Hyperbaric Oxygen Therapy

Blood is made up of three main components: white cells that fight infection, red blood cells that carry oxygen, and plasma, the fluid that carries both kinds of cells throughout the body. Under normal circumstances, only the red blood cells carry oxygen. However, because HBOT forces oxygen into the body under pressure, Oxygen dissolves into all of the body’s fluids, including the plasma, the Lymph, the cerebrospinal fluids surrounding the brain and spinal cord. These fluids can carry the extra oxygen even to areas where circulation is poor or blocked, either by trickling past the blockages or by seeping into the affected area.

This extra oxygen helps in the healing process and enhances the white blood cells’ ability to fight infection. It can promote the development of New Capillaries, the tiny blood vessels that connect arteries to veins. It also helps the body build new connective tissue. In addition, HBOT helps the organs function in a normal manner.

As we age, we can lose vital lung capacity and the ability to effectively obtain adequate Oxygen. Some disease conditions impair oxygen utilization. In addition, with injuries or conditions where there is swelling or edema, this causes pressure within the tissue, which cuts off circulation flow. For years, conventional medicine thought of HBOT only as a treatment for decompression sickness........

However, this is about to change the scope of medicine as never before. The Use of HBOT is becoming increasingly common in general practice as more doctors become acquainted with new applications. Doctors now realize that HBOT has other uses, including the treatment of non-healing wounds, Carbon Monoxide poisoning, various infections, damage caused by radiation treatments, near- drowning, near-hanging, brain and nerve disorders, cardiovascular disorders; and some digestive system disorders.It is important to realize that, in most cases, HBOT is best used when combined with other treatments such as physical therapy and or surgery.

In the USA, the situation stands in marked contrast with many other countries, where HBOT is used for a much wider range of conditions. Multiple Sclerosis patients have banded together in Britain to create their own network of Hyperbaric Chambers. Centers in China treat more than 100,000 patients each year for a multitude of medical conditions.

International Congress of Hyperbaric Medicine (ICHM) has approved indications for which Hyperbaric Oxygen (HBO2) is the primary mode of treatment or an important adjunct to other medical measures.

1. oCarbon Monoxide, Ammonia, Hydrogen Sulphide, Chemical and Petroleum Gas Poisoning.

2. oAccident Head Injuries and other Acute Traumatic Injuries in traffic accidents. 3.o Thermal and Chemical Burns. 4. oAir/Gas Embolism and Nitrogen Narcosis in Scuba Diving Accidents. 5. oDecompression Sickness in Deep Sea Diving (bends). 6. oExceptional Blood Loss Anaemia. 7. oDiabetic Foot and Pressure Ulcers. 8. oNon-Healing Problematic Wounds. 9. oOsteoradionecrosis in Radiotherapy of Cancer Patients. 10. Ostomyelitis (Refractory) in Cancers. 11. Plastic Surgery (Skin Grafts and Flaps). 12. Clostridial Myositis and Myonecrosis (Gas Gangrene) in Post-Surgery Cases. 13. Intracranial Abscess and Encephalitis due to Virus Infections. 14. Strokes and Neurological Disorders. 15. Cerebral Palsy in Near Drowning, near Hanging, Forceps Babies, Autism and Dyslexia. 16. Multiple Sclerosis. 17. Ophthalmological Problems like Retina Detachment or Central Retinal Artery Occlusion (CRAO). 18. Anti-Ageing Treatment. 19. Cosmetic Value Treatment (Michael jackson’s Therapy). 20. Athletic Sports Medicine and Aero Medicine.

Therapeutic effects of Hyperbaric oxygen: Related to the ability of oxygen tension under hyperbaric conditions to:

Promote Cellular proliferation (e.g.restoration of Fibroblast growth and enhancement of osteoclast activity in tissue healing). Reverse Hypoxia in coma patients. Alter Ischemic effects (short supply of oxygen). Influence Vascular Reactivity (e.g. decrease in White Blood Cell adherence to capillary walls). Reduce edema (Swellings). Modulate Nitric Oxide production. Modify Growth Factors (IGF) and Cytokine effect by regulating their levels of receptors in wound healing. Induce changes in membrane proteins affecting on exchanges and gating mechanisms (e.g.preservation of ATP in cell membranes). Accelerate Collagen deposition in tissue healing. Stimulate capillary budding & arborization (Increase capillary proliferation in tissue healing). Accelerate microbial oxidative killing (enhancement of Leucocytes-killing activity in HIV-AIDS patients). Improve selected antibiotics exchange across tissue membranes. Interfere with bacteria propagation by denaturing toxins (suppression of Alpha-toxin production in gas gangrene of problematic wounds). Modulate Immune System Response (stimulation of Superoxide Dismutase (SOD) production). Enchance Oxygen Free Radical Scavengers (decrease Ischemia-Reperfusion injury; termination of Lipid Peroxidation in Carbon Monoxide, Chemical and Petroleum Gas Poisoning).

The History of Mobile-bearing Total Knee Replacement Systems

By Karel J. Hamelynck, MD, PhD

Abstract

The use of a mobile-bearing knee system is routine in modern total knee arthroplasty (TKA). There are indications for use of a mobile-bearing TKA for a growing number of patients. The design, however, was not always well appreciated. Fears of perioperative difficulties and lack of understanding of the design principles limited the acceptance of mobile-bearing technology. Recent evidence has shown that use of mobile-bearing prostheses in TKA has increased, and today, nearly three decades after its introduction, the mobile-bearing design remains relevant and important. The theories behind the design of mobile-bearing prostheses have shown in clinical practice what many already believed to be true: mobile-bearing TKA, when performed correctly, is reliable, and capable of providing substantial benefit for patients.

Mobile-bearing knee replacement systems were designed to prevent mechanical loosening and wear, the two primary shortcomings of knee replacement systems. Studies from the 1960s and 1970s demonstrated good results with conventional fixed-bearing total knee arthroplasty (TKA) systems at 10- to 15-years’ follow-up. However, patients at that time were older and less active than patients are today, and thus there was less demand on implants. Indications for TKA are changing rapidly; today’s patients are more active, and therefore require more durable knee replacement systems, and patients are seeking TKA for knees damaged by excessive weight, accidents, and sports injuries.

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It became clear to early designers of knee prostheses that TKA should entail more than simply replacing cartilage with metal and polyethylene and providing stability through the intrinsic constraint of the components. Clinical follow-up showed that achieving stability through intrinsic constraint was detrimental to fixation and that unnecessary prosthetic constraints should be avoided to minimize the transmission of forces to the bone-prosthesis interface. Free anatomic motion between components was recommended not only to improve function, but to prevent mechanical loosening of components.

These changes had consequences, however; in knee prostheses with fixed bearings, minimal constraint against displacement resulted in small contact areas and high contact stresses. Though minimal torque was transmitted to the fixation interfaces and mechanical loosening was reduced, there was an increased risk of polyethylene articulation damage.

In the 1970s and 1980s, polyethylene wear was not widely recognized as a major cause of aseptic loosening of total knee components. The concept was not well appreciated by orthopedic surgeons, despite the fact that it was demonstrated in laboratory settings and prostheses-retrieval studies. Many designers compromised to produce more conformity between components, while still allowing varus-valgus rotation and some axial rotation. This design concept remains the basis for many knee replacement systems.

Pioneers in Mobile-bearing TKA

Doug Noiles, an engineer with US Surgical Corporation, was probably the first in the United States to recognize that a dual-articulation rotating-platform prosthesis would resolve the kinematic conflict between a low-stress articulation and high bearing conformity. Noiles obtained a patent in 1976 for the Noiles PS Rotating Platform Knee and Revision System, which used metaphyseal sleeves and stems on the tibia and femoral sides. Richard “Dickey” E. Jones began working with Noiles in the mid-1980s, performing many clinical trials on the Noiles PS Rotating Platform knee. This knee system eventually evolved into the P.F.C. Sigma rotating-platform prosthesis (DePuy Orthopaedics, Inc, Warsaw, Ind).

In 1974 Fred Buechel, an orthopedic surgeon, and Michael Pappas, a mechanical engineer, developed the first mobile-bearing joint replacement at Martland Hospital, Newark, NJ, called the “floating-socket” total shoulder, patented in 1975.^1,2

Shortly after, they became influenced by the work of John O’Connor, who presented the work of the Oxford group on mobile meniscal bearings used with intact cruciate ligaments to allow normal knee kinematics after TKA at the annual meeting of the American Association of Orthopaedic Surgeons in Las Vegas, Nev, in February 1977. The Oxford group, headed by John Goodfellow and O’Connor, first described the principle of creating congruent contact at the femorotibial interface while allowing the polyethylene tibial bearing to move relative to the tibial tray.³ The Oxford unicompartmental, meniscal-bearing knee, introduced in 1976, is still used today.

Pappas and Buechel^4,5 were convinced that the mobile-bearing concept could resolve the dilemma facing designers of total knee prostheses at that time: congruency versus constraint. O’Connor viewed the posterior femoral condyle as a circle with the same femorotibial contact in flexion and extension and used a constant radius (the radius of the posterior condyle) for the posterior and distal part of the femoral component. Pappas, using mobile bearings, studied the material properties of polyethylene and calculated the contact area needed to bring the contact stresses well under the maximum allowable level (10 MPa) of ultra high molecular weight polyethylene. Pappas created a femoral component with a large curve in extension, which was the same in both the coronal and sagittal planes. The radius was 50 mm, much larger than the radius of the posterior condyle. The radius created large contact areas between the femoral component and the tibial mobile bearing and also between the femoral component and the patellar component. Pappas, understanding that polyethylene wear would occur during cycles of peak loading of the knee, during heel strike and before toe-off while the knee is extended 5° to 20°, attempted to achieve congruency in extension. To facilitate flexion, the large femoral radius was reduced posteriorly to maintain line contact.^4,5

DePuy Orthopaedics, Inc, entered the “floating socket” industry in 1977 when it received a licensing agreement to manufacture and sell a shoulder prosthesis that implemented the technology. The company later entered the knee prosthesis market in 1979, after Buechel and Pappas presented evidence that the New Jersey Integrated Knee Replacement System improved wear performance of meniscal bearings, compared with conventional fixed bearings, after just 2 years of clinical study.⁶ In 1979, Barry Sorrells became one of the leading advocates of the design and continues, after 30 years, to use the DePuy rotating-platform knee replacement system successfully. Sorrells is one of the original participants in FDA-mandated trials for the New Jersey Knee System and has become an influential advocate of the rotating-platform knee system, also known as the Low Contact Stress (LCS) knee.

Initially, the FDA declined to allow the sale of the New Jersey Knee as a 510K device and required premarket approval and investigational device exemption clinical trials to prove its safety and efficacy. Several prominent surgeons, including Blackwell Sawyer, Emmet Lunceford and Peter Keblish, participated in these trials along with Louis Jordan and P. Fenning. Keblish, interested in the meniscal-bearing and rotating-platform concepts, became known as a speaker and training surgeon both in the United States and abroad. In 1984, the FDA approved the sale of the New Jersey Knee System for cemented knee replacement based primarily on the experience of 23 orthopedic surgeons and results from studies on 918 TKA procedures followed for a minimum of 2 years. The evidence submitted to the FDA included data from Seth Greenwald showing minimal wear and an improvement over fixed bearings in a 10 million-cycle simulation on each of three sets of meniscal bearings. Clinical trials for cementless knee replacement were completed successfully between 1984 and 1991.⁶

Most orthopedic surgeons in the United States at the time did not accept the mobile-bearing concept, because its basis in biomechanics and materials was not well understood. In addition, established knee replacement centers in Boston, New York, and Baltimore, which used fixed-bearing designs, contributed to lack of response. Further, articles about the New Jersey knee were seldom published unless they addressed complications of mobile bearings.^7,8 Such reports fostered misconceptions about complications and surgical difficulty. Gradually, however, some orthopedic surgeons began to use the new design and in 1998, John Insall reported the merits of mobile bearings over fixed bearings to improve long-term wear performance in TKA.⁹

There was more enthusiasm for the LCS total knee system in Europe, as the possibility of good anatomical motion and relief of stresses to the interface appealed to many surgeons. Additionally, the New Jersey knee offered a variety of surgical options. Meniscal bearings allowed the surgeon to retain cruciate ligaments, the natural stabilizers of the knee, whenever they were sufficient and well functioning, and the rotating-platform option allowed sacrificing cruciate ligaments whenever this option seemed more appropriate. In November 1984, the first New Jersey, or LCS, knee, was implanted by a European surgeon in Amsterdam, and in March 1988, the first European congress on mobile-bearing TKA was held, also in Amsterdam. As in the United States, in Europe opinion on the mobile-bearing knee system was divided. Some surgeons, influenced by Sorrells, advocated sacrificing the cruciate ligaments at all times, whereas others, influenced by Keblish, did not consider this sound biomechanical practice. Knee surgeons in Europe were also strongly influenced by Professor Mueller of Bruderholz, Switzerland, whose knowledge of the anatomy and physiology of the knee, and especially the role of the cruciate ligaments, was renowned in TKA.¹⁰ Mueller is credited with the wide use of cruciate-retaining meniscal-bearing prostheses in early LCS TKA.

In the 1990s, there was more general acceptance of the LCS concept, and by 1994, 10 years after the LCS knee prosthesis was introduced in Europe and Asia, 75% of all LCS prostheses were sold abroad, compared with only 25% in the United States.¹¹ Mobile-bearing TKA was still new enough, however, that speakers presenting 10- and 15-year follow-up data on the LCS knee system at major orthopedic meetings were relegated to sessions on “new” products or on “the future of TKA.”

Cruciate-retaining versus Cruciate-sacrifcing TKA

Some surgeons still considered TKA using mobile bearings difficult to perform, and there was some belief that the two articulating surfaces would lead to twice as much wear. Proponents of fixed-bearing knees published studies with long-term follow up showing more durability than mobile-bearing knees, data that had not yet been shown except by its designer.^12-15

There was considerable debate among advocates of LCS knee replacement on whether to retain or sacrifice the cruciate ligaments in TKA. With rare exception,¹⁶ both surgical approaches produced good clinical results.^6,17-22 In nearly all cases, less favorable results could be attributed to insufficient surgery and improper indication, such as cruciate ligament retention in the elderly, rather than to defective design of the prosthesis. Very few surgeons attempted to retain both cruciate ligaments; it was considered too difficult by most surgeons, despite reports of good clinical results.²⁴ Retaining the posterior cruciate ligament (PCL) was preferred in young and active patients, because of its important mechanical and proprioceptive qualities. According to Mueller,¹⁰ it was unclear whether the PCL (the lateral collateral ligament of the medial compartment of the knee and an important stabilizing force against varus-valgus rotations)²⁵ could also help provide stability in the anteroposterior direction and in femoral roll-back during flexion of the knee in the absence of the anterior cruciate ligament. Some PCL-retaining knees proved to be unstable in the anteroposterior direction, sometimes even demonstrating a negative roll-back movement, with negative consequences for the meniscal bearings, including breakage, dislocation, and wear.²⁶

Some surgeons used the rotating-platform LCS knee in all patients, whereas others limited its use to elderly patients with insufficient cruciate ligaments. Results were generally very good, with minimal loosening of components and virtually no wear-induced osteolysis.^21,27 In the United States in the mid-1990s, 75% of LCS knees implanted were of the cruciate-retaining, meniscal-bearing type, and 25% were of the rotating-platform type, compared with 63% and 37%, respectively, outside the United States.¹¹

In 2002, Hamelynck et al²⁸ published a multicenter outcome study comparing results in cruciate-retaining TKA versus cruciate-sacrificing TKA. Twenty-seven surgeons from the United States, Europe, Asia, and South Africa submitted results from procedures performed on 4743 knees: 324 with a bicruciate-retaining, meniscal-bearing tibial component, 2165 with a PCL-retaining, meniscal-bearing tibial component, and 2254 with a rotating-platform tibial component. All patients were followed a minimum of 5 years. The study confirmed results of the LCS total knee system as reported in the literature, that fixation of tibial components with a central tapered cone was reliable. Failure of fixation occurred in 1.1% of the cementless PCL-retaining meniscal-bearing rotating-platform TKAs; 0.7% of the cemented PCL-retaining meniscal-bearing TKAs; and 0.5% of the cemented rotating-platform TKAs. Loosening of femoral and patellar components did not occur. No metal components were revised because of wear-induced osteolysis. Polyethylene wear was reported in some of the older rotating platforms and meniscal bearings, primarily associated with gamma-irradiation in air sterilization. Bearing problems occurred in 1.8% of all patients: 2.2% in bicruciate-retaining meniscal-bearing tibial component knees and 3.0% in PCL-retaining meniscal-bearing tibial component knees; the rotating-platform bearing caused problems in only 0.5% of the cases.

Meniscal-bearing complications such as dislocation and subluxation were found to result from surgical technique issues, including insufficient ligament balancing in flexion, improper positioning of the tibial or femoral component, and retention of an insufficient PCL.

Use of the rotating-platform knee design increased in the United States; the rotating-platform knee was used in approximately 25% of all TKAs in 1994 and in 88% in 1998. Data from Europe and Asia show that a rotating-platform knee was used in 37% of TKAs in 1994 and 72% in 1998.¹¹ The use of meniscal bearings in LCS TKAs in Europe and Asia declined after DePuy launched the LCS AP-glide, a posterior cruciate-retaining tibial component with a gliding polyethylene platform. Movement in the new design was controlled by a guide arm rather than a central cone. Today meniscal-bearing knees are use in less than 4% of LCS knee systems.¹¹

Retrieval studies also demonstrated the superiority of the mobile-bearing design compared with the fixed-bearing designs. Collier et al²⁹ observed important differences in wear in mobile-bearing and fixed-bearing designs in a study comparing 206 mobile-bearing knee devices (144 meniscal-bearing devices and 62 rotating-platform devices) with 619 fixed-bearing knee devices. In the fixed-bearing knees, fatigue mechanisms of cracking and delamination had been dominant. Mobile-bearing knees were found to have a significantly lower incidence of delamination than fixed-bearing knees, despite these bearings all having been sterilized with gamma irradiation in an air environment and then stored in air. It had become clear from earlier research that gamma radiation and air storage resulted in degradative oxidation of the polyethylene.^30-33 The superior results among mobile-bearing knees in the study, however, suggested that a design factor, namely congruity, which affords a large contact area to reduce contact stress, accounted for this apparent discrepancy.

Collier et al²⁹ also reported a lower incidence of significant abrasion in mobile-bearing knees, an important factor given the advent of sterilization methods that limit bearing oxidation and its accompanying fatigue mechanisms. Advances in sterilization methods, specifically the use of ethylene oxide instead of gamma irradiation, indicated that abrasion would likely become the wear mode of greatest concern in knee prostheses. According to Collier, the concern that mobile-bearing knees have a dual articulation, and therefore the potential for increased debris generation, appears to be mitigated by the observation that even fixed bearings fret against their metal counterfaces and produce backside wear debris. The wear data indicated very low wear rates for the dual-articulation mobile-bearing system. The constant observation that machining lines remained visible on the mobile bearing back surface was interesting. Backside surface wear did not result in appreciable removal of material, even in bearings of longest duration.

The importance of reducing wear by increasing the contact areas has been confirmed.^23,34-36 Recently, McEwen et al³⁷ demonstrated that LCS mobile-bearing rotating-platform knee designs result in a significantly lower mean volumetric wear rate of polyethylene than fixed-bearing knee designs, especially when subjected to high internal-external rotational kinematic inputs. McEwen postulated that the reason for this reduced wear rate is that rotating-platform, mobile-bearing designs decouple the motion between the femoral insert and tibial tray insert. As a result, most of the rotation occurs at the distal tibial articulation surface, which generates unidirectional rotation motion. Unidirectional motion is known to produce low wear.³⁸ In other words, backside wear is minimal, and the proximal femoral articulating interface also generates very low axial rotation. Therefore, at the femoral insert articulation, motion is mostly unidirectional and lower wear on the polyethylene is produced.

The mobility characteristics and gait patterns of patients with mobile bearings have also been studied extensively,^26,28,39-47 confirming the superiority of mobile-bearing TKA over fixed-bearing TKA in long-term follow-up.²⁷

Summary

Mobile-bearing systems were designed to prevent mechanical loosening and wear, the two primary complications of knee replacement. Today, after more than 25 years in clinical use, and with overwhelming evidence from clinical experience, laboratory experiments and retrieval analysis, the mobile-bearing concept underlying rotating-platform knee systems has proven to be reliable. The LCS rotating-platform knee, unchanged in almost 30 years, remains a relevant and important design concept.

It is important to note the important design features of mobile-bearing knees. Polyethylene components need to be mobile in a manner that movement is restricted by soft tissues rather than by intrinsic constraint, and bearings must provide sufficient stability to compensate for the absence of the cruciate ligaments. Also, femorotibial contact areas should be large to prevent wear, especially considering condylar lift-off during gait. Finally, movement proximally and distally of the polyethylene bearing should be unidirectional rather than controlled by metal stops, also to prevent wear.

There are many mobile-bearing knee prostheses today. The original patent for mobile-bearing rotating-platform knee systems owned by DePuy expired in 1997, allowing manufacturers to develop their own mobile-bearing prosthesis. Although most rotating-platform knees look alike, there are major differences in design, and classification is needed as proposed by Briard⁴⁶ and Heim and Greenwald.¹⁷ In some rotating-platform designs, the femorotibial contact area is very large, and in other designs, the contact area is rather small. Some designs incorporate unidirectional movement at the distal surface between the polyethylene bearing and tibial tray, whereas others utilize multidirectional gliding at the distal surface.

There also are significant differences in how bearing movement is controlled. Some mobile-bearing knee systems incorporate a certain amount of constraint. In others, bearing movement is controlled by metal cylinders, slots, or stops that may be effective in controlling bearing movement, but may produce suboptimal kinematics and stress on the polyethylene leading to damage and wear. Because of these design differences, long-term follow-up studies should be undertaken to determine variations in results.

References

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2. Buechel FF, Pappas MJ, De Palma AF. “Floating-socket” total shoulder replacement: anatomical, biomechanical and surgical rationale. J Biomed Mater Res. 1978; 1: 89-114.
3. Goodfellow JW, O’Connor J. The mechanics of the knee and prosthesis design. J Bone Joint Surg Br. 1979; 60: 358-368.
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25. Grood ES, Noyes FR, Butler DL, Suntay WJ. Ligamentous and capsular restraints preventing straight medial and lateral laxity in intact human cadaver knees. J Bone Joint Surg Am. 1981; 63:1257-1269.
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34. Bartel DL, Bicknell VL, Wright TM. The effect of conformity, thickness and material on stresses in ultra-high molecular weight polyethylene components for total joint replacement. J Bone Joint Surg Am. 1986; 68:1041-1051.
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36. McEwen HMJ, Barnett PI, Bell CJ, et al. The influence of design, materials and kinematics on the in vitro wear of total knee replacements. J Biomech. 2005; 38:357-365.
37. McEwen HM, Goldsmith AAJ, Auger DD, et al. Wear of fixed bearing and rotating platform mobile bearing knees subjected to high internal and external tibial rotation kinematics. J Mater Sci Mater Med. 2001; 12:1049-1052.
38. Pooley CM, Tabor D. Friction and molecular structure: the behaviour of some thermoplastics. Proc R Soc Lond A. 1972; 329:251-274.
39. Greenwald AS. Stability characteristics of the tibial-femoral and patella-femoral articulations. In: Hamelynck KJ, Stiehl JB, eds. LCS Mobile Bearing Knee Arthroplasty: a 25 Years Worldwide Review. Heidelberg, Germany; Springer; 2002:53-56.
40. Morra EA, Postak PD, Greenwald AS. The effects of articular geometry on delamination and pitting of UHMWPE tibial inserts: a finite element study. Paper presented at: 64th Annual Meeting of the American Academy of Orthopedic Surgeons; February 13-17, 1997; San Francisco, Calif.
41. Morra EA, Postak PD, Greenwald AS. The influence of mobile bearing knee geometry on the wear of UHMWPE tibial inserts: a finite element study. Paper presented at: 65th Annual Meeting of the American Academy of Orthopedic Surgeons; March 19-23, 1998; New Orleans, La.
42. Haas BD, Komistek RD, Stiehl JB et al. Kinematic comparison of posterior cruciate sacrifice versus substitution in a mobile bearing total knee arthroplasty. J Arthroplasty. 2002;17:685-692.
43. Schlepkow P. Three-dimensional kinematics of total knee replacement systems. Arch Orthop Trauma Surg. 1992; 111:204-209.
44. Stiehl JB, Dennis DA, Komistek RD, Keblish PA. Kinematic analysis of a mobile bearing total knee arthroplasty. Clin Orthop Relat Res. 1997; 345:60-65.
45. Stiehl JB, Komistek RD, Haas BR, Dennis DA. Frontal plane kinematics after mobile bearing total knee arthroplasty. Clin Orthop Relat Res. 2001; 392:56-61.
46. Stiehl JB, Komistek RD, Dennis DA. In vivo kinematic comparison of posterior cruciate retention or sacrifice with a mobile bearing total knee arthroplasty. Am J Knee Surg. 2002; 13:13-18.
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Author

Dr Hamelynck is a former clinical professor of orthopaedic surgery at Slotervaart Hospital, Amsterdam, Netherlands.

Trends in Total Knee Arthroplasty

By Douglas A. Dennis, MD

Abstract

The success of total knee arthroplasty (TKA) over the past two decades of use has resulted in the implantation of TKA into younger patients who have increased functional requirements and demand increased implant longevity. Improved functional performance requires enhanced range of motion, increased motor performance, and creation of kinematic patterns that more closely resemble the normal knee. Increased longevity necessitates more durable implant fixation, improvements in bearing materials, and lower polyethylene stresses. Considerations to reduce polyethylene wear include increased cross-linking, improved femoral component surface finish, better modular tibial locking mechanisms, and the use of mobile-bearing TKA designs that allow increased implant conformity and reduced contact stresses without increasing loads transmitted to the fixation interface.

Reports of device failure in the early years of total knee arthroplasty (TKA) were frequently secondary to aseptic loosening and were often associated with malalignment, instability, or use of implants with excessive prosthetic constraint. With improvements in surgical instrumentation and operative techniques (ie, improved alignment and ligamentous balancing), and due to the use of lower conformity prosthetic devices, loosening rates have been minimized. Low conformity TKA designs, however, resulted in a reduction of polyethylene contact area, and premature polyethylene wear and periprosthetic osteolysis became a prominent cause of TKA failure.¹

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There has been excellent 10- to 15-year outcomes of primary TKA. Future TKA designs, therefore, should improve functional performance and reduce articular bearing surface wear, and maintain the excellent long-term fixation typically obtained in properly aligned and balanced TKAs currently in use.

Improving Functional Performance

Figure 1: Diagram demonstrating the modification of the J curve of the femoral component of some “high-flexion” TKA designs.

Enhancing range of motion (ROM) and muscle function are crucial to improving functional performance of TKA. Replication of the normal knee kinematic pattern is critical to maximize knee flexion and physical function. In vivo fluoroscopic studies of normal knee kinematics demonstrate that posterior femoral roll-back of the lateral femoral condyle, averaging 14.1 mm, routinely occurs during deep flexion. Deep flexion is also associated with substantial axial rotation, averaging 16.8°.² Additional similar studies of patients implanted with TKA show significant reductions in posterior femoral roll-back and axial rotation, as well as the presence of paradoxical anterior femoral translation during deep flexion.^3,4 These kinematic differences from the normal knee likely account, at least in part, for the reduction in knee flexion and reduced motor function typically observed following TKA when compared with the normal knee. Future designs of TKA should focus on providing reproducible roll-back and increased axial rotation.

Recent design efforts to improve knee flexion have been incorporated into high-flexion TKA designs.^5-7 These high-flexion devices allow for posterior cruciate ligament substitution, which enhances posterior femoral roll-back, and bearing mobility, which permits increased amounts of axial rotation without creating excessive rotational polyethylene stresses. Many of these newer designs have also reduced the radius of curvature (“J” curve) of the posterior femoral condyles, both to increase the posterior femoral translation distance and reduce polyethylene stresses in deep flexion (Figure 1).

Reducing Polyethelene Wear

Numerous design improvements have been introduced to reduce polyethylene wear. Some focus on improving the bearing materials, including increasing the cross-linking of polyethylene and improving the surface finish of the femoral component. Multiple knee simulator analyses demonstrate marked reductions in adhesive and abrasive wear when comparing highly crosslinked tibial insert specimens with those manufactured with standard polyethylene.^8-10 Longer in vivo clinical evaluations are needed to assess the value of increased cross-linking of polyethylene in TKA. Computer-directed, precision-grind finishing of femoral components is shown to increase polyethylene contact area by 29%.¹¹ A knee simulator analysis of femoral components manufactured with oxidized zirconium show substantial reductions in polyethylene wear when compared with components manufactured from cobalt-chromium alloys.¹²

Figure 2: Contact area and stress analysis demonstrating high polyethylene contact areas (mm2) and low peak stresses (MPa) of three mobile bearing TKA designs.

Accelerated wear from micromotion and backside wear of modular tibial components is associated with premature failure and periprosthetic osteolysis.¹³ Improvements in modular locking mechanisms and the polishing of modular cobalt-chromium tibial trays were introduced to reduce this mechanism of polyethylene wear.¹⁴ Additionally, use of all-polyethylene or other designs of monoblock tibial components are shown to minimize polyethylene wear.¹⁵

Use of implant designs with increased implant conformity reduces contact stresses and the potential for polyethylene wear but can increase wear and fixation stresses in fixed-bearing TKA if conformity is excessive. Mobile-bearing TKA allows increased implant conformity and contact area without dramatically increasing stresses transmitted to the polyethylene material or fixation interface.

Figure 3: Histogram of a high kinematic knee simulator analysis demonstrating polyethylene wear per million cycles of a fixed-bearing versus rotating-platform TKA with identical femoral component geometry.

By increasing sagittal plane conformity in mobile-bearing TKA, in vivo fluoroscopic analyses demonstrate improved control of anteroposterior translation with reduced paradoxical anterior femoral translation, particularly when tested during gait.⁴ The increased coronal plane conformity typically present in mobile-bearing TKA increases the contact area and lessens the increased contact stresses, which are present if femoral condylar lift-off occurs.^16,17 The increased conformity and subsequent reduction in contact stresses in mobile-bearing designs are shown to substantially lower polyethylene stresses in numerous evaluations.^17,18-21 Greenwald demonstrated contact areas of mobile-bearing TKA during gait range from approximately 400 mm² to 800 mm², which keeps contact stresses at 14 MPa or less (Figure 2).²² The contact areas are substantially greater than is typically observed in most fixed-bearing TKA designs (200 mm² to 250 mm²). Lastly, the advantage of increased contact area is reflected in knee simulator wear studies of fixed-versus mobile-bearing TKA. McEwen et al¹⁹ noted over a four-fold reduction in wear in knee simulator testing of a rotating-platform TKA versus a fixed-bearing design with identical femoral component geometry (Figure 3).

To avoid high polyethylene stresses typically observed with highly conforming, fixed-bearing TKA, rotational bearing mobility must be present and has been documented to occur under in vivo conditions.^23,24 The majority of axial rotation observed in these in vivo studies occurred at the polyethylene bearing-tibial tray interface, with the polyethylene bearing typically following the rotation of the femoral component.

Rotation of the rotating-platform polyethylene insert with the femoral component reduces stresses transmitted to the fixation interface and creates the potential for self-alignment of the polyethylene bearing with the femoral component. Rotational post impingement in posterior cruciate-substituting TKA systems can be reduced in rotating-platform designs due to post rotation with the femoral component intercondylar box rather than by attempts to rotate against it. The self-aligning behavior of the polyethylene bearing with the femoral component is shown to maintain large, centrally located surface contact areas at the femorotibial articulation during flexion and extension movements and during axial rotation of the knee. These advantages are typically more difficult to achieve with fixed-bearing TKA designs.²¹ An additional advantage of the self-aligning feature of rotating-platform TKA systems is the potential facilitation of central patellar tracking.²⁹ In a fixed-bearing TKA, if substantial internal rotation of the tibial component relative to the femoral component is present, the tibial tubercle is lateralized, enhancing the risk of patellar subluxation. A rotating-platform design, because of bearing rotation, permits greater self-correction of component rotational malalignment and allows better centralization of the extensor mechanism.

An in vivo fluoroscopic evaluation of over 1000 TKAs involving 33 different fixed and mobile-bearing TKA designs demonstrated that most patients with TKAs experience less than 10° of axial rotation with normal postoperative activities.³ However, in this large multi-center analysis, a number of subjects experienced axial rotational magnitudes greater than 20°, which is beyond the rotational boundaries of most fixed-bearing TKA designs. Greater axial rotation is an additional advantage for rotating-platform TKA designs, which can accommodate a wider range of axial rotation without creation of excessive polyethylene stresses.

Other Advances

Other future improvements to potentially enhance TKA include the introduction of newer, cementless ingrowth materials such as trabecular metal, use of less invasive operative techniques, and the use of computer-assisted navigation. Computer-assisted navigation is shown to reduce component alignment errors and has the potential to increase the precision of soft-tissue balancing.^26,27

References

1. Sharkey PF, Hozack WJ, Rothman RH, et al. Why are total knee arthroplasties failing today? Clin Orthop Relat Res. 2002; 404:7-13.
2. Komistek RD, Dennis DA, Mahfouz M. In vivo fluoroscopic analysis of the normal human knee. Clin Orthop Relat Res. 2003; 410:69-81.
3. Dennis DA, Komistek RD, Mahfouz MR, et al. A multicenter analysis of axial femorotibial rotation after total knee arthroplasty. Clin Orthop Relat Res. 2004; 428:180-189.
4. Dennis DA, Komistek RD, Mahfouz MR, et al. Multicenter determination of in vivo kinematics after total knee arthroplasty. Clin Orthop Relat Res. 2003; 416:37-57.
5. Ranawat AS, Gupta SK, Ranawat CS. The P.F.C. Sigma RP-F total knee arthroplasty: designed for improved performance. Orthopedics. 2006; 29(suppl 1):S29-S30.
6. Gupta SK, Ranawat AS, Shah V, et al. The P.F.C. Sigma RP-F TKA designed for improved performance: a matched-pair study. Orthopedics. 2006; 29(suppl 1):S50-S53.
7. Jones RE. High-flexion, rotating-platform knees: rationale, design, and patient selection. Orthopedics. 2006; 29(suppl 1):S78-S81.
8. Muratoglu OK, Bragdon CR, Jasty M, et al. Knee-simulator testing of conventional and cross-linked polyethylene tibial inserts. J Arthroplasty. 2004; 19:887-897.
9. Schmidig G, Essner A, Wang A. Knee simulator wear of cross-linked UHMWPE. Presented at: the Annual Meeting of the Orthopaedic Research Society, Orlando, Fla, 2000.
10. Wang A, Polineni VK, Essner A, et al. Effect of radiation dosage on the wear of stabilized UHMWPE evaluated by hip and knee joint simulators. Presented at the Annual Meeting of the Society for Biomaterials, New Orleans, La, 2000.
11. Heim CS, Postak PD, Greenwald AS. Factors Influencing the longevity of UHMWPE tibial components. Instr Course Lect. 1996; 45:303-312.
12. Spector BM, Ries MD, Bourne RB, et al. Wear performance of ultra-high molecular weight polyethylene on oxidized zirconium total knee femoral components. J Bone Joint Surg Am. 2001; 83 (suppl 2 pt 2):80-86.
13. Rao AR, Engh GA, Collier MB, et al. Tibial interface wear in retrieved total knee components and correlations with modular insert motion. J Bone Joint Surg Am. 2002; 84:1849-55.
14. Collier MB, Engh CA Jr, McAuley JP, et al. Osteolysis after total knee arthroplasty: influence of tibial baseplate surface finish and sterilization of polyethylene insert. Findings at five to ten years postoperatively. J Bone Joint Surg Am. 2005; 87:2702-8.
15. Ranawat AS, Mohnaty SS, Goldsmith SE, et al. Experience with an all-polyethylene total knee arthroplasty in younger, active patients with follow-up from 2 to 11 years. J Arthroplasty. 2005; 20(7 suppl 3):7-11.
16. D’Lima DD, Chen PC, Colwell CW Jr. Polyethylene contact stress, articular congruity, and knee alignment. Clin Orthop Relat Res. 2001; 392:232-238.
17. Dennis DA, Komistek RD, Walker SA, et al. Femoral condylar liftoff in vivo in total knee arthroplasty. J Bone Joint Surg Br. 2001; 83:33-39.
18. Bartel DL, Bicknell VL, Ithaca MS, et al. The effect of conformity, thickness and material on stresses in ultra-high molecular weight components for total joint replacement. J Bone Joint Surg Am. 1986; 68:1041-1051.
19. McEwen HMJ, Barnett PI, Bell CJ, et al. The influence of design, materials and kinematics on the in vitro wear of total knee replacements. J Biomech. 2005; 38:357-365.
20. Otto JK, Callaghan JJ, Brown TD. Gait cycle finite element comparison of rotating-platform total knee designs. Clin Orthop Relat Res. 2003; 410:181-188.
21. Stukenborg-Coleman C, Ostermeier S, Hurschler C, et al. Tibiofemoral contact stress after total knee arthroplasty: comparison of fixed and mobile-bearing inlay designs. Acta Orthop Scand. 2002; 73:638-646.
22. Greenwald AS, Heim CS. Mobile-bearing knee systems: ultra-high molecular weight polyethylene wear and design issues. Pellegrini V, ed. Rosemont, Ill: Instructional Course Lectures, American Academy of Orthopaedic Surgeons, 2005; 43:195-206.
23. Dennis DA, Komistek RD, Mahfouz MR, et al. Mobile-bearing total knee arthroplasty: do the polyethylene bearings rotate? Clin Orthop Relat Res. 2005; 440:88-95.
24. Komistek RD, Dennis DA, Mahfouz MR, et al. In vivo polyethylene bearing mobility is maintained in posterior stabilized total knee arthroplasty. Clin Orthop Relat Res. 2004; 428: 207-213.
25. Callaghan JJ, Squire MW, Goetz DD, et al. Cemented rotating-platform total knee replacement: a nine to twelve-year follow-up study. J Bone Joint Surg Am. 2000; 82:705-711.
26. Bolognesi M, Hofmann A. Computer navigation versus standard instrumentation for TKA: a single-surgeon experience. Clin Orthop Relat Res. 2005; 440:162-169.
27. Haaker RG, Stockheim M, Kamp M, et al. Computer-assisted navigation increases precision of component placement in total knee arthroplasty. Clin Orthop Relat Res. 2005; 433:152-159.

Author

Dr Dennis is from the Department of Biomedical Engineering, University of Tennessee, Knoxville, Tenn, Oak Ridge National Laboratory/University of Tennessee Center for Musculoskeletal Research, Knoxville, Tenn, and Rocky Mountain Musculoskeletal Research Laboratory, Denver, Colo.

Low Contact Stress (LCS) Complete Knee System in Revision Surgery

By Craig N. Lippe, MD; Lawrence S. Crossett, MD

Abstract

Revision total knee arthroplasty (TKA) should offer the same benefits to patients as primary TKA. As in primary TKA, a main objective of revision TKA is to reduce pain and restore functional range of motion. There are several potential causes of total knee failure, but the principles of repairing each of them is similar. The long-term success of the low contact stress knee system in primary TKA is well established, and clinical evidence for revision TKA with the low contact stress knee is promising.

Most patients who undergo primary total knee arthroplasty (TKA) achieve significant pain relief and restoration of function.¹ However, a small percentage of patients will have continued pain, instability, or stiffness for a variety of reasons. The causes of total knee failures include component loosening, infection, osteolysis, instability, patellofemoral problems, polyethylene wear, lack of motion, and malposition of the components.² Revision knee surgery presents unique problems to the surgeon including bone loss and soft tissue deficiencies that must be addressed at surgery.

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There is the potential for significant patient morbidity, including extensor mechanism disruption,³ wound healing problems,⁴ and an increased risk of infection.⁵ Revision knee surgery also presents a considerable health care burden in terms of cost and use of resources, especially in large referral centers.⁶ Ideally, any revision should be unnecessary. However, once presented with a failed implant, the surgeon must have a revision system available that has the options and flexibility to handle issues of bony loss and soft-tissue deficiencies and one that provides the patient with a stable, well-fixed functional knee.

Total Knee Revision Concepts

TKA revision surgery requires a thorough understanding of normal and pathologic anatomy. Implant failure is frequently accompanied by varying degrees of bone and soft-tissue loss. Additional difficulties include scarring, flexion-extension gap imbalance and changes in the anatomic joint line. The basic principle of revision arthroplasty involves creating a kinematically stable knee that is well fixed and well aligned. This involves the management of the residual bone and soft-tissue loss. Any revision knee system must adequately address these defects with varying levels of prosthetic constraint, component augmentation, diaphyseal stems, and metaphyseal sleeves. An implant that combines this interoperative flexibility with the benefits of a rotating platform should optimize patient outcomes. If the knee surgeon accepts the concept of low contact stress arthroplasty, it is only logical that these principles should be applied in clinically compromised patients.

Benefits of the Rotating Platform

The clinical history of the low contact stress knee is well documented,^7,8 and the use of a rotating platform in revision knee surgery draws on the advantages of rotation (Figure 1). Unidirectional motion reduces polyethylene wear and subsequent lysis. Rotation reduces the loosening forces at the bone/prosthetic interface, allowing for stable long-term fixation. The congruency of the bearing gives the patient excellent stability in gait. These features, in combination with a revision system that allows the surgeon to address the deficiencies encountered in the knee surgery revision setting, should provide an optimal knee revision system.

Figure 1: The LCS Complete Revision Knee System allows rotation between the polyethylene insert and tibial tray.	Figure 2: Excessive polyethylene post wear.

McEwen et al⁹, Mars et al,¹⁰ and Wang et al¹¹ have documented the benefit of unidirectional motion versus multidirectional motion in the reduction of volumetric polyethylene wear. The unique design of the rotating-platform mobile-bearing knee translates complex input motions into more unidirectional motion, resulting in a reduced wear rate due to decreased shear in the polyethylene. In contrast, the rotation of a fixed-bearing knee occurs entirely at the femoral-insert articulation, resulting in multidirectional motion and increased shear forces, which produces greater polyethylene wear. The unidirectional motion encountered with the rotating-platform mobile-bearing knee reduces the potential for long-term osteolysis by minimizing volumetric polyethylene wear.

Figure 3: The LCS Complete Revision Knee System.

Another problem that rotation potentially addresses is that of polyethylene post wear encountered with posterior-stabilized or varus- or valgus-constrained, fixed-bearing knees. Femoral rotation is resisted by the post in a fixed-bearing knee, resulting in high stresses and wear (Figure 2). The rotating-platform prosthesis allows the post to rotate with the femoral component.

Stable fixation of prosthetic components is extremely important to the long-term success of both primary and revision knee arthroplasty. Many factors contribute to the ultimate result. The surgical technique and the quality of bone are arguably the most important factors. The biomechanical characteristics of the prosthesis and the activity of the patients are the next most important factors in determining outcome. The geometry of any prosthetic design can and will restrict movement. Any force caused by motion in the knee that is restricted by the prosthesis is transmitted to the bone/prosthesis and tibial polyethylene/tibial tray interfaces. The greater the intrinsic constraint, the greater the force conducted to these interfaces. Thus, there is a greater potential for loosening of the prosthesis and backside wear.¹² A rotating-platform prosthetic design uncouples these forces, minimizing the rotational and shear forces that are conducted to the bone/prosthetic interface, and allows for the compressive loading of bone.¹³

LCS Complete Knee System in Revision

The LCS Complete Knee System for revision (DePuy Orthopaedics, Warsaw, Ind) was designed to bring the kinematic advantages of the LCS Complete Primary system to revision surgery (Figure 3). The congruency of the bearing gives excellent stability in gait. The mobile bearing allows rotation to occur at the polyethylene bearing/tibial component interface, lessening the stress at the prosthetic interface, which is often compromised in the revision setting. In addition, the unidirectional wear pattern of the rotating platform significantly reduces volumetric polyethylene wear and subsequent lysis or polyethylene failure. Superior patellar kinematics aid in postoperative patella tracking. The addition of diaphyseal stems, tibial and femoral metaphyseal sleeves, tibial and femoral augmentation, and varying degrees of constraint (Figure 4) offers the surgeon intraoperative flexibility when managing the diverse levels of bony and soft-tissue loses encountered in revision TKA.

The Mobile-bearing Tibial Revision Tray

A tibial revision system must allow the surgeon the options of adjunctive stem fixation, methods to manage bone loss, and various levels of prosthetic constraint. The mobile-bearing tibial revision tray (Figure 5) serves as a stable and versatile foundation in the revision knee setting by offering abundant intraoperative options and a platform to compensate for severe bone loss and soft-tissue deficiencies.

The mobile-bearing tibial revision knee tray encompasses a wide array of options to assist the revision knee surgeon when handling bony and soft-tissue deficiencies. There are multiple sizes of tibial components to allow for proximal tibial coverage. Stepped metaphyseal sleeves allow for the filling of bony defects and superior metaphyseal compressive loading. Trial sleeves are sequentially broached until bony defects are overcome and solid fixation in the metaphyseal bone is achieved. Tibial augmentations are also available to manage uncontained bony defects, allowing the surgeon to achieve a stable platform on good bone for excellent fixation. Cemented or uncemented tibial diaphyseal stems are available in various lengths and diameters, offering the knee surgeon flexibility in achieving a stable construct. The mobile-bearing tibial revision tray allows the revision surgeon to accomplish the goals of filling substantial bony defects, restoring the joint line, and providing a strong foundation for solid fixation with compressive loading of bone.

Figure 4: A variety of augments, metaphyseal sleeves, diaphyseal stems, and polyethylene inserts are available with the LCS Complete Revision Knee System.

An additional goal of revision surgery is to use only the constraint necessary when dealing with soft-tissue deficiencies. The mobile-bearing tibial revision knee tray accepts a wide range of bearings with increasing levels of constraint to cope with soft-tissue deficiencies. The tibial platform may be used with rotating-platform inserts from the LCS Complete (a simple rotating-platform insert), the LCS Complete Rotating Platform posterior-stabilized insert, or varus- or valgus-constrained inserts. All of these inserts share the same articulation and central stem geometry with the clinically successful LCS knee. In addition, the revision surgeon has the option of using inserts from the P.F.C. Sigma RP and Sigma TC3 sets in combination with the P.F.C. Sigma revision femoral component. Finally, the revision surgeon has the option of using a rotating platform-hinged insert from the Limb Preservation System, which is compatible with the S-ROM Noiles Rotating Hinge femoral component and the Limb Preservation System distal femoral component. The knee revision surgeon now has the intraoperative ability to manage a wide range of soft-tissue deficiencies using a single tibial platform.

LCS Complete Revision Femoral Component

A revision femoral prosthetic system must allow the restoration of anatomic alignment and functional stability, stable fixation of the revision implants and reestablishment of the joint line. In addition, it is of paramount importance, especially when using a mobile-bearing revision insert, for the revision surgeon to be able to adequately control the flexion gap. The femoral component in the LCS Complete Knee System for revision (Figure 6) accepts bearings of varying constraint and offers the surgeon the options of adjunctive stems, metaphyseal sleeve fixation, and distal and posterior augmentation.

Figure 5: The M.B.T. Revision Tray with available augmentation.	Figure 6: The LCS Complete Revision Femoral Component with available augmentation.

The femoral component in the LCS Complete Knee System for revision is available in multiple sizes and allows the surgeon to match the femur size to the tibia. Femoral augments are available to fill bony defects, re-establish the joint line, and balance the flexion-extension gaps. Distal femoral augments are available in 5-, 10-, and 15-mm sizes, and posterior femoral augments are available in 5- and 10-mm thicknesses. Femoral metaphyseal sleeves are available to fill contained bony defects and provide a stable base for solid fixation of the implant in good bone. Finally, both cemented and uncemented stems are available in various sizes to achieve stable fixation.

Surgical Technique

Preoperative Planning

Revision total knee arthroplasty begins with thorough clinical and radiography evaluations. Physical evaluation includes examining the soft tissues and noting previous incisions. Range of motion, motor strength, condition of all neurovascular structures, ligamentous stability and integrity of the extensor mechanism are evaluated.

Radiographic evaluation includes biplanar views of the knees and tangential views of the patella to assess the present implant and evaluate bone stock. Full-length radiographs are useful in assessing overall alignment. Templates are then used to establish replacement implant sizes and the alignment of bone cuts to indicate augmentation of bony defects and to confirm the anatomic joint line.

Exposure

Exposure is the key to revision knee surgery. A few minutes spent at the beginning of the surgery to get good exposure will save the surgeon from struggling throughout the remainder of the procedure. The concepts of “minimally invasive” or “mini-incision” do not apply in the revision setting. Adequate exposure aids in the removal of failed components, debridement, and assessment of bony defects and in the eventual reimplantation of revision components.

When possible, the scar from the primary procedure is followed. Where parallel incisions are present, the more lateral is usually preferred, because the blood supply to the extensor surface is medially dominant. Where a transverse patellectomy scar is present, the incision should transect it at 90°. Where there are multiple incision scars or substantial cutaneous damage (patients with burns or skin grafts, etc), one may decide to consult a plastic surgeon before surgery to design the incision, determine the efficacy of preoperative soft tissue expansion, and plan for appropriate soft-tissue coverage at closure.

Where patellar mobilization difficulties persist, a quadriceps snip, a proximal inverted quadriceps incision (modified V-Y), or a tibial-tubercle osteotomy may be indicated.¹⁴ Appropriate ligamentous release is performed based on preoperative and intraoperative evaluation. Fibrous adhesions are released to reestablish the suprapatellar pouch and medial and lateral gutters. In many revision patients, the posterior cruciate ligament will be absent or nonfunctional; any residual portion is excised. Intra-operative cultures are obtained at every revision.

Extraction of Implants

Care is taken to preserve as much bone as possible. To this end, a selection of tools is assembled, including thin osteotomes, an oscillating saw, a Gigli saw, a high-speed burr, and various extraction devices, although in many cases only the osteotome is required.¹⁵ The bone/cement or bone/prosthesis interface is carefully disrupted before extraction is attempted. The implanted components are disengaged and extracted as gently as possible to avoid fracture and unnecessary sacrifice of bone stock. When the entire prosthesis is to be replaced, it is advantageous to remove the femoral component first, because this will enhance access to the proximal tibia. All residual methyl methacrylate is cleared with chisels or power tools.

Tibial Preparation

For purposes of alignment, we recommend that the proximal tibial be prepared with reference to the position of an intramedullary (IM) rod. The knee is placed in maximum flexion with the patella laterally displaced and the tibia anteriorly subluxed (Figure 7). The location of the medullary canal is approximated, and the medullary canal is sequentially reamed with progressively larger reamers until firm endosteal engagement is established.

If the revision surgeon opts not to use a tibial metaphyseal sleeve, the proximal tibia is prepared using the metaphyseal bone tapered reamer coupled to the appropriate-sized stem trial. Once this is in place, the 2° tibial cutting block is placed, the reamer removed, and the proximal tibia resected. However, in the vast majority of our revision knee surgeries, we use a tibial metaphyseal sleeve and base the resection of the proximal tibial resection off the sleeve broach.

The mobile-bearing tibial revision broach handle is attached to the smallest broach and the appropriate trial stem (Figure 8). The broach is carefully impacted into the tibia until the top surface of the broach is at the desired proximal tibial resection level (Figure 9). If the broach is unstable or if any defect is unfilled, the procedure is repeated with consecutively larger broaches until the desired fit is achieved. It should be noted that with the mobile-bearing tibial revision tray, only the 29-mm metaphyseal sleeve can accept tibial augmentation. The broach handle is removed, leaving the last broach in place. The proximal tibia may now be resected using the top of the broach as a guide (Figure 10). The trial tibial base plate is assembled with the appropriate-sized trial metaphyseal sleeve and trial stem and inserted.

Figure 7: Adequate exposure is an essential component of revision knees surgery. The tibia is subluxed anteriorly for reaming of the medullary canal.	Figure 8: The M.B.T. Metaphyseal broach. Figure 9: Broaching for the metaphyseal sleeve.

Joint Space Assessment

The joint space is evaluated with spacer blocks to determine the flexion-extension gaps. The balance and symmetry of both the flexion and extension gaps are established as well as what prosthetic augmentation is needed to ensure postoperative equivalence (Figure 11). With the tibia sized and the approximate joint line established, the preliminary femoral component size can be selected by evaluating the explanted component, radiography templates, femoral sizing templates, femoral sizing caliper, or by sizing against the cutting guide. The femoral component size is best estimated by preoperatively templating a lateral radiograph of the operative knee before surgery or the contralateral native knee. If the contralateral knee has been replaced, a lateral radiograph is still beneficial in templating, assuming the knee is functioning well. At the time of revision surgery, the femoral component is often the same size of the tibia, or, more commonly, one size larger.

Figure 10: Proximal tibial resection using the metaphyseal broach as a guide.	Figure 11: Spacer blocks are used to determine the flexion and extension gaps and to ensure a quadrilateral space.

To decrease the flexion gap without affecting the extension gap, a larger femoral component is applied with the addition of posterior augmentation. This is particularly important where an IM stem extension is indicated, because the stem extension will determine the anteroposterior positioning of the component and the consequent flexion gap. The alternative – additional distal femoral resection and use of a thicker tibial insert to tighten the flexion gap – is not recommended, because considerable bone stock has been sacrificed in the primary procedure, and it is important that additional resection of the distal femur be avoided.

To decrease the extension gap without affecting the flexion gap, the distal femur is augmented. It is important to note that this will lower the joint line, which is usually desirable because it is generally found to be elevated in knee revision patients. This will lessen the incidence of postoperative patellar infera.

Femoral Preparation

The midline of the femoral trochlea is identified, and the medullary canal is entered with a 9-mm drill to a depth of 3-5 cm. The medullary canal is opened sequentially with reamers of progressively larger size until firm endosteal engagement is established. The flexion gap is determined next, as in the LCS Complete primary knee system. The IM rod and sleeve guide corresponding to the final reamer size are inserted into the distal femur. The anteroposterior cutting block is placed over the rod and sleeve guide, and rotation is set.

For femoral rotation, the tibial trial functions as a reference point. In a knee with competent collateral ligaments, the femoral positioner that references the tibial plateau will create a quadrilateral flexion gap (Figure 12). We find that other anatomic landmarks, such as the epicondylar axis, are unreliable. Anterior resection is performed through the anterior slot. Posterior resection is performed through the slot designated zero or, where there is posterior condyle deficiency, the appropriate 5-mm or 10-mm slot is used to accommodate posterior augments (Figure 13).

Figure 12: Femoral rotation is set forming a rectangular flexion gap.	Figure 13: Anterior and posterior resection.

Figure 14: Distal femoral resection.

The distal femoral cutting block is now assembled onto the anterior-posterior cutting block. The cutting block has slots to allow for a 0-mm clean-up cut and 5 or 10-mm distal augment. The anteroposterior cutting block and IM rod assembly are subsequently removed. In most cases, little if any bone is removed from the distal femur, because the joint line is effectively elevated with the removal of the primary femoral component. As the level of the resection is predicated on the preservation of bone stock, each condyle is cut only to the level required to establish a viable surface, with augmentation used to correct imbalance. Resection is performed through the slot appropriate for each condyle (Figure 14).

Final femoral preparation involves notch and chamfer resection. Where augmentation is planned, the appropriate augment buttons are inserted into their receptacles on the finishing guide (Figure 15). Fixation pins are introduced to secure the cutting block. The IM guide is carefully removed, and chamfer and notch cuts are made.

Optional femoral metaphyseal sleeves are also available to the knee revision surgeon. These are useful when severe bone loss is encountered in the femoral notch. Much like tibial metaphyseal sleeves, they allow for the filling of bony defects and give the femoral component a stable base for solid fixation to the metaphyseal bone. The femur is sequentially broached to the desired dimension. Care is taken to ensure that the broach remains centered in the path of the IM reamers. This will keep the metaphyseal sleeve in the desired anteroposterior position.

The trial femoral component is now assembled and inserted. Once the appropriate thickness polyethylene trial insert is in place, the knee is taken through a range of motion to verify function and stability. If the surgeon chooses, and bone stock permits, the patella may be revised as well. At this point, the trial components are removed and the final implants may be inserted.

Conclusion

The long-term clinical success of the LCS Knee Revision System as a primary knee arthroplasty system is well established. The mobile-bearing knee prosthesis was developed to restore normal knee function and to protect the polyethylene bearing from excessive forces, thereby limiting wear. Mobile-bearing prostheses are a means to achieve high conformity between the articular surfaces of the implant while maintaining acceptable polyethylene stresses at a safe level. If the knee surgeon accepts the concept of low contact stress arthroplasty, it is only logical to apply these principles to the clinically compromised patient. The LCS Complete Knee System for revision was designed to combine the established benefits of a rotating platform with a comprehensive array of implants and augments to address the issues of contemporary revision knee arthroplasty.

Figure 15: Finishing cuts are made with all augments in place.

References

1. Callahan CM, Drake BG, Heck DA, Dittus RS. Patient outcomes following tricompartmental total knee replacement. a meta-analysis. JAMA. 1994; 271:1349-1357.
2. Gonzalez MH, Mekhail AO. The failed total knee arthroplasty: evaluation and etiology. J Am Acad Orthop Surg. 2004; 12:436-446.
3. Sinha RK, Crossett LS, Rubash, HE. Extensor mechanism disruption after total knee arthroplasty. In: Insall JN, Scott WN, eds. Surgery of the Knee. 3rd ed. New York, NY: Churchill Livingstone; 2001:1863-1873.
4. Wong R, Lotke P, Ecker M. Factors influencing wound healing after total knee arthroplasty. Orthop Trans. 1986;10:497-507.
5. Ayers D, Dennis DA, Johanson NA, Pellegrini VD. Instructional course lectures: the American Academy of Orthopaedic Surgeons. Common complications of total knee arthroplasty. J Bone Joint Surg Am. 1997;79:278-311.
6. Lavernia C, Lee DJ, Hernandez, VH. The increasing financial burden of knee revision surgery in the United States. Clin Orthop Relat Res. 2006;446:221-226.
7. Buechel FF Sr, Buechel FF Jr, Pappas MJ, D’Alession J. Twenty-year evaluation of meniscal bearing and rotating platform knee replacements. Clin Orthop Relat Res. 2001;388:41-50.
8. Jordan LR, Olivio JL, Voorhorst PE. Survivorship analysis of cementless meniscal bearing total knee arthroplasty. Clin Orthop Relat Res. 1997;338:119-123.
9. McEwen HMJ, Fisher J, Goldsmith AA, et al. Wear of fixed bearing and rotating platform mobile bearing knees subjected to high levels of internal and external tibial rotation. J Mater Sci Mater Med. 2001; 2:1049-1052.
10. Mars H, Barton DC, Jones RA, et al. Comparative wear under four different tribiological conditions of acetylene enhanced cross-linked ultra high molecular weight polyethylene. J Mater Sci Mater Med. 1999;10:333-342.
11. Wang A, Stark C, Dumbleton JH. Mechanistic and morphological origins of ultra-high molecular weight polyethylene wear debris in total joint replacement prostheses. Proc Inst Mech Eng [H]. 1996; 210:141-155.
12. Bartel DL, Burnstein AH, Toda MD, Edwards DL. The effect of conformity and plastic thickness on contact stresses in metal-backed plastic implants. J Biomech Eng. 1985; 107:193-199.
13. Kuster MS, Stachowiak GW. Factors affecting polyethylene wear in total knee arthroplasty. Orthopedics. 2002; 25(suppl 2)S235-S242.
14. Younger AS, Duncan CP, Masri BA. Surgical exposures in revision total knee arthroplasty. J Am Acad Orthop Surg. 1998; 6:55-64.
15. Masri AM, Mitchell PA, Duncan CP. Removal of solidly fixed implants during revision hip and knee arthroplasty. J Am Acad Orthop Surg. 2005; 13:18-27.

Authors

Drs Lippe and Crossett are from the University of Pittsburgh School of Medicine, Pittsburgh, Pa.

Injection in the Cervical Facet Joint for Shoulder Pain With Myofascial Trigger Points in the Upper Trapezius Muscle

Shoulder/Elbow

By Chien-Tsung Tsai, MD, MSc; Lin-Fen Hsieh, MD; Ta-Shen Kuan, MD, MS; Mu-Jung Kao, MD; Chang-Zern Hong, MD
ORTHOPEDICS 2009; 32:557

Abstract

The goal of this double-blinded, randomized, controlled study was to confirm the effectiveness of the cervical facet joint injection in treating shoulder pain with the myofascial trigger point in the upper trapezius muscle secondary to cervical facet lesion. Eighty-nine patients with chronic unilateral shoulder pain due to myofascial trigger points in the upper trapezius muscle received an injection to the C4-5 facet joint in the experimental group and to the corresponding unilateral multifidi muscle in the control group. Subjective pain intensity and pressure pain threshold of the myofascial trigger point were assessed, and the prevalence of endplate noise in the myofascial trigger point region was measured in 28 patients before, immediately after, and 1 month after the injection.

Half of the patients in the experimental group, but none of the control patients, reported being completely pain free 1 month after the injection. Both the decrease in the pain intensity and the increase in pressure pain threshold were significantly more in the experimental group than in the control group either immediately or 1 month after the injection. There was no significant difference in the change of endplate noise prevalence between the 2 groups.

This study demonstrates that intra-articular or peri-articular injection into the cervical facet joint region can effectively inactivate the upper trapezius myofascial trigger point secondary to the facet lesion.

Shoulder pain in the upper trapezius region is a frequent complaint in clinical practice.¹ In most cases, >1 myofascial trigger points can be identified in the upper trapezius muscles, and inactivation of the myofascial trigger points may provide complete relief of shoulder pain.¹

A myofascial trigger point is the most sensitive spot in a taut band of skeletal muscle.¹ Nearly every normal adult has latent myofascial trigger points that are tender but not spontaneously painful. A non-painful latent myofascial trigger point can become an active painful myofascial trigger point in response to a soft tissue lesion near or remote to it via central sensitization (increase of the sensitivity in the central pain pathway of this myofascial trigger point, elicited by the irritable impulse from another source).^2-4 An active myofascial trigger point is painful spontaneously or during movement.¹ There are many sensitive loci (probably sensitized nociceptors) in a myofascial trigger point region.^2,4,5

Endplate noise can be recorded from a myofascial trigger point region more frequently than from a non-myofascial trigger point site.^6,7 Endpoint noise is non-propagated potentials due to excessive leakage of acetylcholine in a dysfunctional endplate associated with myofascial trigger point.^6,7 It has been demonstrated that the irritability of a myofascial trigger point is inversely proportionate to the pressure pain threshold^8,9 and directly proportionate to the prevalence of endplate noise in that myofascial trigger point region.¹⁰ A painful myofascial trigger point of the upper trapezius can be inactivated immediately after a myofascial trigger point injection; however, the pain frequently recurs a few weeks after the injection if the underlying lesion that causes the activation of the myofascial trigger point is not eliminated.

It has been suggested that a facet joint lesion of the cervical spine, especially at the C4-5 or C5-6 level, is one of the important causes of shoulder and/or scapular pain.^11-13 Previous studies have indicated that the pain from the C4-5 facet joint may refer or traverse to the shoulder region.^14-16 In many cases, the pain of the myofascial trigger point in the upper trapezius muscle can be elicited or aggravated by rotating the neck to the painful side, followed by extending the neck backward (stimulation to the ipsilateral cervical facet joints, mainly at the C4-5 and C5-6 levels).^11,12,14,17 An injection to the C4-5 and/or C5-6 facet joints can provide long-term relief of shoulder pain.^11,12 Cervical facet joint injection, either intra-articularly or peri-articularly, has been applied in treating pain in the neck region, and sometimes the shoulder pain referred from a facet joint if the pain is caused by a facet joint lesion, but the effectiveness is still controversial.^18-20 Therefore, this double-blinded, controlled study was designed to assess the effectiveness of the cervical facet joint injection in treating shoulder pain of facet joint origin.

Materials and Methods

General Design

Patients with unilateral shoulder pain with active myofascial trigger points in the upper trapezius muscle and who met the criteria (listed in the next section) were recruited for this study. Intra-articular or peri-articular injections to the involved C4-5 facet joint were given to patients in the experimental group, and local injections to the multifidus muscle in the painful side at the same vertebral level were given to patients in the control group. The subjective pain intensity, the pressure pain threshold, and the prevalence of endplate noise in the myofascial trigger point region of the upper trapezius were measured before, immediately after, and 1 month after the injection. Since neither the patients nor the examiners doing outcome assessments were aware of group assignment, the study was considered double-blinded.

Patients

Patients with unilateral shoulder pain were recruited for the study. Inclusion criteria included: (1) having chronic pain in the shoulder region for >3 months with poor responses to any previous treatment; (2) having no previous cervical facet joint injection; (3) having a myofascial trigger point in the ipsilateral upper trapezius muscle; (4) having positive provoking tests (both facet irritation tests and facet compression tests) to irritate the ipsilateral C4-5 facet joint to reproduce or aggravate the patient’s complaint; (5) having no treatment for such pain other than physical therapy and/or oral nonsteroid analgesics within 1 month prior to the study; (6) having no contraindication for needling of the neck, such as bleeding tendency, local infection in the neck region, serious medical problems, recent neck or upper back trauma (within 1 month), or pregnancy; (7) having no condition such as cognitive deficit or substance abuse (including alcohol) that may interfere with the assessment of pain intensity or pain threshold; (8) having no thick subcutaneous fat in the neck (so that the facet joint could be palpated); (9) having no neurological deficit in the upper limbs based on neurological examination and electrodiagnostic tests; (10) having no destructive lesion, severe sclerotic lesion, or disk herniation with cervical spinal cord compression on radiographs or magnetic resonance imaging (MRI); and (11) having had no previous surgery to the neck region. After signing the approved consent form, which was approved by the Institutional Review Board, the selected patients were randomly divided into 2 groups: experimental and control.

Identification of Myofascial Trigger Point

Diagnosis of a myofascial trigger point is based on the most sensitive, tender spot in a palpable taut band and on recognized pain when the sensitive spot is compressed.^21,22

Provoking Tests for Diagnosis of Facet Joint Lesion

Cervical facet irritation test. When the patient turned his or her head to the side with pain, followed by extension of the neck, pain in the upper trapezius myofascial trigger point was aggravated. This was considered a positive facet sign. To increase the degree of irritation to the C4-5 facet, the examiner’s index finger was placed just below the C4-5 facet joint before the rotation–extension movement of the neck. If the pain got stronger, this was considered a positive C4-5 facet sign.

Cervical facet compression test. When the ipsilateral C4-5 facet joint was compressed with the examiner’s finger, pain in the myofascial trigger point of upper trapezius could be aggravated. This was considered a positive facet compression test. The ipsilateral C5-6 facet joint was also compressed. If the shoulder pain elicited by C5-6 facet compression was stronger than that elicited by C4-5 facet compression, the patient was excluded from this study.

Identification of C4-5 facet joint by palpation. The patient was in a side-lying position (lateral decubitus) with a pillow to support the head and neck on the nonpainful side (Figure 1). The pressure between the pillow and the supporting surface of the neck and head was as evenly distributed as possible. The neck was in the neutral position from the C5 to C7 levels, but slightly bending to the nonpainful side (downward) from the C4 up to the C2 level. In this way, a mild convex curve in the symptomatic side could be noticed. Then the physician who gave the facet injection put the index finger of his nondominant hand on the clavicle head of the sternocleidomastoid muscle at the C4-5 level, and then slid it backward slowly and deeply (to separate the scalenus medius muscle anteriorly and the levator scapulae muscle posteriorly) until the transverse process could be palpated. Then his finger was moved in a longitudinal direction (up and down) to feel the most prominent site (facet joint). In this way, the lowest level of facet joint that could be palpated was the C5-6 facet, and the C4-5 facet was 1 level above.

Figure 1: Positioning for cervical facet joint injection.

Injections

For all patients in both groups, a solution containing 1.0 mL of triamcinolone (40 mg/mL) and 1.0 mL of 1% lidocaine was prepared for injection. A 3-mL syringe and a #27 needle (diameter 0.4 mm) with a length of 1.25 inches were used for injection.

Cervical facet joint injection for the experimental group. When the C4-5 facet joint was identified, the index finger of the physician’s nondominant hand would remain unmoved to guide the needle (Figure 2). After sterilization, the needle penetrated the skin at a site 1 to 2 mm above the C4-5 facet joint at an angle aimed toward the C4-5 facet joint. The syringe was held gently with the thumb and long finger of the physician’s dominant hand, similar to Hong’s technique for myofascial trigger point injection.¹ The index finger was on the non-needle end of the syringe to withdraw and push the solution (Figure 3). The needle was moved slowly toward the C4-5 facet joint until it encountered the bone. Then the needle was pulled out slightly (approximately 1 mm) and reinserted in any direction (but avoiding the anterior direction beyond the facet margin) to another point approximately 0.5 to 1.0 mm from the last insertion site. This procedure was repeated continuously in a sequence to map the depth of the structures at and near the facet joint.

Figure 2: Posteroanterior (left) and lateral (right) views of palpation and injection of the facet joint and the location of the needle tip.

Figure 3: Control of the syringe: withdrawal (left) and injection (right).

When a narrow dip (facet joint or near facet joint) could be felt, the solution in the syringe was pushed into this space. In our clinical experience, approximately 0.5 to 1.0 mL of solution can be injected into the facet joint with no significant resistance. If the solution could not be pushed out from the syringe due to a strong resistance, this procedure was repeated until the solution could be injected without resistance. However, if the dip space (facet joint) could not be identified in 10 attempts of needle placement, the solution was injected into the most prominent portion of the palpable facet region. This would be a peri-articular injection. In many cases, the patient reported a sharp pain sensation when the needle encountered the facet joint. This technique requires delicate feeling on the accurate location of the needle tip via the sensation of the thumb and index finger that held the syringe. The remaining solution was discarded after injection.

In a pilot (unreported) study by our group, C4-5 facet joints of 8 patients were injected by 1 physiatrist using this palpation technique, and also under simultaneous fluoroscopic observation by an experienced radiologist. In all cases, the accurate location of the needle tip had also been confirmed by this radiologist once the physiatrist reported an accurate position of the needle tip.

Cervical deep paraspinal muscle injection for the control group. To avoid injection at the facet joint, the ipsilateral C4-5 facet joint was identified and compressed with the index finger of the physician’s nondominant hand during the whole procedure. Similar to facet joint injection, the index finger remained unmoved to guide the needle. After sterilization, the needle penetrated the skin at a site approximately 2 to 3 mm above the C4-5 facet joint. Then the needle was moved in a direction at least 3 mm away from the C4-5 facet joint. When the needle tip reached a depth closed to the bone, 1.0 mL of the solution was injected into the multifidus muscle. The needle was moved in and out 3 to 5 times before being withdrawn from the skin. The remaining solution was discarded after injection.

Post-injection care. Immediately after the injection, the injected region including the facet joint and the site of needle penetration was compressed firmly to avoid post-injection bleeding, the major cause of post-injection soreness,^5,23 for at least 3 minutes. The patient was allowed to take non-steroid analgesic medicine for post-injection pain or any residual myofascial pain as necessary.

Assessments

Subjective assessment of pain intensity. Pain intensity was subjectively reported by the patient using a numerical pain scale from 0 to 10, with 0 representing no pain and 10 representing the worst imaginable pain. The patient was also informed that a value of pain intensity <5>

Assessment of the pressure pain threshold. The pressure pain threshold measurement procedure recommended by Fischer^24,25 was used in this study. The patient was in a comfortable sitting position and encouraged to maintain complete relaxation. The procedure was explained to the patient clearly, then the identified myofascial trigger point of the upper trapezius muscle was marked so that the 3 consecutive measurements could be performed over the same area. A pressure algometer was used to measure the pressure pain threshold. This pressure algometer was applied on this marked area with the metal rod perpendicular to the surface of the skin. The pressure of compression was increased gradually at a speed approximately 1 kg/sec. The patient was asked to report any distinct increase of pain or discomfort. The compression stopped as soon as the patient reported pain, and the reading on the algometer was recorded as a pressure pain threshold value. The patient was asked to remember this level of pain or discomfort at that point and to apply the same criterion for the next measurement.

Three repetitive measurements at an interval of 30 to 60 seconds were performed at each site. The average values of the 3 pressure pain threshold readings were used for data analysis. Three well-trained examiners (C.T., T.K.) performed this measurement. The same patient was examined and measured by the same examiner for all measurements at different times. The examiners were blinded regarding whether the patients were in the experimental or control group.

Assessment of the prevalence of endplate noise in the trigger point region. A 4-channel electromyography machine was used to record the electrical activity in the myofascial trigger point region with disposable monopolar Teflon-coated electromyography needle electrodes. The first channel recorded the electrical activity from the active electrode (experimental needle electrode) in the myofascial trigger point region. The reference needle electrode was placed in a site approximately 3 to 4 cm from the myofascial trigger point. The second channel recorded the electrical activity from the control site. For the control recordings, the active recording electrode was place in a non-myofascial trigger point region outside the endplate zone. The reference electrode was connected to the reference electrode of the first channel through a bridge connector to form a common reference electrode. A ground electrode was placed on the skin near the recording sites. For both channels, the sensitivity of recording was set at 20 µV per vertical division, and the spread speed was set at 10 milliseconds per horizontal division. The high frequency filter was set at 10 kHz and the low frequency filter at 20 Hz.

The procedure to assess the endplate noise prevalence was similar to that used in previous studies.^6,7 The active recording needle electrode was inserted progressively into the myofascial trigger point region. The needle was advanced gently and slowly through the least possible distance (usually 1 to 2 mm) by simultaneously rotating the needle to facilitate smooth entry through the tissue. After 5 thrusts (advancements of the needle in 1 track), the needle was pulled out to the original insertion depth and reinserted in a slightly different direction (a near track). This procedure was repeated again to explore a total of 25 thrusts (5 thrusts/insertions × 5 insertions). All occurrences of endplate noise were recorded. Three well-trained examiners performed this measurement. The same patient was examined and measured by the same examiner for all measurements at different times. The examiners were blinded regarding whether the patients were in the experimental or control group.

Statistical Methods

The mean and standard deviation of the values measured for pain intensity, pressure pain threshold, and endplate noise prevalence were calculated. An analysis of variance was used to assess the differences among the data before, immediately after, and 1 month after injection, and also the differences between the 2 groups. The changes in pain intensity, pressure pain threshold, and endplate noise prevalence after injection were further normalized as follows: percentage of changes=[(post-treatment data–pre-treatment data)/pre-treatment data]×100%. After data normalization, the differences in the changes of pain intensity, pressure pain threshold, and endplate noise between the 2 groups were compared with a Student t test. For all statistical analysis, the confidence interval was set at 95% (P<.05).

Results

Eighty-nine patients met the inclusion criteria, signed the consent forms approved by the Institutional Review Board, and completed the whole course of the 1-month study. As shown in Table 1, the experimental group consisted of 46 patients and the control group consisted of 43 patients. There were no statistical differences in the mean age, mean duration of onset, and causes of shoulder pain between the 2 groups.

Changes in Subjective Pain Intensity in the Experimental Group

As listed in Table 2, 12 patients in the experimental group reported being pain free immediately after the injection. Only 1 of these 12 patients had pain intensity increase to 1 on the 10-point scale 1 month later, and the rest remained pain free. Besides these 12 pain-free patients, an additional 12 patients reported being pain free 1 month after the injection. Half of the patients in the experimental group were pain free 1 month after the injection, and only 9% of patients still had intolerable pain (pain intensity >5).

Changes in Subjective Pain Intensity in the Control Group

No patients in the control group reported being pain free either immediately after or 1 month after the injection (Table 2). In fact, the majority of patients in the control group reported pain (pain intensity >5).

Comparison of Changes in Subjective Pain Intensity Between the Two Groups

Table 3 shows the comparison of changes in pain intensity between the 2 groups before and after the injection. In the experimental and control groups, there was a significant decrease in pain intensity immediately after and 1 month after the injection (P<.05). However, in comparing the difference in the percentage of change (decrease in pain intensity) between the experimental and control groups, the mean pain intensity reduced significantly more (P<.05) in the experimental group than the control group, both immediately after and 1 month after the injection.

Changes in Pressure Pain Threshold

The mean values of pressure pain threshold in both the experimental and control groups before and after the injection are listed in Table 4. There was a significant increase in pressure pain threshold in the experimental group (P<.05) but not in the control group (P>.05) either immediately after or 1 month after the injection. Comparing the difference in the percentage of change (increase in pressure pain threshold) between the experimental and control groups, the mean pressure pain threshold increased significantly more (P<.05) in the experimental group than the control group, both immediately after and 1 month after the injection.

Changes in Prevalence of Endplate Noise

The mean values of endplate noise prevalence in both groups before and after the injection are listed in Table 5. There was a significant decrease in endplate noise prevalence in the experimental group (P<.05), but not in the control group (P>.05) immediately after the injection. However, 1 month after the injection there was no significant change in endplate noise prevalence compared to the value before the injection in either the experimental or the control group. There was no significant difference in the percentage of changes in endplate noise prevalence between the experimental and the control groups either immediately after or 1 month after the injection (P>.05).

Comparison Between Intra-articular and Peri-articular Injections in the Experimental Group

In the experimental group, 6 patients (3 men and 3 women, average age 48.0±11.4 years) who also had degenerative facet joints were injected peri-articularly rather than intra-articularly. They all reported a significant improvement, with pain intensity <3>

Adverse Effects

Only patients with poor responses to the injection required nonsteroid analgesic medicine. No significant adverse effects other than post-injection soreness for a few hours were observed in all patients.

Discussion

This study demonstrates the short-term therapeutic effectiveness of C4-5 facet joint injection in treating ipsilateral shoulder pain with myofascial trigger points in the upper trapezius muscle secondary to cervical facet lesion. The effect lasted for at least 1 month.

Possible Mechanism of Shoulder Pain Relief After Cervical Facet Joint Injection

The mechanism of cervical facet injection for pain relief is unclear.¹⁹ The cervical facet joint is innervated by the medial branch of posterior rami of the cervical root.²⁶ There are nociceptors in the cervical facet joint capsules,^27,28 especially in the posterolateral capsules.²⁸ When the facet joint is injured or inflamed, the facet nociceptors may transmit the nociceptive information to the brain via the spinal cord. In the spinal cord, the sensory impulse may also transmit to other dorsal horn neurons of other receptive fields. Similar to the mechanism of referred muscle pain suggested by Mense,^29-31 it may also cause referred pain in other sites, such as the shoulder. Therefore, the upper trapezius myofascial trigger point can be activated via central sensitization. This is the probable mechanism of the referred shoulder pain from a C4-5 facet joint lesion.

Evidence exists of the association between active myofascial trigger points and lesions of non-muscular origin, such as osteoarthritis of knee,³² cervical disk lesion,³³ or cervical facet lesion.¹³ Chiropractic adjustment³⁴ or local injection¹¹ of the cervical facet joint could inactivate the myofascial trigger points. Bogduk and Simons¹³ have suggested that facet nociceptors and myofascial trigger point nociceptors may be connected in the spinal cord and may use the same nociceptive pathway to the higher center. Therefore, when the pain in the facet joint is suppressed, the pain due to myofascial trigger point can also be controlled, and vice versa. However, we found no case in the literature of cervical facet joint pain completely controlled with a myofascial trigger point injection of the upper trapezius muscle. Furthermore, if the pain in the upper trapezius myofascial trigger point is not elicited by the cervical facet lesion, the pain relief in the myofascial trigger point region should not last long after the facet joint injection. In fact, long-term relief of a myofascial trigger point pain could be observed in this study (longer than 1 month) and in a previous case report (longer than 1 year).¹¹

During physical examination, provoking tests to irritate the related level of the facet joint can elicit pain in the myofascial trigger point region, but stimulation of the associated myofascial trigger point can rarely induce pain in the correlated facet joint. Therefore, facet dysfunction may be one of the important causes to activate remote myofascial trigger points. This study has further supported the importance of treating the underlying etiological lesion for long-term relief of myofascial pain due to myofascial trigger points.^3,12

This study also demonstrated immediate pain relief after the facet injection. Theoretically, the anti-inflammatory effect from a local steroid injection is not an immediate process. The immediate pain relief may be related to hyperstimulation analgesia from the needle stimulation, similar to myofascial trigger point injection or acupuncture.^3,12,35 Strong stimuli to nociceptors may elicit strong neural impulses to the spinal cord interneurons, including the hypothetic myofascial trigger point circuit of a myofascial trigger point,^3,12 to inhibit the cycle of pain and thus provide immediate pain relief. Therefore, in addition to the anti-inflammatory effect, a local steroid injection may also provide a hyperstimulation analgesic effect.

Changes in Pressure Pain Threshold and Endplate Noise Prevalence

In this study, improvement in the myofascial trigger point irritability estimated with pressure pain threshold was significantly more in the experimental group than in the control group. However, the change in endplate noise prevalence was only temporary. It is likely that the mechanism of pain relief after the facet injection is a central (spinal cord level) desensitization process with little, if any, influence on the myofascial trigger point itself. Therefore, after the facet joint injection, the irritability of myofascial trigger point measured peripherally with endplate noise prevalence is still high, although the pain sensation is reduced via the central desensitization. However, the assessment of pressure pain threshold depends on a subjective report of pain and can be influenced by the central desensitization process.

Technique Issues

The facet joint injection technique in this study could be blinded visually, but was not blinded for the identification of the facet joint by palpation (tactile sensory feedback). Using this technique, we injected the facet joint from lateral and posterior approaches. In an animal study, it was found that more nociceptors could be identified in the dorsolateral aspect of the cervical facet joint than other sites.²⁸ This technique is less time consuming, results in less radiation exposure, and is less expensive.

By using the compression/palpation technique (Figure 3), a shorter needle can be used, and thus less tissue destruction would be expected. No serious side effects (such as an injection into the spinal cord or the vertebral artery) would be expected if the procedure were performed carefully. One important concern is that multiple insertions of the needle may cause extensive tissue damage; however, if the side movement of the needle can be avoided, tissue damage can be minimized. In fact, even under the guidance of fluoroscopy^18,19 or ultrasound,³⁶ the chance of one-time insertion into the facet joint is also not high. In our practice, we could usually reach the facet joint with fewer than 5 needle insertions, and sometimes with 1 insertion. Post-injection soreness was mild and temporary (<12>3 minutes.

The major problem with this technique is the requirement of a high skill of palpation on the facet joint. Not every physician is well trained in this technique. Another problem is the difficulty in palpation on the neck of a patient with thick subcutaneous fat. Such patients would be excluded from receiving an injection with this technique.

Conclusion

This study demonstrates that a facet joint injection, either intra-articularly or peri-articularly, at the C4-5 level using a careful palpation technique may effectively suppress shoulder pain with upper trapezius myofascial trigger points due to facet lesion immediately after the injection and possibly for 1 month afterward. The study also supports the hypothesis that the myofascial trigger point in the upper trapezius muscle can be caused by a cervical facet lesion at the C4-5 level.

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Authors

Dr Tsai is from the Department of Rehabilitation Medicine, Da Chien General Hospital, Miao-Li City, Dr Hsieh is Department of Physical Medicine and Rehabilitation, Shin Kong Wu Ho-Su Memorial Hospital School of Medicine, Fu Jen Catholic University, Taipei, Dr Kuan is from the Department of Physical Medicine and Rehabilitation, College of Medicine, National Cheng-Kung University, Tainan, Dr Kao is from the Department of Rehabilitation Medicine, Taipei City Hospital, Taipei, and Dr Hong is from the Department of Physical Therapy, Hung-Kuang University, Sha Lu, Taichung, Taiwan.

Drs Tsai, Hsieh, Kuan, Kao, and Hong have no relevant financial relationships to disclose.

Correspondence should be addressed to: Chang-Zern Hong, MD, Department of Physical Therapy, Hung-Kuang University, 34 Chung-Chie Rd, Sha Lu, Taichung 433, Taiwan.

DOI: 10.3928/01477447-20090624-04