Design Project. Dr. Kevin O Kelly, TCD

Transcription

1 Design Project Project title: Mentor: Total Ankle Replacement Dr. Kevin O Kelly, TCD Background The ankle joint is a comparatively small joint relative to the weight bearing and torque it must withstand. These factors have made the design of total ankle joint replacements technically challenging. Total ankle replacement has been investigated since the 1970s with initially promising results, but the procedure was essentially abandoned in the 1980s due to a high long-term failure rate, both in terms of pain control and improved function. However, researchers have continued to investigate new designs, which can be broadly subdivided into constrained and unconstrained designs. Constrained prosthesis offer the advantage of greater stability, but with decreased mobility and increased stress at the bone implant interface, potentially leading to a greater risk of early loosening and failure. Unconstrained designs provide improved range of motion in multiple planes, but at the expense of stability. The first devices investigated were implanted with cement fixation, which in recent years has given way to cementless designs. Currently, seven ankle prostheses are commercially available or under investigation in this country. In May 2002, the FDA approved the Agility Ankle Revision Prosthesis (DePuy Orthopaedics, Inc.), which is intended for cemented use only in patients with a failed previous ankle surgery. In November 2005 and November 2006, respectively, the FDA approved the INBONE Total Ankle (Depuy Orthopaedics, Inc.) (formerly known as Topez Total Ankle Replacement System from Topez Orthopedics, Inc.), the Salto Talaris Total Ankle Prosthesis (Tornier) and the Eclipse Total Ankle Implant (Kinetikos Medical Inc.) as being substantially equivalent to the Agility model and with the same indications for use. Prostheses that are not currently approved by the FDA include the STAR (Scandinavian Total Ankle Replacement) (Link America, Inc.) device, the Buechel-Pappas device, and the TNK ankle. These are non-cemented, non-constrained mobile bearing devices. The main alternative to total ankle replacement is arthrodesis. While both procedures are designed to reduce pain, the total ankle replacement is additionally intended to improve function. While total ankle replacement is performed most commonly in patients with severe rheumatoid arthritis, patients with severe osteoarthritis, septic arthritis or posttraumatic osteoarthrosis may be considered candidates. Scientific Background The following outcomes are relevant to the analysis of safety and efficacy of total ankle replacement, compared to ankle arthrodesis, the standard treatment alternative: 1. Resolution of pain 2. Function of both the ankle and proximal joint in various activities, such as walking on flat or irregular surfaces, or walking up stairs

2 3. Long term outcomes For example, if an arthrodesis or ankle replacement is not properly aligned, significant gait abnormalities may result. In addition, an arthrodesis puts additional strain on proximal joints, which may in turn accelerate the development of arthritis in the knee and hip. The principal limitations of past total ankle replacement have been loosening of the prosthesis, requiring revision. If the prosthesis requires removal, the success of a subsequent arthrodesis must be considered. Different prostheses require different amounts of removal of bone stock, potentially compromising the success of a subsequent arthrodesis. At the present time there are inadequate data on available total ankle replacements to permit conclusions regarding their safety and effectiveness. The STAR, Beuchel-Pappas, and TNK ankle devices have not yet received FDA approval, and there is little published information. One case series of 100 consecutive total ankle replacements using the Agility Ankle has been published. (2) Follow-up ranged from 2 to 12 years; the prostheses were implanted between 1984 and Patients were evaluated with an interview focusing on pain and activities of daily living, and clinical and radiologic examination. Of the 85 ankles in 83 patients that were available for follow-up, 98% were associated with some level of pain relief. A total of 74% of patients reported an increase in their functional level. Based on radiologic exams, 36% of prosthesis were associated with a delayed union or nonunion. Migration of talar or tibial components of the prosthesis was also noted; migration of the tibial component was associated with nonunion. Nonunion was associated with ballooning lysis at the interface between the bone and tibial component, although lysis was also seen in cases when a solid union was present. The authors conclude that these intermediate results are encouraging, although the radiographic findings created concerns about long term outcomes. Another case series of 86 cases has been published and reported similar results. (3) While 79 of the 86 cases (92%) reported a favorable outcome, there were similar radiographic findings. A total of 22% of prosthetic components had migrated and 8 of the 12 tibial components that had migrated involved a delayed union or nonunion. The lack of any control group precludes a comparison of the prosthesis to arthrodesis. In 2004 Knecht and colleagues (4) reviewed the outcomes in a continuation of the study previously reported by Pyevitch and colleagues (2) with the addition of five more years of follow-up (average follow-up is nine years) and thirty-two additional patients. Since the last follow-up, the revision rate increased by 5%, with seven ankles converted to an arthrodesis and seven converted to another Agility ankle implant. In the prior report Pyevich raised the question of the clinical relevance of radiographic signs of lysis and migration in patients who seemed to be asymptomatic at the time. With five additional years of radiographic and clinical data, it appears that the ankles with implant components that migrated five or more millimeters more often needed revision or arthrodesis. In addition, implant radiographic markers of progressive lysis in any zone, circumferential lucency and anteroposterior lucency were associated with higher pain and disability scores. Talar component settling into the bone was more common than tibial component settling which the authors feel will increase talar component failure over time. Also, in 2004, Spirt and colleagues published a retrospective review on the cause and frequency of reoperation and failure after total ankle arthroplasty and to determine demographic and clinical predictors of reoperation and failure. The medical records of three hundred and six consecutive primary total ankle arthroplasties with the second generation Agility ankle were reviewed. Patients were followed a mean 33 months after arthroplasty. Eighty-five patients (28%) underwent reoperations (involving 168 procedures) after primary total ankle arthroplasty. The most common procedures at the time of reoperation were

3 debridement of heterotropic bone (N=58), correction of axial alignment (N=40), and component replacement (N=31). Eight patients underwent below the knee amputations. In this retrospective review the authors found age to be the only significant predictor of reoperation and failure after total ankle arthroplasty. The five-year survival rate with reoperation as the end point was 54%. The five year survival rate with failure as the end point was 80% for all patients and 89% for patients who were more than fifty-four years of age. Additional case series were published in 2004 of the STAR prosthesis and the Buechal Pappas prosthesis. Neither device has FDA approval. Su and colleagues (6) implanted either the Buechal Pappas Low Contact Stress prosthesis or a custom designed prosthesis in thirtythree patients with rheumatoid arthritis. The average postoperative American Orthopaedic ankle-hindfoot score was 81 of a possible 100, at a mean 6.4 years after surgery. Radiographically, 88.5% of implants were stable without evidence of settling. However, osteolysis occurred in 11.5% of patients. Haskell and colleagues (7) looked at correction of malalignment with intraoperative ligament balancing in eleven patients at two years following TAA with the STAR prosthesis. The authors provide details of realignment and successful maintenance of alignment at two years. However, the study population is small and details of outcomes and overall long term outcomes are not presented. In a 2005 update, one publication on a clinical trial of the STAR prosthesis by Valderrabano and colleagues was identified. (8) In this report, 68 patients with total ankle replacements using the STAR prosthesis were followed for an average of 3.7 years. The authors reported 35 patients were completely free of pain, 67 ankles were graded as good or excellent by overall score and scores on the American Orthopedic Foot and Ankle Society hindfoot improved on average from 24.7 points (range, 3-44 points) to 84.3 points at follow-up. However, there were complications reported including ballooning bone lysis (3 patients), periarticular hypertrophic bone formation (43 ankles) with associated decreased flexion, prosthesis problems requiring revision surgery (9 patients), and additional or secondary surgery (14 patients). Despite complications, results appear encouraging. Nevertheless, the STAR device is still not available in the United States. The Agility-Ankle Revision Prosthesis received FDA clearance for marketing through the 510(k) process (6), and thus detailed clinical outcomes were not required for FDA approval. An updated literature search through September 2006 returned three new published retrospective case series and one prospective case series of total ankle arthroplasty, none of which provided sufficient evidence of the long term safety and effectiveness of total ankle arthroplasty that would result in a policy change. Two studies addressed outcomes with the Agility Total Ankle System (9, 10) and two studies addressed outcomes with the Buechel- Pappas Total Ankle Replacement (BP-TAR) (11, 12). The updated literature search did not identify any clinical trial outcomes data on the Topez Total Ankle Replacement device. Schuberth and colleagues reviewed the records of 50 patients implanted with the Agility device in order to better define the characteristics of the learning curve and whether the rate of complications was increased in patients who required complex reconstruction for preexisting ankle deformities. (9) The average follow-up period was 24 months. This study suggested that with surgeon experience the perioperative complication rate may potentially decrease. However, a larger patient cohort is necessary to show statistically significant differences between the variables studied. Kopp and colleagues conducted a retrospective review of 43 total ankle arthroplasties using the Agility ankle in 41 patients. (12) Patients were followed for an average of 2 years during which time 21 patients had additional procedures. Subjective ankle pain scores improved significantly from baseline. Radiographic follow-up revealed circumferential lucency in eight ankles, lysis in five ankles, subsidence is 18 ankles and three nonunions. Twelve patients experienced complications requiring reoperation. The authors

4 concluded that, the overall intermediate-term clinical results of total ankle replacement using the Agility prosthesis are promising, but the longevity of the prosthesis is questionable because of the frequency of periprosthetic lucency, lysis, and component subsidence. San Giovanni and colleagues conducted a retrospective review of 31 total ankle arthroplasties with the Buechel-Pappas ankle in 23 patients with rheumatoid arthritis. (11) The average follow-up was eight years. The authors report 93% survivorship; however, 18% of patients had radiographic evidence of subsidence possibly indicating impending failure of the prosthesis. Seventy-five percent of the patients rated their post-implant pain as none, 21% as mild, and 4% as moderate. In a prospective pilot study of the Buechel-Pappas device, Nelisson and colleagues studied the direction and migration of the tibial component following 15 total ankle arthroplasties and whether secondary stabilization occurred within the one-year interval following arthroplasty. (12) At two years there were no radiolucencies around the talar component and no signs of bone resorption. Two patients experienced spontaneous distal tibial fracture at two-weeks following surgery. The study indicated that with the unconstrained Buechel-Pappas there is initial migration into upward anterior and valgus tilting but the migration appears to stabilize by six months. An updated search of the literature through December 12, 2008 failed to return any new randomized, controlled trials. There were two meta-analyses and several review articles, all of which reported promising outcomes, but noted the continued controversial nature of total ankle arthroplasty and the need for well-designed comparative studies and long-term data. (13-16) In summary, there are inadequate data on available total ankle replacement prostheses to permit conclusions regarding their safety and effectiveness. Further study involving randomized controlled clinical trials comparing ankle arthroplasty with arthrodesis are necessary to provide long term data in assessing the patient outcomes of total ankle arthroplasty. References 1. BlueCross and BlueShield Association Medical Policy Reference Manual, Policy No Pyevich MT, Saltzman CL, Callaghan JJ, et al. Total ankle arthroplasty. A unique design. J Bone Joint Surg 1998;80A: Conti SF, Bisignani G, Martin R. Update on total ankle replacement. Semin Arthroplasty Reconstruct Foot Ankle 1999;10: Knecht SI, Estin M, Callahan JJ et al. The Agility Total Ankle Arthroplasty. J Bone Joint Surg 2004;86(6): Spirt AA, Assal M, Hansen ST. Complications and Failure After Total Ankle Arthroplasty; J Bone Joint Surg 2004;86-A(6): Su EP, Kahn B, Figgie MP. Total ankle replacement in patients with rheumatoid arthritis. ClinOrtho Rel Res 2004;424; Haskell A, Mann RA. Ankle arthroplasty with preoperative coronal plane deformity. Clin Ortho Rel Res 2004;424; Valderrabano V, Hintermann B, Dick W. Scandinavian total ankle replacement: a 3.7 year average follow up of 65 patients. Clin Orthop Relat Res 2004;(424): Schuberth JM, Patel S, Zarutsky e. Perioperative complications of the Agility Total Ankle Replacement in 50 initial, consecutive cases. Foot Ankle Surg 2006;45(3): Kopp FJ, Patel MM, Deland JT et al. Total ankle arthroplasty with the Agility prosthesis: Clinical and radiographic evaluation. Foot Ankle Surg 2006;27(2): San Giovanni TP, Keblish DJ, Thomas WH et al. Eight-year results of a minimally constrained total ankle arthroplasty. Foot Ankle Surg 2006;27(6): Nelissen RG, Doets HC, Valstar ER. Early migration of the tibial component of the Buechel-Pappas total ankle prosthesis. Clin Orthoped Rel Res 2006;448: Haddad SL, Coetzee JC, Estok R, et al. Intermediate and long-term outcomes of total ankle arthroplasty and ankle arthrodesis. A systematic review of the literature. J Bone Joint Surg Am. 2007;89(9):

5 14. Deorio JK, Easley ME. Total ankle arthroplasty. Instr Course Lect. 2008;57: Guyer AJ, Richardson G. Current concepts review: total ankle arthroplasty. Foot Ankle Int. 2008;29(2): Chou LB, Coughlin MT, Hansen S Jr, et al. Osteoarthritis of the ankle: the role of arthroplasty. J Am Acad Orthop Surg. 2008;16(5): Ideal Patients So who is a good candidate for an ankle replacement? The ideal patient, is someone who is over the age of 50, is not too heavy, and is not extremely active. Some activity is always ideal, and it does not mean however that patients with an ankle replacement have to be sedentary. Quite on the contrary, patients can walk, hike, climb, ride a bicycle, and in some circumstances even ski after ankle replacement. The activities then which are not ideal are those which involve repetitive pounding of the ankle for example running and a job which includes heavy labor. Patients who have poor circulation in the leg, those who have diabetes, or nerve conditions of the leg are not good candidates for an ankle joint replacement. The bone quality of the ankle must be fairly healthy, and we do not normally implant a joint if the ankle bone is dead (a condition called avascular necrosis or AVN of the talus bone). When we perform an ankle replacement, one of the goals is of course to improve the movement of the joint (called the range of motion). Interestingly, the more movement of the ankle that there is before the joint replacement surgery, the more will exist later. If a patient has no motion or very poor motion of the ankle before surgery, we can improve this, but not nearly as much. A patient with very poor movement in the ankle to begin with may be more suited to a fusion of the ankle, since she would not notice the difference in movement after the fusion. On the other hand, the patient with excellent movement of the ankle, even with severe arthritis, would not do well with an ankle fusion, since the loss of movement would be very noticeable.

6 Various types of existing ankle prostheses QuickTime and a decompressor are needed to see this picture. Buechel-Pappas total ankle prosthesis (Endotec). Similar to STAR (Scandinavian Total Ankle Replacement, Waldemar Link) device. The Buechel-Pappas ankle replacement is cementless, three-component (mobile-bearing) design. Tibial component is stabilized by stem that extends into tibial metaphysis (arrowhead). Ultrahigh-molecular-weight polyethylene meniscus (thick arrow) glides along metallic talar component (thin arrow) stabilized by ridge on its undersurface (asterisk) that articulates with corresponding longitudinal groove on talar component. Design allows limited inversion and eversion of ankle joint without loss of congruity and requires minimal talar bone resection. Photograph of Buechel-Pappas arthroplasty device, frontal view.

7 Original DePuy prosthesis. In the United States there is currently only one ankle that has been approved for use by the FDA. This is called the DePuy Agility ankle replacement. The shape of the talar component in particular has been improved from the original. The new talar component is shown on the right hand x-ray and covers the talus almost completely, which prevents later sinking or subsidence of the component into the talus bone.

8 This implantable total ankle replacement system is intended for use in patients where there is severe arthritis or other deformities that hinder the range of motion of the joint. Small Bone Innovations claims that this design of the STAR system is the first of its kind because it relies on movable bearings that glide across the surface of polyethylene. Between the two components sits a plastic (UHMWPE) spacer, the meniscus. This allows movement on both its surfaces. The addition of this omponent, though not present in the normal ankle, allows the artificial joints movement to match the normal ankle more closely. This involves rotation as well as up and down movement (flexion and extension). This ability to match the normal ankles movement also significantly improves the durability of the joint.