Aetna considers total ankle replacement (total ankle arthroplasty) experimental and investigational because its clinical value has not been established.

Total ankle replacement is a procedure in which an injured ankle joint is replaced with a plastic and metal joint. The procedure has been used as an alternative to surgical fusion in patients with loss of ankle function and pain that is refractory to medications, especially because of rheumatoid arthritis. Arthritis from other causes is rarely a reason to do ankle replacement.

Conservative management of ankle pain includes acetaminophen, aspirin, or other medication for pain and inflammation, limiting activity, wearing an ankle brace, shoe modifications, application of heat, and physical therapy.

When conservative measures of treatment fail to provide adequate pain relief, either an ankle fusion or total ankle replacement (ankle arthroplasty) may be considered. Ankle fusion has been the traditional method of treating arthritis of the ankle. In recent years, total ankle replacement has developed as another option. However there are little long-term data on the effectiveness of total ankle replacement. Available data suggest that total ankle replacement has a relatively short lifespan. For this reason, ankle replacements are not usually recommended for people under the age of 50.

The procedure is performed under general or spinal anesthesia. Patients are generally hospitalized for 1 to 4 days. A period of physical therapy is often required after ankle replacement. The patient is able to ambulate within a few weeks following the procedure. The most common complications include thrombophlebitis and pulmonary embolism. Swelling or pressure as a result of the procedure may injure the nerves in the ankle. The new joint can be dislocated rather easily. In addition, there is a risk of infection and hemorrhage.

Encouraged by the excellent results attained by total joint arthroplasty of the hip and knee, several surgeon-engineer teams designed and developed total joint prostheses for the ankle. In the early and middle 1970's reports appeared of early success with these implants in 80% to 85% of patients. In 11 reports that included 346 arthroplasties, good or fair results were reported in 83% and failures in 17% at a mean follow-up of less than 5 years. A wave of enthusiasm developed for total ankle arthroplasty, and the indications for the procedure were expanded, often to include young people engaged in strenuous work or recreational activities. After further experience and longer periods of observation, reviews of most series of total ankle arthroplasties revealed extremely poor long-term results, especially in younger patients with isolated traumatic arthritis. In later reports in which the average follow-up was longer than 5 years, failure occurred in 35% to 76% of arthroplasties.

Comparison of long-term series of total ankle arthroplasty are difficult because of variability in diagnosis, patient age, length of follow-up, prosthesis design, and absence of a uniform scoring system. The largest series of total ankle arthroplasties is that of Kitaoka et al. (1994, 1996), who reported their experience with 204 primary Mayo total ankle replacements. The overall cumulative rate of implant survival was 79% at 5 years, 65% at 10 years, and 61% at 15 years. The probability of an implant being in place at 10 years was 42% for patients 57 years of age or younger and who had previous operative treatment of the ipsilateral ankle or foot and 73% for those older than 57 years of age who had no such previous operative treatment. Because of these poor long-term results, they do not recommend the use of the Mayo total ankle arthroplasty, especially in younger patients who have had a previous operative procedure on the ipsilateral ankle or foot. In a series of 36 constrained Conaxial (Beck-Steffee) ankle replacements, Wynn and Wilde (1992) found that 27% were loose at 2 years, 60% at 5 years, and 90% at 10 years; they recommend that this ankle prosthesis not be implanted.

Complications other than implant loosening also are more frequent after total ankle arthroplasty than after total hip or knee replacement. Delayed wound healing has been reported to occur in as many as 40% of patients, and most long-term series cite rates of deep infection of 3% to 5%. Loosening has been reported in 6% to 25% of implants after 3 to 5 years; usually the talar component is involved. Demottaz, et al. (1979) reported radiolucent zones of 2 mm or more at the cement-bone interface in 88% of prostheses at 1 year, and Unger et al. (1988) reported talar subsidence in 14 of 15 arthroplasties and tibial component tilting in 12 of 15 at an average 6-year follow-up. Wynn and Wilde (1992) reported an overall complication rate of 60%, including wound dehiscence (39%), deep wound infection (6%), fractures of the medial or lateral malleolus (22%), and painful talofibular impingement (14%).

Although some more recent reports of uncemented, unconstrained replacements have shown better short-term results, currently no ankle implants are available that provide consistently good long-term results. There are no prospective randomized controlled clinical trials comparing total ankle replacement to fusion or other alternatives. In a review of total ankle arthroplasty, Saltzman (1999) concluded that despite efforts to develop a workable total ankle replacement the long-term results of most new designs are unknown. Saltzman concluded that prospective clinical trials are needed to determine which factors lead to successful and unsuccessful outcomes.

A 2003 American Orthopaedic Foot and Ankle Society (AOFAS) position statement on total ankle arthroplasty stated that ankle arthritis has many treatment options, both operative and non-operative. Operative treatment is available for patients with persistent symptoms. Surgical options include joint debridement, distraction arthroplasty, osteotomy, ankle arthrodesis and total ankle arthroplasty. Total ankle arthroplasty is a viable option for the treatment of ankle arthritis. However, this position statement does not appear to be substantiated by a vigorous assessment of the technology.

In a review on total ankle replacement, Hintermann and Valderrabano (2003) stated that although the results of the different design approaches are encouraging in limited clinical series, there is still the need for careful, long-term analyses to estimate to what extent the current designs are mimicking the biomechanics of the ankle joint. More attention must be paid to more accurate implantation techniques that result in a well-balanced ligament and allow the ligaments to act together with the replaced surfaces in a most physiological manner. Gill (2004) noted that there is a need for further basic science research in total ankle arthroplasty. The lessons learned from other arthroplasty should be considered in ankle arthroplasty design.

Spirt et al (2004) reported a relatively high rate of re-operation after total ankle arthroplasty with a second-generation total ankle replacement device -- the DePuy Agility Total Ankle System. Younger age was found to have a negative effect on the rates of re-operation and failure. Most prostheses could be salvaged; however, the functional outcome of this procedure is uncertain. Haskell and Mann (2004) tested the hypotheses that pre-operative coronal plane mal-alignment and incongruence of the ankle can be corrected and maintained for 2 years with total ankle replacement. These investigators found that patients with pre-operative incongruent joints are 10 times more likely to have progressive edge-loading develop than patients with congruent joints. They state that surgeons must be attentive to coronal plane alignment during and after ankle replacement, and that longer follow-up is needed to assess the longevity of the correction and the impact of minor mal-alignment on implant wear.

Easley et al (2002) stated that four 2nd-generation total ankle arthroplasty designs have shown reasonable functional outcomes: (i) the Scandinavian Total Ankle Replacement (STAR), (ii) the Agility Ankle, (iii) the Buechel-Pappas Total Ankle Replacement, and (iv) the TNK ankle. They noted that intermediate results are promising but should be interpreted with care. Knecht et al (2004) stated that arthrodesis of the tibiofibular syndesmosis impacts the radiographical and clinical outcomes with the Agility total ankle replacement. The relatively low rates of radiographical hind-foot arthritis and revision procedures at an average of 9 years after the arthroplasty are encouraging. Agility total ankle replacement is a viable and durable option for the treatment of ankle arthritis in selected patients.

On the other hand, in a cost-effectiveness analysis of total ankle arthroplasty, SooHoo and Kominski (2004) stated that the currently available literature has not yet shown that total ankle arthroplasty predictably results in levels of durability and function that make it cost-effective at this time. However, the reference case of this analysis does demonstrate that total ankle arthroplasty has the potential to be a cost-effective alternative to ankle fusion. This reference case assumes that the theoretical functional advantages of ankle arthroplasty over ankle fusion will be borne out in future clinical studies. Performance of total ankle replacement will be better justified if these thresholds are met in published long-term clinical trials. Furthermore, Stengel and associates (2005) performed a meta-analysis of studies exploring the effectiveness of 3-component total ankle prostheses for treating end-stage ankle arthritis of different origin. These investigators concluded that ankle arthroplasty improves pain and joint mobility in end-stage ankle arthritis. Its performance in comparison to the current reference standard (i.e., ankle fusion) remains to be defined in a properly designed randomized trial.

Haddad et al (2007) examined if there are sufficient objective cumulative data in the literature to compare total ankle replacement and ankle fusion. A systematic review of the literature addressing the intermediate and long-term outcomes of interest in total ankle arthroplasty and ankle arthrodesis was performed. Two reviewers evaluated each study to determine whether it was eligible for inclusion and collected the data of interest. Meta-analytic pooling of group results across studies was performed for the two procedures. The analysis of the outcomes focused on second-generation ankle implants. The systematic review identified 49 primary studies, 10 of which evaluated total ankle arthroplasty in a total of 852 patients and 39 of which evaluated ankle arthrodesis in a total of 1262 patients. The mean AOFAS Ankle-Hindfoot Scale score was 78.2 points (95 % confidence interval [CI], 71.9 to 84.5) for the patients treated with total ankle arthroplasty and 75.6 points (95 % CI, 71.6 to 79.6) for those treated with arthrodesis. Meta-analytic mean results showed 38 % of the patients treated with total ankle arthroplasty had an excellent result, 30.5 % had a good result, 5.5 % had a fair result, and 24 % had a poor result. In the arthrodesis group, the corresponding values were 31 %, 37%, 13 %, and 13 %. The 5-year implant survival rate was 78 % (95 % CI, 69.0 % to 87.6 %) and the 10-year survival rate was 77 % (95 % CI, 63.3 % to 90.8 %). The revision rate following total ankle arthroplasty was 7 % (95 % CI, 3.5 % to 10.9 %) with the primary reason for the revisions being loosening and/or subsidence (28 %). The revision rate following ankle arthrodesis was 9 % (95 % CI, 5.5 % to 11.6 %), with the main reason for the revisions being non-union (65 %). One percent of the patients who had undergone total ankle arthroplasty required a below-the-knee amputation compared with 5 % in the ankle arthrodesis group. The authors concluded that on the basis of these findings, the intermediate outcome of total ankle arthroplasty appears to be similar to that of ankle arthrodesis; however, data were sparse. Comparative studies are needed to strengthen this conclusion.

SooHoo et al (2007) compared the re-operation rates following ankle arthrodesis and ankle replacement on the basis of observational, population-based data from all inpatient admissions in California over a 10-year period. The hypothesis was that patients treated with ankle replacement would have a lower risk of undergoing subtalar fusion but a higher overall risk of undergoing major revision surgery. These researchers used California's hospital discharge database to identify patients who had undergone ankle replacement or ankle arthrodesis as inpatients in the years 1995 through 2004. Short-term outcomes, including rates of major revision surgery, pulmonary embolism, amputation, and infection, were examined. Long-term outcomes that were analyzed included the rates of major revision surgery and subtalar joint fusion. Logistic and proportional hazard regression models were used to estimate the impact of the choice of ankle replacement or ankle fusion on the rates of adverse outcomes, with adjustment for patient factors including age and comorbidity. A total of 4705 ankle fusions and 480 ankle replacements were performed during the 10-year study period. Patients who had undergone ankle replacement had an increased risk of device-related infection and of having a major revision procedure. The rates of major revision surgery after ankle replacement were 9 % at 1 year and 23 % at 5 years compared with 5 % and 11 % following ankle arthrodesis. Patients treated with ankle arthrodesis had a higher rate of subtalar fusion at 5 years post-operatively (2.8 %) than did those treated with ankle replacement (0.7 %). Regression analysis confirmed a significant increase in the risk of major revision surgery (hazard ratio, 1.93 [95 % CI, 1.50 to 2.49]; p < 0.001) but a decreased risk of subtalar fusion (hazard ratio, 0.28 [95 % CI, 0.09 to 0.87]; p = 0.03) in patients treated with ankle replacement compared with those treated with ankle fusion. The authors concluded that this study confirmed that, compared with ankle fusion, ankle replacement is associated with a higher risk of complications but also potential advantages in terms of a decreased risk of the patient requiring subtalar joint fusion. They stated that additional controlled trials are needed to clarify the appropriate indications for ankle arthrodesis and ankle replacement.

Vickerstaff et al (2007) stated that total ankle replacement was first attempted in the early 1970s, but poor early results lead to it being abandoned in favor of arthrodesis. Arthrodesis is not totally satisfactory, often causing further hindfoot arthritis and this has lead to a resurgence of interest in joint replacement. New designs which more closely approximated the natural anatomy of the ankle and associated biomechanics have produced more encouraging results and led to renewed interest in total ankle replacement. Three prostheses dominate the market: the Agility, the Buechel-Pappas and the STAR System, and improving clinical results with these devices have led to more designs appearing on the market. Modern designs of prosthetic ankles almost exclusively consist of 3-part prostheses with a mobile bearing component, similar to the Buechel-Pappas and the STAR System. However, the authors stated that clinical results of these newer designs are limited and short-term and have often been carried out by the designers of the implants.

An assessment of total ankle arthroplasty by the Institute for Clinical Effectivness and Health Policy (Pichon-Rivere, et al., 2007) found that current evidence comes from observational studies, especially at short and medium term, and there is lack of information on the life, stability and rate of complications. The assessment stated that second generation non-cemented and mobile-bearing prostheses have shown promising short term results. "More evidence is required to state clear guidelines for the use of arthroplasty in the different clinical conditions resulting from controlled clinical trials and long term follow up."

Guyer and Richardson (2008) stated that many orthopedic surgeons had abandoned the use of first and second generation total ankle replacement because of unacceptably high complication and failure rates as compared to arthrodesis. Recently, there has been renewed interest in ankle joint replacement as longer term outcome studies have become available. However, the authors noted that there continues to be much debate within the orthopedic community as to indications, patient selection, as well as optimal component design.

A review by Cracchiolo and DeOrio (2008) stated: "Although interest in total ankle replacements is increasing, midterm clinical results to date are few and often have not been validated by independent practitioners. In addition, no level I or II studies have been published." Cracchiolo and Deorio (2008) stated that development of total ankle replacements began nearly 40 years ago.  The initial devices were cemented and highly constrained, and they eventually failed.  These were followed by second-generation cementless ankle implants with a fixed (2-component design) or mobile (3-component design) polyethylene bearing.  Currently, 4 ankle replacements are approved by the FDA.  These four -- Agility, INBONE, Salto-Talaris, and Eclipse -- are 2-component designs; the Scandinavian Total Ankle Replacement (STAR) is a 3-part mobile-bearing design.  The authors concluded that, although interest in total ankle replacements is increasing, mid-term clinical results to date are few and often have not been validated by independent practitioners.  In addition, no level I or II studies have been published.  Therefore, the design rationale for these implants and instruments should be carefully evaluated.

On May 27, 2009, the United States Food and Drug Administration (FDA) approved the STAR System, for arthritic or deformed ankles that may preserve some range of motion in the joint. The new prosthesis is a mobile-bearing device, which relies on bearings that move across a surface of polyethylene, a flexible plastic. This mobile bearing is purported to allow motion with retained congruency. The reported disadvantages of mobile bearing include dislocation, two-sided wear and tear, and fracture. As a condition for approval, the manufacturer is required to gather postmarketing data on the long-term durability of the implant.

The FDA has already cleared several fixed-bearing ankle devices, which are also options to fusion surgery. In fixed-bearing ankle system, the articulating surface is molded, locked or attached to one of its metallic components. As a condition of FDA approval, the company, Small Bone Innovations Inc. (Morrisville, PA), will evaluate the safety and effectiveness of the device during the next 8 years.

Deorio and Easley (2008) stated that recent investigations support the belief that ankle replacement represents an attractive surgical alternative to arthrodesis for patients with advanced ankle arthritis. Although longer follow-up is needed for total ankle arthroplasty (TAA) to displace arthrodesis as the surgical "gold standard", intermediate-term results are encouraging. Indications for TAA include primarily post-traumatic and inflammatory arthritis. Contra-indications to TAA include unresectable osteonecrotic bone, peripheral vascular disease, neuropathy, active and/or recent ankle infection, non-reconstructible ankle ligaments, loss of lower leg muscular control, and severe osteopenia or osteoporosis. Young, active, high-demand patients with ankle arthritis may be better candidates for arthrodesis than for TAA. Rigorous patient selection is essential in the success of TAA, more than in other joint arthroplasty procedures. Total ankle prosthetic designs (the Agility, STAR, Hintegra, Salto, and Buechel-Pappas) with a minimum of published intermediate follow-up results, and several other innovative and biomechanically supported designs (the Mobility Total Ankle System, BOX, INBONE, and Salto-Talaris) were reviewed to demonstrate the recent evolution of TAA. Some TAA designs feature a non-constrained polyethylene meniscus (mobile bearing) that articulates between the porous-coated tibial and talar components. The concern for edge loading (when the polyethylene component comes in contact with a metal edge) has been addressed in more recent designs by reducing the superior polyethylene surface area, expanding the tibial component surface, and even offering a convex tibial component. More practical, effective, and safer instrumentation for implantation has also been developed and has been essential to the success of TAA. However, complications with TAA (such as inadequate wound healing and malleolar fractures) are more frequent when compared with total hip and knee arthroplasty, irrespective of the surgeon's training method. The authors stated that adequate long-term follow-up and high levels of evidence are not available to support universal TAA over arthrodesis in the management of end-stage ankle arthritis. Furthermore, they noted that more research is needed to ascertain the cost-effectiveness of TAA and if conversion of ankle arthrodesis to arthroplasty is advisable.

Chou and associates (2008) stated that TAA was developed to reduce pain and retain motion of the ankle joint in patients with osteoarthritis. The ankle joint has unique, complex anatomic and biomechanical characteristics that must be considered in a successful TAA prosthesis. Initial designs from the 1960s to the 1970s had many failures. Current designs use 2 or 3 components, and recent reports on TAA show consistent good-to-excellent intermediate clinical results, with up to 90 % decreased pain and high patient satisfaction. The follow-up time of these studies is limited, however, and long-term studies with 10- to 15-year follow-ups are needed. In addition, a wide variety of complications has been reported, including osteomyelitis and osteolysis. To limit the number of complications and improve clinical outcome of TAA, careful patient selection and surgeon experience are important.

Wood et al (2008) described the medium-term results of a prospective study of 200 total ankle replacement (TAR) at a single-center using the STAR system. A total of 24 ankles (12 %) have been revised, 20 by fusion and 4 by further replacement and 27 patients (33 ankles) have died. All the surviving patients were seen at a minimum of 5 years after operation. The 5-year survival was 93.3 % (95 % confidence interval (CI) 89.8 to 96.8) and the 10-year survival 80.3 % (95 % CI 71.0 to 89.6). Anterior subluxation of the talus, often seen on the lateral radiograph in osteoarthritic ankles, was corrected and, in most instances, the anatomical alignment was restored by TAR. The orientation of the tibial component, as seen on the lateral radiograph, also affects the position of the talus and if not correct can hold the talus in an abnormal anterior position. Subtalar arthritis may continue to progress after TAR. These findings are similar to those published previously.

Wood and colleagues (2009) reported continuing results of the previously described randomized, prospective study of 200 ankle replacements performed between March 2000 and July 2003 at a single center to compare the Buechel-Pappas (BP) and the STAR implant with a minimum follow-up of 36 months.  The two prostheses were similar in design consisting of 3 components with a meniscal polyethylene bearing, which was highly congruent on its planar tibial surface and on its curved talar surface.  However, the designs were markedly different with respect to the geometry of the articular surface of the talus and its overall shape.  A total of 16 ankles (18 %) was revised, of which 12 were from the BP group and 4 of the STAR group.  The 6-year survivorship of the BP design was 79 % (95 % confidence interval (CI) 63.4 to 88.5 and of the STAR 95 % (95 % CI 87.2 to 98.1).  The difference did not reach statistical significance (p = 0.09).  However, varus or valgus deformity before surgery did have a significant effect (p = 0.02) on survivorship in both groups, with the likelihood of revision being directly proportional to the size of the angular deformity.  These findings supported previous studies, which suggested that total ankle replacement should be undertaken with extreme caution in the presence of marked varus or valgus deformity.

Benedetti et al (2008) stated that most clinical studies on TAR reported assessments based on traditional clinical scores or radiographical analysis. Only a few studies have used modern instrumentation for quantitative functional analysis during the execution of activities of daily living. The aim of this study was to use gait analysis to compare the functional performance of patients who underwent TAR versus a control population. A retrospective analysis was performed of 10 consecutive patients who had undergone meniscal-bearing TAR. Clinical and functional assessments were performed at a mean follow-up of 34 months with a modified Mazur scoring system and state-of-the-art gait analysis. Gait analysis assessment of TAR at medium-term follow-up showed satisfactory results for all patients, with adequate recovery of range of motion. Because the literature reports unsatisfying long-term results, it is important to evaluate these patients over a longer follow-up period. The authors concluded that this study showed that TAR yielded satisfactory, but not outstanding, general functional results at nearly 3 years' follow-up. These gait analysis results highlight the importance of integrating in vivo measurements with the standard clinical assessments of patients who underwent TAR while they perform activities of daily living. These results also emphasized the importance of evaluating the functional outcome of TAR over time.

In a case-series study, Naal et al (2009) evaluated the pre- and post-operative participation in sports and recreational activities of 101 patients at a mean of 3.7 years after TAA. Activity levels were determined with use of the University of California at Los Angeles (UCLA) activity scale. The International Physical Activity Questionnaire (IPAQ) was used to quantify habitual physical activity levels and to calculate the proportion of patients meeting current guidelines for health-enhancing physical activity. The AOFAS hind-foot score was used as the clinical outcome measure. Radiographs were studied for tibial and talar radiolucencies, and any association between radiolucencies, activity levels, and sports participation was determined. Pre-operatively, 62.4 % of the patients were active in sports; 66.3 % were active after surgery (p = 0.56). Patients were active in 3.0 +/- 1.8 different sports and recreational activities pre-operatively and in 3.0 +/- 1.6 activities after surgery (p = 1.0). The sports frequency remained unchanged, with 2.0 +/- 1.6 sessions per week before TAA and 2.3 +/- 1.7 sessions per week post-operatively (p = 0.19). Overall, the patients were active in sports and recreation for 3.9 +/- 3.8 hours per week pre-operatively, and for 4.7 +/- 3.9 hours per week after surgery (p = 0.14). The most common disciplines after TAA were swimming, cycling, and fitness/weight training. Sixty-five percent of the patients stated that surgery had improved their sports ability.  The UCLA activity levels increased significantly from 4.3 +/- 2.2 to 6.2 +/- 1.6 (p < 0.001); AOFAS scores also improved significantly from 45.5 +/- 16.6 to 84.3 +/- 13.3 (p < 0.001). Patients suffering from post-traumatic ankle osteoarthritis were less satisfied with surgery than those with primary or inflammatory ankle osteoarthritis. A total of 79 % of the patients met the current guidelines for health-enhancing physical activity according to the IPAQ. Neither sports participation nor activity levels were associated with the presence of peri-prosthetic radiolucencies. The authors concluded that two-thirds of the patients were active in sports after TAA (but not different from pre-surgery), and the majority of the patients met current health-enhancing physical activity recommendations. The clinical outcome as determined by AOFAS scores and the patient satisfaction were favprable. The present study found no association between sports participation, increased physical activity levels, and the appearance of peri-prosthetic radiolucencies 3.7 years after TAA. However, these results have to be confirmed after longer follow-up, in particular of those patients regularly participating in sports with higher impact.

Karantana and associates (2009) noted that ankle arthroplasty is increasingly used to treat advanced ankle arthritis.  Earlier prostheses have given way to second-generation implants, on which these researchers are accumulating medium-term data. Karantana et al (2009) retrospectively reviewed 45 patients (52 ankles) who had primary TAR using the STAR prosthesis, in order to assess survivorship. The minimum follow-up was 60 months (range of 60 to 110 months). Clinical outcome was determined using the AOFAS score. These investigators determined the rate of radiographical loosening and recorded complications and the need for further surgery. Survival was 90 % (95 % CI 76.8 to 95.5) at 5 years and 84 % (95 % CI 68.9 to 92.2) at 8 years. Six of 52 ankles (11 %) had component revision and 2 were converted to fusion. The mean post-operative AOFAS score was 78. The complication rate was 21 %. Subsequent surgery, excluding component revision, was performed in 9 of 52 (17 %) ankles.

In a manufacturer-funded study, Saltzman et al (2009) reported the results of three separate cohorts of patients: a group of STAR patients and a control group of ankle fusion patients (the Pivotal Study groups) and another group of STAR total ankle patients (the Continued Access group) whose surgery was performed following the completion of enrollment in the Pivotal Study. The Pivotal Study design was a non-inferiority study using ankle fusion as the control. A non-randomized multi-centered design with concurrent fusion controls was used. The initial peri-operative findings up to 24 months following surgery were reported. For an individual patient to be considered an overall success, all of the following criteria needed to be met: (i) a 40-point improvement in total Buechel-Pappas (BP) ankle score, (ii) no device failures, revisions, or removals, (iii) radiographical success, and (iv) no major complications. In the Pivotal Study, 158 ankle replacement and 66 arthrodesis procedures were performed; more than one-fifth of Pivotal Study ankle fusion subjects did not have complete data at 24-month follow-up. In the Continued Access Study, 448 ankle replacements were performed, of which 416 were at minimum 24 months post-surgery at time of the database closure. Of these Continued Access patients, one quarter did not have a full set of BP scale data, and one third did not have a complete set of safety data at the end of follow-up. The total number of reported adverse events at the operative site by 24-month follow-up in the Pivotal Study was more common in the arthroplasty group compared to the fusion group. Major complications and need for secondary surgical intervention were also more common in the Pivotal Study arthroplasty group than the ankle fusion group. Although there was no significat difference in rates of major complications between Pivotal Study arthroplasty group and the Continued Access group, there were half as many secondary procedures performed in the Continued Access group compared with the Pivotal Study arthroplasty group. When the Pivotal groups were compared, the BP scores of pain relief, patient satisfaction, walking and limping were equivalent between fusion and replacement patients; stair climbing was marginally better (p = 0.4) in the Pivotal arthroplasty group; and other BP scores (deformity, function, standing, support, and range of motion) were higher for the Pivotal arthroplasty group. The authors concluded that the hypothesis of non-inferiority of ankle replacement was met for all areas of efficacy evaluated; however, non-inferiority of ankle replacement safety was not met with the initial analysis. The authors explained that a major strength of the study was its prospective design, but a disadvantage was its nonrandomized design, such that arthroplasty and arthrodesis patients were enrolled in different centers, and the groups were somewhat dissimilar. Another weakness noted by the authors is that the BP criteria used as the primary endpoint is not a validated instrument, such that a clinical meaningful change in efficacy as measured by BP criteria is unknown. The BP assigns at 15% credit for ankle motion; thus, a prosthesis that maintains or restores motion is favored by the scale over fusion. The authors point out that, although a higher proportion of STAR patients (58.5%) than fusioin patients (14.9%) were deemed a success based upon a 40-point change in the BP scale, one should not conclude that this defines the true success of surgery, as a similarly high proportion of arthroplasty and fusion patients (greater than or equal to 85%) were indeed pleased and satisfied, and the removal of motion as a criterion of success diminishes any differences seen in the relative efficacy rates. The authors stated that longer-term follow-up is needed to ascertain the durability and functional longevity of the STAR ankle replacement in this cohort. The authors explained that the long-term effects of ankle replacement, including sustained functional benefits, options for revision, and impact on incidence of secondary hindfoot arthritis, were not evaluated in this study.

Gougoulias et al (2009) stated that TAA provides an alternative to arthrodesis for management of ankle arthritis. These researchers conducted a systematic literature search of studies reporting on the outcome of TAA. They included peer-reviewed studies reporting on at least 20 TAAs with currently used implants, with a minimum follow-up of 2 years. The Coleman Methodology Score was used to evaluate the quality of the studies. A total of 13 level IV studies of overall good quality reporting on 1105 TAAs (234 Agility, 344 STAR, 153 Buechel-Pappas, 152 HINTEGRA((R)), 98 Salto, 70 TNK, 54 Mobility) were included. Residual pain was common (range of 27 % to 60 %), superficial wound complications occurred in 0 % to 14.7 %, deep infections occurred in 0 % to 4.6 % of ankles, and ankle function improved after TAA. The overall failure rate was approximately 10 % at 5 years with a wide range (range of 0 % to 32%) between different centers. Superiority of an implant design over another can not be supported by the available data.

Koivu et al (2009) noted that between 2002 and 2008, 130 consecutive ankles were replaced with an hydroxyapatite (HA) and titanium-HA-coated Ankle Evolutive System total ankle prosthesis. Plain radiographs were analyzed by 2 independent observers. Osteolytic lesions were classified by their size and location, with cavities greater than 10 mm in diameter considered to be "marked". Computed tomography scanning was undertaken in all patients with marked osteolysis observed on the plain radiographs. Osteolytic lesions were seen on the plain films in 48 (37 %) and marked lesions in 27 (21 %) ankles. The risk for osteolysis was found to be 3.1 (95 % CI 1.6 to 5.9) times higher with implants with Ti-HA porous coating. The authors concluded that care should be taken with ankle arthroplasty until more is known about the reasons for these severe osteolyses.

Yalamanchili et al (2009) stated that TAA is an evolving area of modern orthopedics that is gaining renewed interest after early failures. Implant design has improved with a greater understanding of the complex biomechanics of the ankle joint. Modern ankle prostheses consist of 3 components, including either a fixed or mobile polyethylene-bearing. Only a handful of implants are FDA-cleared for use in the United States, and the experience with some of these implants is limited. Although it is difficult to draw a consensus from the limited studies available, the trend has been towards lower complications and failures than with early implants. Also, multiple recent studies purport better gait and function with TAA. Equivalence with ankle arthrodesis has been suggested but has yet to be conclusively proven. Despite this renewed enthusiasm, surgeons should be aware that complications still exist and can be devastating even in experienced hands. Currently, ankle arthroplasty appears to be a viable alternative to ankle arthrodesis in selected patients. They also noted that although recent studies have been promising, there still is a need for long-term outcomes data and randomized controlled trials. The ultimate role for ankle arthroplasty has yet to be defined.