AES Total Ankle Replacement
The Ankle Evolutive System (AES) TAR is a further development of the Buechel-Pappas-type prosthesis. This design has a modular stem and allows hemi-replacement of the medial tibiotalar and talofibular joints.1 This prosthesis type has been widely used in England and France 2,3 and has also been introduced in Norway.4 While some studies show promising functional results, this prosthesis has experienced significant problems relating to osteolysis and has been withdrawn from the market.17
One of the first reports addressing the outcome in patients who underwent AES TAR is a study by Patsalis.5 This study included 15 AES TAR patients with an average short-term follow up of 8.5 months. Three malleolar fractures were observed intraoperatively. Two replaced ankles had to be revised, while the remaining 13 patients showed significant functional improvement as assessed by the AOFAS score.5
In 2005, a short-term study by the designers of the AES prosthesis outlined the suggested surgical technique and reported good preliminary results.6
Henricson and Ågren addressed the influence of preoperative hindfoot alignment on secondary surgery after TAR.7 The patient cohort included 109 STAR, 62 Buechel-Pappas, and 22 AES TARs. The mean follow-up time in the whole patient group was 4.2 years.Two cases with instability requiring additional surgery (one case with preoperative varus and one case with preoperative valgus deformity) were observed in the AES TAR group. No revision surgeries addressing prosthesis loosening were necessary.7
Brooke et al presented two cases with valgus malalignment following TAR using an AES prosthesis.8 They performed a fibula lengthening osteotomy to regain the anatomical alignment and to avoid pathological increases in wear. In both cases, good clinical and radiographic results were achieved.8 Kharwadkar and Harris published a report of two cases using the AES tibial component as a revision component in patients with failed STAR prostheses.9 The hybrid AES-STAR revision procedures were performed at 4 and 7 years following the primary STAR prosthesis implantation. The mid-term results were satisfactory, with no restriction of daily activities.9
Dahabreh et al published a case report with a patient having revision surgery due to extrusion of a metal radiological marker.10 The exchange of polyethylene insert was performed 9 months after the initial TAR using an AES implant. During revision surgery, the insert was found to be intact without fracture.10 Morgan et al presented 2.5 years' follow-up results in a female patient who had poliomyelitis as a child and had been treated with the AES prosthesis because of a painful, degenerate ankle with preoperatively significant varus deformity.11 The patient showed a satisfactory functional outcome with a well-aligned replacement ankle and no evidence of loosening or osteolysis around prosthesis components.11
Anders et al reported their mid-term results in 94 patients who underwent AES TAR between 2002 and 2007.12 One patient was deceased, leaving 93 ankles for evaluation at a mean follow up of 3.5 years. There were five intraoperative malleolar fractures, which were all secured with screws. One patient was revised after 5.5 years due to loosening of both metallic components, and two patients with loosening of the tibial component were pending revisions. In an additional three cases osteolysis, around the component was seen. Two ankles were revised due to fixed varus or valgus deformity. In one patient, an ankle fusion was performed because of a fracture of the distal tibia. Two patients were revised for deep infection. Overall, the cumulative 5-year survivorship with revision for any reason was 90%. In summary, the authors stated that mid-term results in their patient cohort were promising.12
Morgan et al presented the outcomes of 38 consecutive patients who were treated with AES TAR between 2002 and 2004.13 All patients were reviewed clinically and radiographically at a minimum follow up of 4 years. Most patients presented with significantly improved function and pain relief. Two replaced ankles were converted to ankle fusion resulting in a cumulative 6-year survivorship of 94.7% (95% CI, 80.3% - 98.7%). Ten patients presented with edge-loading, of whom nine had corrective surgery. In nine patients significant osteolysis around the prosthesis components was seen. Because of non-progressive symptoms no further revision surgeries were suggested.
Despite high patient satisfaction, the authors reported some concerns about an observed high rate of osteolysis.13 The reported high rate of osteolysis in patients who underwent AES TAR has been confirmed by other studies. Besse et al reported mid-term results of their prospective study including 51 AES implants performed from 2003 to 2006.14 All patients were reviewed at a mean follow-up of 40 months. Eighty-two percent of all patients had good functional outcome showing a significant postoperative improvement of AOFAS score. In two patients, replaced ankles were converted to ankle fusion because of talar component subsidence and mechanical dislocation. Although the functional outcome and patient satisfaction were comparable to other results published in studies using other third generation prostheses, significant osteolysis with the AES TAR was more frequent with risk of subsidence. As a consequence, the authors stopped implantation of this prosthesis type and recommended a preventive grafting for severe osteolysis.14
The comparably high osteolysis rate was also seen in a study by Koivu et al reviewing 130 consecutive AES implants performed between 2002 and 2008.15 Radiolucent lines or osteolytic lesions were seen on plain radiographs in 48 ankles (37%). Marked osteolytic lesions were found in 27 ankles (21%). The talar component migrated in nine ankles; in an additional two ankles, a shift of the tibial component was observed. Of the 27 ankles with marked osteolysis, 16 underwent revision surgery resulting in a revision rate of 15.5%. The contents of the osteolysis cavities were used for microbiological and histological analysis. The histological findings were interpreted as a foreign-body reaction. The authors concluded that the use of AES implants should be avoided until the reason and extent for the problem of osteolysis has been solved.15 Rodriguez et al observed a high frequency of delayed appearance of osteolysis (77%) in 18 ankles replaced with AES prosthesis at the mean follow-up of 39.4 months.16
In summary, recent studies of the AES TAR reported a high rate of osteolytic lesions.13-16 It is still unclear whether the osteolysis process is a result of failure of the hydroxyapatite coating of the metal components or failure of the mobile bearing. As a result of independently published results showing high osteolysis rate, the AES prosthesis has been withdrawn from the market.17
- Hintermann,B.: Current designs of total ankle prostheses, in Hintermann,B. (ed), Total ankle arthroplasty. Historical overview, current concepts and future perspectives. Wien , Springer, 2004, pp. 69-100.
- Goldberg,A.J., Sharp,R.J., and Cooke,P.: Ankle replacement: current practice of foot & ankle surgeons in the United kingdom. Foot Ankle Int, 30:950-954, 2009.
- Besse,J.L., Colombier,J.A., Asencio,J., Bonnin,M., Gaudot,F., Jarde,O., Judet,T., Maestro,M., Lemrijse,T., Leonardi,C., and Toullec,E.: Total ankle arthroplasty in France. Orthop Traumatol Surg Res, 96:291-303, 2010.
- Fevang,B.T., Lie,S.A., Havelin,L.I., Brun,J.G., Skredderstuen,A., and Furnes,O.: 257 ankle arthroplasties performed in Norway between 1994 and 2005. Acta Orthop, 78:575-583, 2007.
- Patsalis,T.: Die AES-Sprunggelenksprothese: Indikation, Technik und erste Ergebnisse. Fuss Sprungg, 2:38-44, 2004.
- Asencio,J. and Leonardi,C.: Ankle Evolutive System prosthesis: a simple, accurate, and reliable specific concept for primary and revision surgery. Tech Foot & Ankle, 4:119-124, 2005.
- Henricson,A. and Agren,P.H.: Secondary surgery after total ankle replacement. The influence of preoperative hindfoot alignment. Foot Ankle Surg, 13:41-44, 2007.
- Brooke,B.T., Harris,N.J., and Morgan,S.S.: Fibula lengthening osteotomy to correct valgus mal-alignment following total ankle arthrplasty. Foot Ankle Surg,epub ahead of print, 2009.
- Kharwadkar,N. and Harris,N.J.: Revision of STAR total ankle replacement to hybrid AES-STAR total ankle replacement-a report of two cases. Foot Ankle Surg, 15:101-105, 2009.
- Dahabreh,Z., Gonsalves,S., Monkhouse,R., and Harris,N.J.: Extrusion of metal radiological marker from a total ankle replacement insert: a case report. J Foot Ankle Surg, 45:185-189, 2006.
- Morgan,S.S., Brooke,B., and Harris,N.J.: Is there a role for total ankle replacement in polio patients?: A case report and review of the literature. Foot Ankle Surg,epub ahead of print, 2009.
- Anders,H., Kaj,K., Johan,J., and Urban,R.: The AES total ankle replacement: A mid-term analysis of 93 cases. Foot Ankle Surg, 16:61-64, 2010.
- Morgan,S.S., Brooke,B., and Harris,N.J.: Total ankle replacement by the Ankle Evolution System: medium-term outcome. J Bone Joint Surg Br, 92:61-65, 2010.
- Besse,J.L., Brito,N., and Lienhart,C.: Clinical evaluation and radiographic assessment of bone lysis of the AES total ankle replacement. Foot Ankle Int, 30:964-975, 2009.
- Koivu,H., Kohonen,I., Sipola,E., Alanen,K., Vahlberg,T., and Tiusanen,H.: Severe periprosthetic osteolytic lesions after the Ankle Evolutive System total ankle replacement. J Bone Joint Surg Br, 91:907-914, 2009.
- Rodriguez,D., Bevernage,B.D., Maldague,P., Deleu,P.A., Tribak,K., and Leemrijse,T.: Medium term follow-up of the AES ankle prosthesis: High rate of asymptomatic osteolysis. Foot Ankle Surg, 16:54-60, 2010.
- Smith,T.W. and Stephens,M.: Ankle arthroplasty. Foot Ankle Surg, 16:53, 2010.