Can a Three-Component Prosthesis be Used for Conversion of Painful Ankle Arthrodesis to Total Ankle Replacement?

backgroundIn patients with painful ankle arthrodesis, the surgical treatment is challenging, and may include takedown of ankle arthrodesis and conversion to a total ankle replacement (TAR). This procedure is technically demanding given the altered anatomy after arthrodesis. Few studies have evaluated TAR in the setting of prior arthrodesis. QUESTIONS/PURPOSES: (1) What intraoperative and perioperative complications were observed in patients who underwent conversion of an ankle arthrodesis to a TAR? (2) Was durable fixation achieved at short term, and what was the alignment of the components? (3) What subsequent surgical procedures were performed, including revisions? (4) What improvements were observed in pain, tibiotalar range of motion (ROM), and quality of life?

methodsBetween January 2007 and December 2014, 18 patients with a painful ankle arthrodesis underwent conversion to TAR at our tertiary referral center. During this period, the indications for conversion of ankle arthrodesis to TAR were tibiotalar nonunion or malunion after attempted arthrodesis in patients who declined revision ankle arthrodesis. The goal of revision surgery was to help patients regain hindfoot mobility and to decrease pain. During the study period, all patients who met indications were treated with a conversion procedure. Of the 18 patients included, 14 were men and four were women. The mean age of the patients was 51 ± 7 years. The mean followup was 54 ± 27 months, with no loss to follow up observed. The initial ankle arthrodesis was performed 6 ± 3.5 years before conversion to TAR. In all patients, the conversion to TAR was performed using a nonconstrained cementless three-component prosthesis. Intraoperative and postoperative complications, revision procedures, and prosthesis component loosening were evaluated. Weightbearing radiographs were used to determine the angular alignment of the tibial and talar components using α/β/γ angles and to analyze the bone-implant interface. Osseointegration was defined as visible trabecular structures at the bone-implant interface without radiolucent lines. The criteria for radiographic loosening was defined as subsidence or migration of prosthesis components and/or a cystic lesion with a diameter at least 2 mm. Clinical assessment included pain evaluation, measurement of ankle ROM, and quality of life.

resultsTwo of the 18 patients sustained an intraoperative medial malleolar fracture. In three patients, delayed wound healing was observed. At latest followup, four patients had incomplete osseointegration (posterior quarter of the bone-prosthesis interface on the tibial side). None of the 18 patients had prosthesis loosening. In all patients, both components were neutrally aligned. Two patients had painful arthrofibrosis with reduced ROM, which we treated with an open arthrolysis and exchange of mobile-bearing inlay; one other patient is considering a revision for substantial tibial component medial tilt with collapse of the medial arch. At the latest followup, the mean dorsiflexion and plantar flexion were 8.5° ± 3° and 15° ± 5°, respectively. The mean visual analog scale (VAS) score decreased from 9 ± 0.8 to 1.7 ± 1.6 (p < 0.001). The Short Form Health Survey questionnaire (SF-36) physical and mental outcome scores improved from 34 ± 5 to 74 ± 11 (p < 0.001) and from 49 ± 4 to 75.5 ± 7 (p < 0.001).

conclusionsConversion of an ankle arthrodesis to a TAR is a technically challenging procedure. In this small series, it was associated with frequent complications including arthrofibrosis, and functional outcomes including postoperative ROM were lower than reported for primary TAR. However, pain and function did improve. Further studies are necessary to address long-term clinical and radiographic outcomes in this patient cohort. LEVEL OF EVIDENCE: Level IV, therapeutic study.