Short- and mid-term results with the STAR total ankle prosthesis

We evaluated the short- to mid-term results of an unconstrained total ankle prosthesis (S. T. A. R.) with uncemented fixation. Fifty consecutive ankle replacements were performed in 48 patients between 1996 and 1999. The init ial diagnosis was posttraumatic osteoarthrosis in 31 cases (62 %), primary osteoarthrosis in 8 cases (16 %), and systemic joint affection in 11 cases (22 %), e. g. rheumatoid arthritis (6 cases), hemochromatosis (2 cases), ps oriasis arthritis (1 case), lupus erythematodes (1 case), and sclerodermia (1 case). There were two perioperative complications: one superficial wound dehiscence that healed uneventfully, and one injury to the dorsal foot art ery that necessitated primary reconstruction. Seven revisions, all in cases of posttraumatic arthrosis, were necessary: local revision of the fibula f or painful lateral impingement (3 cases), posteromedial soft tissue revisio n for painful restriction of dorsiflexion (2 cases), percutaneous lengtheni ng of the Achilles tendon (1 case), and osteotomy and callus distraction fo r angular correction after stress fracture of the distal tibia (1 case). At the last follow-up control, 21 patients (62 %) were very satisfied, 10 pat ients (29 %) were satisfied, and 3 patients (9 %) were satisfied with reser vations. The obtained range of motion was 30 degrees (range, 15 to 55 degre es), with a maximal plantar-flexion of 25 degrees (range, 15 to 45 degrees) and dorsiflexion of 5 degrees (-3 to 20 degrees). When the AOFAS-Hindfoot- Score was applied, the 34 patients scored 84.1 points (range, 44 to 100 poi nts). After settling of the implants within 6 weeks, no migration was noted in any case, and all implants were considered to be stable. The favorable results were considered to be a result of the mechanical properties of the S. T. A. R. total ankle prosthesis that allows for unconstrained motion of the polyethylene inlay on the tibial component, e, g. anteroposterior trans lation, mediolateral translation and axial rotation. The success of implant ation may depend on exact technique, correct hindfoot alignement, sufficien t capsuloligamentous stability of the ankle, and a solid bane stock. Althou gh our first results are very encouraging, a longer follow-up is mandatory to answer the question whether ankle replacement is a viable alternative to ankle arthrodesis.