[Long-term behavior of ankle fusion: assessment of the same series at 7 and 23 year (19-36 years) follow-up].

PURPOSE OF THE STUDY: Theoretically, long-term functional and radiographic degradation is predictable after ankle fusion, but sound evidence from the consecutive analysis of the same cohort is lacking. The purpose of this study was to check the hypothesis by repeating assessment in the same cohort of patients who underwent ankle fusion.

MATERIAL AND METHODS: The cohort included 52 ankle fusions which had been analyzed in 1984 at seven years (range 2-22 years) follow-up then again in 2000 using the same evaluation criteria. Among the 52 patients, six were lost to follow-up (11.5%) 20 had died (38.4%) and one had undergone leg amputation. The second analysis thus included 25 patients (48%). The comparison cohort thus included 25 patients (18 men and 7 women), mean age 62+/-12.6 years (range 40-94) at the 2000 assessment performed 23+/-4.5 years (range 19-36 years) after the fusion. Functional outcome was assessed with the 100-point Duquennoy scale. Osteoarthritis of the subtalar and mediotarsal joints were assessed preoperatively and at follow-up using the same scale.

RESULTS: The functional outcome did not deteriorate significantly between 1984 and 2000. The mean score was 65.8+/-22.6 (range 19-92) in 1984 and 64.7+/-18.3 (range 34-90) in 2000 (p=0.67). Fifteen patients (60%) had a good or very good outcome at seven years, and 14 (56%) at 23 years. Between 1984 and 2000, ten patients improved their score (on average 10.4 points, range 1-21 points), two had an unchanged score and thirteen a lower score (on average 10 points, range -1 to -24). Ten of these thirteen patients developed severe intercurrent conditions (neurological or cardiac) explaining the degradation. At last follow-up, sixteen ankles were pain free or nearly pain free. Twelve patients considered their ankle as a forgotten problem (VAS 10) and had no regrets concerning the operation. The evolution of the subtalar joint in 16 cases (nine fusions including five at the same time as the ankle fusion and four performed within four years) showed that all developed osteoarthrtic degradation early with aggravation between 1984 and 2000, leading in the majority of cases to severe degenerative disease. This osteoarthritis was painful in less than one-third of the cases (including the four secondary subtalar fusions and the four subtalar fusions which were painful at mobilization). Twenty-three mediotarsal joints were analyzed (two fusions four years after ankle fusion). The degradation was later and less severe than for the subtalar joint with a majority showing moderate osteoarthritis. Ten ankles exhibited compensatory hypermobility of the forefoot measured at more than 15 degrees without pain.

DISCUSSION: This long-term follow-up with two successive assessments using the same evaluation criteria did not demonstrated the late degradation of function expected after ankle fusion. It did show however the presence of undeniable radiographic degradation of the subtalar joint but with little or no severe clinical expression at a minimal follow-up of 19 years. There was no need for complementary fusion between 4 and 23 years follow-up.