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The effect of three-component total ankle replacement malalignment on clinical outcome: pain relief and functional outcome in 317 consecutive patients.

BACKGROUND
Total ankle replacement has become an increasingly popular treatment for patients with end-stage ankle osteoarthritis. The surgery is technically demanding and generally performed by only experienced foot and ankle surgeons. An important complication of total ankle replacement is malposition of the talar component. The biomechanical effect of malposition has been reported; however, the functional outcomes of patients with varying degrees of talar component malposition have not. The purpose of this study was to assess the influence of talar component malposition on postoperative pain relief and functional outcome.


METHODS
This retrospective cohort study included 317 total ankle replacements in 317 patients. The anteroposterior offset ratio was measured with use of lateral ankle radiographs made with the patient in a standing, weight-bearing position. Patients were classified into one of three groups: those with an anteroposterior offset ratio of 0 (127 ankles), those with a ratio of >0 (103 ankles), and those with a ratio of <0 (eighty-seven ankles). Postoperative pain relief was assessed with use of a visual analogue scale. Functional outcome was assessed with the American Orthopaedic Foot & Ankle Society (AOFAS) hindfoot score and measurement of ankle range of motion. The mean duration of follow-up (and standard deviation) was 53.2 ± 18.4 months (range, twenty-four to ninety-eight months).


RESULTS
The postoperative pain level in the group with an anteroposterior offset ratio of 0 was significantly lower than that for both the group with a ratio of >0 (p < 0.001) and the group with a ratio of <0 (p = 0.017). Also, the functional outcome, measured with use of the AOFAS hindfoot score, was significantly higher, and ankle motion was significantly greater, in the group with an anteroposterior offset ratio of 0 than in the group with a ratio of >0 (p = 0.003 and p < 0.001, respectively) and the group with a ratio of <0 (p = 0.007 and p = 0.080).


CONCLUSIONS
The anteroposterior offset ratio may be a useful predictor of outcome in patients with total ankle replacement with regard to both pain and function.


LEVEL OF EVIDENCE
Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.