Dedicated locking plate reduces non-union risk in open ankle fusion in obese patients.

INTRODUCTION: Obesity is a growing public health concern. In ankle osteoarthritis, non-conservative treatment in advanced stages consists in ankle fusion, or else total ankle replacement, for which obesity is a relative contraindication. One of main complications of ankle fusion is non-union. Devascularization, obesity and fixation material are all factors involved in postoperative non-union, and have to be taken into account in surgical strategy for reliable results. The objective of this study was to compare the rate of ankle non-union in obese patients using quadruple screwing or a dedicated locking plate. The hypothesis was that the locking plate limits the risk of non-union in this population.

METHODS: All patients were obese (BMI > 30kg/m²) and presented ankle osteoarthritis with > 10° intra-articular deformity. The approach and joint preparation were performed via an anteromedial approach. Group S was composed of 32 patients, operated on by quadruple screwing; group P comprised 10 patients operated on using a dedicated locking plate. The main endpoint was a significant difference in the rate of non-union between the 2 groups. The secondary endpoint was improvement in pre- and 6-month post-operative AOFAS score.

RESULTS: Group S presented 31% non-union (10/32) and group P 0% (0/10) (p<0.05). Postoperative AOFAS score was significantly higher in group P: 67.8 ± 10.4 [range, 40 - 92] vs 83.1 ± 8.0 [range, 64 - 92] (p<0.05).

CONCLUSION: The dedicated anterior locking plate is a technique of choice for ankle fusion in obese patients with intra-articular deformity > 10°, to limit the risk of non-union.

LEVEL OF EVIDENCE: IV; retrospective study.