Subtalar joint nonunions following isolated ipsilateral ankle arthrodesis a systematic review and meta analysis

Open arthrodesis remains the gold standard for management of end stage subtalar joint arthritis. Rate of isolated subtalar fusion complicated by nonunion has been documented between 4-22.8 %. However, little is known about success of subtalar joint fusion when performed underneath a previously constructed ankle arthrodesis. The aim of this systematic review was to assess the cases of nonunion in patients who underwent a subtalar joint fusion with documented history of previous ipsilateral ankle fusion. A broad literature search was performed through PubMed, Google Scholar, and Cochrane Database using the following search terms: "Time to fusion, ankle fusion complication, outcomes ankle fusion." Meta-regression was performed to assess the effects of study sample size and publication year on the non-union rate. Three studies met inclusion and exclusion criteria. The non-union rates of subtalar joint arthrodesis following ankle fusion in the included studies ranged from 20 % to 55.6 %. The pooled rate was 38 % (95 % CI: 18.2 % to 59.8 %). Our series included a larger number of cases, allowing statistical analysis that clearly demonstrated a markedly lower subtalar fusion rate in patients with previous ipsilateral ankle fusion when compared to what has been documented in the literature.