Fusion of the subtalar joint for post-traumatic arthrosis: a study of functional outcomes and non-unions.

BACKGROUND: The aim of this prospective cohort study was to quantify the rate of non-unions after arthrodesis of the subtalar joint, to identify risk factors and to evaluate the functional outcome.

METHODS: Patients with subtalar fusion from 2000 to 2013 and pre-existing post-traumatic osteoarthritis of the subtalar joint were analysed for risk factors like revision surgery, infection history in the area of operation, obesity, diabetes, cigarette smoking and alcohol abuse. The osseous consolidation was proven by x-ray or CT-scan and clinical aspects, e.g. consistent pain or functional disorders. The outcome was measured using the AOFAS hindfoot score, the SF-36 score and additionally by the visual analog scale. This study included 214 patients with 267 operations (n = 214, age 49 ± 12 years, 83% men); 59% of the cases had a calcanear fracture (n = 126).

RESULTS: Non-unions were substantially high with 23.8%, including all risk factors whereas the non-union rate without any risk factors was only 12%. Considering revision surgery, there were no remarkable differences in the rate of non-union. Infections showed an odds ratio for non-union of 4.33 compared to patients without any risk factors. The AOFAS hindfoot score showed 49 ± 20 after primary arthrodesis and 46 ± 17 after secondary arthrodesis.

CONCLUSION: Failure of subtalar fusion after post-traumatic osteoarthritis is attributable to various examined risk factors. The presence of an infection was stated as a major negative predictive factor for osseous consolidation. Especially the summation of risk factors increases the chance for non-union.

LEVEL OF EVIDENCE: Level II Prospective Comparative Study.