Rates of subtalar joint osteoarthritis after modified Chrisman-snook

Ankle sprains commonly damage the lateral compartment of the tibiotalar and subtalar joint. The presence of functional or mechanical instability leads to long term dysfunction of patients due to ankle laxity. The gold standard surgical procedure for chronic ankle instability is repair of the anterior talofibular and/or calcaneofibular ligaments with imbrication of the inferior extensor retinaculum. The senior author's indications for a modified Brostrom versus a modified Chrisman-Snook (CS) have evolved over the past decade. A potential complication with any technique that crosses the subtalar joint to reconstruct the CFL is progression of subtalar joint osteoarthritis. Consecutive cases of a near-anatomic Chrisman-Snook procedure with semitendinosus allograft were reviewed to identify any worsening of subtalar joint arthrosis. Fifty-six cases met inclusion and exclusion criteria. Patient demographics demonstrated a mean age of 47.5 years (SE ± 0.31), mean BMI 29.8 (SE ± 0.17), 21.4 % with concomitant calcaneal osteotomy, and 19.6 % revision cases after a prior failed ligament repair. Mean follow up was 16.5 months. Overall complication rate was 10.7 % (n = 6) with one patient requiring revision via successful subtalar joint fusion. Mean Kellgren-Lawrence stage increased from 0.56 to 0.81 (SE ± 0.2, p = 0.0621). The mild increase in severity of subtalar joint osteoarthritis did not reach clinical significance. However, more surveillance is needed mid-term to long-term to understand if the increase is transient, permanent, or subject to continued progression.