Abstract
BACKGROUND: Atypical triplane fractures (ATFs) defined as a triplane fracture that did not involve the weight-bearing articulating surface or as an extra-articular triplane fracture. ATFs are scarcely reported and the incidence may be underestimated. Moreover, there is no consensus on treatment. This study aimed to evaluate ATFs incidence, fracture pattern, and treatment outcome, and propose treatment recommendations. METHODS: Twenty-five ATFs of 46 triplane fractures were retrospectively reviewed between 2011 and 2017. ATFs were classified according to the modified ATF classification. Treatment methods were analyzed. Radiologic outcomes were measured based on fracture displacement. Clinical outcomes included the American Orthopedic Foot and Ankle Society score, visual analogue scale, ankle range of motion, and complications at final follow-up period. RESULTS: A total of 11 type IV, 11 type III, and three type II ATFs were identified. All type II ATFs (intra-articular fracture) were treated with operative treatment. Nine patients were treated with operative treatment and 18 patients were treated with non-operative treatment in type III or IV ATFs (extra-articular fracture). Good radiologic and clinical outcomes were observed in all patients. The residual displacement after initial trial of closed reduction was between 4 and 5 mm in ten cases of type III or IV ATFs; however, no complications were observed, and all cases had good clinical results after non-operative treatment. CONCLUSIONS: ATFs may be under-recognized. Operative treatment and non-operative treatment showed good outcome. Non-operative closed reduction and cast immobilization can be recommended for extra-articular ATF with displacement < 4 mm. LEVEL OF EVIDENCE: Level IV, case series.