Supination adduction ankle fractures: Ankle fracture or pilon variant?

Supination adduction (SAD) fractures are rotational ankle fractures with a characteristic vertical medial malleolus fracture and tension failure fibula fracture. While these fractures are considered rotational injuries, they can have joint impaction that could lead to early joint degeneration. The purpose of this study was to characterize SAD ankle fractures and compare these injuries with partial articular pilon fractures.

Following IRB approval, we retrospectively reviewed ankle and pilon fractures (OTA 43 & 44) treated at two academic level-1 trauma centers from 2008-2016. Our primary outcome was failure defined as either ankle arthrodesis or arthroplasty. Infection and significant arthrosis were also compared. We performed multivariate Cox regression to compare failure between SAD ankles and pilon fractures.

Seventy-nine SAD ankle and 91 pilon fractures met inclusion criteria. Patient demographics including age and open injury did not differ between groups. For SAD ankle fractures, impaction occurred in 66% (44/79) of injuries. Impaction failed to be significant risk factor for arthrosis after adjustment for malreduction (p = 0.13). Failure was significantly more common in pilon fractures (11/91, 12%) than SAD fractures (5/79, 6%) (HR=0.25, 95% CI:[0.07,0.92], p = 0.036). Infection and arthrosis rates failed to show a difference between the groups (p = 0.19, 0.63, respectively). Malreduction was significantly associated with joint arthrosis (OR=7.05, 95% CI: [1.63,36.12], p = 0.01).

Rotational ankle fractures have low rates (<2%) of ankle arthrodesis or arthroplasty. The present study demonstrates that SAD ankles have failure (6%) that remains somewhere between rotational ankle fractures and pilon fractures (12%) on the ankle injury spectrum.

Level 3, Prognostic.