Comparison of Supination-Adduction Type 2 and Supination-External Rotation Type 4 in Bimalleolar Ankle Fractures: Does Partial Pylon Variant of Supination-Adduction Type Fracture Affect Functional Outcomes?

BACKGROUND

Supination-adduction (SAD) type injuries are pylon variant injuries and lie between partial intra-articular pylon fractures and rotational ankle fractures. We aimed to evaluate functional outcomes of SAD type 2 bimalleolar fractures in comparison to supination-external rotation (SER) type 4 fractures.

METHODS

We retrospectively reviewed data of 42 cases with SER type 4 and 20 cases with SAD type 2 injuries. Patients with a history of rheumatic disease, open fractures, pathologic fractures, nonbimalleolar fractures, neuropathic disease, and talus osteochondral lesion, and those operated on after greater than 72 hours because of skin lesion or managed with a two-stage surgical protocol after external fixation, were not included in the study. We compared these two groups in terms of the mean age, follow-up time, visual analog scale pain and American Orthopedic Foot and Ankle Society scores, Kellgren-Lawrence arthrosis classification, union time, and complications.

RESULTS

The groups did not differ in terms of mean age (P = .115) and sex (P = .573). There was no significant difference in terms of union time between the groups (P = .686). American Orthopedic Foot and Ankle Society score was significantly higher in the SER group (91.2 ± 9.9) than in the SAD group (86.1 ± 13.2; P = .034). Visual analog scale pain scores were similar in the SAD (0.3 ± 0.92) and the SER (0.26 ± 0.7) groups (P = .897).

CONCLUSIONS

Supination-adduction bimalleolar fractures may have worse functional outcomes in the intermediate term than do SER bimalleolar fractures, implying pylon variant fractures as a mechanism of injury. Supination-adduction bimalleolar fractures might be associated with a high rate of intra-articular cartilage impaction, resulting in varus deformity after surgery.