Short-Term Outcomes of Supination External Rotation IV Bimalleolar and Deltoid Variant Fractures with No Deltoid Repair.

Abstract

To evaluate whether radiographic and clinical outcomes differ between supination-external rotation (SER) type IV bimalleolar fractures and deltoid ligament injuries treated without deltoid repair. A secondary aim was to compare outcomes between universal tubular and fibula-specific plates for fibular fixation. Design: Retrospective cohort study. Academic medical center. Skeletally mature patients with SER-IV (AO/OTA 44-B2) ankle fractures (either bimalleolar or deltoid ligament injury without medial malleolar fracture) treated between November 2011 and July 2024. Exclusions: pathologic/pilon fractures, congenital deformity, nonunion repair, posterior malleolar fixation, or <3 months of follow-up. Secondary comparison included rotational ankle fractures (SER, Pronation External Rotation/PER) stabilized with tubular or fibula-specific plates. Radiographic outcomes included medial clear space (MCS), superior clear space (SCS), tibiofibular clear space (TFCS), talocrural angle, and Takakura score. Clinical outcomes included complication rates, secondary surgeries, infections, and conversions to arthroplasty. Comparisons were made between intra-operative and final post-operative radiographic measurements. A total of 132 patients with SER-IV fracture were included in the primary study arm , with 89 in the bimalleolar (BM) group and 43 in the deltoid-variant (DV) group. Demographics were similar between cohorts, including age (BM: 49.5 ± 19.2 vs. DV: 46.0 ± 15.4 years, p = 0.25), BMI (BM 28.8 kg/m2 ± 5.4 vs. DV 31.1 kg/m2 ± 9.4, p = 0.16), diabetes (BM 11.2% vs DV 2.3%, p = 0.16), smoking (BM 9.0% vs DV 9.3%, p = 1.0), Charlson Comorbidity Index (CCI) (BM 1.8 ± 2.4 vs DV 1.2 ± 1.8, p = 0.09), and American Society of Anesthesiologists' (ASA) score (BM 1.9 ± 0.8 vs DV 1.8 ± 0.7, p = 0.93). Changes in radiographic alignment between intra-operative and final post-operative measurements were comparable between groups, including MCS (BM: 0.3 ± 0.7 mm vs. DV: -0.5 ± 0.9 mm, p = 0.097), SCS (BM: -0.5 ± 0.9 mm vs. DV: -0.7 ± 0.7 mm, p = 0.112), and TFCS (BM: 0.0 ± 1.2 mm vs. DV: 0.2 ± 1.5 mm, p = 0.887). A total of 342 patients with rotational ankle fractures were included in our second study arm, with 282 in the tubular (TB) group and 60 in the fibula-specific (FS) group. Demographics were comparable between cohorts, including age (TB 47.5 ± 19.5 vs. FS 47.0 ± 17.7, p = 0.85), BMI (TB 29.5 ± 6.6 vs FS 29.3 ± 7.9, p = 0.86), diabetes (TB 13.1% vs FS 10.0%, p = 0.65), smoking (TB 8.9% vs FS 15.0%, p = 0.23), CCI (TB 1.7 ± 2.3 vs FS 1.6 ± 1.9, p = 0.72), and ASA (TB 1.9 ± 0.7 vs FS 1.9 ± 0.7, p = 1.00). Changes in radiographic alignment differed between groups; however, these changes were not clinically significant. This included MCS (TB: -0.2 mm vs. BS: -0.7 mm, p = 0.0047), SCS (TB: -0.6 mm vs BS: -1.3 mm, p = 0.0002), and TFCS (TB: + 0.5 mm vs BS: -0.5 mp = 0.0065). Patients with bimalleolar-equivalent injuries treated with fibular fixation alone demonstrated outcomes comparable to those with bimalleolar fractures treated with fibular and/or medial malleolar fixation. In lateral malleolus fractures with medial deltoid injury, deltoid repair had not appeared necessary to restore normal alignment and radiographic outcomes. Fibula-specific and tubular plates both maintained alignment. IV.