Detection of fibular torsional deformities after surgery for ankle fractures with a novel CT method

Background: Substantial fibular torsional deformities were detected after surgery for ankle fractures combined with a lesion of the syndesmotic complex using a novel CT analyzing method. Methods: In a prospective study, 61 patients with ankle fracture dislocations were treated with trans-syndesmotic screw fixation of the distal tibiofibular joint. Postoperative axial CT scans of both lower legs under standardized leg positioning conditions were made and analyzed with three different methods. Method 1 (M1) used proximal and distal CT planes of the lower leg for detection of the fibular torsional angle, method 2 (M2) considered only the angle at the distal tibiofibular joint, and method 3 (M3) measured the angles between the fibular and tibial tangents at the distal tibiofibular joint. Twenty patients with fibular torsional asymmetries of more than 10 degrees were evaluated clinically 6 to 34 months postoperatively with the American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Score. Results: Thirty-five of the 61 patients had torsional side-to-side differences of more than 10 degrees. M1 and M2 showed statistically significant differences compared to M3 (p = 0.001). Validity was controlled by interobserver data, variation coefficients were low for M1 and M2. Clinically, six of 20 patients with torsional differences of more than 10 degrees had excellent results, while seven had good results and seven bad moderately functional results. Six of the seven with moderate results had fibular torsional differences of more than 15 degrees, two of the seven patients with good outcomes. Torsional results of M1 and M2 correlated with the AOFAS score (r = -0.506). Conclusions: Of the 61 ankle fractures with ruptures of the syndesmotic complex, 25% showed torsional side-to-side differences of more than 10 degrees on proximal and distal CT planes. This CT technique correlated with the AOFAS score and could help determine when early operative revision is indicated.