Internal rotation radiographs improve postoperative assessment of hinge fracture and gap filling after open-wedge distal tibial tuberosity osteotoy.

Abstract

Postoperative assessment of lateral hinge fractures and gap filling after opening-wedge distal tibial tuberosity osteotomy (OWDTO) can be difficult on standard anteroposterior (AP) radiographs because of projection-related superimposition. This study aimed to determine whether internal rotation (IR) radiographs provide higher agreement with computed tomography (CT) than standard AP radiographs for postoperative assessment after OWDTO. This retrospective study included 42 knees that underwent OWDTO. AP and IR radiographs were obtained at 1, 2, and 4 weeks and 3 months postoperatively, with CT at 2 weeks and 3 months. Osteotomy visualization was compared between AP and IR views. Temporal reproducibility of gap-width measurements was evaluated using the intraclass correlation coefficient (ICC). Agreement with CT for hinge fracture detection and gap-filling classification was evaluated using Cohen's kappa coefficient, and sensitivity and specificity for hinge fracture detection were calculated. Clear visualization of the osteotomy and hinge region was observed more frequently on IR radiographs than on AP radiographs (p < 0.001). The temporal ICCs for gap-width measurements across 1, 2, and 4 weeks were 0.893 for AP radiographs and 0.961 for IR radiographs. For hinge fracture detection, agreement with CT was higher for IR than for AP radiographs (κ = 0.82 vs 0.53), with sensitivity/specificity of 83.3%/96.7% and 50.0%/96.7%, respectively. For gap-filling assessment, agreement with CT was also higher for IR than for AP radiographs (κ = 0.55 vs 0.15), with fewer false-positive classifications. IR radiographs showed higher agreement with CT than standard AP radiographs for early postoperative assessment after OWDTO, particularly for lateral hinge fracture detection. IR positioning may serve as a practical adjunctive view for improving radiographic visualization of the osteotomy and hinge region during routine follow-up.