Serial assessment of weight-bearing lower extremity alignment radiographs after open-wedge high tibial osteotomy

Abstract

Purpose: The purpose of this study was to perform a serial assessment of the radiologic parameters of the mechanical axis (MA) and the weight-bearing line (WBL) using a weight-bearing anteroposterior (AP) long-standing view of the lower extremity to determine whether the postoperative MA and WBL change with time.

Methods: A total of 90 consecutive lower limbs were examined retrospectively from a weight-bearing AP long-standing view of the lower extremity obtained from 120 patients who underwent open-wedge high tibial osteotomy (OWHTO). A total of 30 patients were excluded because of (1) complications (7 patients) such as bone graft collapse or broken screws, malunion, or nonunion arising after surgery and (2) no acquisition of a regular series of weight-bearing AP long-standing views of the lower extremity (23 patients). The AP long-standing view of the lower extremity was taken, and weight-bearing AP long-standing views of the lower extremity at 1 month, 6 months, 1 year, and 2 years postoperatively were used for assessment of serial change. The Picture Archiving Communication System (Marotech, Inc, St-Augustin-de-Desmaures, Quebec, Canada) was used for radiologic measurements of the WBL ratio and MA. Serial changes were compared between 1 month, 6 months, 1 year, and 2 years postoperatively.

Results: The WBL ratio progressively shifted medially, with significant changes at all time points until 1 year postoperatively (1 month to 6 months, P = .04; 6 months to 1 year, P = .04; 1 year to 2 years, P = .22). Even though the MA angle showed a similar decreasing trend, it showed no statistical difference (P > .05).

Conclusions: This study showed that after OWHTO, the WBL shifts progressively medially until 1 year postoperatively.

Level of evidence: Level IV, diagnostic study.