Appropriate patient selection based on joint line convergence angle minimizes the difference between the mechanical axis in the standing and supine positions after open-wedge high tibial osteotomy and distal tuberosity osteotomy.

Background: This study aimed to evaluate the differences between the mechanical axis (MA) in standing and supine positions in patients who underwent high tibial osteotomy (HTO) or distal tuberosity osteotomy (DTO) based on the surgical indication for the joint line convergence angle (JLCA).

Methods: Seventy-one knees of 69 patients with JLCA of < 6° in standing position and a difference of < 3° between the JLCA in the standing and supine positions who had undergone medial open-wedge HTO or DTO were included in this study. The %MA in the standing and supine positions (%MAst and %MAsp, respectively) and JLCA in the standing and supine positions (JLCAst and JLCAsp, respectively) were determined using preoperative and postoperative long-leg-view radiographs. The difference between %MA and JLCA in the standing and supine positions (Δ%MA and ΔJLCA, respectively) was calculated by subtracting the measurement value in the supine position from that in the standing position.

Results: The preoperative %MAst, %MAsp, JLCAst, and JLCAsp were 23.8 ± 9.5%, 28.7 ± 8.0%, 2.9 ± 1.4°, and 1.6 ± 1.4° respectively. The preoperative Δ%MA and ΔJLCA were - 4.9 ± 5.9% and 1.3 ± 1.0° respectively. The postoperative %MAst, %MAsp, JLCAst, and JLCAsp were 58.8 ± 6.9%, 59.0 ± 6.2%, 1.7 ± 1.0°, and 1.5 ± 1.1°, respectively. No significant differences were observed between the postoperative %MAst and %MAsp. The postoperative Δ%MA and ΔJLCA were - 0.2 ± 3.0% and 0.3 ± 0.6°, respectively. The postoperative Δ%MA was - 5 to 5% in 68 knees (95.8%).

Conclusion: Minimal differences were observed between the Δ%MA after HTO and DTO among patients with preoperative JLCAst of < 6° and ΔJLCA and of < 3°, respectively. Appropriate surgical indications could minimize this difference.