Difference of preoperative varus-valgus stress radiograph is effective for the correction accuracy in the preoperative planning during open-wedge high tibial osteotomy

Purpose This study aimed to evaluate (1) the efficacy of varus-valgus stress radiographs to adjust the preoperative soft-tissue imbalance and (2) ascertain whether varus-valgus stress radiographs are effective for the correction accuracy in the preoperative planning of the opening wedge high tibial osteotomy (OWHTO). Methods From February 2017 to December 2018, a total of 121 consecutive knees that underwent bi-planar OWHTO were enrolled in this retrospective analysis. Preoperative planning was performed using a weight-bearing line (WBL). Target WBL was determined according to the status of the medial compartments such as cartilage, meniscus, and preoperative arthritic grade. Preoperative varus-valgus stress radiographs were used to assess the preoperative mediolateral ligament imbalance. The final target correction length of the opening gap was determined by subtracting the difference between the varus-valgus stress radiographs (VVD). All patients were divided into two groups according to the preoperatively planned correction degree: (group A), smaller than average; (group B), larger than average. Patients were also divided into two other groups (VVD adjusted and neglected groups). Results Groups A and B were 56 and 54 knees, respectively. The preoperatively planned correction lengths of the opening gap were 9.33 +/- 1.5 and 14.16 +/- 3.96 mm, respectively (p < 0.01). Mean values of the VVD were 0.85 +/- 0.72, and 1.27 +/- 1.78 mm, respectively (p < 0.01). Correction errors were 2.17 +/- 2.06 and 3.52 +/- 2.16%, respectively (p < 0.01). Planned and final correction degrees were also significantly larger (p < 0.01, andp < 0.01, respectively), because the preoperative WBL ratio was significantly smaller in the VVD adjusted group (p < 0.01). Conclusion The VVD values could reproduce the preoperative soft-tissue imbalance and it was more prominent as the correction degree increased. The strategy of subtracting the VVD as assumed soft-tissue imbalance in the preoperative planning worked well for the correction accuracy during OWHTO.