Medial opening low tibial osteotomy shifts the load laterally not only at the ankle joint but also at the knee joint

Abstract

Purpose: The purpose of this study was to determine the effects of medial opening low tibial osteotomy (LTO) on lower limb alignment, including the knee joint, 1 year after low tibial osteotomy.

Methods: This study included 20 legs of 20 patients (mean age, 66.8 ± 5.4 years) who underwent LTO for medial ankle osteoarthritis and evaluated the changes in the hip-knee-ankle angle (HKA), percentage hip-to-ankle line (%HA), percentage hip-to-calcaneal line (%HC), medial proximal tibial angle (MPTA), knee joint line convergence angle (K-JLCA), tibio-calcaneal angle (TCA), tibial anterior surface angle (TAS), tibio-plafond inclination (TPI), talar inclination (TI), ankle joint line convergence angle (A-JLCA), mechanical ankle joint axis point (MAJAP) on radiographs and the Japanese Society for Surgery of the Foot (JSSF) ankle/hindfoot scale before and 1 year after low tibial osteotomy.

Results: The mean preoperative/postoperative measured values showed the following: HKA (degrees) of 1.0 ± 3.7/-0.8 ± 3.7; %HC of 38.8 ± 10.0/53.8 ± 16.1; MPTA (degrees) of 85.6 ± 2.4/87.6 ± 2.1; and A-JLCA (degrees) of 4.2 ± 2.9/1.1 ± 2.3 respectively. Including other measurements, a significant increase in the %HA, %HC, MPTA, TCA, TAS, MAJAP and JSSF ankle/hindfoot scale was observed postoperatively, whereas a significant decrease in the HKA, TPA, TI and A-JLCA was observed postoperatively (p < 0.05). With the numbers available, no significant differences were observed between the preoperative and postoperative values of K-JLCA (n.s.).

Conclusion: After LTO, the entire lower limb alignment became valgus, and the loading points of the knee and ankle joints shifted laterally. These changes must be considered when performing LTO, especially in patients with lateral knee OA.

Level of evidence: Ⅳ.

Keywords: ankle osteoarthritis; knee alignment; low tibial osteotomy; lower limb alignment.