Changes in Coronal and Sagittal Alignment of the Ankle Joint After High Tibial Osteotomy: Evaluation Using Low Extremity Scanogram and EOS Imaging System

Abstract

Category: Ankle; Hindfoot Introduction/Purpose: High tibial osteotomy (HTO) is a useful treatment option for symptomatic knee patients with varus knee alignment and medial compartment arthritis. Changes in coronal and sagittal alignment of the knee joint have been reported in several previous studies. However, no study have investigated the changes of both coronal and sagittal alignment of the ankle joint after HTO. The purpose of this study was to investigate changes in coronal and sagittal alignment of the ankle joint after HTO. Our hypothesis was that alignment of ankle joint, as well as knee joint, change significantly after HTO. Methods: Total 46 patients (49 cases) were retrospectively analyzed after HTO for varus knee osteoarthritis. Preoperative and follow-up of low extremity scanogram and EOS imaging system were taken. The hip–knee–ankle (HKA) angle, medial proximal tibial angle (MPTA), knee tibia plafond angle (KTPA), were measured by scanogram to evaluate coronal alignment of the knee. Tibial anterior surface angle (TAS), Tibial plafond inclination (TPI), talar tilt (TT), and ankle joint axis point on the weight-bearing- line (AAWBL) were measured by scanogram to investigate coronal alignment of the ankle. Tibial lateral surface angle (TLS) and lateral knee tibial plafond angle (LKTPA) were measured by EOS to evaluate sagittal alignment of the ankle. Radiologic outcomes of the knee and ankle were evaluated pre- and postoperatively. Results: Varus alignment of the knee was corrected by significant coronal change of the HKA angle, MPTA, KTPA after HTO (P < 0.05). There was significant coronal change in TPI and AAWBL in ankle alignment (P < 0.05). The ankle joint axis point on the weightbearing axis moved laterally which was demonstrated by AAWBL. However, there was no significant difference between preoperative and follow up TAS and TT (P > 0.05). In sagittal alignment of ankle by EOS, LKTPA significantly increased after HTO (P > 0.05), but TLS showed no significant difference postoperatively (P > 0.05). Conclusion: Coronal and sagittal alignment of ankle joint was significantly changed after HTO by lateral shift of ankle joint axis and LKTPA increase after HTO. Further study is necessary to investigate the effects of the present radiologic results on clinical symptoms of the patients.