Correlation of knee joint alignment correction between valgus stress and postoperative radiography after unicompartmental knee arthroplasty
Li Shichao1, Xie Guangyue1, Sun Zhen1, Han Peng1, Hou Xiaohua1, Sun Xiaowei2, Zhang Qidong2
1Department of Orthopedics, Tangshan Gongren Hospital, Tangshan 063000, Hebei Province, China; 2Department of Orthopedics, China-Japan Friendship Hospital, Beijing 100029, China
Abstract: BACKGROUND: Stress radiographs had a certain reference value for the correction of the lower limb alignment in unicompartmental knee arthroplasty, but the extent of tibiofemoral subluxation correction was still unclear. In addition, most medical centers did not pay enough attention to this examination.
OBJECTIVE: To clarify the correlation between the degree of correction of knee varus deformity and subluxation on the stress radiographs and the X-ray appearance after unicompartmental knee arthroplasty.
METHODS: We retrospectively analyzed the patients who undertook unicompartmental knee arthroplasty from January 2018 to January 2021. Totally 37 patients with 50 knees were included. The clinical outcome, and the radiographic assessment including the hip-knee-ankle angle, joint line convergence angle and coronal tibiofemoral subluxation value were assessed on pre- and post-operative full-length radiographs, as well as preoperative valgus stress radiographs. The correlations in-between these factors were analyzed.
RESULTS AND CONCLUSION: (1) Compared with preoperative radiographs, hip-knee-ankle angle, joint line convergence angle and coronal tibiofemoral subluxation were significantly corrected in valgus stress and postoperative radiographs (P < 0.05). (2) Pearson correlation analysis showed that the correction of joint line convergence angle on the valgus stress radiographs was positively correlated with the correction of hip-knee-ankle angle after unicompartmental knee arthroplasty (r=0.420, P < 0.05), while the correction of coronal tibiofemoral subluxation at valgus stress radiographs was also positively correlated with the correction of postoperative coronal tibiofemoral subluxation (r=0.754, P < 0.05). (3) Thus, unicompartmental knee arthroplasty can correct the varus deformity and coronal tibiofemoral joint subluxation of the knee joint, and the degree of correction can be effectively predicted by preoperative valgus stress radiographs.
Key words: uniconpartmental knee arthroplasty, valgus stress radiograph, coronal tibiofemoral subluxation, knee osteoarthritis, correlation analysis