[Correlational between the gap contact force and the degree of lower limb alignment correction in Oxford mobile bearing unicompartmental knee arthroplasty].

To study the correlation between joint contact force and postoperative lower extremity alignment in Oxford unicompartmental knee arthroplasty (OUKA) and provide reference data for predicting the lower extremity alignment after OUKA. It was a retrospective case series study. A total of 78 patients (92 knees) who underwent OUKA surgery from January 2020 to January 2022 in the Department of Orthopedics and Joint Surgery of China-Japan Friendship Hospital were included in this study, including 29 males and 49 females, aged (68.8±6.9) years. A custom-designed force sensor was used to measure gap contact force in the medial gap of OUKA. The patients were divided into groups according to the varus degree of lower limb alignment after operation. Relationship between the gap contact force and the alignment of the lower limbs after operation was analyzed with Pearson correlation analysis, and the gap contact force was compared between patients with different lower limbs alignment correcting results. The mean contact force measured during the operation at 0° of knee extension was 81.7 N±57.8 N, and it was 96.1 N±54.5 N at 20° of knee flexion. The average postoperative knee varus angle was 2.9°±2.7°. The gap contact force at the 0° and 20° positions of the knee joint was negatively correlated with the varus degree of the postoperative lower limb alignment (=-0.493, -0.331, both <0.001). The distribution of gap contact force at 0° was different in each group, the contact force [ (, )] of the neutral position group(=24) was 117.4 N (31.7 N, 233.0 N), and it was 63.7 N (11.3 N, 209.0 N), 31.5 N (8.3 N, 87.7 N) in the mild varus group (=51) and the significant varus group (=17), respectively, and the difference was statistically significant (<0.001); while at 20°, only the difference between the significant varus group and the neutral position group was statistically significant (=0.040). The gap contact force of the alignment satisfactory group at 0° and 20° was greater than those in the significant varus group (both <0.05). The gap contact force measured at 0° and 20° was significantly greater in patients with preoperative significant flexion deformity than in patients without flexion deformity (or mild flexion deformity) (both <0.05). OUKA gap contact force is related to the degree of lower limb alignment correction after the operation. In patients with well-corrected lower limb alignment after surgery, the median intraoperative knee joint gap contact force at 0° and 20° is 117.4 N and 92.5 N, respectively.