Effects of obturator and femoral nerve blocks on pain and kinematic gait parameters in patients undergoing unicompartmental knee arthroplasty: a retrospective cohort study.

Background: Postoperative data indicate that 15-30% of patients undergoing unicompartmental knee arthroplasty (UKA) experience moderate-to-severe pain during the early recovery period, impeding rehabilitation. Due to the complex innervation in the knee, continuous femoral nerve block (FNB) is often administered but provides incomplete analgesia. Although the analgesic effects of nerve blocks are well studied, less is understood about their effects on postoperative rehabilitation and gait kinematics. Thus, in this study, we aimed to investigate the impact of ultrasound-guided obturator nerve block (ONB) combined with FNB on gait kinematics in patients undergoing UKA. This is the first study to quantify the biomechanical benefits of ONB combined with FNB in patients undergoing UKA by gait analysis.

Methods: Patients undergoing UKA and admitted to the Department of Orthopedics, People's Hospital of Ningxia Hui Autonomous Region between March 2024 and December 2024 were retrospectively enrolled. The patients were allocated based on their postoperative nerve block procedure into the FNB or FNB + ONB group, with 30 cases in each group. The FNB group underwent ultrasound-guided, single-shot FNB with catheterization, whereas the FNB + ONB group underwent additional ipsilateral ONB. Patient demographics, preoperative and postoperative visual analog scale (VAS) scores (at rest and during 30° knee flexion), adverse events, kinematic gait parameters, Knee Society Score, and range of motion were recorded.

Results: No intergroup differences were observed in the preoperative VAS scores (P > 0.05). Both groups showed improved postoperative VAS scores (P < 0.05) with comparable resting VAS scores (P > 0.05). The FNB + ONB group demonstrated significantly lower activity-associated VAS scores than did the FNB group (P < 0.05). Analgesic rescue needs and adverse event rates showed no intergroup differences (P > 0.05). The FNB + ONB group exhibited superior postoperative Knee Society Scores, greater range of motion, and reduced kinematic gait abnormalities compared with the FNB group (all, P < 0.05).

Conclusion: ONB combined with FNB provides superior postoperative analgesia compared with FNB alone in patients undergoing UKA, particularly during activity, thereby facilitating early rehabilitation and mitigating postoperative gait disturbances.