Effect of combining peri-hamstring injection or anterior obturator nerve block on the analgesic efficacy of adductor canal block for anterior cruciate ligament reconstruction: a randomised controlled trial

Background: Pain after anterior cruciate ligament reconstruction (ACLR) with autologous hamstring graft can be attributed to both arthroscopic surgery and the graft donor site. This study investigated whether donor site pain control was superior with the addition of either peri-hamstring injection or anterior division obturator nerve block in comparison with adductor canal block (ACB) alone. Methods: Patients scheduled to undergo knee arthroscopy with ACLR using a graft from the ipsilateral hamstring were randomised to one of three groups. All patients received ACB and multimodal analgesia. Subjects in Group H received peri-hamstring local anaesthetic injection while subjects in Group O received an anterior division of the obturator nerve block, and subjects in Group C served as a control group (ACB alone). Results: In 105 subjects undergoing ACLR, there was no significant difference between groups H, O, and C for the primary outcome of pain on movement as assessed by numerical rating scale (NRS) on knee flexion at 2 h after operation (P=0.11). There was no difference in NRS at any time point in the first 48 h after operation, nor was there a difference in oxycodone consumption between the three groups at 24 h (P=0.2). Worst knee pain was initially at the graft donor site in all three groups, which transitioned to anterior knee pain after 12 h. Conclusions: The addition of ultrasound-guided peri-hamstring injection or anterior division of obturator nerve block to ACB did not result in a significant reduction in pain or opioid consumption after ACLR with ipsilateral hamstring graft.