Background: Periarticular injection is a popular method to control postoperative pain after total knee replacement. An adductor canal block is a sensory block that can also help to alleviate pain after total knee replacement. We hypothesized that the combination of adductor canal block and periarticular injection would allow patients to reach discharge criteria 0.5 day faster than with periarticular injection alone.
Methods: This prospective trial enrolled 56 patients to receive a periarticular injection and 55 patients to receive an adductor canal block and periarticular injection. Both groups received intraoperative neuraxial anesthesia and multiple different types of pharmaceutical analgesics. The primary outcome was time to reach discharge criteria. Secondary outcomes, collected on postoperative days 1 and 2, included numeric rating scale pain scores, the PAIN OUT questionnaire, opioid consumption, and opioid-related side effects.
Results: There was no difference in time to reach discharge criteria between the groups with and without an adductor canal block. The Wilcoxon-Mann-Whitney odds ratio was 0.87 (95% confidence interval [CI], 0.55 to 1.33; p = 0.518). The median time to achieve discharge criteria (and interquartile range) was 25.8 hours (23.4 hours, 44.3 hours) in the adductor canal block and periarticular injection group compared with 26.4 hours (22.9 hours, 46.2 hours) in the periarticular injection group. Patients who received an adductor canal block and periarticular injection reported lower worst pain (difference in means, -1.4 [99% CI, -2.7 to 0]; adjusted p = 0.041) and more pain relief (difference in means, 12% [99% CI, 0% to 24%]; adjusted p = 0.048) at 24 hours after anesthesia. There was no difference in any other secondary outcome measure (e.g., opioid consumption, opioid-related side effects, numeric rating scale pain scores).
Conclusions: The time to meet the discharge criteria was not significantly different between the groups. In the adductor canal block and periarticular injection group, the patients had lower worst pain and greater pain relief at 24 hours after anesthesia. No difference was noted in any other secondary outcome measure (e.g., opioid consumption, opioid-related side effects, numeric rating scale pain scores).
Level of evidence: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.