Analgesic Efficacy of Repeated Daily Injections Versus Continuous Adductor Canal Block After Total Knee Arthroplasty:...

Total knee arthroplasty is frequently associated with postoperative pain. Continuous adductor canal blocks are widely used for postoperative analgesia. However, the high dislocation rate of nerve block catheters often leads to ineffective pain control. This study aimed to compare the analgesic effectiveness of repeated daily injections of adductor canal block up to postoperative day (POD) 2 and continuous adductor canal block in patients who underwent total knee arthroplasty.

Seventy-six patients who underwent total knee arthroplasty under spinal anesthesia were randomized to receive repeated daily adductor canal blocks at the end of surgery and in the morning of POD1 and POD2 (n = 39) or continuous adductor canal block with a patient-controlled bolus (n = 37). All patients received perioperative multimodal analgesia. The primary outcome was the time-weighted average numeric rating scale pain score at rest, measured from the end of surgery to 14:00 on POD2. Pain scores over time were also compared using generalized estimating equations.

There was no significant difference in the time-weighted average pain score at rest (from POD0 to POD2) between the repeated injection group (2.9 ± 1.9) and the continuous group (3.1 ± 2.1; mean difference 0.09, 95% confidence interval [CI], -0.81 to 0.99; P = .842). Repeated daily injections did not reduce pain at rest or pain during movement after adjusting for time. In the continuous group, the cumulative occurrence of nerve block catheter dislocation was 48.6% (18/37) on POD1 and 62.2% (23/37) on POD2, as assessed using ultrasonography.

This study was unable to determine whether repeated daily injections or continuous adductor canal block provided superior analgesia in terms of the average pain score during the first 2 days after total knee arthroplasty. However, considering the high dislocation rate of nerve block catheters, reducing catheter dislodgement may improve the analgesic effectiveness of continuous adductor canal blocks.