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Background and Aims The IPACK block is the first choice for good analgesia with better motor sparing than sciatic or tibial nerve blocks after total knee arthroplasty (TKA). We also argue that the popliteal plexus block (PPB) provides sensory block of the posterior knee capsule when local anesthesia is extended from the adductor hiatus to the popliteal fossa.

Methods 20 patients undergoing TKA were retrospectively reviewed. Patients received 15 mL of 0.25% levobupivacaine for IPACK or PPB with a multimodal analgesia protocol that included an adductor block. The primary outcome was dorsiflexion muscle strength 6 hours after the nerve block procedure, and we evaluated the value as a percentage of the preoperative baseline. Secondary outcomes were time to discharge criteria, pain scores, use of additional analgesics, pain scores, and knee flexion range in the operative knee.

Results The percentage of dorsiflexion strength at 6 hours postoperatively was 79±19% in PPB versus 63±23% in IPACK (mean±SD, difference 15%; 95% CI: -34 to 2%; p = 0.08). Other outcomes were not statistically different between the two treatment groups.

Conclusions Our results suggest that PPB and IPACK provide no difference in dorsiflex muscle strength. However, PPB tends to preserve dorsal motor function, suggesting less potential for anesthetic infiltration around the peroneal nerve than IPACK. We believe this trend warrants a larger sample size and a prospective, double-blind, randomized controlled trial to draw the proper statistical conclusions, and a clinical study is currently underway.