• Ulrik Grevstad, Ole Mathiesen, Laura Staun Valentiner, Pia Jaeger, Karen Lisa Hilsted, and Jørgen B Dahl.
• From the *Department of Anaesthesia and Intensive Care Medicine, Copenhagen University Hospital, Gentofte Hospital, Gentofte; †Section of Acute Pain Management, Department of Anaesthesia, Centre of Head and Orthopaedics, Copenhagen University Hospital, Rigshospitalet, Copenhagen; and ‡Department of Orthopaedic Surgery, Copenhagen University Hospital, Gentofte Hospital, Gentofte; and §Department of Anaesthesia, Centre of Head and Orthopaedics, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
• Reg Anesth Pain Med. 2015 Jan 1; 40 (1): 3-10.

Background And ObjectivesTotal knee arthroplasty (TKA) is often associated with severe pain. Different regional anesthetic techniques exist, all with varying degrees of motor blockade. We hypothesized that pain relief provided by the adductor canal block (ACB) could increase functional muscle strength.MethodsWe included 50 TKA patients with severe movement-related pain; defined as having visual analog scale pain score of greater than 60 mm during active flexion of the knee. The ACB group received an ACB with ropivacaine 0.2% 30 mL and a femoral nerve block (FNB) with 30 mL saline. The FNB group received an ACB with 30 mL saline and an FNB with ropivacaine 0.2% 30 mL. We compared the effect of the ACB versus FNB on maximum voluntary isometric contraction of the quadriceps muscle relative to a postoperative baseline value. Secondary end points were differences between groups in ability to ambulate and changes in pain scores (Clinicaltrials.gov identifier NCT01922596).ResultsAfter block, the quadriceps maximum voluntary isometric contraction increased to 193% (95% confidence interval [CI], 143-288) of the baseline value in the ACB group and decreased to 16% (95% CI, 3-33) in the FNB group with an estimated difference of 178% (95% CI, 136-226), P < 0.0001. Pain scores were similar between groups. Before block, 2 of 25 patients in each group were unable to perform the Timed-Up-and-Go test; after block, this number increased to 7 of 25 in the FNB group and decreased to 0 of 25 in the ACB group.ConclusionAdductor canal block provides a clinically relevant and statistically significant increase in quadriceps muscle strength for patients in severe pain after TKA.

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