Tan M, Chen B, Li Q, et al. Comparison of Analgesic Effects of Continuous Femoral Nerve Block, Femoral Triangle Block, and Adductor Block After Total Knee Arthroplasty: A Randomized Clinical Trial. Clin J Pain. 2024 Jun 1;40(6):373-382. doi: 10.1097/AJP.0000000000001211. (Original study)

OBJECTIVES: This study aimed to compare the analgesic effects of continuous femoral nerve block (FNB), femoral triangle block (FTB), and adductor canal block (ACB) following total knee arthroplasty (TKA). The goal was to identify the most effective nerve block technique among these.

METHODS: Patients undergoing TKA were randomly assigned to 1 of 3 groups: FNB, FTB, or ACB. Nerve blocks were administered preoperatively, with catheters placed for patient-controlled nerve analgesia (PCNA). The primary end point was the Numeric Rating Scale (NRS) score at movement at 24 hours postsurgery. Secondary end points included NRS scores at rest and movement, quadriceps strength, Timed Up and Go (TUG) test performance, range of motion, effective PCNA utilization, and opioid consumption at various postsurgery time points.

RESULTS: Of the 94 valid data sets analyzed (FNB: 31, FTB: 31, ACB: 32), significant differences were observed in the primary end point (H=7.003, P =0.03). Post hoc analysis with Bonferroni correction showed that the FNB group had a significantly lower median pain score (3 [2 to 4]) compared with the ACB group (4 [3 to 5], Bonferroni-adjusted P =0.03). Regarding secondary end points, both the FNB and FTB groups had significantly lower NRS scores than the ACB group at various time points after surgery. Quadriceps strength and TUG completion were better in the FTB and ACB groups. There were no statistically significant differences among the groups for the other end points.

DISCUSSION: Continuous FTB provides postoperative analgesia comparable to FNB but with the advantage of significantly less impact on quadriceps muscle strength, a benefit not seen with FNB. Both FTB and ACB are effective in preserving quadriceps strength postoperatively.

Discipline Area Score
Physician 4 / 7
Comments from MORE raters

Physician rater

A well done study of analgesic regional anesthesia techniques for total knee replacement. I have no quibbles with the methods, approach, or presentation of the data. The authors confirmed what is most likely well known to practitioners: the higher on the leg the block, the better the pain relief but the more motor weakness. Pragmatically, local practice is more likely to be driven by surgical preferences, physical therapy goals, logistics of when and where the block can be administered, and personal (anecdotal) experience. Papers like this one, no matter how well done, therefore add little to real-world practice. The most important take-home point is that regional analgesia is important after knee replacement (compared with systemic analgesia only) and is the current standard of care.

Physician rater

This 3-armed and adequately powered RCT sought to determine the best regional analgesic technique following total knee arthroplasty. The authors compared rest and movement pain scores, motor function, rescue analgesia use, and complications. They found femoral triangle block to have equitable analgesic effect compared with femoral nerve block but better motor function and post-operative rehab. Both of these blocks outperformed adductor canal block. The authors employed strict exclusion criteria, notably patients <75 years, no use of prolonged opioids (>1 year), COPD and eGFR <60. I worry this excludes a significant number of patients who require knee arthroplasty and those who would benefit the most from opioid-sparing analgesia. The notable lack of patient-controlled nerve analgesia use (median 1 in 72 hours) and rescue doses of tramadol (median 2 in 72 hours) might suggest there is a lack of education for the patients or that a catheter may not be required.
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