Over the past two decades, femoral nerve block has been central to postoperative analgesia for total knee arthroplasty (TKA), but preference has shifted to other peripheral nerve blocks that can provide analgesia around the knee without the key drawback associated with the femoral block. The trajectory of the use of femoral nerve block illustrates how an intervention can be validated by strong efficacy data and still be reconsidered because of concerns that only became apparent with wider clinical use.
Following its introduction, femoral nerve block was established as a substantial improvement over the exclusive use of intravenous patient-controlled analgesia (PCA) in managing pain after TKA. A 2010 meta-analysis of 23 randomized controlled trials encompassing 1,016 patients found that single-shot femoral block, with or without an added sciatic block, reduced morphine consumption at 24 and 48 hours, lowered pain scores with activity, and cut the incidence of nausea compared with PCA alone (1). These findings, alongside its comparatively low technical complexity relative to epidural analgesia and its avoidance of epidural hematoma risk, drove its adoption as a standard component of TKA pain protocols through the late 2000s and early 2010s (1).
However, as femoral nerve block use broadened beyond controlled trial settings and into routine orthopedic wards, a countervailing safety signal emerged. A 2009 case series from a Scottish orthopedic unit reported that, among approximately 250 patients who received femoral block for TKA, five suffered serious postoperative falls within the first two days after surgery, most resulting in complete wound dehiscence and one in a periprosthetic fracture requiring revision surgery and a 42-day hospital stay (2).
The authors attributed these falls to prolonged quadriceps motor blockade combined with preserved strength in the non-operative limb, which gave patients false confidence to mobilize unaided (2). They cautioned that the anesthesia literature had emphasized analgesic quality while largely overlooking mobilization risk, and recommended measures such as lower local anesthetic concentrations, avoidance of clonidine adjuncts, knee splinting, and restricted unassisted ambulation until motor function returned (2).
Concerns over motor impairment drove anesthesia professionals to explore alternative regional anesthesia techniques that could deliver sensory blockade while sparing the quadriceps. Adductor canal block (ACB), which targets a compartment containing predominantly sensory nerves and only a single efferent motor branch to the vastus medialis, emerged as the preferred option.
A 2017 meta-analysis of 12 randomized controlled trials comparing the two techniques for TKA found that ACB preserved significantly greater quadriceps strength, both by isometric contraction testing and by manual muscle grading, and was associated with a 70% reduction in the likelihood of postoperative falls (3). Importantly, ACB achieved this safety advantage without sacrificing analgesic quality: pain scores at rest and with activity, along with opioid consumption, did not differ significantly between the two techniques, and ACB was associated with better postoperative range of motion (3).
The use of femoral nerve block has expanded and subsequently decreased as anesthetic practice has evolved. Initially established as a superior alternative to systemic opioid analgesia, it has been displaced by motor-sparing techniques such as ACB in contemporary fast-track TKA pathways due to the recognition of fall risk tied to quadriceps weakness. However, femoral nerve block has not disappeared from practice, and it may still have use for patients requiring broader sensory coverage or when regional expertise favors it. But the prevailing trend in enhanced-recovery protocols has moved toward techniques that balance analgesia with early, safe mobilization, reflecting a broader shift in orthopedic anesthesia away from maximal blockade and toward function-preserving pain control.
References
- Paul, J. E.; Arya, A.; Hurlburt, L.; Cheng, J.; Thabane, L.; Tidy, A.; Murthy, Y. Femoral Nerve Block Improves Analgesia Outcomes after Total Knee Arthroplasty: A Meta-analysis of Randomized Controlled Trials. Anesthesiology 2010, 113 (5), 1144–1162. https://doi.org/10.1097/ALN.0b013e3181f4b18.
- Kandasami, M.; Kinninmonth, A. W. G.; Sarungi, M.; Baines, J.; Scott, N. B. Femoral Nerve Block for Total Knee Replacement — A Word of Caution. Knee 2009, 16 (2), 98–100. https://doi.org/10.1016/j.knee.2008.10.007.
- Wang, D.; Yang, Y.; Li, Q.; Tang, S.-L.; Zeng, W.-N.; Xu, J.; Xie, T.-H.; Pei, F.-X.; Yang, L.; Li, L.-L.; Zhou, Z.-K. Adductor Canal Block versus Femoral Nerve Block for Total Knee Arthroplasty: A Meta-analysis of Randomized Controlled Trials. Sci. Rep. 2017, 7, 40721. https://doi.org/10.1038/srep40721.