Femoral nerve blocks significantly impair quadriceps strength when used for postoperative analgesia after total knee arthroplasty (TKA) and anterior cruciate ligament (ACL) reconstruction, according to separate studies presented in March at the annual meeting of the American Academy of Orthopaedic Surgeons (AAOS).

“A femoral nerve blockade, though very effective, is not without potential complications,” said Grigoriy Arutyunyan, MD, an orthopedic surgeon at the Mayo Clinic in Rochester, MN, who presented his group’s findings on ACL reconstruction at the AAOS meeting.

Retrospectively reviewing 196 patients, Arutyunyan and colleagues found that isokinetic quadriceps strength six months after bone patellar tendon bone autograft surgery was significantly worse in the 96 patients who received continuous femoral nerve blocks than in the 100 who did not. The nerve block group also performed more poorly on vertical jump, single hop, and triple hop tests. Somewhat surprisingly, however, return-to-sport rates in the two groups were not significantly different.

In 135 patients who underwent TKA, researchers from the Universite Laval in Quebec City, Canada, found that those who received either continuous or single-shot femoral nerve blocks had less quadriceps strength at six weeks, six months, and 12 months than those who did not receive a nerve block. There was no correlation between quadriceps strength and knee range of motion, which has previously been suggested as a measure of functional recovery after TKA.

“We think femoral nerve blocks should not be recommended for analgesia after total knee replacement,” said Michele Angers, MD, now an orthopedic surgeon at the University of California, San Francisco, who presented the group’s findings at the AAOS meeting.

Quadriceps weakness may increase the risk of postoperative falls, which a third AAOS study found occurred significantly more often in TKA patients with nerve blocks than those without. In 7093 patients who underwent TKA or total hip arthroplasty, researchers from the University of Pittsburgh found that nerve block use significantly affected inpatient fall rates only in the TKA patients. In the Canadian study, two TKA patients in the single-shot femoral nerve block group suffered falls in the first postoperative week that necessitated
further surgery.

“We don’t know if all falls can be prevented, but I think we’ve identified some areas that can be looked at for intervention,” said Brian A. Klatt, MD, an assistant professor of orthopaedic surgery at the University of Pittsburgh, who presented his group’s findings at the AAOS meeting.

Arutyunyan G, Krych AJ, Levy BA, et al. The adverse effect of femoral nerve blockade on quadriceps strength after ACL reconstruction. Presented at the Annual Meeting of the American Academy of Orthopaedic Surgeons, Chicago, March 2013.

Pelet S, Angers M, Belzile E, Vachon J. Influence of femoral block on quadriceps strength recovery after total knee replacement. Presented at the Annual Meeting of the American Academy of Orthopaedic Surgeons, Chicago, March 2013.

Klatt BA, Pigott M, Farber N, et al. Use of nerve blocks after total joint arthroplasty leads to increased rate of falls. Presented at the Annual Meeting of the American Academy of Orthopaedic Surgeons, Chicago, March 2013.