April 2013

Postoperative femoral nerve blocks sap quadriceps strength, increase risk of falls

In the moment: Knee

By Jordana Bieze Foster

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.

One Response to Postoperative femoral nerve blocks sap quadriceps strength, increase risk of falls

  1. Le kenobbie says:

    Has sciatic nerve blocks been used in conjunction with the FNB? I have found the combination of the 2 has a major impact on pain relief behind the knee. Are these FNB being done pre-op or post-op? I have found over the 36 yrs of practice it is best to do blocks post-op. If there is any nerve damage it CAN NOT be blamed onto anesthesia provider. Opinions vary.
    I am not sure if I understand the need to STOP using FNB for pain relief because of lack of quad strength. IE: epidurals have been shown to diminish uterine contractions and slow the process of delivery where an ITN given at 5-6 CM actually increases delivery. Has this stopped the use of epidurals for labor? Many of those complaining have never experienced a TKR/A so how do they know if it is what the patients want? From the pain I have seen post-op from this procedure I would want whatever is available to diminish pain. Quad strength is regain-able over time/rehab. Keeping patient semi-comatose on narcotics post-op keeps them in house too long. I have used FNB in conjunction with Sciatic NB with great success and have NEVER had a surgeon complain to me about loss of strength. I would think simply not being able to use the leg for some time post-op would be as much of a concern as to strength in the quads.
    Has there been studies using less block solution, decreasing drip flow, ultra sound placement of catheter. MAYBE it is not the catheter but the anesthetic solutions?
    As most THA only take a few minute in comparison to a TKA, I only use spinal with ITN/AMS/as most people have little pain post-op and are up and about that night and out much sooner than with a TKA.
    This from my experience and will be, I’m sure, seen as personal and unsubstantiated.

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