Femoral nerve catheter analgesia may improve early function post-TKA

Patients who received femoral nerve block had significantly better mean knee flexion on the first day postop vs. patients who received intravenous opioids.

Controlling pain using a femoral nerve catheter rather than standard intravenous opioids may improve early knee function after total knee arthroplasty, a study suggests.

Martin L. De Ruyter, MD, associate professor of anesthesiology at Kansas University Medical Center in Kansas City, Kan., conducted the study with colleagues at Texas Tech University Health Sciences Center in Odessa, Texas, and at the Mayo Clinic in Jacksonville, Fla. The researchers compared the two analgesic approaches for controlling postop pain in a consecutive series of patients who underwent elective, unilateral total knee arthroplasty (TKA) for degenerative joint disease.

The study included data for 24 patients who received a femoral perineural catheter with continuous infusion of ropivacaine and patient-controlled boluses. These patients were compared to 26 patients who received traditional standard postop analgesia consisting of either intravenous morphine sulfate or hydromorphone.

The results are published in the Journal of Arthroplasty.

In all cases, surgery involved a standard medial parapatellar incision with implantation of a PFC Sigma Knee System (DePuy Orthopedics). All patients also initiated a similar postop rehabilitation program beginning the first postoperative day, which involved physical therapist-directed rehab twice daily for 4 days, according to the study.

Of the 26 patients in the opioid group, 19 received an epidural anesthetic, five received general anesthesia and two received spinal anesthesia for surgery. Of the 24 femoral nerve catheter (FNC) patients, 17 received spinal anesthesia and seven received general anesthesia during surgery.

The researchers found that both groups had similar self-reported Visual Analog Scale pain scores on the first postoperative day, which averaged 4.8 for the FNC group and 4.9 for the opioid group. Both groups also had similar needs for assistance to move from a supine to a sitting position and for gait.

However, FNC patients had significantly better mean knee flexion on the first day postop, averaging 76.5° compared to 67° for opioid patients (P=.004), according to the study.

At the fourth and final day of rehabilitation, FNC patients required significantly less assistance to move into a sitting position (P=.017). They also required less gait assistance, although this difference was not significant (P=.072), the authors said. Patients in the FNC group used significantly less patient-controlled analgesia, 29.1% vs. 84.6% for patients in the opioid group (P<.05).

Duration of hospitalization was also significantly shorter for FNC patients, averaging 3.6 days compared to 4.2 days for opioid-treated patients (P=.034), according to the study.

For more information:
De Ruyter ML, Brueilly KE, Harrison BA, et al. A pilot study on continuous femoral perineural catheter for analgesia after total knee arthroplasty. J Arthroplasty. 2006;21:1111-1117.