• Orthopaedics Clinical Trials
• Hip & Knee Conditions
• Sports Medicine

• Orthopaedics
• Orthopaedics Clinical Trials
• Hip & Knee Conditions
• Sports Medicine

Robert A. Magnussen, MD, MPH, Wexner Medical Center, Ohio State University, Columbus, Ohio, USA, presented the findings of a randomized controlled trial on the effect of femoral nerve block (FNB) on quadriceps muscle strength and patient-reported outcomes following anterior cruciate ligament (ACL) reconstruction.

ACL reconstruction (ACLR) in athletes seeks to restore knee stability to withstand abrupt sports-related directional changes and pivoting. Postoperative rehabilitation often involves the restoration of quadriceps muscle strength to permit optimal sports performance and reduce the risk of re-injury. Blocking the function of the femoral nerve perioperatively can be done as a means of pain relief. Whether the approach hampers recovery of the quadriceps muscle is unclear [Atchabahian A et al. Anesthesiology 2001].

The trial addressed the hypotheses that perioperative FNB would result in significantly diminished strength in the lower quadriceps muscle 6 weeks after ACLR, as compared with preoperative muscle strength, and that postoperative improvements reported by patients would be delayed when FNB was used perioperatively.

Thirty patients who had experienced acute ACL injury and whose ACLR involved a hamstring autograft were randomly assigned to a group receiving a single injection of 20 mL of .5% ropivacaine using ultrasound guidance (n = 14) or a control group (n = 16) not receiving the FNB. Both groups underwent standard accelerated rehabilitation with weight bearing as tolerated and no braces. All patients were assessed preoperatively and at 12 weeks postoperatively using the patient-reported Knee Injury and Osteoarthritis Outcome Score (KOOS), and isokinetic strength was tested at 60° per second. A 6-week postoperative assessment for all patients included KOOS and isometric strength testing at 90° of flexion.

Patients in both groups were similar preoperatively in age, gender composition, height, weight, body mass index, limb symmetry, and patient-assessed activities of daily living (ADLs), pain, and symptoms (Table 1).

No surgical or nerve block complications were evident, and clinically detectable femoral nerve palsy was absent in all patients throughout the follow-up period. Comparisons prior to ACLR and 6 weeks after surgery revealed that quadriceps strength did not vary significantly between the left and right legs in the absence of FNB, whereas nerve block was associated with significantly decreased quadriceps strength in the operative leg 6 weeks postoperatively (p < .05). By 12 weeks, quadriceps strength in both legs was similar in both patient groups.

Dr. Magnussen then addressed the association between FNB and KOOS values of ADL, pain, and symptoms. Both groups improved during the 12-week follow-up. The improvement was, however, more pronounced at 6 weeks in the absence of FNB. The change in KOOS ADL score at 6 weeks in the absence of block (6.5 ± 9.1) was greater than in the presence of block (.1 ± 11.3), but it was not significantly different (p = .12). Changes in KOOS pain and symptom values at 6 weeks postoperatively with no block (7.5 ± 9.0 and 10.1 ± 12.4, respectively) and with block (−1.1 ± 14.1 and −3.0 ± 21.3, respectively) were not significant (p = .069 and p = .059). Values of all assessed parameters at 12 weeks postoperatively were similar between groups.

FNB was associated with decreased quadriceps strength and an absence of patient-reported improvements at 6 weeks postoperatively. By 12 weeks, these deficits were not apparent. The long-term effects, if any, of quadriceps weakness in the early weeks following ACLR in patients receiving perioperative FNB remain unclear.

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