Podium (Sports) 14

The Effect of Femoral Nerve Block Vs. Adductor Canal Block on Post-Operative Pain Scores, Knee Flexion Active ROM and Quadriceps Strength in Patients who had undergone Arthroscopic ACL Reconstruction using Hamstring Graft: A Case Series

Clariz S. Patricio, MD; Zara Grace J. Felix, MD; Henry R. Tabinas, Jr., MD, FPOA AFP

Background:  ACL injury is one of the most common sports related injuries; reconstruction is performed arthroscopically under spinal anesthesia using a hamstring autograft. Patients are encouraged to perform active ROM and isometric exercises postoperatively as soon as they are able to tolerate it. Most patients report post operative pain, preventing the performance of these exercises. Among available methods for post-operative pain control, femoral nerve block (FNB) or adductor canal block (ACB) can be performed. This case series was done to describe FNB and ACB, their effect on analgesia, knee flexion active ROM and quadriceps strength in patients who had undergone arthroscopic ACL reconstruction using hamstring graft. The researchers also wanted to explore potential adverse effects of FNB and ACB and if these are feasible to perform in the local setting.

Methods:  Seven patients scheduled for ACL reconstruction were recruited and randomly assigned to receive FNB or ACB. Baseline measurements of knee flexion active ROM and quadriceps strength were taken.  Postoperative pain control was done by giving bupivacaine bolus every 6h for the first day post-operatively, every 8 hours for the second day post-operatively and every 12h for the third day post-operatively. Patients were encouraged to perform knee flexion active ROM and straight leg raises as tolerated.  Postoperative VAS scores of patients during the first to third postoperative days were recorded to include adverse effects and the need for rescue analgesia.  Knee flexion active ROM at 72h and one week postoperatively, and quadriceps strength one week postoperatively were recorded.

Results: Knee flexion active ROM at 72h post-op was higher in patients under FNB (mean 80o) compared to those under ACB (mean 73.75o). At one week post-operatively, values for knee flexion active ROM were noted to be similar in patients under ACB (mean 92.5o) and FNB (mean 91.67o).  Quadriceps strength at one week post-op was noted to be similar in ACB (mean 58.96N) and FNB (56.66N).  For the pain scores, the ACB group had higher VAS pain scores compared to the FNB group on the first postoperative day. However t-test for postoperative days 1 to 3 showed no significant difference on the pain scores (Day 1: t stat 0.53 < t critical two-tail 2.57; Day 2: t stat 1.09 < t critical two-tail 2.78; Day 3: t stat 2.48 < t critical two-tail 3.18).    Only two out of seven respondents (29%) had the need for a rescue dose of analgesia.  Based on statistical analysis, there were no significant differences in rescue dose consumption.

Conclusion: This case series was able to discuss the advantages of FNB and ACB in arthroscopic ACL reconstruction using hamstring graft in the local setting in terms of pain scores, knee flexion active ROM, and quadriceps strength. It also discussed adverse effects such as motor block, local pain and altered sensation noted in patients who received FNB but not in patients who received ACB. The authors recommend further research on this topic to include a bigger study population in the form of a RCT.