Purpose: Subsartorial saphenous nerve blockade (SSNB) is an effective analgesic alternative to femoral nerve blockade after anterior cruciate ligament (ACL) reconstruction with bone-tendon-bone (BTB) autograft. It was hypothesized that dexamethasone in a SSNB will prolong analgesia, improve pain and satisfaction, and reduce postoperative opioid requirements and side effects.
Methods: One hundred ninety-five patients undergoing ACL reconstruction with BTB autograft (ages 16-65) were enrolled. Subjects received SSNB with 13 ml of 0.5 % bupivacaine (control group), 1 mg preservative-free dexamethasone +0.5 % bupivacaine (treatment group I), or 4 mg preservative-free dexamethasone +0.5 % bupivacaine (treatment group II). Subjects received identical perioperative management. On postoperative days 1 and 2, subjects reported perceived block duration, pain scores, satisfaction, opioid use, and side effects. Cox-proportional hazards modelling was used to compare block duration, adjusting for body mass index, age, sex, tourniquet time, American Society of Anesthesiologists classification, and intravenous dexamethasone dose.
Results: Patient-perceived block duration was significantly increased in treatment group I [hazard ratio (95 % confidence interval [CI]) 0.48 (0.31-0.75); P = 0.001] and treatment group II (hazard ratio (95 % CI): 0.52 (0.33-0.81); P = 0.004) compared to control. The block was extended from a median (95 % CI) of 33.1 (28.4-37.3) to 41.2 (32.4-50.9) and 46.5 (35.8-48.9) hours, respectively. Additionally, patients in treatment group II reported increased time that block provided pain relief, higher patient satisfaction, lower pain scores at rest, and decreased drowsiness and confusion.
Conclusion: The addition of 1 and 4 mg of dexamethasone to the block injectate significantly increased SSNB duration by 8-13 h compared to control.
Level of evidence: Therapeutic study, level 1.
Keywords: ACL reconstruction; Patellar tendon autograft; Postoperative pain; Subsartorial saphenous nerve block.