Femoral Nerve Blockade Does Not Lead to Subjective Functional Deficits After Anterior Cruciate Ligament Reconstruction

Abstract

Anterior cruciate ligament reconstruction (ACLR) ranks among the most common surgeries performed in civilian as well as military orthopedic settings. Regional anesthesia, and the femoral nerve block (FNB) in particular, has demonstrated efficacy in reducing postoperative pain and opioid use after ACLR, however concerns linger about possible impaired functional outcomes. The purpose of the current investigation was to assess International Knee Documentation Committee Subjective Knee Form (IKDC-SKF) scores at 6 to 12 months after ACLR in patients who did (FNB) and did not (NoFNB) receive a perioperative FNB. All patients undergoing unilateral ACLR in the study period were reviewed in this institutional process improvement analysis. The primary outcome was prospectively collected IKDC-SKF scores obtained at 6-12 months post-surgery. Demographic and surgical information collected as potential covariates included age, sex, body mass index (BMI), preoperative IKDC-SKF score, use of an FNB, use of another (not femoral nerve) block, American Society of Anesthesiologists (ASA) score, graft type (auto vs. allograft), concomitant meniscus or cartilage procedures, tobacco use, tourniquet time, and primary vs. revision surgery. Assuming a 1:2 ratio of patients who did not vs. did receive FNBs and a clinically meaningful difference of 7 points on the IKDC-SKF, 112 patients were required for 80% power. A regression model averaging approach examined the relationships between covariates and postoperative IKDC-SKF scores. One hundred nineteen patients met inclusion criteria (FNB 79 and NoFNB 40). The cohorts were significantly different in several factors including BMI, ASA level, graft type, and other peripheral nerve blocks, which were controlled for through regression modeling. Regressions with model averaging examined the relationship between treatment groups and postoperative IKDC-SKF scores, along with other potential predictor variables. Estimated adjusted marginal differences in postoperative IKDC-SKF scores from the best-fitting model revealed a very small 0.66-point mean (P = .86) difference between NoFNB and FNB groups that was not statistically significant. Those who reported tobacco use had a 10.51 point (P = .008) lower mean postoperative IKDC-SKF score than those who did not report tobacco use. Every 1-point increase in the preoperative IKDC-SKF score was associated with a 0.28-point (P = .02) increase in the postsurgical IKDC-SKF score. Active tobacco use may negatively impact short-term subjective patient-reported outcomes after ACLR, as reported by the IKDC-SKF. Lower preoperative scores are also associated with significantly lower postoperative IKDC-SKF scores while the use of a FNB was not associated with lower postoperative scores. The negative association between tobacco use and patient-reported functional outcomes after ACLR lends further support to tobacco cessation programs within the military.