Objectives: This study’s objective was to determine whether multimodal analgesia plus an injection of the hamstring sheath immediately following the harvest of the semitendinosus and gracilis tendons during hamstring autograft anterior cruciate ligament reconstruction (ACLR) reduces postoperative pain. We hypothesized that multimodal analgesia plus a hamstring sheath injection of the harvest site for autograft hamstring ACLR reduces postoperative pain. Methods: The Institutional Review Board approved this study registered with ClinicalTrials.gov and identified by NCT01868425. This study was a single-center, surgeon stratified double-blind, placebo-controlled, randomized study from April 2013 to December 2017. Patients were randomly assigned to one of two groups, in a 1:1 ratio per surgeon, to receive either standard of care analgesia plus intra-operative hamstring sheath saline injection (Placebo group) or standard of care analgesia plus multimodal analgesia plus intraoperative hamstring sheath anesthetic injection (MA group) for patients undergoing ACLR with hamstring autograft. Eligible participants were adults aged 18 years to 55 years old consented for ACLR using hamstring tendon autograft. Contraindication to a femoral nerve block, allergy to protocol medications, nervous system disease, renal or hepatic impairment, history of opioid dependence or current narcotic use, significant psychiatric disease, pregnancy or lactating, a seizure disorder, history of postoperative nausea and vomiting, latex allergy, and clinically significant cardiac or pulmonary disease excluded patients for participation in this study. The primary endpoint was total postoperative opioid administration. Secondary endpoints included the patient’s subjective pain score for the posterior, anterior, and lateral side of the knee, postoperative nausea, sedation, and pruritus scores. Based on our preliminary data, we estimated the mean opioid for standard care will be 6.6 morphine equivalents with a standard deviation of 6.2 morphine equivalents. Testing the ability of multimodal analgesia to reduce opioid usage by at least 50%, a minimal sample size of 45 subjects per group was needed to achieve 80% power based on a one-tailed t-test and a significance level < 0.05. Student’s t-test compared outcomes between groups. Additionally, a linear regression model for was also used for the primary outcome with total opioid administration as the dependent variable in order to control for body mass index (BMI) and sex, providing an adjusted estimate of the difference between groups. Results: A total of 112 patients (Figure 1) met inclusion criteria and were randomized into the placebo group (n = 57) and MA group (n = 55). Demographic data demonstrated no significant differences between groups (Table 1). The primary analysis was postoperative opioid administration and included all patients randomly assigned to either group for opioid administration in the postoperative anesthetic care unit (PACU), however opioid administration in 24 hours after discharge was not recorded for five patients in the MA group, leaving 50 patients remaining for the per-protocol analyses. Secondary outcome data was not recorded for one patient in the placebo group leaving 56 patients remaining for the per-protocol analyses. The mean postoperative opioid needs (Table 2) for patients in the MA group (18.7 ± 13.14) was less than those in the placebo group (22.6 ± 11.15), although this was not statistically significant (p-value = 0.140). Secondary outcomes (Figure 2A) demonstrated a significant reduction in posterior knee pain postoperatively in the MA group (2.84 ± 2.25) compared to Placebo (3.56 ± 1.97; p-value = 0.0362). There were no significant differences in postoperative pain in the front or sides of the knee. Similarly, there were no significant differences in pruritis (MA: 0.26 ± 0.99 vs. Placebo: 0.696 ± 1.73; p-value = 0.2163), sedation (MA: 5.02 ± 2.29 vs. Placebo: 4.61 ± 2.16; p-value = 0.656), and nausea (MA: 1.16 ± 2.28 vs Placebo: 0.714 ± 1.72; p-value = 0.243) scores (Figure 2B). Conclusions: Multimodal analgesia plus hamstring sheath injection reduces postoperative patient reported posterior knee pain compared to placebo for patients undergoing ACLR using hamstring tendon autograft. However, multimodal analgesia plus a hamstring sheath injection does not reduce postoperative opioid requirements.
