Patient-controlled bupivacaine infusion into the infrapatellar fat pad after anterior cruciate ligament reconstruction

Purpose: The goal of the study was to determine the safety and analgesic efficacy of a patient-controlled infusion pump that dispenses bupivacaine extra-articularly to the infrapatellar fat pad after anterior cruciate ligament (ACL) reconstruction with ipsilateral bone-patellar tendon-bone autogenous graft. Type of Study: Prospective clinical study. Methods: Twenty-one consecutive patients were enrolled in the study. After surgery, the catheter of a bupivacaine infusion pump was implanted extra-articularly onto the infrapatellar fat pad. Ten patients were given infusion pumps with 50 mL of 0.5% bupivacaine to be self-administered for analgesia. Eleven patients were given infusion pumps with 50 mL of 0.25% bupivacaine. Opioid analgesics were available if patients were unable to control the pain solely with the bupivacaine pump. Historic controls consisted of 62 consecutive patients who underwent ACL reconstruction before study initiation. Patients recorded volumes of self-administered bupivacaine; also recorded were postoperative pain levels using a visual analog scale (VAS). Opioid analgesic usage was measured and compared with historic controls. Results: Amount of bupivacaine infused and VAS recorded pain levels were not significantly different between the 0.5% and the 0.25% bupivacaine groups. Opioid analgesic usage was significantly reduced when the 0.5% bupivacaine group was compared with historic controls (mean morphine equivalents via intramuscular route: 0.5% group, 17.6 mg; historic controls, 66.4 mg; P = .015). This was also significant when normalized by patient weight (0.5% group, 0.227 mg/kg; historic controls, 0.880 mg/kg; P = .023). Opioid usage in the 0.25% group (35.7 mg and 0.540 mg/kg) was also less than historic controls; however, this was not statistically significant. Conclusions: Infrapatellar fat pad infusion with 0.5% bupivacaine may provide enhanced analgesia after ACL reconstruction with ipsilateral bone-patellar tendon-bone autogenous graft. A double-blinded, randomized control trial with a greater number of patients is required to confirm these findings.