Posterior capsule injection of local anesthetic for post-operative pain control after ACL reconstruction: a prospective, randomized trial.

Purpose: Alternative modalities to optimize pain control after anterior cruciate ligament reconstruction (ACLR) are continually being explored. The purpose of this study was to compare femoral nerve block (FNB) only vs FNB with posterior capsule injection (PCI) of the knee for pain control in patients undergoing ACLR.

Methods: Patients undergoing primary ACLR were randomized to receive either FNB only or FNB with PCI. Following surgery, patient's pain was evaluated in the postoperative care unit (PACU) and at home for 4 days. Pain levels were measured via visual analog scale (VAS) and calculating opioid consumption. Outcomes of interest included postoperative pain levels and opioid consumption.

Results: A total of 42 patients were evaluated, with 21 patients randomized to each study arm. Outcomes showed significant pain reduction in both anterior and posterior knee VAS scores in the PACU in those that received PCI (anterior VAS: 39.6 vs 21.3 (SD = 12.9), p < 0.01; posterior VAS: 25.4 vs 15.3 (SD = 8.05), p = 0.01). Moreover, the PCI group also showed significantly less opioid consumption compared to FNB only (23.5 vs 17.4 pills, p = 0.03). There were no differences found in pain scores between groups in home VAS sores.

Conclusions: These finding suggest the use of arthroscopically assisted injection of local anesthetic to the posterior capsule of the knee significantly reduces early post-operative pain and dramatically reduces the number of opoid medication taken after ACLR.

Level Of Evidence: Prospective, randomized, control trial, Level I.