Analgesic Benefits of Genicular Nerve Blocks of the Posterior Knee for Patients Undergoing ACL Reconstruction

Analgesic Benefits of Genicular Nerve Blocks of the Posterior Knee for Patients Undergoing ACL Reconstruction

Analgesic Benefits of Genicular Nerve Blocks of the Posterior Knee for Patients Undergoing Anterior Cruciate Ligament (ACL) Reconstruction

Outpatients scheduled to have ACL surgery typically receive a femoral nerve block to provide analgesia for the front of the knee. Postoperatively, these patients will often report pain in the back of the knee. Local anesthetic infiltration of the posterior aspect of the knee results in blockade of the genicular nerves of the posterior knee. These nerves originate off of the tibial and common peroneal nerves and their blockade will result in improved posterior knee pain relief and may decrease narcotic consumption compared to patients who receive the same infiltration with normal saline.

Femoral nerve blocks are commonly used to provide postoperative analgesia for ACL surgery. The limitation of these blocks is the incomplete analgesia they provide of the knee joint subjecting the patient to posterior knee pain. As a result, some of these patients receive rescue sciatic blocks in the postoperative care unit to cover posterior knee pain. The sciatic block provides excellent analgesia for the posterior knee; however its blockade invariably affects other territories of the sciatic nerve such as the lower leg and foot. For ACL surgery, the loss of sensation and/or motor strength to this area is unnecessary and may make ambulation more difficult. The ability to ambulate with minimal assistance may be more important for a patient undergoing an outpatient surgery when compared to an inpatient surgery. At the posterior knee, the sciatic nerve branches off into the tibial and common peroneal nerves which give rise to sensory fibers that innervate the posterior knee. We propose targeting these terminal fibers in the popliteal fossa by infiltrating local anesthetic between the distal femoral shaft and popliteal artery thereby providing posterior knee analgesia without affecting the lower leg.This application of this block has not been studied in patients having ACL surgery. A single interim analysis is scheduled after the data for 50 cases are available.

Ultrasound guided posterior genicular nerve infiltration with 30mL of Bupivicaine 0.20% with epinephrine 1:300,000 (Study Drug)

Ultrasound guided posterior genicular nerve infiltration posterior knee with 30mL of preservative free normal saline

Ultrasound guided posterior genicular nerve infiltration posterior knee with 30mL of preservative free normal saline

Numeric Rating Scale (NRS) (NRS pain scores; 0 = no pain,10 = excruciating pain) in the back of the knee recorded every 4 hours up to 24hrs following surgery. Pain Bruden scale ranges from 0 (no pain) to 240 (extreme pain). For example, pain burden of 120 is equivalent to a NRS score of 5 out of 10.

Quality of recovery (QoR15) is a questionnaire that asks 15 questions regarding how the participant has felt in the last 24 hours. Each question is followed by an 11-point numerical rating scale (0 = "none of the time" to 10 = "all of the time"; maximum score 150). The higher the QoR15 total score, the worse the quality of recovery reported.

Inclusion Criteria: patients who are presenting for ACL reconstruction candidates for peripheral nerve blocks patients ASA 1-3 Exclusion Criteria: Patient refusal ASA Classification of 4 or higher Pre-existing neuropathy in the femoral or sciatic distribution Coagulopathy Infection at the site Non-English speaking or non-reading patients Chronic opioid use (>3months) Pregnancy Any other contra-indication to regional anesthesia Failed femoral nerve block Sciatic nerve block placed due to severe pain not managed by intravenous and oral agents.