Accuracy of Ultrasound‐Guided Localization of the Peripatellar Plexus for Knee Pain Management

Abstract

IntroductionPain associated with arthritis of the knee and its ultimate treatment, total knee arthroplasty, can be considerable and has historically been addressed with a variety of treatment modalities including an emphasis on opioid usage for severe pain. While opioids provide effective pain relief, they have many unwanted side effects including nausea, vomiting, constipation, urinary retention, mental status changes, and respiratory depression. Alternatively, patients experiencing knee pain have benefited from anesthetization through cryoneurolysis of the cutaneous nerves of the anterior thigh and knee that contribute to the peripatellar plexus. The purpose of this study was to assess the accuracy of ultrasound‐guided localization of the peripatellar plexus on cadaveric lower extremities.Materials and MethodsUltrasound was used to locate the anterior femoral cutaneous nerve (AFCN), the infrapatellar branch of the saphenous nerve (IPSN), and the lateral femoral cutaneous nerve (LFCN) in the right and left lower extremities of two female and three male, lightly embalmed anatomical donors. Upon identifying a potential candidate, methylene blue was injected under ultrasound guidance. Confidence of identification for each site was scored as low, medium, or high at the time of injection based upon the clarity and difficulty in locating each of the cutaneous nerves via ultrasound. The three points of injection for each limb ware marked, and blunt dissection subsequently used to confirm the identification of each structure. A successful attempt was defined as MB staining directly within the nerve epineurium and an unsuccessful attempt was defined as MB staining of the subcutaneous loose connective tissue with no direct staining of nerve epineurium.ResultsIn total, 30 injection sites were analyzed. High confidence was reported 60% (18/30) of the time, medium confidence was reported 23.3% (7/30) of the time, and low confidence was reported 16.7% (5/30) of the time. All five of the reports of low confidence were associated with IPSN injections. Dissection revealed successful injections in 90% (27/30) of the injection attempts, and unsuccessful injections in 10% (3/30) of the attempts. All three unsuccessful injection attempts were associated with IPSN injections and resulted in staining of the great saphenous vein.DiscussionDependency and addiction that can occur with chronic opioid use have been brought to the national forefront in what is now considered to be an “Opioid Crisis”. To reduce the dependence on opioids, multimodal approaches to pain including cryoneurolysis have been advocated. This study confirmed the accuracy of ultrasound‐guided localization of cutaneous nerves of the peripatellar plexus. Improving the precision in identifying these nerves is crucial in reducing patient morbidity, treatment times, and associated treatment costs.Support or Funding InformationThis work was supported by Myoscience A. Ultrasound location of the AFCN within the subcutaneous loose connective tissue of the thigh, just superficial to the fasciae latae and quadriceps muscles. B. Injection of methylene blue into AFCN via ultrasound guidance.imageA. Ultrasound location of the AFCN within the subcutaneous loose connective tissue of the thigh, just superficial to the fasciae latae and quadriceps muscles. B. Injection of methylene blue into AFCN via ultrasound guidance.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.