Ultrasound-guided diagnostic IPACK as a valuable tool in the management of a patient with soleal sling syndrome: a doubly rare case report.

ABSTRACT

This article describes the use of an infiltration between the popliteal artery and capsule of the knee joint (IPACK) to diagnose an entrapment neuropathy of the tibial nerve (TN) in a patient presenting with chronic neuropathic pain in the medial posterior compartment of the left knee, with a previous electromyography showing no evidence of tibial or common peroneal nerve neuropathy. After a positive sciatic nerve block, the patient was evaluated for a TN block, cancelled due to the presence of an abnormal leash of vessels wrapping around the nerve. For this reason, the patient was submitted to a diagnostic IPACK. A negative IPACK suggested that a compression of the TN at the popliteal fossa was the most likely source of the symptoms. After surgical decompression of the TN nerve at the popliteal fossa, the patient's symptoms decreased substantially.

Lay abstract This case report describes the use of an infiltration between the popliteal artery and capsule of the knee joint (IPACK), a technique in which local anesthetic is injected between the popliteal artery and the back side of the knee joint, to diagnose a compression of the tibial nerve (TN) in a patient with chronic knee pain. A female adult patient presented for further evaluation of chronic pain in the inner side of the back of her left knee. A previous electromyography showed no evidence of tibial or common peroneal nerve disease. After a positive diagnostic block of the left sciatic nerve, the patient was evaluated for a left TN block, so as to ascertain whether a compression of this nerve at the back side of the knee could be the origin of the patient's symptoms. During the ultrasound scanning of the TN, a group of abnormal vessels was found wrapping around the nerve, which made it impossible to inject the TN in a safe manner, even with the guidance of ultrasound. For this reason, the patient was instead submitted to a diagnostic left IPACK. A negative IPACK suggested that a compression of the TN at the popliteal fossa, the region behind the knee joint, was the most likely source of the patient's symptoms. After surgical decompression of the TN at the popliteal fossa, the patient's symptoms decreased substantially.