Lateral Femoral Cutaneous Nerve Entrapment by Hip Arthroplasty Scar Tissue

Case Diagnosis: 34-year-old male with bilateral hip avascular necrosis who developed meralgia paresthetica as a complication of right total hip arthroplasty

Case Description or Program Description: The patient underwent anterior approach right total hip arthroplasty (THA) due to avascular necrosis. Post-operatively, he developed burning pain, numbness, and tingling on the right anterolateral thigh. Symptoms did not respond to conservative treatment. Patient was referred to PM&R clinic by Plastic Surgery for diagnostic femoral nerve block proximal to the inguinal ligament, which provided transient relief. Diagnostic ultrasound showed lateral femoral cutaneous nerve (LFCN) enlargement near the anterior superior iliac spine. Further workup with MRI confirmed entrapment of the LFCN at the level of the proximal sartorius and tensor fascia lata by extensive post-surgical scarring. Although nerve conduction studies were unremarkable, clinically the patient’s case remained consistent with meralgia paresthetica.

Setting: Tertiary Care University Hospital

Assessment/Results: The patient returned to PM&R clinic for ultrasound guided LFCN block at the level of the visualized scar tissue. He had 50% relief of proximal thigh pain. An additional LFCN block was performed distal to the scar tissue for persistent mid and distal thigh pain. Given inadequate relief, patient underwent LFCN neurolysis, nerve allograft wrap, and intramuscular burying of the nerve end with Plastic Surgery.

Discussion (relevance): Neuropathy is a rare but acknowledged complication of THA. Determining the precise etiology of neuropathy after THA can be challenging. This case is unique in that imaging elucidated LFCN entrapment within scar tissue as the etiology.

Conclusions: The PM&R clinician is uniquely situated to utilize a wide range of diagnostic technologies from real-time imaging with ultrasound, static imaging with MRI, and diagnostic nerve block. All of the above tools helped elucidate the cause of this patient's post-operative meralgia paresthetica and direct the patient towards definitive treatment.