Double Crush Syndrome of the Lower Limb with L3 Radiculopathy and Femoral Nerve Palsy after Total Hip Arthroplasty: A Case Report

Case Diagnosis: Double Crush Syndrome

Case Description or Program Description: A 48-year-old female patient sought care for ongoing right hip and groin pain with radiation down the anterior thigh. Within the last year, the patient had total hip arthroplasty (THA) via posterior approach with orthopedic surgery. The patient noted reduced pain initially after surgery but worsened weakness in hip and knee flexion. Due to ongoing disability, nerve conduction study (NCS), electromyography (EMG) and lumbar MRI were recommended.

Setting: Physical Medicine and Rehabilitation Clinic

Assessment/Results: Electrodiagnostic findings included decreased amplitude of right saphenous nerve response and needle EMG findings showing chronic MUAP changes with decreased recruitment in the right iliopsoas, vastus lateralis and medialis. MRI lumbar spine showed a perineural cyst at the right L3-L4 neuroforamen.

Discussion (relevance): Femoral nerve palsy after THA is a rare complication, ranging from 0.08% to 7.6% occurrence which may develop because of direct nerve compression via traction, hematomas or damage such as laceration, ischemia or thermal spread injuries. Perineural (Tarlov) cysts can be found in the lumbosacral spine, about 1.5 to 4.6% with approximately 20% being symptomatic. Physical exam, electrodiagnostic and imaging findings suggest this patient's weakness may be due to femoral nerve injury in addition to a nerve root injury at L3-L4 resulting in double crush syndrome.

Conclusions: Femoral neuropathy after THA and Tarlov Cysts in the lumbar spine are uncommon but together can lead to double crush syndrome confirmed by electrodiagnostic evidence as seen in this patient. The patient may have had pre-existing nerve root compression and with traction during surgery lead to impaired function. This is a known risk factor for nerve palsy post THA. Electrodiagnostic studies and MRI are valuable tools in the accurate diagnosis of neuropathic complications after THA.