Occurrence of Femoral Nerve Palsy After Total Hip Arthroplasty (THA) Using the Direct Lateral Approach.

Femoral nerve palsy (FNP) is a rare but serious complication after total hip replacement (THP). Despite its rarity, FNP can significantly impact patient recovery and quality of life. This case report examines the occurrence of FNP in a patient following a primary THP and highlights the importance of surgical technique and postoperative detection and its management. We present the case of a 38-year-old male with a history of microscopic polyangiitis on long-term steroid treatment, who developed FNP following THP. The patient was admitted with non-traumatic right hip pain with osteoporotic fracture of the femoral head and underwent elective THP. Postoperatively, the patient showed quadriceps weakness and related sensory deficits. Postoperative assessments included physical examination, electromyography (EMG), nerve conduction studies (NCS), and magnetic resonance imaging to assess the extent of the nerve injury. EMG and NCS confirmed severe femoral mononeuropathy with profound active denervation changes. A subsequent magnetic resonance imaging revealed atrophy of the right sartorius and quadriceps femoris muscles. Conservative management was decided, including physiotherapy and close follow-up, which led to significant gradual improvement over six months, with enhanced knee range of motion (ROM), increased quadriceps strength, and improved sensation on the medial side of the leg and foot. Femoral nerve injuries, although uncommon, pose significant risks in THP. Excessive retraction during surgery may contribute to these injuries. Early diagnosis, conservative management, and interdisciplinary coordination are crucial to achieve optimal recovery.