Sciatic nerve compression by an extrapelvic cyst secondary to wear debris after a cementless total hip arthroplasty: A case report and literature review.

INTRODUCTION: Polyethylene (PE) wear debris after total hip arthroplasty (THA) may cause formation of a soft tissue mass due to inflammatory reaction. To the best of our knowledge we report the first case in whom the diagnosis was made after examination of the hip, pelvis and lumbar spine with detailed radiological methods and the plain radiographs showed no signs of loosening of the THA. PRESENTATION OF CASE: We report a 52 years-old woman who presented with a cyst causing sciatic irritation in her gluteal region due to wear debris after THA. Magnetic resonance imaging (MRI) was useful in detecting the cyst. Resolution of the cyst occured after subtotal cystectomy and revision of the acetabular components. DISCUSSION: Although plain radiographs can show signs of the underlying pathology; such as osteolysis, loosening of the components and wear of the PE liner, they are unable to detect cystic lesions. Cystic lesions may be an early sign of wear debris.
CONCLUSION: This case shows us that sciatic neuropathy with no evidence of nerve root impingement on lumbar MRI in a patient with THA requires also examination of the hip and pelvis with detailed radiological methods, such as MRI, in addition to plain radiography. Removal of the source of debris via revision surgery following subtotal cystectomy leads to the resolution of the remaining portion of the cyst and also relief of the symptoms of sciatic nerve compression.