Iliopsoas cyst causing persistent pain after total hip arthroplasty

Persistent pain after total hip arthroplasty (THA) has many potential causes. The most common are aseptic loosening, infection, and heterotopic ossification. Irritation of the iliopsoas tendon due to the acetabular component is an underestimated cause of persistent groin pain and functional disability after THA with rare incidence. Pain specific to iliopsoas tendonitis includes activities such as hyperextension of the hip, forced flexion, and activities of daily living (eg, ascending stairs). This article presents a case of a 50-year old man with clinical and radiological signs of osteoarthritis of the right hip joint. A THA was performed. After a symptom-free interval of several weeks postoperatively, the patient reported pain projecting from the right groin and radiating ventromedially along the leg. Magnetic resonance imaging of the hip showed a fluid-filled cyst in anatomical proximity to the femoral nerve causing an iliopsoas tendonitis. The patient underwent surgical resection of the cyst was performed by an anterior approach; a conjunction to the hip joint was not present. The implanted components of the prosthesis showed good osseointegration with no signs of loosening. The cyst was removed and the iliopsoas tendon was released. A few weeks after the operation, the patient was pain free. At 17-month follow-up, no problems were reported. In cases such as this, finding the correct diagnosis may be difficult and misleading. Conservative and operative therapeutic options are discussed and compared with divergent findings in the literature.