Loosening of total hip arthroplasty with a prosthesis employing a skirted femoral head.

In total hip arthroplasty, a modular femoral head with a flange increases the head-neck strength and compensates the leg length, but results in a decreased head-to-neck diameter ratio. Studies have shown increased chance of impingement and incidence of dislocation associated with a skirted femoral head component. However, the relation between implant loosening and the skirted neck has not been well demonstrated. We report a 41-year-old male patient with aseptic loosening of total hip arthroplasty due to osteolysis of both acetabular and femoral components 5 years after surgery. The retrieved prostheses demonstrated polyethylene wear due to impingement of the skirted head during hip flexion. Pathologic examination showed prominent foreign body reaction. Prosthetic impingement occurs due to malposition of components and extreme posture. A decreased head-to-neck diameter ratio further compromises prosthetic range of motion. A skirted femoral head component should be used with caution.