Early migration of uncemented porous coated anatomic femoral component related to aseptic loosening.

Primary total hip arthroplasties were performed in 108 patients (116 hips) using a porous coated anatomic (PCA) hip system. Nineteen (22 hips) of 108 patients (116 hips) who had a subsidence of a PCA femoral stem more than 3 mm were studied for the time onset, the amount of stem subsidence, and outcomes. A minimum follow-up period was seven years. The average age of the patients at operation was 37.4 years. The operative diagnosis was avascular necrosis of femoral head in seven hips; osteoarthrosis secondary to childhood septic hip joint in six; fracture of femoral neck in three; and miscellaneous in six hips. The average preoperative Harris hip score was 57 points, which improved to 82 points at the seven-year follow-up examination. Overall, there was a 79% prevalence of thigh pain (15 patients). Six patients had occasional, nondisabling, activity-related thigh pain. The remaining nine patients had persistent and disabling thigh pain at the final follow-up examination. All stems had an undersized component in one or both planes. One hip was stabilized by bone ingrowth. Twelve hips were fixed by fibrous tissue ingrowth and had occasional clinical symptoms. Nine hips had component loosening at the final follow-up examination, of which four were revised and five were pending revision. Early instability of the femoral component measured by radiographs was correlated with and predictive of late radiographic loosening of the femoral component.