Migration of the femoral stem in hip arthroplasties. Analysis of associations with structural, radiological and follow-up variables.

Medical and/or distal migration of the prosthetic stem was found in 63 out of 337 patients (19 per cent) treated surgically with a Christiansen hemiprosthesis, a Christiansen total hip prosthesis or a Charnley total hip prosthesis. Fractured bone cement, radiolucent zones at the cement/bone interface, resorption of the femoral calcar and cortical sclerosis were all associated with migration. Varus position of the Christiansen total hip prosthesis was significantly associated with medical migration, and a short stem was significantly associated with distal migration. The other structural variables could not be linked with migration. Distal migration was pain-inducing and was significantly associated with late infection. Medical migration had a less distinct association with pain, and was not correlated with infection. Both medical and distal migration were time-dependent, and 4 or more years after operation about 2.5 per cent of the prosthetic stems had migrated.