Mechanism of failure in hips with an uncemented, all polyethylene socket

The outcome of 32 patients with 33 primary total hip replacements performed using noncemented uncoated polyethylene acetabular cups (RM cup) with ceme nted titanium alloy monoblock stems (STH-2 stem) was reviewed. At a mean fo llowup of 6.3 years (range, 6 months-10 years), the failure rate was 57%, m ore than 14 times higher than the rate typically seen with cemented polyeth ylene acetabular cups used with the STH stem. Failure was characterized by rapidly progressive acetabular or femoral osteolytic lesions that resulted in extensive bone loss, often in patients who had no symptoms. In addition to the debris that typically is generated by a metal on plastic bearing cou ple, an abundance of polyethylene particles of submicron size were produced at the cup-bone interface. Tissues retrieved from areas of osteolysis reve aled the presence of intracellular submicron polyethylene particles in macr ophages. It is recommended that patients with no symptoms who have RM nonce mented, uncoated acetabular cups be followed up yearly and undergo early re vision surgery when faced with osteolysis to prevent extensive bone loss.