Osteolysis in cemented titanium alloy hip prosthesis

We evaluated 132 consecutively implanted cemented titanium alloy stems (Ti6 -Al7-Nb, SLS-88) after a mean follow-up of 6.6 years (range 5-7 years). Alm ost 30% of the stems showed significant osteolysis, mainly in the proximal stem area. The amount of osteolysis correlated significantly to a typical p ain pattern: dull, circular, and occurring at rest. Six stems had already b een revised, and another 7 stems were loose clinically and radiologically, which resulted in a Kaplan-Meier survivorship of 95% for stem revisions and 88% for stem failures (revisions plus loose stems). We found that smaller stem sizes tend to increase the development of osteolysis and loosening. Tw o factors seem to play a role in early loosening of cemented titanium alloy stems: i) increased elasticity of titanium, which leads in small stem size s to micromotion between the stem and cement and to cement breakage, and ii ) corrosion of the cemented titanium alloy stem and subsequent osteolysis i n the adjacent bone. The combination of both factors (high elasticity plus corrosion) accelerates the degradation of the bone anchorage of the stem an d initiates early loosening. We advise against the further use of cemented SLS-88 titanium alloy sterns.