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). Almost 30% of the stems showed significant osteolysis, mainly in the proximal stem area. The amount of osteolysis correlated significantly to a typical pain pattern: dull, circular, and occurring at rest. Six stems had already been 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. Two factors seem to play a role in early loosening of cemented titanium alloy stems: i) increased elasticity of titanium, which leads in small stem sizes to micromotion between the stem and cement and to cement breakage, and ii) corrosion of the cemented titanium alloy stem and subsequent osteolysis in the adjacent bone. The combination of both factors (high elasticity plus corrosion) accelerates the degradation of the bone anchorage of the stem and initiates early loosening. We advise against the further use of cemented SLS-88 titanium alloy stems.