Abstract
Aims: Clinical studies have revealed issues with residual particles from roughening processes on the surface of cementless stems. A new stem was therefore developed to achieve optimal primary stability in the femur but with a rough contamination-free surface for osteo-integration. Methods: TMZF, a new high strength and low modulus beta-titanium alloy was chosen for the stem to achieve optimal osseous integration. Several methods to achieve the goal of a rough and contamination free surface have been evaluated and documented by laser proþlometry, SEM and EDAX. Prototypes of the stem with different edge radii were implanted into human cadaver femora and tested with respect to their rotational stability. Early clinical experience was collected on the þrst 280 cases with currently short-term follow up. Results: With TMZF¨ a smaller neck diameter is possible, giving increased range of motion. With an improved process the required surface roughness and pattern for osteo-integration was achieved without any residual contaminants. Stems with a decreased radius of the edges of this rectangular design were less stable in the cadaver tests than those with sharp edges and the stem is manufactured accordingly. Conclusions: A straight stem (Hipstarª) with sharp edges made from a high performance titanium beta-alloy, reduced neck diameter and non contaminated rough surface, has been developed and tested in vitro and in vivo. A multicentric prospective clinical study has been initiated to conþrm the advantages of this innovative stem.
Theses abstracts were prepared by Professor Dr. Frantz Langlais. Correspondence should be addressed to him at EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
