ABSTRACT
Uncemented hip stems are advantageous for the lack of risk related to fatigue failure of the cement mantle. Their main problem is primary stability, which is necessary to guarantee osteointegration. A new fixation concept was developed for a partially cemented stem (Cement Locked Uncemented, CLU), derived from an anatomic uncemented pressfit stem (AncaFit, Cremascoli, Italy). To improve the primary stability, the stem was modified machining two pockets for cement injection in the lateral-proximal area. The CLU stem was found to be significantly more stable than a press-fitted AncaFit stem. Micromotion recorded in the cemented type was comparable with that for the CLU. At the same time, the FEM 78analysis confirmed that the CLU design does not induce excessive stresses in the surrounding cement. The CLU stem thus opens a new way to reach primary fixation for cementless stems.
