RESUMO
INTRODUCTION: Despite controversial discussions, hip resurfacing at the moment seems to be the most bone-sparing surgical procedure of the femoral bone when implanting hip endoprostheses. Main risks are septic and aseptic loosening and necroses of the coxal end of the femoral bone mainly influenced by the periprosthetic allocation of bone cement. Because of a lack of radiation transparency of the hip resurfacing implant, this cement allocation cannot be sufficiently evaluated by common radiological procedures. A pilot study was conducted to describe and validate the macromechanical interdigitation of bone cement with spongy bone of anatomic specimens compared to artificial bone models and to evaluate whether artificial bones may be used for further interdigitation studies of different implantation techniques. METHODS: Plastic models of polyoxymethylene (POM) according to the inside geometry of the Metasul Durom hip prosthesis were implanted on ex vivo femora (n = 14) versus artificial bone models (n = 24) (Sawbones) of three different spongy densities (0.16; 0.20; 0.32 g/cm(3)) (each n = 8) in a clinically standardised surgical procedure and reproduced by highly resolving computed tomography. Afterwards a computer-based analysis of the cement allocation was accomplished. RESULTS: It could be shown that the Sawbones of the lower spongy densities (0.16 and 0.20 g/cm(3)) were similar to the ex vivo femora regarding the bone penetration of cement. No significant differences could be shown regarding interdigitation. According to our data, both groups of Sawbones may be used for further studies.