[Deformations of acetabulum with load before and after prosthetic implantation. An experimental study by extensometry].

Using fresh cadavers pelves, an experimental model of unipodal stance was performed. The skeleton (femurs, pelvis and 2 lumbar vertebrae) was connected to the machine by non constrained junctions. Muscles (gluteus, iliacus and rectus abdominis) were simulated. Using this model, monopodal stance could be maintained under load. Strain measurements were performed on the periphery of the acetabulum. Results showed that periacetabular strains were dependent on the mobility of the lower lumbar intervertebral discs as well as on the type equilibrium (uni or bipodal). It was remarkable that the blockage of intervertebral rotations (experimental lombo-sacral arthrodesis) increased acetabular stiffness. The influence of total hip replacement was also studied. Periacetabular strains remained important around cementless press-fit cups. This would plead for a non weight bearing postoperative period in clinical practice of cementless arthroplasty. Important deformations also persisted around conventional cemented cups, justifying further research to limit periacetabular deformations around total hip prostheses, in the hope of limiting the rate of late acetabular loosening.