[A study of primary mooring and deformation of the peri-acetabular area under static load]

We propose a method to study the primary stability and the periacetabular deformation under static load, with and without cemented and cement-free acetabular implants, using a biomechanical model that stimulates the balance mechanism described by Pauwels. The biomechanical model uses whole pelvises of recently frozen corpses. We have imitated the gluteus medius and minimus muscles on the pelvis with cables and pulleys. The loading device comprises a metallic frame, on which a hydraulic press is set up for static testing, and a prototype femoral prosthesis made of two main parts: one on which the gluteal muscles are inserted, and another one on which the femoral head is attached. The pelvis is fixed to the metallic frame by a plate attached to the sacrum and allowing movements in all planes of space. The measurement method utilizes: for primary stability, four transducers, including three three-directional ones, in the three planes of space outside the pelvis, only one being located inside the pelvis with a 16 degrees orientation relative to the vertical; for deformation, a transducer located in three different places in the periacetabular region. We have used ten freshly frozen pelvises with six different implants (two with and four without cement) and eighteen implantations.