Cadaver analysis of anterior and posterior acetabular horn displacement

Purpose of this study The purpose of this study was to quantify relative di splacement of anterior and posterior horn of the acetabulum lunate surface using Omega strain gauges while increasing loads were applied to the hip jo int. Measurement were performed on fresh cadaver bones in unipodal stance u sing experimental method before and after socket's implantation. Material and methods; Nine skeletons, from fresh non-embalmed cadavers, inc luding pelvis, the three last lumbar vertebrae and both femurs were maintai ned in unipodal. equilibrium using metallic cables for muscle passive simul ation. Loads were applied up to 700 N. Specific extensometric Omega strain gauges were created and tested, with 5 mu of sensibility. Measurement of di splacement between horns were studied on two sides of each pelvic before an d after Implantation of conventional and prototype cemented or press fit im plants. Results Among 81 loads on 18 acetabulum healthy and implanted, displacement was: significant in 58 cases with a spacing of horn of 7 to 140 mu with av erage 31,1 mu and non significant in 25 cases. On healthy acetabulum, spacing was variable from 12 to 140 mu (average 43,2 mu) in 18 of 26 loads. On implanted acetabulum by different sockets, spaci ng was variable from 7 to100 mu (average 27,4 mu) in 40 of 55 loads. Displacement was fonction of rotation hip, smaller in internal rotation and larger in external rotation. Spacing of horns was reduced in oversize sock ets. Discussion The data obtains by omega strain gauge suggest acetabular displa cement is not univocal under load. There were a widening of the acetabular notch on load. This can be explained by the modification Of primary incongr uity of the two components of the hip joint because of acetabular deformati on. Such results are in agreement with recently published data obtained abo ut length of the transverse acetabular ligament.