Malposition of the acetabular component during hip arthroplasty may cause impingement, dislocation, long-term wear and loosening. Positioning of the cup is often inaccurate because it is difficult to know precisely the orientation of the pelvis in the lateral decubitus position. Therefore, we examined changes of pelvic orientation with lateral patient positioning.
Fifty-two hips, in 9 men and 36 women with a mean age of 57.6 years, were studied. In all cases, a posterolateral approach was employed in a lateral decubitus position. As positioning devices, a pelvic positioner was used for 32 hips, and a“magicbed”for 20 hips. Anteroposterior pelvic radiographs were taken in supine position before surgery and in lateral position during surgery. Three different parameters, lateral tilt, internal rotation, and flexion of the pelvis, were measured and compared between the pelvic positioner and the“magicbed”.
Lateral tilt of the pelvis in a lateral decubitus position was correlated with patient's weight and body mass index. Internal rotation of the pelvis was controlled by the pelvic positioner better than by the “magicbed”. Flexion of the pelvis was slightly decreased by the pelvic positioner.
It is important to know how pelvic orientation is influenced by a patient's build and positioning devices to achieve better alignment of the cup.
