Effects of Spinopelvic Balance on Acetabular Version in Total Hip Arthroplasty

The orientation of acetabular component is influenced by pelvic tilt, body position and individual variation in pelvic parameters. Most adverse events attribute to improper positioning of the acetabular component in the functional position. There is evidence that the orientation of the pelvis changes from the supine to standing position, consequently changing the orientation of acetabular cup version. This article substantiates the influence of pelvic tilt, incurred from a sagittal deformity of spine, on the dynamic orientation of the acetabular cup which was positioned in accordance with the anatomic landmarks alone. If the reference is only the bony architecture and the dynamic positions of the pelvis are not taken into account, improper functional orientation of the acetabular cup can result in sitting and standing positions. These can induce instability even in anatomically appropriately oriented acetabular component. The sagittal position of pelvis being a key factor in impingement and dislocation after total hip arthroplasty, its tilting affects the position of acetabular component in the sagittal plane of the body as compared with its anatomic position in the pelvis. Therefore we suggest a preoperative lateral view of spine-pelvis, in upright and supine position for evaluation of a corrective adaptation of the acetabular cup accordingly with pelvic balance.