Abstract
Objectives
The anteversion angle of the cup is important for achieving the stability and avoiding the dislocation after total hip arthroplasty (THA). We place the component considering with the change of inclination of pelvis with its posture change. We analyzed the perioperative pelvic inclination angles with posture change and the time course.
Materials and Methods
We treated 40 hips in 40 patients (9 males and 31 females) with cementless THA that were performed from January 2007 to December 2008 in our hospital. 30 osteoarthritis hips, 3 rheumatoid arthritis hips and 7 idiopathic osteonecrosis hips were included. All patients were performed THA with VectorVision Hip 2.5.1 navigation system (BrainLAB, Feldkirchen, Germany). We used AMS HA cups and PerFix stems (KYOCERA Medical co., Osaka, Japan). The mean age of surgery was 59 years old (35–79 years old). The pelvic inclination angles (PIA) were measured with anteroposterior radiographic image in accordance with the Doiguchi's method.
Results
The amount of change of the pelvic inclination angle between supine and standing position was 0.6 degrees prior to surgery, 0.7 degree at 1 year after surgery and 2.3 degrees at 3 years after surgery. 7 patients prior to surgery, 7 patient at 1 year after surgery and 13 patient at 3 year after surgery changed more than 5 degrees between supine and standing position. The pelvic inclination angles of 23 patients prior to surgery, 19 patients at 1 year after surgery and 29 patients at 3 years after surgery changed in the retroverted direction with posture change. It tended to increase after surgery.
Discussion and Conclusions
When we place the acetabular component, it is important that the pelvic inclination angle in supine position according to preoperative planning and the change of pelvic inclination angle with posture change. The amount of change of PIA tended to increase at 3 year after surgery compared to 1 year after surgery. Moreover, we experienced some patients the amount of change of pelvic inclination angle between supine and standing position changed more than 10 degrees. If the pelvic inclination angle changes widely, it requires more attention because of a narrow safe margin for placing the acetabular component.
