Abstract
INTRODUCTION
Acetabular cup orientation is an important element of Total Hip arthroplasty (THA). The purpose of this retrospective case-control study was to compare variability of acetabular cup placement between THA performed via Direct Anterior Approach (DAA) with fluoroscopy in supine position and posterior approach (PA) in lateral position without use of fluoroscopy.
METHODS
Radiographic and clinical records of THAs performed by a single, high volume arthroplasty surgeon at one institution were reviewed. Patients with similar design of uncemented acetabular cup, femoral component and bearing surface were included to form two groups. PA group consisted of 300 THAs performed from May 2006 to June 2009. DAA group consisted of 300 THAs performed from Oct 2009 to Oct 2011 excluding first 100 cases to eliminate the influence of learning curve. Radiographic analysis was done by two independent blinded observers to determine cup inclination and anteversion (Liaw et al) on standardized, 6 week postoperative, standing anteroposterior pelvic radiographs using Picture Archiving and Communication System software (PACS).
RESULTS
Both groups were comparable in terms of age, sex and BMI. Mean inclination in both groups was similar; PA (41.2 degrees; range, 23 to 63) and DAA (40.36 degrees; range, 29 to 51). Mean anteversion was lower in DAA group (13.29 degrees; range, 6.2 to 32) as compared to PA group (24 degrees; range, 2.3 to 48.8). Variances for cup inclination (49.7 PA vs 19.1 DAA) and anteversion (75.1 PA vs 16.1 DAA) were significantly lower in the DAA group as compared to the PA group as per the F- test for equality of variances (p = 0.001).
DISCUSSION
Acetabular cup placement in PA relies predominantly on internal landmarks. Utilization of fluoroscopy with supine position during DAA THA helps in intraoperative assessment of cup orientation and making adjustments for pelvic tilt, thus resulting in decreased variability.
