Acetabular component orientation in 834 total hip arthroplasties using a manual technique.

UNLABELLED: Acetabular component orientation during total hip arthroplasty affects dislocation, range of motion, polyethylene wear, pelvic osteolysis, and component migration. New total hip arthroplasty navigation systems have been introduced to avoid the errors reported after acetabular component orientation using a manual technique. We investigated acetabular component orientation in 834 consecutive primary total hip arthroplasties performed by one surgeon using a manual technique. We examined the relationship between dislocation and a defined safe range. Vertical tilt and planar anteversion were 44.4 +/- 6.5 and 17.9 +/- 6.3 (mean +/- standard deviation), respectively. The error of vertical tilt and planar anteversion were 5.2 +/- 3.9 and 5.3 +/- 4 (mean +/- standard deviation), respectively. Two hundred thirty-three of 834 hips (27.8 %) were outside the safe range. Logistic regression analysis showed that patients with Group IV class according to the classification system of Crowe et al and right hips had a greater risk of being outside the safe range. Navigation systems should be considered, especially in patients with highly dislocated hips. We found no relationship between risk of dislocation and the safe range. Factors other than acetabular component orientation also might affect dislocation. LEVEL OF EVIDENCE: Prognostic Study, Level IV (case series).