High variability in pelvic orientation in the lateral decubitus position negatively affects acetabular component placement.

PURPOSE

Determine factors that impart increased risk of acetabular component malposition in the lateral decubitus position.

METHODS

A retrospective review of 813 X-rays from posterior THA procedures at a single institution. Pelvic tilt and rotation were measured on preoperative standing AP-pelvis and intraoperative cross-table x-rays. Proper intraoperative pelvic orientation (PPO) was defined as vertical tilt and axial rotation within ± 15° of the preoperative standing pelvis orientation. Acetabular abduction was measured on standing postoperative x-rays with Goal abduction (GA) of 30-50°.

RESULTS

PPO was obtained in 284/413 cases (69 %). Patient sex, weight, BMI, and operative laterality were not significantly associated with PPO. Patients with PPO were shorter (1.68m vs 1.72m, p < 0.01). PPO occurred in 168/221 patients (76 %) with the Capello or Wixson hip positioner, compared to 116/192 (60 %) with the De Mayo positioner (p < 0.01). GA was obtained in 249/284 (88 %) of patients with PPO, as compared to 103/129 (80 %) patients without PPO.

CONCLUSION

The risk of pelvic malpositioning significantly increases with the use of certain hip positioning systems, and taller patients. Acetabular component abduction is negatively affected by an improperly positioned pelvis.