Dislocation After Total Hip Arthroplasty Causes and Prevention

TLDR

The study developed a standing‑position acetabular‑placement technique using pelvic bony landmarks to prevent impingement and dislocation, defining a safe cup position of 30–50° abduction and 20–40° flexion. The technique uses a standing lateral preoperative radiograph with the X‑ray tube centered over the trochanter to position the cup, and a standing true lateral postoperative film to measure cup flexion reproducibly within 10°, requiring no special instruments. Among 441 posterior‑approach THAs performed from 1984 to 1988, the dislocation rate was 1.14%, dropping to zero in 1989.

Abstract

In this prospective study, a technique of positioning the acetabulum by bony landmarks of the pelvis in the standing position was developed using a standing lateral preoperative roentgenogram with the X-ray tube centered over the trochanter. Since 1984, 441 total hip arthroplasties (THAs) were done through the posterior approach with a 1.14% dislocation rate through 1988 and no dislocations in 1989. To prevent impingement and dislocation, it was determined that the safest range for cup position was 30 degrees-50 degrees abduction and 20 degrees-40 degrees flexion from the horizontal. To measure postoperative cup position, a standing true lateral roentgenogram of the operated hip allowed direct measurement of cup flexion and was reproducible within 10 degrees. No special instruments are necessary for this technique, which can be used with any THA system.