New Measurement Method May Help Treat Acetabular Deformities

A method to measure percent coverage of the femoral head by the acetabulum may help provide better guidance for the surgical treatment of acetabular deformities than radiographs alone, according to recent research data.

“If this normative data is accurate, maybe [it] will help define resections, or at least the safe limit, when indicated,” Christopher M. Larson, M.D., said. “There is the potential to use this data to evaluate three-dimensional coverage of patients preoperatively as well.”

Researchers studied 409 hip computed tomography (CT) scans of patients with a mean age of 25.3 years who did not have hip pain, clear lateral dysplasia or profunda deformity. CT scan alignment was corrected along the horizontal and vertical axes while the percentage of acetabular coverage and global surface area coverage were measured three-dimensionally by software mapping of the CT scan. Percent coverage laterally was correlated with the lateral center edge angle (LCEA), and both presence and prevalence of cranial retroversion (cross-over sign) and a positive posterior wall (PW) sign were measured.

Mean global coverage of the femoral head was 40 percent. Local coverage anteriorly was 38 percent, laterally was 67 percent, and posteriorly was 51 percent. Mean femoral head surface area coverage was 40 percent anteriorly, 60 percent superiorly and 48 percent posteriorly. Lateral coverage represented a mean LCEA of 31 degrees. Researchers found that 15.4 percent of hips showed cranial retroversion that correlated with a cross-over sign while 30.3 percent had less than 50 percent posterior coverage that correlated with a positive PW sign. Male hips had a higher prevalence of cross-over (19.2 percent vs. 11.2 percent) and PW signs (46 percent vs. 13.3 percent) than female hips.

“This might better define when to consider rim resections, fixation versus resection of rim fractures, for instance, or when to consider a pelvic osteotomy,” Larson said.