While measurement repeatability of individual pelvic radiographic parameters has already been evaluated, there have been no reports on the repeatability of biomechanical computations from such measurements. The aim of our study was to evaluate the repeatability of computations of the resultant hip force and the peak contact hip stress from seven pelvic radiographic parameters in adult dysplastic hips.
We performed a retrospective analysis of 18 nonoperated adult dysplastic hips with a series of three anteroposterior pelvic radiographs for each hip. The participants were adult patients treated with unilateral Bernese periacetabular osteotomy at our institution in the years 1987–1995, and only their nonoperated hips without osteoarthritis were included. Radiographic measurements and biomechanical computations were performed with the previously developed HIPSTRESS method on each of the three radiographs for each individual, and repeatability was assessed with the intraclass correlation coefficients.
We found high repeatability of the measured Wiberg center-edge angle, pelvic width, the horizontal coordinate of the abductor insertion point on the greater trochanter, intermediate repeatability of the interhip distance and low repeatability of the femoral head radius, pelvic height and the vertical coordinate of abductor insertion point on the greater trochanter. The intraclass correlation coefficients of the resultant hip force and the peak contact hip stress were 0.88 and 0.94, respectively.
The repeatability of biomechanical computations from pelvic radiographic measurements is comparable to the repeatability of the present methods for assessment of hip dysplasia.