Summary
Objective: To evaluate the inter- and intra-observer variability in measurement of the angle
of lateral opening (ALO) and version angle measurement using digital radiography and
computed tomography (CT).
Methods: Each hemipelvis was implanted with a cementless acetabular cup. Ventrodorsal and
mediolateral radiographs were made of each pelvis, followed by CT imaging. After removal
of the first cup, the pelves were implanted with an acetabular cup in the contra-lateral
acetabulum and imaging was repeated. Three surgeons measured the ALO and version angles
three times for each cup from the mediolateral radiographic projection. The same measurements
were made using three-dimensional multiplanar reconstructions from CT images. Two
anatomical axes were used to measure pelvic inclination in the sagittal plane, resulting
in six measurements per cup. Two-way repeated measures analysis of variance evaluated
inter- and intra-observer repeatability for radiographic and CT-based measurements.
Results: Version angle based on radio-graphic measurement did not differ within surgeons (p
= 0.433), but differed between surgeons (p <0.001). Radiographic measurement of ALO
differed within surgeons (p = 0.006) but not between surgeons (p = 0.989). The ALO
and version angle measured on CT images did not differ with or between surgeons.
Clinical significance: Assessment of inter-and intra-observer measurement of ALO and version angle was more
reproducible using CT images than conventional mediolateral radiography for a Zurich
cementless acetabular cup.
Keywords
Canine - hip dysplasia - radiography - total hip arthroplasty - computed tomography