Calibration Marker Position in Digital Templating of Total Hip Arthroplasty

We report a mathematical method to assess the vertical and horizontal positions of spherical radiopaque objects of known size in conventional radiographs.

The reliability and validity of the method were tested in an experimental setting and applied to 100 anteroposterior pelvic radiographs with external calibration markers and unilateral total hip arthroplasty (THA).

We found excellent reliabilities; intraclass correlation coefficients for interobserver and intraobserver reliabilities were 0.999-1.000 (P = .000). The mean normal height of THA was 198 mm (range: 142-243 mm, standard deviation: 18 mm) above the detector. Vertical and horizontal external marker positions differed significantly from the true hip center (THA; P < .001 and P = .017).

This method could enhance patient safety by enabling automated detection of malpositioned calibration markers by templating software.