Evaluation of the accuracy and use of x-ray markers in digital templating for total hip arthroplasty.

Despite benefits of digital templating, digital image acquisition techniques often make image magnification unknown and variable. We assessed the accuracy of digital x-ray scaling devices based on position. Radiographs of 106 total hip arthroplasty (THA) patients were studied to determine the accuracy of 2 digital x-ray markers at 1 of 4 positions by comparing true to expected x-ray magnification. The Pearson r coefficient was calculated as an indicator of measurement correlation between investigators. Greater accuracy was obtained for markers placed at the greater trochanter without skin overlap than for markers placed with soft tissue or bone overlap on x-ray. Flexible positioning markers provided greater accuracy than adhesive markers. Based on our data, we suggest positioning at the greater trochanter without skin overlap on x-ray and suggest flexible positioning over adhesive marker use.