Comparison of Two Scaling Methods in Preoperative Digital Templating of Total Hip Replacement

Abstract

Background/Purpose: Preoperative templating is essential for the planning of total hip replacement. Digital templating has gained popularity due to the availability of digital images. Scaling is the critical step that calibrates magnified digital images to the actual dimension, for subsequent digital templating. We compared the accuracy of two scaling methods: (1) radiological marker; and (2) fixed magnification factor. Methods: Forty-five postoperative radiographs in 21 patients who had undergone either total hip replacement or hip hemiarthroplasty were evaluated. The sizes of femoral head components in the digital radiographs were estimated using the two scaling methods. The estimated values were then compared to the true values stated in operation records. The absolute error (AE) and relative error (RE) of both scaling methods were calculated and compared. Results: Both the mean AE and RE were smaller in Method 2 (fixed magnification factor), and were statistically significant (p < 0.05). Conclusion: We recommend fixed magnification factor as the scaling method for digital templating.

Keywords

• calibration
• digital radiograph
• scaling
• templating
• total hip arthroplasty