Till Örebro universitet

Background: Recently, total hip arthroplasty (THA) has come to focus on restoration of individual anatomy including femoral neck anteversion and global offset (femoral and acetabular offset). Three-dimensional (3D) computed tomography (CT) data could provide a better basis for preoperative templating. The use of CT has been hampered by high radiation dose.

Purpose: To evaluate the effective dose used in pelvis and hip CT for THA templating.

Material and Methods: CT data from two clinical trials of THA were evaluated for CT scan length and volume CT dose index (CTDIvol). The effective doses from hip-knee-ankle CT and pelvis and hip radiography were compared. Conversion factors for effective dose for radiography were calculated using the PCXMC software.

Results: A reduced dose CT protocol for pelvis imaging gave a substantial dose reduction compared with standard CT, while maintaining sufficient image quality. Between the two clinical trials there was a significant reduction in effective CT dose corresponding to changes in the CT protocol (P<0.01). The CT dose for the latter group was similar to, but nevertheless significantly higher than for, radiography (P<0.01). However, in the latter group the theoretical minimum dose for CT, using the minimum scan length required by the templating software, was equal to the dose from radiography.

Conclusion: Although the CT dose remained higher than for radiography, potential reductions in scan length could reduce the dose further so that CTwould have a comparable level of risk to radiography with the added benefit of 3D templating.