Elliptical acquisition provides measurement accuracy comparable to CT in an experimental model of hip surgery.

INTRODUCTION: Robot-assisted and computer-assisted hip arthroplasty rely on preoperative CT imaging and digital twins, but real-time intraoperative 3D imaging remains limited. Elliptical acquisition using a mobile cone-beam CT system could provide repeatable intraoperative 3D images with lower radiation exposure than conventional CT. HYPOTHESIS: Elliptical acquisition would provide accuracy and precision comparable to conventional CT for these measurements. MATERIALS AND METHODS: An isolated Sawbone pelvis with a previously implanted right total hip and a native left hip was imaged using a 2D/3D C-arm with elliptical acquisition and a conventional CT scanner. Four metallic markers were placed to define distances of interest. The primary endpoint was prosthetic femoral head diameter. Secondary endpoints were the sciatic spine-greater trochanter (SS-GT), pubic spine-greater trochanter (PS-GT), and anterior superior iliac spine-greater trochanter (ASIS-GT) distances. For each parameter, 10 repeated measurements were obtained on 5 acquisitions per modality and compared with 10 direct digital caliper measurements used as the reference standard. Accuracy was assessed as bias relative to the reference standard, and precision as the standard deviation of repeated measurements. Radiation dose was recorded as dose-area product (DAP). RESULTS: The reference prosthetic femoral head diameter was 28.08 mm (SD 0.06). Mean CT-based diameter was 28.18 mm (SD 0.29; bias +0.10), and mean elliptical diameter was 28.01 mm (SD 0.25; bias -0.07). For the SS-GT, PS-GT and ASIS-GT distances, mean biases of CT and elliptical measurements remained below 0.2 mm for all parameters. Elliptical measurements tended to show slightly lower bias and, for most distances, lower dispersion than CT. Mean DAP per acquisition was 7.62 × 10-5 Gy·m2 for CT and 5.48 × 10-5 Gy·m2 for elliptical acquisition. CONCLUSION: In this Sawbone model of hip surgery, intraoperative elliptical acquisition provided femoral head and marker distance measurements with accuracy and precision comparable to conventional CT, with slightly lower radiation exposure in this experimental setup. These preliminary findings support technical feasibility for intraoperative three-dimensional assessment, but clinical relevance remains to be established. LEVEL OF EVIDENCE: IV.