Assessing the relative positioning of an osteosynthesis plate to the patient-specific femoral shape from plain 2D radiographs
- We present a novel method to derive the surface distance of an osteosynthesis plate w.r.t. the patientspecific surface of the distal femur based on 2D Xray images. Our goal is to study from clinical data, how the platetobone distance affects bone healing. The patientspecific 3D shape of the femur is, however, seldom recorded for cases of femoral osteosynthesis since this typically requires Computed Tomography (CT), which comes at high cost and radiation dose. Our method instead utilizes two postoperative Xray images to derive the femoral shape and thus can be applied on radiographs that are taken in clinical routine for followup. First, the implant geometry is used as a calibration object to relate the implant and the individual Xray images spatially in a virtual Xray setup. In a second step, the patientspecific femoral shape and pose are reconstructed in the virtual setup by fitting a deformable statistical shape and intensity model (SSIM) to the images. The relative positioning between femur and implant is then assessed in terms of displacement between the reconstructed 3D shape of the femur and the plate. A preliminary evaluation based on 4 cadaver datasets shows that the method derives the platetobone distance with a mean absolute error of less than 1mm and a maximum error of 4.7 mm compared to ground truth from CT. We believe that the approach presented in this paper constitutes a meaningful tool to elucidate the effect of implant positioning on fracture healing.
Author: | Moritz Ehlke, Mark Heyland, Sven Märdian, Georg N. Duda, Stefan ZachowORCiD |
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Document Type: | In Proceedings |
Parent Title (English): | Proceedings of the 15th Annual Meeting of CAOS-International (CAOS) |
Tag: | 3d-reconstruction from 2d Xrays; fracture fixation of the distal femur; pose estimation; statistical shape and intensity models |
Year of first publication: | 2015 |
Preprint: | urn:nbn:de:0297-zib-54268 |