Biomedical imaging is essential in the diagnosis of musculoskeletal pathologies and postoperative evaluations. In this context, Cone-Beam technology-based Computed Tomography (CBCT) can make important contributions in orthopaedics. CBCT relies on divergent cone X-rays on the whole field of view and a rotating source-detector element to generate three-dimensional (3D) volumes. For the lower limb, they can allow acquisitions under real loading conditions, taking the name Weight-Bearing CBCT (WB-CBCT). Assessments at the foot, ankle, knee, and at the upper limb, can benefit from it in situations where loading is critical to understanding the interactions between anatomical structures. The present study reports 4 recent applications using WB-CBCT in an orthopaedic centre. Patient scans by WB-CBCT were collected for examinations of the lower limb in monopodal standing position. An initial volumetric reconstruction is obtained, and the DICOM file is segmented to obtain 3D bone models. A reference frame is then established on each bone model by virtual landmark palpation or principal component analysis. Based on the variance of the model point cloud, this analysis automatically calculates longitudinal, vertical and mid-lateral axes. Using the defined references, absolute or relative orientations of the bones can be calculated in 3D. In 19 diabetic patients, 3D reconstructed bone models of the foot under load were combined with plantar pressure measurement. Significant correlations were found between bone orientations, heights above the ground, and pressure values, revealing anatomic areas potentially prone to ulceration. In 4 patients enrolled for total ankle arthroplasty, preoperative 3D reconstructions were used for prosthetic design customization, allowing prosthesis-bone mismatch to be minimized. 20 knees with femoral ligament reconstruction were acquired with WB-CBCT and standard CT (in unloading). Bone reconstructions were used to assess congruency angle and patellar tilt and TT-TG. The values obtained show differences between loading and unloading, questioning what has been observed so far. Twenty flat feet were scanned before and after Grice surgery. WB-CBCT allowed characterization of the deformity and bone realignment after surgery, demonstrating the complexity and multi-planarity of the pathology. These applications show how a more complete and realistic 3D geometric characterization of the of lower limb bones is now possible in loading using WB-CBCT. This allows for more accurate diagnoses, surgical planning, and postoperative evaluations, even by automatisms. Other applications are in progress.
The aims of the treatment of tibial infected nonunions with bone and soft tissue loss (generally consequent to open fractures) are: the healing of infection, the bone consolidation with preservation of lower limb length and the reconstruction of soft tissue loss. The epider-mato-fascio-osteoplasty according to Umiarov (a modification of bifocal or multifocal compression-distraction osteosynthesis) enables to treat wide areas of bone and soft tissue loss without a preventive sterilization of the infection neither soft tissues closure and without bone and skin grafts. An important point of the treatment is the prevention of complications such as: persistence of infection (due to an insufficient debridement), trouble in formation of bone regenerate and /or callus at the docking site (due to inadequate configuration of the external fixator, imperfect management of the phases of treatment, obstacles on bone transport), defect of skin coverage (due to an improper rate of bone and soft tissue transport), complications at the site of application of the device (inflammation or infection, breaking of the fixation elements), functional impairment (knee and ankle stiffness). In the 54 patients treated the anatomical and functional results have been particularly favourable, thanks to an accurate preoperative planning and a careful postoperative management, diminishing the risks of complications.
