gms | German Medical Science

Objectives/Interrogation: In osteochondritis dissecans (OCD) of the elbow, severity of the lesion affects prognosis and selection of treatment. It is difficult to precisely evaluate lesions even with magnetic resonance imaging (MRI) or computed tomography (CT). We developed a novel technique to construct three-dimensional (3D) MRI-CT fusion images. It enables the detailed evaluation and surgical simulation of OCD of the elbow. We aimed to validate the fusion images against intraoperative findings to clarify their usefulness.

Methods: We enrolled 10 patients with OCD of the elbow who underwent surgery. For preoperative CT, a 320-row detector imager (TOSHIBA©) was used to obtain 1-mm thick slices and to generate a 3D model of the humerus. A 3 Tesla imager (SIEMENS©) was used for preoperative MRI. Images were obtained using a 3D double-echo steady sequence, with 0.4-mm thick slices. 3D models of the humerus and articular cartilage were constructed. To widen the humeroradial joint space and clarify the articular cartilage outline, 7 kg of axial traction was applied to the elbow during MRI. Images were fused for further evaluation and surgical simulation, using software manufactured by Materialise©. The International Cartilage Repair Society (ICRS) classification was predicted based comprehensively on articular cartilage shape (normal or irregular), and the existence of cartilage fissure or defect and segmented subchondral bone lesion. Average distance error of fusion images was examined. Preoperative ICRS classification expected from fusion images was compared with intraoperative ICRS classification. The applicability of preoperative simulation of surgery was evaluated.

Results and Conclusions: Average distance error of the fusion images was 0.87 (range 0.74-1.00) mm. The expected ICRS classifications were classes II, III, and IV in 1, 4, and 5 cases, respectively. Intraoperative ICRS classification accurately matched the imaging-based predictions in all patients. As operative planning, subchondral drilling for a class II and class IV case, free body removal in a class IV case, and costal osteochondral autograft for 4 class III cases and 3 class IV cases were simulated. Surgeries were conducted based on the simulations.

The 3D MRI-CT fusion images provide the exact positional relationship between bony and cartilaginous lesions, an accurate evaluation of lesion severity, and a precise simulation of the surgical procedure. In conclusion, this is a novel and useful technique for the treatment of OCD of the elbow.