The value of magnetic resonance imaging as postoperative control after arthroscopic treatment of osteochondritis dissecans.

The purpose of our study was to evaluate the value of MRI for preoperative arthroscopical planning in patients with osteochondritis dissecans. Based on the experience from 136 patients with osteochondritis dissecans of the knee or the ankle who were arthroscopically operated by retrograde drilling a follow-up study was carried out with 86 of them by clinical, radiological and postoperative magnetic resonance imaging (MRI) examinations. The evaluation was made by means of a visual analogue scale and a score system. The radiological findings were analysed according to the classification of Rodegerdts and Gleissner. The changes based on the MR images were classified according to our own pathoanatomical classification. The total score showed a significant improvement from 63.3 to 79.6 points (knee) and from 50.6 to 70.4 points (ankle). In 72% of the cases, the findings of the MR images showed a defective cartilage surface in the area of the osteochondritis dissecans lesion. An increase of signal in the osteonecrotic area could be seen in 51% of the cases when using a short-time inversion recovery (STIR) image. Especially in patients with postoperative failures, a high percentage of cartilage defects (grade III) could be detected on the MR images (PS 500/10). Uptake of gadolinium-diethylene triamine tetra-acetic acid was regarded as a sign for revascularization. Radiographs did not correlate with these changes detected in the MR images. This retrospective study of an operated osteonecrosis dissecans by MRI provides more detailed information about eventual revascularization of the osteonecrotic area. With this information a more detailed preoperative planing for further cases should be possible.