The classification of osteonecrosis in patients with cancer: validation of a new radiological classification system

•Patients with cancer may have osteonecrosis lesions at multiple sites.•There is no non-joint-specific osteonecrosis classification available.•We introduced a new non-joint-specific osteonecrosis classification.•The validation was performed by assessing inter- and intra-observer reliability.•The classification was reliable and could be used regardless of the affected site.

AimTo validate a new, non-joint-specific radiological classification system that is suitable regardless of the site of the osteonecrosis (ON) in patients with cancer.Material and methodsCritical deficiencies in the existing ON classification systems were identified and a new, non-joint-specific radiological classification system was developed. Seventy-two magnetic resonance imaging (MRI) images of patients with cancer and ON lesions were graded, and the validation of the new system was performed by assessing inter- and intra-observer reliability.ResultsIntra-observer reliability of ON grading was good or very good, with kappa values of 0.79–0.86. Interobserver agreement was lower but still good, with kappa values of 0.62–0.77. Ninety-eight percent of all intra- or interobserver differences were within one grade. Interobserver reliability of assessing the location of ON was very good, with kappa values of 0.93–0.98.ConclusionAll the available radiological ON classification systems are joint specific. This limitation has spurred the development of multiple systems, which has led to the insufficient use of classifications in ON studies among patients with cancer. The introduced radiological classification system overcomes the problem of joint-specificity, was found to be reliable, and can be used to classify all ON lesions regardless of the affected site.