Incidental T1-hypointense spinal lesions: Retrospective application of Bone-RADS

Incidental T1-hypointense bone lesions on spinal MRI frequently prompt follow-up. We retrospectively applied the 2022 Society of Skeletal Radiology Bone Reporting and Data System (Bone-RADS) framework to a historical cohort to assess concordance between observed lesion outcomes and Bone-RADS expectations and quantify imaging that would not have been recommended under the framework.

This retrospective cohort study was approved by the institutional Research Ethics Board with waiver of informed consent. Spine MRI reports from May 2013 to May 2023 were reviewed. Of 256,989 spine MRI examinations, 6709 reports contained the term "T1-hypointense," and 276 patients with recommended and completed lesion-directed follow-up met inclusion criteria. Bone-RADS was applied retrospectively to this follow-up-enriched cohort; no histopathological reference standard was available.

Among 276 patients with incidental T1-hypointense bone lesions, 212 had solitary lesions eligible for retrospective Bone-RADS classification and 64 had multiple lesions, which were not classified. Of the 212, 186 were classified as Bone-RADS 1 and 26 as Bone-RADS 2/3. The 186 Bone-RADS 1 patients underwent 295 lesion-directed follow-up examinations that would not have been recommended under retrospective application of Bone-RADS. No lesion developed aggressive features or required biopsy or intervention. Median follow-up for Bone-RADS 1 lesions was 5.5 months (interquartile range, 3.0-21.5 months).

Observed outcomes were concordant with Bone-RADS expectations but do not constitute validation of the framework. Retrospective application identified follow-up examinations beyond Bone-RADS recommendations for lesions classified as Bone-RADS 1. Prospective multicenter evaluation against histopathological or long-term clinical reference standards is required.