Is Computed Tomography Useful for the Investigation of Bone Health When Managing Distal Radius Fractures? CT-derived Second Metacarpal Index (CT-2MCI): A reproducible Opportunistic Measure of Cortical Bone Status in Patients Undergoing Wrist Imaging

Abstract

Osteoporosis is characterized by low bone mineral density and microarchitectural deterioration, increasing the relative risk of fragility fractures. In distal radius fractures, cortical bone quality influences fracture severity and fixation outcomes. Traditional dual X-ray absorptiometry (DXA) assesses overall bone density but is weighted toward trabecular bone and is limited in the acute setting. X-ray-derived second metacarpal index (XR-2MCI) is a validated surrogate marker for cortical bone evaluation. This study aimed to assess the correlation between computed tomography-derived second metacarpal index (CT-2MCI) and conventional XR-2MCI, and to explore the correlations with local Hounsfield unit (HU) measurements.

A retrospective analysis was conducted on 87 patients who underwent both plain film and computed tomography (CT) of the ipsilateral hand within 3 months. HU measurements were taken at the distal radius and capitate. Intra/Interobserver reliability were assessed. Correlation between CT and radiographic indices, as well as HU values were evaluated.

CT-2MCI showed strong correlation with XR-2MCI across all orientations and was highly reproducible. Radial HU measurements demonstrated strong internal consistency between sites but correlated poorly with both radiographic and CT-2MCI. Subgroup analysis suggested moderate correlations between Capitate HU and XR-2MCI in females, but not males.

CT-2MCI is a reproducible, orientation-independent radiological index that demonstrated strong correlation with XR-2MCI, a validated surrogate marker for osteoporosis, thereby providing an opportunistic assessment of cortical bone status in patients undergoing wrist CT imaging. HU measurements should be interpreted according to the anatomical region and bony parameters being assessed. The study represent level of evidence III.