Advancing bone health evaluation in Hermann’s tortoises (Testudo hermanni) using spectral detector computed tomography

Introduction Metabolic bone disease (MBD) is a common disorder in captive chelonians. Early diagnosis is challenging due to non-specific clinical signs, normal blood values in early stages, and limited sensitivity of radiographs. Spectral detector computed tomography (SDCT) offers quantitative, phantomless assessment of bone mineral density (BMD) and may improve diagnostic accuracy. This study evaluated SDCT’s feasibility for measuring BMD in Hermann’s tortoises ( Testudo hermanni ) and its ability to distinguish healthy from MBD-affected individuals. We also examined whether CT-derived shell morphometric ratios correlate with shell softening severity. Materials and methods Twenty-three tortoises were divided into healthy and MBD-affected groups, with shell softness graded subjectively. SDCT scans were acquired without sedation, and BMD maps were generated using a phantom-based linear calibration model. Regions of interest were placed at the gular scute, scapula, and ilium. BMD distributions, mean values, and shell morphometric ratios were compared between groups. Results 106 measurement sites were analyzed. SDCT detected significant BMD declines from healthy to severely MBD-affected tortoises ( p ≤ 0.05) at all sites, most pronounced at the ilium. Diseased animals showed right-skewed BMD histograms with low-attenuation pixel accumulation. Shell height-to-width ratios did not differ significantly. BMD generally reflected clinical status, though mild cases overlapped with healthy values. Conclusion SDCT is a sensitive, non-invasive method for detecting and quantifying demineralisation in Hermann’s tortoises. It distinguishes healthy from MBD-affected individuals, enables objective observer-independent assessment, and complements clinical examination. SDCT shows strong potential for early diagnosis and monitoring of treatment in chelonian MBD. Larger, age-stratified cohorts are needed to confirm these findings.