Radiographic Cortical Thickness Index Predicts Fragility Fracture in Gaucher Disease.

Background Patients with Gaucher disease (GD) have a high risk of fragility fractures. Routine evaluation of bone involvement in these patients includes radiography and repeated dual-energy x-ray absorptiometry (DXA). However, osteonecrosis and bone fracture may affect the accuracy of DXA. Purpose To assess the utility of DXA and radiographic femoral cortical thickness measurements as predictors of fragility fracture in patients with GD with long-term follow-up (up to 30 years). Materials and Methods Patients with GD age 16 years and older with a detailed medical history, at least one bone image (DXA and/or radiographs), and minimum 2 years follow-up were retrospectively identified using three merged UK-based registries (Gaucherite study, enrollment 2015-2017; Clinical Bone Registry, enrollment 2003-2006; and Mortality Registry, enrollment 1993-2019). Cortical thickness index (CTI) and canal-to-calcar ratio (CCR) were measured by two independent observers, and inter- and intraobserver reliability was calculated. The fracture-predictive value of DXA, CTI, CCR, and cutoff values were calculated using receiver operating characteristic curves. Statistical differences were assessed using univariable and multivariable analysis. Results Bone imaging in 247 patients (123 men, 124 women; baseline median age, 39 years; IQR, 27-50 years) was reviewed. The median follow-up period was 11 years (IQR, 7-19 years; range, 2-30 years). Thirty-five patients had fractures before or at first bone imaging, 23 patients had fractures after first bone imaging, and 189 patients remained fracture-free. Inter- and intraobserver reproducibility for CTI/CCR measurements was substantial (range, 0.96-0.98). In the 212 patients with no baseline fracture, CTI (cutoff, ≤0.50) predicted future fractures with higher sensitivity and specificity (area under the receiver operating characteristic curve [AUC], 0.96; 95% CI: 0.84, 0.99; sensitivity, 92%; specificity, 96%) than DXA T-score at total hip (AUC, 0.78; 95% CI: 0.51, 0.91; sensitivity, 64%; specificity, 93%), femoral neck (AUC, 0.73; 95% CI: 0.50, 0.86; sensitivity, 64%; specificity, 73%), lumbar spine (AUC, 0.69; 95% CI: 0.49, 0.82; sensitivity, 57%; specificity, 63%), and forearm (AUC, 0.78; 95% CI: 0.59, 0.89; sensitivity, 70%; specificity, 70%). Conclusion Radiographic cortical thickness index of 0.50 or less was a reliable independent predictor of fracture risk in Gaucher disease. Clinical trial registration no. NCT03240653 © RSNA, 2022