Are we underestimating pathological fracture risk in malignant bone lesions of the proximal humerus?

This study is aimed at evaluating the distribution of metastatic bone disease (MBD), with a particular focus on the humerus, and its association with pathological fractures. Factors for contributing to the underestimation of fracture risk were assessed, including their impact on surgical management.

We retrospectively reviewed patient records of patients undergoing surgical treatment for MBD at our institution between 2005 and 2023. The analysis included factors such as medical history, tumour type, metastatic status, surgical method, lesion location, and imaging. The images of local and staging studies (CT chest/abdomen/pelvis, CT skeleton body, bone scan, PET/CT) were reviewed by two observers. Group comparisons were made based on lesion localisation.

The two most affected bone regions were the proximal femur (39.4%), followed by the proximal humerus (13.5%). Lesions of the proximal humerus were significantly more likely to be associated with pathological fractures compared to those of the proximal femur and other localisations (p < 0.01). Identified potential causes include less frequent depiction of the proximal humerus during staging (29% vs. 79% and 51%; p < 0.01) and overall lower Mirel's scores despite the number of fractures (8 vs. 10 and 9; p < 0.01).

Metastatic bone disease (MBD) in the proximal humerus is less frequently captured in current staging imaging, particularly CT chest/abdomen/pelvis. Additionally, fracture prediction using Mirel's scoring often underestimates the actual risk. Staging investigations should include this region more comprehensively, and even when correctly imaged, better tools are needed to evaluate bone metastases effectively.