Influence of trabecular microstructure and cortical index on the complexity of proximal humeral fractures

Poor bone quality increases the susceptibility to fractures of the proximal humerus. It is unclear whether local trabecular and cortical measures influence the severity of fracture patterns. The goal of this study was to assess parameters of trabecular and cortical bone properties and to compare these parameters with the severity of fractures and biomechanical testing.

Twenty patients with displaced proximal humeral fractures planned for osteosynthesis were included. Fractures were classified as either 2-part fractures or complex fractures. Bone after core drilling was harvested during surgery from the humeral head in each patient. Twenty bone cores obtained from nonpaired cadaver humeral heads served as nonfractured controls. Micro-CT (μCT) was performed and bone volume/total volume (BV/TV), connectivity density (CD), trabecular number (Tb.N), trabecular thickness (Tb.Th), trabecular spacing (Tb.Sp), and bone mineral density (BMD) were assessed. The cortical index (CI) was determined from AP plain films. Biomechanical testing was done after μCT scanning by axially loading until failure, and ultimate strength and E modulus were recorded.

BV/TV, BMD and CD showed moderate to strong correlations with biomechanical testing (r = 0.45-0.76, all p < 0.05). No significant differences were detected between the 2-part and complex fracture groups and controls regarding μCT and biomechanical parameters. CI was not significantly different between the 2-part and complex fracture groups.

In our study population local trabecular bone structure and cortical index could not predict the severity of proximal humeral fractures in the elderly. Complex fractures do not necessarily imply lower bone quality compared to simple fractures.