Osteoporosis changes the amount of vertebral trabecular bone at risk of fracture but not the vertebral load distribution

Study Design. A finite-element study to investigate the amount of trabecula r bone at risk of fracture and the distribution of load between trabecular core and cortical shell, for healthy, osteopenic, and osteoporotic vertebra e. Objectives. To determine differences between healthy, osteopenic, and osteo porotic vertebrae with regard to the risk of fracture and the load distribu tion. Summary of Background Data. The literature contains no reports on the effec ts of osteopenia and osteoporosis on load distribution in vertebral bodies, nor any reports on the amount of trabecular bone at risk of fracture. Methods. Computed tomography data of vertebral bodies were used to construc t patient-specific finite-element models. These models were then used in fi nite-element analyses to determine the physiologic stresses and strains in the vertebrae. Results. For all three classes of vertebrae the contribution of the trabecu lar core to the total load transfer decreased from about 70% near the endpl ates to about 50% in the midtransverse region. The amount of trabecular bon e that is at risk of fracture was about 1% for healthy vertebrae, about 3% for osteopenic vertebrae, and about 16% for osteoporotic vertebrae. Conclusions. Our finite-element models indicated that neither osteopenia no r osteoporosis had any effect on the contribution of the trabecular core to the total load placed on the vertebra. The trabecular core carried about h alf the load. Our finite-element models indicated that osteoporosis had a s ignificant effect on the amount of trabecular bone at risk of fracture, whi ch increased from about 1% in healthy vertebrae to about 16% for osteoporot ic vertebrae.