Biomechanical Assessment of Fracture Loads and Patterns of the Odontoid Process

Abstract

Study Design. Laboratory study. Objective. This study aimed to investigate the biomechanical competence and fracture characteristics of the odontoid process. Summary of Background Data. Odontoid fractures of the second cervical vertebra (C2) represent the most common spine fracture type in the elderly. However, very little is known about the underlying biomechanical fracture mechanisms. Materials and Methods. A total of 42 C2 human anatomic specimens were scanned via computed tomography, divided in six groups, and subjected to combined quasistatic loading at −15°, 0°, and 15° in sagittal plane and −50° and 0° in transverse plane until fracturing. Bone mineral density (BMD), height, fusion state of the ossification centers, stiffness, yield load, and ultimate load were assessed. Results. While lowest values for stiffness, yield load, and ultimate load were observed at load inclination of 15° in sagittal plane, no statistically significant differences were observed between the study groups (P≥0.235). BMD correlated positively with yield load (r 2=0.350, P<0.001) and ultimate load (r 2=0.955, P<0.001) but not with stiffness (r 2=0.082, P=0.07). The specimens with clearly distinguishable fusion of the ossification centers revealed less data scattering of the biomechanical outcomes. Conclusion. Load direction plays a subordinate role in traumatic fractures of the odontoid process. BMD was associated with significant correlation to the biomechanical outcomes. Thus, odontoid fractures appear to result from of an interaction between the load magnitude and bone quality.

Analysis of Three-Dimensional Bone Microarchitecture of the Axis Exposes Pronounced Regional Heterogeneity Associated with Clinical Fracture Patterns

“…Previous studies have shown that local bone mass and microarchitecture have a major influence on the occurrence of fractures [ 26 – 31 ]. By analyzing bone specimens from lumbar vertebrae via image-guided failure assessment under microtomographic imaging, it was shown that a decrease in BV/TV is accompanied by an increased fracture probability and that especially the combination of low BV/TV and Conn.D indicates the weakest bone region.…”

“…, bone structure, bone composition, joints, and ligaments, and trauma mechanism are decisive. A recent biomechanical study investigated the influence of bone density on the occurrence of axis fractures indicating an increased fracture risk with low BMD while the direction of the applied loading showed little influence [ 31 ]. Nevertheless, especially the articular connection between the anterior arch of the atlas and the DAX seems likely to be relevant for the occurrence of the DFTII.…”

Artificial neural networks for the detection of odontoid fractures using the Konstanz Information Miner Analytics Platform

“…The most common mechanism of injury is the hyperextension of the cervical spine, which pushes the head and C1 vertebrae backward. Odontoid fractures account for 20% of cervical spine fractures in adults and are the most common subtype among patients aged >65 years [ 3 , 4 ]. Specifically, spine surgeons are interested in this topic because these injuries have high morbidity and fatality rates [ 5 , 6 ].…”