Micro-architecture study of the normal odontoid with micro-computed tomography

Geriatric Type II Fractures of the Dens Axis: Biomechanical Superiority of a New Osteosynthesis Plate Compared to Common Anterior Screw Fixation

Study DesignBiomechanical Basic Research.ObjectivesType II Fractures of the dens axis (DFTII) are common fractures of the cervical spine in geriatric patients. A surgical approach is the anterior screw fixation (ASF). However, a disadvantage is the high post-operative rate of non-union. This study aimed to develop and biomechanically test an osteosynthesis plate (OSP) for the anterior treatment of DFTII in comparison to ASF.MethodsA novel OSP was developed and manufactured. The OSP was biomechanically tested in comparison to ASF in synthetic bone models and geriatric human cadaveric bone. An analysis of the bone microstructure of the human C2 vertebrae was performed utilizing high-resolution quantitative computed tomography to exclude differences in bone quality among the experimental groups. Biomechanical testing was performed by cyclic loading of compression and tensile forces until failure.ResultsIn the comparative biomechanical analysis of ASF and OSP in synthetic bone, significant differences were observed regarding the load to failure, favoring the OSP (P = 0.040). The comparative biomechanical analysis of ASF and OSP in the cadaveric specimens also revealed a significantly lower load to failure of the ASF (P = 0.046). The experimental groups did not show significant differences regarding age, sex or bone microstructure.ConclusionsThe current study demonstrated that the OSP is biomechanically superior to the ASF, indicating higher stability. This study provides the basis for an alternative anterior treatment option for DFTII.

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

The odontoid process (dens) of the second cervical vertebra (axis) is prone to fracture. While the importance of its skeletal integrity has been previously noted, representative three-dimensional microarchitecture analyses in humans are not available. This study aimed to determine the bone microarchitecture of the axis using high-resolution quantitative computed tomography (HR-pQCT) and to derive clinical implications for the occurrence and treatment of axis fractures. For initial clinical reference, the apparent density of the axis was determined based on clinical computed tomography (CT) images in patients without and with fractures of the axis. Subsequently, 28 human axes (female 50%) obtained at autopsy were analyzed by HR-pQCT. Analyses were performed in three different regions corresponding to zones I (tip of dens), II (base of dens), and III (corpus axis) of the Anderson and D'Alonzo classification. Lower apparent densities based on clinical CT data were detected in zone II and III compared to zone I in both the group without and with fracture. In the autopsy specimens, cortical thickness and bone volume fraction decreased continuously from zone I to zone III. Trabecular and cortical tissue mineral density was lowest in zone III, with no differences between zones I and II. In conclusion, our clinical and high-resolution ex vivo imaging data highlight a marked regional heterogeneity of bone microarchitecture, with poor cortical and trabecular properties near the dens base. These results may partly explain why zones II and III are at high risk of fracture and osteosynthesis failure.

Ultrasonography, Microcomputed Tomography, and Macroscopic Preparation in an Anatomical Study of the Thoracic Limb of the Golden-Headed Lion Tamarin (Leontopithecus chrysomelas)

The aim of this study was to evaluate the normal anatomy of the forearm of the golden-headed lion tamarin (Leontopithecus chrysomelas) using microcomputed tomography (micro-CT) and ultrasonography (US) and then compare the results with the results of a gross anatomy dissection of the forearm. The results of the US examination of the musculoskeletal system of the tamarin forearm were not satisfactory. US imaging enabled observation of the shape of the soft tissue and the size of muscle groups; however, we distinguished more muscles by traditional methods. In addition, in the dissection study, the assessment of the muscles was easier. Examination of the forearm bones using micro-CT provided a complete picture of the bones in this part of the body and was less time-consuming than traditional methods. Imaging allows the anatomy to be represented as a 3D image. However, some methods are not accurate; as in our study, US did not allow a complete assessment of the forearm musculature.