Zeitschriftenaufsätze und Buchbeiträge

Segmental degeneration in the human lumbar spine affects both the intervertebral discs and facet joints. Facet joint degeneration not only affects the cartilage surface, but also alters the cellular properties of the cartilage tissue and the structure of the subchondral bone. The primary focus of this study is the investigation of these microstructural changes that are caused by facet joint degeneration. Microstructural analyses of degenerated facet joint samples, obtained from patients following operative lumbar interbody fusion, have not previously been extensively investigated. This study analyzes human facet joint samples from the inferior articular process using scanning electron microscopy, micro-computed tomography, and energy dispersive X-ray spectroscopy to evaluate parameters of interest in facet joint degeneration such as elemental composition, cartilage layer thickness and cell density, calcification zone thickness, subchondral bone portion, and trabecular bone porosity. These microstructural analyses demonstrate fragmentation, cracking, and destruction of the cartilage layer, a thickened calcification zone, localized calcification areas, and cell cluster formation as pathological manifestations of facet joint degeneration. The detailed description of these microstructural changes is critical for a comprehensive understanding of the pathology of facet joint degeneration, as well as the subsequent development and efficacy analysis of regenerative treatment strategies.

One of the most challenging adaptations within the therians has been to ensure dynamic stability of the trunk during rapid locomotion in highly structured environments. A reorganization of limb mechanics and development of new sensors has taken place within their stem lineage. Rats, which have a similar lifestyle to the first therians, possess sinus hairs specialized for tactile sensing. It is supposed that carpal sinus hairs have a role in sensing substrate properties and can thus induce adjustments in limb kinematics and body posture according to the different surface diameters and structures detected. This implies a shared sensorimotor control loop of sinus hairs and body posture. To investigate the role of the carpal sinus hairs during locomotion and to explore a possible interaction between limb and spine motion, spatiotemporal and kinematic parameters as well as the contact mechanics of the hairs with regard to the surface were quantified. Locomotion on a treadmill with continuous and discontinuous substrates was compared in the presence/absence of the carpal sinus hairs across a speed range from 0.2 m/s to 0.6 m/s. Recordings were taken synchronously using x-ray fluoroscopy and normal-light high-speed cameras. Our investigation revealed that the three tactile hairs made a triangle-like contact with the ground approximately 30 ms before touchdown of the forelimb. Within that time, it is likely that both the body posture and its oscillation are adjusted according to the different surface textures. The sensory input of the carpal sinus hairs induces a stabilization of the trajectory of the center of mass and, therefore, improves the dynamic stability of the trunk; conversely, the absence of the sensors results in a more crouched frontal body posture, similar to that seen in rats when they are moving in an unknown terrain. The carpal sinus hairs also sense the animal's speed during surface contact. This implicates an adjustment of the limb and spine kinematics, by increasing the speed-dependent effect or by increasing the distance between the trunk and the ground when the rat is walking faster.