In vitro analysis of thoracic spinal motion segment flexibility during stepwise reduction of all functional structures.

PURPOSE: The aim of this study was to quantify the stabilizing effect of the passive structures in thoracic spinal motion segments by stepwise resections. These data can be used to calibrate finite element models of the thoracic spine, which are needed to explore novel surgical treatments of spinal deformities, fractures, and tumours. METHOD: Six human thoracic spinal motion segments from three segmental levels (T2-T3, T6-T7, and T10-T11) were loaded with pure moments of 1 and 2.5 Nm in flexion/extension, lateral bending, and axial rotation. After each loading step, the ligaments, facet capsules, and the nucleus pulposus were stepwise resected from posterior to anterior direction, while the segmental relative motions were measured using an optical motion tracking system. RESULTS: Significant increases (p < 0.05) in the range of motion were detected after resecting the anterior spinal structures depending on loading magnitude, motion direction, and segmental level. The highest relative increases in the range of motion were observed after nucleotomy in all motion directions. The vertebral arch mostly stabilized the thoracic spinal motion segments in flexion and extension, while the facet joint capsules mainly affected the segmental stability in axial rotation. Coupled motions were not observed. CONCLUSIONS: The anulus fibrosus defines the motion characteristics qualitatively, while the ligaments and the presence of the nucleus pulposus restrict the mobility of a thoracic spinal motion segment solely in a quantitative manner. The posterior ligaments do not predominantly serve for primary stability but for the prevention of hyperflexion. These slides can be retrieved under Electronic Supplementary Material.

Rotation frequency of human bronchial and nasal epithelial spheroids as an indicator of mucociliary function.

BACKGROUND: We evaluated a new in vitro model for mucociliary transport function. Spheroids of human respiratory epithelium show beating cilia at their surface. When cultured in their own mucus, spheroids can rotate along their axis due to coordinated ciliary beating. OBJECTIVE AND METHODS: To assess whether this setup yields meaningful results we measured rotation frequency (RF) of human bronchial or nasal epithelial spheroids under different temperatures and concentrations of isoproterenol. Isoproterenol was administered either as caged compound releasing active isoproterenol after illumination with UV light, or through a permeable membrane in a two-chamber system. RESULTS: Under stable conditions, RF remained constant over 200 min. Between 27 and 35 degrees C, there was a temperature-dependent increase: RF(27)( degrees )(C) = 0.27 +/- 0.08 s(-1), and RF(37)( degrees )(C) = 0.43 +/- 0.10 s(-1) (means +/- SEM). Isoproterenol (10(-5), 10(-4) and 10(-3) mmol/l) induced concentration-dependent increases in RF (9, 20 and 25%, respectively; medians) if applied in the two-chamber system. The experiments with caged isoproterenol did not yield conclusive results, probably because the byproducts from photolysis negatively affected ciliary function. The transport velocity at the surface of bronchial and nasal spheroids was estimated to be 2.96 and 3.62 mm/min (medians), respectively, which is in the same range as mucus transport velocity measured in vivo in humans. CONCLUSIONS: This setup can be used to study mucociliary transport function under controlled conditions in vitro, in particular as RF is likely to reflect not only ciliary beat frequency, but also the coordination of ciliary beating and the properties of the mucus.