ISSLS Prize Winner: A Detailed Examination of the Elastic Network Leads to a New Understanding of Annulus Fibrosus Organization.

STUDY DESIGN: Investigation of the elastic network in disc annulus and its function. OBJECTIVE: To investigate the involvement of the elastic network in the structural interconnectivity of the annulus and to examine its possible mechanical role. SUMMARY OF BACKGROUND DATA: The lamellae of the disc are now known to consist of bundles of collagen fibers organized into compartments. There is strong interconnectivity between adjacent compartments and between adjacent lamellae, possibly aided by a translamellar bridging network, containing blood vessels. An elastic network exists across the disc annulus and is particularly dense between the lamellae, and forms crossing bridges within the lamellae. METHODS: Blocks of annulus taken from bovine caudal discs were studied in either their unloaded or radially stretched state then fixed and sectioned, and their structure analyzed optically using immunohistology. RESULTS: An elastic network enclosed the collagen compartments, connecting the compartments with each other and with the elastic network of adjacent lamellae, formed an integrated network across the annulus, linking it together. Stretching experiments demonstrated the mechanical interconnectivities of the elastic fibers and the collagen compartments. CONCLUSION: The annulus can be viewed as a modular structure organized into compartments of collagen bundles enclosed by an elastic sheath. The elastic network of these sheaths is interconnected mechanically across the entire annulus. This organization is also seen in the modular structure of tendon and muscle. The results provide a new understanding annulus structure and its interconnectivity, and contribute to fundamental structural information relevant to disc tissue engineering and mechanical modeling. LEVEL OF EVIDENCE: N/A.

Classification of breast tissue using a laboratory system for small-angle x-ray scattering (SAXS).

Structural changes in breast tissue at the nanometre scale have been shown to differentiate between tissue types using synchrotron SAXS techniques. Classification of breast tissues using information acquired from a laboratory SAXS camera source could possibly provide a means of adopting SAXS as a viable diagnostic procedure. Tissue samples were obtained from surgical waste from 66 patients and structural components of the tissues were examined between q = 0.25 and 2.3 nm(-1). Principal component analysis showed that the amplitude of the fifth-order axial Bragg peak, the magnitude of the integrated intensity and the full-width at half-maximum of the fat peak were significantly different between tissue types. A discriminant analysis showed that excellent classification can be achieved; however, only 30% of the tissue samples provided the 16 variables required for classification. This suggests that the presence of disease is represented by a combination of factors, rather than one specific trait. A closer examination of the amorphous scattering intensity showed not only a trend of increased scattering intensity with disease severity, but also a corresponding decrease in the size of the scatterers contributing to this intensity.

Human nasal cartilage ultrastructure: characteristics and comparison using scanning electron microscopy.

OBJECTIVES/HYPOTHESIS: Human nasal cartilage is hyaline cartilage, although the function and loads placed on it are different depending on the location. We hypothesized that important differences exist between the nasal septal cartilage and lower lateral cartilage (LLC) ultrastructures. Such differences would be important in the field of cartilage engineering. METHODS: Ten specimens (6 septum and 4 LLC) of cartilage from patients undergoing nasal surgery (rhinoplasty or septoplasty) were obtained and examined using scanning electron microscopy. Micrographs were then analyzed and measured using photograph analysis software. RESULTS: The collagen fibers of septal cartilage were found to be arranged in a mesh framework, with larger lacunae and thicker fibers measuring 3.18 microm (standard deviation = 0.75 microm), with a 99.9% confidence interval of 2.74 to 3.54 microm. LLC fibers, on the other hand, were arranged in less-organized sheets, with fibrous extensions, and had fewer, narrower lacunae. The fibers from the LLC averaged 2.29 microm, with a 99.9% confidence interval of 1.17 to 3.42 microm. CONCLUSIONS: Significant ultrastructural differences exist between the cartilage of the nasal septum and LLC. These are almost certainly the result of their embryologic origins and different forces placed on the structures they support. A less-organized pattern with smaller collagen fibers is present in the LLC versus the more-organized, layered, thicker collagen fibers of the septum. These differences may prove to be critical in the future of cartilage engineering.