Collagen fibre orientation in the annulus fibrosus of intervertebral disc during bending and torsion measured by x-ray diffraction

A microstructural investigation of intervertebral disc lamellar connectivity: detailed analysis of the translamellar bridges

“…13A–C indicate some design characteristics of the annular wall, including means to accommodate small amounts of interlamellar movement expected in normal function (up to 4°; Bruehlmann et al. 2004; Klein & Hukins, 1982a,b);…”

“…Earlier researchers have shown slip between adjacent lamellae accompanies torsion, flexion and extension (Hickey & Hukins, 1980; Klein & Hukins, 1982a). The change in orientation of collagen fibres in the rabbit disc wall due to a 5° torsion (≈ 5× more than the human physiological range; Gregersen & Lucas, 1967) was associated with a 2–3º change in the tilt angle of the fibres (Klein & Hukins, 1982a,b). A similarly small amount of lamellar reorientation was reported by Bruehlmann et al.…”

The elastic fibre network of the human lumbar anulus fibrosus: architecture, mechanical function and potential role in the progression of intervertebral disc degeneration

“…To understand how elastic fibres convey this functionality, it is helpful to examine their potential interactions with other matrix constituents, in particular collagen, with which at the microstructural level they appear to closely associate. Bending and compression of the intervertebral disc within the confines of each motion segment are made possible by the circumferential and axial expansion of the lamellae; this expansion is facilitated by both the direct extension of the collagen fibre bundles and their tilting relative to the transverse plane [18,31,32,51]. In circumferential expansion, direct extension of collagen fibre bundles (fibre strain, measured at the peripheral surface) as a total percentage of tissue deformation is relatively large [59,64].…”

“…The structural mechanism which facilitates tilting is relative collagen fibre reorientation, or inter-fibre 'sliding' [6]. In circumferential tension, the tilt angle (the angle of the fibres to the transverse plane) decreases as fibres re-orient towards the loading direction; in axial tension the opposite occurs [5,18,31,32]. Tensile deformation of lamellae could therefore be considered a two-stage process: on the initial application of load, the straightening of crimp occurs first, functioning perhaps more as a shock-absorbing mechanism to prevent sudden impact damage to the collagen fibres, similar to in tendons; larger-scale tensile deformation, particularly that which occurs axially in bending, then follows, facilitated by collagen fibre re-orientation.…”

The objectives for the mechanical evaluation of spinal instrumentation have changed

“…3.4 h). Alternatively, fibre angle has been quantified using X-ray diffraction [10,32], and has been used to demonstrate changes in orientation resulting from mechanical loading [14,15]. Unfortunately, the exposure times required for analysis of intact discs is very large, and there is poor spatial localisation of the tissue interrogated.…”