Article

Disc Degeneration Affects the Multidirectional Flexibility of the Lumbar Spine

Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, New Haven, Connecticut.
Spine (Impact Factor: 2.45). 07/1994; 19(12):1371-80. DOI: 10.1097/00007632-199406000-00011
Source: PubMed

ABSTRACT An in vitro biomechanical investigation using human lumbar cadaveric spine specimens was undertaken to determine any relationship between intervertebral disc degeneration and nonlinear multidirectional spinal flexibility.
Previous clinical and biomechanical studies have not established conclusively such a relationship.
Forty-seven discs from 12 whole lumbar spine specimens were studied under the application of flexion-extension, axial rotation, and lateral bending pure moments. Three flexibility parameters were defined (neutral zone (NZ), range of motion (ROM), and neutral zone ratio (NZR = NZ/ROM)) and correlated with the macroscopic and radiographic degeneration.
In flexion-extension, the ROM decreased and NZR increased with degeneration. In axial rotation, NZ and NZR increased with degeneration. In lateral bending, the ROM significantly decreased and the NZR increased with degeneration. In all three loading directions, the NZR increased, indicating greater joint laxity with degeneration.

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    • "Mechanical instability is considered related to excessive spinal segmental movement and is confirmed by radiography (Fritz et al., 2005; Beazell et al., 2010). Numerous studies have dealt with changes in segmental movement in relation with structural changes in the disc, which is a finding reported in cases of disc degeneration (Mimura et al., 1994; Li et al., 2011; Ibarz et al., 2013). Panjabi (1992) defined a functional instability as loss of the spine's ability to maintain intervertebral neutral zones under loaded conditions , resulting in pain and disability. "
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    • "Yet, experimental and computational works inferred that the disc morphology also affects the spinal compliance [8] [9]. Indeed, independently of the disc's chemical composition or integrity, it was shown that the larger the cross-sectional area of an intervertebral disc, the stiffer its response and that the thicker the IVD, the more compliant its behavior. "
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    • "A biomechanical study revealed the importance of the anterior portion of the spine for spinal stability. The role of intervertebral discs in degenerative spinal instability has previously been clarified by means of biomechanical cadaver studies [22] [23]. Another cadaver study revealed that axial rotational motion was more affected by disc degeneration rather than posterior facet joints, and segmental motion increased with increasing severity of disc degeneration [22]. "
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