The Stabilizing System of the Spine. Part I. Function, Dysfunction, Adaptation, and Enhancement

Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, New Haven, Connecticut 06510.
Journal of Spinal Disorders (Impact Factor: 1.21). 01/1993; 5(4):383-9; discussion 397. DOI: 10.1097/00002517-199212000-00001
Source: PubMed


Presented here is the conceptual basis for the assertion that the spinal stabilizing system consists of three subsystems. The vertebrae, discs, and ligaments constitute the passive subsystem. All muscles and tendons surrounding the spinal column that can apply forces to the spinal column constitute the active subsystem. The nerves and central nervous system comprise the neural subsystem, which determines the requirements for spinal stability by monitoring the various transducer signals, and directs the active subsystem to provide the needed stability. A dysfunction of a component of any one of the subsystems may lead to one or more of the following three possibilities: (a) an immediate response from other subsystems to successfully compensate, (b) a long-term adaptation response of one or more subsystems, and (c) an injury to one or more components of any subsystem. It is conceptualized that the first response results in normal function, the second results in normal function but with an altered spinal stabilizing system, and the third leads to overall system dysfunction, producing, for example, low back pain. In situations where additional loads or complex postures are anticipated, the neural control unit may alter the muscle recruitment strategy, with the temporary goal of enhancing the spine stability beyond the normal requirements.

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    • "Twenty participants with and 20 without non-specific CLBP (CLBP vs. WCLBP), which can be defined as multifactorial and/or mechanical physical back problems (Panjabi, 1992), were recruited on a voluntary basis from January to September 2014 at the Universities in Londrina City in Brazil (students/workers between 18 and 45 yrs old) and older adults (above 60 yrs old from the local community). Both groups were matched by age and sex (50% males and 50% females). "

    • "Forces in the spinal ligaments (Alapan et al., 2014; Wang et al., 1999) as well as forces and moments in the discs (Arjmand and Shirazi-Adl, 2006; El-Rich et al., 2004) were also predicted . Dysfunction of any spinal component results in system perturbation which may lead to immediate compensation from other components, long-term adaptation response and/or ultimately injury (Panjabi, 1992). Therefore, understanding the interaction of spinal components and their relative contribution in load-bearing (spinal load-sharing) is crucial to the spine function. "
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    ABSTRACT: A harmonic synergy between the load-bearing and stabilizing components of the spine is necessary to maintain its normal function. This study aimed to investigate the load-sharing along the ligamentous lumbosacral spine under sagittal loading. A 3D nonlinear detailed Finite Element (FE) model of lumbosacral spine with realistic geometry was developed and validated using wide range of numerical and experimental (in-vivo and in-vitro) data. The model was subjected to 500N compressive Follower Load (FL) combined with 7.5Nm flexion (FLX) or extension (EXT) moments. Load-sharing was expressed as percentage of total internal force/moment developed along the spine that each spinal component carried. These internal forces and moments were determined at the discs centres and included the applied load and the resisting forces in the ligaments and facet joints. The contribution of the facet joints and ligaments in supporting bending moments produced additional forces and moments in the discs. The intervertebral discs carried up to 81% and 68% of the total internal force in case of FL combined with FLX and EXT, respectively. The ligaments withstood up to 67% and 81% of the total internal moment in cases of FL combined with EXT and FLX, respectively. Contribution of the facet joints in resisting internal force and moment was noticeable at levels L4-S1 only particularly in case of FL combined with EXT and reached up 29% and 52% of the internal moment and force, respectively. This study demonstrated that spinal load-sharing depended on applied load and varied along the spine.
    Journal of Biomechanics 10/2015; DOI:10.1016/j.jbiomech.2015.09.050 · 2.75 Impact Factor
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    • "A limitation of these earlier studies, however, was the lack of control over the trunk displacement and response time. As such, measures of trunk stiffness represented the combined effects of active, passive, and neural control stabilizing subsystems (Panjabi, 1992a,b), without information about relative contributions of each subsystem. This limitation was later overcome by use of displacement-controlled perturbation paradigms Contents lists available at ScienceDirect journal homepage: "
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    ABSTRACT: Age-related differences in trunk intrinsic stiffness, as an important potential contributor to spinal stability, were investigated here because of: (1) the role of spinal instability in low back pain (LBP) development; (2) the increasing prevalence of LBP with age, and (3) the increasing population of older people in the workforce. Sixty individuals aged 20-70 years, in five equal-size age groups, completed a series of displacement-controlled perturbation tests in an upright standing posture while holding four different levels of trunk extension efforts. In addition to examining any age-related difference in trunk intrinsic stiffness, the current design assessed the effects of gender, level of effort, and any differences in lower back neuromuscular patterns on trunk intrinsic stiffness. No significant differences in trunk intrinsic stiffness were found between the age groups. However, stiffness was significantly larger among males and increased with the level of extension effort. No influences of differences in neuromuscular pattern were observed. Since the passive contribution of trunk tissues in the upright standing posture is minimal, our values of estimated trunk intrinsic stiffness primarily represent the volitional contribution of the lower back musculoskeletal system to spinal stability. Therefore, it seems unlikely that the alterations in volitional behavior of the lower back musculature, caused by aging (e.g., as reflected in reduced strength), diminish their contributions to the spinal stability.
    Journal of Biomechanics 10/2015; DOI:10.1016/j.jbiomech.2015.09.010 · 2.75 Impact Factor
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