1,874 research outputs found

    A biomechanical model of the spine to predict trunk muscle forces: Optimizing the relationship between spinal stability and spinal loading.

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    The purpose of this study was to develop an optimization model of the spine that, incorporating a measure of spinal stability as a constraint, allowed for realistic predictions of trunk muscle and spine compression forces. A 3-dimensional, 52 muscle, single joint model of the lumbar spine was developed and tested in situations of pure trunk flexor and lateral bend moments. Spinal stability, about each anatomical axis, was calculated at the L4/L5 spinal joint. Estimates of the optimal level of spinal stability, in a given loading situation, obtained through the use of regression equations developed from experimental findings, were utilized as constraints in the optimization model. Two separate optimization cost functions were tested: (1) minimization of the sum of the cubed trunk muscle forces; (2) minimization of the intervetebral force at the L4/L5 joint level. The addition of spinal stability measures, about each anatomical axis, as constraints in the optimization model, caused significantly improved estimates of the compressive forces acting on the spine, as well as improved prediction of trunk muscle forces as a whole. Furthermore, the addition of stability constraints allowed the model to predict activity in muscles functioning as pure antagonists to the applied external moment, a first for optimization models of the spine. Thus, it is concluded that spinal stability plays a vital role in dictating the recruitment patterns of trunk muscles. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2003 .B76. Source: Masters Abstracts International, Volume: 42-02, page: 0572. Adviser: Jim Potvin. Thesis (M.H.K.)--University of Windsor (Canada), 2003

    Trunk muscle recruitment patterns in patients with low back pain enhance the stability

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    Study Design. A comparative study of trunk muscle recruitment patterns in healthy control subjects and patients with chronic low back pain was conducted. Objective. To assess trunk muscle recruitment in patients with low back pain. Summary of Background Data. Conflicting evidence has been reported on the level and pattern of trunk muscle recruitment in patients with low back pain. The disparities can be explained partly by methodologic differences. It was hypothesized that trunk muscle recruitment patterns may be altered in patients with low back pain to compensate for reduced spinal stability. Methods. For this study, 16 patients with low back pain and 16 matched control subjects performed slow trunk motions about the neutral posture and isometric ramp contractions while seated upright. Ratios of electromyographic amplitudes and estimated moment contributions of antagonist over agonist muscles and of segmentally inserting muscles over muscles inserting on the thorax and pelvis only were calculated. In addition, model simulations were performed to assess the effect of changes in muscle recruitment on spinal stability. Results. The ratios of antagonist over agonist, and of lumbar over thoracic erector spinae electromyographic amplitude and estimated moment contributions were greater in the patients than in the control subjects. The simulation model predicted that these changes would effectively increase spinal stability. Conclusions. Trunk muscle recruitment patterns in patients with low back pain are different from those in healthy control subjects. The differences are likely to be functional with respect to enhancement of spinal stability in the patients

    Trunk muscle recruitment patterns in patients with low back pain enhance the stability of the lumbar spine

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    STUDY DESIGN: A comparative study of trunk muscle recruitment patterns in healthy control subjects and patients with chronic low back pain was conducted. OBJECTIVE: To assess trunk muscle recruitment in patients with low back pain. SUMMARY OF BACKGROUND DATA: Conflicting evidence has been reported on the level and pattern of trunk muscle recruitment in patients with low back pain. The disparities can be explained partly by methodologic differences. It was hypothesized that trunk muscle recruitment patterns may be altered in patients with low back pain to compensate for reduced spinal stability. METHODS: For this study, 16 patients with low back pain and 16 matched control subjects performed slow trunk motions about the neutral posture and isometric ramp contractions while seated upright. Ratios of electromyographic amplitudes and estimated moment contributions of antagonist over agonist muscles and of segmentally inserting muscles over muscles inserting on the thorax and pelvis only were calculated. In addition, model simulations were performed to assess the effect of changes in muscle recruitment on spinal stability. RESULTS: The ratios of antagonist over agonist, and of lumbar over thoracic erector spinae electromyographic amplitude and estimated moment contributions were greater in the patients than in the control subjects. The simulation model predicted that these changes would effectively increase spinal stability. CONCLUSIONS: Trunk muscle recruitment patterns in patients with low back pain are different from those in healthy control subjects. The differences are likely to be functional with respect to enhancement of spinal stability in the patients

    Biomechanical testing of a polymer-based biomaterial for the restoration of spinal stability after nucleotomy

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    <p>Abstract</p> <p>Background</p> <p>Surgery for disc herniations can be complicated by two major problems: painful degeneration of the spinal segment and re-herniation. Therefore, we examined an absorbable poly-glycolic acid (PGA) biomaterial, which was lyophilized with hyaluronic acid (HA), for its utility to (a) re-establish spinal stability and to (b) seal annulus fibrosus defects. The biomechanical properties range of motion (ROM), neutral zone (NZ) and a potential annulus sealing capacity were investigated.</p> <p>Methods</p> <p>Seven bovine, lumbar spinal units were tested in vitro for ROM and NZ in three consecutive stages: (a) intact, (b) following nucleotomy and (c) after insertion of a PGA/HA nucleus-implant. For biomechanical testing, spinal units were mounted on a loading-simulator for spines. In three cycles, axial loading was applied in an excentric mode with 0.5 Nm steps until an applied moment of ± 7.5 Nm was achieved in flexion/extension. ROM and NZ were assessed. These tests were performed without and with annulus sealing by sewing a PGA/HA annulus-implant into the annulus defect.</p> <p>Results</p> <p>Spinal stability was significantly impaired after nucleotomy (p < 0.001). Intradiscal implantation of a PGA-HA nucleus-implant, however, restored spinal stability (p < 0.003). There was no statistical difference between the stability provided by the nucleus-implant and the intact stage regarding flexion/extension movements (p = 0.209). During the testing sequences, herniation of biomaterial through the annulus defect into the spinal canal regularly occurred, resulting in compression of neural elements. Sewing a PGA/HA annulus-implant into the annulus defect, however, effectively prevented herniation.</p> <p>Conclusion</p> <p>PGA/HA biomaterial seems to be well suited for cell-free and cell-based regenerative treatment strategies in spinal surgery. Its abilities to restore spinal stability and potentially close annulus defects open up new vistas for regenerative approaches to treat intervertebral disc degeneration and for preventing implant herniation.</p

    Low back pain : a comparative study on the value of core training versus traditional strengthening exercises

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    This randomised controlled trial (RCT) employed a pre-test/post-test design to compare the effects of core training (Pilates method) and traditional back exercises on a population with low back pain (LBP). Therapeutic intervention related to the Pilates method has recently become popular, but there is little evidence to prove it works. In this study, 120 individuals with LBP were allocated to three different groups. Group A was the control group, Group B was given modified Pilates intervention and Group C received traditional back exercises. All three groups were given a posture re-education session and back-care advice. After the initial session, the control group had individual sessions on posture re-education. The other groups undertook a six-week course of either modified Pilates or general back exercise classes. The modified Pilates group was taught how to use the core muscles, incorporating stabilisation with increasing functional movements. The back exercise group did similar exercises without learning to specifically stabilise. The Oswestry Low Back Pain Disability Questionnaire (ODQ) and the Visual Analogue Scale (VAS) were used as measures for pain and functional disability. Post-test ODQ readings showed no significant difference for pain-related function whilst VAS readings revealed a significant improvement in pain levels in all three groups, with the control group showing the best scores. However, the six-month follow-up scores showed that only the modified Pilates group continued to improve. At this stage, the control group was beginning to regress and the back exercise group was almost back to baseline measures. It was therefore concluded that core stability exercises have better long-term effects than traditional back exercisespeer-reviewe

    What are Biofilms?

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    AOSpine—Spine Trauma Classification System: The Value of Modifiers: A Narrative Review With Commentary on Evolving Descriptive Principles

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    Study Design: Narrative review. Objectives: To describe the current AOSpine Trauma Classification system for spinal trauma and highlight the value of patient-specific modifiers for facilitating communication and nuances in treatment. Methods: The classification for spine trauma previously developed by The AOSpine Knowledge Forum is reviewed and the importance of case modifiers in this system is discussed. Results: A successful classification system facilitates communication and agreement between physicians while also determining injury severity and provides guidance on prognosis and treatment. As each injury may be unique among different patients, the importance of considering patient-specific characteristics is highlighted in this review. In the current AOSpine Trauma Classification, the spinal column is divided into 4 regions: the upper cervical spine (C0-C2), subaxial cervical spine (C3-C7), thoracolumbar spine (T1-L5), and the sacral spine (S1-S5, including coccyx). Each region is classified according to a hierarchical system with increasing levels of injury or instability and represents the morphology of the injury, neurologic status, and clinical modifiers. Specifically, these clinical modifiers are denoted starting with M followed by a number. They describe unique conditions that may change treatment approach such as the presence of significant soft tissue damage, uncertainty about posterior tension band injury, or the presence of a critical disc herniation in a cervical bilateral facet dislocation. These characteristics are described in detail for each spinal region. Conclusions: Patient-specific modifiers in the AOSpine Trauma Classification highlight unique clinical characteristics for each injury and facilitate communication and treatment between surgeons
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