ISB recommendation on definitions of joint coordinate system of various joints for the reporting of human joint motion—part I: ankle, hip, and spine

In view of the current level of knowledge and the numerous treatment possibilities, none of the existing classification systems of thoracic and lumbar injuries is completely satisfactory As a result of more than a decade of consideration of the subject matter and a review of 1445 consecutive thoracolumbar injuries, a comprehensive classification of thoracic and lumbar injuries is proposed The classification is primarily based on pathomorphological criteria Categories are established according to the main mechanism of injury, pathomorphological uniformity, and in consideration of prognostic aspects regarding healing potential The classification reflects a progressive scale of morphological damage by which the degree of instability is determined The severity of the injury in terms of instability is expressed by its ranking within the classification system A simple grid, the 3-3-3 scheme of the AO fracture classification, was used in grouping the injuries This grid consists of three types: A, B, and C Every type has three groups, each of which contains three subgroups with specifications The types have a fundamental injury pattern which is determined by the three most important mechanisms acting on the spine: compression, distraction, and axial torque Type A (vertebral body compression) focuses on injury patterns of the vertebral body Type B injuries (anterior and posterior element injuries with distraction) are characterized by transverse disruption either anteriorly or posteriorly Type C lesions (anterior and posterior element injuries with rotation) describe injury patterns resulting from axial torque The latter are most often superimposed on either type A or type B lesions Morphological criteria are predominantly used for further subdivision of the injuries Severity progresses from type A through type C as well as within the types, groups, and further subdivisions The 1445 cases were analyzed with regard to the level of the main injury, the frequency of types and groups, and the incidence of neurological deficit Most injuries occurred around the thoracolumbar junction The upper and lower end of the thoracolumbar spine and the T 10 level were most infrequently injured Type A fractures were found in 661 %, type B in 145%, and type C in 194% of the cases Stable type Al fractures accounted for 347% of the total Some injury patterns are typical for certain sections of the thoracolumbar spine and others for age groups The neurological deficit, ranging from complete paraplegia to a single root lesion, was evaluated in 1212 cases The overall incidence was 22% and increased significantly from type to type: neurological deficit was present in 14% of type A, 32% of type B, and 55% of type C lesions Only 2% of the Al and 4% of the A2 fractures showed any neurological deficit The classification is comprehensive as almost any injury can be itemized according to easily recognizable and consistent radiographic and clinical findings Every injury can be defined alphanumerically or by a descriptive name The classification can, however, also be used in an abbreviated form without impairment of the information most important for clinical practice Identification of the fundamental nature of an injury is facilitated by a simple algorithm Recognizing the nature of the injury, its degree of instability, and prognostic aspects are decisive for the choice of the most appropriate treatment Experience has shown that the new classification is especially useful in this respect

A comprehensive classification of thoracic and lumbar injuries

Study Design. The contribution of transversus abdominis to spinal stabilization was evaluated indirectly in people with and without low back pain using an experimental model identifying the coordination of trunk muscles in response to a disturbance to the spine produced by arm movement.

Inefficient muscular stabilization of the lumbar spine associated with low back pain : A motor control evaluation of transversus abdominis

Basic biomechanical measurements of bone: a tutorial.

Background: We studied the incidence, prevalence, and radiographic progression of symptomatic adjacent-segment disease, which we defined as the development of new radiculopathy or myelopathy referable to a motion segment adjacent to the site of a previous anterior arthrodesis of the cervical spine. Methods: A consecutive series of 374 patients who had a total of 409 anterior cervical arthrodeses for the treatment of cervical spondylosis with radiculopathy or myelopathy, or both, were followed for a maximum of twenty-one years after the operation. The annual incidence of symptomatic adjacent-segment disease was defined as the percentage of patients who had been disease-free at the start of a given year of follow-up in whom new disease developed during that year. The prevalence was defined as the percentage of all patients in whom symptomatic adjacent-segment disease developed within a given period of follow-up. The natural history of the disease was predicted with use of a Kaplan-Meier survivorship analysis. The hypothesis that new disease at an adjacent level is more likely to develop following a multilevel arthrodesis than it is following a single-level arthrodesis was tested with logistic regression. Results: Symptomatic adjacent-segment disease occurred at a relatively constant incidence of 2.9 percent per year (range, 0.0 to 4.8 percent per year) during the ten years after the operation. Survivorship analysis predicted that 25.6 percent of the patients (95 percent confidence interval, 20 to 32 percent) who had an anterior cervical arthrodesis would have new disease at an adjacent level within ten years after the operation. There were highly significant differences among the motion segments with regard to the likelihood of symptomatic adjacent-segment disease (p < 0.0001); the greatest risk was at the interspaces between the fifth and sixth and between the sixth and seventh cervical vertebrae. Contrary to our hypothesis, we found that the risk of new disease at an adjacent level was significantly lower following a multilevel arthrodesis than it was following a single-level arthrodesis (p < 0.001). More than two-thirds of all patients in whom the new disease developed had failure of nonoperative management and needed additional operative procedures. Conclusions: Symptomatic adjacent-segment disease may affect more than one-fourth of all patients within ten years after an anterior cervical arthrodesis. A single-level arthrodesis involving the fifth or sixth cervical vertebra and preexisting radiographic evidence of degeneration at adjacent levels appear to be the greatest risk factors for new disease. Therefore, we believe that all degenerated segments causing radiculopathy or myelopathy should be included in an anterior cervical arthrodesis. Although our findings suggest that symptomatic adjacent-segment disease is the result of progressive spondylosis, patients should be informed of the substantial possibility that new disease will develop at an adjacent level over the long term.

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Radiculopathy and Myelopathy at Segments Adjacent to the Site of a Previous Anterior Cervical Arthrodesis

Combining orthopedic surgery with biomechanical engineering, this reference and teaching text reviews and analyzes the clinical and scientific data on the mechanics of the human spine. This edition adds new material on vibration (i.e. road driving) and its effect on the spine; anatomy and kinematics

Clinical Biomechanics of the Spine

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

The stabilizing system of the spine. Part I. Function, dysfunction, adaptation, and enhancement.

SummaryThe neutral zone is a region of intervertebral motion around the neutral posture where little resistance is offered by the passive spinal column Several studies—in vitro cadaveric, in vivo animal, and mathematical simulations—have shown that the neutral zone is a parameter that correlates we

The stabilizing system of the spine. Part II. Neutral zone and instability hypothesis.

Clinical spinal instability and low back pain

STUDY DESIGN: This study examined the coactivation of trunk flexor and extensor muscles in healthy individuals. The experimental electromyographic data and the theoretical calculations were analyzed in the context of mechanical stability of the lumbar spine. OBJECTIVES: To test a set of hypotheses pertaining to healthy individuals: 1) that the trunk flexor-extensor muscle coactivation is present around a neutral spine posture, 2) that the coactivation is increased when the subject carries a load; and 3) that the coactivation provides the needed mechanical stability to the lumbar spine. SUMMARY OF BACKGROUND DATA: Theoretically, antagonistic trunk muscle coactivation is necessary to provide mechanical stability to the human lumbar spine around its neutral posture. No experimental evidence exists, however, to support this hypothesis. METHODS: Ten individuals executed slow trunk flexion-extension tasks, while six muscles on the right side were monitored with surface electromyography: external oblique, internal oblique, rectus abdominis, multifidus, lumbar erector spinae, and thoracic erector spinae. Simple, but realistic, calculations of spine stability also were performed and compared with experimental results. RESULTS: Average antagonistic flexor-extensor muscle coactivation levels around the neutral spine posture as detected with electromyography were 1.7 +/- 0.8% of maximum voluntary contraction for no external load trials and 2.9 +/- 1.4% of maximum voluntary contraction for the trials with added 32-kg mass to the torso. The inverted pendulum model based on static moment equilibrium criteria predicted no antagonistic coactivation. The same model based on the mechanical stability criteria predicted 1.0% of maximum voluntary contraction coactivation of flexors and extensors with zero load and 3.1% of maximum voluntary contraction with a 32-kg mass. The stability model also was run with zero passive spine stiffness to simulate an injury. Under such conditions, the model predicted 3.4% and 5.5% of maximum voluntary contraction of antagonistic muscle coactivation for no extra load and the added 32 kg, respectively. CONCLUSIONS: This study demonstrated that antagonistic trunk flexor-extensor muscle coactivation was present around the neutral spine posture in healthy individuals. This coactivation increased with added mass to the torso. Using a biomechanical model, the coactivation was explained entirely on the basis of the need for the neuromuscular system to provide the mechanical stability to the lumbar spine.

Manohar M. Panjabi

Papers

Clinical Biomechanics of the Spine

The stabilizing system of the spine. Part I. Function, dysfunction, adaptation, and enhancement.

The stabilizing system of the spine. Part II. Neutral zone and instability hypothesis.

Clinical spinal instability and low back pain

Stabilizing function of trunk flexor-extensor muscles around a neutral spine posture.