Vertebral/Manipulation
Manipulation Facilitates Motoneuron Excitability
Despite an increase in the use of spinal manipulation for low back pain (LBP), the mechanism for its efficacy at reducing pain and muscle spasms is not fully understood. Manipulation may involve a decrease of resting motoneuron activity, leading to a decrease in hypertonicity.
To evaluate the effects of lumbar spinal manipulation on motoneuron excitability, the authors utilized a process called transcranial magnetic stimulation (TMS) to measure the amplitude of motor-evoked potentials (MEPs) in the right gastrocnemius muscle of 24 subjects who were in either a control or intervention group.
To evaluate the effects of lumbar spinal manipulation on motoneuron excitability, the authors utilized a process called transcranial magnetic stimulation (TMS) to measure the amplitude of motor-evoked potentials (MEPs) in the right gastrocnemius muscle of 24 subjects who were in either a control or intervention group.
The intervention consisted of a single side-posture L5-S1 high-velocity, low-amplitude spinal manipulation, given to 12 patients. The 12 patients in the control group were placed in the side-posture position, without any lower-limb flexion or trunk torque; no contact was made on the spine and no manual force was introduced.
Results: MEP amplitudes were "significantly facilitated" for 20 to 60 seconds following spinal manipulation and continued to remain facilitated for up to five minutes, although at a lower amplitude. The control group showed no significant change in MEP amplitude after side positioning.
Conclusion: A significant facilitation, although temporary, appears following spinal manipulation when motoneuron pool excitability is measured by central corticospinal activation using TMS. Therefore, central motor facilitation was demonstrated as a neurophysical reaction to manipulation. This is the first study to report on these central motor changes after spinal manipulation, according to the authors; the next step will be to compare this response in healthy individuals vs. those with LBP.
Results: MEP amplitudes were "significantly facilitated" for 20 to 60 seconds following spinal manipulation and continued to remain facilitated for up to five minutes, although at a lower amplitude. The control group showed no significant change in MEP amplitude after side positioning.
Conclusion: A significant facilitation, although temporary, appears following spinal manipulation when motoneuron pool excitability is measured by central corticospinal activation using TMS. Therefore, central motor facilitation was demonstrated as a neurophysical reaction to manipulation. This is the first study to report on these central motor changes after spinal manipulation, according to the authors; the next step will be to compare this response in healthy individuals vs. those with LBP.
Neurophysiological Responses to Lumbar Spinal Manipulation
Research has uncovered a variety of pain generators present in spinal tissues. The presence of mechanosensitive and nociceptive afferent fibers in spinal tissues, and subsequent research documenting the role of afferent stimulation in pain production and neuromuscular stabilization of the spine, provide a possible framework for investigating the mechanisms of spinal manipulative therapy (SMT).
Only recently, however, have the mechanical and physiological influence of spinal manipulative therapy begun to be quantified experimentally.
The purpose of this study was to simultaneously quantify vertebral motions and neuromuscular and spinal nerve root responses to mechanical force, manually assisted, short-lever spinal manipulative thrusts (SMTs). In the study, four patients underwent lumbar laminarthrectomy to decompress the central spinal canal and neuroforamina. Prior to decompression, intraosseous pins were affixed to the lumbar spinous process, with accelerometers mounted to the pins. Following decompression, electrodes were inserted into the musculature adjacent to the pins and around the left and right S1 spinal nerve roots. With the spine exposed, SMTs were delivered internally to the lumbosacral spinous process and facet joints, and externally by contacting the skin overlying the respective spinal landmarks using two force settings and two force vectors.
SMTs resulted in positive electromyographic (EMG) and compound action potential (CAP) responses, usually lasting several milliseconds in duration. Multiple responses were observed in numerous cases. The time between the initiation of the mechanical thrust and the neurophysiologic response to internal and external SMT thrusts ranged from 2.4 to 18.1 milliseconds for EMG responses, and 2.4 to 28.6 milliseconds for CAP responses.
The researchers conclude: "Spinal manipulation results in measurable biomechanical and neurophysiologic responses, which appear to be individualized among patients. The vertebral motions that occur (rotations and translations) and resulting spinal nerve root and muscular reflex responses appear to be temporally related to the applied force during SMT. These findings suggest that intersegmental motions produced by spinal manipulation may play a prominent role in eliciting physiologic responses."
The purpose of this study was to simultaneously quantify vertebral motions and neuromuscular and spinal nerve root responses to mechanical force, manually assisted, short-lever spinal manipulative thrusts (SMTs). In the study, four patients underwent lumbar laminarthrectomy to decompress the central spinal canal and neuroforamina. Prior to decompression, intraosseous pins were affixed to the lumbar spinous process, with accelerometers mounted to the pins. Following decompression, electrodes were inserted into the musculature adjacent to the pins and around the left and right S1 spinal nerve roots. With the spine exposed, SMTs were delivered internally to the lumbosacral spinous process and facet joints, and externally by contacting the skin overlying the respective spinal landmarks using two force settings and two force vectors.
SMTs resulted in positive electromyographic (EMG) and compound action potential (CAP) responses, usually lasting several milliseconds in duration. Multiple responses were observed in numerous cases. The time between the initiation of the mechanical thrust and the neurophysiologic response to internal and external SMT thrusts ranged from 2.4 to 18.1 milliseconds for EMG responses, and 2.4 to 28.6 milliseconds for CAP responses.
The researchers conclude: "Spinal manipulation results in measurable biomechanical and neurophysiologic responses, which appear to be individualized among patients. The vertebral motions that occur (rotations and translations) and resulting spinal nerve root and muscular reflex responses appear to be temporally related to the applied force during SMT. These findings suggest that intersegmental motions produced by spinal manipulation may play a prominent role in eliciting physiologic responses."
Neuromechanical Vertebral Motion During Manipulation of the Lumbar Spine
While the clinical outcomes of spinal manipulation (SM) and chiropractic adjustments are the subject of much investigation, basic research into the mechanisms of these procedures remains poorly understood.
Because spinal manipulation is a mechanical intervention, it is reasonable to assume that its benefits may be derived from the mechanical properties of the force applied to the body, the body's response to such force, or a combination of these (and other) factors. Biomechanical investigations of spinal manipulation may help researchers, educators and clinicians better understand the mechanisms of SM, develop SM techniques, train clinicians more effectively, and minimize risks while achieving better patient results.
The objective of this study was to quantify vertebral and intervertebral lumbar spinal motions that occur during spinal manipulation in a live human subject. Four patients (two male, two female) undergoing decompressive spinal surgery volunteered to participate. While under anesthesia, the patients were subjected to a series of 14 mechanical force, manually assisted (Activator instrument) SM thrusts delivered at different facet joints and contact points. Effects were measured using accelerometers affixed to surgical pins fixed to the lumbar spinous process.
Results: Peak-to-peak medial-lateral (ML), posterior-anterior (PA) and axial (AX) vertebral displacements increased significantly with increased applied force. Pronounced coupling was observed between all axes for thrusts delivered over the facet joints; for thrusts delivered to the spinous processes, only the AX and PA axes showed a significant degree of coupling. Posterior-anterior vertebral displacements decreased significantly when the facet joint contact point was caudal to the surgical pin, compared to contact cranial to the pin. Spinal manipulative thrusts over the spinous processes produced significantly greater PA and AX displacements compared to ML displacements. The combined medial-lateral, posterior-anterior and axial peak-to-peak displacements for the force settings and contact points ranged from 0.15 to 0.66 mm, 0.15 to 0.81 mm, and 0.07 to 0.45 mm, respectively.
The authors conclude that their measurements of the spine during the application of spinal manipulative thrusts "corroborate previous spinous process measurements in human subjects." They add, "Our findings demonstrate that PA, ML, and AX spinal motions are coupled and dependent on applied force and contact point."
The objective of this study was to quantify vertebral and intervertebral lumbar spinal motions that occur during spinal manipulation in a live human subject. Four patients (two male, two female) undergoing decompressive spinal surgery volunteered to participate. While under anesthesia, the patients were subjected to a series of 14 mechanical force, manually assisted (Activator instrument) SM thrusts delivered at different facet joints and contact points. Effects were measured using accelerometers affixed to surgical pins fixed to the lumbar spinous process.
Results: Peak-to-peak medial-lateral (ML), posterior-anterior (PA) and axial (AX) vertebral displacements increased significantly with increased applied force. Pronounced coupling was observed between all axes for thrusts delivered over the facet joints; for thrusts delivered to the spinous processes, only the AX and PA axes showed a significant degree of coupling. Posterior-anterior vertebral displacements decreased significantly when the facet joint contact point was caudal to the surgical pin, compared to contact cranial to the pin. Spinal manipulative thrusts over the spinous processes produced significantly greater PA and AX displacements compared to ML displacements. The combined medial-lateral, posterior-anterior and axial peak-to-peak displacements for the force settings and contact points ranged from 0.15 to 0.66 mm, 0.15 to 0.81 mm, and 0.07 to 0.45 mm, respectively.
The authors conclude that their measurements of the spine during the application of spinal manipulative thrusts "corroborate previous spinous process measurements in human subjects." They add, "Our findings demonstrate that PA, ML, and AX spinal motions are coupled and dependent on applied force and contact point."
Nenhum comentário:
Postar um comentário