The Underlying Mechanism of Spinal Manipulative Therapy and the Effect of Pain on Physical Outcome Measures

The Underlying Mechanism of Spinal Manipulative Therapy and the Effect of Pain on Physical Outcome Measures

The Underlying Mechanism of Spinal Manipulative Therapy and the Effect of Pain on Physical Outcome Measures

The purpose of this study is to compare changes in spinal stiffness and back muscle activity between spinal manipulative therapy (SMT) responders, non-responders and asymptomatic participants. Additionally, the investigators wanted to compare the amount of lumbar degeneration between SMT responders, non-responders and asymptomatic participants. This study also determines if the presence of pain modifies post-SMT spinal stiffness and back muscle activity.

SMT is a common manual therapy for treating patients with mechanical low back pain (LBP). SMT is defined as a high velocity, low amplitude thrust technique. Specifically, the clinician stands beside a supine patient. The patient is passively side-bent towards the side to be manipulated. The clinician passively rotates the patient and then delivers a high velocity, low amplitude thrust to the anterior superior iliac spine in a posteroinferior direction. SMT is indicated for patients with LBP judged to have spinal hypomobility or malalignment. Recently, our collaborators have discovered that LBP subjects who benefit from SMT can be identified prior to treatment by a five-item clinical prediction rule. Compared to non-responders, those who respond to SMT have: 1) more than 30% decrease in the modified Oswestry Disability Index score, 2) a significant and immediate decrease in spinal stiffness, and 3) a concurrent change in lumbar multifidus muscle activity. Taken together, the physical changes experienced by SMT responders alone provide an unique opportunity to better understand the mechanisms underlying SMT. Since spinal stiffness is an important physical indicator of SMT response, it is important to understand the causal relation between pain, paraspinal/trunk muscle activity and spinal stiffness. Although research has shown positive correlation between pain and muscle activity, and between paraspinal muscle activity and spinal stiffness, the causal relation between pain, paraspinal/trunk muscle activity and spinal stiffness remains unknown. Given this background, an induction of temporary benign experimental pain to asymptomatic individuals can help clarify such causal relation and improve our understanding of physical responses in responders following pain resolution by SMT.

spinal manipulative therapy, low back pain, experimental pain, spinal stiffness, lumbar multifidus, degeneration

To investigate the effects of high velocity, low amplitude lumbopelvic spinal manipulative therapy on spinal stiffness and back muscle activity.

To investigate the sequential changes in spinal stiffness and back muscle activity of asymptomatic participants over time without any intervention. Participants of this arm can volunteer for an additional experimental pain protocol after their third visit (at 1 week) to investigate the effects of experimental pain on the changes of spinal stiffness and back muscle activity using a randomized crossover design (injecting 5% hypertonic saline or 0.9% isotonic saline to the interspinous ligaments at L3 to L5 levels in random order in two additional visits).

High velocity, low amplitude spinal manipulative therapy (HVLA-SMT) will be provided to the lumbopelvic region on both sides.

A randomized crossover design is used to investigate the changes in spinal stiffness and back muscle activity of asymptomatic participants following an experimental pain induction procedure. Specifically, asymptomatic participants attend two separate sessions 5 days apart. Participants will receive 0.3 ml of 5% hypertonic saline or 0.9% isotonic saline in random order into the interspinous ligaments at L3 to L5 levels. The resulting temporal changes in pain intensity, spinal stiffness and trunk muscle activity following saline injections will be monitored. During the second session, the participants will undergo the same procedures but with the previously unused saline concentration.

It is a questionnaire to assess the participants' perceived low back pain related functional disability.

Using the rehabilitative ultrasound imaging to measure lumbar multifidus muscle thickness at rest and during an automatic muscle contraction.

The spinal stiffness of participants will be measured by a validated mechanical indentation machine. Briefly, a 60 N load will be applied to the third lumbar spinous process and the corresponding spinal tissue deformations will be measured. The spinal stiffness will be calculated from the force-displacement curve of each indentation.

Electromyography of abdominal and erector spinae muscles during spinal stiffness testing will be measured.

It records the anatomical features of the lumbar spine and the changes in lumbar disc diffusion during the first session (an expected average of 1-hour duration).

It measures the subjective perception of exertion during the spinal stiffness test and muscle testings

Measurement of lumbar multifidus muscle thickness by rehabilitative ultrasound imaging in the pain induction experiment

Using the rehabilitative ultrasound imaging to measure lumbar multifidus muscle thickness at rest and during an automatic muscle contraction.

Before the injection, immediately after the injection, and 25-minute after the injection in each session

The spinal stiffness of participants will be measured by a validated mechanical indentation machine. Briefly, a 60 N load will be applied to the third lumbar spinous process and the corresponding spinal tissue deformations will be measured. The spinal stiffness will be calculated from the force-displacement curve of each indentation.

Before the injection, immediately after the injection, and 25-minute after the injection in each session

Electromyography of abdominal and erector spinae muscles during spinal stiffness testing will be measured.

Before the injection, immediately after the injection, and 25-minute after the injection in each session

Before the injection, immediately after the injection, and 25-minute after the injection in each session

Before the injection, immediately after the injection, and 25-minute after the injection in each session

It is a questionnaire to assess the participants' perceived low back pain related functional disability.

It measures the subjective perception of exertion during the spinal stiffness test and muscle testings

Before the injection, immediately after the injection, and 25-minute after the injection in each session

Inclusion Criteria: Self ambulatory participants with or without acute/chronic LBP. LBP is defined as pain or discomfort between costal margin and above the gluteal folds, with or without leg pain. All the included LBP participants must have modified Oswestry Disability Index score > 12% Have the ability to lie prone for at least 20 minutes. Asymptomatic participants should be free from LBP at the time of visit. Exclusion Criteria: With medical 'red flag' conditions such as cancer, cauda equine syndrome, spinal infection, fracture or systemic disease History of arm surgery, shoulder or arm pain that may hinder the arm lifting in prone History of orthopedic or neurological surgery to the spine, pelvis or hips Inflammatory or active infective processes involving spine or shoulder Spondylolisthesis, ankylosing spondylitis, scoliosis of greater than 20 degrees (Cobb's angle) Pregnancy Osteoporosis Neurologic deficit or signs of nerve root compression Congenital spinal disorder (such as spina bifida), Participation in competitive sports more than 3 times per week History of spinal manipulation or lumbar multifidus stabilization exercise training within the past 4 weeks Additional exclusion criteria for asymptomatic participants include: back pain in the preceding year, or exceeding 1 week; missed at least 1 work day because of back pain; and consultation for a back problem.