Neural Control and Mechanosensation in Spine Muscle

Low back pain (LBP) is a complex condition that affects 65-85% of the population, and is the leading musculoskeletal condition contributing to disability in the United States. Disc injury is the most common injury and 75% of individuals undergoing surgical and rehabilitative interventions for this condition experience suboptimal or poor outcomes. These patients demonstrate disability and deficits in functional capacity, and paraspinal muscles in these individuals have been shown to be altered in volume, composition, and mechanical properties. These maladaptive changes influence the ability for the muscle to respond appropriately to rehabilitation efforts in a subgroup of individuals with chronic back pain who do not demonstrate the expected acute activation responses to exercise. While the structural and adaptive capacities of healthy muscle are well understood, pathological muscle recovery and activation deficits are less clear and may be influenced by neurogenic and/or muscle specific impairments. To address this gap in knowledge, the purpose of this trial is to compare central and peripheral origins of impaired activation in individuals with chronic disc injury who do, and do not respond to exercise. Experiment 1 will use a novel functional MRI technique and electromyographic measurements to compare responder and non-responder groups in patients with chronic lumbar disc injury undergoing standard physical therapy. Experiment 2 will compare corticomotor excitability and intracortical inhibition and facilitation between individuals who are undergoing physical therapy or surgery who do and do not respond to exercise. Experiment 3 will compare ex vivo passive and active mechanical responses, and transcriptomics from intraoperative multifidus biopsies of patients undergoing spinal surgery for chronic lumbar disc injury to evaluate muscle mechanotransduction. These experiments will elucidate the neurogenic and muscle-specific contributions to muscle adaptation in the presence of chronic lumbar spine pathology and pain.

Inclusion criteria

• Surgical group:
• Individuals diagnosed with chronic disc injury (symptoms > 3 months),
• Individuals planning to undergo a spinal surgery to address the diagnosis of chronic disc injury

Physical Therapy Group-

• Individuals diagnosed with chronic disc injury (symptoms >3 months),
• Individuals initiating an exercise-based physical therapy program to address the diagnosis of chronic disc injury

Healthy Control group -

• Individuals with no history of chronic back pain (interfering pain lasting >3 months) within the past 3 years,
• no significant spinal pathology beyond normal age-related degenerative changes

Exclusion criteria

• Surgery/Physical therapy groups-History of lumbar spine surgery
• Diabetes
• Neuromuscular diseases
• Epilepsy or other seizure disorder -Healthy control group -
• History of lumbar spine surgery
• History of interfering pain lasting >3 months
• Diabetes
• Neuromuscular diseases
• Epilepsy or other seizure disorder