Pathophysiology Pathophysiology Decreased volume of spinal canal due to osteoarthritis of disc and facet joints. Less space available for neural elements. Mechanical irritation can incite a local inflammatory response Vascular and conduction changes of neural elements are thought to be responsible for symptoms. Chronic neural compression leads to edema, demyelination, and wallerian degeneration of the afferent and efferent fibers. Substance P has been proposed as a pain modulator related to involvement of the nerve root and dorsal root ganglion. Central stenosis Ligamentum flavum buckling or hypertrophy. Superior facet process hypertrophy or osteophyte formation. Intervertebral disc protrusion or osteophyte formation Lateral recess stenosis Entrance zone: Hypertrophy of the superior articular process Mid zone: Fibrocartilage overgrowth of a pars interarticularis defect. Formainal stenosis: Pedicular kinking from scoliosis, foraminal disc herniations, or foraminal collapse secondary to collapse of disc space.

Physical and Psychosocial Risk Factors for Low Back Pain Repetitive lifting or pulling Exposure to prolonged industrial or vehicular vibrations Obesity Sagittal malalignment Pregnancy Cigarette smoking Lack of exercise

Symptoms and Signs Cervical and lumbar spinal stenosis can coexist; therefore a detailed examination of both areas and the upper and lower extremities is essential. Symptoms –Low back pain(95%), claudication(91%), leg pain (71%), leg weakness(33%) –Exacerbated by walking; relieved by sitting or leaning forward –May have radicular pain with herniated disc Signs –Paucity of neurologic deficits despite profound symptoms –May have positive femoral nerve stretch test or straight leg raise with disc herniation

Nonspinal Causes of Pain Musculoskeletal Infectious Neoplastic Degenerative –Spondylosis –Spinal stenosis –Degenerative disc disease –Facet syndrome –Costochondritis Metabolic –Osteoporosis –Osteomalacia Trumatic Inflammatory –Ankylosing spondylitis Deformity –Scoliosis –Kyphosis Muscular –Strain –Fibromyalgia –Polymyalgia rheumatica Neurogenic Thoracic disc herniation Neoplasms –Extradural –Intradural –Extramedullary –Intramedullary Arteriovenous malformation Inflammatory –Herpes zoster Postthoracotomy syndrome Intercostal neuralgia Referred pain Intrathoracic –Cardiovascular –Pulmonary –Mediastinal Intraabdomina –Gastrointestinal –Hepatobiliary Retroperitoneal –Renal –Tumor –Aneurysm

Imaging Studies MRI best study for herniated nucleus pulposus diagnosis CT still most used worldwide Discography: Relevant adjunctive study Discography/CT scan for annular pathology Myelography/CT: Age, co-pathology Important factors –Surgeon ability to interpret own studies –Imaging: A tool that can correlate pain with pathology

Discography Rationale –Pain provoked by irritating sensitized nerve endings in the disc –Nerve endings in end plates and annulus Limitations –Some sensitized nerve endings in disc not stimulated –Injection into nucleus; if no fissures extend into annulus, pain may not be reproduced during discography Complications –Infection: 0 to 1.3% of patients –Nerve root irritation –Allergic reaction –Retroperitoneal hemorrhage –Increase in pain in patients with chronic pain