PathophysiologyPathophysiology

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 f

or symptoms.• Chronic neural compression leads to edema, demyelination, and wallerian degenera

tion of the afferent and efferent fibers.• Substance P has been proposed as a pain modulator related to involvement of the n

erve root and dorsal root ganglion.Central stenosis• Ligamentum flavum buckling or hypertrophy.• Superior facet process hypertrophy or osteophyte formation.• Intervertebral disc protrusion or osteophyte formationLateral 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 Physical and Psychosocial Risk Factors for Low Back PainLow Back Pain

• Repetitive lifting or pulling• Exposure to prolonged industrial or

vehicular vibrations• Obesity• Sagittal malalignment• Pregnancy• Cigarette smoking• Lack of exercise

Symptoms and SignsSymptoms 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 we

akness(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 PainNonspinal Causes of PainMusculoskeletal• 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 neuralgiaReferred pain• Intrathoracic

– Cardiovascular– Pulmonary– Mediastinal

• Intraabdomina– Gastrointestinal– Hepatobiliary

• Retroperitoneal– Renal – Tumor– Aneurysm

Imaging StudiesImaging 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

DiscographyDiscography

• 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