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
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Infection: 0 to 1.3% of patients
Nerve root irritation
Allergic reaction
Retroperitoneal hemorrhage
Increase in pain in patients with chronic pain