Pathophysiology of Lumbar Spondylosis
Lumbar spondylosis is a chronic, degenerative condition of the lumbar spine characterized by intervertebral disc degeneration and facet joint arthropathy, leading to structural changes that can cause pain and neurological symptoms. 1
Primary Degenerative Process
The pathophysiology of lumbar spondylosis follows a cascade of degenerative changes:
Initial Disc Degeneration:
- Begins with biochemical changes in the nucleus pulposus
- Loss of proteoglycans and water content in the disc
- Decreased disc height and altered biomechanical properties
- Increased stress on surrounding structures
Facet Joint Involvement:
- Increased load on facet joints due to disc height loss
- Development of facet hypertrophy and arthropathy
- Formation of osteophytes at vertebral margins
Structural Consequences:
- Disc bulging and potential herniation
- Ligamentum flavum hypertrophy
- Foraminal narrowing
- Potential development of spinal canal stenosis
- Segmental instability in advanced cases
Biomechanical Factors
- Altered load distribution across spinal segments
- Abnormal motion patterns between vertebrae
- Increased shear forces, particularly at L4-L5 and L5-S1 levels
- Development of segmental instability that may progress to spondylolisthesis 2
Neurological Implications
Degenerative changes can lead to compression of neural structures through:
- Direct compression from disc bulging/herniation
- Foraminal stenosis from facet hypertrophy and osteophyte formation
- Central canal stenosis from combined disc bulging, facet hypertrophy, and ligamentum flavum thickening
- Potential development of neurogenic claudication in cases with spinal stenosis 3
Risk Factors
- Advanced age (primary risk factor)
- Genetic predisposition
- Occupational factors (heavy lifting, vibration exposure)
- Previous trauma or surgery
- Elevated pedicle-facet joint angles and W-type facet joints (predisposing to multilevel involvement) 3
Clinical Manifestations
The clinical presentation varies based on the structures affected:
- Axial Back Pain: From degenerative disc and facet joint changes
- Radicular Pain: From nerve root compression (typically unilateral)
- Neurogenic Claudication: From spinal stenosis (typically bilateral)
- Motor/Sensory Deficits: In cases with significant neural compression
Diagnostic Imaging
Imaging reveals characteristic findings:
- Radiography: Shows disc space narrowing, osteophyte formation, facet hypertrophy, and potential spondylolisthesis
- MRI: Gold standard for evaluating soft tissue involvement, neural compression, and extent of stenosis 4
- CT/CT Myelography: Useful for evaluating bony details, particularly in patients with contraindications to MRI 4
Progression and Complications
Lumbar spondylosis can progress to:
- Degenerative spondylolisthesis (vertebral displacement)
- Spinal instability
- Spinal stenosis with neurogenic claudication
- In rare cases, cauda equina syndrome
Management Approach
Management should follow a stepwise approach:
Conservative Treatment (First-line):
- NSAIDs or COX-2 inhibitors for pain control
- Physical therapy focusing on core strengthening and flexibility
- Activity modification
- Patient education on ergonomics and self-management
Interventional Procedures (For persistent symptoms):
- Epidural steroid injections
- Transforaminal injections
- Facet joint injections
Surgical Management (For refractory cases with significant neural compression or instability):
- Decompression procedures for stenosis
- Fusion with or without instrumentation for instability or spondylolisthesis
- Total disc replacement in selected cases 5
Important Considerations
- Lumbar spondylosis is often asymptomatic, with radiographic changes frequently not correlating with clinical symptoms
- Treatment decisions should be based on symptom severity and functional limitations rather than imaging findings alone
- Multilevel involvement may require more extensive surgical intervention when conservative measures fail 3
- Careful evaluation for potential spinal infection should be considered in cases with atypical presentation or risk factors 4
Understanding the pathophysiological cascade of lumbar spondylosis is essential for appropriate clinical management and for distinguishing it from other causes of low back pain that may require different treatment approaches.