DISCOGENIC BACK PAIN
Internal Disc Disruption | Degenerative Disc Disease | Mechanical Back Pain
Pfirrmann MRI Grading
Critical Must-Knows
- Discogenic pain = internal disc disruption with intact annulus but painful fissures
- Diagnosis requires concordant provocation discography - controversial gold standard
- 80% improve with 6-12 months conservative care - surgery last resort only
- Fusion indicated for single-level disease with concordant pain reproduction
- Disc replacement for preserved disc height, no facet arthropathy, under 60 years
Examiner's Pearls
- "Key distinction: discogenic pain (internal) vs herniation (external compression)
- "Modic changes on MRI correlate with discogenic pain (Type 1 = inflammation)
- "High-Intensity Zone (HIZ) = annular tear on MRI - 80% sensitivity for discogenic pain
- "SPORT trial: fusion similar outcomes to intensive PT at 4 years for degenerative disease
Clinical Imaging
Imaging Gallery
Critical Discogenic Back Pain Exam Points
Diagnosis Challenge
No pathognomonic sign exists. Diagnosis is clinical exclusion plus provocative testing. Beware overdiagnosis - many asymptomatic adults have disc degeneration on MRI.
MRI Findings
Modic Type 1 changes (marrow edema) correlate best with pain. High-Intensity Zone (HIZ) = annular tear. Pfirrmann Grade 4-5 = advanced degeneration.
Conservative First
Minimum 6 months structured conservative care before surgery. 80% improve without intervention. Surgery for failed conservative care with concordant pain only.
Surgical Decision
Fusion vs disc replacement: Single-level, preserved height, under 60, no facet disease = consider arthroplasty. Otherwise fusion. Adjacent segment disease occurs in both.
Quick Decision Guide
| Clinical Scenario | MRI Findings | Treatment | Key Pearl |
|---|---|---|---|
| Young (under 40), single-level | Pfirrmann 3-4, HIZ+, Modic 1, preserved height | Intensive PT × 6 months, then consider disc replacement | Disc replacement preserves motion but needs intact facets |
| Middle-aged (40-60), single-level | Pfirrmann 4-5, Modic 1-2, moderate collapse | PT × 6 months, then consider ALIF/TLIF fusion | Fusion is gold standard - predictable pain relief |
| Older (over 60), multi-level | Pfirrmann 4-5, facet arthropathy, instability | PT, epidurals, avoid surgery unless neurological deficit | Multi-level fusion high morbidity - manage expectations |
MODICModic Changes on MRI
Memory Hook:MODIC changes = Marrow edema (Type 1) is the Most Painful type, converts to Osseous fat over time!
DISCOGENICDiagnostic Criteria for Discogenic Pain
Memory Hook:DISCOGENIC pain requires proving the DISC is the source - concordant provocation with all other causes excluded!
REPLACEIndications for Fusion vs Disc Replacement
Memory Hook:REPLACE criteria = when you can REPLACE the disc instead of fusing - young, single-level, intact facets, preserved height!
Overview and Epidemiology
Discogenic back pain represents internal disc disruption (IDD) - a degenerative condition where the nucleus pulposus loses hydration and the annulus fibrosus develops painful fissures, but without frank herniation causing neural compression. This is a mechanical and chemical pain syndrome from disrupted disc architecture.
Definition and Pathophysiology
Discogenic pain is axial low back pain originating from internal disc disruption with an intact but damaged annulus. The nucleus pulposus loses proteoglycan content, causing dehydration and loss of disc height. Annular tears propagate from the nucleus outward, reaching pain-sensitive outer annular fibers. Inflammatory cytokines (IL-6, TNF-alpha, PGE2) leak into tears, sensitizing nociceptors.
Pathological Cascade
Degenerative Progression
Nucleus pulposus loses proteoglycan and water content. Disc height maintained but internal architecture disrupted. Annular tears begin centrally.
Annular fissures propagate radially outward, reaching pain-sensitive outer one-third of annulus. High-Intensity Zone (HIZ) visible on MRI. Inflammatory mediators sensitize nociceptors.
Disc height loss with endplate changes (Modic). Biomechanical instability develops. Facet loading increases. May develop segmental instability.
Disc collapse with osteophyte formation. Paradoxical stabilization (auto-fusion). Pain may improve as motion decreases ("burning out").
Biochemical Factors
- Inflammatory cytokines: IL-1, IL-6, TNF-alpha
- Matrix metalloproteinases: Degrade collagen and proteoglycans
- Nerve growth factor (NGF): Ingrowth into normally aneural inner annulus
- Substance P: Nociceptive neurotransmitter in painful discs
Biomechanical Factors
- Loss of disc height: Increased facet loading
- Annular incompetence: Abnormal stress distribution
- Segmental instability: Excessive translation/rotation
- Endplate fracture: Modic Type 1 changes
Epidemiology and Natural History
Natural history is variable - approximately 80% of patients improve with conservative care over 6-12 months. The disc may "burn out" with progressive collapse and fibrosis, reducing pain. Younger patients with single-level disease and Modic Type 1 changes have worse prognosis.
Pathophysiology and Anatomy
Disc Anatomy
The intervertebral disc consists of three components:
Nucleus Pulposus
- Central gelatinous core - 80% water content in youth
- Proteoglycan matrix (aggrecan) retains water
- Type II collagen provides structure
- Aneural and avascular - nutrients via diffusion from endplates
Annulus Fibrosus
- Concentric lamellae of type I collagen fibers
- Outer one-third is innervated (sinuvertebral nerve, dorsal rami)
- 15-25 layers alternating 30-degree fiber orientation
- Anchors to vertebral endplates via Sharpey fibers
Cartilaginous Endplates
- Interface between vertebral body and disc
- Nutrient diffusion pathway for avascular disc
- Load distribution across vertebral body
- Injury causes Modic changes and disc degeneration
Innervation Pattern - Key to Discogenic Pain
The outer one-third of the annulus fibrosus is innervated by:
- Sinuvertebral nerve (recurrent branch of ventral ramus) - posterior and posterolateral annulus
- Grey rami communicantes - anterolateral annulus
- Dorsal rami - posterior annulus
Inner two-thirds is normally aneural. In discogenic pain, nerve growth factor (NGF) causes aberrant nerve ingrowth into inner annulus along radial tears, creating pain-sensitive tissue in normally aneural zones.
Biomechanics of Disc Degeneration
| Biomechanical Factor | Normal Disc | Degenerated Disc | Clinical Effect |
|---|---|---|---|
| Nucleus hydration | 80% water content, high proteoglycan | Reduced to 70% water, proteoglycan loss | Loss of shock absorption, increased annular stress |
| Intradiscal pressure | Normal pressure distribution | Altered load transfer, peak pressures | Annular tears propagate, endplate injury |
| Disc height | Normal height maintains lordosis | Collapse causes kyphosis | Facet overload, foraminal stenosis, sagittal imbalance |
| Motion segment stability | Controlled motion within physiologic range | Abnormal translation/rotation or stiffening | Instability (early) or autofusion (late) |
Load distribution: In flexion, sitting posture increases intradiscal pressure by 200-300% compared to standing. This explains why discogenic pain is characteristically worse with sitting and flexion activities.
Classification Systems
Pfirrmann MRI Classification
5-grade system based on T2 signal intensity, disc structure, and disc height. Most widely used MRI grading system for disc degeneration.
| Grade | Structure | Distinction | Height | Signal (T2) |
|---|---|---|---|---|
| Grade 1 | Homogeneous, bright white | Clear nucleus-annulus distinction | Normal | Hyperintense (bright) |
| Grade 2 | Inhomogeneous with horizontal band | Clear distinction maintained | Normal | Hyperintense with central horizontal band |
| Grade 3 | Inhomogeneous, grey | Unclear distinction | Normal to decreased | Intermediate (grey) |
| Grade 4 | Inhomogeneous, dark grey | Lost distinction | Decreased | Intermediate to hypointense (dark grey) |
| Grade 5 | Inhomogeneous, black | Lost distinction | Collapsed | Hypointense (black) |
Clinical Correlation
Grade 3-5 correlates with symptomatic disc degeneration, but Grade 3-4 changes are common in asymptomatic individuals over 40. Grade 4-5 with Modic Type 1 changes and HIZ has highest specificity for discogenic pain source.
Clinical Presentation and Assessment
History
- Axial low back pain: Mechanical, worse with flexion/sitting
- No radiculopathy: Pain does not radiate below knee
- Morning stiffness: Improves with movement
- Provocative activities: Prolonged sitting, bending, lifting
- Relief: Standing, walking, lying supine
Examination
- Normal neurological exam: No radiculopathy
- Range of motion: Painful flexion, limited by pain
- Straight leg raise: Negative (distinguishes from herniation)
- Provocative tests: Discogenic pain worse with flexion
- Facet loading: Negative (extension, rotation) - rules out facet source
Differential Diagnosis - Exclude Other Sources
Discogenic pain is a diagnosis of exclusion. Must rule out:
- Facet arthropathy: Pain worse with extension, positive facet loading tests
- Sacroiliac joint: Provocative SI tests (FABER, Gaenslen)
- Myofascial pain: Trigger points, muscle spasm
- Spondylolisthesis: Palpable step-off, instability on dynamic X-rays
- Red flags: Infection, tumor, fracture, cauda equina syndrome
Pain Characteristics
Mechanical pain pattern:
- Worse with sitting (intradiscal pressure highest)
- Worse with flexion (increased annular stress)
- Better with standing, walking, lying supine
- No nocturnal pain (unlike tumor)
- No constitutional symptoms (unlike infection)
Axial distribution:
- Centered in low back (L4-5 or L5-S1)
- May refer to buttocks or posterior thighs
- Does NOT radiate below knee (rules out radiculopathy)
- Not dermatomal distribution
Investigations
Imaging Protocol
AP and lateral standing X-rays. Assess disc height loss, alignment, instability. Flexion-extension views if instability suspected. Limited sensitivity for early discogenic pain.
T1 and T2 sequences. Assess disc morphology (Pfirrmann grading), High-Intensity Zone (HIZ), Modic endplate changes. Sensitivity 80-90% when combined with clinical correlation.
Intradiscal contrast injection with pressure monitoring. Concordant pain reproduction at affected level, negative at control levels. Gold standard but controversial due to potential disc injury.
Facet blocks or SI joint injections to exclude alternative pain sources. Over 50% pain relief suggests non-discogenic source.
Imaging Gallery
MRI Findings
| Finding | Description | Clinical Correlation | Sensitivity |
|---|---|---|---|
| Pfirrmann Grading | 5-grade system based on T2 signal and disc height | Grade 4-5 = advanced degeneration, Grade 3 = intermediate | High sensitivity (90%) but low specificity (many asymptomatic have degeneration) |
| High-Intensity Zone (HIZ) | Hyperintense focal area in posterior annulus on T2 | Annular tear - 80% correlation with discogenic pain | 80% sensitivity, 80% specificity for concordant discography |
| Modic Type 1 Changes | Hypointense T1, hyperintense T2 in vertebral endplate | Marrow edema, inflammation - correlates with pain | 70% sensitivity for active discogenic pain |
| Disc Height Loss | Reduced disc space height compared to adjacent levels | Advanced degeneration, may indicate instability | Moderate correlation with pain (biomechanical loading) |
Modic Changes Classification
Modic Type 1 (hypointense T1, hyperintense T2) = marrow edema and inflammation - correlates BEST with discogenic pain and is considered "active" inflammatory process.
Modic Type 2 (hyperintense T1, iso-hyperintense T2) = fatty replacement - chronic change, less painful.
Modic Type 3 (hypointense T1 and T2) = sclerosis - end-stage, stable.
Type 1 can progress to Type 2 with treatment or over time as inflammation resolves.
Discography - Controversial Gold Standard
Indications (highly selective):
- Failed 6+ months conservative care
- Single-level MRI abnormality with clinical correlation
- Considering fusion or disc replacement
- Multi-level degeneration - need to identify pain generator
Technique:
- Intradiscal contrast injection under fluoroscopy
- Measure opening pressure and pain reproduction
- Concordant pain = reproduces exact clinical pain at low pressure (under 15 psi above opening)
- Control levels should be negative
Controversy:
- Risk of iatrogenic disc injury (accelerated degeneration)
- High false-positive rate (20-40% in asymptomatic volunteers)
- Poor inter-rater reliability
- Many surgeons no longer perform due to concerns
Management Algorithm
Conservative Management - First Line (Minimum 6 Months)
Conservative care is the mainstay - 80% of patients improve without surgery. Structured multimodal approach over minimum 6-12 months before considering intervention.
Conservative Treatment Pathway
Goals: Pain control, activity modification, patient education.
- NSAIDs + acetaminophen for analgesia
- Relative rest (avoid bed rest - maintain activity as tolerated)
- Patient education on natural history and prognosis
- Postural advice (avoid prolonged sitting)
Structured physical therapy program:
- Core strengthening and spinal stabilization exercises
- Flexion-based program (Williams) vs extension-based (McKenzie) - individualized
- Aerobic conditioning
- Functional restoration
If inadequate response:
- Epidural steroid injections (limited role - no direct disc effect)
- Cognitive behavioral therapy for pain coping
- Weight loss if obese (reduces biomechanical load)
- Smoking cessation (smoking impairs disc nutrition)
Assess response to conservative care. If persistent severe disability despite compliance with 6 months structured program, consider surgical evaluation. Reassess diagnosis - may not be discogenic source.
Red Flags for Conservative Failure
Consider surgical evaluation if:
- Severe disabling pain (VAS over 7/10) despite 6+ months conservative care
- Documented compliance with structured PT program
- Single-level MRI abnormality with concordant clinical findings
- Significant functional impairment (unable to work, ADLs compromised)
- Patient psychologically appropriate (realistic expectations, no catastrophizing)
Interventional and Surgical Management
Surgical Patient Selection
Surgery is reserved for highly selected patients with failed conservative care and confirmed discogenic source.
Ideal Surgical Candidate
- Single-level disc degeneration (L4-5 or L5-S1)
- Failed 6+ months structured conservative care
- Concordant MRI findings (HIZ, Modic 1, Pfirrmann 4-5)
- Positive discography (if performed) - concordant pain
- Normal neurological exam - no radiculopathy
- Age under 60 (for disc replacement consideration)
- Psychologically appropriate - realistic expectations
- No litigation or workers' compensation
Contraindications
- Multi-level disease (poor outcomes)
- Facet arthropathy or spondylolisthesis (needs fusion)
- Psychosocial factors (depression, catastrophizing)
- Smoking (fusion non-union risk)
- Obesity (worse outcomes)
- Active litigation (poor prognostic factor)
- Inadequate conservative trial (under 6 months)
- Unclear pain generator (multi-source pain)
Surgical outcomes for discogenic pain are less predictable than decompression for stenosis or herniation. Patient selection is critical.
Complications
| Complication | Incidence | Risk Factors | Management |
|---|---|---|---|
| Pseudarthrosis (Fusion) | 5-15% (higher in smokers) | Smoking, obesity, multi-level, diabetes, NSAID use | Revision fusion with bone grafting, biologics (BMP), address risk factors |
| Adjacent Segment Disease | 15-30% at 10 years | Pre-existing degeneration, biomechanical stress, age | Conservative care first, revision fusion if symptomatic with failed conservative care |
| Vascular Injury (ALIF) | 1-5% | Anterior approach, vessel mobilization | Immediate vascular repair, access surgeon on standby, hemodynamic resuscitation |
| Retrograde Ejaculation (ALIF) | 1-5% males | Superior hypogastric plexus injury during L5-S1 approach | Irreversible - counsel preoperatively, consider sperm banking |
| Nerve Root Injury | 1-3% | Neural retraction, instrumentation malposition | Decompress if hematoma, remove hardware if malpositioned, observation if neuropraxia |
| Dural Tear | 3-10% | Posterior approaches, revision surgery | Primary repair, fibrin glue, bed rest, consider lumbar drain if persistent CSF leak |
| Implant Subsidence (ADR) | 5-10% | Osteoporosis, oversizing, endplate injury | Observation if asymptomatic, revision to fusion if symptomatic with height loss |
| Infection | 1-3% (higher with fusion) | Obesity, diabetes, prolonged surgery, revision | Antibiotics, washout and debridement if deep, hardware retention if stable fusion |
Adjacent Segment Disease
Adjacent segment disease (ASD) develops in 15-30% of patients at 10 years post-fusion. Risk factors include pre-existing degeneration (MRI changes at index surgery), biomechanical stress transfer, and older age. Disc replacement theoretically reduces ASD by preserving motion, but long-term clinical benefit unclear. Many cases of ASD are asymptomatic radiographic degeneration - only 5-10% require revision surgery.
Outcomes and Prognosis
Fusion Outcomes
Success rates: 60-70% good to excellent outcomes at 2-5 years in well-selected patients. Results are less predictable than decompression surgery for stenosis or herniation.
Predictors of poor outcome:
- Multi-level disease
- Psychosocial factors (depression, catastrophizing, litigation)
- Smoking (doubles pseudarthrosis risk)
- Obesity
- Workers' compensation or litigation status
- Inadequate conservative trial (under 6 months)
- Unclear pain generator (multiple sources)
Disc Replacement Outcomes
Success rates: 70-80% good to excellent outcomes at 5 years, similar to fusion. Lower adjacent segment disease radiographically (15% vs 30%), but unclear if clinically significant.
Failures: Facet arthropathy develops in 10-15% (contraindication to ADR). Implant loosening or wear over long-term (over 10 years) unknown.
Natural History Without Surgery
80% of patients improve with conservative care over 6-12 months. Disc may "burn out" with progressive collapse and fibrosis. Younger patients with Modic Type 1 changes have worse natural history.
Evidence Base and Key Trials
SPORT Trial - Surgical vs Conservative for Degenerative Disc Disease
- Multi-center observational cohort - 304 patients with degenerative disc disease
- Surgery (fusion) vs intensive non-operative care comparison
- At 2 years: surgery group showed greater improvement in pain and function
- At 4 years: outcomes converged - similar functional outcomes between groups
- High crossover rate (40% in conservative group crossed to surgery)
Swedish Lumbar Spine Study - Fusion vs Conservative Care
- Multi-center RCT - 294 patients with chronic low back pain
- Fusion vs continued conservative care
- At 2 years: fusion group had 33% reduction in Oswestry Disability Index vs control
- 63% of fusion patients reported success vs 29% conservative group
- Complication rate 17% in surgical group
Total Disc Replacement vs Fusion - FDA IDE Study
- RCT - 375 patients, Charite disc replacement vs anterior fusion (BAK cage)
- Primary outcome: non-inferiority of disc replacement to fusion
- At 5 years: disc replacement non-inferior to fusion for clinical success
- Adjacent segment degeneration: 28% fusion vs 16% disc replacement (radiographic)
- Reoperation rate similar: 10% fusion vs 8% disc replacement
Modic Changes and Discogenic Pain - Correlation Study
- Cross-sectional study - 412 patients with low back pain
- MRI assessment of Modic changes correlated with pain
- Modic Type 1 changes: OR 4.5 for low back pain
- Modic Type 2 changes: OR 2.3 for low back pain
- High-Intensity Zone (HIZ): OR 3.2 for discogenic pain
Discography False-Positive Rate in Asymptomatic Volunteers
- Provocative discography in 26 asymptomatic volunteers
- 10% had positive discogram (concordant pain reproduction) at low pressure
- False-positive rate increased to 40% in volunteers with chronic pain elsewhere
- Poor specificity raises concerns about discography as diagnostic gold standard
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Diagnosis and Work-up
"A 35-year-old office worker presents with 18 months of mechanical low back pain. Pain is worse with sitting and bending, better with standing. No leg pain. Failed physiotherapy and NSAIDs. MRI shows Pfirrmann Grade 4 degeneration at L5-S1 with High-Intensity Zone (HIZ) and Modic Type 1 changes. What is your diagnosis and management?"
Scenario 2: Surgical Decision-Making
"The patient from Scenario 1 has now completed 8 months of structured conservative care including PT, weight loss, and medications, but continues to have severe disabling pain (VAS 8/10). Discography performed shows concordant pain at L5-S1 at low pressure, negative at L4-5. Facet joints appear intact on MRI and CT. The patient is 35 years old, non-smoker, psychologically appropriate. Discuss your surgical options and decision-making."
Scenario 3: Complication Management
"You performed an ALIF fusion at L5-S1 for discogenic pain in a 45-year-old male. At 12 months post-op, the patient has persistent pain similar to preoperative levels. CT scan shows lucency around the interbody cage with no bridging bone. What is your assessment and management?"
MCQ Practice Points
Pathophysiology Question
Q: Which Modic change type on MRI correlates BEST with active discogenic pain? A: Modic Type 1 (hypointense T1, hyperintense T2) represents marrow edema and inflammation, correlating most strongly with active discogenic pain. Type 2 (fatty replacement) is chronic and less painful. Type 3 (sclerosis) is end-stage.
Imaging Question
Q: What is the High-Intensity Zone (HIZ) on MRI and what is its clinical significance? A: HIZ is a hyperintense focal area in the posterior annulus on T2-weighted MRI, representing an annular tear. It has 80% sensitivity and 80% specificity for concordant pain on discography. Correlates with full-thickness radial annular tears reaching pain-sensitive outer annulus.
Conservative Management Question
Q: What percentage of patients with discogenic back pain improve with conservative care, and what is the minimum trial period before considering surgery? A: 80% of patients improve with structured conservative care over 6-12 months. Minimum 6 months of structured PT, activity modification, and multimodal analgesia should be completed before surgical consideration. Surgery is reserved for failed conservative care with concordant MRI findings.
Surgical Indication Question
Q: What are the ideal patient criteria for lumbar disc replacement vs fusion? A: Disc replacement ideal criteria: age under 60, single-level L4-5 or L5-S1, preserved disc height (over 5mm), intact facet joints (no arthropathy), normal alignment (scoliosis under 11 degrees), no spondylolisthesis, normal bone quality. Fusion preferred if any contraindication present (facet disease, multi-level, instability, older age).
Evidence Question
Q: What did the SPORT trial show regarding fusion vs conservative care for degenerative disc disease? A: SPORT trial (Weinstein 2009) showed surgery (fusion) provided faster pain relief at 2 years compared to intensive conservative care. However, at 4 years, outcomes converged - similar functional outcomes between surgical and conservative groups. High crossover rate (40%). Supports initial conservative trial before surgery, but surgery reasonable option for persistent symptoms.
Complication Question
Q: What is the incidence of adjacent segment disease after lumbar fusion and what are the risk factors? A: Adjacent segment disease (ASD) develops in 15-30% of patients at 10 years post-fusion (radiographic). Only 5-10% require revision surgery. Risk factors include pre-existing degeneration on MRI at index surgery, biomechanical stress transfer from fused segment, and older age. Disc replacement theoretically reduces ASD by preserving motion (16% vs 28% in studies), but clinical significance unclear.
Australian Context and Medicolegal Considerations
Australian Practice Patterns
- Public System Coverage: Lumbar fusion (1-2 levels) and disc replacement procedures covered
- PBS: Limited coverage for biologics (BMP) - special authority required
- ACSQHC: Surgical site infection benchmarking (target under 3%)
- Guideline: NHMRC recommends minimum 6-month conservative trial before fusion
Medicolegal Considerations
- Consent: Must counsel vascular injury (1-5%), retrograde ejaculation (1-5% males ALIF), nerve injury, pseudarthrosis (5-15%), adjacent segment disease
- Documentation: Record failed conservative care duration and modalities (physiotherapy, injections, medications)
- Expectations: Document discussion of realistic outcomes (60-70% success, less predictable than decompression)
- Litigation: Workers compensation and litigation are poor prognostic factors - document discussion
Medicolegal Risk Factors
Discogenic back pain surgery has high medicolegal risk due to less predictable outcomes compared to decompression surgery. Critical documentation includes:
- Informed consent: realistic expectations, 60-70% success rate, risk of persistent pain
- Conservative trial: minimum 6 months documented structured PT, medications, injections
- Patient selection: psychological screening, exclude catastrophizing, litigation, workers comp
- Surgical planning: concordant MRI findings, consider discography if multi-level degeneration
- Approach-specific risks: ALIF retrograde ejaculation (1-5% males), vascular injury (1-5%)
Consent Discussion Points
Specific for ALIF approach:
- Vascular injury (1-5%): major vessels at risk, access surgeon required, potential life-threatening hemorrhage
- Retrograde ejaculation (1-5% in males): permanent, consider sperm banking in young men desiring fertility
- Sympathetic nerve injury: chronic pain syndromes, rare
- Visceral injury: bowel, ureter (rare with proper technique)
General fusion/disc replacement:
- Pseudarthrosis (5-15%): higher in smokers (double risk), may require revision
- Adjacent segment disease (15-30% radiographic at 10 years): 5-10% need revision surgery
- Nerve injury (1-3%): transient neuropraxia common, permanent injury rare
- Infection (1-3%): deep infection may require washout, hardware removal if non-union
- Persistent pain (30-40%): realistic expectation - not guaranteed cure
- Outcomes less predictable than decompression surgery for stenosis or herniation
DISCOGENIC BACK PAIN
High-Yield Exam Summary
Key Pathophysiology
- •Internal disc disruption (IDD) = nucleus dehydration + annular tears WITHOUT frank herniation
- •Inflammatory cytokines (IL-6, TNF-alpha) in annular tears sensitize nociceptors
- •Nerve ingrowth into normally aneural inner annulus (NGF-mediated)
- •Modic Type 1 (marrow edema) = most painful, Type 2 (fatty replacement) = chronic, Type 3 (sclerosis) = end-stage
MRI Classification
- •Pfirrmann Grade 1-2 = normal to early degeneration (bright T2 signal)
- •Pfirrmann Grade 3 = intermediate degeneration (grey T2 signal)
- •Pfirrmann Grade 4-5 = advanced degeneration (dark T2 signal, collapsed)
- •HIZ (High-Intensity Zone) = annular tear, 80% sensitivity/specificity for discogenic pain
- •Modic Type 1 = hypointense T1, hyperintense T2 = inflammation = most painful
Diagnosis
- •Diagnosis of EXCLUSION - rule out facet, SI joint, myofascial sources
- •Mechanical axial pain worse with sitting/flexion, better with standing/walking
- •Normal neurological exam - NO radiculopathy (distinguishes from herniation)
- •Provocative discography = concordant pain reproduction (controversial - 20-40% false positive)
Treatment Algorithm
- •Conservative FIRST - minimum 6 months structured PT, core strengthening, multimodal analgesia
- •80% improve with conservative care - surgery is last resort
- •Surgery if: failed 6+ months conservative, concordant MRI findings, single-level, no psychosocial red flags
- •Fusion vs disc replacement: ADR if age under 60, preserved height, intact facets, single-level
Surgical Pearls
- •ALIF preferred for L5-S1 (large footprint, lordosis restoration, direct access)
- •TLIF for L4-5 or if need decompression (unilateral approach, single position)
- •Disc replacement: requires REPLACE criteria (Range, Early, Posterior facets, Level, Age, Coronal, Endplates)
- •Supplement with posterior pedicle screws for stability (fusion rate over 95% vs 70-80% stand-alone)
Complications
- •Pseudarthrosis 5-15% (doubles in smokers) - revise with posterior fusion + bone graft + BMP
- •Adjacent segment disease 15-30% radiographic at 10 years (5-10% need revision surgery)
- •ALIF specific: vascular injury 1-5%, retrograde ejaculation 1-5% (counsel males, sperm banking)
- •Outcomes: 60-70% success with fusion, less predictable than decompression surgery