FACET ARTHROPATHY
Degenerative Spine Disease | Source of Axial Back Pain | Contribution to Stenosis
Pathological Grading (Modified Fujiwara)
Critical Must-Knows
- Facet arthropathy is a major contributor to AXIAL MECHANICAL BACK PAIN (not radicular).
- Diagnostic facet joint blocks are the gold standard for diagnosis (80% pain relief threshold).
- Facet hypertrophy contributes to CENTRAL and LATERAL RECESS STENOSIS.
- Conservative management (PT, NSAIDs) is first-line for 6-12 weeks.
- Radiofrequency ablation of medial branch nerves provides 6-12 months relief in 60-70% of patients.
Examiner's Pearls
- "Pain worse with EXTENSION and ROTATION (loads the facets).
- "Tenderness over facet joints (2-3 cm lateral to midline).
- "Single-level facet pain is rare; usually multi-level disease.
- "MRI changes correlate poorly with symptoms - clinical diagnosis is key.
Critical Facet Arthropathy Exam Points
At a Glance
Facet Arthropathy vs Discogenic Pain
| Feature | Facet Arthropathy | Discogenic Pain |
|---|---|---|
| Pain Pattern | Extension/Rotation worse | Flexion worse |
| Location | Paraspinal (2-3cm from midline) | Midline or bilateral buttock |
| Radiation | Rare beyond knee (pseudo-radicular) | Axial or leg pain (if herniation) |
| Imaging | Facet hypertrophy, subchondral sclerosis | Disc desiccation, Modic changes, annular tears |
| Diagnostic Test | Medial branch block (80% relief) | Provocative discography (controversial) |
Mnemonics
FACETFacet Joint Pain Features
Memory Hook:FACET pain has classic postural features that distinguish it from discogenic pain.
BLOCKMedial Branch Block Technique
Memory Hook:BLOCK technique ensures accurate diagnosis before considering radiofrequency ablation.
FUSESurgical Indications for Facet Disease
Memory Hook:FUSE criteria: when conservative and interventional treatments fail, or structural decompression requires fusion.
Overview and Epidemiology
Definition Facet arthropathy (zygapophyseal joint osteoarthritis) is degenerative disease of the posterior synovial joints of the spine, characterized by cartilage loss, subchondral sclerosis, osteophyte formation, and capsular hypertrophy. It is a major contributor to axial mechanical low back pain and spinal stenosis.
Epidemiology
- Prevalence: Present in 40-85% of adults over 60 on imaging (many asymptomatic).
- Contribution to LBP: Facets responsible for 15-40% of chronic low back pain cases.
- Level Distribution: L4/5 (most common) greater than L5/S1 greater than L3/4.
- Progression: Accelerated by obesity, heavy labor, prior spine surgery (adjacent segment disease).
Why L4/5 Predominates
L4/5 is the most mobile lumbar segment and bears the highest biomechanical stress. It is the fulcrum for lumbar lordosis and experiences maximum extension/rotation moments. This explains why L4/5 facet arthropathy and degenerative spondylolisthesis are most common at this level.
Pathophysiology
Degenerative Cascade
Facet arthropathy develops through a well-defined degenerative cascade:
- Initiation: Primary cartilage wear from aging, repetitive loading, or trauma triggers chondrocyte dysfunction.
- Synovial Inflammation: Cartilage breakdown products stimulate synovitis, causing pain and joint effusion.
- Subchondral Changes: Bone sclerosis and subchondral cyst formation develop as cartilage protection is lost.
- Osteophyte Formation: Marginal osteophytes form as a compensatory response to increased stress.
- Capsular Hypertrophy: Joint capsule thickens, contributing to lateral recess stenosis.
- Instability: Advanced degeneration may lead to subluxation and dynamic instability.
Disc-Facet Relationship
The disc and facet joints form a "three-joint complex" at each spinal level:
- Disc degeneration leads to loss of height, increasing facet joint load
- Increased facet load accelerates facet degeneration
- Facet degeneration causes posterior element instability
- Instability further accelerates disc degeneration (vicious cycle)
Stenosis Mechanism
Facet hypertrophy contributes to spinal stenosis through:
- Central Stenosis: Bilateral facet hypertrophy with ligamentum flavum thickening creates "trefoil" canal
- Lateral Recess Stenosis: Superior articular process hypertrophy compresses traversing nerve root
- Foraminal Stenosis: Subluxation and osteophytes narrow the neural foramen
Anatomy and Biomechanics
Facet Joint Anatomy
- Type: Synovial diarthrodial joint with hyaline cartilage.
- Orientation: Sagittal in lumbar spine (resists rotation), coronal in thoracic (allows rotation).
- Innervation: Dual innervation by medial branches of dorsal rami from levels above and below (e.g., L4/5 facet innervated by L3 and L4 medial branches).
- Capsule: Richly innervated with mechanoreceptors and nociceptors.
Biomechanical Function
- Load Sharing: Facets bear 0-16% of axial load in neutral position, increasing to 40% in extension.
- Motion Control: Primary resistors of rotation and excessive translation.
- Stability: Prevent anterior translation of superior vertebra (resist shear).
Decompression and Iatrogenic Instability
Resection of greater than 50% of the facet joint (especially the pars interarticularis) during decompression surgery significantly increases risk of postoperative instability and may require prophylactic fusion. Always assess preoperative facet joint integrity and plan fusion if extensive facetectomy is needed.
Medial Branch Nerve Anatomy
- Courses over SAP-TP junction (superior articular process and transverse process).
- Target for diagnostic blocks and radiofrequency ablation.
- Dual innervation means TWO levels must be blocked/ablated per joint.
- Example: L4/5 facet requires L3 and L4 medial branch blocks.
Degenerative Cascade
- Disc degeneration → Loss of height → Increased facet load.
- Facet arthropathy → Synovial hypertrophy → Instability.
- Instability → Subluxation → Spondylolisthesis.
- Stenosis → Facet hypertrophy + ligamentum flavum thickening.
Classification Systems
Modified Fujiwara Radiographic Grading
The Fujiwara classification grades facet arthropathy based on plain radiographs and CT imaging.
| Grade | Findings | Clinical Correlation | Treatment |
|---|---|---|---|
| Grade 0 | Normal facet joint | Asymptomatic | None |
| Grade 1 | Joint space narrowing, sclerosis | Minimal symptoms | Conservative |
| Grade 2 | Moderate osteophytes, joint erosion | Symptomatic facet pain | Conservative, Blocks, RFA |
| Grade 3 | Severe osteophytes, subchondral cysts, subluxation | Stenosis, instability | Decompression +/- Fusion |
Imaging-Clinical Discordance
MRI and CT findings of facet arthropathy correlate POORLY with symptoms. Many asymptomatic patients have Grade 3 changes. Clinical diagnosis relies on history, exam, and diagnostic blocks, not imaging severity alone.
Clinical Assessment
History
- Pain Pattern: Axial mechanical low back pain, worse with extension/rotation.
- Relieving Factors: Flexion, sitting, rest.
- Aggravating Factors: Prolonged standing, walking, extension activities.
- Pseudo-radicular Pain: Pain may radiate to buttock/thigh (rarely below knee).
- Morning Stiffness: Common (inflammatory component).
- Night Pain: Rare (if present, consider other pathology).
Examination
- Inspection: Loss of lumbar lordosis (protective flexion posture).
- Palpation: Tenderness 2-3cm lateral to midline over facet joints.
- Range of Motion: Pain with extension and ipsilateral rotation.
- Extension-Rotation Test: Standing extension + rotation reproduces pain.
- Neurological Exam: Usually normal (unless concomitant stenosis/radiculopathy).
- Straight Leg Raise: Negative (unless concurrent disc herniation).
Red Flags Requiring Further Investigation
Atypical features suggesting alternative diagnosis:
- Night pain, constitutional symptoms: Infection, malignancy.
- Progressive neurological deficit: Stenosis, cauda equina syndrome.
- Young age (under 40): Inflammatory spondyloarthropathy, infection.
- Trauma history: Fracture, instability.
- No mechanical pattern: Visceral referred pain, systemic disease.
Facet Loading Test
The Extension-Rotation Test is highly specific for facet pain. Have patient stand, extend lumbar spine, then rotate toward painful side. Reproduction of typical pain suggests facet-mediated pain. Sensitivity increases if combined with paraspinal tenderness over facet joints.
Investigations
Diagnostic Imaging Protocol
- AP and Lateral: Assess alignment, disc height, osteophytes.
- Flexion-Extension Lateral: Dynamic instability (greater than 3mm translation or greater than 10 degrees angulation).
- Oblique Views: Visualize facet joint space, pars interarticularis.
- Findings: Joint space narrowing, sclerosis, osteophytes, vacuum phenomenon.
- T2 Sagittal/Axial: Facet joint effusion (high signal), cartilage loss.
- T1: Subchondral sclerosis (low signal), fatty infiltration.
- STIR: Bone marrow edema (active inflammation).
- Key Finding: Facet hypertrophy with ligamentum flavum thickening causing trefoil canal.
- Indications: Metallic artifact on MRI, detailed bony anatomy needed.
- Findings: Excellent visualization of osteophytes, subchondral cysts, joint orientation.
- Grading: Use Fujiwara classification based on CT.
- Indications: Discordant imaging and clinical findings, suspected facet pain.
- Findings: Increased tracer uptake indicates active inflammation.
- Use: Guides diagnostic block selection in multi-level disease.
Diagnostic Gold Standard
Controlled Diagnostic Medial Branch Blocks are the gold standard for confirming facet-mediated pain. 80% pain relief with concordant physical exam provocation is required. Two separate blocks (using short-acting and long-acting anesthetic) reduce false-positive rate from 40% to under 10%.
Management Algorithm
Conservative Management (First-Line for 6-12 Weeks)
Goal: Reduce inflammation, improve function, avoid surgery.
Conservative Treatment Pathway
- Activity Modification: Avoid extension-based activities.
- NSAIDs: Regular dosing for anti-inflammatory effect (2-4 weeks).
- Physical Therapy: Core strengthening, flexion-based exercises, manual therapy.
- Modalities: Heat, ice, TENS (symptomatic relief).
- Continuing PT: Proprioceptive training, functional restoration.
- Weight Loss: If BMI over 30 (reduces facet load).
- Bracing: Lumbar corset for symptom control (not long-term).
- Reassessment: If no improvement, consider interventional options.
Conservative Success Predictors
Favorable prognostic factors for conservative management: Age under 50, symptom duration under 6 months, BMI under 30, absence of stenosis, good compliance with PT. Approximately 40-60% achieve satisfactory relief with conservative treatment alone.
Complications
| Complication | Incidence | Risk Factors | Management |
|---|---|---|---|
| Adjacent Segment Disease | 20-30% at 10 years post-fusion | Long fusion constructs, sagittal imbalance | Extend fusion if symptomatic |
| Postoperative Instability (Decompression Alone) | 10-15% | Over 50% facet resection, preoperative subluxation | Revision fusion |
| RFA Neuritis | 10-20% | High temperature, prolonged lesion time | NSAIDs, neuropathic pain medications, time (usually resolves) |
| Chronic Pain Syndrome | Variable | Duration over 2 years, psychological factors, litigation | Multidisciplinary pain program, psychological support |
| Infection (Post-Injection) | Under 1% | Immunosuppression, diabetes | Antibiotics, drainage if abscess |
Adjacent Segment Degeneration
Adjacent segment disease occurs in 20-30% of fusion patients within 10 years. Risk factors include long fusion constructs, sagittal imbalance, and obesity. Preserve motion segments when possible; minimize fusion length. Counsel patients preoperatively about long-term risks and need for potential revision surgery.
Outcomes and Prognosis
Conservative Management:
- 40-60% achieve satisfactory improvement with PT, NSAIDs, and activity modification.
- Better outcomes in younger patients (under 50), shorter symptom duration (under 6 months).
Radiofrequency Ablation:
- 60-70% report 50% or greater pain reduction at 6-12 months.
- Average duration of relief: 9-12 months.
- Repeat RFA often effective but diminishing returns after third ablation.
Surgical Fusion:
- 70-80% good to excellent outcomes when performed for structural indications (stenosis, instability).
- Poorer outcomes for isolated facet pain without structural pathology (30-50% satisfaction).
Predictors of Poor Surgical Outcome
Poor prognostic factors for fusion: Isolated facet pain without stenosis/instability, duration over 2 years, psychological comorbidities (depression, catastrophizing), active litigation/compensation, smoking, obesity (BMI over 35). Comprehensive preoperative assessment and patient selection are critical.
Evidence Base and Key Trials
Systematic Review: RFA for Facet Joint Pain
- Systematic review of 9 RCTs and 34 observational studies
- 60-70% of patients with positive diagnostic blocks achieve 50% or greater pain relief
- Average duration of relief: 9-12 months
- Cooled RFA may provide longer relief than conventional RFA
RCT: Intra-Articular Steroids vs Medial Branch Blocks
- RCT comparing intra-articular steroid injections vs medial branch blocks
- Medial branch blocks superior to intra-articular injections (60% vs 33% relief at 1 month)
- Relief from intra-articular injections often short-lived (under 4 weeks)
- Medial branch blocks better identify RFA candidates
Cohort Study: Facet Arthropathy and Lumbar Stenosis
- Retrospective cohort of 312 patients with lumbar stenosis
- Severe facet arthropathy (Fujiwara Grade 3) present in 67% of stenosis patients
- Facet hypertrophy accounts for 30-40% of canal narrowing in stenosis
- Combined facet and ligamentum flavum hypertrophy creates trefoil canal configuration
Australian Data: Spine Fusion Rates
- Lumbar fusion rates in Australia: 85 per 100,000 population (2022-23)
- 15% increase in fusion rates over past decade
- Degenerative disease accounts for 60% of fusion indications
- Variation in fusion rates across states suggests practice variation
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Diagnosis and Initial Management
"A 62-year-old male presents with 6 months of low back pain worse with extension and prolonged standing. Pain radiates to right buttock but not below knee. Neurological exam normal. MRI shows Grade 2 facet arthropathy at L4/5 and L5/S1. How would you assess and manage this patient?"
Scenario 2: Interventional Management Decision
"The patient from Scenario 1 returns after 8 weeks of conservative treatment with minimal improvement. He requests 'something more' for pain relief. How would you counsel him regarding interventional options?"
Scenario 3: Surgical Decision in Complex Case
"A 68-year-old female with L4/5 facet arthropathy, Grade 1 degenerative spondylolisthesis, and central stenosis presents with neurogenic claudication (walking 50 meters). Previous RFA provided 8 months of relief but pain recurred. MRI shows trefoil canal with facet hypertrophy contributing to stenosis. How would you manage this patient?"
MCQ Practice Points
Medial Branch Innervation
Q: The L4/5 facet joint receives dual innervation from which medial branch nerves? A: L3 and L4 medial branch nerves. Each facet joint is innervated by medial branches from the levels above and below. This is why diagnostic blocks and RFA must target TWO levels per joint (e.g., L3 and L4 for L4/5 facet).
Diagnostic Block Threshold
Q: What percentage of pain relief is required from a diagnostic medial branch block to confirm facet-mediated pain? A: 80% pain relief with concordant provocation maneuvers. Single blocks have a 30-40% false-positive rate, so two separate blocks (using anesthetics with different durations) are recommended to reduce false positives to under 10%.
Facet Biomechanics
Q: What percentage of axial load do facet joints bear during lumbar extension? A: Up to 40% of axial load during extension. In neutral position, facets bear 0-16% of load. Extension increases facet loading dramatically, which explains why facet arthropathy causes extension-based pain.
RFA Outcomes
Q: What is the average duration of pain relief following successful radiofrequency ablation for facet-mediated pain? A: 6-12 months (average 9-12 months) in 60-70% of patients with positive diagnostic blocks. Relief is temporary; RFA can be repeated when pain recurs, though efficacy may diminish after the third ablation.
Surgical Indication
Q: What is the primary indication for fusion in the setting of facet arthropathy? A: Structural indications: spondylolisthesis, stenosis requiring extensive facetectomy (over 50% of facet), or documented dynamic instability. Fusion for isolated facet pain without structural pathology is controversial and generally NOT recommended based on current evidence.
Adjacent Segment Disease
Q: What is the incidence of adjacent segment disease following lumbar fusion at 10 years? A: 20-30% of patients develop symptomatic adjacent segment disease within 10 years of fusion. Risk factors include long fusion constructs, sagittal imbalance, and patient factors (obesity, smoking). This highlights the importance of preserving motion segments when possible.
Australian Context and Medicolegal Considerations
Australian Healthcare System
- PBS: Subsidy for NSAIDs, neuropathic pain medications.
- Public Wait Times: Variable (6-12 months for elective fusion in some states).
Clinical Practice Guidelines
- ACSQHC National Safety Standards: Preoperative patient assessment, shared decision-making.
- Australian Spine Guidelines: Conservative management first-line (6-12 weeks), interventional options if failed.
- NHMRC Guidelines: Evidence-based patient selection for fusion (structural indications, not pain alone).
Medicolegal Considerations
Key documentation requirements:
- Adequate trial of conservative management (minimum 6-12 weeks) before interventional treatments.
- Informed consent for RFA: Explain temporary relief (6-12 months), need for repeat procedures, 30-40% non-response rate.
- Informed consent for fusion: Adjacent segment disease risk (20-30% at 10 years), realistic outcome expectations, alternative treatments.
- Patient selection for fusion: Document structural indication (stenosis, instability), not isolated pain. Fusion for isolated facet pain is controversial and associated with poor outcomes.
- Shared decision-making: Document discussion of risks, benefits, alternatives, and patient preferences.
Common litigation issues include fusion for isolated pain without structural pathology, inadequate conservative trial before surgery, and failure to counsel about adjacent segment disease.
FACET ARTHROPATHY
High-Yield Exam Summary
Key Anatomy
- •Synovial diarthrodial joint with hyaline cartilage
- •Dual innervation: L4/5 facet = L3 and L4 medial branches
- •Medial branch courses over SAP-TP junction (target for blocks/RFA)
- •Facets resist 0-16% load (neutral), 40% load (extension)
Classification
- •Fujiwara Grade 0 = Normal
- •Grade 1 = Narrowing, sclerosis → Conservative
- •Grade 2 = Osteophytes, erosion → Conservative, Blocks, RFA
- •Grade 3 = Severe changes, cysts, subluxation → Decompression +/- Fusion
Diagnosis
- •Clinical: Extension/rotation pain, paraspinal tenderness, no radiculopathy
- •Imaging: MRI/CT shows facet changes (poor symptom correlation)
- •Gold standard: Medial branch blocks (80% relief threshold)
- •Confirmatory: Two separate blocks (reduces false positives to under 10%)
Treatment Algorithm
- •Conservative 6-12 weeks: PT, NSAIDs, activity modification (40-60% success)
- •Diagnostic blocks: 80% relief confirms facet pain
- •RFA: 6-12mo relief in 60-70% (can repeat, diminishing returns after 3rd)
- •Fusion: ONLY for stenosis, spondylolisthesis, or over 50% facetectomy needed
Surgical Pearls
- •Resection over 50% facet = high instability risk (consider fusion)
- •Fusion for isolated facet pain WITHOUT stenosis/instability = controversial, poor outcomes
- •TLIF/PLIF for stenosis + instability (addresses both pathologies)
- •Counsel about adjacent segment disease (20-30% at 10 years)
Complications
- •RFA neuritis: 10-20% (temporary, resolves with time)
- •Adjacent segment disease: 20-30% at 10 years post-fusion
- •Postoperative instability: 10-15% if over 50% facet removed without fusion
- •Chronic pain syndrome: multifactorial (duration, psychological factors)