Thoraco-lumbar Disc Disease

Disc Herniation

Epidemiology

  • Thoracic:
    • Rare <1%
    • Usually caudal levels (T11-12 most common)
    • Scheuermann’s kyphosis is a risk factor
    • More likely to cause myelopathy
    • Men = Women
  • Lumbar:
    • Common
    • 90% >60 years have MRI disc changes
    • 40% <40 years have MRI changes
    • 5% actually become symptomatic
    • Men 3:1 Women
    • L4/5 most common, then L5/S1
    • Risk factors: Smoking; manual work; genetic

Aetiology

  • With ageing, disc changes are:
    • Increased Keratin Sulphate: Chondroitin Sulphate ratio
    • Decreased water content
    • Decreased proteoglycan concentration
  • MRI features:
    • Hypointense on T1 & T2 – dehydrated
    • Loss of disc height
  • Types of herniation:
    • Protrusion: Disc still contained within annulus
    • Extrusion: Disc outside annulus but not free
    • Sequestration: Free disc fragments in canal

Anatomy of Herniation

  • Thoracic:
    • Tend to be paracentral – rarely far lateral
  • Lumbar:
    • 95% paracentral/posterolateral
      • Through weakest part of PLL
      • Affect traversing root
    • 5% far lateral/foraminal
      • Affect exiting root
    • Axillary herniation:
      • May affect both traversing & exiting root

Diagnosis

  • Sciatica is hallmark – usually to below knee
  • Differentiate from referred pain to thigh/buttock (same mesodermal lineage)
  • May be preceded by low back pain (annular tear)
  • History of bending/lifting but not always
  • Pain worse on flexion

Imaging

  • XR:
    • May show degenerative disease, spondylolisthesis etc.
  • MRI:
    • Gold standard for assessing disc herniation – high false positive rate
    • Findings must correlate to clinical features
    • Contrast (gadolinium MRI):
      • Useful for recurrent disc herniation or post-surgery herniation
      • Scar tissue is vascular – high signal
      • Disc is dehydrated & avascular - hypointense on all sequences

Examination

  • Nerve root irritation tests:
    • SLR, Bowstring, Lhermitte’s
    • Lesague sign: Contralateral SLR is most specific test
  • Rule out cauda equina
  • Screen for red flags to rule out tumour/infection

Management

  • Non-operative:
    • Natural history is good
    • 90% resolve within 3/12 – disc is resorbed
  • Physio:
    • Stay mobile; extension exercises; aerobic exercise; reassurance & support
  • Epidural Steroid Injection:
    • Foraminal root injection
    • Caudal
    • Good sustained relief when they work
    • Enables earlier return to function
    • Only effective in 60% though

Surgery

  • Best results before 6/12 – do not leave indefinitely
  • Indicated for:
    • Failure of non-operative Rx
    • Intractable pain
    • Progressive motor weakness – urgent
    • Cauda Equina – emergency

Technique

  • Thoracic Disc:
    • Posterior surgery relatively contraindicated – high rate neurologic injury
    • Options:
      • Anterior transthoracic approach
      • Anterior via costotransversectomy - easier
  • Lumbar Disc:
    • Open partial laminectomy & discectomy is gold standard
    • Foraminal discs may be easier via an intertransverse approach (Wiltse)
    • Microdiscectomy & endoscopic no proven long-term benefit

Complications – rare but potentially devastating

  • Recurrent or continued symptoms:
    • Most commonly because foraminal root impingement underappreciated
  • Nerve Root injury (<1% in lumbar spine)
  • Epidural Haematoma
  • Epidural abscess
  • Dural Tear
  • CSF leak/fistula
  • Haemorrhage:
    • Anterior perforation through disc into great vessels
    • Pack, close, turn over & stop bleeding via transabdominal approach
    • 50% mortality

Degenerative Disc Disease & Discogenic Back Pain

Epidemiology

  • 80% will have back pain during their lives
  • 30-50 year olds most common for acute back pain

Pain Generators

  1. Disc
  2. Facet joints
  3. Muscular pain
  4. Instability
  5. Spondylolysis & Spondylolisthesis
  6. Nerve root impingement
  7. Stenosis

Disc Generated Pain

  • Normal Ageing Degeneration:
    • Proteoglycan content decreases
    • Water content decreases
    • Keratin Sulphate increases compared to chondroitin sulphate
    • Disc height reduction
  • End plate microfractures
  • Disc Herniation
  • Altered mechanics & spinal loading:
    • Osteophyte formation
    • Facet joint arthrosis
    • Segmental Instability

Modic Changes

  • Represent MRI features seen in the vertebral body & endplates with DDD
Type T1 T2 Relevance
Modic 1 Dark Bright Associated with pain and inflammation; End plate fissuring; Histology – vascular granulation (25%)
Modic 2 Bright Bright Trabecular fissuring; Fatty infiltration of vertebra; Correlates with chronic stable back pain; Most common type (70%)
Modic 3 Dark Dark Rare to see; Sclerotic vertebra and end plates

Lumbar Segmental Instability

  • Caused by degenerative disc disease, facet arthrosis & subluxation
  • Classic symptom: Catch & pain going into extension from a flexed posture
  • Imaging shows >4mm translation on flexion, extension views
  • Can be difficult to correlate with symptoms
  • Treatment: Surgical fusion if thought to be cause of pain

Diagnosis of DDD

  • Rule out red flag lesions
  • Rule out treatable radiculopathy & stenosis
  • XR only if pain persists >6 weeks with no red flags

Waddell’s Non-organic Signs

  1. No pain on distraction
  2. Vague symptoms & history
  3. Simulation pain – e.g., Axial pressure causes low back pain
  4. Pain on light touch
  5. Non-dermatomal pain
  6. Numbness & pain simultaneously
  7. Hysteria

MRI

  • Disc height deterioration
  • Loss of signal in disc
  • Facet hypertrophy
  • Subluxation
  • Modic changes

Management

  • Non-operative is mainstay:
    • Physiotherapy:
      • Aerobic exercise program
      • Core stability training
      • Support & education
      • Multimodal analgesia
    • Chiropractic treatment:
      • Some evidence this works
  • Surgery:
    • Results are unpredictable
    • Rule out other diagnoses first
    • Diagnostic injections pre-surgery are useful
    • Best results are in:
      • None of Waddell’s signs
      • Modic type 1 changes
      • Single level disc disease
      • Other treatments failed

Technique

  • Arthrodesis – gold standard:
    • PLIF, TLIF, Posterior fusion, Anterior fusion
    • Instrumentation improves fusion rate which improves outcome
    • No technique shown to be superior
  • Non-Fusion options:
    • Interspinous distraction devices – more for stenosis
    • Dynamic Stabilisation systems:
      • Not validated in literature for chronic low back pain
    • Total Disk Arthroplasty:
      • Good results for single level disease
      • Not for multilevel disease or instability
      • Long-term results and revision issues not known
Back to top