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British Medical Books Health Issues Computerized Tomography

Lumbar Disc Disease

  • most frequent claim for disability in USA (1990) involved back disorders
    • approximately 19%
    • enormous financial costs
    • loss of productivity
  • Nachemson (1993) - cost of LBP was 5% of Sweden’s GNP
    • clear correlation between welfare benefits & stay away from work

Natural history of lumbar disc disease

  • natural history of the disc sy. is towards resolution
    • Holmes & Rothman - 90% resolve spontaneously within 3 months
    • Singer - similar findings
    • Weber (Spine 1983) - results of disc dx treated operatively at 1 year was far better than those treated non-operatively BUT, at 4 & 10 year follow-up, the results were the same
  • neurological results improved just as well in the conservatively treated group as the operative group
  • natural course of herniated discs - decrease in size (serial CT scans) - Thelander & others

Theory of spinal degeneration

  • all spines degenerate
  • present methods of treatment are for symptomatic relief, not for a cure
  • degenerative process divided into three separate stages

1st stage - dysfunction

    • age group - 15-45 years
    • tears in the disc anulus & localized synovitis of the facet joints
    • familial predisposition to lumbar disc herniation in patients who had herniation before age 21 years

2nd stage - instability

    • 35-70-year-old patients
    • internal disruption of the disc progressive disc resorption, degeneration of the facet joints with capsular laxity, subluxation & joint erosion

Final stage - stabilization

    • patients older than 60 years
    • development of hypertrophic bone about the disc and facet joints
    • leads to segmental stiffening or frank ankylosis
  • each spinal segment degenerates at a different rate
    • one level is in dysfunction, another may be entering stabilization stage
  • disc herniation a complication of disc degeneration in dysfunction & instability stages
  • spinal stenosis from degenerative arthritis is a complication of bony overgrowth compromising neural tissue in the late instability & early stabilization stages
  • males were found to have more degeneration than females
  • L4-5 & L3-4 disc levels showed the greatest degree of disc degeneration

Pain transmitting structures

  • at the level of the intervertebral foramen is the dorsal root ganglion
  • distal to the ganglion three distinct branches arise from the dorsal root

ventral ramus

    • supplies all structures ventral to the neural canal

sinu-vertebral nerve

    • originates from the ventral ramus
    • innervating posterior aspect of disc, vertebral bodies & posterior longitudinal ligament

dorsal ramus

    • three branches
    • innervate the structures dorsal to the neural canal
      • posterior musculature and skin
      • facet joint

Results of surgery

  • failure rate of surgery for pain relief d/t disc herniation is high (reported by several authors)
  • significant morbidity also present post-op.

Why surgery often fails

    • main cause of surgical failure = poor patient selection
    • inaccurate diagnosis
    • back pain & sciatica can originate from a number of sites
  • X rays, CT scans & MRI’s are only of relevance if the findings are supported by clinical findings
  • to operate on the basis of special investigations only is unacceptable
  • must also remember:
    • diabetes can mimic a herniated disc
    • ischaemia of the cauda equina & nerve roots are a cause of intermittent claudication
    • psychogenic factors

Special Investigations

  1. CT & MRI
    • low specificity: 30% of the N population have positive scans which are of no importance
  2. EMG
    • has a very high accuracy: helpful test when surgery is considered
  3. Fibrinolytic activity test
    • a low fibrinolytic response favours a bad surgical result
    • the plasminogen activator inhibitor 1 test is sufficient to assess this
  4. Discogram
    • valuable pre-operative examination

Treatment modalities

  1. Manipulation
    • if it has a role
  2. Traction
    • no proof that it has a beneficial role
  3. Chemonucleolysis
    • unpopular because of severe complications:
      • transverse myelitis
      • allergic reactions
      • persisting attacks of muscle spasm
  4. Facet joint infiltration
    • useful, may exclude a facet joint arthropathy as a cause of pain
  5. Epidural injections (cortisone)
    • recommended
  6. Spinal corsets
    • have a place in the treatment of low backache

Acute herniated lumbar disc

  • in lumbar disc disease need to consider:
    • no surgery for psychosocial problems
    • exclude other causes of LBP or sciatica
    • accurate clinical diagnosis
    • unequivocal definition of the lesion on imaging

Clinical

  • 3rd & 4th decade
  • may be related to trauma
  • relief by flexion
  • aggravation by coughing or straining
  • SLR +ve
  • paraesthesia limited to dermatomes

L4 nerve root compression - L3-L4 disc prolapse

  • least common
  • pain in lateral thigh, anterior knee, medial leg
  • +ve femoral N stretch test
  • weak quadriceps, hip adductors
  • sensation << over inner side of the leg, anterior knee
  • absent knee jerk

L5 nerve root - L4-L5 disc prolapse

  • common
  • pain at posterolateral thigh, lateral calf & dorsal foot
  • weakness of dorsiflexion of foot (can’t heel walk)
    • EHL
    • EDL & B
    • Gluteus medius
  • sensory deficit - anterolateral leg, dorsum of foot, great toe
  • no reflex deficit

S1 nerve root compression - L5-S1 disc prolapse

  • most common
  • leg pain > back pain
    • sciatica - mid-gluteal, posterior thigh, calf –> heel
    • >> pain with activity, coughing, sitting, Valsalva
  • paraspinal muscle spasm
  • loss of lordosis
  • +ve SLR
    • pathognomic if well leg SLR produces pain on involved side
  • motor loss
    • peroneus longus & brevis
    • triceps surae –> << plantarflexion (can’t tip-toe)
    • gluteus max.
  • sensation
    • lateral ankle & foot
  • absent ankle jerk

Differential diagnosis of non-mechanical back pain
Extrinsic lesions

  1. referred
    • abdomen, retroperitoneal
    • aneurism, tumour etc.
  2. hip dx.
    • OA
    • infection (TB)
  3. endocrine, metabolic
    • DM
    • Paget’s

Intrinsic lesion - 1° dx. of the spine

  1. infection - bone, disc, epidural space
  2. neoplasm
  3. inflammatory - ankylosing spondylitis
  4. trauma

Treatment Protocol

  • bed rest for 2 to 5 days + NSAID’s (minor analgesics if intolerance to NSAID’s)
  • patient education on the disease & postural guidance
  • as soon as the pain has improved - physiotherapy
    • extension exercises
    • rationale - re-location of the disc
  • if no response to above treatment –> epidural injection of LA + steroids (under image)
    • NB: before epidural must be sure of the diagnosis
    • exclude infection on MRI
    • CI: cauda equina sy., progressive neurology, bleeding disorder
    • after epidural injection - bed rest for 10 to 14 days
    • maximal benefit may only be seen after 2 weeks
  • if this fails - LA + steroid infiltration around the nerve root: CT guided
  • by 4 to 5 weeks after the onset, should be in a position to make a decision about surgery
  • if the patient can tolerate the pain, a 3 month wait before surgery is not detrimental
  • ± 5% of patients with an acute back, with or without neurological symptoms should come to surgery
  • all patients suffering from LBP require a spine education program (back school)
  • treatment should always be conservative to start with

Indications for surgery in acute disc prolapse:

  1. absolute indications
    • massive prolapse with bladder & bowel paralysis (cauda equina sy.)
    • increasing neurological deficit w/ a significant decrease in SLR test
  2. relative indications
    • failure after adequate conservative treatment (at least 6 weeks but < 3 months)
      • after 3 months risk of chronic pathology to the nerve root
    • incapacitating pain, recurrent episodes of sciatica despite adequate conservative Rx.
      • confirming imaging study (myelogram, CT or MRI) - only indicated if surgery planned
      • must have a radiculopathy, with pain below the knee (> back pain) & the SLR test should reproduce the sciatica
      • sensory disturbances & minor motor signs - should not influence surgical decision

Surgical Options

  • open surgery
      1. standard laminectomy or laminotomy & discectomy
      2. microsurgical discectomy
  • closed surgical techniques
      1. percutaneous discectomy
      2. arthroscopic discectomy
  • chemonucleolysis

Principles of surgery in disc prolapse:

  1. free the nerve root from enchroachment
  2. nerve root must remain undamaged
  3. leave as little scar as possible
  4. do not create instability
    • post-operatively limited walking is permitted, sitting is avoided for 6 weeks
  • if surgery indicated - should be done before 4 months
    • << amount of adhesion of disc to nerve root
  • failed back rate of about 15% in USA
    • main cause is poor patient selection
  • percutaneous discectomy/nucleolysis is not successful - Revrel’s study (1993)
  • formal open surgery is better than above - Nachemson 1988
  • no benefit from fusion with simple discectomy - Tullbergs study (1993)

Complications of discectomy

  • 0-10%

Intra operative

  • dural tears, CSF fistula
  • neurological complications, nerve root injury
  • bleeding
  • injury to abdominal vessels, organs

Post-operative

  • DVT, PE
  • infection
  • scarring, arachnoiditis
  • ileus
  • spinal instability, chr. backache

Recurrence of disc herniation

  • usually only presents after a 1 year pain free interval after surgery
  • if the pain relief was 6 months or less, other causes such as scar tissue or arachnoiditis or internal nerve injury could be the cause

Symptoms

  1. multifocal & non mechanical, present at rest
  2. entire extremity is painful, numb, weak
  3. extremity gives way
  4. treatment response
    • no improvement
    • “allergic” to treatment
    • not on treatment
  5. multiple admissions, multiple doctors, multiple investigations

Signs

  1. skin or non anatomic distribution
  2. simulated rotation tests positive
  3. distraction tests positive
  4. whole leg is weak or numb