Lumbar Herniated Discs

Epidemiology

 

Sciatica > 2/52 1.6%

 

M:F = 1:1

 

Most common L4/5 

L5/S1 inherently stable 

 

Risk factors

 

Sedentary lifestyle

Smokers

Frequent driving

Heavy lifting 

 

Anatomy

 

Annulus Fibrosis

- circumferential, multilayered rim

- type 1 collagen fibres at 30o to horizontal

- peripheral nerve endings

- high resistance to torsional and axial loads

 

Nucleus pulposis

- hydrophilic PG + 70% water

- type 2 collagen

- resist axial compression

 

Avascular

- nutrients diffuse from the end plate

 

Wiltse Classification

 

1.  Bulge 

- annulus diffusely extends beyond the plane of the disc space

- annulus intact / nil focal protrusion

 

2.  Protrusion

- focal bulging within margin of annulus

- diameter of base is greater than diameter of tissue displaced beyond disc space

 

Lumbar Disc Protrusion

 

3.  Extrusion

- under PLL

- mass of discal tissue of greater diameter than the aperature through which it has passed

 

Lumbar Disc ExtrusionL5 S1 Extruded Disc

 

4.  Sequestration

- free disc in canal

- fragment with no continuity with tissue in disc of origin

 

Sequestered Disc MRI 3Sequestered Disc MRI 2Sequestered Disc MRI 4Sequestered Disc MRI 1

 

Anatomical Classification

 

1. Central

 

Lumbar Central Disc Herniation MRICentral Lumbar Disc Herniation

 

2. Lateral Recess / Posterolateral

- between dura and foramina

- anterior: disc (annulus) and vertebral body

- posterior: facet joint, lamina, ligamentum flava

- lateral: foramen, L5 pedicle

 

Herniated disc lateral Recess S1 nerve root compressionL45 Posterolateral Disc

 

3. Foraminal

- anterior: body of L5, L5/S1 disc

- posterior: pars, apex of superior facet of S1

 

Foraminal Disc MRIForaminal Disc 2 MRI

 

4. Extra- Foraminal / Far Lateral

 

Pathophysiology Nerve Root

 

Compression

 

Poorly resistant to compression

- dural sheath instead of perineurium

- tethered between dura and foramen

- compression impairs blood flow to nerve

 

Problem

- asymptomatic nerve compressions

- studies suggest that normal nerve roots do not generate pain when compressed

 

Biochemical

 

Chemical factors

- make nerve root more susceptible to effects of compression

 

Anatomy

 

L4/5

- traversing nerve root is L5

- exiting nerve root is L4

 

Posterolateral disc

- compresses traversing nerve i.e. L4/5 disc hits L5 nerve root

- this is most common situation

 

Foraminal disc

- compresses exiting nerve root i.e. L4/5 disc hits L4 nerve root

- require partial medial facetectomy / stand on opposite side of table

 

Far Lateral / Extra-foraminal disc

- compresses nerve root already exited i.e. L4/5 disk hits L4 nerve root

- Wiltse approach or complete facetectomy / follow nerve out

 

Symptoms

 

Typical patient 20-45 year old male

 

Pain

- leg in dermatomal distribution

 

Neurology

- numbness / parasthesia / weakness

 

Cauda Equina Syndrome

- saddle anaesthesia / urinary incontinence / weak EHL

 

Signs

 

Tension signs

 

1.  SLR / Straight leg raise / Lasegue's Sign

- elevate leg from hip with knee straight

- reproduce pain below knee

- L5 / S1 nerve roots

 

Deville et al Spine 2000

- meta-analysis

- SLR very sensitive 90% but lower specificity 26%

- crossed SLR low sensitivity 29% but more specific 88%

 

2.  Femoral nerve stretch test

- patient prone, knee flexed, extend hip

- reproduces pain

- L4 nerve root

 

Neurology

  Pain Sensation Weakness Reflex Test
L2 Lateral thigh Lateral thigh HF    
L3 Medial knee Medial knee Quads    
L4 Anteromedial knee Medial Malleolus T Ant Knee Jerk Femoral Stretch
L5 Dorsum foot First webspace EHL   SLR
S1 Sole / lateral foot Sole / lateral foot FHL Ankle Jerk SLR

DDx L4 nerve root

- CPN / DPN palsy

- test peroneals, tibialis posterior

 

DDx L5 nerve root

- CPN / DPN / Sciatic palsy

- test peroneals / abductors

 

DDx S1 nerve root

- tibial nerve

- test tibialis posterior

 

MRI

 

T2 Sagittal - myelogram

 

Lumbar MRI T1 Herniated DiscHerniated disc lateral Recess S1 nerve root compressionCauda Equina MRI

 

T1 Axial - see nerve root against white fat

 

Lumbar HNP T1 Axial

 

DDx

 

Infection / Tumour / Fracture

 

Management

 

Non-operative Management

 

NHx

 

Recovery  

- 80% improve after 6/52

- 90% improve after 3/12

- 95% improve after 6/12

 

Weakness just as likely to resolve as pain

 

Results Operative v Nonoperative

 

Peul et al BMJ 2008

- RCT of conservative treatment v microdiscectomy

- symptoms 6 - 12 weeks

- earlier symptomatic relief in surgical group

- no difference at one or two years

 

Options

 

Medications

- NSAIDs / opiates / steroids / tricyclic antidepressants

 

Physiotherapy / lumbar stabilisation exercises

 

Traction

 

Chiropractic manipulation

 

Epidural steroids

 

Price Health Technol Assess 2005

- multicentred RCT placebo control

- 220 patients with unilateral sciatica

- minimal and transient value over placebo at 3 weeks

- no difference after 6 weeks

- not cost effective / drain on resources

 

Arden et al Rheumatology 2005

- WEST study

- exactly the same findings

 

Transforaminal CS / Nerve Root Injections

 

Nerve Root Injection

 

Riew et al JBJS Am 2000

- RCT of patients with unilateral nerve root compression

- all considered suitable for operative intervention

- effectively prevented need for surgery in more than half of the patients

- LA + steroid more effective than LA alone

 

Operative Management

 

Absolute Indications

 

Cauda Equina Syndrome

 

Relative Indications

 

Failure of non operative treatment

Severe debilitating anatomical leg pain

Progression neurological deficit

 

Prediction of good operative outcome

 

6/6 Nachemson

 

1. Leg > back pain

2. Symptoms consistent with root irritation

3. Signs consistent with root irritation

4. Tension signs / positive SLR

5. Imaging consistent with Symptoms & Signs

6. Pain > 6 weeks

 

Options

 

Chemonucleolysis

Standard Discectomy

- open

- microdiscecotmy

Percutaneous / Endoscopic Discectomy

 

Chemonucleolysis

 

Mechanism

- chymopapain dissolves nucleosus pulposis

- older technique largely out of favour

 

Results

 

Muralikuttan et al Spine 1992

- RCT of discectomy v chemonucleolysis

- inferior short term results with chemonucleolysis

- no difference at one year

 

Discectomy

 

Advantage

- suitable for noncontained disc

 

Results

 

Dewing et al Spine 2007

- prospective followup of 183 single level lumbar discectomies

- average age 27

- 85% satisfied with surgery

- recurrent disc herniation in 3%

- better outcomes in L4/5 than L5/S1

- better outcomes in sequestered / extruded discs than contained discs

- poorer outcomes in smokers and patients with predominance of back pain

 

Righesso et al Neurosurgery 2007

- RCT of open v microdiscectomy

- no difference in outcome

- longer scar and inpatient stay in open group

- longer surgical times in microdiscectomy

 

Percutaneous Discectomy

 

Indications

- contained disc

 

Technique

- image guidance / endoscopic techniques

- interlaminar or transforaminal

- discectomy with cutting / suction probe

 

Advantage

- minimal scar

- rapid recovery

 

Results

 

Ruetten et al Spine 2008

- RCT of endoscopic interlaminar and transforaminal v microdiscectomy

- 82% relief of leg pain, no difference in each group

- 6% recurrence, no difference in each group

- reduced back pain and complications with improved rehab in endoscopic group

 

Complications Discectomy

 

Wrong level surgery

 

Neural injury

- paraplegia 1: 25 000

- nerve root injury

- cauda equina 0.2%

 

Dural tears

 

A.  Intraoperative Management

- head down

- stop ventilating / hand ventilate / anaesthetic valsalva

- ensure free abdomen

- CSF can make nerve root in danger / protect with patty

- attempt primary repair with 6.0 prolene non cutting needle

- supplement with Tisseel glue

- +/- fat graft / thoracolumbar graft

- subfascial drain

- bed rest 2 days

 

B.  Postoperative CSF leak

- ensure no meningitis symptoms

- glucose / microscopy test to confirm

- adequate fluids / head down / quiet room / bed rest

- antibiotics controversial

- MRI: small leak or large leak

 

Non operative Management

- insert drain below conus

- decreases CSF pressure

- bed rest / leave drain for 5 - 7 days

 

Operative Management

- failure nonoperative / large leak

- thoracolumbar fascia / synthetic graft repair

 

Incomplete decompression / failure to relieve symptoms

 

Infection 2%

 

Thromboembolism 1%

 

Arachnoiditis / Intradural fibrosis

 

Incidence 5%

 

MRI changes

1.  Central root clumping

2.  Empty sac appearance

3.  Soft tissue mass in subarachnoid space

 

HNP recurrence

 

Incidence

- life long 6 - 7%

- second time 50%

- third time 90%

 

Investigation

- gadolinium MRI

- scar enhances but recurrent HNP does not

 

Management

- disc resection +/- fusion