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Disc Herniation L5 impingement L4 and L5 nerve impingement
Disc Herniation L5 impingement L4 and L5 nerve impingement probability
Disc Herniation L5 impingement L5 S1 nerve impingement
Disc Herniation L5 impingement L5 nerve impingement (axial MRI view)
Disc Herniation L5 impingement L5 nerve impingement (axial 3D view)
Disc Herniation L5 impingement L5 nerve impingement affected dermatomes
Disc Herniation L5 impingement L5 nerve impingement
Disc Herniation L5 impingement Disc herniation and nerve root impingement

Aetiology

  • The annulus fibrosus along with the nucleus pulposis can resist strain from multiple directions.  The multiple layers of concentrically stacked collagen laminae in the annulus provide tensile strength while the nucleus resists compressive forces.  This unique arrangement permits the spinal column to absorb axial loading forces in a symmetric manner while allowing some degree flexibility.
  • As the nucleus losses hydration it becomes less resistant to compressive forces and as a result these forces are then transmitted in an asymmetrical manner.  This results in annular degeneration leaving the disc susceptible to annular fissuring and tearing.  This can result in herniation of the nucleus.
  • This form of degenerate disc disease can be split up into three different stages:

 

 

Dysfunction

  • Typically occurring between 15-45 years
   
  • Characterised by circumferential or radial tears to the annulus
  • Associated with synovitis of the facet joints

Instability

  • Typically occurring between 35-70 years
  • There is disruption of the disc and re-absorption
  • The facet joints degenerate and this is associated with capsular laxity and subluxation

Stabilisation

  • Progressive development of hypertrophic bone around the discs and facet joints leaded to relative stability of the intervertebral discs

 

 

 

  • The direction of the disc herniation can also be defined.  Localised herniations and disc protrusions are the most common types, with extrusions and sequestered discs being less common (Table 1).

 

Table1:  Types of disc herniation.

 

Disc Herniation

Explanation

 

Localised

 

Less than 50% of disc circumference displaced beyond the confines of the disc space

 

 

Protrusion

 

Herniated disc with broad base

 

 

Extrusion

 

Herniated disc with broad base

 

 

Sequestered

 

Free segment completely detached from parent disc

 

 

Clinical Presentation

  • The most common presenting complaint is one of intermittent lower back or buttock pain for a varying amount of time before the onset of severe leg pain.
  • A sudden exacerbating factor such as hyper-flexion can reinitiate the pain and this is commonly associated with the onset of leg pain.
  • This radicular pain passes below the knee and follows the dermatome of the involved nerve root.  The pain caused by the herniated disc is commonly at least equal in severity and commonly more so to that of the back pain itself.
  • If the leg pain is mild and the back pain is the predominant feature a diagnosis of nerve root impingement from a herniated disc should be questioned.
  • Indeed, if the pain is constant with no relieving factors, the diagnosis of a herniated disc is again unlikely.
  • More specifically, other symptoms of disc herniation include paraesthesia and muscle weakness.  The level and type of muscle weakness, when associated with disc herniation, determines the nerve root involved (Table 2 & Image 1):

 

Table 2:  Nerve Root and Dysfunction caused

 

Nerve Root

Function

Dysfunction

 

 S1

 

Sensory

Motor

Reflex

 

 

Lateral malleolus / Lateral foot / Dorsum of fifth MTP.

Eversion of the foot (Peroneus longus and brevis) / Gastronemius / Hamstrings

Loss of ankle jerk 

 

 

 L5

 

Sensory

Motor

Reflex

 

 

Anterolateral leg / 1stweb space dorsum of foot

Great toe extension (Extensor hallucis longus)

Usually no change

 

 

 L4

 

Sensory

Motor

Reflex

 

Lateral Thigh / Anterior knee / Medial leg

Variable, some weakness in quads, hip adductors, tibialis anterior, dorsiflexion and inversion of the foot (combination L 4&5)

Knee jerk variable.

 

  • Bilateral symptoms of paraesthesia and or muscle weakness may be as a consequence of a massive extrusion of the disc involving the whole canal.
  • If this is the case, the history should enquire about saddle paraesthesia, bladder and bowel dysfunction, as these constitute a diagnosis of cauda equina syndrome, which is an orthopaedic emergency.
  • Unilateral symptoms and or signs may also be associated with compression of the cauda equina and therefore bladder and bowel dysfunction should always be asked about.

 

Clinical Examination Findings

 

Look

 

  • In the acute phase pain will cause marked paraspinal muscle spasm.  This may produce a correctable scoliosis in the lumbar spine.
  • There will be loss of normal lumbar lordosis.
  • As the pain subsides these findings tend to resolve but the loss of normal lordosis may remain.
  • Long standing disuse of the limb may produce obvious muscle wasting.

 

Feel

 

  • Palpation for tenderness is a variable sign in lumbar disc herniation.
  • Tenderness and spasm over the paraspinal muscles may be found in the acute setting.  Patients should be examined prone to ensure the muscles are as relaxed as possible.
  • The patient may have pain localised over the corresponding lumbar spinous processes or interspinous ligaments and if this is a predominant feature, especially in the thoracic or upper lumbar spine, this should be considered an indication for further investigation.

 

Move

 

Straight leg raise (SLR)

  • Pain on SLR testing is a result of increased nerve root tension and lack of the normal excursion of the root at the herniation site.
  • A positive crossed SLR test has a higher specificity than a positive ipsilateral test.

 

Laségue sign

  • Like SLR this test has variable sensitivity.
  • Should cause pain in the ipsilateral buttock and leg distal to the knee.
  • Contralateral leg pain is thought to be a pathognomonic sign of disc herniation (in the same way as the cross over SLR).

 

Femoral nerve stretch

  • For higher lesions  (L2 – L4 nerve root irritation)
  • SLR and Laseuge tests may be negative. 
  • In this case, femoral nerve stretch may reproduce the patients’ symptoms in the anterior thigh.

 

Investigations

 

Plain Radiographs

  • Not generally helpful and not indicated if a diagnosis of nerve root impingement is suspected
  • AP and lateral lumbar spine images should be assessed for:
  • Presence or absence of disk degeneration
  • Osseous or soft-tissue abnormalities
  • Atherosclerosis of the abdominal vasculature

 

Magnetic Resonance Imaging (MRI)

 

Indications:

  • Patients who develop focal or diffuse neurological deficit
  • Patients who present initially with intractable radicular pain and are unable to continue with conservative management
  • Any patient considered for operative treatment
  • Cauda equina syndrome

 

Not indicated:

  • Patients that present with painful lumbar radiculopathy, in the absence of red flag signs.
  • These patients should undertake at least 6 weeks of non-surgical treatment before they are considered for further imaging.

 

Management

  • The list of non-operative treatment modalities is exhaustive with many having no scientific basis.  There are some however that have been associated with improvement in pain and an earlier return to work for the patient.
  • Over 90% of patients symptoms will improve with non-operative means.

 

 

Non-surgical

 

Physiotherapy

  • Gold standard treatment.
  • For patients with symptoms from true nerve root impingement they should be instructed to adopt positions of comfort only in the first 48hours after the onset of symptoms is advocated.
  • They should take non-steroidal anti-inflammatory and rest in the most comfortable position to relieve pressure on the nerve roots.
  • Muscle relaxants should be used selectively and for well-defined limited periods of time.

 

Analgesics

  • NSAID’s
  • Mild narcotics

 

 

Muscle relaxants

  • Not first-line agents.
  • Should only be considered in patients who are experiencing significant spasms.
  • Used for well-defined and limited period, as side effects of dependence can be detrimental.
  • No evidence that they alter the natural history of the disease.

 

 

Surgical

  • With the exception of a cauda equina syndrome and neurological deficit, surgery should not be considered earlier than 6 weeks from onset of symptoms.
  • If symptoms continue despite conservative measures then patients should be investigated further and referred to an orthopaedic surgeon with a specialist interest in spinal surgery for clinical assessment.
  • Before the patient considers surgery they must understand that the operation is not a cure but for relief of symptoms only.
  • Following surgery the patient must continue protective muscle strengthening and avoidance manoeuvre’s.
  • Patient selection is the key to a good outcome to treatment:

 

  • Unilateral leg pain extending below the knee
  • Symptoms present for at least 6 weeks
  • Pain that decreases with rest, anti-inflammatory or facet joint injections
  • Pain should have reoccurred and returned to the previous level.

 

 

 

Indications 

 

Absolute

  • Cauda equina syndrome (emergency)
  • Progressive neurological deficit. 
  • If a motor or sensory deficit is identified then this should be investigated on an urgent basis and referred on.

 

 

Relative indications 

  • Intractable radicular pain
  • Neurological deficit that does not improve with conservative measures
  • Recurrent sciatica following a successful trial of conservative measures
 
 

 

Operations 

 

1.  Open Laminectomy and discectomy 

  • Discectomy is the surgical removal of herniated disc material.  First, a small piece of the lamina bone is excised to give the surgeon a better view of the herniated disc and surrounding structures (Laminectomy). 
  • The segment of disc that has been compressing the nerve root is then removed.

 

2.  Microdiscectomy  

  • This is the same procedure carried out through a smaller incision and with the use of an operating microscope
  • The results are comparitable between open and microdiscectomy.


Summary Points

  1. Common complication of degenerative disc disease.
  2. Associated with clinically apparent nerve root impingement.
  3. Is most common in the third and fourth decades.
  4. Male : female ratio (3:1).
  5. 95% of intervertebral disc herniations occur at the level of L4/5 or L5/S1. 
  6. Only 5% intervertebral disc herniations become symptomatic.
  7. Within 8-12 weeks of symptom onset, about 90% of patients will have symptomatic improvement without surgery.