Degenerative Disorders(Lumbar Disc Prolapse)

Degenerative Disorders

"Lumbar Disc Prolapse"

 

Definition:

• It is herniation of nucleus puposus of the intervertebral disc through a tear in the annulus fibrosus.

Incidence:

• Age:- mostly middle age.
• Commonest level L4/L5 followed by L5/S1.
• Lumbar disc prolapse:- cervical disc prolapse 4:1.

Aetiology:

1. Trauma:- lifting heavy objects.
2. Degeneration:-causing weakness of annulus fibrosis.
3. Both of the above.

Pathophysiology:

1)Stages of lumbar disc herniation:

• Tearing of the ring of annulus fibrosis.

• Protrusion of the disc against neural structures.

• Extrusion of nucleus pulposis in the neural canal.

 

2)Direction of the cervical disc prolapse:

• Posterolateral>>>root compression>>> sciatica(most common).
• Posterior>>> thecal compression>>> cauda equina(in the cervical region posterior protrusion>>> spinal cord compression i.e. myelopathy.

Clinical Picture:

1)Related to stretching of annulus fibrosis:

a)back pain for several weeks or years before leg pain.
Pain increase with straining, coughing, sitting or standing for a long time and leaning forward.
Improves by bed rest.

b)Spasm of paravertebral muscle limits spinal mobility to reduce pain.

2)Related to neural compression:

a)In posterolateral disc herniation:
1)Sharp lancinating leg pain occurs along one of the dermatomal supply of the lower limbs. It is increased and decrease by the same factors mentioned with back pain.
Pain is called sciatica when it occurs along the distribution of the sciatic nerve.
Pain is called femoralgia if a long the distribution of the femoral nerve.
2)Numbness and parethesia may occur.
3)Motor weakness.
4)Straight leg raising test(Lesegue's sign). w hile the patient in the supine position, raising the leg less than 60 degrees>>> elicits the pain, Dorsiflexion of the foot while the leg is elevated aggravates the pain.

b)In posterior herniation(Cauda equina syndrome):
1)Sensory
a. Saddle anaesthesia.
b. Sciatica and low back pain.
2)Motor:

 weakness e.g. foot drop.
3)Autonomic:
a. Sphincteric disturbance.
b. Sexual dysfunction.

Differential Diagnosis:

1)Osteoarthiritis of the hip joint:

• This can be differentiated by faber test which is Flexion, Abducion, External rotation of the hip.This usually increases pain originating from hip joint.

2)Sacroiliitis:

• There is tenderness on the sacroiliac joint and pain does not extend below the knee.

3)Spondylolithesis:

• Is anterior subluxation of a vertebra on another.Most commonly at L4/L5 and is due to degeneration of the facet joints.
• Back pain is significant. Sciatica, if present, is usually bilateral. X-ray is diagnostic.

4)T.B of the hip joint(rare).

Investigation:

1)MRI:

• Is the modality of choice.
• Demonstrates the prolapsed disc and any canal stenosis.

 

2)X-ray(A-P and Lateral)

• Has a limited value in diagnosis of lumbar disc. It shows a reduced disc height& osteophytes.
• On the contrary it is very useful in

                                                           Spondylolisthesis
                                                            Detects spina bifida
                                                           Detects secondary tumros

3)CT scan is useful but to a less degree than MRI.

 

4)Myelography is invasive and no longer used.

Treatment:

Conservative(succeeds in 90% of cases):

1. Bed rest for 2-4 weeks. Boards are placed under mettress.
2. Analgesics.
3. Muscle relaxants.
4. Weight reduction is advisable.

2)Surgical

Indications of surgery:

1. Failure of conservative treatment.
2. Intolerable pain in spite of initiation of conservative treatment.
3. Progressive motor weakness.
4. Cauda equina syndrome.

Type of surgery:
1)Discectomy: different approaches are used:

• After laminectomy or hemi laminectomy.
• Interlaminar.
• Microscopic.
• Endoscopic.
• Laser.

2)Chemonucleolysis in some cases.

N.B.

• In surgery we remove L4 lamina to gain access to L4/L5 disc which causes compression on L5 root.