Degenerative Disorders Of Lumbar Spine

Lower back and leg pain Zongqiang Huang

 Lumbar disc herniation  Lumbar spinal stenosis

Lumbar disc herniation Anatomy Clinical features Radiological exam Differential diagnosis Treatment

Anatomy

 Intervertebral disc 1. Annulus fibrosus 2. Nucleus pulposus 3. End plate

Anulus fibrosus  Anulus fibrosus makes up peripheral portion of disk structure  Composed of fibrocartilage and type I collagen  Fibers of anulus run obliquely between vertebrae and are arranged primarily in concentric layers  Anulus is wider anteriorly than posteriorly

Nucleus pulposus  Nucleus pulposus consists of a network of delicate collagenous fibers in a mucoprotein gel  Nucleus has a high water content,apparently the result of imbibition by the gel;  It functions to resist compressive loads; water content declines with advancing age and is reduced by pressure borne by the disc  Gradual loss of proteoglycan content explains the loss of water w/ aging

Disc pressure / failure  Intradiscal pressure is higher when sitting than when standing; - sitting-leaning forward > sitting > standing > lying on side > supine;  Rotation combined w/ flexion are the worst positions for disc injury;  It is elevated by bending forward, bending to side, lifting, coughing, sneezing, and straining;  Asymmetric & cyclic loading combined w/ lateral bend, compression, and flexion are risk factors for disk herniation;

Sciatic nerve  Anterior branchs of L4,L5,S1-3

Posterolateral disc herniation

 Protrusion is usually posterolateral into vertebral canal, where it may compress the roots of a spinal nerve  Each nerve emerges the upper part of foramen and lies against body of vertebra above  Protruded disc usually compresses next lower nerve as that nerve crosses level of disc in its path to its foramen

Central (posterior) herniation

 In the lower lumbar segments, central herniation may result in S1 radiculopathy  Cauda equina syndrome

Far lateral disc herniation  Compress the nerve root above the level of the herniation (hence a L4-L5 far lateral herniation may result in a L4 radiculopathy)  Occurs in 6-10% of all lumbar disc herniations;  L4 nerve root is most often involved;  Patient typically have intense radicular pain (sciatic 25% and femoral 75% of the time)

Symptoms and signs  Low back pain with radiation of severe pain down the back of the leg to the ankle and foot.  Neurological signs such as motor and sensory loss and occasionally bladder involvement.  Spasm of the spinal muscles with tenderness over the lower lumbar spine on the side of the lesion. The muscular spasm may produce a scoliosis.  There may be a history of previous episodes of back pain and sciatica or of a previous injury.

Protrusion of the L4/5 disc  Protrusion of the L4/5 disc may cause L5 root pressure with pain radiating down the leg to the dorsum of the foot.  Numbness on the outer side of the calf and medial two-thirds of the dorsum of the foot  Weakness of dorsiflexion, particularly of the foot and toes.

Protrusion of the L5/S1  The S1 nerve root is compressed  Pain and numbness on the outer side of the foot and under side of the heel.  Weakness of both eversion and antarflexion of the foot  The ankle jerk is diminished or absent

Protrusion of the L3/4 Protrusion of the L3/4 disc may cause pressure on the L4 nerve root Numbness over the front of the knee and leg The knee jerk is diminished. Weakness of the knee extensors.

Central protrusion  Central protrusion of a lower lumbar disc can press on the cauda equina and lead to urinary retention.  On examination there is usually perianal numbness and a patulous anus.  Emergency decompression is essential to avoid permanent damage to sphincter innervation.

Cauda equina  The spinal cord ends in the lumbar area and continues through the vertebral canal as spinal nerves. Because of its resemblance to a horse's tail, the collection of these nerves at the end of the spinal cord is called the cauda equina. These nerves send and receive messages to and from the lower limbs and pelvic organs.

 Limitation of lateral flexion of the lumbar spine to the same side will be most marked with a protrusion lateral to the nerve root  while limitation of lateral flexion to the opposite side will be most marked with a protrusion medial to the nerve root.

Straight Leg Raise  In a normal person, this can be done to about 75 or 80 degrees of flexion at the hip without sharp pain radiates down to the leg.

 Well leg or cross leg sign: if there is a left sided herniation,raising the right leg may cause pain to shoot down the course of the left sciatic nerve.  Sciatic stretch test: this test is performed after a straight leg raising test by lowering the affecting leg a few degrees below the point .

Radiographs  Traction spurs  Disc space narrowing

CT

MRI  There is a 29% prevalence of disc herniation in asymtomatic individuals

Differential diagnosis  Secondary tumours and multiple myeloma of the lumbar spine which usually cause vertebral destruction with sparing of the discs.  Fractures and infections

Natural History  Prognosis of disc herniation is generally good regardless of treatment;  Patients operated on for proven disc herniations improved more rapidly than patients treated non operatively;  Within 4-5 years both operative and non operative treatment groups will generally have comprable neurologic recovery; hence long term results are similar w/ or w/o surgery;  Of all patients who sustain acute sciatica, less than 25% will require surgery;

Treatment  Nonoperative treatment  Pain relief is best achieved by mobilizing the spine and strengthening the back muscles  Bed rest  Nonsteroidal anti-inflammatory agents  Active physical therapy  Skin traction for sciatic irratation  Epidural steroid injection

Surgery  Opened surgery

 Minimally invasive surgery

Indications for operation  Cauda equina lesions (emergency decompression)  Progressive or unresponsive lesions with appreciable neurological signs despite conservative management.

Lumbar stenosis  Spinal stensosis is a narrowing of the spinal canal or neural foramina producing root ischemia and neurogenic claudication  Although degenerative spondylolisthesis is common cause of stenosis, 10% of adults > 65 yrs may have this finding & many are asymptomatic;

Clinical Findings  Patients are usually 60 years or older;  Unilateral or bilateral leg pain, w/ or without back pain;  Pain occurs when the patient is upright and particularly when walking  Typical symptom is leg pain, numbness, and weakness developing after patient walks a predictable distance; - patient seeks relief by sitting, leaning forward to "relieve pressure

Phalen test  With patient upright, bend the patient into extension for a full minute  This should accentuate the spinal stenosis;  Positive test will produce a crescendo of leg symptoms followed by rapid relief of these symptoms when the patient flexes forward, places his hands on examination table, and places one foot on stool

CT scan:  Evaluate for lateral stenosis & central stenosis  Dural sac w/ AP diameter of < ten millimeters is consistent w/ clinical syndrome of lumbar stenosis;

Surgical Treatment  Decompression  Laminae are minimally trimmed for exposure;  Includes widening of lateral recess;  Removal of medial rim of facets

Adult Degenerative Spondylolisthesis  Often occurs as a result of degenerative disc disease and facet deficiency;  It is often associated w/ intersegmental instability and w/ central stenosis;  Involves L4-L5 level four times more often than the L5/S1 level;  Often causes radiculopathy related to nerve compression within the foramen (ie, L4/L5 spondylithesis will cause a L4 radiculopathy)

Dynamic radiographs  Flexion-Extension X-rays

Non Operative Treatment  NSAIDS  Epidural steroids  Bracing  Change of job type

Surgery  Decompression of the nerve roots  Stabilization by posterolateral fusion