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138 III Degenerative Spinal Conditions
2. Driving certain motor vehicles
3. Multiple pregnancies
4. Cigarette smoking
5. Sedentary lifestyle
6. Obesity
7. Anxiety and depression
II. Pathogenesis
A. Intervertebral disk degeneration (IVD) (Fig. 13–1)
1. Decreased nutrition to the IVD
a. End plate sclerosis
b. Decreased vascularity
(1) O
2
tension decreases
(2) Lactate increases
(3) pH decreases in the center of the nucleus pulposus
2. Decreased water content
a. Normally 88% decreases to 60% by the eighth decade
3. Increased likelihood of annular tears with aging
a. Decreased proteoglycan content of the nucleus pulposus leads to
greater peripheral annular loading and less central nucleus pulpo-
sus resistance.
b. Annular tear may cause low back pain without radiculopathy.
Figure 13–1 Schematic demonstrating the morphological changes associated with degeneration in the
intervertebral disk. Signal intensity (MRI) decreases as degeneration progresses with loss of disk height.
Chapter 13 Lumbar Disk Disease 139
c. Nociceptors are found on the outer anulus and posterior longitudi-
nal ligament.
(1) The posterolateral corner is most susceptible to a fear from
flexion/rotation or torsional stresses.
4. Herniation
a. Types (Table 13–1)
b. Locations
(1) Most common at L4–5 and L5–S1
(a) Less common at high lumbar and thoracic regions
(2) Classically posterolateral with impingement of the nerve below
(i.e., L4–L5 Herniated Nuclear Pulposus (HNP) affects the
traversing L5 nerve root) (Fig. 13–2)
(3) Axillary herniations
(a) Usually due to cephalad and medial migration of the disk
fragment
(b) Medial retraction becomes difficult and dangerous
(Fig. 13–3).
(4) A small central disk herniation may cause back pain without
radiculopathy or cauda equina syndrome.
(5) Extreme lateral or foraminal herniation
(a) Impinges upon the nerve root above
(b) More common in older patients
(c) Typically found at L3 and L4 (Fig. 13–4)
(6) Intradural herniation is extremely rare.
B. Nerve roots
1. Anatomy
a. Each lumbar nerve root exits below the pedicle and above the disk.
(1) For example, the L5 nerve exits below the L5 pedicle and above
the L5–S1 disk.
b. Dorsal root ganglion lies in the intervertebral foramen inferior to
the pedicle, which may be the main source of pain.
c. Each nerve root has three branches.
(1) Ventral ramus for motor function
(2) Sinuvertebral nerve
(a) Innervates the outer layer of the posterior anulus fibrosus
(b) Anterior part of the anulus fibrosus has sympathetic
innervation, and the afferent fibers connect with the
sinuvertebral nerves.
Table 13–1 Morphology of Disk Herniations
Type Findings
Protrusion Broad-based disk bulge
Extrusion Disk herniation through the posterior longitudinal ligament. The fragment
is larger than its base but still in continuity
Sequestered Complete displacement of the disk with no continuity of the fragment
and the intact disk
140 III Degenerative Spinal Conditions
B
Figure 13–2 (A) Schematic demonstrating the anatomic orientation of the exiting and traversing
nerve root in relation to the intervertebral disk. Note that the exiting nerve root can only be
affected by a far lateral disk herniation. (B) Typically, posterolateral disk herniations affect the tra-
versing nerve root. An MRI showing a posterolateral L5-S1 disk herniation impinging on the left S1
nerve root.
A
Chapter 13 Lumbar Disk Disease 141
Figure 13–3 Illustrations and MRI demonstrating various types of lumbar disk herniations. (A,B)
Left paracentral L5–S1 disk herniation. (C,D) Sequestered disk fragment that migrated inferiorly to
the level of the S1 pedicle. (E,F) L5–S1 axillary disk herniation.
Figure 13–4 An axial MRI demonstrating a large far lateral disk herniation at L5–S1 causing
impingement upon the right L5 nerve root.
142 III Degenerative Spinal Conditions
(3) Dorsal ramus branch
(a) Innervates the facets and posterior muscles
C. Biochemical pathology of disk herniation
1. Anulus fibrosus and nucleus pulposus cells produce matrix.
a. Primarily collagen and proteoglycans
b. With aging and disk degeneration, the cells die (apoptosis), and the
matrix content is decreased.
c. Both anabolic and catabolic processes maintain the integrity of the
matrix.
(1) Proinflammatory cytokines regulate the catabolic processes
(a) Tumor necrosis factor-alpha, interleukin-1, phospholipase
A2, prostaglandins
(2) Growth factors that regulate the anabolic processes.
(a) Bone morphogenetic protein (BMP)
2. Diffusion through the end plates or nutritional pathway is also altered
by degenerative changes.
3. Anular tear or herniated nucleus pulposus is initially associated with
significant inflammation.
a. Cytokine leakage through the anular defect may cause radiculopathy.
b. Nucleus pulposus fragments elicit inflammatory and neurotoxic
changes without significant mechanical compression.
(1) Rest, antiinflammatory drugs, or epidural steroids frequently
alleviate the symptoms by decreasing the inflammatory reaction.
4. The herniated nucleus pulposus fragment elicits significant inflamma-
tory reaction and undergoes subsequent resorption.
III. Clinical evaluation
A. History
1. Sciatica or radiculopathy
a. Frequently becomes greater than back pain in large extruded or
sequestered disk herniations
b. Typically resolves with time in most protruded disk herniations
c. Dermatomal distribution
(1) Pain is classically worse with sitting, coughing, sneezing, and
forward flexion.
(2) Usually alleviated by lying and rest
B. Physical examination
1. Observation of patient’s behavior, pain response, spine balance, gait,
muscle spasm, muscle atrophy is important
2. Bony and soft tissue palpation
a. Midline tenderness is frequent at the involved level.
b. Sciatic notch and tenderness along the course of sciatic nerve may
be present in radiculopathy.
c. Paraspinal muscle spasm may be palpable.
3. Range of motion
a. Normal range of motion is extremely variable among individuals
and even changes from morning to evening.
(1) Pain reproduction at extremes of motion is a helpful sign.
Chapter 13 Lumbar Disk Disease 143
(a) Painful lumbar flexion suggests discogenic etiology.
(b) Painful lumbar extension suggests facet disease.
b. Lateral bending causes ipsilateral painful limb in patients with pos-
terolateral or lateral herniated disks.
(1) Lateral bending away from the symptomatic limb may aggra-
vate pain in patients with an axillary herniated disk.
c. Painful dysrhythmic range of motion may indicate mechanical in-
stability particularly when straightening from forward flexion.
4. Neurological examination
a. Motor, sensory, and reflex deficits may be present along a specific
nerve root distribution.
b. Special tests
(1) Straight leg raise
(a) Elevation of a painful limb causes radicular limb pain.
(i) Record the degree of elevation that reproduces pain.
(ii) Dorsiflexion of the foot while raising the leg also
stretches the sciatic nerve and causes pain.
(b) Reproduction of back pain during a straight leg raise should
be noted.
(i) Not considered a positive finding.
(ii) May be found in association with a tear of the anulus
fibrosus tears or central herniated disk
(2) Contralateral leg raise test
(a) Positive if elevation of a nonpainful limb causes back and
limb pain on the opposite side
(i) Usually implies sequestered or large extruded herni-
ated disk
(3) Reverse straight leg raise test
(a) Femoral extension in a prone position stretches the femoral
nerve reproducing pain in the L3 or L4 distribution.
(4) Waddell’s nonorganic findings
(a) Three of five positive findings suggestive of malingering or
other secondary gains
(i) Nonanatomic superficial tenderness
(ii) Simulation tests (axial loading and rotation)
(iii) Flip test
* Extending the leg in a sitting posture is negative.
** Straight leg raise in a supine position is markedly
positive.
(iv) Nonanatomic weakness and sensory findings
(v) Overreaction
5. Differential diagnosis of low back pain
a. Viscerogenic
(1) Abdominal and renal
b. Neoplastic
(1) Primary and metastatic bone tumors
c. Neurogenic
(1) Spinal cord tumors or cysts
144 III Degenerative Spinal Conditions
d. Inflammatory diseases
(1) Ankylosing spondylitis, Reiter’s syndrome, inflammatory bowel
diseases, and psoriatic arthritis (sacroiliitis)
e. Infectious
(1) Discitis, osteomyelitis
f. Spondylogenic
(1) Myofascial syndromes
(a) Iliolumbar syndrome, piriformis syndrome, quadratus lum-
borum syndrome, and fibrositis (trigger point syndrome)
(2) Motion segment disorders
(a) Disk disease, facet syndrome, spinal stenosis
(3) Bony problems
(a) Fractures including osteoporotic compression fractures
(b) Spondylolisthesis
(c) Sacral lesions, coccyx pain
(4) Psychogenic
6. Distinguishing spondylogenic causes of low back pain
a. Discogenic
(1) Herniated nucleus pulposus
(a) Leg pain, tension signs, neurological deficits
b. Anular tears
(1) Back pain and referred pain to the buttock
(2) Midline tenderness, painful forward flexion, back pain in-
creased with straight leg raising test
c. Myofascial syndromes
(1) Tenderness on the affected muscles rather than in the midline
(2) Pain with active contraction and with passive stretch (con-
tralateral bending)
d. Posterior elements
(1) Spondylolysis
(a) Painful extension and rotation toward opposite side
(2) Facet syndrome
(a) Tenderness unilaterally over the joint
(b) Painful hyperextension and bending
(3) Spinal stenosis
(a) Neurogenic claudication
(b) Painful extension of the back
7. Diagnostic studies
a. Plain X-rays
(1) Detect spondylolysis/spondylolisthesis
(2) Disk space narrowing
(3) Scoliosis
(4) Tumors
(5) Infection
b. Magnetic resonance imaging (MRI)
(1) Procedure of choice for herniated disks and for spinal stenosis
(2) Use of gadolinium contrast increases accuracy and detects other
lesions such as tumor, infection, and recurrent herniated disks.
c. Computed tomography (CT) scan or myelo/CT scan
Chapter 13 Lumbar Disk Disease 145
(1) Use if MRI is contraindicated.
(2) CT may be better in patients with degenerative scoliosis or in
patients with metal implants.
d. Discography
(1) Perform to reproduce pain in discogenic syndrome patients
without radiculopathy.
e. Bone scan
(1) Perform if suspicious for tumor or infection.
IV. Conservative treatment
A. Proven methods
1. Patient education (“Back School”)
a. Decreased mechanical stress and expectation
2. Cardiovascular fitness programs
3. Smoking cessation
4. Maintenance of ideal body weight
B. Unproven methods
1. Prolonged bed rest, muscle relaxants, traction, braces, and manipulation
2. Avoid narcotics and tranquilizers except for acute symptoms (1 to 5 days)
3. Epidural steroids have not been proven to be helpful.
a. Use in selected patients with persistent leg pain to help with reha-
bilitation.
V. Operative management
A. Indications
1. Failure of conservative treatment for at least 6 weeks
2. Progressive neurological deficits
3. Presence of neurological findings
a. Radicular pain
b. Positive tension sign or neurological deficits
c. Positive imaging study with clinical correlation
VI. Surgical techniques (Figs. 13–5, 13–6; Table 13–2)
Figure 13–5 Illustration of a typical L5-S1 laminotomy and discectomy. (A)The interlaminar expo-
sure starts with removal of the ligamentum flavum. (B) Additional removal of laminar bone is per-
formed until the lateral portion of the nerve root is visualized. (C) The nerve root is gently retracted
medially, and the herniated disk is removed with the aide of a pituitary rongeur.
146 III Degenerative Spinal Conditions
Figure 13–6 An illustration of a Wiltse paraspinal approach for excision of a for lateral disk hernia-
tion. Intermuscular dissection is between the multifidus and longissimus.
Chapter 13 Lumbar Disk Disease 147
Suggested Reading
Andersson GB. Epidemiological features of chronic low-back pain. Lancet 1999;354:581–585
Batti MC, Videman T. Lumbar disk degeneration: epidemiology and genetics. J Bone Joint Surg Am
2006;88(Suppl 2):3–9
Peng B, Hao J, Hou S, et al. Possible pathogenesis of painful intervertebral disk degeneration. Spine
2006;31:560–566
Saal JS, Saal JA. Management of chronic discogenic low back pain with a thermal intradiscal catheter. A
preliminary report. Spine 2000;25:392–398
Waddell G, McCulloch JA, Kummel E, Venner RM. Nonorganic physical signs in low-back pain. Spine
1980;5:117–125
Waddell G, Sommerville D, Henderson L, et al. Objective clinical evaluation of physical impairment in
chronic low back pain. Spine 1992;17:617–628
Weber H. Lumbar disk herniation: a controlled prospective study with ten years of observation. Spine
1983;8:131–140
Table 13–2 Various Techniques of Disk Treatment
Surgical Technique Findings
Open discectomy • Better visualization of nerve
• More muscle dissection
• Longer hospital stay
• Potential for iatrogenic instability
Microscopic-assisted discectomy • Limited muscle dissection
• Better visualization and lighting
• Increased time and cost
• Difficulty with equipment availability
Percutaneous discectomy • Techniques include chemonucleolysis, percutaneous
discectomy, and laser discotomy
• Inferior results when compared with microscopic-
assisted discectomy
Intradiscal electrothermal therapy • Newer procedure for primary discogenic back pain
• Results demonstrate equivocal results when com-
pared with placebo