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108 II Trauma
3. Torsional flexion injuries (fracture-dislocations) (Fig. 9–4)
a. Frequently cause complete paraplegia
b. Surgical posterior stabilization and fusion are necessary for early
rehabilitation.
5. Vertical compression injuries (burst fractures)
a. Neurological involvement is common secondary to retropulsed pos-
terior vertebral body fragment.
b. Treatment
(1) Conservative treatment with acute bed rest and TLSO orthosis
may be offered for patients who have no neurological deficits
with minimal deformity.
D. Surgical options for neurological compromised patients
Figure 9–2 (A) A sagittal MRI of a 34-year-old man who sustained a burst fracture to the T12 verte-
bral body. Note the retropulsion of the posterior vertebral body with compression of the anterior the-
cal sac. (B) A postoperative anteroposterior radiograph following an anterior L1 corpectomy and fusion
using a titanium Harms mesh cage and an anterior plate and screw construct.
A
B
Chapter 9 Thoracolumbar Spine Fractures 109
Figure 9–3 (A) A sagittal CT reconstruction of
a fracture–dislocation of the thoracolumbar
spine demonstrating marked vertebral body
displacement and canal narrowing. (B) A sagit-
tal MRI of the thoracolumbar spine of the same
patient demonstrating marked canal narrow-
ing. Note the draping of the spinal cord over
the posterosuperior edge of the caudal tho-
racic vertebrae. (C) A postoperative lateral radi-
ograph of the same patient demonstrating
reduction of the spinal deformity followed by a
fusion and stabilization with segmental pedicle
screw anchors spanning three levels above and
below the level of injury.
A
B
C
110 II Trauma
1. Anterior approach preferred in certain situations
a. Large retropulsed anterior fragment with significant neurological
deficits
b. Intervention delayed 2 weeks
2. Posterior approach preferred if the retropulsed fragment is located
posterolaterally, with minor neurological deficits.
a. Posterior approach is required for fracture-dislocations and in situ-
ations associated with traumatic dural tears.
b. Both anterior and posterior approaches may be needed in three-
column injuries.
(1) Particularly in situations with neurological compromise and
posterior ligamentous injuries
Figure 9-4 (A) A sagittal T2-weighted MRI demonstrating a complete fracture-displacement through
the L5 vertebral body due to a distraction-extension injury mechanism. (B) A lateral postoperative ra-
diograph of the lumbosacral spine following reduction of the fracture-displacement and stabilization
with pedicle screw instrumentation from L4–S1.
A
B
Chapter 9 Thoracolumbar Spine Fractures 111
Suggested Reading
Keynan O, Fisher CG, Vaccaro A, et al. Radiographic measurement parameters in thoracolumbar frac-
tures: a systematic review and consensus statement of the spine trauma study group. Spine 2006;
31:E156–E165
Rampersaud YR, Annand N, Dekutoski MB. Use of minimally invasive surgical techniques in the manage-
ment of thoracolumbar trauma: current concepts. Spine 2006;31:S96–S102
Rechtine GR II. Nonoperative management and treatment of spinal injuries. Spine 2006;31:S22–S27
Vaccaro AR, Baron EM, Sanfilippo J, et al. Reliability of a novel classification system for thoracolumbar
injuries: the Thoracolumbar Injury Severity Score. Spine 2006;31:S62–S69
Vaccaro AR, Lehman RA, Hurlbert RJ, et al. A new classification of thoracolumbar injuries: the impor-
tance of injury morphology, the integrity of the posterior ligamentous complex, and neurologic status.
Spine 2005;30:2325–2333
Weinstein JN, Collalto P, Lehmann TR. Long–term follow–up of nonoperatively treated thoracolumbar
spine fractures. J Orthop Trauma 1984;1(2):152–159
III
Degenerative Spinal
Conditions
10 Biochemical Aspects of Intervertebral Disk Degeneration
11 Degenerative Cervical Spine Disorders: Surgical
and Nonsurgical Treatment
12 Degenerative Thoracic Spine Conditions
13 Lumbar Disk Disease: Pathogenesis and Treatment Options
14 Lumbar Spinal Stenosis
15 Surgical Management of Axial Back Pain
10
Biochemical Aspects of
Intervertebral Disk
Degeneration
I. Intervertebral disk
A. Cells
1. Notochordal cells present embryologically disappear by adult life
2. Chondrocyte-like cells in the nucleus pulposus and annulus fibrosus
most likely originate from chondrocytes in the cartilaginous end plate.
3. No significant cell turnover
4. Apoptosis with aging and disk degeneration
B. Gross structures (from peripheral to central) (Fig. 10–1)
1. Outer fibrous annulus fibrosus
a. Primarily collagen fibrils in oblique layers
b. Limited vascular and nerve supply
c. Sinuvertebral nerve posteriorly
d. Sympathetic fibers anteriorly
2. Inner annulus fibrosus
a. Fibrocartilaginous
3. Transition zone
a. Thin zone of fibrous tissue between inner annulus and the nucleus
pulposus
4. Nucleus pulposus
C. Matrices
1. Collagens
a. Annulus (70%)
(1) Predominantly type I
(2) Type I, II, III, V, VI, IX, XI
b. Nucleus (20%)
(1) Predominantly type II
(2) Type II, VI, IX, and XI
115
116 III Degenerative Spinal Conditions
c. Provide tensile strength
d. Collagen cross-linking by covalent bonds via modification of lysine/
hydroxylysine residues
e. Highest concentration of cross-linking in nucleus
D. Disk degeneration
1. Collagen synthesis and content increase in the nucleus
2. Decreased concentration of cross-linking in the annulus
E. Proteoglycans (PGs)
1. PG aggregates’ constituents
a. Central hyaluronan filament
b. Link proteins attach multiple glycosoaminoglycan molecules
c. Large PGs
(1) Aggrecan
(a) Similar to articular cartilage
(b) Half the size of PGs found in cartilage
(c) Higher keratin sulfate:chondroitin sulfate ratio
(d) Higher molecular weights of keratin sulfate
(e) Increased hyaluron content
(f) Important in water retention
(g) Provides compressive strength
d. Small PGs
(1) Biglycan, decorin, lumican, fibromodulin
(2) Involved in organization of collagen and fibril formation
(3) PG content and synthesis vary depending on age, region, and
degeneration.
(4) PG synthetic activity of adult normal annulus approximately
one third lower than articular cartilage and young nucleus
(5) Synthetic activity greatest in the inner annulus
F. Aging and degeneration (Fig. 10–2)
1. Keratin sulfate:chondroitin sulfate ratio increases
Figure 10–1 Schematic demonstrating the basic anatomic structures of the disk in relationship to
the neural elements.
Chapter 10 Biochemical Aspects of Intervertebral Disk Degeneration 117
Figure 10–2 Varying stages of disk degeneration (I–V) categorized via the Thompson grading
scale. (A) Cadaveric specimens and corresponding (B) magnetic resonance images. Grade I repre-
sents a healthy disk and grade V represents a disk with osteophytic end plate changes, loss of disk
height, and water content.