Thoracolumbar Fractures
I. Introduction
× 70% trauma 30% neoplastic/degenerative
× metastatic neoplasm is usually in vertebral body
× most common mets are Lung, Breast, Prostate, Throid, Renal)
× neurological deficits from direct cord trauma from bone fragment, narrowing of canal by subluxation, vascular compromise by bony/hematoma compression
II. Anatomy
A. Vertebral bony anatomy
1. body
wt bearing
surface area increases from T1 to T12
2. pedicle
protects canal
3. processes
act as levers
muscle attachment
4. articular processes
-direct/restrict motion
-at L5, inf artic process bears wt
-2 inf (in front of lamina), 2 superior (behind pedicle)
-cervical region, they face A-P allowing rotation
-Lumbar region, they face Laterally disallowing rotation
5. vertebral arch
pedicle + laminae
-canal diameter 10mm transverse/ 8mm sag, narrowest T4-9
6. superior and inferior vertebral notches
-only in cervical, lumbar and T1 superiorly
B. Vertebral contours
-Kyphosis in thoracic region
-Lordosis in lumbar region
-cervical lordosis converts to thoracic kyphosis, with apex of convexity at ~T6
and thoracic kyphosis to lumbar lordosis ~ L3
-COG anterior to T6 and Posterior to L3(flexes thorax, extends lumbar)
-more susceptible to flexion-rotation injuries
-int thoracic spine, more stability contributed by ligaments and facet capsule
-lose stabilization of ribs at thoraco-lumbar junction
C. Distinguihing features/Movements
1. transverse process
× progressively decreased spread T1 to T12
× lumbar lagest is L3
×Thoracic TP's: point back, up, laterally: have facet for rib tubercle: stout
× Lumbar : point laterally: long and slender
2. rib articulations
× free floating "Costa" or ribs in thoracic spine provide extra stability
× Cervical and lumbar spines: costa is anterior part of transverse process
× rib facets are at upper postero-lateral portion of inferior body encroaching upon lower postero-lateral angle of sup body and tubercle of Transverse process of inf rib
3. vertebral bodies
× thoracic VB's have ~ equal A-P and Transverse diameters circular foramen
× Cervical and Lumbar VB's have transverse diameters > A-P trianular foramen
4. spinous processes
- spinelike, nearly vertical, especially in mid thoracic
-oblong, perpendicular in lumbar
D. FSU (functional spinal unit)
2 adjacent bodies
disc
facet joints
connecting ligaments
-normal weight bearing 75%disc / 25% facets
-lose 1 facet then 100% disc
-disc bears 30% torsional force
E. Columns Concept
1. anterior
-ant 2/3 body, annulus, and ant long lig
2. middle
-post 1/3 body, annulus, and post long lig
3. posterior
-spinous processes, facet with capsule, lig flav, inter/supraspinous ligs
III. Fractures-Holdsworth classification (mechanistic)
-his proposal of 2 columns argued that post column disruption was sufficients for instability
-this has been shown to be incorrect
A. Axial Loading
-comminuted fx of vert. body
-bone retropulsed into spinal canal
-intact posterior ligamentous complex
B. Flexion
-disruption of post ligaments without bony injury
C. Flexion-Axial loading
1. Type A
-wedge fx<50%
-usually intact post spinous and ligamentous elements
2. Type B
-wedge Fx >50%
-usual post ligamentous damage, may have post bony damage
3. Type C
-Burst fracture - dislocation
-retropulsed bone fragments in canal
-disrupted post ligaments and usually post bone
D. Flexion-rotation
-a rotational-fracture-dislocation with vert body rotating carrying with it a slice of inferior body
-unilateral facet fracture of inferior body
-usually a wedge/burst fracture of the upper vertebral body
E. Hyperextension
-anterior ligamentous disruption
-post displacement of cephalad vertebral body relative to caudad body
F. Flexion-Distraction
-transverse disruption of vertebral body and neural arch through pedicles with intact posterior ligamentous structures
IV. Fractures-Descriptive (Denis)
-fails to include exclusively post ligamentous injury (flexion - Holdsworth)
-important because argues must have PLL and Pst annulus dispurtion along with post column to have instability
A. Compression
-trauma, osteoporosis
-may see in thoracic region if 2° to osteo
Failed anterior column decresed ant. VB Ht
Middle column is fulcrum increased interspinous distance(side of failed EP)
no change post VB Ht
intact post. VB cortex
no subluxation
1.Anterior
most common
T12-L5 > T5-9
2. Lateral
3. Variants
a. superior endplate disruption
b. inferior endplate disruption
c. superior and inferior endplate disruption
d. sup. + inf. with ant. portion of VB fx'ed
B. Burst
-failed VB in axial loading
-failed anterior and middle columns decreased ant. & post. VB Ht
-majority are T12-L5 increased interpediculate distance
tilt/retropulsed bone
fx post. VB cortex
splayed posterior joints
verticle laminar fracture
large central myelographic defect
1. Fx both endplates
-usually lower lumbar
2. Fx of sup endplate
-T-L junction
#1 & #2 b/c of natural tendency of axial loading to cause flexion at T-L junction and extension in lower lumbar vertebra
3. Fx of inf endplate
-rare
4. Burst rotation
-midlumbar
-may confuse with Fx-dislocation
5. Burst lat flexion
-different from lateral compr fx by disruption of post VB wall
•potential for neurological deficit, new or delayed, is high whereas this risk is absent with lat compr fxs.
C. Chance (Seat belt, Flexion-distraction)
-failed posterior and middle columns increased post. VB Ht
-ant column is fulcrum (hinge) increased interspinous distance
-majority are L1-L3 fx post. VB cortex
horiz fx of t'verse process, pedicle, and pars
•CT may miss b/c this is in parallel to CT "cut"
1. Posterior opening through disc space
-interrupts interspinous lig, PLL, disc, and facet capsule
2. Posterior opening through bone
D. Fracture-dislocation
-failure of all columns
-most likely to have neurological deficit normal VB Ht if through disc
-patient may present reduced displaced unilateral facet
-often see multiple rib fractures changed orientation of pedicle/spinous processes
unilateral articular process fxs frequent fxs of facet/pedicle at bases
horiz laminar fxs ALL stripped from inf VB
-majority are T12-L5 anterior wedging possible
1. Flexion-rotation
-failed posterior /middle columns by tension/rotation
-failed anterior columns from compression/rotation
a. through disc
b. through Vertebral Body (Slice)
2. Shear
-3 column failure + ALL
a. Postero-anterior vector
-intact VB
-free floating laminae, fx'd spinous processes, sup facet of inf body
-complete ALL disruption
b. Antero-posterior vector
-no free floating laminae
- +/- spinous process fx
-ant. VB locked on sup. facet of inf body
3. Flexion-distraction
-tension on posterior and middle columns
-torn annulus
-stripped, but not transected, ALL
-absence of sup. articular process fx
V. Stability/instability
Mechanical instability: (first degree): No acute neural threat. (20° flexion of L1 on L2, or lateral bend of 10° withou t vertebral fx)
Neurological instability: (second degree): i.e. burst. increased deformity with axial loading
Mechanical and Neurological(third degree): i.e. Fx-dislocation and severe burst fx with neuro deficit
Unstable
× anything allowing neural injury, progressive deformity
× > 1 column disruption
× burst < 50% wiht post. lig. injury
× >50% unstable
× post column disruption with PLL and Post annulus disruption
× Burst fxs
× Fx-dislocation
-10-15 yrs after fracture, risk premature degenerative spina stenosis, progressive kyphosis
VI. Associated injuries
× transverse process fractures of lumbar
× pars fxs in young people in sports
VII. Imaging
A. Plain Films
-difficult to delineate middle column injuries
-" " " canal compromise
B. CT
-excellent to examine canal compromise by bone
-sagittal reconstructions helpful
-quick
C. Myelography
-determine blocks
-use if suspect dural tear
D. Post metrizimide CT
E. Tomograms
F. MRI