Thoracolumbar burst fracture

Introduction

• First described by Holdsworth in the 1960s as an axial load fracture due to a disc herniation through the superior endplate, resulting in vertebral body disruption¹
• Redefined by Denis according to his 3-column model
  • Compression of the anterior and middle columns with retropulsion of a posterior vertebral body fragment

Anatomy

• Normal thoracic kyphosis is 20 to 50 degrees; lumbar lordosis is 30-50 degrees
• Thoracolumbar junction is a transitional zone from rigid thoracic to mobile lumbar spine, and thus is more susceptible to injury
• Spinal cord generally transitions to the cauda equina at L1, though some variation is seen
• Posterior osteoligamentous complex is a critical factor in determining stability; consists of supraspinous and intraspinous ligaments, ligamentum flavum, and facet joints

Pathogenesis

• Primary force is an axial load to the vertebral body
  • Supraphysiologic load leads to end plate failure as disc is driven into the body²
  • Not due to an increase in internal vertebral body pressure as was once postulated³
• May or may not involve a flexion bending moment
• Posterior column may fail in tension
• Rotational component leads to a more complex and unstable rotational burst fracture

Natural History

• Patients with stable burst fractures without neurologic injury treated nonoperatively
  • Majority able to return to work; in one study, 74% returned within 6 months⁴
  • On average, Oswestry scores indicate minimal disability long term
  • Rare to no neurologic deterioration in initially intact patients
  • In short term, kyphotic deformity not correlated to pain or disability, but in long-term, may cause altered biomechanics at adjacent segments ^4,5,6
• No consensus on exact amount of kyphosis that may lead to long-term concerns
• Canal compromise can decrease by >50% by remodeling regardless of treatment^2,7,8
  • Neurologic recovery from incomplete spinal cord injury correlates with pattern of areas affected⁹
• Central cord: Functional motor recovery in 75% of cases
• Anterior cord: Functional recovery in only 10% of cases
• Brown-Sequard: Functional recovery in over 90% of cases

Clinical Presentation

• Fall from height and motor vehicle accidents are most common mechanisms²
• May have associated injuries: bilateral calcaneus injuries, noncontiguous spinal fractures
• Neurologic injury patterns
  • Spinal cord injury, complete or incomplete
  • Conus medullaris injury
  • Cauda equina syndrome
  • Radiculopathy
• Patients in neurologic shock may demonstrate bradycardia and hypotension
• Physical examination
  • Tenderness, step-off, or localized ecchymosis over spinal processes
  • Assess neurologic status using standardized American Spinal Injury Association (ASIA) classification scale
  • Sacral sparing with normal rectal tone and perineal pinprick sensation is positive prognostic factor for neurologic recovery
  • Assess bulbocavernosus reflex; if not intact, patient is still in spinal shock

Imaging and Diagnostic Studies

Plain Films¹⁰

• Look for widening of pedicles
• Distraction of spinous processes suggests flexion injury; malalignment suggests rotational component
• Kyphosis evaluated via the Cobb Angle - angle between superior endplate of uninjured cranial vertebra and inferior endplate of inferior vertebra
• Anterior loss of height of 50% or more compared to uninjured level may indicate posterior injury
• Poor sensitivity in differentiating compression and burst fractures
• Supine films may underestimate degree of kyphosis; best seen with weight-bearing x-rays.

CT Scan

• In patients with altered mental status after blunt trauma, CT scan of thoracolumbar spine with reconstruction is superior to plain radiographs in detecting fractures requiring intervention¹¹
• Better evaluation of canal, facets, and columns affected in vertebral body
• Canal encroachment can be evaluated on mid-sagittal or axial cuts
• Widening or asymmetry of facet joints implies distraction or rotational component
• “Naked” facet seen in frank dislocations

MRI

• Should be obtained in patients with neurologic deficits; also recommended for preoperative planning and to determine extent of posterior element injury^2,9
• Fat-suppressed T2 and short tau inversion recovery (STIR) sequences are highly sensitive for evaluating integrity of posterior ligamentous complex¹²
• Spinal cord edema is poor prognostic indicator for neurologic recovery⁹
• Edema in vertebral body in adjacent levels indicates occult compression injury; may necessitate a longer construct¹³

Classification

Four main classification systems

Denis

• Minor injuries - spinous and transverse processes, pars, and facet fractures
• Major injuries based on a 3-column model
• Burst fractures differentiated from compression fracture by involvement of middle column

McAfee

• Evolved out of Denis system to include mechanism of injury
• Subcategorizes injuries based on whether middle column fails in compression or distraction
• Can aid in understanding fracture patterns, but not validated

Magerl/AO: Mechanistic

• Type A - compression injury; sometimes operative
• Type B - distraction injury; often operative
• Type C - rotation injury; nearly always operative
• Comprehensive, but poor inter- and intra-observer reliability

Thoracolumbar Injury Classification and Severity Score (TLICS)

• Developed by Spine Trauma Study Group to better evaluate “unstable” fracture patterns and determine mode of treatment^12,14
• 3 criteria evaluated, each assigned points
  • Mechanism - burst assigned 2 points
  • Neurologic status - intact, root level injury, incomplete SCI, complete SCI
  • Competency of PLC - based on T2-weighted MRI
• Good to excellent inter- and intra-observer reliability

Table 1. Thoracolumbar Injury Classification and Severity Score (TLICS)¹⁴

Scores
<4: Nonsurgical Management
=4: Nonsurgical v. Surgical
>4: Surgical Management*

Treatment

• Treatment should be rendered based on spinal stability
  • Instability
    • White and Panjabi - “Loss of the ability of the spine under physiologic loads to maintain its pattern of displacement so that there is no initial or added neurological deficit, no major deformity, and no incapacitating pain”¹⁵
    • TLICSS developed in attempt to objectively determine stability
    • Definite indications for surgical management^2,7,16
  • Associated dislocation
  • Progressive neurologic injury
  • Incomplete SCI with kyphosis and/or significant canal compromise
  • Failure of nonsurgical management - progressive kyphosis, persistent pain, intolerance of brace/cast
• Relative indications^2,7,16,17
  • Concomitant posterior osteoligamentous injury
  • Other injuries (ie, abdominal) necessitating frequent manipulation
  • Factors (obesity, soft tissue injury) precluding cast/brace treatment
• Non-surgical management recommended for stable burst fractures (no posterior injury)
  • RCT showed significantly lower pain scores and higher functional scores in group treated non-operatively versus operatively⁴
• Non-operative management
  • TLSO in extension or Risser body cast in hyperextension
    • Injuries above T 7 require cervical extension to the TLSO
    • Immobilize for minimum of 10-12 weeks
    • Must obtain upright films in brace to ensure maintenance of sagittal alignment and balance
    • Periodic and regular radiographic follow-up to rule out progressive kyphosis
• Operative management
  • Anterior surgery
    • Able to directly decompress any retropulsed fragments
    • Indicated if only anterior and middle columns involved (ie, burst with neurologic compromise secondary to retropulsed fragments)
    • Anterior column reconstruction and fusion allows for shorter fusion segment
    • Direct anterior decompression may lead to higher likelihood of recovery from incomplete SCI than indirect decompression done posteriorly; however, evidence is scant
  • Posterior surgery^2,7,16,17
    • Current options - posterior laminectomy with fusion, posterolateral decompression and fusion, posterior stabilization without decompression
    • Better construct for a posterior osteoligamentous injury (recreates posterior tension band)
    • Indirect decompression can be performed via distraction instrumentation posteriorly; relies on intact Sharpeys fibers/ annular ligament²
      • Thought to be less effective when canal compromise is >67% due to higher likelihood of annular disruption
      • Must monitor sagittal alignment as can worsen kyphotic deformity
    • Laminectomy for indirect decompression should be combined with instrumentation to avoid instability, malalignment, and kyphosis.
  • Combined anterior/posterior surgery
    • Trend towards better maintenance of kyphosis correction¹⁷
    • May be used in cases with retropulsed fragments with neurologic injury and concomitant posterior osteoligmanetous injury
    • Also indicated in cases of significant anterior collapse and posterior column disruption²
  • Rod long-fuse short - fusing only adjacent levels, temporarily spanning longer with rod
    • Fallen out of favor due to high rates of failure, kyphosis, and accelerated arthrosis²
  • Short segment instrumentation (1 level cranial and caudal) can lead to high rates of implant failure and loss of sagittal alignment¹⁸
    • Generally, the posterior construct should include 2 levels cranial and caudal to fractured level

Complications

• Progression of kyphosis
  • Increased risk correlated with initial loss of anterior height >50%¹⁹
  • 20-35 degrees of initial kyphosis postulated to have higher risk of progression
  • Sagittal Index (SI = local segmental kyphosis – baseline curve) is a measurement of the segmental kyphosis with correction for baseline sagittal contour at the involved segment²⁰
    • Higher risk of kyphosis if SI>15 (not a validated index)
  • Fractures treated via an anterior or combined surgical approach show trend towards improved maintenance of kyphosis correction^7,17
• Complication rates between anterior and posterior surgery are overall similar
  • Anterior surgery carries a greater risk of visceral injury
  • Posterior surgery has a greater risk of infection and hardware prominence
• Failure of instrumentation can occur with short-segment constructs as discussed above
• Late development of syringomyelia

Pearls and Pitfalls

• Burst fracture may be misdiagnosed as compression fracture if there are no frankly retropulsed fragments; one must examine for involvement of the middle column
• Look for non-contiguous spine injuries; 5% of patients have a non-contiguous injury, 50% may go undiagnosed on initial evaluation¹³
• Amount of canal compromise does not correlate with neurologic impairment ⁹
• Regular and diligent clinical and radiographic follow-up essential for non-operative management of burst fractures to ensure maintenance of neurologic integrity and spinal alignment^2,10

Controversy

• Much controversy surrounds the treatment of patients without neurologic injury
  • When to obtain an MRI to look for disruption of posterior elements?
  • Should treatment be based on MRI findings of posterior ligamentous disruption?
• What is the false-positive rate of diagnosing posterior tension band disruption on  MRI?
  • What degree of canal compromise warrants surgical decompression?
  • What approach should be used for surgical decompression and stabalization?

References

1. Holdsworth FW. “Fractures, Dislocations, and Fracture-Dislocations of the Spine.” J Bone Joint Surg Am. February 1963; 45B (1): 6-20.
2. Vaccaro A et al. “Diagnosis and Management of Thoracolumbar Spine Fractures.” J Bone Joint Surg Am. December 2003;85:2456-2470.
3. Roaf R. “A Study of the Mechanics of Spinal Injuries.” J Bone Joint Surg Am. November 1960. 42B(4): 810-823.
4. Wood K et al. “Operative Compared with Nonoperative Treatment of a Thoracolumbar Burst Fracture without Neurological Deficit: A Prospective, Randomized Study” J Bone Joint Surg Am. May 2003; 85:773-781.
5. Alanay A et al. “Course of nonsurgical management of burst fractures with intact posterior ligamentous complex: an MRI study.” Spine (Phila Pa 1976) 2004 Nov 1;29(21):2425-31.
6. Young MH. “Long-Term Consequences of Stable Fractures of the Thoracic and Lumbar Vertebral Bodies.” J Bone Joint Surg Br. May 1973; 55B(2): 295-300.
7. Dai LY et al. “A review of the management of thoracolumbar burst fractures” 2007 Mar; 67(3):221-31.
8. Mumford J et al. “Thoracolumbar Burst Fractures: The Clinical Efficacy and Outcome of Nonoperative Management.” Spine (Phila Pa 1976) 1993 June 15; 18(8):955-970.
9. Spivak J, Vaccaro A, and Cotler J. “Thoracolumbar Spine Trauma: I. Evaluation and Classification” J Am Acad Orthop Surg. November/December 1995;3(6):345-352.
10. Bono C and Rinaldi M. “Thoracolumbar Trauma” Orthopaedic Knowledge Update: Spine. 3rd edition. Rosemont, IL: American Academy of Orthopaedic Surgeons, 2006. 201-202.
11. Smith MW et al. “The reliability of nonreconstructed computerized tomographic scans of the abdomen and pelvis in detecting thoracolumbar spine injuries in blunt trauma patients with altered mental status.” J Bone Joint Surg Am. 2009 Oct;91(10):2342-9.
12. Patel A. and Vaccarro A. “Thoracolumbar Spine Trauma Classification” J Am Acad Orthop Surg. February 2010;18: 63-71.
13. Ponnappan R, Lee J. “Thoracolumbar Trauma” Orthopaedic Knowledge Update 9. Rosemont, IL: American Academy of Orthopaedic Surgeons, 2008. 581-82.
14. Vaccaro AR, Lehman RA Jr, Hurlbert RJ, et al. “A new classification of thoracolumbar injuries: The importance of injury morphology, the integrity of the posterior ligamentous complex, and neurologic status.” Spine (Phila Pa 1976) 2005;30:2325-2333.
15. White AA, Panjabi MM. Clinical Biomechanics of the Spine. 2nd Edition. Philadelphia: JB Lippincott, 1990.
16. Spivak J, Vaccaro A, and Cotler J. “Thoracolumbar Spine Trauma: II. Principles of
    Management.” J Am Acad Orthop Surg. November/December 1995. 3(6): 353-360.
17. Oner FC et al. “Therapeutic Decision Making in Thoracolumbar Spine Trauma.” Spine. 2010; 35: S235--S244
18. Tezeren G, Kuru I. Posterior fixation of thoracolumbar burst fracture: short-segment pedicle fixation versus long-segment instrumentation. J Spinal Disord Tech 2005;18:485-8.
19. McAfee PC, Yuan HA, Lasda NA. “The unstable burst fracture.” Spine. 1982;7:365-73.
20. Farcy JP, Weidenbaum M, Glassman SD. Sagittal index in management of thoracolumbar burst fractures. Spine 1990;15: 958-65.