A thoracic Chance fracture is an injury in which the spine is pulled apart during a forceful forward-bending motion. It is a type of flexion-distraction injury, meaning that the back portion of the spinal column is placed under tension and may separate.
Chance fractures most commonly occur near the thoracolumbar junction, where the relatively rigid thoracic spine transitions into the more mobile lumbar spine. They are often associated with high-energy trauma, particularly motor vehicle accidents.
Because these injuries may disrupt several of the structures that normally stabilize the spine, a Chance fracture can be mechanically unstable even when there is little or no spinal cord compression.
What Is a Chance Fracture?
A Chance fracture occurs when the spine bends sharply forward around a fixed point.
Instead of the vertebra simply being compressed, the forces pull the spinal column apart from back to front.
A classic Chance fracture may pass through:
- The spinous process
- The lamina
- The pedicles
- The vertebral body
When the injury passes primarily through bone, it is sometimes called a bony Chance fracture.
In other patients, much of the injury occurs through the ligaments, discs, and joints rather than through bone. These injuries are often referred to more broadly as flexion-distraction injuries.
What Causes a Thoracic Chance Fracture?
Chance fractures are strongly associated with sudden forward bending of the spine during trauma.
Common causes include:
- Motor vehicle accidents
- Lap-belt injuries
- Falls from a height
- High-energy sports injuries
- Crush injuries
- Other major trauma
Historically, Chance fractures were often called seat-belt fractures because they were seen in passengers restrained primarily by a lap belt.
During a sudden deceleration, the pelvis may remain restrained while the upper body moves forward. The spine then bends sharply over the lap belt, producing a distraction injury.
Modern three-point seat belts have reduced the frequency of classic lap-belt injuries, but flexion-distraction fractures still occur.
Where Do Chance Fractures Occur?
Chance fractures most commonly affect the lower thoracic and upper lumbar spine.
The thoracolumbar junction, particularly around T11 through L2, is vulnerable because it represents a transition between:
- The rigid thoracic spine supported by the rib cage
- The more flexible lumbar spine
The abrupt change in spinal mechanics makes this region particularly susceptible to injury during high-energy trauma.
Symptoms of a Thoracic Chance Fracture
Symptoms commonly include:
- Severe back pain
- Tenderness over the injured vertebra
- Pain with movement
- Muscle spasms
- Difficulty sitting upright
- Difficulty standing or walking
There may also be bruising across the abdomen from the seat belt or other restraint.
Neurologic symptoms are less common than with some burst fractures, but they can occur.
Possible neurologic symptoms include:
- Leg weakness
- Numbness or tingling
- Difficulty walking
- Loss of coordination
- Bowel or bladder dysfunction
Any neurologic deficit after significant spinal trauma requires urgent evaluation.
Why Are Chance Fractures Potentially Unstable?
The spine is stabilized by bones, discs, joints, and ligaments.
During a Chance injury, several of these structures may be disrupted simultaneously.
In particular, the injury may damage the posterior ligamentous complex, which plays an important role in resisting excessive forward bending.
The posterior ligamentous complex includes:
- Supraspinous ligament
- Interspinous ligament
- Ligamentum flavum
- Facet joint capsules
When these structures are torn, the vertebrae may no longer maintain normal alignment.
This is why a Chance fracture can be unstable even if the amount of spinal canal narrowing appears relatively small.
Bony Versus Ligamentous Chance Injuries
One of the most important distinctions is whether the injury passes primarily through bone or through ligaments and discs.
Bony Chance Fracture
In a bony Chance fracture, the distraction injury passes through the vertebral body and posterior elements.
Bone has a relatively predictable ability to heal.
If alignment remains acceptable and the posterior ligaments are intact, some bony Chance fractures can be treated without surgery.
Ligamentous Flexion-Distraction Injury
In a ligamentous injury, the forces tear the stabilizing ligaments, facet capsules, or intervertebral disc.
These injuries generally have a greater risk of persistent instability because torn ligaments may not reliably restore normal spinal stability.
For this reason, significant ligamentous Chance-type injuries are more frequently treated surgically.
Associated Abdominal Injuries
Chance fractures are particularly important because they can be associated with abdominal injuries.
The same forces that bend the spine over a seat belt may compress abdominal organs between the belt and the spine.
Associated injuries may include:
- Small bowel injury
- Mesenteric injury
- Pancreatic injury
- Abdominal wall injury
- Vascular injury
A patient with a Chance fracture after a motor vehicle accident therefore often requires careful evaluation for injuries outside the spine.
Abdominal pain, tenderness, bruising, or a visible seat-belt sign may increase concern for associated internal injuries.
How Is a Chance Fracture Diagnosed?
Evaluation typically includes a physical and neurologic examination as well as imaging.
X-rays
X-rays may demonstrate:
- Widening between the spinous processes
- Abnormal spinal alignment
- Vertebral body fracture
- Kyphotic deformity
However, X-rays may underestimate the complexity of the injury.
CT Scan
CT is particularly useful for evaluating the bony components of a Chance fracture.
It can show:
- Fractures through the vertebral body
- Pedicle fractures
- Lamina fractures
- Spinous process fractures
- Facet joint disruption
- Abnormal widening of the posterior elements
- Associated burst components
CT is commonly obtained in patients who have experienced significant trauma.
MRI
MRI is particularly valuable when there is concern for injury to the ligaments, discs, or spinal cord.
MRI can help identify:
- Posterior ligamentous complex injury
- Disc disruption
- Spinal cord compression
- Spinal cord injury
- Epidural hematoma
- Other soft-tissue injuries
MRI may be especially important when the CT findings do not completely explain the suspected degree of instability.
How Is Spinal Stability Determined?
Treatment depends heavily on whether the injury is mechanically stable.
Factors that may suggest instability include:
- Disruption of the posterior ligamentous complex
- Widening between the spinous processes
- Facet joint disruption
- Significant kyphosis
- Translation between vertebrae
- Disc injury
- Multiple-column disruption
- Progressive deformity
Neurologic function is also considered, but a patient can have an unstable Chance fracture and still have a completely normal neurologic examination.
Nonsurgical Treatment
Selected Chance fractures may be treated without surgery.
Nonsurgical treatment is most appropriate when:
- The injury is primarily through bone
- The posterior ligaments remain intact
- Spinal alignment is acceptable
- There is no significant neurologic injury
- The patient can safely mobilize
- Alignment remains stable on follow-up imaging
Treatment may include:
- Pain medication
- Activity modification
- Bracing
- Gradual mobilization
- Follow-up X-rays
A thoracolumbosacral orthosis, or TLSO brace, may be used to help maintain alignment while the fracture heals.
Follow-Up During Nonsurgical Treatment
Patients treated without surgery require close follow-up because some injuries can gradually lose alignment.
Follow-up imaging may be used to look for:
- Increasing kyphosis
- Widening of the injured segment
- Progressive vertebral displacement
- Failure of fracture healing
Progressive deformity may indicate that the injury is less stable than initially thought and may lead to reconsideration of surgical treatment.
When Is Surgery Recommended?
Surgery is more likely to be recommended when there is:
- Posterior ligamentous complex disruption
- Significant spinal instability
- Progressive kyphotic deformity
- Vertebral translation
- Significant disc disruption
- Neurologic injury
- Failure to maintain alignment with bracing
- Severe associated fracture patterns
Ligamentous flexion-distraction injuries often require surgical stabilization because the damaged soft tissues may not heal with sufficient strength to reliably stabilize the spine.
Surgical Stabilization
Surgery usually involves posterior spinal instrumentation.
Pedicle screws are placed into vertebrae above and below the injured level and connected with rods.
This allows the surgeon to:
- Restore spinal alignment
- Close the distracted portion of the spine
- Stabilize the fracture
- Prevent progressive deformity
- Protect the spinal cord
- Allow earlier mobilization
Spinal fusion may also be performed depending on the injury pattern and the surgical strategy.
How Many Levels Need to Be Instrumented?
The number of vertebrae included in the surgical construct depends on:
- Location of the fracture
- Degree of instability
- Associated fractures
- Bone quality
- Degree of deformity
- Integrity of neighboring vertebrae
Some injuries can be treated with short-segment fixation around the injured level.
More severe thoracic injuries may require longer constructs.
The thoracic spine generally tolerates longer fixation better than the lumbar spine because it is naturally less mobile.
Is Spinal Decompression Necessary?
Not every Chance fracture requires spinal decompression.
Many of these injuries primarily cause instability rather than direct spinal cord compression.
Decompression may be necessary when there is:
- Bone within the spinal canal
- Epidural hematoma
- Associated burst fracture
- Spinal cord compression
- Neurologic deterioration
The surgical approach is tailored to the specific source of compression.
Chance Fracture Versus Burst Fracture
Chance fractures and burst fractures result from different injury mechanisms.
A burst fracture primarily results from compression of the vertebral body.
A Chance fracture primarily results from distraction, or pulling apart, of the spinal column.
Burst fractures often:
- Cause vertebral body fragmentation
- Push bone backward into the spinal canal
- Produce anterior and middle column compression
Chance fractures more often:
- Widen the back of the spinal column
- Disrupt ligaments
- Produce horizontal fractures through the vertebra
- Cause instability through flexion-distraction forces
Some high-energy injuries contain features of both patterns.
Chance Fracture Versus Flexion-Distraction Injury
The terms are closely related but are not completely interchangeable.
A Chance fracture traditionally describes a flexion-distraction injury that passes predominantly through bone.
A flexion-distraction injury is the broader category and includes injuries that pass through:
- Bone
- Ligaments
- Intervertebral discs
- Facet joints
- Combinations of these structures
The distinction can be important because predominantly ligamentous injuries are generally less likely to heal reliably without surgical stabilization.
Recovery After a Chance Fracture
Recovery depends on:
- Severity of the injury
- Whether the injury is bony or ligamentous
- Whether surgery is required
- Presence of neurologic injury
- Other injuries sustained during the trauma
- Age and general health
Patients with stable fractures and no neurologic injury may gradually resume normal activity as the fracture heals.
Patients treated surgically are often encouraged to begin walking relatively early, depending on associated injuries.
Physical therapy may help restore:
- Strength
- Endurance
- Balance
- Mobility
- Core control
How Long Does a Chance Fracture Take to Heal?
Bony healing commonly takes approximately 8 to 12 weeks, although complete recovery may take longer.
Patients treated nonsurgically are generally monitored with repeat imaging during this period.
Recovery following surgery depends on the extent of the injury and whether spinal fusion was performed.
Patients with associated abdominal injuries or neurologic injury may require a substantially longer recovery.
Potential Complications
Complications can include:
- Progressive kyphosis
- Chronic back pain
- Persistent instability
- Failure of the fracture to heal
- Neurologic deterioration
- Post-traumatic deformity
Potential surgical complications include:
- Infection
- Bleeding
- Dural tear
- Neurologic injury
- Hardware failure
- Nonunion
- Adjacent-level problems
The individual risk depends on the severity and complexity of the injury.
Post-Traumatic Kyphosis
If the injured segment heals in an abnormal position, the spine may develop excessive forward curvature called post-traumatic kyphosis.
This may cause:
- Chronic mechanical back pain
- Difficulty standing upright
- Fatigue
- Progressive spinal imbalance
- Neurologic problems in severe cases
Maintaining appropriate alignment during initial treatment helps reduce the risk of later deformity.
When Is a Chance Fracture an Emergency?
Chance fractures usually result from significant trauma and require prompt medical assessment.
Emergency evaluation is particularly important when there is:
- New leg weakness
- Numbness
- Paralysis
- Difficulty walking
- New bowel or bladder dysfunction
- Severe abdominal pain
- Significant abdominal bruising after a motor vehicle accident
- Loss of consciousness
- Severe or worsening back pain after trauma
Associated abdominal injuries may sometimes be just as important as the spinal injury itself.
Outlook
Thoracic Chance fractures are flexion-distraction injuries that can disrupt the structural stability of the spine.
Some predominantly bony fractures with good alignment can heal successfully with bracing and close observation.
Injuries involving substantial ligament disruption are more likely to remain unstable and frequently require surgical stabilization.
Treatment should be based on:
- Fracture pattern
- Integrity of the spinal ligaments
- Spinal alignment
- Neurologic function
- Associated injuries
- Bone quality
- Overall health
Careful evaluation is also important because Chance fractures can be associated with significant abdominal injuries after high-energy trauma.
Related Topics
- Flexion-Distraction Injury
- Thoracic Burst Fracture
- Thoracic Compression Fracture
- Thoracic Spinal Instability
- Post-Traumatic Kyphosis
- Spinal Cord Injury
- Thoracic Pedicle Screw Instrumentation
- Thoracic Spinal Fusion