15 Classification and Treatment of Thoracic Fractures
Introduction
Thoracic fractures in healthy individuals are uncommon due to the stabilizing effect of the rib cage. However, high energy trauma and predisposing conditions can increase the likelihood of fracture. 1 Although there is no ideal standard for classification of thoracolumbar (TL) injuries, the evolution of the three- column model of Dennis, the AO/Magerl comprehensive classification, and thoracolumbar injury severity scale and score (TLISS)/thoracolumbar injury classification and severity score (TLICS) point system have provided significant insight into anatomy, mechanism of injury, and the implications and therapies for instability. 2 – 4 Multiple surgical techniques address spinal instability, but the choice of surgery depends on the level of injury and anatomy.
Indications
The goal of thoracic spine fracture treatment is preventing deformity, providing stability, and protecting the neural elements. If conservative management is deemed insufficient to provide these goals, then surgical management should be considered. Surgery should be also considered as an adjunct to hasten rehabilitation, shorten hospital stays, and particularly in cases of multiple injury.
Anatomy
The thoracic spine is the longest spine segment and a common site for trauma, especially at its lower segments (T10-T12). 5 The thoracic spine consists of 12 vertebrae with a physiologic kyphotic curve due to wedging of the thoracic vertebrae (a 2- to 3-mm difference in anterior and posterior height). 6
Bony Structure
The vertebral bodies (VB) anteriorly are load bearing and the arches posteriorly resist tension. The anteroposterior (AP) diameter of the VB increases from T1 to T12, while the transverse diameter decreases from T1 to T3 and then increases to T12. 7
The VB sides are concave and the laminae are broad and heavily overlapped. The pedicles project from the superior VB posteriorly. The laminae extend dorsomedially from the pedicles to fuse and form the dorsal wall of the spinal canal.
Facets
The articular processes arise from the superior and inferior laminar surfaces.
From T1 to T10, the thoracic facets are oriented coronally. This minimizes anterior translation during flexion. From T11 to T12, the facets have an oblique sagittal orientation to limit rotation.
The coronal facet orientation of the upper thoracic spine allows for rotation around the craniocaudal axis (75 degrees of rotation to each side) with the greatest rotation at T8-T9. 8 In contrast, lumbar spine rotation is limited by the orientation of the facets and anterior annulus to only 10 degrees.
Ribs
The most distinguishing features of the thoracic spine are the ribs and their two vertebral articulations. Specifically, the rib heads articulate with the vertebrae and the disk. The rib tubercle articulates with the transverse process at the costotransverse articulation.
Demifacets above and below the disk articulate with the head of the rib to form the costovertebral joint (a synovial joint divided by an intraarticular ligament into two separate compartments).
Overall, the rib cage provides the thoracic spine with two to three times the load bearing capacity before instability relative to other spine segments. Sagittal and lateral flexion- extension are also stabilized. Therefore, high mechanical forces must occur to cause thoracic vertebral injuries—often with concurrent injuries to the chest, cervical spine, and head. 9
The radiate and costotransverse ligaments bind the ribs to their vertebrae additionally and provide stabilization. 10
Spinal Cord
The thoracic canal is narrowed with less free space for the spinal cord compared to the cervical spine.
The central thoracic spine also has a limited blood supply, with a lower threshold for vascular cord injury on kyphosis or compression than the lumbar spine.
Spinal cord injury to the upper thoracic spine can have devastating sequelae while root injury in the thoracic spine is far less functionally relevant than in the lumbar spine.
Evaluation and Diagnosis
Initial evaluation of trauma involves assessment for serious life-threatening injuries with rapid resuscitation as necessary. Spinal injury, while common in multiple-system trauma, is frequently unrecognized. 11
Physical Spine Examination
A thorough spine examination is critical in the initial comprehensive trauma evaluation.
Direct examination includes visual inspection and palpation of all spinal segments.
A step-off, localized tenderness, or a soft spot (from laceration, swelling, or ecchymosis) may be the only sign of instability.
Soft-tissue trauma to the chest or abdomen may suggest a seat-belt injury with a TL flexion-distraction injury.
Neurologic Examination
Neurologic exam should include motor strength, sensory function, and reflexes.
If spinal cord injury is suspected, serial exams are necessary as the neurologic exam may change, especially in settings of instability.
Grading by the American Spinal Injury Association (ASIA) Impairment Scale documents the level and severity of the spinal cord injury.
A repeat evaluation should be performed if initial evaluation is inadequate.
Patients with spinal cord injury should be tested for perianal sensation, rectal tone, and bulbocavernosus reflex. Any suspicious findings warrant imaging.
Spine precautions should remain in place until spinal trauma is excluded.
Spinal fractures are missed frequently in settings of multiple injuries. 12 – 15
Indications for Conservative Management
Conservative management should be considered anytime a patient can maintain alignment and neurologic stability without surgery. 1 Stable fractures such as uncomplicated compression fractures may not require bracing as the rib cage and sternum buttress the spine.
Orthoses
If support is needed, compression fractures are routinely treated with an orthosis often with inclusion of the cervical spine. Cervical support could include a mandible, occipital pads, or halo ring and may consist of a cervicothoracic orthosis (CTO) or cervicothoracolumbosacral orthosis (CTLSO).
Orthoses and casts should be used with caution
Sensory deficits may lead to wound breakdown due to pressure ulcerations from an orthosis. Skin contact should be checked frequently and routinely. Emaciated patients with poor soft tissue padding are especially at risk.
Orthoses and casts maybe difficult for patients to remove and the fit may need to be adjusted over time.
Indications for Surgical Management
Surgical decompression is indicated when there is neural compression with worsening neurologic deficit, which may include worsening myelopathy or radiculopathy. 1
In cases where the injury is complete, ASIA A, surgery will likely not result in neurologic improvement; however, stabilization of the spine may be beneficial in facilitating rehabilitation and patient transfers.
Surgical stabilization is indicated for worsening neurologic deficit, disrupted posterior ligamentous complex (PLC), dislocation of the thoracic spine, failure to obtain or maintain correction by nonsurgical means, unacceptable deformity, and intolerance to nonsurgical management.
Denis described a three-column model of the spine. 2 Many believe that mechanical instability results from disruption of two or three of the three columns.
The TLICS/TLISS provides guidelines for when surgical intervention is warranted. 4
While a compression fracture of the anterior column may be mechanically stable in the short term, significant kyphosis or VB collapse may lead to progressive deformity over time.
Cohen et al recommend operative reduction and fusion for any neurologic dysfunction that meets the following criteria 16 :
If any of the compressed vertebrae wedge fractures measure over 40% in a young or middle aged adult
If the compression percentages for the adjacent vertebral wedge fractures combine to greater than 50%
Acute kyphosis is present
Munting recommends surgery when significant pain combined with altered function is reported for a posttraumatic deformity exceeding 20 degrees of sagittal index. 17
Pain is often located about the apex of the deformity. This kyphotic deformity may lead to compensatory hyperlordosis in the lumbar spine and/or hypokyphosis or even lordosis in the thoracic spine above the lesion and cause painful muscle spasm.
Other indicators for surgery include inability to maintain straight vision due to severe kyphosis, pseudoarthrosis, disk degeneration, progressive neurologic deficit, and cosmesis.
Preprocedure Consideration
Radiographic Imaging
Correct diagnosis with physical exam may be difficult, particularly in patients with altered mental status, patients who are intubated or sedated, and patients with multiple pelvis or limb fractures. Initial imaging (plain radiography or CT) is crucial in these cases.
Plain Radiography
AP and lateral plain X-rays of the thoracic and lumbar spine allow the physician to count the number of rib- bearing vertebrae and the number of lumbar vertebrae to ensure accuracy of surgical planning. Care should be taken to evaluate for possible anatomic variants (e.g., cervical ribs or lumbarized sacral vertebrae). However, the upper thoracic column is poorly visualized on plain radiography.
Computed Tomography
Modern computed tomography (CT) allows rapid characterization of spinal fracture morphology and provides critical detail in the acute and therapeutic setting. 1 In a study by Smith et al, nonreconstructed CT detected TL fractures more accurately than plain radiographs and is recommended for diagnosis of TL fractures in acute trauma for patients with altered mental status. 18
Information includes canal narrowing due to retropulsed fragments, better evaluation of unstable rotational injuries, and indirect assessment of ligamentous and disk injuries.
Facet dislocation and posterior interspinous widening due to distraction may demonstrate a “naked facet sign.”
CT myelogram may demonstrate areas of compression of the thecal sac.
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) demonstrates associated soft tissue injury that will not be visible on the CT.
Occasionally decompression of the spinal cord from these soft tissue elements will be indicated even for fractures that appear to be stable on CT.
If the fracture appears to be associated with some pathology, then it may be helpful to include enhanced images in the MRI to determine if the bone appears to have an associated infection or tumor.
Medication
Steroids have had waxing and waning popularity in the setting of acute spinal cord injury. If there is a neurologic injury, some reports have indicated that high dose methylprednisolone has given some benefit. 19 However, these initial reports has not been replicated, and the risk to the patient concomitant with steroid use including life-threatening infections is not inconsiderable. 20 Recent guidelines have recommended against their use. 21
Antibiotics: If the patient has an associated infection, it may be beneficial to obtain a specimen for culture prior to starting antibiotics. Otherwise standard preoperative antibiotics are used, typically cefazolin.
Operative Management
Guidelines for Management
There is no consensus on the best treatment for TL spine injuries. As a rule of thumb, posterior decompression (e.g., laminectomy) may be effective for posterior spinal cord compression in a stable spine. However, laminectomy without instrumentation may destabilize a spine that already has damage to another column and therefore is inappropriate whenever stability is in question. For anterior compression, typically anterior approach is preferred with consideration of anatomic limitations.
McAfee et al provided one of the earliest general treatment guidelines based on specific injury patterns. 22
Compression fracture: observation with follow-up or prefabricated brace immobilization for 12 weeks
Stable burst: custom fitting orthosis or cast immobilization for 12 weeks. L4 and above: TLSO; L5: HTLSO; if kyphosis > 15 degrees, hyperextension cast.
Unstable burst: surgical decompression and stabilization (approach controversial). Consider emergent posterior short-segment decompression and fusion (with external immobilization in a custom TLSO for 12 weeks), and delayed anterior decompression and fusion if the patient has neurologic deficit and residual cord/root compression.
Flexion-distraction (and Chance injury): consider hyperextension cast for a purely osseous injury with no associated neurologic deficit. Consider posterior short-segment stabilization and fusion for associated neurologic injury or abdominal injury or when spine injury is primarily ligamentous.
Fracture-dislocation: posterior long-segment surgical stabilization with pedicle screw fixation two to three levels above and below the injury with local bone graft fusion.
In the 1990s, the first multicenter study (MCSI) of the Spine Study Group of the German Association of Trauma Surgery showed limitations for isolated posterior instrument and fusion techniques in cases with a compromised anterior column.
Since then, operative approaches and adjuncts have advanced considerably to include endoscopic and minimally invasive surgery—advances in interbody support and intraoperative navigation.
The second multicenter study (MCSII) of the Spine Study Group of the German Association of Trauma Surgery reviewed traumatic TL (T1-L5) injuries as an update to MCSI. Of 733 patients with acute TL injuries treated surgically 23 :
380 (51.8%) patients were operated on by posterior stabilization and instrumentation alone
34 (4.6%) had an anterior procedure alone
319 (43.5%) had combined posteroanterior procedures.
Overall they found:
Short angular stable implant systems have replaced conventional nonangular stabilization systems.
Posttraumatic deformity was restored best with combined posteroanterior surgery.
Different surgical approaches did not have a significant influence on neurologic recovery on 2-year follow-up.
Five percent of all patients required revision surgery for perioperative complications.
The most common surgical interventions for thoracic injuries are described below.
Operative Field Preparation
Positioning
The patient is intubated supine and then positioned carefully as needed.
Pressure points are padded.
Intraoperative monitoring including somatosensory evoked potentials (SSEP) and motor evoked potentials should be considered.
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