Trauma to the spinal cord and column is a devastating injury that often results in an abrupt change in the quality of the patient’s life and for those who care for him or her. Aside from the obvious loss of function and ability to interact with one’s environment, many chronic complications often develop over time in this group of patients. These complications can further impede functional as well as emotional rehabilitation. One of these complications involves post-traumatic deformity of the spinal column after acute treatment of a spinal injury. The vast majority of unstable spinal injuries are recognized early and managed with either prolonged immobilization or surgical stabilization. Rarely, the initial treatment may be inadequate, resulting in late instability leading to deformity, pain, and/or increased neurologic deficit. In less obvious injuries less aggressive immobilization techniques may have been chosen, but because of the occult instability and exposure to chronic physiologic stresses, a gradual deformity may become apparent. 8,14
Each year in the United States there are more than 1 million acute injuries to the spine with approximately 50,000 of these resulting in fractures to the bony spinal column. 11 Although there are between 7000 and 10,000 new cases of spinal cord injury each year, for the most part, the majority of spine injuries are minor. They usually involve the soft tissues and do not require surgical stabilization or prolonged orthotic immobilization. The overall incidence of spinal cord injury has decreased nationally for a variety of reasons. These include improvements in emergency medical services, earlier and safer spine stabilization at the scene of an accident, faster transport with the use of helipads, and improved emergency and trauma bay care for these patients. These improvements have led to a reduction in the progression of incomplete spinal cord injuries to complete ones. Other positive factors participating in the overall reduction in spinal cord injury include safer automobiles, increased occupational safety standards, and better regulations involving contact sports. Because of these above-mentioned factors, there has been a increasing trend for improved patient survival with incomplete and complete spinal cord injuries. 22 This ironically has been associated with a greater number of patients presenting with symptoms related to loss of normal spinal alignment or worsening spinal deformity because of vertebral or ligamentous incompetency and at times a secondary deterioration in neurologic function.
Plain radiographs, including anteroposterior and lateral scoliosis views, are important when evaluating the overall balance of a patient with a post-traumatic spinal deformity. Flexion and extension lateral and anteroposterior bending views are also invaluable in assessing the flexibility of any spinal deformity. This allows the physician to have an understanding of the potential extent of correction that can be anticipated at the time of surgical intervention. Comparing follow-up imaging studies with prior films aids in documenting the progression of skeletal changes over time. 8
Computed tomography scanning offers detailed evaluation of the spinal bony architecture through the use of fine 1- to 3-mm cuts along with sagittal and coronal reconstructions. This allows the visualization of subtle structural abnormalities, especially involving the posterior element bony structures that are often difficult to visualize on plain radiography. In patients with new onset neural deficits, computed tomography scanning after myelography can be useful in determining both central and foraminal neural compression.
Magnetic resonance imaging (MRI) is invaluable in visualizing spinal soft tissue structures in great detail. Its use in identifying posterior spinal soft tissue injury helps in determining the extent of potential physiologic instability. The superb visualization of MRI of subtle neural compression and changes within the parenchyma of the spinal cord is extremely important, especially if spinal column manipulation is necessary, which may result in further neural compression.
A post-traumatic kyphotic deformity is an example of a potential complication after spinal trauma, and a comprehensive understanding of normal sagittal plane vertebral relationships is mandatory to effectively manage this spinal disorder. 24
Normal sagittal alignment allows the head to be positioned over the pelvis. A plumbline dropped from the external auditory meatus should pass posterior to the hip joint and through the anterior portion of the sacrum (S1). 24Table 1 summarizes the diagnosis, indications, and surgical approaches for post-traumatic deformity of the cervical, thoracic, and lumbar spine. In the thoracic spine an injury to the anterior column resulting from a flexion–compression-type injury may produce a focal kyphosis at that level. This kyphotic deformity will cause hyperextension of adjacent spinal regions to compensate for the altered sagittal alignment resulting in altered facet joint motion, intervertebral shear, and potential instability, accelerating the degenerative process. 24 If the posterior bony ligamentous column is disrupted, the kyphotic deformity may gradually worsen over time, even if immobilized. If the injury is located primarily to the anterior and middle bony column, rarely, with appropriate immobilization, will the deformity progress. Injuries that involve the posterior ligamentous structures, such as advanced staged burst flexion–compression injuries or flexion–distraction injuries, are prone to post-traumatic deformity if aggressive measures to prevent this occurrence are not taken. This is more common at the thoracolumbar junction where there is a lack of ribs as a supporting structure. 5,6
The focal kyphotic deformity is best measured when making a comparison between the superior and inferior endplates of the vertebral bodies above and below the level of the injury. 24 It has been shown that direct measurement of the fractured vertebrae is fraught with significant observer variation. 23
Surgical intervention is considered if the kyphotic deformity is found to be progressive over time or if there is new evidence or progression of a neurologic deficit. Patients with a localized kyphotic deformity of ≥30° are noted to be at a statistically increased risk for chronic continued pain in their kyphotic region. 13,19,25 Additionally, if the kyphosis is static, a relative indication for surgical treatment is an unacceptable cosmetic appearance usually associated with pain.
A number of procedures exist when surgical management is indicated, including either a posterior or anterior only approach or any variation of a combined anterior and posterior procedure. Posterior stabilization alone is often not sufficient for optimal correction and stabilization of a late post-traumatic thoracolumbar kyphotic deformity. A posterior only fusion in the presence of an existing kyphotic deformity places considerable tension on the instrumentation and bone graft regardless of the adequacy of sagittal plane correction because of the large bending moments (stresses) challenging the correctiveforces needed to obtain adequate spinal alignment. In the vast majority of cases an initial anterior release and/or decompression is favored, which allows greater manipulation of spinal alignment and improved fusion healing success with anterior column reconstruction (Figure 1). Accessing the anterior column is often extremely difficult with the limited exposure afforded by a posterolateral approach. 6,16,25,29 Reports of greater neurologic recovery after an anterior decompressive procedure in the setting of an incomplete deficit compared with a posterolateral approach have been reported even as late as 2 years after injury. 3,9,29
If the deformity is localized to the lower lumbar and/or sacral segments (L4, L5, and sacrum), a posterolateral approach is often the most sensible approach because of the technical difficulty of reconstructing the anterior column in this region. Often an osteotomy is necessary to globally manipulate sagittal or coronal balance. The recent popularity of the transforaminal interbody approach allows access to the anterior column for graft placement without excessive retraction of the neural elements while avoiding an anterior exposure. Roberson and Whitesides used an anterior alone approach in the setting of post-traumatic deformity with 17 of 18 good results in patients who they noted had a stable posterior spinal column. 25 A combined anterior and posterior procedure was used if there were any question about the integrity of the posterior elements. 25 Polly et al 24 reported on the usefulness of the bilateral transforaminal approach in placing of structural grafts anteriorly, which function as a pivot point or axis of rotation for posterior compressive forces used to restore lumbar lordosis. This is an extremely useful approach that allows for an indirect circumferential fusion, especially in patients for whom an anterior approach is undesirable. 24
Flexion compressive- and flexion distraction-type injuries in the lumbar spine resulting in focal kyphosis are tolerated poorly by patients of any size. Symptoms of a flatback posture such as early fatigue and pain from a stooped posture may develop. The surgical management of this deformity is determined by its flexibility as demonstrated on dynamic plain radiography. In a fixed lumbar kyphotic deformity, often either a combined anterior and posterior approach or a posterior alone pedicle subtraction osteotomy is necessary to significantly alter sagittal alignment. Closing wedge osteotomies of this type may achieve up to 35° of focal correction in the sagittal plane and are best used when a localized but large correction is needed. 24
Kyphosis in the thoracolumbar or lumbar spine may also be the result of iatrogenic over distraction of the lordotic lumbar region. This also manifests clinically as a flatback syndrome. Kostuik et al, 15 in 1988, reported on 54 patients with a fixed iatrogenic flatback deformity treated with a combined anterior opening wedge osteotomy and instrumentation followed by a posterior closing extension osteotomy and instrumentation. There was an average increase in lumbar lordosis from 21.5° before surgery to 49° after surgery with significant pain reduction in more than 90% of patients. 15 Shufflebarger and Clark 26 popularized the back-front-back procedure. This included an initial posterior release procedure involving facetectomies and osteotomies followed by an anterior release and reconstruction. The last stage consisted of an instrumented posterior fusion to restore the posterior tension band function of the posterior spinal elements. 24,26
Because it is now well recognized and documented that distraction instrumentation should be used with caution in the lumbar spine, iatrogenic late flatback deformity is decreasing in incidence as a result of greater experience with advanced generation instrumentation systems.
The most commonly encountered postoperative cervical deformity after a decompressive procedure for cervical trauma is kyphosis. Most patients who develop cervical instability and a late kyphotic deformity experience initial pain relief at their index procedure. However, with time and an increase in physical activity, the developing spinal kyphotic deformity results in symptoms of increasing neck pain and/or recurrent neurologic symptoms.
Surgical treatment involves the same principles involved in managing kyphotic deformities in other areas of the spine. This involves lengthening of the anterior spinal column and shortening of the posterior spinal column. The most common anterior approach involves either segmental decompression via release of the anterior longitudinal ligament and discectomies followed by bone grafting or a multilevel corpectomy if significant stenosis exists behind the vertebral bodies. The posterior longitudinal ligament is preserved, if possible, to act as a hinge at the time of deformity correction. Posterior procedures involve shortening of the posterior column through inferior facet resections followed by fusion and segmental instrumentation. Osteotomies may be needed if the facet joints are fused. Before placement of instrumentation, the head may be positioned into further lordosis after the decompressive procedure (Figure 2). Abumi et al 2 reported on 30 patients who underwent pedicle screw fixation for the treatment of cervical kyphosis. Seventeen patients had flexible kyphotic deformities and underwent posterior procedures alone, whereas 13 patients had rigid kyphotic deformities requiring combined anterior and posterior procedures. At follow-up both groups had marked improvement in their cervical alignment, with an average correction from 30.8° to 0.5° of kyphosis in the rigid group at final follow-up. 2
Lateral compression or burst injuries may at times result in a post-traumatic coronal or scoliosis deformity. As with late kyphotic deformities, indications for surgical intervention include documented progression of deformity leading to spinal imbalance or development or worsening of a neurologic deficit with or without pain refractory to conservative measures.
Miscellaneous Causes of Post-traumatic Deformity
Nonunion may also result in a progressive spinal deformity. This often presents as increasing pain localized to the surgical site with radiographic evidence of instrumentation fatigue and bone nonhealing. A thorough workup to exclude a deep infection must ensue because this may mimic or be responsible for a symptomatic nonunion.
Implant dislodgement is the most common reported complication resulting in a post-traumatic deformity after posterior instrumentation and has been reported in up to 16% of patients in some series. Causes may include excessive force at the implant bone junction, technical errors, poor implant selection, weak and osteoporotic bone, and brace wear noncompliance. 11 Further surgery is often needed with repeated bone grafting (Figure 3).
Laminectomy and Fusion Length
Keene et al 14 have reported that of 106 patients who had operative stabilization of thoracolumbar fractures, 16 (15%) underwent surgery 4 months to 16 years later for chronic instability. The risk factors noted by these authors for post-traumatic deformity at the thoracolumbar junction included a prior laminectomy or a short fusion segment. Improved spinal alignment was seen when at least five levels or more were incorporated into the fusion and when a posterior laminectomy was not performed. 14
Spinal cord injury resulting in either complete quadriplegia or paraplegia may result in a rare complication leading to a post-traumatic deformity known as a Charcot spine. This deformity may present as late as 31 years after the initial injury. 20,28 It can be seen in patients initially treated nonoperatively or operatively. This deformity is a consequence of the insensate nature of the vertebral elements below the level of the spinal lesion. In patients with a neuropathic spine, abnormal movement between the vertebrae takes place, leading to destruction of the cartilage, fracture of the subchondral bone, and ultimately collapse of the vertebrae resulting in a giant pseudarthrosis. Complications associated with a Charcot spine include worsening back pain, loss of spasticity, obstructive uropathy with changes in bladder function, crepitance with motion at the Charcot lesion level, a progressive gibbus formation, and loss of sitting balance with the development of decubitus ulcers. 8,28 Radiographically, the early stages demonstrate hypertrophic bone formation around the vertebrae adjacent and below the level of the cord lesion or just below a previous fusion level (Figure 3). 8,20,28 The disc spaces and endplates may appear fragmented as well. These changes then progress to massive periosteal bone formation and finally a giant ball-and-socket pseudarthrosis leading to an audible crepitance or clunk with motion with progressive kyphosis, flexion instability, and loss of height. 20 Rapid progression may occur with this disorder, and frequent radiographic evaluations are indicated to identify individuals who may require spinal stabilization to manage this difficult deformity. 10,27 An anterior fusion with partial resection of the Charcot joint followed by posterior spinal instrumentation and fusion has shown good results with kyphosis correction at 30 months. 10,20 The possibility of developing secondary levels of Charcot arthropathy below a previously successful fusion has been shown. 10
One of the most common symptoms of post-traumatic deformity is pain. It is typically constant and aching in character in the apical area of the deformity, which is increased by bending, lifting, twisting, and prolonged standing or sitting. 19 This is the result of abnormal forces placed on the soft tissue structures surrounding the spinal column deformity causing fatigue and pain. Often the precise origin of pain is difficult to identify. Pain may also be secondary to premature degenerative changes associated with the spinal deformity. Pain relief from surgical intervention in spinal deformity is less than predictable and should not be considered exclusively as an indication for surgical intervention.
Bohlman et al have shown that late anterior decompression, at an average of 4.5 years after the initial traumatic event, for chronic pain or paralysis after thoracolumbar fractures with canal compromise has resulted in significant pain relief in 41 of 45 patients at follow-up. 7
Malcolm et al 19 reviewed 48 patients with a post-traumatic deformity, of which 13 (27%) were noted to have an increasing neurologic deficit. 19 A cause for neurologic deterioration after an initial improvement or plateauing of neurologic function, besides a progressive deformity, may be the development or an expansion of an intracord cyst or cavity, i.e., post-traumatic syringomyelia or progressive post-traumatic cystic myelopathy. With the wide availability of MRI, post-traumatic cystic myelopathy has been recognized and diagnosed with increasing frequency. A prevalence of between 3.2% and 40% has been reported in the literature in spinal cord injury patients. 12,17 Up to 75% of patients may present with worsening neurologic function on initial evaluation. There are many causes of post-traumatic cystic myelopathy, including tethering of the spinal cord, arachnoiditis, microcystic cord degeneration, and spinal cord compression secondary to spinal column instability. 17 The pathoanatomy of post-traumatic cystic myelopathy or post-traumatic syringomyelia involves the presence of large confluent cysts within the spinal cord. The presence of microcysts in the absence of a large cyst, with tethering of the cord and myelomalacia, is referred to as post-traumatic myelomalacic myelopathy. 17 Surgical treatment of this syndrome involves shunting the syrinx and releasing the tether or cyst fenestration, which has recently been reported. Shunting of the cyst has been met with disappointing long-term improvement with shunt revision frequently needed in up to 50% of patients. 4
Post-traumatic kyphosis fortunately is a primary cause of neurologic deterioration in a minority of patients. According to a recent study, patients with less than 15° of post-traumatic kyphosis and/or less than 25% of post-traumatic stenosis were one half as likely to develop hydromelia than with patients with a greater deformity. 1 Abel et al 1 reported a group of patients (n = 68) without spinal cord cystic degeneration who were found to have progressive loss of neurologic function in the setting of a post-traumatic deformity. Neurologic dysfunction in this setting was the result of progressive kyphosis, stenosis, instability, arachnoiditis, and cord tethering. 1 This heightens the treating physician’s vigilance in preventing the potential for deformity occurrence with early surgical intervention if spinal alignment changes become obvious in the post-traumatic period.
The results of surgical management of post-traumatic instability is influenced by many factors including the age and medical status of the patient, the type of initial injury, the time duration between the initial injury and deformity correction, and the experience of the treating physicians. Keene et al 14 reported good to satisfactory results after the surgical treatment of post-traumatic deformities resulting from flexion–distraction (6), burst (1), and fracture–dislocation (1) type injuries. Only two of eight (25%) patients with a wedge compression fracture had a good or satisfactory outcome. The two patients with good results had 30% to 40% vertebral body collapse at the time of surgery, whereas the six patients with poor results had more than 40% vertebral collapse at the time of surgery. The type of surgical reconstruction in this group of patients, i.e., fusion, had little effect on overall outcome. The timing of reconstructive surgery had an influence on outcome as patients operated within 12 months of their injury had a better outcome than those operated on at a later date. 14 Lehmer et al reported a 93% maintenance of correction and a 100% fusion rate in 38 patients undergoing a posterior closing wedge osteotomy for late thoracolumbar kyphosis with 76% of patients stating that they would repeat the surgery. 18 Posterior decompression with instrumentation and fusion of one segment both above and below the level of a rigid post-traumatic kyphotic deformity has been reported by Wu et al; they reported on 13 patients with an average kyphotic correction of 38.8° at 2-year follow-up. 30
The potential for neurologic injury is increased in the surgical management of a post-traumatic spinal deformity because of the draping of the neural elements over the anterior vertebral elements, the presence of a pre-existing spinal cord injury, and the possibility of scarring with cord tethering. New onset or progressive neurologic injury is rarely reported in the nonoperative management of spinal injury and is reported to be approximately 1% after all spinal surgery. This is undoubtedly higher in the surgical management of post-traumatic spinal deformity. This may be related to several factors including instrumentation placement within the spinal canal or more commonly spinal cord tethering from deformity correction. Spinal cord intraoperative monitoring is extremely useful in detecting any change in neurologic function during surgical manipulation. 11
Patients treated surgically for post-traumatic deformity are often debilitated and chronically colonized in their respiratory and genitourinary tracts because of prolonged hospitalizations and extended rehabilitation stays. Depending on their neurologic status, many patients often have open decubiti leading to an increased infection rate with any open surgical procedure. Postoperative infections in these patients are often the result of less virulent but occasionally multiple organisms.
A rare complication reported in patients undergoing surgical procedures for spinal deformity includes a chylothorax. This is a result of direct injury to the lymphatic system via an anterior thoracic exposure. Chylothorax usually develops a few days after surgery, and symptoms may include chest pain, dyspnea, breathlessness, tachycardia, and low-grade fever. Proper microbiologic workup is necessary as the draining fluid from the wound or chest tube may be confused with a bacterial infection. Conservative management is the mainstay of treatment with surgery rarely needed. 21
Trauma to the spinal cord and column is a devastating injury that may be fraught with many complications including post-traumatic deformity. Certainly, the best treatment is prevention, with close follow-up and early intervention when needed. Once present, the treatment of post-traumatic deformity follows basic biomechanical principles consisting of re-establishing the integrity of the compromised spinal columns so that spinal stability can be restored. This may involve an anterior, posterior, or a combined surgical approach. Great care must be given when manipulating the sagittal profile of the spinal column so as not to overlengthen the neural elements, which is poorly tolerated, especially in the setting of a pre-existing spinal cord injury. The surgical management of post-traumatic deformity is a challenging problem. The treating physician must pay strict attention to the biomechanics of the entire spinal column and be cognizant of the response of the neural elements to any form of manipulation. This will hopefully allow a successful surgical and functional outcome.
- Post-traumatic deformity, especially kyphosis, is a potentially devastating complication after injury to the spinal column.
- Proper understanding of spinal biomechanics is paramount for the appropriate application of surgical reconstruction and stabilization procedures.
- There is an increased risk of neurologic injury with surgical correction because of kyphotic deformity, prior spinal cord injury, and neural scarring.
- Long-term outcomes have been more satisfactory with earlier surgical intervention.
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