Cervical Spine Fracture with Extreme Dislocation in a Patient with Ankylosing Spondylitis: A Case Report and Systematic Review of the Literature
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.360906
Source of Support: None, Conflict of Interest: None
Keywords: Ankylosing spondylitis, cervical spine, dislocation, fracture, intraoperative CT, kyphosis
Spinal fractures, particularly cervical spinal fractures, are common in patients with ankylosing spondylitis (AS). AS is characterized by pathological ossification of the ligaments, disc, endplates and apophyseal structures, which results in remodeled, squared vertebral bodies resembling bamboo spine., The flexible spine is gradually turned into a rigid and kyphotic structure. Though there is abnormal calcification, there is osteoporosis in AS which predisposes these patients to spinal fractures. Management of spinal fractures is particularly challenging due to certain features of AS. We present a case of cervical spine fracture with extreme dislocation in a patient with AS, discuss the surgical nuances in such cases, and review the pertinent literature.
A 56-year-old male, a taxi driver, was brought to our emergency department after having met a road traffic accident. On arrival, the patient was conscious and oriented, but he was unable to move any of his limbs. Neurological examination revealed C7-level American Spinal Cord Injury Association (ASIA) grade B spinal cord injury (SCI). He was put in a rigid cervical collar. He was not maintaining oxygen saturation and was intubated and required inotropic support as well. His past medical history was unavailable. The treating team was not aware that he had AS, and thus, no support was given under his head till CT and MRI were done to compensate for kyphosis. Lateral radiograph did not reveal any fracture/ dislocation [Figure 1]. CT scan revealed C6–7 fracture–dislocation with features suggestive of AS [Figure 1]. The fracture involved all the three columns and extended through C7 body anteriorly and through the C6–7 disc posteriorly [Figure 2]. MRI revealed the same fracture with compression over the posterior aspect of the spinal cord by the C7 lamina [Figure 3]. His Subaxial Cervical Spine Injury Classification (SLICS) score was 9. His fracture was classified as C7 type C.N4.M3 as per recent AO spine subaxial cervical injury classification.
He was taken up for surgery within 24 hours of injury. Cervical traction was not used to avoid overdistraction. The plan was to perform a 360° fixation, anterior followed by posterior fixation. A lot of time was spent on positioning the patient as we did not have any photograph of the patient before trauma and did not know about the kyphotic alignment of the spine. We wanted to fix the fracture in his natural alignment. Hence, we gradually increased the height of pillows under his head so that we could match the natural alignment of his cervical spine [Figure 4]. We used intraoperative CT scan in this case as the cervicothoracic junction was not seen in C-arm.
After an alignment of the cervicodorsal spine was achieved, the patient was prepped and draped for anterior cervical surgery. The cervicothoracic junction, kyphosis and need of multilevel fixation led us to choose longitudinal incision for anterior cervical approach. We exposed from C5 to D2. There was a gap of 7–8 mm between the fractured segments which was filled using iliac crest bone graft, and an anterior cervical plate extending from C5 to D2 was used and fixed using long screws [Figure 5].
Patient was hemodynamically stable and was turned prone in the same sitting. There was a lot of bleeding during posterior cervical spine exposure. The patient underwent bilateral C4, 5 and 6 lateral mass screws and pedicle screws in D1, 2 and 3. Total blood loss was 1000 ml, but the patient was hemodynamically stable at the end of procedure. The patient required mechanical ventilation for a prolonged duration, and there was no change in ASIA grade.
He developed ventricular tachycardia a few weeks later and was successfully cardioverted. He died of myocardial infarction about 2 months after injury while in hospital.
There were many technical challenges in our patient. It was difficult to position the patient in a kyphotic alignment in the presence of extremely unstable fracture, and our ignorance of his previous degree of kyphosis added to this difficulty. C-arm was not useful due to the fracture location and intraoperative CT had to be used. It can be challenging to access the anterior aspect of cervical thoracic junction in a patient with cervical kyphosis for surgeons not used to this approach. It was challenging to guide the screws in optimum trajectory, as the discs were calcified, and to get adequate purchase for screws of anterior cervical plate. Normally, the cervical plates have lordotic curvature. We straightened the cervical plate so that the cervical spine is fixed in the normal alignment of this patient. There was excessive bleeding during posterior cervical exposure. Identifying the entry points of screws and trajectory was difficult too. Nursing in postoperative period was challenging too, as non-maintenance of the kyphotic alignment may lead to screw pullout due to the osteoporosis.
AS is a seronegative spondyloarthropathy.,, It is a progressive systemic disease which is linked to the human leukocyte antigen B27 (HLA-B27) in 95% of cases., On the other hand, only 5% of patients who are positive for HLA-B27 develop AS. The reported prevalence varies from 0.1% to 1.4%, and gender- and geography-based variations are well known. Most of the time, it starts from the sacroiliac joint and then spreads rostrally, but other patterns have also been described. Disease onset occurs before 30 years of age in 80% of patients.,, However, fractures are seen only when the disease has become severe, which occurs in the latter part of their lives.
The cumulative incidence of spinal fracture 30 years after diagnosis of AS was found to be 17%, which increased further with increasing disease duration.,,,
Pathophysiology of spinal fractures in AS
The risk of fractures in AS patients has been estimated to be 7.7 times higher than in the normal population.,,, There are various pathological features of AS which are responsible for this increased risk.
AS is characterized by pathological ossification of the ligaments, disc, endplates and apophyseal structures, which results in remodeled, squared vertebral bodies resembling bamboo spine.,,,, The flexible spine is gradually turned into a rigid and kyphotic structure.
The abnormal calcification does not result in increased strength; rather, there is osteoporosis as the ectopic bone is formed in the areas of ongoing inflammation with high osteoclastic activity, resulting in poor mineralization of the bone. DEXA scan measures the bone mineral density falsely high, due to the presence of syndesmophytes.,,
Osteoporosis is an important cause of fracture and also poses problems during surgical fixation. Osteoporosis along with rigid kyphotic structure of the spine makes the person prone to fractures even due to minor or low velocity trauma.,
Comorbidities in AS patients
There is associated ankylosis of the costovertebral joints as well, which results in restriction of chest movements. It plays a significant role in the morbidity of these patients in the perioperative period, compounded by the fracture-related and postoperative pain. Patients with AS have many medical comorbidities that involve the respiratory system, cardiovascular system, eye (uveitis), gastrointestinal system, etc., These increase the risk of any surgical intervention in these patients.
Characteristics of cervical spinal fractures in AS
A common feature of fractures in AS patients is that they occur at the level of intervertebral disc, as the calcified disc is the weakest part in the otherwise stiff spine. There is also a high prevalence of extension type of fractures, reported in up to 74% of cases. There is an associated significant instability and chances of dislocation are high if the patient is not positioned properly., Hence, they require early fixation in order to prevent further damage to the spinal cord.
Andersson lesions are specific to AS and were first described by Andersson in 1937. It denotes localized vertebral or discovertebral lesion. They occur as a result of the non-union of a spine fracture due to mechanical stress, ultimately leading to pseudoarthrosis. Many other names like “spondylodiscitis”, “discitis”, “diskitis”, and “sterile diskitis” have been used to describe these lesions, which point toward the unclear etiology of these lesions. Once, infection was also considered to be the cause. Usually there is no need of biopsy, and these are managed conservatively. Surgical fixation is reserved for patients for whom non-operative management fail.
SCI in spinal fracture in AS
The cervical region is the most commonly involved part of the spine in AS-related spinal fractures, and a majority of these fractures occur at C6 and C7. The chances of a patient with AS developing SCI after a spinal fracture are higher than in a patient without AS: 11.4 times as per a study. Complete SCI is also more common, as is secondary deterioration following trauma in AS patients with spinal fracture. Causes of secondary deterioration include missed fracture on initial assessment or non-maintenance of cervical spine alignment during shifting of the patient or damage during positioning in CT/MRI gantry or formation of extradural hematoma. The risk of a patient with AS developing a new onset deficit following a cervical fracture is three times that of a normal patient.
Overlooking a fracture on radiology
It is very easy to miss a fracture in AS patients: One study estimated that 17% of fractures were missed due to both patient- and physician-related errors. The various causes of missing a fracture in these patients include the poor visualization of the bone on radiographs due to poor mineral density; most of the fractures occur at the cervicothoracic junction, which is difficult to visualize on normal radiographs; fractures can occur after trivial trauma which might be ignored by the patient or doctor; and the presence of AS-related chronic pain makes the patient ignore symptoms which might arise from a fracture. Both MRI and CT are recommended in these patients to detect all of the fractures, as each modality of these can pick some fractures missed by the other modality.
Medical vs surgical management of fractures in AS patients
The indications of surgery in these fractures include presence of spinal instability, spinal dislocation and neurological deficits. Non-surgical management of these fractures in patients without neurological deficits or dislocation by means of immobilization has resulted in very poor results.,,, High rates of delayed dislocation, as high as 60%, has been reported in literature apart from other complications of immobilization, like pressure sores and pulmonary complications, etc. The risk of surgery is also higher in AS patients compared with patients without AS., The risks involved include the risk of excessive bleeding during surgery and extradural hematoma formation, and implant-related complications like pullout. Complications occurred in up to 84% of the patients in a systematic review.,
Challenges in surgical management of cervical spinal fracture in AS patients
Osteoporosis is one of the biggest challenges involved in the surgery of patients with AS with spinal fractures. There are high chances of fractures and screw pullout. Fixation is extended across extra levels to get more screw pullout strength. Despite this, re-dislocation is not uncommon in these patients.
Fixation across the cervicothoracic junction (CTJ) is required as most of these fractures involve C6 and C7, which is challenging from the anterior approach in the presence of kyphotic deformity. Visualization of the CTJ on fluoroscopy is required to check for the alignment of spine and if the dislocation has reduced. Usually, it is difficult to visualize the CTJ on fluoroscopy in patients with short neck; it becomes even more difficult in patients with AS due to coexistent kyphosis and poor bone quality. An intraoperative CT is helpful and can overcome these difficulties.
All of the landmarks used in spinal instrumentation are lost due to calcification of the disc, cartilage and obliteration of facet joints. Hence, free hand instrumentation becomes challenging. Use of C-arm or intraoperative navigation is helpful.
Shifting of an AS patient with cervical spinal fracture needs to be done very carefully as these fractures are unstable. Head position needs to be maintained with the head in flexed position because of the kyphotic cervical alignment which is different from normal patients. Everyone involved in the care of the patient needs to be aware of the desired head position of these patients. Similarly, while getting CT and MRI of these patients, one has to provide adequate support under the head, and neck should not be extended.
There is higher bleeding during exposure of spine and from bones in these patients than in non-AS patients. There is risk of extradural hematoma following surgery has been described in literature.
Choice of surgical approach
The choice of approach depends on the fracture type. Usually three-column injuries require 360° fixation. Combined anterior and posterior fixation has been found to yield good results with less chances of re-dislocation. It can be done in a single stage or in two stages., A single stage surgery obviates the need of repeated anesthesia but can lead to a higher risk of infection. However, the risks of surgery increase with the increasing duration of the surgery. Posterior-only approach is used more commonly in thoracic and lumbar fractures and less often in cervical fractures.,
Kanter et al. proposed a management algorithm for AS patients with cervical spine fractures. They proposed that patients with acute incomplete cord injury should be operated on as early as possible, preferably within the first 24 hours. Patients with complete cord injury were recommended to be stabilized before being taken for surgery. They recommended direct spinal fixation for patients with acute SCI without any spinal deformity. The surgical approach can be decided depending on the case. Patients who presented late after trauma or who had spinal deformity were put on traction less than 5 pounds to avoid overdistraction. A single-stage, posterior spinal fixation can be done if the spinal deformity reduces after traction. Anterior spinal fixation can be added to post spinal fixation if the spinal deformity is not completely reduced.
Intraoperative reduction can be tried when spinal alignment is not achieved with preoperative traction-like drilling of the facet complex or spinous process leverage traction on the dislocated facet posteriorly. Multilevel fixation is recommended as the bone strength and screw purchase is considerably weak in AS patients. The average number of levels fused in a series by Kanter et al. were 5.6 levels (range 2–8 levels).
They recommended prolonged use of cervical traction when access to the anterior cervical spine is limited because of high-grade kyphosis. An osteotomy can also be used in such cases. Osteotomies are well described in literature and have been recommended at C7/T1 levels., However, osteotomies carry risks and should be used only when absolutely required.
Cervical spine fractures are common in patients with AS, and management of these fractures is challenging due to many factors. Proper surgical planning is essential for a good outcome. Long segment fixation in neutral alignment for the patient is required. Spinal precautions should be followed in patients with suspected spinal fractures following road traffic accidents.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]