Individual subaxial cervical spine injuries represent a wide spectrum of damage to the anatomic structures of the neck, including fractures, ligamentous injury, and disk disruption, often with injury to the cervical spinal cord and nerve roots. Although each injury is unique in terms of the particular complex of bone and soft-tissue disruption, some type of classification is necessary as an intellectual framework to develop consistent treatment algorithms. Some variation of the Allen and Ferguson mechanistic classification system continues to be used as the basis for injury classification.2 Unfortunately, the complexity of individual injuries, often comprising different types of injuries to multiple segments of the spine, frequently necessitates complex reconstructive strategies. Few clinical series describe a pure population of a single subaxial cervical spinal injury type treated completely uniformly.
Summary of Previous Findings
The previous medical evidence-based guideline on this topic focused on “the utility of closed reduction with or without external immobilization compared to arthrodesis with or without internal fixation.” Several generalizations can be distilled from that early medical evidence-based review. Treatment with external immobilization only (traction or orthosis) failed to maintain adequate spinal alignment in approximately 30% of injuries treated in that fashion. Approximately 9% of surgically treated patients had a similar fate. Vertebral compression of 40%, kyphosis of 15%, or vertebral subluxation > 20% were cited as risk factors for failure of external immobilization. A greater proportion of failed alignment patients had residual cervical pain compared with similarly treated patients in whom anatomic spinal alignment was achieved and maintained. Twenty-six percent of patients failed closed reduction of their cervical facet dislocation injuries, whereas 96% of patients treated surgically (open reduction) achieved successful reduction. Anterior plate fixation and posterior lateral mass plate/screw systems were both highly successful at maintaining spinal reduction and alignment postoperatively. Posterior fusion procedures were associated with a higher rate of complications (37%) than anterior fusion procedures (9%).1
Four articles in the current literature review were identified that dealt with the nonsurgical management of subaxial fractures: 3 articles related to unilateral subaxial facet injuries and 1 article related to compressive flexion injuries.
Unilateral facet injuries represent a broad spectrum of potential degrees of mechanical instability. Although the injury to the facet complex itself is often obvious, it can be difficult to determine whether the amount of injury is sufficient to render the spine unstable to the point where external immobilization would likely be inadequate to maintain spinal alignment to facilitate healing. In 1997, Halliday et al3 studied 24 unilateral facet injuries and evaluated these injuries by magnetic resonance imaging (MRI). Injuries to the anterior longitudinal ligament, posterior longitudinal ligament, facet capsule, and interspinous ligament were studied. Patients were treated both surgically and nonsurgically in their retrospective series. Twelve patients were treated nonsurgically. Six of the 7 treatment failures in this group had 3 of 4 ligaments injured. Eight of 12 surgically treated patients also had at least 3 ligaments injured. Spector et al4 studied 24 unilateral facet fractures treated nonsurgically. Five of these injuries eventually required surgical stabilization either for loss of position or for the development of radiculopathy. In addition, 4 of 6 patients who presented with radicular complaints had no improvement of their symptoms by the end of the study period. These authors found that fractures involving ≥ 40% of the absolute height of the intact lateral mass or an absolute height of 1 cm were at increased risk for failure of nonoperative treatment. Lee and Sung5 described 39 patients treated with single-level anterior interbody fusion for unilateral lateral mass fractures. In their cohort study, 15 patients were initially treated nonoperatively. Twelve of these 15 patients eventually required surgical treatment. The authors, however, did not detail the reasons for their nonoperative treatment failures.
In 2002, Fisher and associates6 reported a retrospective cohort study comparing halo vest immobilization with anterior cervical fusion for the treatment of subaxial cervical compression-flexion (teardrop) fractures. Four of 24 patients treated in a halo device eventually required surgical treatment. The average kyphosis in the halo treatment group was 11.4° compared with 3.5° in the group treated with instrumented anterior fusion (21 patients). However, functional outcome, as judged by Short Form-36 scores, was equivalent between the 2 groups. Although the patients were matched in many respects, because of the retrospective nature of the series and the manner in which treatment was determined (based on the preference of the attending surgeon), this study offers Class III medical evidence.
Proponents of anterior internal fixation and fusion for the treatment of acute subaxial cervical spinal fractures cite several potential advantages of this treatment approach. Patient positioning is safe and straightforward, obviating the need to turn the patient prone with the potential of an unstable injury. The surgical dissection is accomplished along defined tissue planes with little if any iatrogenic muscle injury. Ventral decompression of the spinal cord can be performed under direct visualization. However, anterior screw/plate instrumentation may be biomechanically inadequate to control instability postoperatively. Several authors have investigated the utility of standalone anterior instrumentation and fusion in the treatment of subaxial cervical spinal injuries.
Woodworth et al7 performed a retrospective review of 19 patients with a mixture of injury types treated with anterior decompression and fusion. They reported an 88% fusion rate with only 1 instrumentation failure. There were no cases of neurological deterioration and no infections. Kasimatis et al8 described a series of 74 patients, also with a mixture of injury types. Ninety percent of the patients in their series achieved success fusion. Although they reported 11 postoperative infections (15%), only 3 patients required revision surgery. Reindl et al9 reported a retrospective series of 41 consecutive patients with “disruptions of both anterior and posterior structures and subluxation or dislocation of at least one facet” treated with anterior instrumented fusion. All patients went on to solid fusion with no loss of reduction or instrumentation failures. One patient experienced a transient neurological deterioration. Six of 19 patients with a spinal cord injury on admission improved at least 1 Frankel grade. Twenty percent of patients had transient dysphagia postoperatively, and 20% had persistent moderate to severe neck pain at last follow-up.
Other authors have reported on anterior internal fixation and fusion more specifically for facet and lateral mass injuries. Lee and Sung5 described 39 patients treated with a single-level anterior fusion for unilateral lateral mass fractures. Radiographic failure was observed in 8 patients (21%). Three cases had instability or malalignment at an adjacent segment; 5 cases had incomplete reduction of their subluxation injuries. Henriques and associates10 reported a series of 39 patients with ligamentous unilateral and bilateral facet dislocations treated with anterior instrumentation and fusion. Only 2 of 17 patients with unilateral injuries lost reduction postoperatively. Conversely, 7 of 13 patients with bilateral injuries demonstrated postoperative recurrent subluxation. Although no statistical analysis was performed on this small sample, the authors noted that 4 of 5 patients with complete neurological injuries and bilateral facet dislocations had radiographic failure. Johnson et al11 published a retrospective series of 87 patients (of 107 total) with unilateral and bilateral facet injuries treated with anterior instrumentation and fusion. Thirteen percent of patients suffered radiographic failure; none had neurological deterioration. Analyzing the 11 patients who suffered a loss of reduction after surgery, the authors identified facet fracture (10 of 11), endplate fracture (9 of 11), and C6-7 injury level (8 of 11) as risk factors for radiographic failure in their experience.
Proponents of posterior fixation and fusion as treatment for subaxial cervical spinal fracture injuries cite superior biomechanics as the primary advantage of this internal fixation strategy. Furthermore, open reduction of facet dislocations is straightforward with the posterior approach and has been the traditional surgical method used. Five contemporary articles reported clinical series of subaxial injuries treated with posterior fixation and fusion. Kotani et al,12 Zhou et al,13 and Yukawa et al14 all reported retrospective series of patients treated with pedicle screw instrumentation for a variety of subaxial injuries. Overall, these series document a low rate of instrumentation-related and other complications and good neurological recovery with this demanding surgical technique. Lenoir and associates15 reported a series of 30 patients treated with posterior fixation and fusion for fractures around the cervicothoracic junction, an area where instrumentation failure has been felt to be common because of high biomechanical stress. Five patients with similar injuries were also treated with anterior decompression and fusion with internal fixation (dorsal-ventral combination procedure). The postoperative pulmonary infection rate (30%) and mortality rate (23%) were high in patients with these severe high-energy injuries, but the number of instrumentation failures (2) and wound infections (2) was low. Finally, Pateder and Carbone16 described a series of 29 patients with a mixed series of cervical spinal subaxial injuries treated with posterior lateral mass screw fixation and fusion. Of these 29 patients, only 1 experienced instrumentation failure and 1 suffered a root injury. There were 4 postoperative wound complications. On average, the authors noted a 2° loss of correction in sagittal angulation with posterior operative reduction and internal fixation techniques.
Several authors have reported series of patients treated with a combination of anterior and posterior decompression, internal fixation, and fusion techniques. Harrington and Park17 treated unilateral and bilateral facet injuries with single-level arthrodesis in 22 patients. The authors did not differentiate outcomes between the anterior standalone and anterior and posterior techniques. They reported 68% correction of sagittal angulation and 70% correction of translational deformity for unilateral injuries compared with 51% and 65%, respectively, for bilateral injuries. They identified no nonunions or cases of neurological deterioration. Toh et al18 reported a retrospective study of 31 patients treated with a variety of surgical techniques (24 anterior, 7 posterior) for a mixture of subaxial cervical spinal injuries (11 burst fractures, 20 teardrop injuries). The group treated with posterior fixation and fusion had higher rates of postoperative spinal canal compromise and required more spinal levels to achieve effective fixation. Bone fragment removal and decompression of the spinal canal were better for patients treated anteriorly compared with those treated posteriorly. Nine of 24 patients treated with anterior surgery improved neurologically, but none of the patients treated posteriorly improved. No Frankel A patient recovered motor function regardless of treatment. Song and Lee19 compared anterior and combined anterior and posterior internal fixation and fusion techniques in a series of 50 patients with distractive subaxial cervical flexion injuries. They found no differences in the rate of union, complications, or radiographic or neurologic outcomes. Lambiris et al20 published a comparative cohort study of patients undergoing either anterior (74 patients) or posterior (23 patients) fixation and fusion for a variety of subaxial cervical spinal injuries. They reported no difference in the complication rates between the 2 techniques.
Brodke and colleagues21 randomized 52 consecutive patients with unstable subaxial cervical spine injuries to anterior or posterior stabilization and fusion. Injuries in all patients were reduced and decompressed preoperatively by closed reduction; therefore, the choice of surgical approach was not dictated by the need to decompress the spinal canal. The authors found no difference in the neurological outcome, final degree of kyphosis, fusion status, or rate of complications between the 2 surgical approaches. Because of the small number of patients included in this randomized comparative study (inadequate study power), this report provides Class III medical evidence.
Kwon et al22 performed a prospective randomized trial of unilateral facet injuries comparing anterior with posterior internal fixation and fusion techniques in 42 patients. All injuries were judged to require surgical stabilization by the treating surgeon. Patients with significant vertebral body fractures, disk herniations, or spinal cord injuries were excluded from the trial. The authors found no difference in the primary outcome: time to fulfill criteria for hospital discharge. They also found no difference in postoperative pain scores, 1-year self-reported outcomes measures, or fusion rates. More than 50% of the patients treated with anterior fusion procedures complained of dysphagia, all of which reportedly resolved by 3 months. Four of 22 patients treated with posterior internal fixation and fusion procedures suffered wound complications (1 deep, 3 superficial); none of the 20 patients treated anteriorly had wound complications. Patients treated with posterior procedures had statistically more kyphosis (1.6°) compared with those treated with anterior procedures (8.8° lordosis). Patients treated with plates posteriorly had more kyphosis than those treated with wires, although the plates used were not constrained. Because of the small number of study patients and because the primary study end point was only meeting criteria for hospital discharge, this study was considered to offer Class III medical evidence on this issue.
In the previous version of the guideline on the treatment of subaxial cervical spinal injuries, the author group noted that comparatively few studies examined the specific difficulties associated with the management of patients with ankylosing spondylitis (AS) who sustain subaxial cervical spinal injuries.1 Results of the treatment of these patients were rather dismal. In 4 articles reporting patients with this entity and subaxial injuries, 9 of 22 total patients died. Four patients managed nonoperatively died. Two of 9 survivors treated with external immobilization failed treatment. One worsened neurologically when placed in a halo and was subsequently treated successfully with laminectomy and posterior internal fixation and fusion. The other patient had persistent cervical subaxial spinal instability but refused further therapy. In contrast, 5 of 9 AS patients with subaxial cervical fracture injuries treated primarily with surgery died. One patient was neurologically worse after surgery. Three patients healed successfully without instability.23-25
Four additional reports concerning the care of patients with AS and subaxial cervical spinal injuries were identified in the current literature search. Cornefjord et al26 published a retrospective case series (Class III medical evidence) of 19 patients with AS and subaxial cervical spine fractures treated with posterior fixation and fusion. Four patients were also treated with anterior fusion procedures. Five patients died during the follow-up period, but no deaths were related to surgery. All patients sustained fractures after low-energy trauma. One patient deteriorated neurologically postoperatively. Two of 8 patients with neurological deficits improved postoperatively. There were no cases of instrumentation failure or loss of reduction. The authors concluded that long-segment rigid posterior fixation was an acceptable method for treating patients with AS who sustained subaxial cervical spine fractures.
Einsiedel and colleagues27 described a retrospective review of 37 AS patients with subaxial fractures from 2 institutions over a 16-year period. All patients were treated surgically. Ten patients were treated with anterior standalone instrumentation and fusion. Twenty-four patients were treated with anterior and posterior instrumentation and fusion. Two cases were treated with posterior instrumentation and fusion alone, and 1 patient underwent laminectomy only without fusion. Patients were followed up only until hospital discharge. All patients improved neurologically. Despite the short-term follow-up, 50% of patients treated with anterior instrumentation suffered instrumentation failure. No patient treated with posterior instrumentation experienced instrumentation failure. Three patients died in the early postoperative period. The authors noted a high rate of fractures detected with only computed tomography or MRI in the thoracic and lumbar regions in association with the primary subaxial cervical fractures. From this class III medical evidence, the authors concluded that cervical spinal fractures in patients with AS should be treated with combined anterior and posterior instrumentation and fusion procedures.
In 2008, Kanter and colleagues28 published a series of 13 patients with AS and subaxial cervical fractures. Twelve patients had either posterior standalone instrumentation and fusion or anterior and posterior surgery. Only 1 patient underwent anterior-only instrumentation and fusion. An average of 5.6 segments were instrumented. Five of 13 patients improved neurologically; 1 patient had neurological deterioration. Thirty-eight percent of the patients experienced complications, including instrumentation failure in 2 patients and death in 1 patient. All of the 10 patients available for radiographic follow-up went on to achieve fusion confirmed by computed tomography imaging. The authors offered a complex management algorithm and recommended surgical treatment for all patients with AS and cervical fractures. This study represents Class III medical evidence on this issue.
In 2010, Caron et al29 published a retrospective review of their experience treating patients with AS or diffuse idiopathic skeletal hypertrophy syndrome who had sustained spinal fractures. One hundred twelve patients were identified in their database. Clinical and radiographic follow-up was available for 62 of 84 patients who survived the initial hospitalization with a mean follow-up of 6.5 months. Sixty-seven fractures (55%) were in the cervical spine. The authors did not quantify their results by spinal level. Neurological deterioration occurred in 81% of patients for whom there was a delay in diagnosis (19% of all patients). The reported overall mortality was 32%. Mortality was significantly higher (P = .005) in patients treated nonsurgically, but some of these patients were not treated surgically because of their severe medical comorbidities. Linear regression analysis revealed that age was the primary predictor of mortality in their review. The authors concluded that patients with AS and those with diffuse idiopathic skeletal hypertrophy who sustained traumatic spinal fractures were sufficiently similar to be considered together in terms of treatment and prognosis. Extreme vigilance and the routine use of advanced imaging (computed tomography and MRI) were recommended because of the significant number of patients who presented with a delayed diagnosis and neurological deterioration.
Subaxial cervical spine fractures and dislocations encompass a broad spectrum of acute traumatic injuries. Adequate decompression of the neural elements and the restoration of sufficient spinal stability to allow early mobilization and rehabilitation remain basic treatment tenets. Although nonsurgical treatment can be employed successfully, surgical treatment of these injuries achieves these goals more consistently and more quickly, especially in higher grades of injury. Both anterior and posterior surgical approaches have been reported as effective. Neither approach is necessarily superior to the other as long as the goals of treatment can be accomplished. Treatment must be individualized on the basis of the specific characteristics of each particular injury. Factors to be considered include neurologic status, the degree and type of bony and/or ligamentous disruption, and the degree and cause of spinal cord compression. The treatment of patients with AS who sustain traumatic subaxial cervical spinal fractures is challenging and has a comparatively high associated morbidity and mortality, regardless of the treatment offered or the surgical approach used.
KEY ISSUES FOR FUTURE INVESTIGATION
Subaxial cervical spine injuries are common, can have devastating personal consequences, and represent a significant cost to individuals and society. Research continues to be hampered by lack of an accurate, reproducible, universally accepted classification system. Recent literature continues to suffer from poorly characterized patient populations, inconsistent treatment protocols, and variable outcome measures that make generalizations regarding treatment difficult. Only 2 prospective Class I trials in investigation of these injury types were identified in the present literature review; unfortunately, both provided Class III medical evidence because of inadequate power and other study design or process factors. Future research needs to incorporate more precisely characterized patient groups, more rigorously defined treatment protocols, and generalizable outcome measures obtained by complete, comprehensive follow-up.
The authors have no personal financial or institutional interest in any of the drugs, materials, or devices described in this article.
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Keywords:Copyright © by the Congress of Neurological Surgeons
Ankylosing spondylitis; Anterior and posterior stabilization and fusion procedures; Subaxial cervical fractures