Odontoid fractures are the most common cervical fracture type among the elderly population. Several treatment options exist for these patients, ranging from immobilization with a semirigid orthosis to surgical arthrodesis. This report reviews the key points in the management of odontoid fractures in the aged patient, including diagnosis, the various forms of conservative therapies, and the options for surgical intervention.
Key points
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Odontoid fractures are the most common fracture type among the elderly population.
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Radiographic evaluation of odontoid fractures with plain films, computed tomographic imaging, and MRI plays a major role in treatment decisions.
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An array of conservative measures exists for the management of odontoid fractures ranging from semirigid orthoses to halo immobilization. Each type of brace has its own distinct risks and benefits.
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The 2 primary categories of surgical intervention for odontoid fractures are ventral odontoid screw fixation and posterior atlantoaxial arthrodesis. Fusion rates for both procedures are excellent in most patients, but pitfalls exist with both operative approaches that must be considered when selecting patients for these operations.
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There is a strong need for further high-quality research into optimal management of odontoid fractures in the elderly, a need that will only increase as the population ages worldwide.
Introduction
Nearly 20% of cervical fractures involve the odontoid process. This fracture pattern most often results from a forced hyperflexion or hyperextension mechanism. The elderly are especially vulnerable to this injury pattern and frequently present with odontoid injury after ground-level falls with associated hyperextension. The optimal management strategy for odontoid fractures remains controversial, especially in the elderly, because of the high morbidity and mortality with both conservative and operative intervention. As the population ages, the landscape of spinal surgery is poised to shift dramatically, and the treatment of these patients becomes an increasingly common problem among practitioners treating spinal conditions. This review discusses the management of odontoid fractures among the elderly, with a focus on the various treatment options and their outcomes.
Introduction
Nearly 20% of cervical fractures involve the odontoid process. This fracture pattern most often results from a forced hyperflexion or hyperextension mechanism. The elderly are especially vulnerable to this injury pattern and frequently present with odontoid injury after ground-level falls with associated hyperextension. The optimal management strategy for odontoid fractures remains controversial, especially in the elderly, because of the high morbidity and mortality with both conservative and operative intervention. As the population ages, the landscape of spinal surgery is poised to shift dramatically, and the treatment of these patients becomes an increasingly common problem among practitioners treating spinal conditions. This review discusses the management of odontoid fractures among the elderly, with a focus on the various treatment options and their outcomes.
Patient evaluation
The definition of the elderly patient is not widely agreed on, and, as in other patient populations, there is significant heterogeneity among patients of this age group. Among patients who are older than 70 years, however, odontoid fractures comprise the most common cervical spine facture and in those older than 80 years the most common overall spine fracture. Evaluation of patients in whom odontoid fracture is suspected consists of radiographic studies in addition to clinical evaluation. These studies can aid in definition of the fracture and in the decision on how to manage the injury.
Radiographic Evaluation
Anderson and D’Alonzo defined 3 types of dens fractures based on radiographic fracture pattern. Fractures involving only the tip of the odontoid are characterized as type I, those through the base as type II, and those that extend into the vertebral body as type III ( Fig. 1 ). Although most type III and almost all type I fractures eventually fuse with conservative management in a cervical collar, nonunion rates for type II injuries are significantly higher.
The initial diagnostic evaluation of traumatic cervical spine injuries often includes plain radiographs, usually consisting of an anterior–posterior projection, a lateral projection, and an open-mouth view for visualization of the odontoid. In cases in which a fracture is identified on plain radiographs, and in those in which the index of suspicion is high, radiographs are generally followed by computerized tomography (CT). CT allows for both a confirmation of the presence of a fracture and improved definition of fracture morphology for use in subsequent management decisions. Indeed, the effectiveness of CT for cervical spine trauma, combined with its ubiquity in modern practice, led some to question the need for plain radiographs in this patient population.
The role of MRI in odontoid fractures remains an area of debate. Although ligamentous injury, specifically of the transverse atlantal ligament, may be missed on plain radiographs and CT, the incidence of this seems to be low—between 0% and 10%. Despite the rarity of this injury, the integrity of the transverse ligament is an important consideration in the treatment algorithm. Although well-aligned bony fractures may heal with orthosis, ligamentous injury in addition to the fracture has a significantly lower healing rate. Additionally, if the prospect of operative intervention is entertained, odontoid screw fixation would not be appropriate in the setting of ligamentous injury. Complicating decisions about the use of MRI in the elderly are that MRI findings may also be difficult to interpret in this population because of their bone composition and misinterpretation can lead to misdiagnosis.
Risk Factors for Odontoid Fracture
The predilection for odontoid fractures in the elderly is believed to be secondary to progressive degenerative changes in the cervical spine as individuals age. As these changes occur, motion in the subaxial cervical spine decreases, leaving the C1-2 segment as the most mobile portion of the neck. One recent study suggests that elderly individuals with severe osteoporosis and with significant degeneration of the atlanto-odontoid joint combined with a smoothened lateral atlantoaxial joint may be at higher risk for type II odontoid fractures after trauma. A vascular mechanism has been implicated as well, with a watershed area at the base of the dens that is more pronounced in the elderly, contributing to fracture risk.
Premorbid clinical risk factors for odontoid fractures after trauma in the elderly population have not been well studied, although variables ranging from the location of the fall to racial/ethnic disparities have been investigated in the general trauma literature. As is the case with other traumatic injuries, worse premorbid health seems to be associated with increased morbidity and mortality in odontoid fractures regardless of management strategy, as is the presence of neurologic deficit.
Conservative management
Conservative management for odontoid fractures most commonly consists of rigid external fixation—with either a hard cervical collar or halo immobilization. These options are sometimes chosen in the elderly because of concerns for operative morbidity in this fragile population. This risk must be counterbalanced with the higher rates of nonunion with external immobilization alone.
Orthotic Types
A variety of braces are currently marketed for the management of cervical injury, falling into 4 broad categories as defined by Johnson and colleagues. The least restrictive cervical collar is the so-called soft collar. Although comfortable and economical, soft collars provide little in the way of motion limitation and, therefore, play little role in the management of odontoid fractures. The second category is the semirigid orthosis, generally comprising 2 interlocking polymer segments; this category includes the Aspen ( Fig. 2 ) and Miami-J collars. These collars provide significantly more motion limitation—especially of rotational movement—compared with soft collars, at the cost of a lower degree of comfort. The Minerva brace includes a thoracic element to the construct and commonly incorporates a posterior occipital bolster with a mandibular brace, providing further limitation of flexion and extension. The most restrictive external orthotic solution is the halo vest. Although offering the maximal movement limitation in all planes—flexion/extension, rotation, and lateral bending —the halo requires physician expertise for application. The use of pins for halo vest fixation also necessitates the use of local anesthetic and can lead to various complications, including infection, nerve injury, and even fractures and durotomy.
Outcomes and Complications
There remains a significant lack of high-quality evidence in the literature with regard to outcomes after conservative management of odontoid fractures in the elderly, with most studies on the topic consisting of small case series. Interpretation of the results is hampered by the use of a variety of brace types between and even within individual studies.
Rates of bony fusion with external immobilization and type II fractures vary depending on the study from as low as 23% to as high as 82%. Although osseous fusion has classically been the standard of success in the healing of odontoid fractures, a body of literature exists suggesting that in asymptomatic patients who are stable on flexion/extension imaging, so-called fibrous union should also be considered an acceptable outcome.
As described previously, the halo brace provides the most rigid external construct available, and historically many practitioners have advocated its use as the first-line treatment for elderly patients with odontoid fractures. Fusion rates with halo fixation can reach as high as 90%, although significant variability exists because of the heterogeneity of the literature. Despite the rigidity offered by the halo, significant attention was paid in the last decade to the high rate of complications associated with their use in the elderly. Morbidity—primarily consisting of pneumonias—was reported in up to 52% of this patient population with halo vest immobilization. Mortality rates are often similarly high, leading one author to deem the halo a “death sentence” for older patients with cervical fractures. Despite these concerns, in carefully chosen cases, many surgeons continue to have high rates of success with halo fixation.
Concerns over the use of halo fixation led some to use semirigid braces and cervicothoracic bracing systems such as the Minerva brace to treat patients with dens fractures. Sime and colleagues recently did a meta-analysis of 13 studies examining differences in outcomes and complication rates between these alternative systems and the halo. With regard to achieving stability—defined as osseous fusion or fibrous nonunion without motion on flexion/extension films—patients placed in halos had a success rate of 84%, whereas those in semirigid orthoses had a success rate of 63%, and those placed in Minerva braces had a success rate of 65%. Halo patients had an overall mortality rate of 25%, whereas those in semirigid orthoses had a mortality rate of 28%, and those with Minerva braces had a mortality rate of 25%. None of these differences, however, reached statistical significance. These findings were supported by a recent combined prospective/retrospective analysis of halo fixation versus semirigid orthoses by Patel and colleagues that also found no significant difference in outcomes, although the authors noted that bony union was more common with the halo.
Although conservative measures may sometimes be the treatment option of choice for patients and their families, care must be taken to avoid neurologic catastrophe. Close follow-up including surveillance radiography is necessary, as symptoms of progressive myelopathy were reported to develop years after the initial injury.
Surgical intervention
There are many indications for surgical intervention in odontoid fractures, including instability, symptomatology, and psychosocial variables, all of which must be carefully weighed with the risks of surgery itself and tailored to the individual patient. Symptoms in these patients can range from neck pain to radicular symptoms to myelopathy and may worsen with time or with subsequent trauma. There is evidence that surgical intervention may reduce mortality among elderly patients with odontoid fractures compared with conservative management and that the elderly may be at particular risk for failure of osseous healing with bracing alone. There is also evidence that quality-of-life outcomes for elderly patients with nonoperative treatment are worse than those of patients who receive surgery.
Surgical intervention for odontoid fractures can be broadly divided into 2 categories: dorsal fixation, consisting of a variety of atlantoaxial constructs, and ventral fixation, with the placement of a direct odontoid screw.
Ventral Fixation
Initially reported by Nakanishi in 1980, direct screw fixation of the odontoid process was first described in the English-language literature by Böhler. With proper technique, the procedure allows for stabilization of the fracture with minimal soft tissue disruption and maintenance of rotation at the atlantoaxial joint, all while avoiding the need for autograft or allograft ( Fig. 3 ). Rates of fusion in patients undergoing odontoid screw fixation are high, with a rate of 88% in the series of 147 cases by Apfelbaum and colleagues. Complications of odontoid screw fixation in elderly patients most commonly consist of pneumonia and dysphagia, although more serious complications such as intraoperative hardware failure and mortality have been reported.
Related posts:
Update on New Imaging Techniques for Trauma
Thoracolumbar Trauma Classification
Classification and Management of Pediatric Craniocervical Injuries
Classification and Management of Pediatric Subaxial Cervical Spine Injuries
Pediatric Thoracolumbar Spine Trauma
Complications in the Management of Patients with Spine Trauma
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