As the population ages, fractures of the odontoid process of C2 have become increasingly prevalent.1 Odontoid fractures comprise up to 15% of all cervical fractures in nonpediatric patients and are typically associated with flexion–distraction injuries with a high incidence of associated morbidity.2 Indeed, for the geriatric population, dens fractures comprise the majority of all cervical fractures in patients older than 80 years and remain the most common cervical fracture pattern in all patients older than 65 years.3
Particularly in geriatric patients, poor bone quality, altered regional biomechanics, and poor blood supply to the base of the odontoid predispose these patients to nonhealing. Much of the morbidity associated with type II odontoid fractures has traditionally been thought to be due to the risk of nonhealing and ensuing instability and neurologic injury. A mobile dens unit may potentially lead to atlantoaxial instability, with subsequent compression of the neural elements and brainstem, and ultimate myelopathic degeneration.4 However, because the historical literature on these patients often only reported failure of treatment as the development of a neurologic injury or significant atlantoaxial instability, previous literature emphasized that successful osteosynthesis of odontoid fractures did not necessarily correlate with successful clinical outcomes in geriatric patients; this rudimentary analysis allowed many authors to advocate for nonoperative treatment of these fractures.5–8 More recently, high-level studies have demonstrated the severity of these fractures, with Vaccaro et al9 publishing a prospective study finding an 18% 1-year mortality rate in geriatric patients with an odontoid fracture. Furthermore, multiple contemporary studies have demonstrated a significant decrease in mortality rates in geriatric patients treated surgically compared with those treated nonsurgically,9–11 and an improvement in health-related quality of life (HRQOL) outcomes in patients treated surgically. The purpose of this review was therefore to discuss and address the ideal treatment for geriatric patients with type II odontoid fractures, based on current evidence.
IMAGING AND CLASSIFICATION
Most geriatric patients with these injuries present after falls from standing or similar low-energy trauma; classically, suspected cervical spine trauma should be evaluated upon presentation with anteroposterior, lateral, and open-mouth odontoid view plain radiographs. However, plain radiographs alone only detect about 80% of traumatic cervical spine injures, and this is largely due to poor visualization of upper cervical spine and the cervicothoracic junction.12 Consequently, computed tomography is now the preferred imaging modality in many trauma centers upon presentation to evaluate for suspected cervical spine trauma. Computed tomography imaging has been reported to have a sensitivity approaching 100% in detecting upper cervical spine fractures, and it is actually substantially less expensive than plain radiography in many centers.13,14 Furthermore, associated injuries can have a major impact on the determination of treatment, and a complete scan permits in-depth evaluation of the entire cervical spine.15
The most widely used classification scheme was proposed in 1974 by Anderson and D'Alonzo16 (Fig. 1), and it organizes fracture patterns based on the anatomic location of the fracture. Fractures of the tip of the dens secondary to avulsion of the alar ligaments are classified as type I fractures. Type II fractures are fractures that extend through the base of the odontoid, whereas type III fractures involve the body of the axis.16 However, Grauer et al17 proposed a modification to this classification that redefined type III fractures as those that extend into the superior articular facet of C2, rather than simply the vertebral body, as some type II fractures may extend into the body but continue to have poor healing potential. Management of type I and type III fractures are considerably less controversial than for type II fractures: in the absence of occipito-atlantal or atlantoaxial instability, or other concomitant unstable cervical fractures, the recommended management of type I fractures is immobilization in a hard cervical collar.18 For type III fractures, in the absence of significant displacement or distraction through the fracture site, either a halo vest or hard cervical collar may be used, as fusion rates seem to be similar between these 2 treatments.19 For type II geriatric odontoid fractures, however, historic literature has not provided a clear consensus on optimal treatment, whereas more recent literature shows a clear decrease in mortality rates and an increase in HRQOL outcome metrics with surgical intervention.9–11
TYPE II GERIATRIC ODONTOID FRACTURES
Type II fractures are under substantial tension from the apical ligament and frequently involve osteoporotic cortical bone without significant cancellous surface area, and thus, the healing potential of these fractures is limited.20 In addition, the periosteal blood supply to the area is decreased due to the myriad of synovial cavities that surround the base of the dens. Due to the aforementioned problems with these fractures, the nonhealing rate has been reported as high as 85% in patients treated nonoperatively.21 Historically, the benefits of surgical intervention have been extensively debated in the literature, particularly in geriatric patients with individual factors and comorbidities that may require consideration before any attempt at surgical management. However, more current, high-quality studies have shown substantial benefit in support of surgical intervention.9–11
Management of Acute Type II Geriatric Odontoid Fractures
Operative Versus Nonoperative Treatment
Upon presentation of a type II geriatric odontoid fracture, the fracture morphology must be assessed, and degrees of comminution, angulation, and displacement can all affect potential for healing. Patient's health considerations, such as osteoporosis or altered bone mineral density, previous dysphagia or dysphonia, and cardiopulmonary comorbidities, are also important to consider. Evaniew et al22 examined the mortality outcomes in patients with acute odontoid fractures and found that evidence of atlantoaxial instability was associated with an increased risk of nonunion and mortality. Traditional immobilization for these fractures include application of a halo vest; however, multiple studies have since found that elderly patients immobilized in this fashion have high rates of failure to thrive and respiratory complications, as well as inadequate immobilization despite correct application of the vest23,24; Bednar et al25 reported that the mortality rate for geriatric patients with type II odontoid fractures treated in a halo was 42%. Importantly, the morbidity of nonoperative treatment has not only been found in patients treated with a halo vest. Muller et al26 reported on 18 patients with geriatric odontoid fractures treated nonoperatively (15 in hard collar and 3 in a halo), and they found a mortality rate of 33%, and more than 50% of the patients were found to have a major complication from treatment.
Over the last decade, multiple high-quality studies have been published demonstrating clear superiority for surgical treatment in geriatric patients with type II odontoid fractures. Chapman et al10 published the retrospective results of 322 patients older than 65 years who sustained a type II odontoid fracture. The authors found that overall mortality rate at 30 days postinjury was 14%, but the short-term mortality was significantly lower in the operatively managed group when compared with the nonoperative population (7% vs. 22%, P < 0.0001).10 They also examined the long-term outcomes of these patients, with an average follow-up of greater than 2 years. The overall mortality was 44%, with significantly more patients expiring in the nonoperative group (51% vs. 38%, P = 0.016).10 Regression analysis controlling for age, sex, and comorbidities found that the hazard ratio for mortality at final follow-up was 1.35 for patients treated nonoperatively (P = 0.079).10 Similarly, in a subgroup analysis of a prospective multicenter study, Smith et al27 found that 22% of geriatric patients with a type II odontoid fracture who were managed nonoperatively eventually required delayed surgical intervention. Furthermore, Vaccaro et al9 published the only large, prospective multicenter observational study of patients older than 65 years who were diagnosed with a type II odontoid fracture, and the study looked not only at mortality but also at the HRQOL outcome metrics. The authors reported significantly improved Neck Disability Index scores (P < 0.0001) and the physical component of the short-form-36 (P = 0.01) in patients treated operatively.9 Additionally, they found no difference in complication rates of patients treated surgically versus conservatively, but there was a strong trend toward a decrease in mortality with operative intervention: 26% versus 14% (P = 0.06).9 Finally, in a recent systematic review examining operative and nonoperative interventions for type II geriatric odontoid fractures, Schroeder et al11 found a significant decrease in the short-term mortality [odds ratio, 0.43; 95% confidence interval (CI), 0.30–0.63] and long-term mortality (odds ratio, 0.47; 95% CI, 0.34–0.64) rates in patients treated operatively. This review included 21 published articles examining 1233 patients and limited their review to studies performed after the year 2000.11 Similar to the Vaccaro study, the complication rate was not higher in patients treated surgically (odds ratio, 1.01; 95% CI, 0.63–1.63).11 The authors concluded that patients undergoing surgical treatment for geriatric type II odontoid fractures have a decreased risk of mortality, both in the short- and long-term, without an associated increase in complications.11 In addition to demonstrating improved mortality rates and HRQOL outcome metrics, Barlow et al28 found that surgical treatment of type II geriatric odontoid fracture in patients aged 65–84 years was more cost-effective than nonoperative treatment. When using $100,000/quality-adjusted life year (QALY) as a benchmark, surgery is cost-effective in patients younger than 84 years.28
Importantly, there may be a difference in the ideal treatment between older and younger geriatric patients, although there has not been a consensus on the effect of extreme patient age in the literature. In a prospective study, Fehlings et al29 reported that treatment failure (defined as death by any cause, worsening in the Neck Disability Index score by more than 9.5 absolute points, or occurrence of a major treatment-related complication) was more common in older patients, male sex, and patients initially treated nonoperatively. Another case series of 5 patients found that asymptomatic patients older than 80 years with type II odontoid fractures may have good functional outcomes with nonoperative care, and if the patients fail a trial of nonoperative management, conversion to surgical stabilization after initial treatment failure did not affect outcome.30 However, this series is limited by its very small number of included patients, and generalizable outcomes may be not applicable.
Most spine trauma surgeons generally agree that odontoid fractures can be approached either anteriorly or posteriorly. Anterior surgery involves odontoid screw fixation, with the goal of surgery to be effective osteosynthesis of the fracture site alone. Posterior surgery includes C1–C2 arthrodesis with posterior instrumentation. Anterior screw fixation has been advocated in the literature,31 including 2-screw lag fixation to maximize purchase in osteoporotic bone32; however, the addition of a second screw has not been shown to significantly affect union rates.33 Several mechanisms of failure for isolated anterior screw fixation have been identified. In a retrospective review of 33 patients older than 65 years treated with anterior odontoid screw fixation, Osti et al34 identified several factors that predisposed to loss of correction or nonunion. These factors included “degenerative changes in the atlanto-odontoid joint, severity of osteoporosis in the odontoid process, posterior oblique fracture type (fracture line going from anterior inferior to posterior superior), suboptimal fracture reduction, suboptimal position of the screw implant, quality of fracture compression, and severity of fracture comminution.”34 Another study found that the anterior approach may have a greater effect on patient morbidity as a result of complications related to implant fixation.29 In contrast, however, the systematic review by Schroeder et al11 found that there were no significant differences in short- or long-term mortality, or in overall complication rates, between anterior and posterior surgical approaches and included 6 studies examining posterior cervical fusion and 9 studies examining anterior odontoid screw placement. Overall, most authors suggest that given the limitations of the anterior odontoid approach, it should primarily be considered in younger patients with good bone quality, amenable fracture obliquity, and appropriate body habitus.
Posterior C1–C2 fusion is the most commonly performed operation for type II odontoid fractures. Several techniques to achieve arthrodesis have been described, including C1–C2 transarticular screws, sublaminar wiring (in patients with aberrant vascular anatomy that precludes screw fixation), and polyaxial screw placement in the atlas and the axis with rod connection. For transarticular screws, the screw should enter the C2 lateral mass, cross the C1–C2 joint, and terminate in the lateral mass of C1.35 The starting point is described as just cephalad to the C2–C3 facet capsule, necessitating a very steep trajectory. As such, percutaneous starting points, oftentimes below the cervical spine at the level of T1, must be used in conjunction with open placement of bone graft over C1–C2 posterior elements. Additionally, fixation in C1 can be achieved by polyaxial lateral mass screws, and C2 can be stabilized by polyaxial pedicle or pars screws. Yet another alternative technique, using a laminar claw hook–rod system as an alternative to traditional posterior cervical screws, has been described: in a retrospective review of a series of 167 consecutive odontoid fractures, Maciejczak et al36 found similar fusion and complication rates between this technique and traditional screw–rod constructs, with a theoretical advantage of less risk of vertebral artery injury and less procedural difficulty in the hook group. However, this technique has not been widely adopted.
AUTHORS' PREFERRED TREATMENT
In light of the available evidence, it is the author's preferred treatment to surgically manage geriatric patients with type II odontoid fractures with a C1 lateral mass and a C2 pars screw construct (Fig. 2).
Despite the commonality with which type II geriatric odontoid fractures occur, a consensus for optimal treatment has historically remained lacking in the literature. Both nonoperative and operative management are associated with high mortality rates and decreased functional status. Previous literature had suggested that fixation or arthrodesis in the setting of an acute type II odontoid fracture was equivalent to nonoperative management, but more recent high-quality literature has found that surgery provides an efficacious option for geriatric patients with these fractures. Improvements in short- and long-term mortality have been demonstrated, and significant improvements in functional status after surgery (without increased complication rates) suggest that for patients sustaining these fractures who are able to undergo general anesthesia, the benefits of surgery outweigh the associated risks.
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