Odontoid Fracture in the Elderly: Odontoid Screws Versus Posterior Fusion

Type II odontoid fracture is the most common cervical spine fracture in the elderly, and the incidence of this injury is increasing. The odontoid peg is central to the stability of the upper cervical spine—the posterior ring of C1 articulates with the anterior odontoid process, and axial rotation at this joint accounts for approximately 60 degrees of rotation. Stability is afforded via ligamentous constraint: The transverse ligament inserts posteriorly on the odontoid, preventing anterior-posterior translation of C1 relative to C2. Consequently, a fracture of the odontoid process may allow the translation of the occiput-C1-odontoid complex relative to the body of C2.

The management of type II odontoid fractures in the elderly is controversial for several reasons. Odontoid fractures in the elderly are associated with significant morbidity, irrespective of the type of management chosen. In the octogenarian population acute inpatient mortality may exceed 10%, regardless of management option. There is consensus that in the elderly patient with a displaced fracture the most likely outcome of nonoperative management (either with cervical orthosis or halothoracic vest bracing) is a nonunion. In addition, there is growing consensus that in elderly patients halothoracic vest immobilization is associated with significant morbidity.

Nonoperative treatment of a displaced type II odontoid fracture is associated with a nonunion rate that approaches 80% in the elderly. An unstable nonunion has an associated risk of catastrophic neurologic injury with subsequent falls, as well as a well-documented risk of late-onset progressive myelopathy. The goal of surgical management is to restore stability to the upper cervical spine, either through direct osseous union of the odontoid fracture or through posterior fusion of the ring of C1 to the posterior elements of C2.

Case Presentation

An 82-year-old woman fell from standing and came to a regional level I trauma spinal cord injury referral center.

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PMH: Unremarkable
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PSH: Unremarkable
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Exam: The patient was neurologically intact, with normal reflexes. Head trauma was present with ecchymosis and a scalp hematoma over the right occiput. There was no tenderness to palpation along the posterior spinal elements.
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Imaging: Initial anteroposterior (AP), lateral, and open-mouth odontoid images demonstrated a type II odontoid fracture. AP and lateral radiographs of the thoracic and lumbar spine were negative for fracture. Due to the displaced odontoid fracture, a computed tomography (CT) scan of the cervical spine, as well as a magnetic resonance imaging (MRI) scan of the cervical spine with magnetic resonance angiography, were obtained. The CT scan ( Figure 11-1 ) demonstrated a posteriorly displaced odontoid fracture with comminution at the fracture site.

FIGURE 11-1

Sagittally reconstructed CT scan ( A ) demonstrates a posteriorly displaced type II odontoid fracture with fracture comminution. The axial ( B ) and coronal ( C ) images illustrate the posterior translation of the C1-odontoid complex relative to the body of C2.

Surgical Options

The surgical management options for a type II odontoid fracture can be divided into two subsets: anterior approach and fixation with the goal of direct osteosynthesis, and posterior approach and fusion of the C1-C2 complex.

Anterior Odontoid Screw

Direct union of an odontoid fracture through placement of anterior odontoid screws is attractive mainly because it avoids the morbidity of the posterior approach and maintains axial rotation of the C1-C2 articulation. Apfelbaum and colleagues reported on a large cohort of 147 patients who underwent anterior screw fixation and demonstrated it to be an effective technique irrespective of age, but they found that outcomes were worse for fractures with an anterior-oblique orientation and for fractures treated longer than 18 months after injury. To achieve direct osteosynthesis, however, one must obtain a complete reduction of the fracture or be able to achieve reduction of the fracture in the operating room. Similar results have been found with single- and multiple-screw fixaion. A partially threaded screw should be used (or the proximal fragment overdrilled by 1 mm), and the threads must be advanced completely across the fracture site. In addition, the transverse ligament must be carefully assessed for injury, because injury to this ligament is a contraindication to anterior odontoid screw fixation. Direct repair of the fracture will not restore C1-C2 stability in the setting of an incompetent ligament.

The presence of osteoporosis raises concern for increased risk of instrumentation failure with anterior fixation, as reported by Andersson and associates. However, Borm and co-workers reported on a cohort of elderly patients treated successfully with anterior odontoid fixation, and Harrop and colleagues found that age per se was not a contraindication, but that the presence of osteoporosis carries a risk of instrumentation failure. Direct comparison between outcomes for anterior odontoid screw fixation and posterior C1-C2 fusion in a retrospective review involving an elderly cohort suggested better overall results with the posterior procedure when fusion rate and rate of reoperation were considered. A retrospective study of data for a cohort of elderly patients who underwent surgery for acute type II odontoid fractures found a significantly higher incidence of postoperative pneumonia, dysphagia, and vocal cord problems in the patients undergoing anterior screw fixation (compared with those treated using various posterior techniques). In patients with good bone quality and appropriate fracture orientation, anterior odontoid screw fixation has been demonstrated to be associated with a fusion rate of approximately 90%, but the use of the technique in the elderly and/or patients with osteoporosis remains controversial.

Posterior C1-C2 Fusion

Posterior C1-C2 fusion may be achieved via posterior wiring and bone grafting (Brooks or Gallie technique), placement of posterior C1-C2 transarticular screws (Magerl ), posterior C1 lateral mass–C2 pars instrumentation and fusion (popularized by Harms and Melcher ), and placement of posterior C1 lateral mass–C2 laminar screws. The use of transarticular screws and C1 lateral mass–C2 pars/laminar screws has largely supplanted sublaminar wiring. Advantages of a posterior fusion procedure include the ability to restore stability in the setting of transverse ligament injury as well as in the setting of an irreducible fracture. With the increasing biomechanical stability afforded by later-generation posterior constructs there has been a concomitant decrease in the use of postoperative halo vest immobilization. Relative risks of a posterior C1-C2 procedure are the morbidity of the posterior approach, risk of brisk bleeding from the venous plexus, risk of injury to the vertebral artery, as well as risk of injury to the carotid artery or esophagus with anterior perforation of a C1 lateral mass screw.

The patient described in the Case Presentation is an octogenarian who incurred her injury in a fall from standing. As with most such fractures, the patient is neurologically intact. The fracture is posteriorly displaced and angulated. Because posterior displacement and patient age are significant risk factors for nonunion, the options in this case are to provide surgical management or to accept a likely nonunion with use of a cervical orthosis. Preoperative reduction of such a fracture has been demonstrated to be associated with significant risk of airway compromise. In addition, if the surgeon is unable to achieve an anatomic reduction in the operating room, any planned anterior procedure would need to be aborted and changed to a posterior procedure.

The long-term morbidity of a nonunion is unclear. Some literature contends that a fibrous nonunion may be an acceptable outcome, and this may be the case in an elderly patient with significant comorbid medical conditions that result in a predominantly sedentary lifestyle. However, for an independent, active elderly patient, a nonunion likely portends worse outcomes. A displaced fracture that has not healed leaves the upper cervical spine at significant risk in the event of a subsequent fall. Furthermore, although the incidence of late-onset myelopathy is not established, the report by Crockard and colleagues suggests that it is in the setting of a displaced fracture with subsequent nonunion that late-onset myelopathy is most likely to occur. Interestingly, Crockard’s group found that in the cohort with nonunion the transverse ligament was frequently interposed in the fracture site. Consequently, for an active elderly patient such as the one described in the Case Presentation, surgical management is a reasonable option. Which option is the best for any given patient is a complex question and ultimately must be decided by the patient and physician based on patient-specific factors.

If surgical management is undertaken in the patient in the Case Presentation, a posterior C1-C2 fusion may be more desirable than anterior fixation for a number of reasons. The fracture in this patient is displaced, which precludes anterior fixation without prior reduction. As noted earlier, closed reduction of displaced odontoid fractures in the elderly has been demonstrated to be associated with risk of airway compromise, and so any preoperative closed reduction procedure probably carries more inherent risk than it would in a younger patient. Closed reduction in the operating room is possible, but if reduction cannot be achieved, the anterior procedure would need to be aborted. There is a lack of consensus regarding the role of anterior screw fixation in the elderly with respect to the quality of the bone. One large single-center retrospective cohort study reviewed results for 75 acute type II odontoid fractures that were managed surgically and found a statistically significant increase in the rate of airway problems and dysphagia in patients who underwent anterior screw fixation compared with those treated using other techniques. Several reports have suggested that in osteoporotic patients anterior screw fixation may result in suboptimal outcomes due in part to fracture site comminution, as well as the risk of nonunion with subsequent failure of the hardware, and the rate of nonunion is higher in elderly than in younger patients. Anterior screw fixation has not been demonstrated to be superior to posterior C1-C2 instrumentation, and given the conflicting data on the efficacy of the procedure in the elderly, a posterior procedure may provide more consistent results in achieving fusion and stability, which is the ultimate goal of surgical management.

Due to the displacement type of fracture, the patient’s age, and the history of osteoporosis, the patient underwent a posterior C1-C2 fusion with lateral mass instrumentation and placement of C2 pars screws, with patellar allograft bone used as the graft source, secured in place with No. 5 fiber wire (modified Gallie technique) ( Figure 11-2 ). The patient was extubated on postoperative day 1 and progressed well enough to be transferred to a skilled nursing facility on postoperative day 5. At the time of 6-month follow-up the patient had returned to living independently with her spouse.

Fundamental Technique

Surgical planning, positioning of the patient, and use of intraoperative fluoroscopy are procedural variables that are under the control of the surgeon, and proper attention to these details is essential ( Tips from the Masters 11-1 ).

Tips from the Masters 11-1

Careful preoperative planning using CT reconstructions is essential. The C2 isthmus and foramen must be scrutinized to confirm that the morphology is appropriate for use of a C2 screw, and a thorough understanding of the anatomy is mandatory before surgical intervention is undertaken.

Preoperatively the vertebral artery should be visualized on MRI scan and the foramen identified on CT images of C1 and C2, with careful attention paid to the diameter of the C2 pars. A high-riding foramen in C2 may preclude the safe placement of a pars screw on that side or necessitate use of a shorter screw.

The patient should be positioned prone on chest rolls in Mayfield tongs in reverse Trendelenburg position of sufficient angle to make the cervical spine at least parallel with the floor of the operating room; this will facilitate operative visualization and minimize blood loss. To facilitate fluoroscopy the table may need to be reversed with the patient’s head at the opposite end of the table from the anesthesia team, so the anesthesia team should be prepared accordingly for management of the endotracheal tube and intravenous lines.

Surgical dissection should be carried subperiosteally along the posterior elements of C2 and C1. Great care should be taken to maintain the initial midline dissection of the lamina of C1 within 15 mm of midline and along the posterior inferior margin. This will minimize the chance of injury to the vertebral artery as it traverses dorsally along the superior aspect of the posterior arch of C1. The lamina of C2 should be exposed, and the C2 isthmus clearly identified. It is recommended that at this point a Penfield 4 dissector be placed along each side of the C2 isthmus and that lateral fluoroscopic images be obtained. The fluoroscope should be adjusted until the images of the Penfield dissectors are superimposed: this will help to avoid parallax and optimize accurate visualization of the anatomy ( Tips from the Masters 11-2 ).

Tips from the Masters 11-2

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