The Treatment of Displaced Type II Odontoid Fractures in Elderly Patients

 Hossein Elgafy * ,Marcel F. Dvorak **, Alexander R Vaccaro ***, Nabiel Ebraheim#

* Assistant Professor, University of Toledo Medical Center
** Associate Professor, University of British Columbia
*** Professor, Thomas Jefferrson University and the Rothman Institue
# Professor, University of Toledo Medical Center

Address for Correspondence:  

Hossein Elgafy
University of Toledo Medical Centre
Department of Orthopaedics 
3065 Arlington Avenue
Toledo, Ohio 43614-5807
Tel: 4193833515
Fax: 4193833526
E-mail: helgafy@u.washington.edu

Abstract:

Odontoid fractures are the most common cervical spine fractures for patients aged >70 years and are the most common of all spinal fractures for patients aged >80 years. Type II fracture is the most common type of odontoid fracture and considered relatively unstable. It occurs at the base of the odontoid, between the level of the transverse ligament and the C2 vertebral body. In geriatric population, is important to look for any associated clinical comorbidities that may affect management.  Treatment options for displaced odontoid fractures can be conservative or surgical. Conservative management includes immobilization in a cervical collar or halo vest. External immobilization with a cervical collar has led to inconsistent results. Halo vest immobilization in elderly is associated with a significant nonunion rate and several complications. Well agreed upon surgical indications are the poly-trauma patient, the presence of a neurologic deficit, an associated unstable subaxial spine injuries that requires surgical fixation and a symptomatic nonunion. Surgical management includes either anterior odontoid screw fixation or posterior C1-2 instrumentation and fusion.

J.Orthopaedics 2008;5(1)e17

 Epidemiology:

Odontoid fractures represent 9% to 15% of adult cervical spine fractures.1–3 They commonly occur as a result of low-energy impacts such as falls in the elderly.4, 5 Odontoid fractures are the most common cervical spine fractures for patients aged >70 years and are the most common of all spinal fractures for patients aged >80 years.6 There are equal male-to-female distributions in both populations. The frequency of associated neurologic injury is variable among multiple studies, ranging from 2% to 27%.7, 8, 9 However, when present, it is usually catastrophic because of the high level of spinal cord injury. Odontoid fracture combined with subaxial cervical spine injury is uncommon and rarely reported in the literature. Misdiagnosis or inappropriate management of such combined injuries may result in further neurologic deficit or late spinal instability. The mechanism of odontoid fracture can be either hyperextension that often results into posterior displacement of the odontoid or hyperflexion that often results in anterior displacement.

It is difficult to explain the reasons for the increased incidence of odontoid fractures in elderly compared to younger age groups. This may reflect the propensity for accidental falling in the elderly and its associated mechanism of trauma. Lakshmanan et al,10 suggested an explanation for such increased incidence based on their study of CT-scan images of the cervical spine in 23 patients who were over the age of 70 years and had odontoid fractures. In each patient, the type of odontoid fracture and the characteristics of the degenerative changes in each joint were analysed. Twenty-one of 23 patients had Type-II odontoid fractures. The incidence of significant atlanto-odontoid degeneration in these individuals was very high (90.48%), with relative sparing of the lateral atlantoaxial joints. Osteoporosis was found in 13 of 23 patients at the dens-body junction and in seven of 23 patients involving the odontoid body. With ageing, progressively more advanced degenerative changes develop in the atlanto-odontoid joint. These eventually may, in some people, obliterate the joint space and fix the odontoid to the anterior arch of the atlas. In contrast, the lateral atlantoaxial joints are hardly affected by osteoarthritis. Thus, atlantoaxial movements including atlantoaxial rotation are markedly limited by osteoarthritis of the atlanto-odontoid joint. However, there is still potential for movement in the lateral atlantoaxial joints, as they remain relatively free of degenerative change. The vulnerability of the atlantoaxial segment is further increased by markedly limited rotation below the axis vertebra due to advanced facet-joint degeneration. As a consequence, a relatively low-energy trauma to the lateral part of the face, for instance by a fall, will induce forced atlantoaxial rotation. This, with the marked limitation of movement at the atlanto-odontoid joint, will produce a torque force at the base of the odontoid process potentially leading to a Type II fracture.

Classification:

In the 1970s Anderson and D’Alonzo,11 proposed the most widely used classification system for odontoid fractures. Type I fracture is infrequent and occurs near the tip of the odontoid process, above the transverse ligament. It occurs by avulsion of the apical and/or alar ligaments and it considered relatively stable. However, this fracture type also may be associated with an unstable occipital-cervical dislocation that can result from bilateral avulsion of the alar ligaments or a contralateral occipital condyle fracture. Type II fracture is the most common type of odontoid fracture and considered relatively unstable. It occurs at the base of the odontoid, between the level of the transverse ligament and the C2 vertebral body. Type III fracture extends into the vertebral body and are relatively stable.

Anderson and D’Alonzo,11 suggested treatment algorithms based on the relative stability of each fracture type. Type I and type III fractures are usually treated conservatively with external immobilization either in a collar or a halo vest. However, there is ongoing debate on the best way to manage type II fractures; options include cervical collar, halo vest, anterior odontoid screw fixation or C1-2 posterior instrumentation and fusion. 1, 2, 3, 11, 12, 13, 14, 15, 16

It is often difficult to differentiate between type II and type III fractures. Grauer et al,17 have suggested a more precise definition to differentiate type II from type III fractures. Type II fractures were defined as fractures located caudal to the inferior border of the anterior C1 ring, with no extension into the superior articular facets of C2. If the fracture extends into one of the superior articular facets of C2, the fracture was classified as a type III fracture. To further define the personality of Type II fractures regarding fracture line obliquity, displacement, and comminution that clearly affect treatment recommendations, Grauer et al,17 have also suggested a subclassification of type II fractures.Type IIA describes a minimally or nondisplaced fracture with no comminution. These fractures are generally treated with external immobilization. A Type IIB fracture is a displaced fracture extending from anterior-superior to posterior-inferior, or a transverse fracture. These fractures can be treated with anterior screw fixation following fracture reduction, assuming adequate bone density. Type IIC was defined as a fracture line extending from anterior-inferior to posterior superior or a fracture with significant comminution. These fractures are generally treated with posterior C1-2 instrumentation and fusion.

Clinical Assessment

In geriatric population, is important to look for any associated clinical comorbidities that may affect management.  A full neurologic   assessment is obtained and the entire spine should be imaged to rule out any noncontiguous spinal injuries. There is 34% risk of noncontiguous spine fractures associated with the presence of an odontoid fracture,.24  

Imaging Studies

In some centers a computerized tomography (CT) of the cervical spine is currently done as the primary modality to assess for cervical spine injury due to the inherit limitation of the plain radiographs in evaluating the upper cervical spine and cervicothoracic junction.18, 19, 20 Furthermore, a recent report suggested that CT imaging should be used to obtain rapid, efficient cervical spine evaluation and negate the need for plain radiographic imaging.21 However, the authors still recommend the traditional three plain x-ray cervical spine series (anteroposterior, cross table lateral and open mouth view) for the initial assessment of patients with a suspected odontoid injury. .22, 23 The rational for obtaining  plain radiographs is for the surgeons to get familiar with the personality  of the fracture on plain radiographs which is the modality that will be used intraoperatively in case of surgical management. 

A transverse fracture line may be missed on a CT scan axial cut. Therefore, it is important to evaluate carefully the reformatted (sagittal, coronal) CT images. Magnetic resonance imaging (MRI) should be obtained if there is a neurologic deficit or to evaluate for suspected ligamentous injury.

Management:

Several important factors should be considered when deciding on the best management plan for displaced type II odontoid fractures in elderly patients. These factors include decreased bone density that interferes with adequate fixation with anterior odontoid screw, the fact that the elderly do not tolerate halo immobilization well and most importantly associated medical comorbidities. The literature has shown that, when comparing fractures in persons younger than 40 years to those older than 65 years, there was a 35% earlier mortality following treatment in the elderly population.4, 5, 6, 25, 26

Treatment options for displaced odontoid fractures can be conservative or surgical. Conservative management includes immobilization in a cervical collar or halo vest. Surgical management includes odontoid screws fixation, or C1-2 posterior instrumentation and fusion that can be achieved with either C1-2 transarticular screws or C1 lateral mass screw and C2 pars screws. 1, 2, 3, 11, 12, 13, 14, 15, 16

Conservative Management through External Immobilization with Cervical Collar or Halo Vest

External immobilization with a cervical collar has led to inconsistent results. The associated nonunion rate is believed to be caused by the high degree of instability of this fracture pattern.^{27, 28, 29}  This nonunion rate may also be related to a decreased vascularity at the watershed region at the odontoid base, thus producing a decreased healing potential. Consequently, some surgeons have recommended halo vest immobilization for type II odontoid fractures.²⁸ However, halo vest immobilization is still associated with a significant nonunion rate in a number of series, ranging from 26% to 80%.^{5, 8, 9, 27, 30} Furthermore, halo vest use in the elderly has been associated with complications in the range of 26%, including poor reduction maintenance, pneumonia, pin site infection, cerebral spinal fluid leakage, and even death.^{30-, 31}

Some surgeons believe that a stable nonunion achieved after external immobilization with a cervical collar in the elderly population is an acceptable risk when considered against the potential morbidity of surgical intervention. Often times a semi-rigid cervical collar is the treatment of choice (figure 1).

Figure 1 A-B. Lateral and open mouth views of 79 year old male showed Type II odontoid fracture which was sustained after a fall while walking. Patient was treated in Miami J collar for 3 months.

Figure 1-C Two months follow up lateral view showed maintenance of acceptable alignment

Figure 1-D Six months follow up lateral view showed bridging callus across the fracture site.

Surgical Management

Due to the concerning high incidence of nonunion with external immobilization, multiple studies have suggested primary surgical management in elderly patients that include either anterior odontoid screw fixation or posterior C1-2 instrumentation and fusion.^{26, 28,}

Well agreed upon indications for surgical management in displaced type II odontoid fractures include; poly-trauma patient, neurologic deficit, and associated unstable subaxial spine injuries that require surgical fixation. In these cases the surgeons can use either anterior odontoid screw fixation or posterior C1-2 instrumentation and fusion depending on patient’ s body habit, presence of osteoporosis, the obliquity of the fracture line, and the ability to achieve successful anatomic reduction of the fracture. One has to elect posterior C1-2 fusion rather than anterior odontoid screw in displaced type II odontoid fractures that are associated with C1-2 instability secondary to transverse ligament injury and symptomatic nonunion that develops after either external immobilization or anterior odontoid screw fixation. ^{26, 28}

Odontoid fracture combined with subaxial unstable cervical spine injury is uncommon and rarely reported in the literature. Closed reduction should be tried first and then both fractures can be fixed, if possible, under the same anesthesia.  The priority in the surgical management should be given for the fracture that causes spinal cord injury in patient with neurologic deficit. If the patient is neurologically intact then the priority is given for the fracture that could not be successfully reduced with preoperative traction. If the patient is neurologically intact and both fractures are successfully reduced with preoperative traction, one has to consider the extend of instability between the odontoid fracture and the subaxial cervical spine injury and the risk of surgical intervention involving each injury. Many would choose to surgically stabilize both injuries while others would prioritize stabilizing the subaxial cervical spine when the odontoid fracture is successfully anatomically reduced with preoperative traction. 

Figure 2 A Lateral view of 83 year old male showed comminuted Type II odontoid fracture with posterior displacement and posterior angulation which he sustained after a motor vehicle accident. 

Figure 2 B Axial CT scan showed associated C 1 anterior arch fracture

Figure 2 C Lateral view showed C1-2 posterior fusion with transarticular screws and sublaminar wire.

Anterior Odontoid Screw Fixation

To avoid loss of 50% of cervical rotation with C1-C2 fusion Bohler in 1982,³²  described anterior odontoid screw fixation. Specifically designed retractors and biplanar fluoroscopy are important for this procedure. After adequate fracture reduction following patient positioning on the operative table and ensuring appropriate trajectory for screw placement with the help of  fluoroscopy, a low cervical approach is made around the C5-C6 level. The prevertebral plane is then developed, allowing access to the C2-C3 disk space. The entry site for the screw is at the anterior-inferior corner of the C2 endplate and although preservation of the C2-C3 disk space is important, most surgeons apply the screw through the C2-C3 disk space to ensure an adequate screw trajectory. Two screws have been initially used with this technique. However, most surgeons are currently using a single screw as studies have shown no significant difference between the biomechanical stability or nonunion rates of 1 or 2 screws. Furthermore, it is often not safe to place 2 screws.^{33, 34}

The reported fusion rates with anterior odontoid screw have ranged from 83% to 100%.^{12, 33, 35, 36} However, Anterior odontoid screw fixation is not suitable for each type II odontoid fracture. This method is only appropriate for type II fractures that could be adequacy reduced. Patients with cervical or thoracic kyphosis and short, thick necks may also not allow for appropriate trajectory for screw placement. Furthermore, the fracture should have right obliquity to allow compression across the fracture site and avoid displacement with lag screw fixation. The ideal fracture geometry is a Grauer type IIB fracture which is a displaced fracture extending from anterior-superior to posterior-inferior, or a transverse fracture.¹⁷ In addition, this method of fixation should be avoided in osteoporotic bone, pathologic fracture, or nonunion where fracture fixation and subsequent healing are impaired. Based on the previous facts one would not expect to use anterior odontoid screw fixation in the elderly population in which osteoporosis is prevalent. 

Posterior C1-C2 Fusion

Several surgical techniques have been described to achieve posterior C1-2 fusion. These include sublaminar wiring, C1-C2 transarticular screws, and Harms posterior C1 lateral mass and C2 pars screws. ^{12, 13, 14, 37} Gallie¹³ described the first posterior C1-C2 wiring technique. This technique used a single central wire placed in a sublaminar position, under the ring of C1 and around the C2 spinous process. The wire provided stability and also served to secure a structural autograft in place. Brooks and Jenkins ¹⁴ later introduced an alternative wiring technique using bilateral sublaminar C1-C2 wires with 2 structural autograft blocks. A major disadvantage of sublaminar wiring technique is the potential risk of spinal cord injury while passing the wires. Furthermore, sublaminar wires cannot be used with concomitant C1 posterior arch fracture.

An alternative method of C1-C2 stabilization is that of transarticular screws (figure 2).¹⁵ An appropriate screw trajectory should be confirmed with fluoroscopy after patient positioning on the operative table. The procedure should be abandoned and an alternative method of fixation should be used if an appropriate screw trajectory cannot be achieved due to the patient’s body habit such as with morbid obesity and advanced thoracic or cervical kyphosis.  After open posterior exposure of the upper cervical spine that usually extends from C1 to C 3 the starting point for the screw insertion on the C 2 lateral mass is identified. The screws are then inserted in a percutaneous fashion through two small stab incisions at the cervicothoracic junction. The screw is then advanced along the isthmus of C2 and into the C1 lateral mass. In the original description of this technique the authors used adjuvant sublaminar wiring and structural bone graft applied over the posterior arch of C 1 and C2 lamina. The reported fusion rates with this technique have approached 100%.^{15,  16,  38} However, recently some surgeons started to use C1-2 transarticular screws without adjunctive sublaminar wiring and elect to decorticate and apply bone graft within the C1-2 joint and over the C1 posterior arch and C2 lamina. However, elimination of the posterior wiring produces only 2-point fixation, which has been associated with increased flexion and extension motion.³⁹

There are limitations to C 1-2  transarticular screw technique that include the required reduction of C1 on C2 before screw placement, risk of vertebral artery injury, and potential bleeding from dissection surrounding the C2 pedicle.³⁷ If transarticular screws are considered, preoperative CT should be evaluated to make sure that an appropriate and safe screw trajectory exists.

 To avoid the limitations of transarticular fixation, Harms and Melcher have introduced a technique for screw fixation using posterior C1 lateral mass and C2 pars screws.  Once the screws are placed, the reduction of C1 relative to C2 can be adjusted if necessary before securing the screws with a short rod construct. This technique produced 100% fusion in all 37 patients at 1 year and had no neurologic, vascular, or implant complications. ³⁷

Biomechanical studies showed that the Brooks and Jenkins wiring technique was 2.5 times more stable than the Gallie wiring technique and C1-2 transarticular screw constructs have had a 10-fold increased rotational stiffness and similar lateral bending stiffness when compared to that of posterior wiring techniques.^{40, 41, 42}  Biomechanical comparison of Harms posterior C1 lateral mass and C2 pars screws to bilateral C1-C2 transarticular screws with Gallie wiring showed significantly decreased motion in lateral bending and axial rotation with both the Harms and transarticular screw constructs. Furthermore, no significant difference was documented between the transarticular and Harms methods. ⁴³

Nonunion

Type II odontoid fractures are less stable, and associated with higher nonunion rates when compared with type I and III odontoid fractures. Factors associated with an increased incidence of nonunion for type II odontoid fractures include posterior fracture displacement, displacement > 5 mm, >10° of angulation, fracture comminution, delayed treatment, and patients older than 40 years.^{7, 44, 45, 46}

Asymptomatic nonunions are often observed without any active surgical intervention although this often spurs debate. Patients with a symptomatic nonunion often present with persistent neck pain,   myelopathy, or both. In such a case surgical management should be considered. Several factors should be looked at carefully before deciding on the best surgical option. These factors include associated medical comorbidities, whether the presenting symptom is pain only or associated with myelopathy, and finally the status of the subaxial spine. In patients with severe medical comorbidities that render surgical management risky, one may elect to continue with conservative management. Posterior C1-2 fusion is the procedure of choice for patients presenting with a chief complaint of pain. Patients presenting with myelopathy may require decompression that may be achieved by resection of the posterior C1 arch and possibly a portion of the C2 lamina.⁴⁷  One may also choose to extend the instrumentation and fusion to the subaxial spine in patients with advanced subaxial spondylosis and spinal canal stenosis. In these cases, it will be very difficult to know if myelopathy is related to the odontoid nonunion or the subaxial spinal canal stenosis.       

Summary :

Despite the frequency of odontoid fractures in elderly, there is still lack of consensus on the best treatment option for displaced type II odontoid fractures. This reflects the reality that there is not yet any single ideal solution for this clinical problem. Odontoid fractures should be evaluated with appropriate imaging to assess the fracture itself as well as exclude other contiguous or noncontiguous fractures.  External immobilization with a cervical collar has led to inconsistent results. Halo vest immobilization in elderly is associated with a significant nonunion rate and several complications. However, some surgeons believe that a stable nonunion achieved after external immobilization with a cervical collar in the elderly population is an acceptable risk when considered against the potential morbidity of surgical intervention. Well agreed upon surgical indications are the poly-trauma patient, the presence of a neurologic deficit, an associated unstable subaxial spine injuries that requires surgical fixation and a symptomatic nonunion. Surgical management includes either anterior odontoid screw fixation or posterior C1-2 instrumentation and fusion.

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This is a peer reviewed paper 

Please cite as : Hossein Elgafy: The Treatment of Displaced Type II Odontoid Fractures in Elderly Patients

J.Orthopaedics 2008;5(1)e17

URL: http://www.jortho.org/2008/5/1/e17

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