Posterior C1-C2 fusion may be achieved via posterior wiring and bone grafting (Brooks or Gallie technique), placement of posterior C1-C2 transarticular screws (Magerl15), posterior C1 lateral mass–C2 pars instrumentation and fusion (popular- ized by Harms and Melcher16), and placement of posterior C1 lateral mass–C2 lami- nar screws. The use of transarticular screws and C1 lateral mass–C2 pars/laminar screws17 has largely supplanted sublaminar wiring.1 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 biome- chanical stability afforded by later-generation posterior constructs there has been a concomitant decrease in the use of postoperative halo vest immobilization.1,18 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 verte- bral 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 neurologi- cally intact. The fracture is posteriorly displaced and angulated. Because posterior dis- placement 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.19 In addition, if the sur- geon 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,20,21 and this may be the case in an elderly patient with significant comorbid medical conditions that result in a predomi- nantly 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 colleagues7 suggests that it is in the setting of a dis- placed 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,19 and so any preoperative closed reduction procedure probably car- ries 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 proce- dure 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.1 Sev- eral 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 non- union is higher in elderly than in younger patients.22 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 tech- nique) (Figure 11-2). The patient was extubated on postoperative day 1 and pro- gressed 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 indepen- dently 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 atten- tion to these details is essential (Tips from the Masters 11-1).
A B
FIGURE 11-2 Postoperative lateral (A) and AP (B) radiographs demonstrating fracture reduction with C1 lateral mass and C2 pars instrumentation.
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 fora- men identified on CT images of C1 and C2, with careful attention paid to the diam- eter 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 endo- tracheal 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 lat- eral 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 • Use two Penfield dissectors to eliminate parallax when orienting for lateral fluoroscopy.
At this point dissection of the soft tissues inferior to the C1 lateral mass, the cav- ernous sinus, and the C2 greater occipital nerve should be performed, and the C2 greater occipital nerve should be mobilized inferiorly. This can be done with mini- mal blood loss with the aid of a small thrombin-soaked patty and Penfield dissector, with the patty used to sweep the soft tissues away from the lamina. If the epidural plexus is disturbed, the surgeon should be prepared to encounter brisk venous bleeding; this can be controlled using a thrombin-soaked absorbable gelatin sponge, cottonoid patty, and FloSeal hemostatic matrix (Tips from the Masters 11-3).
Tips from the Masters 11-3 • Careful dissection with a thrombin-soaked patty will minimize epidural bleeding in the C1-2 interval.
After exposure of the C1-C2 articulation, the medial and lateral borders of the inferior articular process of C1 should be palpated with a Penfield 4 dissector, and a 2-mm bur used to score the starting point for drill insertion. Notching of the inferior cortex of the posterior ring of C1 may be necessary to obtain the correct starting point and trajectory. This can be done with either a Kerrison punch or bur, with careful attention to the superior vertebral artery (Figure 11-3). Using real-time fluo- roscopy, a drill is then advanced past the starting point to cannulate the lateral mass.
It is crucial that the proper sagittal trajectory be maintained. In the sagittal plane the drill should be parallel to the C1 posterior arch, and it should be medially angulated 5 to 10 degrees (Tips from the Masters 11-4). After drilling, a ball-tipped probe is used to confirm that the lateral mass has not been breached. Screws of the appro- priate length should be placed. Use of a partially threaded screw is recommended, because the smooth exposed shank will minimize neural irritation.
Tips from the Masters 11-4 • The undersurface of the C1 ring may need to be notched for proper C1 lateral mass instrumentation.
After insertion of the C1 lateral mass screws, the C2 isthmus screws can be placed using palpation of the medial border. Preoperative CT images should be carefully reviewed to confirm that there is adequate space to accommodate a screw. The medial border of the isthmus should be palpated from within the canal, and a 2-mm drill should be used to cannulate the pilot hole. The starting point is proximal to the C2-3 facet and should be confirmed both by palpation of the medial border of the isthmus and by preoperative imaging. A general guide for the starting point is the intersection of the pars interarticularis with a horizontal line through the midline of the lamina of C2; however, there is no universal starting point, and preoperative planning is essen- tial (Figure 11-4). Preferred practice is to bias the starting point superior and medial to the intersection of the pars and midline of the lamina, with careful use of a Penfield 4 dissector to define the medial border of the pars. The starting point should be initi- ated with a bur, and then a 2-mm drill should be used. The drill should have a medial angulation of 20 to 30 degrees as it is advanced, with the assistant taking care to delin- eate the medial border of the isthmus with palpation, providing visual confirmation of the trajectory. The pilot hole should be carefully probed, and then the screw placed.
Optimal bone grafting is essential to achieve osseous union. Tricortical iliac crest autograft is the gold standard. However, harvest of tricortical iliac crest is associated with donor site morbidity, and in an elderly patient the quality of the graft may be sub- optimal. If the surgeon feels that patient-specific factors preclude autologous iliac crest structural graft harvest, an alternative is allograft. The preference is to use autologous graft whenever possible, but when circumstances require it, good results have been achieved with patellar bone allograft. The graft must be appropriately sized so that it fits securely between the cortical surfaces of the inferior ring of C1 and the C2 lamina; the graft can be notched superiorly to match the contour of C1 and inferiorly to straddle the
Minimum width
Minimum height
FIGURE 11-3 Starting point for lateral mass screw. Note the posterior overhang of C1, which may need to be notched to facilitate proper screw trajectory.
A B
FIGURE 11-4 AP (A) and lateral (B) representations of instrumentation. Note the relationship of the vertebral artery. The general starting point for the C2 screw is the intersection of the pars and the midline of the lamina; this must be confirmed with careful palpation of the medial border.
C2 spinous process, and then gently wedged into place. With proper dimensions the fit should be tight—compressive force is necessary to promote adequate fusion. The graft can be bolstered in place with suture material looped under the lamina and over the graft in a figure-eight pattern (Tips from the Masters 11-5). Alternatively, the graft may be secured with stainless steel wire or titanium cable using a modified Gallie technique.
Tips from the Masters 11-5 • Graft may be bolstered with suture material to minimize risk of dislodgment.
As with all posterior cervical cases, meticulous hemostasis and wound closure technique are imperative. Preferred practice is to use a cervical orthosis (Philadelphia collar) in the postoperative period and to place a drain deep to the fascia. Patient- specific issues should be considered in determining the length of time the cervical orthosis should be worn. The recommendation is to maintain the orthosis for a mini- mum of 6 weeks; at that point the relative merits of continued immobilization should be balanced against patient-specific factors such as ease of feeding and activity level.
For a minimally active patient who is developing occipital irritation and/or having difficulty eating, it may be reasonable to discontinue use of the orthosis.
DISCUSSION OF BEST EVIDENCE
The current evidence regarding the management of type II odontoid fractures comes primarily from Level III studies as well as from some Level II studies. No Level I evidence is available.