Surgical management of odontoid fractures at Level one trauma center: A single-center series of 142 cases
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.152633
Source of Support: None, Conflict of Interest: None
Introduction : Odontoid fractures constitute 9-20% of all adult cervical spine fractures. The present study was carried out to focus on the nuances involved in the surgical management of odontoid fractures.
Keywords: Fusion rate; odontoid fracture; outcome; surgical fixation; trauma
Odontoid fractures comprise 9-20% of all cervical spine fractures. ,,, Due to the strategic location of the fracture, many patients succumb at the scene of the accident due to spinal cord injury.  In the surviving patients, the most common symptom is pain; major neurological deficits are infrequent. , The problem with the conservative management of these fractures is the risk of non-union and the delayed development of myelopathy. ,
Anderson and D'Alonzo (1974)  have classified odontoid fractures into type I, II and III. Based on this universally accepted classification, the type II and III odontoid fractures often require some form of stabilization. ,, However the optimum treatment strategy on whether to perform surgery or to continue the patient on conservative management is still mired in controversy. ,, The surgical approaches prevalent for dealing with acute odontoid fractures include either an anterior odontoid screw (OS) placement or a posterior fixation (PF). ,,,,,,,,,,,,, The anterior fixation procedure has the advantage of preserving C1-C2 motion and head/neck rotation. 
The aim of this study was to study the outcome related to bony union and functional recovery in a large cohort of patients admitted to our institution, who underwent surgery for acute odontoid fractures between January 2008 and March 2014.
The clinical records of patients having an odontoid fracture and admitted between January 2008 and March 2014 were retrospectively reviewed. During this period, a total of 155 patients were admitted with type II and type III odontoid fractures.
The parameters noted included their demographic profile, neurological status (at admission), associated risk factors, injury characteristics (type, displacement, etc.), ictus-surgery interval (age of fracture), surgical details, perioperative and clinico-radiological long-term outcome. The initial pre-operative evaluation was performed with anterior-posterior (AP) and lateral dynamic plain radiographs of the upper cervical spine. Computed tomographic (CT) and magnetic resonance imaging (MRI) scans further delineated the soft tissue and bony pathology.
Surgical intervention was preferred over conservative management in type II and type III odontoid fractures at our center due to its advantage in being able to achieve an instantaneous fixation, thus permitting an early mobilization and rehabilitation. A halo brace requires prolonged application before fusion is achieved. It is also very cumbersome to use with a relatively low compliance, especially in the hot and humid environment of the Indian sub-continent. Hence, conservative management was only considered in those patients who had a non-displaced and a stable odontoid fracture; and, in those, who were either unfit for anesthesia due to severe comorbidities or were unwilling to undergo surgery. The 13 patients who were treated conservatively were excluded from the study. Thus, 142 patients, treated by surgery, were enrolled in this study.
A preoperative traction was applied in 140 patients (98.6%). Non-displaced (55 patients; 39.3%) or minimally displaced (46 patients; 32.8%) fractures could be managed with a traction applied after induction of anesthesia; however, significantly displaced fractures (39 patients; 27.9%), requiring preoperative reduction of the displaced fragments, could only be aligned by the application of traction in the ward with progressive increase in the traction weight and a serial assessment of the reduction achieved with the translational pull. The serial radiological assessment of the reduction achieved was helpful in determining the appropriate surgical procedure. The traction also helped in maintaining the reduction of fracture dislocation during surgery. Nine patients with a remote history of trauma did not show reduction of the odontoid fracture following preoperative placement of traction; in five patients only partial C1-2 reduction was possible. In the remaining 126 patients, a proper preoperative odontoid alignment with C1-2 reduction could be achieved.
An anterior OS placement was preferred over PF in both type II (including anterior oblique fractures and comminuted type IIA fractures) and type III (high type) odontoid fractures as it preserved C1-2 mobility [Figure 1]. A proper alignment of the fractured segments following application of the traction and the intactness of the transverse ligament (determined on MRI imaging) were the essential pre-requisites for an anterior OS fixation. Only acute fractures that were sustained less than 3month ago were considered for OS fixation. The 85 (59.9%) patients fulfilling these criteria underwent an anterior OS fixation. The time frame of injury in all our patients who underwent an anterior OS fixation was of less than 2 months (median injury-surgery interval: 10 days, range 1-65 days).
The remaining 57 (40.1%) patients, who were not considered suitable for an anterior OS fixation, underwent PF for acute as well as remote fractures (median injury-surgery interval: 22 days). Bony union was achieved by supplementing the metal construct with an onlay bone graft harvested from the posterior iliac crest. The details of the various surgical procedures are listed in [Table 1].
A segmental C1-C2 fixation was preferred over a more extensive, occipitocervical fusion (OCF). Patients who had well-aligned C1 and C2 vertebrae and absence of a high-riding vertebral artery underwent either the Magerl technique (C1-C2 transarticular fixation) or the Goel/Harm technique (C1 lateral mass [LM] - C2 pedicle/pars [PS] fixation using screws and rods). Lack of a proper C1-C2 alignment resulted in only the later procedure being considered. Thus, a C1-C2 transarticular fixation (Magerl technique) was performed in 16 patients. This procedure was supplemented with a sub-laminar C1-2 wiring in 11 patients. The more versatile Goel/Harm technique, that produced an equally rigid C1-C2 construct, was performed in 14 patients (including the five patients who were not considered fit to undergo Magerl's fixation due to the presence of an incompletely reduced fracture [Figure 2]). Five patients, having intact C1 and C2 posterior elements, underwent C1-C2 sub-laminar wiring with onlay bone graft stabilization.
In 13 patients, with associated C1-2 posterior element fractures, the more extensive OCF (fusing the occipital bone with the C3 and C4 vertebrae) was performed. A contoured rod was used for OCF in three patients who could not afford the occipital-lateral mass construct. An anterior compression due to a malunited odontoid fracture was present in nine patients. This was not reducible even by the translational pull of the traction. These patients underwent a transoral decompression followed by the OCF.
During the post-operative period, movements at the neck were prevented using a Philadelphia cervical collar for 12 weeks. At follow-up visits, dynamic plain lateral upper cervical radiographs and a CT scan were performed at an interval of 3 months. Bony union was confirmed by visualizing bony trabeculations crossing the fractured site, absence of motion on flexion/extension images, absence of sclerotic borders adjacent to the fracture site, and a bony union at the PF site. Fusion occurring after 3 months was referred as "delayed fusion". "Non-union" referred to absence of bony union even after 9 months of the surgical procedure.
Demographics, mechanism of injury, and fracture characteristics
One hundred and forty two patients [127 men and 15 women, with a median age of 28 years, range: 4 -75 years] underwent surgical stabilization for type II or type III odontoid fractures. Motor vehicular accidents were most common cause (58%) of the odontoid fracture; in elderly population, however, the fracture was usually sustained by a fall. Most of the patients (83.8%) had a type II fracture (including a comminuted type IIA fracture) in 6.7% patients. The details of the fracture sustained are listed in [Table 2].
Neurological symptoms, associated injuries, and risk factors
The most common neurological symptom was neck pain (88.6%) while neurological deficits were present in 45.7% patients. The severity of spinal cord injury was further quantified by using American Spinal Injury Association (ASIA) grades [Table 3]. Forty-two patients had associated injuries while 100 patients had an isolated injury of the odontoid process. Head injury (12.7%) and cervical spine fractures (11.2%) were most commonly associated injuries. Seven patients had a concomitant systemic illness (cardiac disease) and four patients had an associated diabetes mellitus.
Outcome and procedure-related complications
Anterior odontoid screw fixation
Of the 85 patients (59.9%) who underwent an anterior OS fixation, procedure related morbidity occurred in 10 (11.7%) patients of whom 6 (7%) underwent resurgery. Failure of fixation occurred in three patients (3.5%). The OS pull through was subsequently managed by the Magerl technique combined with C1-C2 sub-laminar wire fixation [Figure 3] and [Figure 4]. A patient required revision of the OS due to malposition of the odontoid screw. Two others underwent revision surgery for pseudo-arthrosis [Table 4].
A patient who had a K wire breakage during drilling, underwent a revision OS procedure during the same sitting, leaving the broken K wire in situ [Figure 5]. One patient (1.1%) died due to cranial migration of the K wire causing a diffuse subarachnoid hemorrhage [Figure 6].
After three months of surgery, 7 of the patients, who had undergone an OS placement procedure, had a recurrence of C1-2 dislocation. Three of them had a delayed bony union; 2 underwent a Magerl procedure; one refused surgery and was continued on conservative management; and, one was lost to follow-up. In 80 patients with a successful OS screw fixation who were available for follow up evaluation, bony union was achieved in 91.2% patients at 3 months and in 95% upto their last available follow-up. Thus, non-union persisted in 5% patients.
Two patients who underwent C1-C2 wiring (Gallie's technique) had a non-union at follow-up. One of them in whom failure of reduction had occurred due to the wire cutting through the posterior elements, required an occipito-cervical fixation. The other patient was managed conservatively with a Philadelphia collar as he was symptom-free and there was no instability. This patient was lost to follow up so no further details are available. The overall fusion rates after PF were 96.5% (for type II fractures: 94.7%; and for type III fractures: 100%).
No patient had an intraoperative vascular injury and there were no procedure-related deaths. The overall morbidity rate was 8.7% with two patient requiring revision surgeries. Two patients, who had severe neurological deficits and belonged to the category of ASIA A died during their hospital stay due to ventilator-associated pneumonia.
The mean follow-up of the patients was 22 months (range: 6 months to 5.4 years). At the last follow-up, 83 patients (97.6%) who underwent anterior fixation and 55 patients who underwent PF (96.4%) survived with an overall survival rate of 97.1%.
Out of 65 patients who had a preoperative neurological deficit, four patients died, two patients maintained their neurological status and rest of the patients had improvement in their neurological grade. The neurological status at the last follow-up was ASIA grade B in two patients; ASIA grade C in nine patients; ASIA grade D in 21 patients; and ASIA grade E in 106 patients.
Odontoid fractures comprise 9-20% of all cervical spine fractures. Thus up to one in five patients with a cervical spine fracture will sustain an odontoid fracture. ,,, The treatment aims to reestablish the stability of the atlanto-axial complex by restoring the alignment of the odontoid process and prevent secondary complications due to non-union and instability. ,,
Conservative management using a halo brace is associated with variable fusion rates between 53-93%. The associated morbidity is related to its prolonged usage in a recumbent patient. ,, Shetty et al.  demonstrated an 84.2% fusion rate with conservative management in stable type II fractures. Literature shows that there is a growing trend towards surgical fixation of these fractures as fusion rates are better and the patients may be mobilized early. , In the present series, primary surgical intervention was preferred in all patients except the 13, who were either declared unfit for surgery or were not willing to undergo surgical intervention.
Since its initial description by Nakanishi  and by Bohler (1982),  anterior OS fixation has withstood the test of time. This procedure allows for a more physiological fusion by direct osteosynthesis of the fracture lines and has the advantage of preserving normal rotation at the atlanto-axial joint. , Eighty-five patients (59.2%) who had an acute, well-aligned odontoid fracture (type II fracture: 75 patients, type IIA fracture: 4 patients, and, type III fracture: 6 patients) with an intact transverse ligament, underwent OS fixation at our center. The fusion rate of 95% after OS fixation in our series was comparable with the results in the available literature (87-100%). ,,,,,,
Many authors have recommended PF as the procedure of choice for the surgical approach in type IIA and type III fractures due to a slightly higher non-union rate associated with OS fixation. Our results of 95.8% and 100% fusion rates in type II and high type III fractures are comparable with the published literature. ,,, Moon et al.,  Fountas et al.,  and Lee et al.  in their series showed fusion rates of 100%, 87%, and 96%, respectively. Bhanot et al.  reported a 94% fusion rate with one case of non-union and one screw pull-out in their series of 17 type II odontoid fractures after an anterior screw fixation. Shrinivasan et al. could successfully place OS in 84.6% type II fractures with an 82% fusion rate.
Aldrian et al. (2011)  showed a good fusion rate of 87% after OS fixation in type IIA fracture and have also recommended it as the first line of management in comminuted odontoid fractures. Other authors, in a contrasting opinion, have recommended against utilizing an OS fixation in type IIA comminuted fractures due to the high non-union rates and have preferred the PF techniques. ,, In our series, out of four patients with type IIA fracture who underwent OS fixation, three patients showed a good union while one patient, who developed non-union, was successfully managed by PF. A recommendation by Aldrian et al.,  is that in type IIA fracture, the initial surgical procedure should be an anterior OS fixation; and, PF should be reserved for cases where the initial procedure fails.
Apfelbaum (2000)  and Dantas (2002)  have advised against the placement of anterior OS in fractures with an anterior oblique fracture line due to the high non-union rates. In contrast to their results, in our series, out of eight patients with a less steep, anterior oblique fracture, only one patient had a non-union after OS fixation. Therefore, whenever the angle of the odontoid fracture line is less oblique and screw trajectory across the fractured segments is achievable, OS fixation should be the first line management option as it provides for better functional results.
In elderly patients, the available class III evidence recommends surgical over conservative management. Which operative approach to adopt is still a matter of debate. According to a recent meta-analysis by Ryken et al.  , a wide-ranging opinion exists with some authors reporting no difference in the results of anterior versus posterior approaches while others have preferred one approach over other. Overall, seven patients with age greater than 60 years underwent surgical intervention (OS fixation-6; PF-1) and all of them showed a good bony union. Therefore, an elderly age should not be a contraindication for the OS fixation. We used a single cannulated, partially threaded lag screw in all these patients with a good result. The current literature also supports our approach in that there is no difference in the fusion rates with either a single or double screw placement. ,
Overall, there was a morbidity of 11% and a mortality of 1.1% in our series. This was comparable to the published literature.  The one procedure related death (1.1%) was due to diffuse SAH as a result of cranial migration of the K wire. Occurrence of SAH was probably due to a vascular injury. This complication has rarely been reported with an OS placement and only three cases have been published in the literature. In our patient, this may have been the result of a mal-positioned K wire or a misplaced screw.  Hence, one should be very careful while drilling a hole in the odontoid process especially during the process of achieving the bi-cortical purchase. Maneuvers such as the use of a stopper to prevent migration, screw placement under image guidance, and utilizing only a unicortical purchase are possible solutions to avoid this unfortunate complication. ,
We performed primary PF in 57 patients (40.1%) with a fusion rate of 96.4%. Fusion rates (94.7%) in type II fractures were inferior to the type III fractures (100%) but were comparable to the fusion rates quoted in literature that have ranged from 87% (in type II fracture) to 100% (in type I and type III fractures).  Inclusion of the occipital bone in the construct was associated with a significant compromise of neck movements.
With the Magerl technique, we had a fusion rate of 100% that is comparable with the reported literature. , This technique may be used as a stand-alone procedure or may be supplemented with a C1-C2 sub-laminar wiring. Addition of sub-laminar wiring, however, did not change results of this technique in our series. This procedure is technically difficult and requires a steep upward trajectory. The three-point rigid fixation and cost-effectiveness of the procedure is responsible for its popularity. The Goel/Harms technique of C1-C2 fixation is more versatile when compared to the former procedure. We had fusion rates of 100% in the 14 patients who underwent this form of fixation. This is comparable with the results published in literature.  There is, however, a risk of 1.3-5.8% (more with Magerl technique) of vertebral artery injury in posterior fusion procedures.  The C1-C2 wiring and graft placement technique was used in five patients who, however, had a poor outcome (with the fusion rates being only 60%). The biomechanical strength of this fixation is also less than ideal as compared to the Magerl or Goel/Harms procedure (that provides a strong rotational stability). ,,, Therefore, the C1-C2 sublaminar wiring technique should be used as the last resort. Shetty et al.  in their retrospective series showed a 100% fusion rate after posterior C1-C2 arthrodesis with the Magerl technique (eight patients) and the Goel/Harms technique (three patients) compared with C1-C2 sub-laminar wiring and graft fixation (nine patients) that had a failure rate of 33%.
OCF is the final option available when segmental posterior C1-2 fixation procedures cannot be performed; or, when the patient has undergone a simultaneous transoral decompression of the malunited fractures. We performed an OCF in 13 patients (including three in whom a contoured rod procedure was performed). Nine of them underwent OCF following a transoral odontoidectomy (TOO) for anterior compression. All these patients had a good fusion (and results were comparable to literature) but at the cost of significant neck movement compromise. 
Anterior OS fixation should be considered the first-line of management in well-reduced, acute type II and high type III fractures, including the type IIA fractures, as it preserves cervical motion. PF is also associated with excellent fusion rates but should be reserved for patients in whom OS fixation either fails or is not feasible.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
[Table 1], [Table 2], [Table 3], [Table 4]