A new transodontoid fixation technique for delayed type II odontoid fracture: technical note

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Surgical Neurology 71 (2009) 121 – 125 www.surgicalneurology-online.com

Technique

A new transodontoid fixation technique for delayed type II odontoid fracture: technical note A. Fahir Ozer, MD a , Murat Cosar, MD b,⁎, Tunç B. Oktenoglu, MD a , Mehdi Sasani, MD a , A. Celal Iplikcioglu, MD c , Hakan Bozkus, MD, PhD a , Cengiz Bavbek, MD d , A. Cetin Sarioglu, MD a b

Departments of aNeurosurgery and dRadiology, VKV American Hospital, Istanbul, 34365 Turkey Department of Neurosurgery, Faculty of Medicine, Carakkale 18 Mart University, 17200 Carakkale, Turkey c Department of Neurosurgery, Okmeydani Education Hospital, Istanbul, 39363 Turkey Received 5 August 2007; accepted 10 September 2007

Abstract

Background: A different transodontoid screw fixation technique was studied in delayed type II odontoid fractures. This study presents observations on a different transodontoid fixation technique to remove and decrease the amount of sclerotic layers to accelerate the fusion process after the operation. Methods: Ten cases of chronic type II odontoid fractures were operated on via transodontoid screw fixation between 2000 and 2007 which were admitted 6 weeks or later after the trauma. Four of these 10 delayed patients were operated on using a new anterior transodontoid screw fixation technique, whereas the other 6 delayed patients were operated on using classical anterior transodontoid screw fixation. Results: Four delayed cases with type II odontoid fracture operated on via this new technique had good results throughout the minimum 38 months' follow-up period. We did not observe nonunion, infection, and/or other complications such as vascular or brain-stem injury. Conclusion: Transodontoid screw fixation should be considered as a preferable treatment modality. This surgical intervention may be an alternative to conservative treatment even for cases with delayed type II odontoid fractures. © 2009 Elsevier Inc. All rights reserved.

Keywords:

Cervical trauma; Odontoid screw fixation; Type II odontoid fracture

1. Introduction Sixty percent of all odontoid fractures are type II cases, forming a significant subgroup with a 6% mortality and morbidity rate [1,7,18]. As this group has a very small chance of spontaneous fusion with external immobilization, surgery is frequently the treatment of choice. Common treatment techniques include conservative halo immobilization and C1-

Abbreviation: CT, computed tomography. ⁎ Corresponding author. PK: 34 03000 Afyonkarahisar, Turkey. Tel.: +90 505 8041362; fax: + 90 272 2172029. E-mail address: [email protected] (M. Cosar). 0090-3019/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.surneu.2007.09.027

C2 posterior wiring with surgical fusion. The new concept of transodontoid screw fixation is becoming one of the first choices of treatment for type II odontoid fractures. C1-C2 posterior screwing is another alternative technique which provides more rigid fixation than posterior wiring. Nonunion is one of the major problems of odontoid fractures. A review of the literature has demonstrated multiple factors influencing nonunion of type II odontoid fractures such as patients' age, extent of neurologic damage, degree of dense displacement, presence of concomitant C1-2 fracture, preexisting pathologic condition, and age of the fracture [6,19]. It is well known that chronic and/or delayed type II odontoid fracture has a relatively high nonunion rate

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Table 1 Summary of 4 delayed type II odontoid fractures operated on with new transodontoid fixation technique Patient no.

Age (y)

Sex

Cause of injury

Time to admission

Neurologic status

Hospitalization period

Follow-up period

Outcome

1 2 3 4

50 25 29 47

Female Male Male Male

MVA a MVA MVA MVA

6 wk 12 wk 10 wk 7 wk

E E E E

4d 3d 2d 2d

72 mo 60 mo 51 mo 35 mo

E E E E

a

MVA indicates motor vehicle accident; E, neurologically intact; B, complete motor paralysis, some preservation of sensation.

[14]. Owing to difficulties in diagnosis, most cases were admitted several weeks after the trauma, described as delayed cases in this study. Fusion is diminished by sclerosis of the fractured bones, the C2 body, and odontoid. Therefore, immobilization for a long time (eg, halo brace) or curetting the sclerotic margins enhances bone healing. The technique described here eliminates the difficulty of curetting the sclerotic margins of the fractured bones. The study presented here discusses the results of 4 delayed type II odontoid fractures operated on via this new technique. 2. Clinical materials and methods 2.1. Patients Ten cases of delayed type II odontoid fractures admitted to the hospital at least 6 weeks (mean, 10 weeks) after the trauma between 2000 and 2007, and operated on with anterior transodontoid screw fixation. Four of the 10 cases of delayed type odontoid fracture were operated on via a new transodontoid screw fixation technique. The mean age of the patients was 37.7 years (range, 25-50 years), and most cases were male (3 male and 1 female). Motor vehicle accidents caused all of the injuries. All patients were found to be unstable after radiologic investigation. The odontoid bony fragment was displaced ventrally in 1 case (25%), dorsally in 2 cases (50%), and remained in the natural anatomic position in 1 case (25%). The neurologic status of the patients was classified according to the Frankel scale [9] which classifies the patients into 5 groups: (1) complete loss of both motor and sensory function below a given level; (2) some preservation of sensation, complete motor paralysis; (3) had motor and sensory function but the motor function is useless; (4) had motor function, but not normal motor function; and (5) neurologically intact. The clinical data of this patient group are presented in Table 1.

supine-positioned cases after fiberoptic intubation. A transverse midcervical skin incision was made at the C5C6 interspace and blunt dissection was performed down within the avascular plane to the prevertebral area and extended to the C2-C3 disc space. The cervical retractors were fixed after the dissection of paravertebral fascia and the C2-C3 interspace level was verified via the lateral C-arm fluoroscopic view. A 2-mm threaded K-wire is inserted into the midline of the anteroinferior edge of the C2 while levering on the C3 body with adequate trajectory under biplanar fluoroscopy. After the insertion of K-wire with an adequate trajectory, it is then drilled through the fracture line into the distal portion of the fractured dens. The K-wire was left in place for the fixation of fractured odontoid. After this process, another Kwire was used to create multiple entry points into the odontoid from the right and left side of the fixed K-wire (controlled under biplanar fluoroscopy) (Fig. 1). This process must be performed under biplanar fluoroscopy to avoid any potential vascular and brain-stem injury. After the preparation of multiple drills into the C2 body and odontoid, the odontoid screws were used for fixation. The

2.2. Surgical technique Because nonunion is a common problem in delayed cases owing to the sclerotic margins of the fracture site, an additional technique was applied to 4 of the 10 delayed cases. This presented technique was constructed over the transodontoid screw fixation technique described by Apfelbaum [2,3]. Biplanar C-arm fluoroscope was used for all

Fig. 1. Schematic illustration of the presented technique. After fixating the odontoid via a K-wire, multiple drills are performed in the body of C2 and the odontoid to enhance bone healing.

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(Table 1). The preoperative radiologic images of the first case are shown in Fig. 2 and its early and late follow-up radiologic images are seen in Figs. 3 and 4. In addition, the preoperative radiologic images of the third case are shown in Fig. 5A and 12 months' follow-up images are shown in Fig. 5B and C. 4. Discussion

Fig. 2. Patient 1: A sagittal reconstruction CT scan demonstrated a dorsally dislocated odontoid fracture.

decision of whether to place 1 or 2 odontoid screws was based on the size of the odontoid. Creating multiple holes in the sclerotic margins of the C2 body and odontoid provides more contact points of spongious bone to spongious bone, so it is expected to achieve better fusion. Although removal of sclerotic margins is a basic orthopedic concept to augment bone healing [14,17], this technique has not been previously applied to odontoid fractures. The analysis of bone healing was based on clinical and neuroradiological studies. All patients underwent cervical dynamic plain radiographs in the third and sixth postoperative months. Computed tomography scans were routinely performed between the 6th and 12th months. 3. Results In our limited series, 4 of the 10 delayed type II odontoid fracture patients were operated on via this new transodontoid fixation. We did not observe nonunion, infection, vascular injury, screw malposition, mortality, and morbidity for the mean 38 months of follow-up. The neurologic status of the patients was evaluated with Frankel scores and it did not change for all patients in the follow-up period after surgery

There is still debate on how to treat patients with type II odontoid fractures, with treatment modalities ranging from conservative therapy to surgery [20]. In the last decade, satisfactory results with surgical fixation popularized surgical intervention [2,13,20]. The difficulty of spontaneous fusion is a common problem in type II odontoid fractures. Nonunion is mostly affected by the slipping distance between the fractured odontoid and the body of C2, with a distance of more than 4 to 6 mm remarkably increasing the risk of nonunion [8,10-12]. On the other hand, the sclerotic margins of fractured sites prevent healthy fusion in chronic cases. Age also affects the rate of spontaneous fusion, which decreases over the age of 40 [4,7,8]. In addition, even for some young patients the treatment may require halo bracing for a long time. Halo bracing carries some disadvantages such as pain, infection at the pin sites, osteomyelitis of the skull, and social life problems such as job loss and decrease in income. Moreover, application of a halo brace application might result in nonunion [8,21]. Posterior C1-C2 wiring and bone fusion are the usual surgical technique. External support is necessary as this technique carries a risk of translational deformity until the completion of bone fusion. Although some series had satisfactory bone fusion rates, less successful series have also been reported with an 80% nonunion rate [10]. An alternative surgical technique to posterior C1-C2 wiring with fusion is the posterior C1-C2 transfacet screwing technique, which provides a more rigid fixation. Both of these surgical procedures share the same disadvantage: fixation of

Fig. 3. Patient 1: An early-term postoperative CT scan showed the fixation of odontoid fractures using one screw. The screw is in the confines of the odontoid in 3 planes (A: sagittal; B: coronal; C: axial).

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Fig. 4. Patient 1: The postoperative late-term CT scan (A: sagittal; B: coronal) revealed satisfactory bone fusion. Arrows depict the cortical integrity of the fusion.

the C1-C2 complex limits cranial rotation capacity by up to 50% with discomfort and pain upon neck motion. Transodontoid screw fixation was first presented by Böhler [5] in 1982. In this technique, C2 is the only vertebra to be involved in the surgical procedure, so there is no anatomical destruction of the upper section of the cervical spine such as in posterior arthrodesis. This fact singles out transodontoid screw fixation as a more physiologic technique in comparison with posterior wiring or transfacet screw fixation techniques. In addition, transodontoid screw fixation offers biomechanical advantages as it preserves the craniocervical junction and cervical motion [15,16]. C1-C2 posterior fixation techniques are preferable if transodontoid screw fixation fails. The major problem with the transodontoid screw fixation technique is the poor outcome in regard to bone fusion in delayed and/orchronic cases. The sclerotic margins of the fractured bones diminish the fusion rate. Two of the delayed cases of our series had nonunion which was operated on via classical transodontoid fixation.

In the technique presented here, fixation of the odontoid via a K-wire is followed by creating multiple (4 or 5) holes in both the C2 body and the odontoid. This will remove at least some part of the sclerotic margins of the fractured part of the upper C2 body and the inferior surface of the odontoid, leading to a higher expected fusion rate. In this limited series of delayed cases, satisfactory bone fusion was observed. Although this technique can result in a weak endurance capacity at the C2 vertebra corpus, this complication was not noted in this limited series. Transodontoid screw fixation offers low mortality and morbidity rates, minimum hospital stay, and easy adaptation to social life. Therefore, it is an appropriate treatment method to be considered in the treatment of type II odontoid fractures. Although the results of our short series (4 cases) are not suitable for statistical comparison, we think that in delayed or chronic cases, this technique could be an alternative to the classical transodontoid fixation technique.

Fig. 5. Patient 3: The sagittal CT scan revealed a dorsally dislocated odontoid fracture (A). The postoperative late-term CT scan showed an odontoid fracture in the natural anatomic location and satisfactory bone healing (B: sagittal; C: coronal).

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Commentary Ozer et al describe a modification to trans-odontoid screw placement for type II odontoid fractures. The technique centers around disruption of the sclerotic bony margins which form in cases of nonunion. The surgical technique of creating an improved vascular bed and exposure of cancellous bone to promote arthrodesis is not new—its application in this specific condition is. Although there may be other techniques to obtain this same objective in the future, this technique is inexpensive and readily applicable. I would caution surgeons that this technique must be performed with careful and continuous observation of the K-wire trajectory and depth.

William C. Welch, MD, FACS, FICS Department of Neurosurgery University of Pennsylvania Philadelphia, PA 19107, USA