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Table of Contents    
Year : 2022  |  Volume : 70  |  Issue : 8  |  Page : 129-134

Single-Stage Posterior Only Approach for Unilateral Atlantoaxial Spondyloptosis with type-II odontoid Fracture in Pediatric Patients

Department of Neurosurgery, All India Institute of Medical Sciences, New Delhi, India

Date of Submission27-Apr-2020
Date of Decision22-Jun-2020
Date of Acceptance10-Jul-2020
Date of Web Publication11-Nov-2022

Correspondence Address:
Pankaj Kumar Singh
Additional Professor, Department of Neurosurgery, Room No. 720, Neurosciences Centre, All India Institute of Medical Sciences, New Delhi - 110 029
Ramesh S Doddamani
Additional Professor Department of Neurosurgery Room No 716, Neuroscience Center All India Institute of Medical Sciences, New Delhi - 110 029
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0028-3886.360918

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 » Abstract 

Objective: When there is a complete slippage of facet joints of C1 over C2 such that there is no contact between the articulating surfaces of C1 and C2, the condition is known as atlantoaxial spondyloptosis (AAS). AAS represents an extremely rare manifestation of atlantoaxial instability. This study was performed to highlight the presentation, radiological features, and management of unilateral AAS in pediatric patients.
Material and Methods: We retrospectively identified four pediatric patients with AAS from our hospital records in the last 6 years (2014–2019).
Results: Among the four patients with unilateral AAS, three were posttraumic and one was diagnosed with craniovertebral junction tuberculosis (CVJ TB). All the patients had a varying degree of spastic quadriparesis on presentation. One patient with CVJ TB presented with neck tilt. All patients with traumatic unilateral AAS were associated with an odontoid fracture. These patients underwent C1-C2 fixation with complete reduction of spondyloptosis using the techniques of joint manipulation and joint remodeling with a posterior only approach. Complete reduction of AAS in patients with trauma was also associated with the realignment of the odontoid fracture. All patients improved neurologically after surgery and achieved excellent correction of the deformity on a follow-up imaging.
Conclusion: Pediatric unilateral AAS is an extremely rare phenomenon. A single-stage posterior approach with C1-C2 fixation is a feasible technique for the treatment of this seemingly difficult to correct deformity in pediatric patients and the clinical outcomes are excellent.

Keywords: DCER, joint manipulation, joint remodeling, posterior approach, odontoid fracture
Key Message: Unilateral AAS is an uncommon condition, usually seen after trauma. These patients can be managed effectively via the posterior approach in a single-stage surgery with C1-C2 fixation using joint manipulation, joint remodeling, and DCER techniques. Using these techniques even the most severe type of deformity (AAS) can be corrected.

How to cite this article:
Varshney G, Kumar A, Doddamani RS, Meena R, Sawarkar DP, Verma S, Singh PK, Gupta D, Satyarthee G, Chandra P S, Kale SS. Single-Stage Posterior Only Approach for Unilateral Atlantoaxial Spondyloptosis with type-II odontoid Fracture in Pediatric Patients. Neurol India 2022;70, Suppl S2:129-34

How to cite this URL:
Varshney G, Kumar A, Doddamani RS, Meena R, Sawarkar DP, Verma S, Singh PK, Gupta D, Satyarthee G, Chandra P S, Kale SS. Single-Stage Posterior Only Approach for Unilateral Atlantoaxial Spondyloptosis with type-II odontoid Fracture in Pediatric Patients. Neurol India [serial online] 2022 [cited 2022 Dec 3];70, Suppl S2:129-34. Available from: https://www.neurologyindia.com/text.asp?2022/70/8/129/360918

Atlantoaxial spondyloptosis (AAS) is a rare radiological diagnosis and it represents an extreme form of atlantoaxial instability. Goel and coworkers defined AAS as complete displacement of facets of atlas anterior to the facets of the axis so that there is no contact between the two articulating surfaces.[1] AAS can be likened to atlantoaxial dislocation (AAD), except that the former represents an extremely severe type of deformity. Besides, AAD is much more common than AAS, more so compared to unilateral AAS. The occurrence of AAS is probably related to the high velocity trauma, representing an extremely severe variety of injury considering the fact that, the ligamentous complex of the atlantoaxial region offers stern resistance to both traumatic forces and infective pathologies. Surgeries of the atlantoaxial region are technically demanding. Achieving complete reduction in severe dislocation (spondyloptosis) of the C1-C2 vertebrae poses a real challenge.[22] Herein, we describe a series of four pediatric cases of unilateral AAS that were managed by a posterior only approach in single-stage. Using the techniques of joint manipulation and joint remodeling with complete correction of deformity and good neurological outcome in all cases. To the best of our knowledge, this is the first series describing unilateral AAS in pediatric patients.

 » Material and Methods Top

We retrospectively retrieved data of pediatric craniovertebral junction (CVJ) deformity operated at our center between 2014–2019 and identified four cases of unilateral AAS. All these cases were operated by using a posterior only approach with C1-C2 fixation. The data were obtained from case files, operation notes, discharge summaries, and follow-up outpatient files. Patient consent was not required as the data was collected from hospital records in a retrospective manner. Patient details are not identifiable from text or the images.

 » Results Top

In this series, four cases (three males and one female) of unilateral AAS in the pediatric age group were operated over a period of 5 years. The mean age of the patients was 11.25 years with a mean duration of symptoms for 7 months (range 4–12 months). Three patients presented with post-traumatic AAS and one was diagnosed with craniovertebral junction tuberculosis (CVJ TB) [Figure 1], [Figure 2], [Figure 3], [Figure 4]. All the patients had varying degree of spastic quadriparesis on examination along with neck pain and restriction of neck movements [Table 1]. One patient also complained of dysphagia to solid foods and the patient with CVJ TB had a history of mastoid abscess for which she was started on antitubercular treatment. None of the patients had bowel or bladder complaints at presentation. Non-contrast computed tomography (CT) scan of the CVJ was performed in all the patients. Unilateral AAS was noted in all the patients (left-sided in three and right-sided in one patient). An associated displaced Type II odontoid fracture was seen in all the cases of posttraumatic AAS. The patient with CVJ TB had a normal odontoid. In all cases, the CT CVJ demonstrated completely dislocated C1 vertebra lying anterior to the anterior aspect of the C2 vertebral body on one side. Consequently, inferior facet of C1 was locked onto the anterior surface of the superior facet of C2 vertebra. In post-traumatic AAS patients with odontoid fracture, the fractured segment of the odontoid was displaced between C1 and C2 in an axial plane [Table 2]. In one patient, owing to the severity of subluxation, C1 anterior arch produced pressure effect on the posterior pharyngeal wall (leading to dysphagia as the presenting feature).
Figure 1: Pre and postoperative non-contrast CT scan of case no. 1. Sagittal section showing left-sided AAS (a) with type II odontoid fracture (b). (c): Right C1-C2 joint. (d-f): Complete reduction of AAS and odontoid fracture in follow-up scan

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Figure 2: Pre and postoperative non-contrast CT scan of Case no. 2. (a-c): Preoperative sagittal view showing unilateral AAS with a type 2 odontoid fracture. (d-f): Postoperative scan showing complete correction of AAS along with the realignment of odontoid fracture

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Figure 3: Pre and postoperative non-contrast CT scan of Case no. 3. (a-c): Preoperative sagittal view showing unilateral AAS with a type 2 odontoid fracture. (d and e): Postoperative scan showing complete correction of AAS. (f): X-ray of the cervical spine at 4-years follow-up showing a stable construct

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Figure 4: (a-c): Preoperative non-contrast CT scan of Case no. 4 showing unilateral AAS. (d): Intraoperative radiograph showing complete correction of the deformity. (e): Postoperative X-ray of cervical spine at 1-year follow-up

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Table 1: Showing details of the individual case along with their neurological and radiological status

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Table 2: Showing surgical procedure and intraoperative details of each case

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All patients were operated by a posterior only approach in a single sitting [Table 3]. Care was taken to prevent undue neck movements while positioning the patients. All patients were positioned prone with a hard-cervical collar in situ. Incremental cranial traction (up to 3–4 kg) was applied in all patients with the help of Gardner Wells tongs. However, traction did not reduce the spondyloptosis in any of the patients, may be due to C1-C2 interlocking. This interlocking also meant that any maneuvering of the C1-C2 vertebrae will not lead to the correction of AAS. To achieve this, the inferior aspect of the C1 arch was drilled revealing the posterior surface of the C1 facet. At this stage in surgery, only the bare superior articular facet of the axis which was posterior to the C1 facet was visible. Due to the extreme degree of listhesis, the articular surfaces of the C1 facets were not visible. Drilling the inferior one-third of C1 facets and opening the C1-C2 joint allowed for maneuvering so that the C1 vertebra could be pulled back over the C2 superior articular facet with the help of an instrument (osteotome). Once satisfactory reduction was achieved, bilateral C1 lateral mass screws followed by bilateral C2 pedicle screws were inserted under image intensifier guidance. Screws were fixed with rods. This along with compression across the rods resulted in a complete reduction of the listhesis. The associated odontoid fracture in these patients got reduced with a reduction of spondyloptosis. The patient with CVJ TB underwent posterior C1-C2 fixation using the DCER (distraction, compression, extension, and reduction) technique. To correct the rotatory component, first, the right C1-C2 joint was opened. Maneuvering the C1-C2 joints did not lead to a reduction in this case. At this stage, both the C1 and C2 facet joints were drilled and C1 was pulled back over C2. Joint spacers were then inserted in bilateral C1-C2 joints followed by C1 lateral mass and C2 pedicle screws insertion under image intensifier guidance. The posterior arch of C1 was removed. Fixation with rods followed by compression leads to the complete correction of left-sided spondyloptosis. For bony fusion, autologous bone chips from iliac crest were used in all cases.
Table 3: Showing postoperative details and follow-up of each case

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All the patients had significant improvement in motor power and spasticity in the immediate postoperative period. None of the patients had any intra/postoperative complications. All patients were prescribed hard cervical collar in the postoperative period for at least 12 weeks. Upon follow-up, further neurological improvement was noted in all the patients. Follow-up CT CVJ was performed in all the patients; excellent correction of deformity and stable construct with bony fusion was noted [Table 3].

 » Discussion Top

The CVJ acts as a transition zone between the cranium (mobile segment) and the spinal column (relatively rigid segment).[23] The atlantoaxial joint represents the most mobile segment of the entire spine with a variety of movements like axial rotation (average 23.3° to 38.9° to either side), flexion, and extension (average 10.1° to 22.4° total) and lateral bending (average 9°).[2],[3],[4],[24],[25] This range of motion is possible owing to the unique characteristics of atlantoaxial joint surfaces (opposing facet joints are almost flat and parallel) and their supporting ligaments. However, mobility comes at a cost, as the chances of developing instability is the highest at CVJ compared to the rest of the spine. Hence, it can be aptly stated here that, “Mobility comes at the cost of instability”. Involvement of CVJ is observed in about one-third to half of all cases of cervical spine injuries.[5],[6] Odontoid fractures account for 10–20% of all cervical spine fractures.[7],[26]

The literature on AAS is sparse and restricted to few case series and reports and very few when only the pediatric age group is considered. Unilateral AAS has not been yet described in the literature. The management of AAS was first described in 2006 by Goel et al.,[1] in a series of four cases. Three of these cases were congenital and one was diagnosed with rheumatoid arthritis, with an age ranging between 12-31 years.[27],[28] None of these patients had any evidence of odontoid fracture. The presentation, however, with spastic quadriparesis, is similar to that observed in our series. Goel et al.[8] later on added two more cases of AAS in 2011, in a series of 14 cases of atlantoaxial facet locking, while the rest of them had rotatory dislocation with unilateral facet locking. Again, none of the patients in this series had an odontoid fracture. Traumatic AAS with associated odontoid fractures were first described by Salunke et al.[9] in a series of six cases. Similar to the delayed presentation of patients in our series, Salunke et al. also noted that the patients only had mild neck pain at the time of trauma and presented with progressive weakness in a delayed manner. Radiologically, all patients in their series had interlocked C1-C2 facets, as was seen with the cases described in this series. We have also previously described a case of AAS with type II odontoid fracture that was surgically managed using the technique of joint remodelling by posterior only approach.[10]

The concepts of joint manipulation, joint remodeling, and DCER were described in the context of AAD and basilar invagination (BI)[1],[11],[12],[13],[14],[15],[16],[17],[18],[19] and since then have been used by various authors to achieve realignment at the craniovertebral junction.[9],[11],[14],[15],[16],[17],[18],[19],[20] Recently, Yadav and collogues have described, anterior only approach for managing cases of AAD using endoscopic transoral route[21]. However, the surgical techniques used in the treatment of cases presented in this series employed posterior only approach with a combination of the above mentioned techniques to achieve excellent deformity correction and good neurological outcomes. Intraoperative C1-C2 distraction and joint manipulation, initially described by Goel et al.,[12],[13] was used to achieve a reduction in three cases described in this series. However, in certain cases, joint manipulation alone may not be sufficient to achieve correction. Hence, the technique of joint drilling and remodeling to render the joint surfaces flat and parallel to each other, has been used to achieve correction in cases of congenital AAD [9],[15]. In the current study, we extrapolated the technique of drilling and remodeling of the facet joints for achieving complete reduction with the help of osteotome inserted between the C1-2 facets. In exceptional circumstances, only partial correction of deformity may be achieved following joint manipulation, however, with C1-2 screw and rod fixation complete reduction and alignment can be achieved. This possible only with comprehensive joint drilling and remodeling.

In case 4, where the patient had a rotatory deformity of the neck due to unilateral AAS, we used the technique of DCER, described by Chandra et al.[14],[15] Using this technique, the C1-C2 joints were opened to allow maneuvering and thereby achieving reduction. Failing to do so both the C1-C2 facets were drilled, joint spacers were inserted in both joints and C1 was pulled back over C2 achieving complete reduction of spondyloptosis.

The successful reduction of the of the AAS leads to alignment of the fractured segments of the odontoid. This can be explained with the fact the transverse atlantal ligament (TAL) remains intact in these cases. AAS can be equated to the locked facets, commonly observed in the subaxial cervical spine and results as a consequence of hyperflexion injury at CVJ. A hyperflexion injury with neck rotation towards one side, results in unilateral AAS analogous to what is described for unilateral locked facets in the subaxial cervical spine. Hence, in these cases both odontoid and the TAL, offer a strong resistance against the occurence of AAS, along with the C1-2 joint capsule. TAL represents among the strongest ligamnets in the human body. While, the odontoid process is relatively weaker at the waist (narrowest portion) and more prone to fracture, specially Type-II Odontoid fracture owing to; i) precarious blood supply as the waist represents the watershed territory ii) narrowest portion of the dens and iii) the stretching forces exerted by the ligaments (alar ligament pulling the dens superiorly, TAL maintaining the integrity of C1- C2 in the axial plane) in multiple directions simultaneously.

Depending upon the direction of dislocation in the axial plane, AAS can be categorized into: 1] Anterior AAS (AAAS) and 2] Posterior AAS (PAAS) for convenience. Technically, AAAS can therefore result from either; fracture of the odontoid or disruption of the TAL. Theoretically, in the presence of disruption of TAL with an intact odontoid process, AAAS should result in severe neurological deficits as the intact odontoid process can lead to severe compression of the spinal cord. However, no such cases have been described in the literature yet. The TAL therefore acts beneficially in these situations by causing type-II odontoid fracture, as evidenced by its displacement anteriorly in unison with the C1 anterior arch, thereby preventing severe neurological damage. Salunke and collegues, have described a series of six cases with PAAS and a fractured dense, once again reiterating the fact that odontoid is weaker at the waist. They noted the disruption of the anterior longitudinal ligament in three of their cases further supplementing the development of PAAS [17]. Therefore, complete reduction of the C1-2 facets, automatically aligns the fractured odontoid segments with a posterior only approach without requiring an additional procedure.

As observed in various studies published, cranial traction was not effective in reducing the dislocation due to C1-C2 interlocking in our series as well. It is only when the C1-C2 joints were opened (manipulated) and/or drilled (remodeled) that reduction was achieved (partial/complete). This reduction was strengthened and maintained with the help of C1-C2 screw rod fixation and compression which also helped to reduce the spondyloptosis in cases where it was only partially correct. We achieved excellent outcomes in all the four cases, both in terms of clinical improvement in the patients and radiological complete reduction of spondyloptosis. Limitations remain to be the retrospective nature of our study, apart from the absence of CT angiography in few cases.

 » Conclusion Top

AAS is a rare entity with trauma to the CVJ representing the commonest cause. Bilateral AAS appears to be more common compared to the unilateral variety and are analogous to the locked facets commonly encountered in the sub axial cervical spine. It can be classified into anterior and posterior AAS depending upon the direction of subluxation in the axial plane, of C1 either anteriorly or posteriorly over C2 respectively. AAS irrespective of the variety is usually seen in association with type – II odontoid fracture, especially in post-traumatic cases. The integrity of the TAL plays a vital role in the realignment of the fractured odontoid, when posterior only approach is used to manage these challenging cases.

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Conflicts of interest

There are no conflicts of interest.

 » References Top

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  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

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