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Os Odontoideum: Analysis of 190 Surgically Treated Cases
Journal Pre-proof Os-odontoideum: Analysis of 190 surgically treated cases Atul Goel, M.Ch, Neurosurgery, Abhinandan Patil, M.Ch, Neurosurgery, Abhidha Shah, M.Ch, Neurosurgery, Saswat Dandpat, M.Ch, Neurosurgery, Survendra Rai, M.Ch, Neurosurgery, Shashi Ranjan, M.Ch, Neurosurgery PII:
S1878-8750(19)32735-4
DOI:
https://doi.org/10.1016/j.wneu.2019.10.107
Reference:
WNEU 13578
To appear in:
World Neurosurgery
Received Date: 7 September 2019 Revised Date:
17 October 2019
Accepted Date: 18 October 2019
Please cite this article as: Goel A, Patil A, Shah A, Dandpat S, Rai S, Ranjan S, Os-odontoideum: Analysis of 190 surgically treated cases, World Neurosurgery (2019), doi: https://doi.org/10.1016/ j.wneu.2019.10.107. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Inc.
Os-odontoideum: Analysis of 190 surgically treated cases
1. Atul Goel M.Ch. Neurosurgery Professor and Head of Department, Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel, Mumbai. and Consultant Neurosurgeon, Lilavati Hospital and Research Centre, Bandra (E), Mumbai. 2. Abhinandan Patil M.Ch. Neurosurgery Senior Resident, Department of Neurosurgery, , Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel, Mumbai. 3. Abhidha Shah M.Ch. Neurosurgery Assistant Professor, Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel, Mumbai. 4. Saswat Dandpat M.Ch. Neurosurgery Senior Resident, Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel, Mumbai. 5. Survendra Rai M.Ch. Neurosurgery Assistant Professor, Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel, Mumbai. 6. Shashi Ranjan M.Ch. Neurosurgery Senior Resident, Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel, Mumbai.
Correspondence: Prof. Atul Goel, Head of Department, Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel, Mumbai400012, India Telephone no: 22-24129884 Fax no: 22-24143435 E-mail: [email protected]
Conflict of Interest: None Disclosure of Funding; None
1
Os-odontoideum: Analysis of 190 surgically treated cases
2 3
Background: The management of os-odontoideum is analyzed on the basis of
4
approximately 20 years of experience.
5 6
Objective: This is a report of an experience with 190 cases having os-odontoideum.
7
The management outcome following atlantoaxial fixation is analyzed.
8 9
Material and methods: During the period January 2000 to September 2018, 190
10
patients having os-odontoideum were surgically treated. There were 113 males and 77
11
females and their ages ranged from 2 to 68 years (average 24 years).The patients were
12
divided into three groups depending on the nature of atlantoaxial dislocation (Group
13
1- mobile and partially or completely reducible atlantoaxial dislocation, Group 2-
14
fixed or irreducible atlantoaxial dislocation and Group 3- presence of basilar
15
invagination). Sixty- five patients were in pediatric age group (less than 18 years). All
16
patients underwent atlantoaxial joint manipulation and lateral mass plate and screw
17
fixation. The operation was aimed at segmental atlantoaxial arthrodesis. No transoral
18
or posterior foramen magnum bone decompression was done. Occipital bone was not
19
included in the fixation construct.
20 21
Results: On direct bone handling and observation, atlantoaxial joint pathological
22
hyperactivity related instability was identified in all patients. Atlantoaxial segmental
23
stabilization resulted in clinical symptomatic and neurological improvement in 100
24
percent patients.
25
1
1
Conclusions: Os-odontoideum signifies chronic or longstanding atlantoaxial
2
instability. Segmental atlantoaxial fixation is a reliable form of surgical treatment.
3
Any form of bone decompression is not necessary. Inclusion of occipital bone and
4
subaxial vertebrae in the fixation construct is not necessary.
5 6
Key-words: os-odontoideum, atlantoaxial instability, basilar invagination,
7
atlantoaxial fixation
8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
2
1
Os-odontoideum: Analysis of 190 surgically treated cases
2 3
Introduction:
4
Since its original description in 1886, os-odontoideum has been a well-defined and
5
frequently discussed abnormality of the odontoid process.1 Despite the fact that the
6
entity has been under discussion for approximately one and a half century, it may not
7
be incorrect to state that the pathogenesis remains unclear and the treatment protocol
8
has not yet been standardized. On the basis of largest personal series in the literature
9
till date, we discuss management of 190 cases having os-odontoideum. In the series,
10
we identify a hitherto unreported clinical entity of retro-C2-body cystic degeneration
11
associated with localized erosion of the bone of the C2 body in 28 cases. All patients
12
were successfully treated by atlantoaxial arthrodesis using lateral mass plate and
13
screw metal fixation technique.2,3
14 15
Material and Methods:
16
From January 2000 to September 2018, neurosurgery operation theatre database of
17
authors institutes included 2400 cases with craniovertebral junction instability that
18
were treated by atlantoaxial fixation. Of these, 190 patients had os-odontoideum.
19
These consecutive cases have been studied retrospectively. All the patients provided
20
written informed consent before surgery, and all clinical tests and surgical procedures
21
were conducted according to principles of Declaration of Helsinki. As the study is a
22
retrospective analysis of data and previously published surgical techniques were
23
deployed, ethics committee permission was not deemed necessary. Cases treated by
24
the senior author before the year 2000 have not been included in the study as the
25
clinical and radiological data is not entirely available and the treatment protocol
3
1
adopted was not uniformly similar to that presented in this report. As complete
2
odontoid process separation from the body of axis vertebra was only rarely
3
encountered, os-odontoideum was described as cases wherein a ‘significant’ or at-
4
least half of the odontoid process separated from the rest of the odontoid process-body
5
of axis complex. There was a clear and smooth demarcation of the separated part of
6
the odontoid process from either the rest of the odontoid process or from the body of
7
the axis. Patients treated conservatively or without surgery and evaluated only on
8
outpatient basis were not included. To describe and characterize the cases, the patients
9
were divided into 3 groups, depending on the nature of atlantoaxial instability and
10
presence of basilar invagination. Mobility of atlantoaxial dislocation was assessed on
11
dynamic lateral profile imaging (plain radiographs or sagittal CT scan) with the head
12
in flexed and extended positions. Despite the absence of odontoid tip as a landmark of
13
measurement, basilar invagination was assessed by the classically described
14
parameter of Chamberlain’s line.4,5 Group 1 included 116 cases where there was
15
partially or completely reducible atlantoaxial dislocation. (Figures 1 and 2) Group 2
16
included 51 cases where the atlantoaxial dislocation was fixed or irreducible in nature.
17
(Figures 3, 4) Group 3 included 23 cases where there was basilar invagination.
18
(Figure 5) (Table 1) Four patients had Down’s syndrome. Three patients including
19
two siblings, a 15 year old boy and an 18 year old girl had Morquio’s syndrome. No
20
other patient had any defined genetic or known syndromic abnormality. Two
21
additional patients belonged to the same family (daughter 25 years old and father 51
22
years old). There was no genetic abnormality in both of these patients. Ten patients
23
with os-odontoideum who had been operated earlier elsewhere were reoperated for
24
failed craniovertebral fixation surgical procedure done earlier. All of these patients
25
had Group 2 type of os-odontoideum.
4
1 2
Clinical profile: The clinical profile of the patients is summarized in Tables 2-5. Goel
3
clinical grading scale6, the Japanese Orthopedic Association7and Visual Analog Scale
4
(VAS)8 scoring systems were used to clinically evaluate the patients both before and
5
after the surgical treatment and at follow-up.
6 7
Radiological analysis: All patients underwent preoperative dynamic plain radiographs
8
and CT scan with the head in flexed and extended positions and MRI of the
9
craniovertebral junction. The bone anomalies observed in these patients are depicted
10
in Table 6. In all cases, dynamic imaging showed that during head movements the
11
odontoid process was firmly aligned to the clivus in the region of apical ligament and
12
to the anterior arch of atlas and did not move relative to movements of other
13
components of axis. The alteration in the craniocervical angulation varied in the
14
groups and is shown in Table 7. The angulation of the articular surface of facet of
15
atlas from the horizontal (in neutral head position) is detailed in Table 7.
16
Neural alterations included Chiari formation (11 patients) and syringomyelia (15
17
patients).Enlargement of the subaxial spinal subarachnoid space (external
18
syringomyelia), enlargement of spinal canal dimension and reduction of spinal cord
19
girth was identified in 96 patients.
20
A cyst-like formation, simulating ‘retroodontoid cyst’ was identified in the superior
21
and posterior aspect of the body of axis in 28 patients. (Figures 2, 6 and 7) The cyst
22
was labelled as ‘retro-C2-body’ cyst. The posterior aspect of the C2 vertebral body
23
adjoining the cyst had well defined bone erosion (as shown in the figures 2, 6 and 7)
24
in all cases. In cases where there was ‘retro-C2-body’ cyst, 18 patients had Group 1
25
os-odontoideum and 10 patients had Group 2 os-odontoideum.
5
1
Operative procedure: All patients underwent surgery with atlantoaxial lateral mass
2
plate/rod and screw fixation with the techniques described by the first author in 1994
3
and 2004.2,3 The basic surgical steps in all the three groups of patients involved
4
opening of the atlantoaxial articulation, manipulation and distraction of the facets,
5
denuding the articular capsule, packing of bone graft (harvested from iliac crest)
6
within the joint cavity and direct plate/rod and screw fixation of the lateral masses of
7
atlas and axis. Muscle attached to the posterior elements of atlas and axis was sharply
8
cut. Bone graft was additionally placed in the posterior midline after appropriately
9
preparing the host bone by drilling of its outer cortex. In the early part of the series, in
10
11 patients (4 patients were in Group 1, 5 patients were in Group 2 and 2 patients
11
were in Group 3) in addition to bone graft intra-articular metallic spacers were used to
12
distract the facets for the purpose of craniovertebral realignment and firm
13
stabilization.9,10 In subsequent cases, intrarticular metal implant was not used. No
14
foramen magnum bone decompression was done.
15 16
The constant observation was that there was clear evidence of atlantoaxial instability
17
on direct manipulation of the bones of the region in all three groups of patients. The
18
instability was identified on direct observation of the facets and articulation
19
irrespective of whether it was observed or not on preoperative dynamic radiological
20
imaging. In all cases the articular cartilage was well formed and the joints were
21
seemingly functionally active. In a number of cases, the articular cartilage extended
22
beyond the facets of atlas and axis over the pedicle of the axis bone. In cases with
23
bifid posterior arch of atlas, the facets of atlas were remarkably mobile and located
24
laterally in relationship with the facet of axis. The vertebral artery was ‘high-riding’
25
in the superior facet of axis in 55 cases.
6
1
The patients were advised to wear a firm external cervical collar for a period of 3
2
months after surgery and all neck activities and movements were restricted. After this
3
period all movements were permitted. The follow-up ranged from 6 to 218 months
4
(average 64 months).Postoperative CT scan was obtained within 24 hours of surgery,
5
3 months after surgery and at subsequent follow-up.
6 7
Results:
8
Tables 3 - 5 show the clinical outcome after at-least 6 months of surgery. All patients
9
improved in varying degrees in their clinical symptoms and neurological status. The
10
alterations in craniocervical angulation following surgery are shown in Table 7.
11
Delayed imaging (after one year of surgery) was available for review in 125 patients
12
showed evidence of bone fusion in all cases in the region of the facets and in the
13
posterior midline. There were no significant infection or implant related
14
complications. There were no implant failures or evidences of recurrent atlantoaxial
15
instability that forced reoperation.
16 17
Discussion:
18
Giacomini first described os-odontoideum in 1886.1By original definition; it refers to
19
an independent odontoid process bone that is separated from its base at the site of
20
attachment to the body of axis. Our analysis identifies that odontoid process
21
separation is more often not exactly at the probable site of junction of the odontoid
22
process with the body of axis. We identified os-odontoideum as a condition where a
23
‘significant’ or approximately atleast half of the presumed odontoid process separated
24
from the rest of the odontoid process and body of C2.The separated part of the
25
odontoid process has a smooth inferior border and has no anatomic continuity or
7
1
functional congruence with the remaining part of the odontoid process or the body of
2
axis. Os-odontoideum can sometimes mimic trauma related fracture at the base of the
3
odontoid process. Irregular edges of the fractured segments and a history of
4
significant trauma help distinguish fracture of odontoid process from os-odontoideum.
5
Os-terminale, ossification or osteophyte formation in the region of apical ligament are
6
other odontoid process related abnormalities.
7 8
Pathogenesis:
9
The pathogenesis of os-odontoideum is unclear and has been a debated issue. Genetic
10
abnormality and faulty embryogenesis has been suggested as a cause considering the
11
identification in some twin cases and in cases with Down’s and Morquio’s
12
syndrome.11-14 In our series there were two adults (father and daughter) without any
13
identified genetic abnormality and two siblings diagnosed to have Morquio’s disease.
14
The post-traumatic theory is the more prevailing theory.15-18 McRae believed that os-
15
odontoideum has embryological origin, but required the ongoing stresses of life to
16
trigger instability and produce symptoms after childhood.19 Os-odontoideum seems to
17
be a secondary phenomenon to primary longstanding atlantoaxial instability. The
18
presenting clinical symptoms are relatively mild, despite the evidences of significant
19
structural abnormality and neural deformation. This is probably related to a number of
20
natural protective measures that are in play.20,21 Bifid arches of atlas were seen in 37
21
cases.21 In our earlier analysis of 70 cases we identified that bifid arch of atlas had an
22
open-close door kind of movements. Head flexion that results in critical posterior
23
movement of the odontoid process is associated with opening of the door or widening
24
of the bifid of the posterior arch, whilst in extension of the head the door closes. We
25
likened bifid posterior arch to be a form of natural ‘decompressive laminectomy’.21As
8
1
discussed in our earlier publication, the articular surface of the facet of atlas was
2
rotated medially and the facet of atlas was dislocated lateral in relationship to the
3
facet of axis in a number of cases having bifid atlas.21 It was observed that these
4
morphological alterations were related to longstanding atlantoaxial instability and the
5
processes were designed to increase the transverse and decrease the vertical
6
dimensions of the spinal canal at the level of atlas. It was earlier identified that the
7
presence of syringomyelia, Chiari formation, external syringomyelia and external
8
syringobulbia, enlargement of cervical and dorsal spinal canal dimension, reduction in
9
spinal cord girth are natural secondary ‘protective’ events to primary atlantoaxial
10
instability.22-24 Considering that a number of these secondary neural and
11
musculoskeletal malformations are associated with os-odontoideum, it does appear
12
that os-odontoideum is by itself a secondary event to primary atlantoaxial instability.
13
It seemed that both os-odontoideum and bifid arch of atlas are essentially natural bone
14
transformations that are protective endeavours to save the cord from compression
15
between bones in the presence of potential or manifest atlantoaxial instability.
16 17
Clinical presentation:
18
Subtlety and long-standing nature and relatively mild to moderate intensity of
19
symptoms are the hallmarks, despite the radiological observation of marked instability
20
and related cord deformation or compression. Os-odontoideum may be identified
21
incidentally and the symptoms in these cases are seemingly unrelated to the odontoid
22
abnormality. In 19 patients the symptoms were relatively acute while in the rest 171
23
the symptoms were longstanding, average duration of symptoms ranged from 7 days
24
to 96 months. Neck pain (190 patients) and torticollis (23 patients) were prominent
25
symptoms. Ataxia, limb weakness, restricted neck movement, swallowing difficulties,
9
1
hoarseness of voice were the other presenting symptoms (Table 2). Symptoms related
2
to vertebral artery compromise have also been reported, but were not encountered in
3
our series. Mild to severe trauma precipitated neurological symptoms in 69 patients.
4 5
Indicators of instability:
6
Radiological evidence of movement of the odontoid ossicle and anterior arch of C1 on
7
dynamic films relative to the odontoid process-body of C2 forms a significant
8
evidence of instability.25,26 Presence of altered cord signals and evidence of cord
9
‘atrophy’ on MRI in relationship to the residual odontoid process-superior edge of the
10
body of C2 are indicators of instability.27 On flexion of the head, the body of C2
11
frequently travels anterior to its normal location and lays inferior to the anterior arch
12
of atlas. Thus the motion dynamics may vary in each individual patient with os-
13
odontoideum. As identified by us in an earlier report presence of bifid arch of atlas
14
and os-odontoideum is associated with lateral atlantoaxial facetal displacement or
15
dislocation.21 In at-least 23 cases there was additional evidence of rotatory atlantoaxial
16
dislocation. This multidirectional instability at the articulation between the atlas and
17
the axis is suggestive of defective or ineffective cruciate and capsular ligaments. Our
18
recent studies on the subject suggest that the atlantoaxial instability can also be
19
identified by their facetal alignment on lateral profile imaging with the head in neutral
20
position and direct observation and handling of bones of the region and assessment of
21
the status of the atlantoaxial joint during the surgical procedure.28 In general, in
22
younger patients, the atlantoaxial instability was more marked and reducible on
23
dynamic movements than in older patients where the instability tended to be of fixed
24
variety and basilar invagination was frequent.
10
1
It was observed that the atlantoaxial joints were functional and were pathologically
2
‘hyperactive’ in all cases, including those where the dynamic radiological images
3
were suggestive of ‘fixed’ atlantoaxial dislocation. More importantly, the facets of the
4
atlas and axis could be manually distracted and attempts could be made towards
5
restoration of craniovertebral junction alignment. Irrespective of the presence or
6
absence of radiologically demonstrable atlantoaxial instability or facetal mal-
7
alignment, os-odontoideum was by itself an indicator of atlantoaxial instability.
8 9
In 28 patients there was a cyst-like formation posterior to the superior aspect of the
10
body of axis. This cyst simulated retrodoontoid cyst formation, another feature that
11
was associated by us earlier with chronic atlantoaxial instability.29,30 Radiological
12
observation of presence of osteophytes in the vicinity of the os-odontoideum in at-
13
least 21 cases is also an indication of chronicity of the entire process. However, no
14
confirmation of histological nature was possible as these cysts were not directly dealt
15
with during surgery.
16 17
Indications of surgery:
18
On the basis of the understanding, that os-odontoideum is a manifestation of
19
atlantoaxial instability, in general, surgery is indicated for all patients. Presence of
20
pain in the nape of neck was by itself an indicator of instability and forms an
21
indication of surgery. Presence of any neurological symptom or deficit is a definitive
22
indication for surgical intervention. Considering the relative safety of the current
23
technical procedures, surgery can be indicated even in an incidentally detected os-
24
odontoideum. However, in such cases decision regarding the need for surgery will
11
1
have to be based on the clinical situation and the surgical experience of the treating
2
surgeon.
3 4
Surgical technique:
5
We have observed that Goel technique of C1 lateral mass and C2 fixation provides a
6
biomechanically firm and rigid internal fixation.2,3 The possibility of denuding of the
7
articular cartilage of the atlantoaxial joint, stuffing of bone graft within the joint and
8
of joint manipulation to reduce dislocation, makes this technique versatile. Individual
9
placement of screws in C1 and C2 lateral mass makes the procedure safer as regards
10
the vertebral artery. ‘High riding’ vertebral artery was identified in 55 cases (28.9 %).
11
This high incidence was significantly more when compared to the generally observed
12
incidence of high-riding vertebral artery. It is crucial to identify such a location of
13
vertebral artery and direct the screw in the pars-pedicle-facet of axis in a precise and
14
safe manner. More recently, we expose the vertebral artery after drilling the thin bone
15
shell that usually covers the posterior aspect of the arterial loop and mobilize it
16
laterally or inferiorly. This modified technique allowed safe insertion of the screw
17
into the facet of axis with the vertebral artery under direct surgical
18
vision.31Atlantoaxial stabilization using our technique resulted in biomechanically
19
strong fixation that ultimately led to arthrodesis of the unstable spinal segment. We
20
could achieve 100% bone fusion and all patients showed symptomatic and clinical
21
neurological recovery. The very fact that all patients in the series had symptomatic
22
recovery, no patient in the entire series over the study period of 20 years has needed
23
reoperation for any indication including implant failure or has suffered delayed
24
neurological worsening is a testimony to success of the surgical technique and
25
validity of atlantoaxial fixation as a surgical procedure. Our belief is that more than
12
1
neural deformation or evidences of compression, it is subtle instability related micro-
2
injuries to the cord that causes symptoms. Although complete reduction of the
3
atlantoaxial dislocation is preferable, strong stabilization of the atlantoaxial joint with
4
the aim to achieve arthrodesis is of prime significance and the goal of surgery and can
5
result in quick resolution of symptoms.
6
‘Fixed’ atlantoaxial dislocation with or without basilar invagination was identified in
7
74 cases. A number of factors have been implicated to result in ‘fixed’ dislocation.
8
Impaction of the transverse ligament between the odontoid process and the body of
9
the C2 has been implicated in the development of fixed atlantoaxial dislocation.32We
10
observed that in cases with fixed atlantoaxial instability (Group 2) and basilar
11
invagination (Group 3), the angulation of the facet of atlas was significantly acute in
12
relationship with the facet of axis when compared to cases where the atlantoaxial
13
instability was completely (Group 1) or partially reducible (Group 1). While
14
deploying our technique of atlantoaxial joint manipulation, distraction and reduction
15
of the dislocation, we observed that the joint in these cases is not only, not ‘fixed’, but
16
is mobile and pathologically hyperactive. Subtle and persistent abnormal movements
17
at this joint are the probable causes of clinical symptoms.12 In 11 early cases, titanium
18
metal spacer was used to distract the facets to reinforce stabilization and to achieve
19
reduction of the atlantoaxial dislocation and basilar invagination. However, in the
20
subsequent cases, only bone graft was impacted into the joint space and no metal
21
implant was used. Avoidance of metal implant allowed insertion of more bone graft
22
within the articular cavity and permitted an enhanced opportunity for arthrodesis of
23
the joint. As described by us earlier, the technique of craniovertebral junction
24
‘realignment’ was attempted in Group 2 and 3 cases by atlantoaxial joint
25
manipulation and distraction of facets of atlas and axis by deploying intra-articular
13
1
bone graft with or without metal implant.5,9 Despite the fact that realignment of the
2
craniovertebral junction was targeted, firm atlantoaxial athrodesis was the primary
3
aim of the surgical procedure. Decompression of the craniovertebral region by
4
anterior transoral route or by posterior foramen magnum decompression was not done
5
in the entire series and was considered against the aim of achievement of bone
6
arthodesis. Although important, the impact of craniovertebral stabilization and
7
realignment on subaxial cervical spine in general and spinal sagittal balance in
8
particular was not evaluated. Several authors have advocated the need for inclusion of
9
the occipital bone in the fixation construct.32 Menezes in his recent article has
10
identified the presence of occipito-atlantal instability in some patients having os-
11
odontoideum.33 Our analysis confirms that os-odontoideum is associated with
12
atlantoaxial instability and atlantoaxial stabilization forms the core of surgical
13
treatment. Occipitocervical fixation is unnecessary. It appears that inclusion of the
14
occipital bone in the fixation construct when it is not necessary or when it can be
15
avoided can result in disabling restriction of neck/head movements. Inclusion of
16
normal occipitoatlantal joint and subaxial spinal segments in the fixation construct
17
without directly disabling the joint by removal of articular cartilage can lead to
18
difficulty in providing movement-free construct that will allow bone fusion. Despite
19
the fact that the senior author was amongst the initial surgeons that discussed the use
20
of occipital screws for occipitocervical fixation3, we do not recommend
21
occipitocervical fixation for atlantoaxial instability. Moreover, occipital bone forms a
22
thin and poor host region for stable screw purchase.
14
1
Conclusions:
2
Presence of os-odontoideum is a definite indicator of atlantoaxial instability.
3
Atlantoaxial stabilization is the treatment.
4
References:
5 6 7 8
1. Giacomini C: Sull’ esistenza dell’ “osodontoideum” nell’ uomo. Gior Accad Med Torino.1886; 49:24-28. 2. Goel A, Desai K, Muzumdar D: Atlantoaxial fixation using plate and screw
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method: A report of 160 treated patients. Neurosurgery. 2002;51:1351-1357.
10
3. Goel A, Laheri VK: Plate and screw fixation for atlanto-axial dislocation.
11 12 13 14 15 16
(Technical report). ActaNeurochir (Wien). 1994;129:47-53. 4. Goel A, Bhatjiwale M, Desai K: Basilar invagination: a study based on 190 surgically treated cases. J Neurosurg. 1998;88:962-968. 5. Goel A: Basilar invagination: Treatment by atlantoaxial joint distraction and direct lateral mass fixation. J Neurosurg Spine. 2004;1(3):281-6. 6. Goel A: Chiari malformation – Is atlantoaxial instability the cause? Outcome
17
analysis of 65 patients with Chiari malformation treated by atlantoaxial
18
fixation. J Neurosurg Spine 2015;22 (2): 116-127.
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7. Fujiwara A, Kobayashi N, Saiki K, Kitagawa T, Tamai K, Saotome K.
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Association of the Japanese Orthopaedic Association score with the Oswestry
21
Disability Index, Roland-Morris Disability Questionnaire, and short-form 36.
22
Spine (Phila Pa 1976)2003; 28:1601–7.
23
8. Huskisson EC: Measurement of pain. J Rheumatol1982; 9: 768-769.
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9. Goel A: Atlantoaxial joint jamming as a treatment for atlantoaxial dislocation: a
25
preliminary report. Technical note J Neurosurg Spine 2007; 7(1):90-94. 15
1
10. Goel A, Kulkarni AG, Sharma P: Reduction of fixed atlantoaxial dislocation
2
in 24 cases: technical note. J Neurosurg Spine. 2005;2(4):505-9.
3
11. Dai L, Yuan W, Ni B, et al. Osodontoideum: etiology, diagnosis, and
4 5 6 7 8
management. Surg Neurol.2000;53:106–9. 12. Morgan MK, Onofrio BM, Bender CE. Familial osodontoideum: a case report. J Neurosurg.1989;70:636–9. 13. Kirlew KA, Hathout GM, Reiter SD, et al. Osodontoideum in identical twins: perspectives on etiology. Skeletal Radiol.1993;22:525–7.
9
14. Tang X, Tan M, Yi P, Yang F, Hao Q. Atlantoaxial dislocation and
10
osodontoideum in two identical twins: perspectives on etiology. Eur Spine J.
11
2018 ;27(Suppl 3):259-263.
12 13 14 15 16 17 18 19 20 21 22
15. Fielding JW, Hensinger RN, Hawkins RJ: Os odontoideum. J Bone Joint Surg (Am) 62. 1980:376-383. 16. Schuler TC, Kurz L, Thompson DE, et al. Natural history of os odontoideum: a case report. J Pediatr Orthop.1991;11:222. 17. Stillwell WT, Fielding JW. Acquired os odontoideum: a case report. Clin Orthop.1978;135:71. 18. Wollin DG. The os odontoideum: separate odontoid process. J Bone Joint Surg Am.1963;45:1459–71. 19. McRae DL: The significance of abnormalities of the cervical spine. AJR. 1960;84:3-25. 20. Goel A, Shah A. Reversal of longstanding musculoskeletal changes in basilar
23
invagination after surgical decompression and stabilization. J Neurosurg Spine
24
2009;10:220-7.
16
1
21. Goel A, Nadkarni T, Shah A, Ramdasi R, Patni N. Bifid Anterior and
2
Posterior Arches of Atlas: Surgical Implication and Analysis of 70 Cases.
3
Neurosurgery. 2015;77(2):296-305; discussion 305-6.
4
22. Goel A, Nadkarni T, Shah A, Sathe P, Patil M. Radiological evaluation of
5
Basilar invagination without obvious atlantoaxial instability (Group B-basilar
6
invagination): An analysis based on a study of 75 patients. World Neurosurg
7
2015; 95: 375-382.
8 9 10
23. Goel A, Sathe P, Shah A. Atlantoaxial fixation for Basilar invagination without obvious atlantoaxial instability (Group B-basilar invagination): Outcome analysis of 63 surgically treated cases. World Neurosurg 2017; 99:164-170.
11
24. Goel A, Jain S, Shah A. Radiological Evaluation of 510 Cases of Basilar
12
Invagination with Evidence of Atlantoaxial Instability (Group A Basilar
13
Invagination). World Neurosurg. 2018;110:533-543.
14
25. Goel A. Treatment of odontoid fractures. Neurol India. 2015;63(1):7-8.
15
26. Goel A, Jain S, Shah A, Patil A, Vutha R, Ranjan S, More S. Atlantoaxial
16
Fixation for Odontoid Fracture: Analysis of 124 Surgically Treated Cases.
17
World Neurosurg. 2018;110:558-567.
18 19 20 21 22 23 24 25
27. Goel A. Is focal spinal cord "atrophy" an evidence of chronic spinalinstability? J Craniovertebr Junction Spine. 2017;8(4):295-296. 28. Goel A: Goel’s classification of atlantoaxial “facetal” dislocation. J Craniovertebr Junction Spine2014;5 (1): 3-8. 29. Goel A. Retro-odontoid mass: An evidence of craniovertebral instability. J Craniovertebr Junction Spine. 2015;6(1):6-7. 30. Shah A, Jain S, Kaswa A, Goel A. Immediate Postoperative Disappearance of Retro-Odontoid "Pseudotumor". World Neurosurg. 2016;91:419-23. 17
1
31. Goel A, Rangnekar R, Shah A, Rai S, Vutha R. Mobilization of the vertebral
2
artery- surgical option for C2 screw fixation in cases with ‘high riding’
3
vertebral artery. Operative Neurosurgery (Accepted in press)
4
32. Wu X, Wood KB, Gao Y, Li S, Wang J, Ge T, Zhao B, Shao Z, Yang S, Yang
5
C.Surgical strategies for the treatment of osodontoideum with atlantoaxial
6
dislocation. J Neurosurg Spine. 2018;28(2):131-139.
7
33. Dlouhy BJ, Policeni BA, Menezes AH. Reduction of atlantoaxial dislocation
8
prevented by pathological position of the transverse ligament in
9
fixed,irreducibleosodontoideum: operative illustrations and radiographic
10
correlates in 41 patients. J Neurosurg Spine. 2017;27(1):20-28.
11 12
Figure Legends:
13
Figure 1: Images of a 14 year old boy
14
Figure 1a: T2-weighted MRI shows os-odontoideum. Cord compression can be seen.
15
Figure 1b: CT scan with the head in flexed position shows os-odontoideum.
16
Atlantoaxial instability can be seen.
17
Figure 1c: CT scan with the head in extension position shows reduction of
18
atlantoaxial dislocation.
19
Figure 1d: CT scan with the cut passing through the facets. It shows Type 1
20
atlantoaxial facetal instability. High-rising vertebral artery can be seen.
21
Figure 1e: Postoperative image showing fixation in aligned position.
22
Figure 1f: Postoperative CT scan showing the metal implant with plate and screws in
23
the facets of atlas and axis.
24
Figure 1g: Postoperative CT scan after 24 months of surgery shows bone fusion in the
25
region.
18
1
Figure 1h: Fusion of the facets can be seen.
2 3
Figure 2: Images of a 42 year old female
4
Figure 2a: T2-weighted MRI showing os-odontoideum and evidences of cord
5
compression. A retro-C2 body cyst can be seen.
6
Figure 2b: CT scan with the head in flexed position showing os-odontoideum and
7
atlantoaxial instability. Bone erosion can be seen in the region of retro-C2 body cyst.
8
Figure 2c: CT scan with the head in extension showing reduction of the atlantoaxial
9
instability.
10
Figure 2d: CT scan with the cut passing through the facets. Osteophytes can be seen
11
in the vicinity of facets.
12
Figure 2e: Postoperative CT scan showing the fixation in aligned position.
13
Figure 2f: CT scanwith the cut passing through the facets showing the implant.
14 15
Figure 3: Images of a 14 year old boy
16
Figure 3a: T2-weighted MRI showing os-odontoideum and atlantoaxial instability.
17
Syringomyelia can be seen.
18
Figure 3b: CT scan with the head in flexed position showing atlantoaxial instability.
19
Figure 3c: CT scan with the head in extended position. Reduction of the dislocation is
20
not seen (Group 2 os-odontoideum).
21
Figure 3d: Postoperative CT scan showing reduction of the dislocation.
22
Figure 3e: Postoperative CT scan showing the implant.
23 24
Figure 4: Images of a 14 year old girl
19
1
Figure 4a: T2-weighted MRI showing os-odontoideum and related atlantoaxial
2
instability and cord compression.
3
Figure 4b: CT scan with the head in flexed position showing atlantoaxial instability.
4
Figure 4c: CT scan with the head in extended position showing no reduction of the
5
dislocation.
6
Figure 4d: 3-D CT scan showing presence of bifid posterior arch of atlas.
7
Figure 4e: Postoperative CT scan showing fixation in aligned position.
8
Figure 4f: CT scan showing the implant. Note the high-vertebral artery.
9 10
Figure 5: Images of a 17 year old boy
11
Figure 5a: T2-weighted MRI showing os-odontoideum with basilar invagination
12
(Group 3 os-odontoideum).
13
Figure 5b: CT scan with the head in flexion showing os-odontoideum with basilar
14
invagination.
15
Figure 5c: Postoperative CT scan showing reduction of basilar invagination and
16
fixation in aligned position.
17
Figure 5d: CT scan with the cut through the facets showing the implant.
18 19
Figure 6: Images of a 42 year old male patient.
20
Figure 6a: T2-weighted MRI showing os-odontoideum and cord compression.A retro-
21
C2 body cyst can be seen
22
Figure 6b: Axial image showing the retro C2 body cyst.
23
Figure 6c: CT scan showing os-odontoideum and atlantoaxial instability. Bony
24
erosions on the posterior aspect of body of C2 can be seen.
25
Figure 6d: CT scan showing the alignment of facets.
20
1
Figure 6e: Post-operative MRI showing resolution of the retro C2 body cyst.
2
Figure 6f: Axial image showing resolution of the cyst.
3
Figure 6g: Postoperative CT scan showing fixation in aligned position.
4
Figure 6h: Postoperative CT scan showing the implant.
5 6
Figure 7: Images of a 38 year old female patient
7
Figure 7a: T2-weighted MRI showing os-odontoideum, atlantoaxial instability and
8
cord compression. A small cyst located in the posterior aspect of the C2 vertebral
9
body.
10
Figure 7b: CT scan with the head in flexion showing os-odontoideum and atlantoaxial
11
instability. A relatively small bone erosion in the posterior aspect of C2 body is seen.
12
Figure 7c: Postoperative scan showing fixation in alignment.
13
Figure 7d: Postoperative scan with the cut passing through the facets showing the
14
implant.
15
Figure 7e: Postoperative scan after 16 months of surgery showing fusion of the
16
posterior elements.
17
Figure 7f: Scan showing fusion of the facets.
18 19
Table Legends:
20
Table 1: Classification of os odontoideum
21
Table 2: Table showing the presenting signs and symptoms
22
Table 3: Distribution as per clinical grading system.
23
Table 4: Grading of myelopathy by the Japanese Orthopedic Association Score
24
Table 5: Visual Analog scale (0 – no pain, 10- maximum pain)
25
Table 6: Table showing the radiological abnormalities
21
1
Table 7: Table showing the radiological measurements
2 3
22
Table 1: Classification of os odontoideum
Group
Description
Number of Patients
Group 1
Partially or completely reducible atlantoaxial dislocation Fixed or irreducible atlantoaxial dislocation Basilar Invagination
116
Group 2 Group 3
51 23
Table 2: Table showing the presenting signs and symptoms
Presenting Complaints
Number of Patients
Neck pain Restricted Neck movements Weakness Paresthesias Ataxia Torticollis Urinary complaints Change in Voice
190 40 162 87 92 23 14 8
Table 3: Distribution as per clinical grading system. Grade
Description
Grade 1 Independent and normally functioning Grade 2 Walks on own but needs support/help to carry out routine household activities
Number of patients (Preoperative)
Number of patients (Postoperative)
30
174
71
16
Grade 3 Walks with minimal support and requires help to carry out household activities Grade 4 Walks with heavy support and unable to carry out household activities Grade 5 Unable to walk and dependant for all activities
34
-
42
-
13
-
Table 4: Grading of myelopathy by the Japanese Orthopedic Association Score
Score
Pre-operative (No. of patients)
Post-operative (No. of patients)
<7
8
-
8 – 12
61
-
>13
89
11
16 - 17
32
179
Table 5: Visual Analog scale (0 – no pain, 10- maximum pain)
VAS score
Pre-operative
Post-operative
Post-operative ( 6 months)
Neck pain
7.5 – 9.9 (8.8)
1.8 – 3.5 (2.1)
0 – 1 (0.3)
Table 6: Table showing the radiological abnormalities Radiological Abnormality
Number of Patients
Bifid arches of atlas Assimilation of atlas C2-3 Fusion Klippel- Fiel abnormality/Multiple Fusions Platybasia Osteophytes Chiari formation Syringomyelia External Syringomyelia
37 11 20 7 2 21 11 15 96
Table 7: Table showing the radiological measurements Angle (Degrees)
Group 1 Range (Average)
Group 2 Range (Average)
Group 3 Range (Average)
Craniocervical angle Angulation of articular facet of atlas
101.1 – 154.4 (129.8) 8.1 – 42.2 (16.6)
88.2 – 139.1 (116.3) 7.7 – 42.8 (20.23)
91.3 – 148 (115.3) 7.2 – 44.5 (18.6)
Abbreviations:
VAS – Visual Analog Scale JOA – Japanese Orthopedic Association Score
Conflict of Interest The author has no conflicts of interest to disclose.
S1878-8750(19)32735-4
DOI:
https://doi.org/10.1016/j.wneu.2019.10.107
Reference:
WNEU 13578
To appear in:
World Neurosurgery
Received Date: 7 September 2019 Revised Date:
17 October 2019
Accepted Date: 18 October 2019
Please cite this article as: Goel A, Patil A, Shah A, Dandpat S, Rai S, Ranjan S, Os-odontoideum: Analysis of 190 surgically treated cases, World Neurosurgery (2019), doi: https://doi.org/10.1016/ j.wneu.2019.10.107. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Inc.
Os-odontoideum: Analysis of 190 surgically treated cases
1. Atul Goel M.Ch. Neurosurgery Professor and Head of Department, Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel, Mumbai. and Consultant Neurosurgeon, Lilavati Hospital and Research Centre, Bandra (E), Mumbai. 2. Abhinandan Patil M.Ch. Neurosurgery Senior Resident, Department of Neurosurgery, , Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel, Mumbai. 3. Abhidha Shah M.Ch. Neurosurgery Assistant Professor, Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel, Mumbai. 4. Saswat Dandpat M.Ch. Neurosurgery Senior Resident, Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel, Mumbai. 5. Survendra Rai M.Ch. Neurosurgery Assistant Professor, Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel, Mumbai. 6. Shashi Ranjan M.Ch. Neurosurgery Senior Resident, Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel, Mumbai.
Correspondence: Prof. Atul Goel, Head of Department, Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel, Mumbai400012, India Telephone no: 22-24129884 Fax no: 22-24143435 E-mail: [email protected]
Conflict of Interest: None Disclosure of Funding; None
1
Os-odontoideum: Analysis of 190 surgically treated cases
2 3
Background: The management of os-odontoideum is analyzed on the basis of
4
approximately 20 years of experience.
5 6
Objective: This is a report of an experience with 190 cases having os-odontoideum.
7
The management outcome following atlantoaxial fixation is analyzed.
8 9
Material and methods: During the period January 2000 to September 2018, 190
10
patients having os-odontoideum were surgically treated. There were 113 males and 77
11
females and their ages ranged from 2 to 68 years (average 24 years).The patients were
12
divided into three groups depending on the nature of atlantoaxial dislocation (Group
13
1- mobile and partially or completely reducible atlantoaxial dislocation, Group 2-
14
fixed or irreducible atlantoaxial dislocation and Group 3- presence of basilar
15
invagination). Sixty- five patients were in pediatric age group (less than 18 years). All
16
patients underwent atlantoaxial joint manipulation and lateral mass plate and screw
17
fixation. The operation was aimed at segmental atlantoaxial arthrodesis. No transoral
18
or posterior foramen magnum bone decompression was done. Occipital bone was not
19
included in the fixation construct.
20 21
Results: On direct bone handling and observation, atlantoaxial joint pathological
22
hyperactivity related instability was identified in all patients. Atlantoaxial segmental
23
stabilization resulted in clinical symptomatic and neurological improvement in 100
24
percent patients.
25
1
1
Conclusions: Os-odontoideum signifies chronic or longstanding atlantoaxial
2
instability. Segmental atlantoaxial fixation is a reliable form of surgical treatment.
3
Any form of bone decompression is not necessary. Inclusion of occipital bone and
4
subaxial vertebrae in the fixation construct is not necessary.
5 6
Key-words: os-odontoideum, atlantoaxial instability, basilar invagination,
7
atlantoaxial fixation
8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
2
1
Os-odontoideum: Analysis of 190 surgically treated cases
2 3
Introduction:
4
Since its original description in 1886, os-odontoideum has been a well-defined and
5
frequently discussed abnormality of the odontoid process.1 Despite the fact that the
6
entity has been under discussion for approximately one and a half century, it may not
7
be incorrect to state that the pathogenesis remains unclear and the treatment protocol
8
has not yet been standardized. On the basis of largest personal series in the literature
9
till date, we discuss management of 190 cases having os-odontoideum. In the series,
10
we identify a hitherto unreported clinical entity of retro-C2-body cystic degeneration
11
associated with localized erosion of the bone of the C2 body in 28 cases. All patients
12
were successfully treated by atlantoaxial arthrodesis using lateral mass plate and
13
screw metal fixation technique.2,3
14 15
Material and Methods:
16
From January 2000 to September 2018, neurosurgery operation theatre database of
17
authors institutes included 2400 cases with craniovertebral junction instability that
18
were treated by atlantoaxial fixation. Of these, 190 patients had os-odontoideum.
19
These consecutive cases have been studied retrospectively. All the patients provided
20
written informed consent before surgery, and all clinical tests and surgical procedures
21
were conducted according to principles of Declaration of Helsinki. As the study is a
22
retrospective analysis of data and previously published surgical techniques were
23
deployed, ethics committee permission was not deemed necessary. Cases treated by
24
the senior author before the year 2000 have not been included in the study as the
25
clinical and radiological data is not entirely available and the treatment protocol
3
1
adopted was not uniformly similar to that presented in this report. As complete
2
odontoid process separation from the body of axis vertebra was only rarely
3
encountered, os-odontoideum was described as cases wherein a ‘significant’ or at-
4
least half of the odontoid process separated from the rest of the odontoid process-body
5
of axis complex. There was a clear and smooth demarcation of the separated part of
6
the odontoid process from either the rest of the odontoid process or from the body of
7
the axis. Patients treated conservatively or without surgery and evaluated only on
8
outpatient basis were not included. To describe and characterize the cases, the patients
9
were divided into 3 groups, depending on the nature of atlantoaxial instability and
10
presence of basilar invagination. Mobility of atlantoaxial dislocation was assessed on
11
dynamic lateral profile imaging (plain radiographs or sagittal CT scan) with the head
12
in flexed and extended positions. Despite the absence of odontoid tip as a landmark of
13
measurement, basilar invagination was assessed by the classically described
14
parameter of Chamberlain’s line.4,5 Group 1 included 116 cases where there was
15
partially or completely reducible atlantoaxial dislocation. (Figures 1 and 2) Group 2
16
included 51 cases where the atlantoaxial dislocation was fixed or irreducible in nature.
17
(Figures 3, 4) Group 3 included 23 cases where there was basilar invagination.
18
(Figure 5) (Table 1) Four patients had Down’s syndrome. Three patients including
19
two siblings, a 15 year old boy and an 18 year old girl had Morquio’s syndrome. No
20
other patient had any defined genetic or known syndromic abnormality. Two
21
additional patients belonged to the same family (daughter 25 years old and father 51
22
years old). There was no genetic abnormality in both of these patients. Ten patients
23
with os-odontoideum who had been operated earlier elsewhere were reoperated for
24
failed craniovertebral fixation surgical procedure done earlier. All of these patients
25
had Group 2 type of os-odontoideum.
4
1 2
Clinical profile: The clinical profile of the patients is summarized in Tables 2-5. Goel
3
clinical grading scale6, the Japanese Orthopedic Association7and Visual Analog Scale
4
(VAS)8 scoring systems were used to clinically evaluate the patients both before and
5
after the surgical treatment and at follow-up.
6 7
Radiological analysis: All patients underwent preoperative dynamic plain radiographs
8
and CT scan with the head in flexed and extended positions and MRI of the
9
craniovertebral junction. The bone anomalies observed in these patients are depicted
10
in Table 6. In all cases, dynamic imaging showed that during head movements the
11
odontoid process was firmly aligned to the clivus in the region of apical ligament and
12
to the anterior arch of atlas and did not move relative to movements of other
13
components of axis. The alteration in the craniocervical angulation varied in the
14
groups and is shown in Table 7. The angulation of the articular surface of facet of
15
atlas from the horizontal (in neutral head position) is detailed in Table 7.
16
Neural alterations included Chiari formation (11 patients) and syringomyelia (15
17
patients).Enlargement of the subaxial spinal subarachnoid space (external
18
syringomyelia), enlargement of spinal canal dimension and reduction of spinal cord
19
girth was identified in 96 patients.
20
A cyst-like formation, simulating ‘retroodontoid cyst’ was identified in the superior
21
and posterior aspect of the body of axis in 28 patients. (Figures 2, 6 and 7) The cyst
22
was labelled as ‘retro-C2-body’ cyst. The posterior aspect of the C2 vertebral body
23
adjoining the cyst had well defined bone erosion (as shown in the figures 2, 6 and 7)
24
in all cases. In cases where there was ‘retro-C2-body’ cyst, 18 patients had Group 1
25
os-odontoideum and 10 patients had Group 2 os-odontoideum.
5
1
Operative procedure: All patients underwent surgery with atlantoaxial lateral mass
2
plate/rod and screw fixation with the techniques described by the first author in 1994
3
and 2004.2,3 The basic surgical steps in all the three groups of patients involved
4
opening of the atlantoaxial articulation, manipulation and distraction of the facets,
5
denuding the articular capsule, packing of bone graft (harvested from iliac crest)
6
within the joint cavity and direct plate/rod and screw fixation of the lateral masses of
7
atlas and axis. Muscle attached to the posterior elements of atlas and axis was sharply
8
cut. Bone graft was additionally placed in the posterior midline after appropriately
9
preparing the host bone by drilling of its outer cortex. In the early part of the series, in
10
11 patients (4 patients were in Group 1, 5 patients were in Group 2 and 2 patients
11
were in Group 3) in addition to bone graft intra-articular metallic spacers were used to
12
distract the facets for the purpose of craniovertebral realignment and firm
13
stabilization.9,10 In subsequent cases, intrarticular metal implant was not used. No
14
foramen magnum bone decompression was done.
15 16
The constant observation was that there was clear evidence of atlantoaxial instability
17
on direct manipulation of the bones of the region in all three groups of patients. The
18
instability was identified on direct observation of the facets and articulation
19
irrespective of whether it was observed or not on preoperative dynamic radiological
20
imaging. In all cases the articular cartilage was well formed and the joints were
21
seemingly functionally active. In a number of cases, the articular cartilage extended
22
beyond the facets of atlas and axis over the pedicle of the axis bone. In cases with
23
bifid posterior arch of atlas, the facets of atlas were remarkably mobile and located
24
laterally in relationship with the facet of axis. The vertebral artery was ‘high-riding’
25
in the superior facet of axis in 55 cases.
6
1
The patients were advised to wear a firm external cervical collar for a period of 3
2
months after surgery and all neck activities and movements were restricted. After this
3
period all movements were permitted. The follow-up ranged from 6 to 218 months
4
(average 64 months).Postoperative CT scan was obtained within 24 hours of surgery,
5
3 months after surgery and at subsequent follow-up.
6 7
Results:
8
Tables 3 - 5 show the clinical outcome after at-least 6 months of surgery. All patients
9
improved in varying degrees in their clinical symptoms and neurological status. The
10
alterations in craniocervical angulation following surgery are shown in Table 7.
11
Delayed imaging (after one year of surgery) was available for review in 125 patients
12
showed evidence of bone fusion in all cases in the region of the facets and in the
13
posterior midline. There were no significant infection or implant related
14
complications. There were no implant failures or evidences of recurrent atlantoaxial
15
instability that forced reoperation.
16 17
Discussion:
18
Giacomini first described os-odontoideum in 1886.1By original definition; it refers to
19
an independent odontoid process bone that is separated from its base at the site of
20
attachment to the body of axis. Our analysis identifies that odontoid process
21
separation is more often not exactly at the probable site of junction of the odontoid
22
process with the body of axis. We identified os-odontoideum as a condition where a
23
‘significant’ or approximately atleast half of the presumed odontoid process separated
24
from the rest of the odontoid process and body of C2.The separated part of the
25
odontoid process has a smooth inferior border and has no anatomic continuity or
7
1
functional congruence with the remaining part of the odontoid process or the body of
2
axis. Os-odontoideum can sometimes mimic trauma related fracture at the base of the
3
odontoid process. Irregular edges of the fractured segments and a history of
4
significant trauma help distinguish fracture of odontoid process from os-odontoideum.
5
Os-terminale, ossification or osteophyte formation in the region of apical ligament are
6
other odontoid process related abnormalities.
7 8
Pathogenesis:
9
The pathogenesis of os-odontoideum is unclear and has been a debated issue. Genetic
10
abnormality and faulty embryogenesis has been suggested as a cause considering the
11
identification in some twin cases and in cases with Down’s and Morquio’s
12
syndrome.11-14 In our series there were two adults (father and daughter) without any
13
identified genetic abnormality and two siblings diagnosed to have Morquio’s disease.
14
The post-traumatic theory is the more prevailing theory.15-18 McRae believed that os-
15
odontoideum has embryological origin, but required the ongoing stresses of life to
16
trigger instability and produce symptoms after childhood.19 Os-odontoideum seems to
17
be a secondary phenomenon to primary longstanding atlantoaxial instability. The
18
presenting clinical symptoms are relatively mild, despite the evidences of significant
19
structural abnormality and neural deformation. This is probably related to a number of
20
natural protective measures that are in play.20,21 Bifid arches of atlas were seen in 37
21
cases.21 In our earlier analysis of 70 cases we identified that bifid arch of atlas had an
22
open-close door kind of movements. Head flexion that results in critical posterior
23
movement of the odontoid process is associated with opening of the door or widening
24
of the bifid of the posterior arch, whilst in extension of the head the door closes. We
25
likened bifid posterior arch to be a form of natural ‘decompressive laminectomy’.21As
8
1
discussed in our earlier publication, the articular surface of the facet of atlas was
2
rotated medially and the facet of atlas was dislocated lateral in relationship to the
3
facet of axis in a number of cases having bifid atlas.21 It was observed that these
4
morphological alterations were related to longstanding atlantoaxial instability and the
5
processes were designed to increase the transverse and decrease the vertical
6
dimensions of the spinal canal at the level of atlas. It was earlier identified that the
7
presence of syringomyelia, Chiari formation, external syringomyelia and external
8
syringobulbia, enlargement of cervical and dorsal spinal canal dimension, reduction in
9
spinal cord girth are natural secondary ‘protective’ events to primary atlantoaxial
10
instability.22-24 Considering that a number of these secondary neural and
11
musculoskeletal malformations are associated with os-odontoideum, it does appear
12
that os-odontoideum is by itself a secondary event to primary atlantoaxial instability.
13
It seemed that both os-odontoideum and bifid arch of atlas are essentially natural bone
14
transformations that are protective endeavours to save the cord from compression
15
between bones in the presence of potential or manifest atlantoaxial instability.
16 17
Clinical presentation:
18
Subtlety and long-standing nature and relatively mild to moderate intensity of
19
symptoms are the hallmarks, despite the radiological observation of marked instability
20
and related cord deformation or compression. Os-odontoideum may be identified
21
incidentally and the symptoms in these cases are seemingly unrelated to the odontoid
22
abnormality. In 19 patients the symptoms were relatively acute while in the rest 171
23
the symptoms were longstanding, average duration of symptoms ranged from 7 days
24
to 96 months. Neck pain (190 patients) and torticollis (23 patients) were prominent
25
symptoms. Ataxia, limb weakness, restricted neck movement, swallowing difficulties,
9
1
hoarseness of voice were the other presenting symptoms (Table 2). Symptoms related
2
to vertebral artery compromise have also been reported, but were not encountered in
3
our series. Mild to severe trauma precipitated neurological symptoms in 69 patients.
4 5
Indicators of instability:
6
Radiological evidence of movement of the odontoid ossicle and anterior arch of C1 on
7
dynamic films relative to the odontoid process-body of C2 forms a significant
8
evidence of instability.25,26 Presence of altered cord signals and evidence of cord
9
‘atrophy’ on MRI in relationship to the residual odontoid process-superior edge of the
10
body of C2 are indicators of instability.27 On flexion of the head, the body of C2
11
frequently travels anterior to its normal location and lays inferior to the anterior arch
12
of atlas. Thus the motion dynamics may vary in each individual patient with os-
13
odontoideum. As identified by us in an earlier report presence of bifid arch of atlas
14
and os-odontoideum is associated with lateral atlantoaxial facetal displacement or
15
dislocation.21 In at-least 23 cases there was additional evidence of rotatory atlantoaxial
16
dislocation. This multidirectional instability at the articulation between the atlas and
17
the axis is suggestive of defective or ineffective cruciate and capsular ligaments. Our
18
recent studies on the subject suggest that the atlantoaxial instability can also be
19
identified by their facetal alignment on lateral profile imaging with the head in neutral
20
position and direct observation and handling of bones of the region and assessment of
21
the status of the atlantoaxial joint during the surgical procedure.28 In general, in
22
younger patients, the atlantoaxial instability was more marked and reducible on
23
dynamic movements than in older patients where the instability tended to be of fixed
24
variety and basilar invagination was frequent.
10
1
It was observed that the atlantoaxial joints were functional and were pathologically
2
‘hyperactive’ in all cases, including those where the dynamic radiological images
3
were suggestive of ‘fixed’ atlantoaxial dislocation. More importantly, the facets of the
4
atlas and axis could be manually distracted and attempts could be made towards
5
restoration of craniovertebral junction alignment. Irrespective of the presence or
6
absence of radiologically demonstrable atlantoaxial instability or facetal mal-
7
alignment, os-odontoideum was by itself an indicator of atlantoaxial instability.
8 9
In 28 patients there was a cyst-like formation posterior to the superior aspect of the
10
body of axis. This cyst simulated retrodoontoid cyst formation, another feature that
11
was associated by us earlier with chronic atlantoaxial instability.29,30 Radiological
12
observation of presence of osteophytes in the vicinity of the os-odontoideum in at-
13
least 21 cases is also an indication of chronicity of the entire process. However, no
14
confirmation of histological nature was possible as these cysts were not directly dealt
15
with during surgery.
16 17
Indications of surgery:
18
On the basis of the understanding, that os-odontoideum is a manifestation of
19
atlantoaxial instability, in general, surgery is indicated for all patients. Presence of
20
pain in the nape of neck was by itself an indicator of instability and forms an
21
indication of surgery. Presence of any neurological symptom or deficit is a definitive
22
indication for surgical intervention. Considering the relative safety of the current
23
technical procedures, surgery can be indicated even in an incidentally detected os-
24
odontoideum. However, in such cases decision regarding the need for surgery will
11
1
have to be based on the clinical situation and the surgical experience of the treating
2
surgeon.
3 4
Surgical technique:
5
We have observed that Goel technique of C1 lateral mass and C2 fixation provides a
6
biomechanically firm and rigid internal fixation.2,3 The possibility of denuding of the
7
articular cartilage of the atlantoaxial joint, stuffing of bone graft within the joint and
8
of joint manipulation to reduce dislocation, makes this technique versatile. Individual
9
placement of screws in C1 and C2 lateral mass makes the procedure safer as regards
10
the vertebral artery. ‘High riding’ vertebral artery was identified in 55 cases (28.9 %).
11
This high incidence was significantly more when compared to the generally observed
12
incidence of high-riding vertebral artery. It is crucial to identify such a location of
13
vertebral artery and direct the screw in the pars-pedicle-facet of axis in a precise and
14
safe manner. More recently, we expose the vertebral artery after drilling the thin bone
15
shell that usually covers the posterior aspect of the arterial loop and mobilize it
16
laterally or inferiorly. This modified technique allowed safe insertion of the screw
17
into the facet of axis with the vertebral artery under direct surgical
18
vision.31Atlantoaxial stabilization using our technique resulted in biomechanically
19
strong fixation that ultimately led to arthrodesis of the unstable spinal segment. We
20
could achieve 100% bone fusion and all patients showed symptomatic and clinical
21
neurological recovery. The very fact that all patients in the series had symptomatic
22
recovery, no patient in the entire series over the study period of 20 years has needed
23
reoperation for any indication including implant failure or has suffered delayed
24
neurological worsening is a testimony to success of the surgical technique and
25
validity of atlantoaxial fixation as a surgical procedure. Our belief is that more than
12
1
neural deformation or evidences of compression, it is subtle instability related micro-
2
injuries to the cord that causes symptoms. Although complete reduction of the
3
atlantoaxial dislocation is preferable, strong stabilization of the atlantoaxial joint with
4
the aim to achieve arthrodesis is of prime significance and the goal of surgery and can
5
result in quick resolution of symptoms.
6
‘Fixed’ atlantoaxial dislocation with or without basilar invagination was identified in
7
74 cases. A number of factors have been implicated to result in ‘fixed’ dislocation.
8
Impaction of the transverse ligament between the odontoid process and the body of
9
the C2 has been implicated in the development of fixed atlantoaxial dislocation.32We
10
observed that in cases with fixed atlantoaxial instability (Group 2) and basilar
11
invagination (Group 3), the angulation of the facet of atlas was significantly acute in
12
relationship with the facet of axis when compared to cases where the atlantoaxial
13
instability was completely (Group 1) or partially reducible (Group 1). While
14
deploying our technique of atlantoaxial joint manipulation, distraction and reduction
15
of the dislocation, we observed that the joint in these cases is not only, not ‘fixed’, but
16
is mobile and pathologically hyperactive. Subtle and persistent abnormal movements
17
at this joint are the probable causes of clinical symptoms.12 In 11 early cases, titanium
18
metal spacer was used to distract the facets to reinforce stabilization and to achieve
19
reduction of the atlantoaxial dislocation and basilar invagination. However, in the
20
subsequent cases, only bone graft was impacted into the joint space and no metal
21
implant was used. Avoidance of metal implant allowed insertion of more bone graft
22
within the articular cavity and permitted an enhanced opportunity for arthrodesis of
23
the joint. As described by us earlier, the technique of craniovertebral junction
24
‘realignment’ was attempted in Group 2 and 3 cases by atlantoaxial joint
25
manipulation and distraction of facets of atlas and axis by deploying intra-articular
13
1
bone graft with or without metal implant.5,9 Despite the fact that realignment of the
2
craniovertebral junction was targeted, firm atlantoaxial athrodesis was the primary
3
aim of the surgical procedure. Decompression of the craniovertebral region by
4
anterior transoral route or by posterior foramen magnum decompression was not done
5
in the entire series and was considered against the aim of achievement of bone
6
arthodesis. Although important, the impact of craniovertebral stabilization and
7
realignment on subaxial cervical spine in general and spinal sagittal balance in
8
particular was not evaluated. Several authors have advocated the need for inclusion of
9
the occipital bone in the fixation construct.32 Menezes in his recent article has
10
identified the presence of occipito-atlantal instability in some patients having os-
11
odontoideum.33 Our analysis confirms that os-odontoideum is associated with
12
atlantoaxial instability and atlantoaxial stabilization forms the core of surgical
13
treatment. Occipitocervical fixation is unnecessary. It appears that inclusion of the
14
occipital bone in the fixation construct when it is not necessary or when it can be
15
avoided can result in disabling restriction of neck/head movements. Inclusion of
16
normal occipitoatlantal joint and subaxial spinal segments in the fixation construct
17
without directly disabling the joint by removal of articular cartilage can lead to
18
difficulty in providing movement-free construct that will allow bone fusion. Despite
19
the fact that the senior author was amongst the initial surgeons that discussed the use
20
of occipital screws for occipitocervical fixation3, we do not recommend
21
occipitocervical fixation for atlantoaxial instability. Moreover, occipital bone forms a
22
thin and poor host region for stable screw purchase.
14
1
Conclusions:
2
Presence of os-odontoideum is a definite indicator of atlantoaxial instability.
3
Atlantoaxial stabilization is the treatment.
4
References:
5 6 7 8
1. Giacomini C: Sull’ esistenza dell’ “osodontoideum” nell’ uomo. Gior Accad Med Torino.1886; 49:24-28. 2. Goel A, Desai K, Muzumdar D: Atlantoaxial fixation using plate and screw
9
method: A report of 160 treated patients. Neurosurgery. 2002;51:1351-1357.
10
3. Goel A, Laheri VK: Plate and screw fixation for atlanto-axial dislocation.
11 12 13 14 15 16
(Technical report). ActaNeurochir (Wien). 1994;129:47-53. 4. Goel A, Bhatjiwale M, Desai K: Basilar invagination: a study based on 190 surgically treated cases. J Neurosurg. 1998;88:962-968. 5. Goel A: Basilar invagination: Treatment by atlantoaxial joint distraction and direct lateral mass fixation. J Neurosurg Spine. 2004;1(3):281-6. 6. Goel A: Chiari malformation – Is atlantoaxial instability the cause? Outcome
17
analysis of 65 patients with Chiari malformation treated by atlantoaxial
18
fixation. J Neurosurg Spine 2015;22 (2): 116-127.
19
7. Fujiwara A, Kobayashi N, Saiki K, Kitagawa T, Tamai K, Saotome K.
20
Association of the Japanese Orthopaedic Association score with the Oswestry
21
Disability Index, Roland-Morris Disability Questionnaire, and short-form 36.
22
Spine (Phila Pa 1976)2003; 28:1601–7.
23
8. Huskisson EC: Measurement of pain. J Rheumatol1982; 9: 768-769.
24
9. Goel A: Atlantoaxial joint jamming as a treatment for atlantoaxial dislocation: a
25
preliminary report. Technical note J Neurosurg Spine 2007; 7(1):90-94. 15
1
10. Goel A, Kulkarni AG, Sharma P: Reduction of fixed atlantoaxial dislocation
2
in 24 cases: technical note. J Neurosurg Spine. 2005;2(4):505-9.
3
11. Dai L, Yuan W, Ni B, et al. Osodontoideum: etiology, diagnosis, and
4 5 6 7 8
management. Surg Neurol.2000;53:106–9. 12. Morgan MK, Onofrio BM, Bender CE. Familial osodontoideum: a case report. J Neurosurg.1989;70:636–9. 13. Kirlew KA, Hathout GM, Reiter SD, et al. Osodontoideum in identical twins: perspectives on etiology. Skeletal Radiol.1993;22:525–7.
9
14. Tang X, Tan M, Yi P, Yang F, Hao Q. Atlantoaxial dislocation and
10
osodontoideum in two identical twins: perspectives on etiology. Eur Spine J.
11
2018 ;27(Suppl 3):259-263.
12 13 14 15 16 17 18 19 20 21 22
15. Fielding JW, Hensinger RN, Hawkins RJ: Os odontoideum. J Bone Joint Surg (Am) 62. 1980:376-383. 16. Schuler TC, Kurz L, Thompson DE, et al. Natural history of os odontoideum: a case report. J Pediatr Orthop.1991;11:222. 17. Stillwell WT, Fielding JW. Acquired os odontoideum: a case report. Clin Orthop.1978;135:71. 18. Wollin DG. The os odontoideum: separate odontoid process. J Bone Joint Surg Am.1963;45:1459–71. 19. McRae DL: The significance of abnormalities of the cervical spine. AJR. 1960;84:3-25. 20. Goel A, Shah A. Reversal of longstanding musculoskeletal changes in basilar
23
invagination after surgical decompression and stabilization. J Neurosurg Spine
24
2009;10:220-7.
16
1
21. Goel A, Nadkarni T, Shah A, Ramdasi R, Patni N. Bifid Anterior and
2
Posterior Arches of Atlas: Surgical Implication and Analysis of 70 Cases.
3
Neurosurgery. 2015;77(2):296-305; discussion 305-6.
4
22. Goel A, Nadkarni T, Shah A, Sathe P, Patil M. Radiological evaluation of
5
Basilar invagination without obvious atlantoaxial instability (Group B-basilar
6
invagination): An analysis based on a study of 75 patients. World Neurosurg
7
2015; 95: 375-382.
8 9 10
23. Goel A, Sathe P, Shah A. Atlantoaxial fixation for Basilar invagination without obvious atlantoaxial instability (Group B-basilar invagination): Outcome analysis of 63 surgically treated cases. World Neurosurg 2017; 99:164-170.
11
24. Goel A, Jain S, Shah A. Radiological Evaluation of 510 Cases of Basilar
12
Invagination with Evidence of Atlantoaxial Instability (Group A Basilar
13
Invagination). World Neurosurg. 2018;110:533-543.
14
25. Goel A. Treatment of odontoid fractures. Neurol India. 2015;63(1):7-8.
15
26. Goel A, Jain S, Shah A, Patil A, Vutha R, Ranjan S, More S. Atlantoaxial
16
Fixation for Odontoid Fracture: Analysis of 124 Surgically Treated Cases.
17
World Neurosurg. 2018;110:558-567.
18 19 20 21 22 23 24 25
27. Goel A. Is focal spinal cord "atrophy" an evidence of chronic spinalinstability? J Craniovertebr Junction Spine. 2017;8(4):295-296. 28. Goel A: Goel’s classification of atlantoaxial “facetal” dislocation. J Craniovertebr Junction Spine2014;5 (1): 3-8. 29. Goel A. Retro-odontoid mass: An evidence of craniovertebral instability. J Craniovertebr Junction Spine. 2015;6(1):6-7. 30. Shah A, Jain S, Kaswa A, Goel A. Immediate Postoperative Disappearance of Retro-Odontoid "Pseudotumor". World Neurosurg. 2016;91:419-23. 17
1
31. Goel A, Rangnekar R, Shah A, Rai S, Vutha R. Mobilization of the vertebral
2
artery- surgical option for C2 screw fixation in cases with ‘high riding’
3
vertebral artery. Operative Neurosurgery (Accepted in press)
4
32. Wu X, Wood KB, Gao Y, Li S, Wang J, Ge T, Zhao B, Shao Z, Yang S, Yang
5
C.Surgical strategies for the treatment of osodontoideum with atlantoaxial
6
dislocation. J Neurosurg Spine. 2018;28(2):131-139.
7
33. Dlouhy BJ, Policeni BA, Menezes AH. Reduction of atlantoaxial dislocation
8
prevented by pathological position of the transverse ligament in
9
fixed,irreducibleosodontoideum: operative illustrations and radiographic
10
correlates in 41 patients. J Neurosurg Spine. 2017;27(1):20-28.
11 12
Figure Legends:
13
Figure 1: Images of a 14 year old boy
14
Figure 1a: T2-weighted MRI shows os-odontoideum. Cord compression can be seen.
15
Figure 1b: CT scan with the head in flexed position shows os-odontoideum.
16
Atlantoaxial instability can be seen.
17
Figure 1c: CT scan with the head in extension position shows reduction of
18
atlantoaxial dislocation.
19
Figure 1d: CT scan with the cut passing through the facets. It shows Type 1
20
atlantoaxial facetal instability. High-rising vertebral artery can be seen.
21
Figure 1e: Postoperative image showing fixation in aligned position.
22
Figure 1f: Postoperative CT scan showing the metal implant with plate and screws in
23
the facets of atlas and axis.
24
Figure 1g: Postoperative CT scan after 24 months of surgery shows bone fusion in the
25
region.
18
1
Figure 1h: Fusion of the facets can be seen.
2 3
Figure 2: Images of a 42 year old female
4
Figure 2a: T2-weighted MRI showing os-odontoideum and evidences of cord
5
compression. A retro-C2 body cyst can be seen.
6
Figure 2b: CT scan with the head in flexed position showing os-odontoideum and
7
atlantoaxial instability. Bone erosion can be seen in the region of retro-C2 body cyst.
8
Figure 2c: CT scan with the head in extension showing reduction of the atlantoaxial
9
instability.
10
Figure 2d: CT scan with the cut passing through the facets. Osteophytes can be seen
11
in the vicinity of facets.
12
Figure 2e: Postoperative CT scan showing the fixation in aligned position.
13
Figure 2f: CT scanwith the cut passing through the facets showing the implant.
14 15
Figure 3: Images of a 14 year old boy
16
Figure 3a: T2-weighted MRI showing os-odontoideum and atlantoaxial instability.
17
Syringomyelia can be seen.
18
Figure 3b: CT scan with the head in flexed position showing atlantoaxial instability.
19
Figure 3c: CT scan with the head in extended position. Reduction of the dislocation is
20
not seen (Group 2 os-odontoideum).
21
Figure 3d: Postoperative CT scan showing reduction of the dislocation.
22
Figure 3e: Postoperative CT scan showing the implant.
23 24
Figure 4: Images of a 14 year old girl
19
1
Figure 4a: T2-weighted MRI showing os-odontoideum and related atlantoaxial
2
instability and cord compression.
3
Figure 4b: CT scan with the head in flexed position showing atlantoaxial instability.
4
Figure 4c: CT scan with the head in extended position showing no reduction of the
5
dislocation.
6
Figure 4d: 3-D CT scan showing presence of bifid posterior arch of atlas.
7
Figure 4e: Postoperative CT scan showing fixation in aligned position.
8
Figure 4f: CT scan showing the implant. Note the high-vertebral artery.
9 10
Figure 5: Images of a 17 year old boy
11
Figure 5a: T2-weighted MRI showing os-odontoideum with basilar invagination
12
(Group 3 os-odontoideum).
13
Figure 5b: CT scan with the head in flexion showing os-odontoideum with basilar
14
invagination.
15
Figure 5c: Postoperative CT scan showing reduction of basilar invagination and
16
fixation in aligned position.
17
Figure 5d: CT scan with the cut through the facets showing the implant.
18 19
Figure 6: Images of a 42 year old male patient.
20
Figure 6a: T2-weighted MRI showing os-odontoideum and cord compression.A retro-
21
C2 body cyst can be seen
22
Figure 6b: Axial image showing the retro C2 body cyst.
23
Figure 6c: CT scan showing os-odontoideum and atlantoaxial instability. Bony
24
erosions on the posterior aspect of body of C2 can be seen.
25
Figure 6d: CT scan showing the alignment of facets.
20
1
Figure 6e: Post-operative MRI showing resolution of the retro C2 body cyst.
2
Figure 6f: Axial image showing resolution of the cyst.
3
Figure 6g: Postoperative CT scan showing fixation in aligned position.
4
Figure 6h: Postoperative CT scan showing the implant.
5 6
Figure 7: Images of a 38 year old female patient
7
Figure 7a: T2-weighted MRI showing os-odontoideum, atlantoaxial instability and
8
cord compression. A small cyst located in the posterior aspect of the C2 vertebral
9
body.
10
Figure 7b: CT scan with the head in flexion showing os-odontoideum and atlantoaxial
11
instability. A relatively small bone erosion in the posterior aspect of C2 body is seen.
12
Figure 7c: Postoperative scan showing fixation in alignment.
13
Figure 7d: Postoperative scan with the cut passing through the facets showing the
14
implant.
15
Figure 7e: Postoperative scan after 16 months of surgery showing fusion of the
16
posterior elements.
17
Figure 7f: Scan showing fusion of the facets.
18 19
Table Legends:
20
Table 1: Classification of os odontoideum
21
Table 2: Table showing the presenting signs and symptoms
22
Table 3: Distribution as per clinical grading system.
23
Table 4: Grading of myelopathy by the Japanese Orthopedic Association Score
24
Table 5: Visual Analog scale (0 – no pain, 10- maximum pain)
25
Table 6: Table showing the radiological abnormalities
21
1
Table 7: Table showing the radiological measurements
2 3
22
Table 1: Classification of os odontoideum
Group
Description
Number of Patients
Group 1
Partially or completely reducible atlantoaxial dislocation Fixed or irreducible atlantoaxial dislocation Basilar Invagination
116
Group 2 Group 3
51 23
Table 2: Table showing the presenting signs and symptoms
Presenting Complaints
Number of Patients
Neck pain Restricted Neck movements Weakness Paresthesias Ataxia Torticollis Urinary complaints Change in Voice
190 40 162 87 92 23 14 8
Table 3: Distribution as per clinical grading system. Grade
Description
Grade 1 Independent and normally functioning Grade 2 Walks on own but needs support/help to carry out routine household activities
Number of patients (Preoperative)
Number of patients (Postoperative)
30
174
71
16
Grade 3 Walks with minimal support and requires help to carry out household activities Grade 4 Walks with heavy support and unable to carry out household activities Grade 5 Unable to walk and dependant for all activities
34
-
42
-
13
-
Table 4: Grading of myelopathy by the Japanese Orthopedic Association Score
Score
Pre-operative (No. of patients)
Post-operative (No. of patients)
<7
8
-
8 – 12
61
-
>13
89
11
16 - 17
32
179
Table 5: Visual Analog scale (0 – no pain, 10- maximum pain)
VAS score
Pre-operative
Post-operative
Post-operative ( 6 months)
Neck pain
7.5 – 9.9 (8.8)
1.8 – 3.5 (2.1)
0 – 1 (0.3)
Table 6: Table showing the radiological abnormalities Radiological Abnormality
Number of Patients
Bifid arches of atlas Assimilation of atlas C2-3 Fusion Klippel- Fiel abnormality/Multiple Fusions Platybasia Osteophytes Chiari formation Syringomyelia External Syringomyelia
37 11 20 7 2 21 11 15 96
Table 7: Table showing the radiological measurements Angle (Degrees)
Group 1 Range (Average)
Group 2 Range (Average)
Group 3 Range (Average)
Craniocervical angle Angulation of articular facet of atlas
101.1 – 154.4 (129.8) 8.1 – 42.2 (16.6)
88.2 – 139.1 (116.3) 7.7 – 42.8 (20.23)
91.3 – 148 (115.3) 7.2 – 44.5 (18.6)
Abbreviations:
VAS – Visual Analog Scale JOA – Japanese Orthopedic Association Score
Conflict of Interest The author has no conflicts of interest to disclose.