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| EDITORIAL |
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| Year : 2022 | Volume
: 9
| Issue : 1 | Page : 10-14 |
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Right-Sided anterior extrapharyngeal approach to bilateral atlantoaxial joints - An experience
Vinu V Gopal
Professor, Department of Neurosurgery, Government Medical College, Kottayam, Kerala, India
| Date of Submission | 04-Jan-2022 |
| Date of Acceptance | 05-Jan-2022 |
| Date of Web Publication | 9-Mar-2022 |
Correspondence Address:
Vinu V Gopal
Department of Neurosurgery, Government Medical College, Kottayam, Kerala
India
 Source of Support: None, Conflict of Interest: None
DOI: 10.4103/joss.joss_2_22
How to cite this article:
Gopal VV. Right-Sided anterior extrapharyngeal approach to bilateral atlantoaxial joints - An experience. J Spinal Surg 2022;9:10-4 |
Atlantoaxial facet joints act as the center of mobility and subsequently form the center for instability of the craniovertebral junction.[1],[2] It is one of the body's most mobile joints. The atlantoaxial joints of two sides and the occipitoaxial joints form the rostral two limbs of the Y-shaped configuration of the human spinal support pillar.[1],[2] Because of the excessive mobility of the atlantoaxial (C1-C2) motion segment, fusion rates are lower than those done at the sub-axial spine. The concept that the seat of instability rests in the facetal malalignment and that arthrodesis with stable bony fusion results in good patient outcomes has revolutionized the treatment of instability at atlantoaxial joints.[1],[2]
The aim of the treatment of atlantoaxial instability is to achieve a solid bony fusion between atlantoaxial joints, thereby eliminating any motion between them. This will relieve the neck pain and avoid the risk of further neurological deterioration. Over the past years, technical advances have been made on fixation techniques of the unstable atlantoaxial joint.
In this editorial, I would like to highlight the advantages of the anterior approach to fixation of the atlantoaxial region compared to the classical posterior approach. With my limited experience, I will touch upon the technical nuances involved in this approach.
| Problems Associated with Posterior Paraspinal Approach to Atlantoaxial Joints | |  |
The posterior paraspinal approach for atlantoaxial cage distraction and screw fixation (Goel technique) is the gold standard for the management of atlantoaxial subluxation despite the paucity of randomized controlled trials.[1] There are several problems associated with the posterior paraspinal approach.
The main disadvantages of posterior surgery involve disruption of the posterior ligamentous complex, which is crucial for stability. Iatrogenic C2 root denervation leads to paraspinal muscle atrophy, which worsens the instability. Another major risk is vertebral artery injury.[3]
The right submandibular approach to the anterior retropharyngeal space provides adequate access to both atlantoaxial joints. This approach is purely intermuscular and hence does not disrupt the craniovertebral ligaments. An added advantage is that odontoid decompression can also be done if required. There is almost no risk of injury to the vertebral artery, paravertebral venous plexus, or the C2 ganglion.
| Right-Sided Anterior Extrapharyngeal Approach | | |
The technique of the anterior retropharyngeal approach was popularized by Patkar.[3] The joint can reduce spontaneously when a patient is placed in a supine position with neck extension. Moreover, it helps to make fixation more feasible.[3] Results also showed a 100% rigid fixation with no mortality and 0% risk of vertebral artery injury.[3] In his studies, complications such as the risk of carotid artery injury and nerve injuries (marginal mandibular nerve, hypoglossal nerve, vagal nerve, and recurrent laryngeal nerve) were minimal. Hence, they can be considered a good option compared to the gold standard technique of the posterior approach to atlantoaxial fixation in terms of patient outcome. Although data regarding the technical difficulty of distraction and compression with plates, screw loosening, implant failure, risk of over distraction, and long-term follow-up regarding fusion need to be addressed, the fixation technique is also cost-effective compared to the gold standard. Multi-institutional prospective studies are required for further validation of results. Further, follow-up clinical data and level 1 evidence are required for precise information.
In this editorial, I would like to share my experience with the anterior retropharyngeal approach in craniovertebral junction diseases, mainly due to trauma and infection. In the past year, I did four cases of anterior retropharyngeal approach for rigid fixation and fusion of bilateral atlantoaxial joints.
| Surgical Technique - Anterior Extrapharyngeal Approach to Atlanto-Axial Joints | | |
All the cases were done under general anesthesia with endonasal intubation. The patient position adopted was supine with the extension of the head [Figure 1]. A lateral X-ray was taken to confirm that mandible was at or above the C2 body. Two C arms were placed and oriented perpendicular to each other in a biplanar mode, as shown in [Figure 2]. The position was confirmed with the preoperative operative axial and sagittal three-dimensional computerized tomography (CT) angiogram in an extended position [Figure 3]. | Figure 3: Preoperative planning with three-dimensional reconstructed computerized tomography along with vertebral angiogram with the neck in extension
Click here to view |
A curved incision was made 2 cm below the mandibular margin from the midline to the angle of the mandible safeguarding the marginal mandibular nerve [Figure 4]a. Flaps were raised in the subplatysmal plane. After double ligation of the facial artery, the mylohyoid was reflected upward to expose the submandibular gland, the digastric muscle, and the stylohyoid muscle [Figure 4]a. Hypoglossal nerve could be identified and mobilized by sharp dissection after reflecting the digastric muscle upwards [Figure 4]b and [Figure 4]c. | Figure 4: Steps of exposure (a) subplatysmal flap yellow arrow indicates submandibular gland and digastric muscle (b) identification of hypoglossal nerve, yellow arrow indicates hypoglossal nerve (c) dissecting hypoglossal nerve, green and blue arrow indicate the course of hypoglossal nerve
Click here to view |
Retropharyngeal space on the anterior aspect of the C2 body was approached just medial to the internal carotid artery. The anterior surface of C1 was exposed with cautery and periosteal elevators after placing four long blades (6–8 cm) of Medtronic® Trimline retractor perpendicular to each other [Figure 5]. The C2 body was cleared of anterior longitudinal ligament, and the longus Colli was dissected to expose the atlantoaxial joints on both sides. The joint capsule was opened to expose the synovium, and the joint cartilage was curetted to the posterior margin of the joint. The supine position with a mild extension of the head almost always resulted in the reduction of mobile atlantoaxial dislocations.
I would like to share my experiences with the various constructs done through this approach
- Bilateral transarticular screws for atlantoaxial instability along with odontoid screw construct for fracture odontoid (triple screws) [Figure 6]a and [Figure 6]b
 | Figure 6: Bilateral transarticular screws (a) Introperative picture (b) lateral X-ray view
Click here to view |
It was always easier to pass the contralateral screw from a right-sided approach. A 6–10 mm screw in lateral mass and 5–8 mm in sub-facet of axis vertebra provided rigid fixation. If needed, this can be combined with an odontoid screw inserted through a sub-axial mini-incision. Postoperative CT is shown in [Figure 7].
- Anterior plate and screw system [Figure 8]
The anterior surface of the lateral mass of C1 on both sides was cleared of soft tissue for the placement of polyslotted plates [Figure 9]. After placing the plate, the entry point for the upper screw on the plate was the midpoint of the C1-C2 joint, and screws of length 15–20 mm were directed 20° upward and outwards (direction and length based on preoperative CT scan). The lower screw on the polyslotted plate was directed 20° medially and length calculated as per CT measurements. The head was slightly extended before fixing the lower screw to reduce the atlantoaxial dislocation, which was confirmed using the C arm. The procedure was repeated on the opposite side. The X-ray picture showing the plate and screw along with the cage in situ is shown in [Figure 10].
- Anterior atlantoaxial joint jacking and cage distraction for correction of Basilar invagination [Figure 9] and [Figure 10]
Customized titanium wedge-shaped hollow cages (5–7 mm anteriorly, 3–5 mm posteriorly, and 12-mm width [Jayaon Surgical Co., Chennai, India])[3] are also available which can be filled with bone substitute (G. Surgiwear India Ltd., Mumbai, India) [Figure 9] and [Figure 10].
Irreducible dislocations can be reduced by facet joint mobilization after curettage. Customized wedge-shaped lordotic cages made of titanium can be used to distract the joint, thereby reducing basilar invagination if required. As the approach is retropharyngeal, there is no violation of mucosa, and if needed, we can do odontoid decompression. The implants used were Dynamic compression plates (used routinely in the orthopedic procedure) which are cost-effective. Self-tapping screws with polyslotted plates along with lordotic cages help in joint distraction. Once tightened, the screw will engage in the next lower slot providing sufficient compression and reduction.
- Extrapharyngeal odontoidectomy and fixation in cases of anterior cervico-medullary compression
If anterior odontoid decompression is needed, it can be done simultaneously through the same approach. I would also like to share my experience of managing a case of craniovertebral junction rheumatoid arthritis for which an anterior extrapharyngeal odontoid decompression was done, followed by bilateral cage distraction and fixation using plate and screws. The same was done under motor-evoked potential monitoring [Figure 11]. Postoperative reconstructed CT is shown in [Figure 12]. The patient was discharged on the 5th postoperative day with no major complication except for mild hypoglossal nerve praxia.
 | Figure 11: Exposure of bilateral C1-C2 joint in rheumatoid spine (a) retroflexed odontoid (b) after odontoidectomy
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 | Figure 12: Postoperative computerized tomography (three-dimensional reconstruction) showing odontoidectomy and anterior plates and screws with spacer
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All patients who underwent anterior approach in my case series were ambulated with a Philadelphia cervical collar the next day. Postoperative X-rays and CT-scan were done to confirm reduction and fixation.
| Advantages of Anterior Extrapharyngeal Approach | | |
- There is no risk of injury to the vertebral artery, paravertebral venous plexus, or C2 ganglion
- The supine position with the mild extension of the head almost always reduces mobile atlantoaxial dislocations, and most irreducible dislocations can be reduced by odontoid and facet manipulation[4]
- Customized wedge-shaped lordotic titanium cages can distract the axis with the odontoid and reduce basilar invagination. The lateral mass of the atlas and the body of the axis provide adequate bone stock for rigid screw plate fixation without risk of vascular injury
- This approach is retropharyngeal and does not violate mucosa, and if needed, we can combine odontoid decompression
- Moreover, the procedure is cost-effective as the implants used were dynamic compression plates (poly slotted). Self-tapping screws, once tightened, will engage in the next lower slot of the poly slotted plate providing sufficient compression and reduction.
Limitations
- This approach is also not without limitations as it has a steeper learning curve, risk of hypoglossal injury, and marginal mandibular injury, which needs further validation in large series
- Data regarding the technical difficulty of distraction and compression with plates, problems with screw loosening, implant failure, risk of over distraction, and long-term follow-up regarding fusion need to be addressed[4]
- Further research on biomechanical feasibility using anatomical ex vivo and in-vivo constructs must be done to validate further the anterior approach's appropriateness and safety for C1-C2 fixation and fusion.
Although my experience is limited to four cases of anterior atlantoaxial fixation, I feel that biomechanical feasibility with polyaxial screws and rods will be a future area of research. By reducing the size of the screw head, the similar principle of distraction and compression can be applied from the anterior approach also with less risk of postoperative dysphagia. The anterior approach still needs further randomized controlled trials for level 1 evidence. Further research and biomechanical feasibility using anatomical ex vivo and in-vivo constructs must be done to validate further the appropriateness and safety of the anterior approach for C1 to C2 fixation and fusion.
Acknowledgments
The author especially thank his colleagues in the Department of Neurosurgery, Medical College, Kottayam, for the support.
| References | | |
| 1. | Goel A. Craniovertebral anomalies: Role for craniovertebral realignment. Neurol India 2004;52:427-9.  [ PUBMED] [Full text] |
| 2. | Goel A, Laheri V. Plate and screw fixation for atlanto-axial subluxation. Acta Neurochir (Wien) 1994;129:47-53. |
| 3. | Patkar S. Anterior fixation of atlantoaxial joints: Technique and pitfalls. J Spinal Surg 2014;1:60-8. [Full text] |
| 4. | Gopal VV. Atlantoaxial fixation-anterior or posterior approach, critical review. J Spinal Surg 2016;3:51-4. [Full text] |
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12]
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