Although posterior approaches are being used frequently in most atlantoaxial dislocations (AAD), anterior decompression is also required in some patients in whom the C1-2 dislocation is not properly reduced by the posterior approach. Transnasal and transoral approaches need an additional posterior approach to perform atlantoaxial fusion. They also have an added risk of infection. The endoscopic transcervical approach can be used for single-stage cervical decompression and stabilization that includes an odontoidectomy and anterior fusion. It can be used both in reducible and irreducible AAD. Patients with a high basilar invasion, traumatic or other lesions involving the C1 or C2 facet joint, reducible AAD with Chiari malformation, and patients with a large mandible or a mandible angle lying below the C3 level even after the maximum neck extension, should not be subjected to this procedure. Preoperative X-ray, computed tomography (CT) scan with angiogram, and magnetic resonance imaging of the craniovertebral region should be done to assess the dislocation. The early results of an endoscopic transcervical approach were found to be safe and effective for decompression and fusion in our experience. There was no permanent complication. The procedure avoids a two-stage surgery; thus, odontoidectomy, if needed, can be performed in addition to the C1-2 fusion in a single stage.
Keywords: Atlantoaxial Joint, endoscopic surgical procedure, joint dislocation, minimally invasive surgical procedure, surgical decompression Key Message:
The novel endoscopic single-stage anterior decompression and anterior fusion by the transcervical approach for the management of patients with AAD is described. Its advantages include minimal soft tissue disruption, preservation of the posterior tension band, an easier supine positioning of the patients during surgery, avoidance of the contaminated transoral or transnasal corridor, avoidance of risk of injury to the vertebral artery, and, if required (especially if reduction is not satisfactory after joint manipulation), performance of a simultaneous odontoidectomy in single stage anterior approach.
How to cite this article: Yadav YR, Ratre S, Parhihar V, Dubey A, Dubey NM. Endoscopic technique for single-stage anterior decompression and anterior fusion by transcervical approach in atlantoaxial dislocation. Neurol India 2017;65:341-7
How to cite this URL: Yadav YR, Ratre S, Parhihar V, Dubey A, Dubey NM. Endoscopic technique for single-stage anterior decompression and anterior fusion by transcervical approach in atlantoaxial dislocation. Neurol India [serial online] 2017 [cited 2022 Nov 27];65:341-7. Available from: https://www.neurologyindia.com/text.asp?2017/65/2/341/201834
The endoscopic single-stage anterior decompression and anterior fusion by the transcervical approach, performed in patients with AAD that was causing a high cervical myelopathy, is a novel technique that ensures an adequate surgical corridor, adequate visualization of C1-2 vertebral bodies through the anterior approach and facilitates the performance of a single procedure for both decompression and stabilization. In the recent times, solely the posterior approach is often being utilized to bring about a reduction in AAD. In the small percentage of patients who do not benefit from the posterior approach, an additional transoral approach may also be required; the latter, however, is through the potentially infected oral or nasal cavity and precludes a simultaneous anterior C1-2 stabilization utilizing a metal prosthesis due to the fear of infection. An open anterior transcervical extrapharyngeal approach has been found to be effective,,,,, with the additional advantage of avoiding the contaminated corridor, that also facilitates a good screw purchase, and minimal dissection of tissue; however, it has not been widely used due to the oblique visualization of the C1-2 vertebral segments and the narrow operative windows through which the surgeon has to operate.
Microscopic anterior release of the C1-2 joints leading to the reduction of irreducible AAD along with anterior transarticular screw fixation;, and, transoral release, reduction, internal fixation, and bone grafting , have been described in order to avoid performing an additional posterior approach for C1-2 joint stabilization. However, the former procedure requires a significant amount of coronal angulation for access to the C1-2 articular processes; and, there is a risk of infection in the latter approach through the transoral corridor. To the best of our knowledge, the endoscopic technique of a single-stage anterior decompression and anterior fusion by the transcervical approach for management of AAD, that is being described in this article, has not been reported. The preliminary experience, technical details, indications, limitations, results and advantages of the procedure are being presented in this article. The institutional ethical committee's permission was obtained prior to performing this new procedure.
Preoperative work up
The age, sex, duration of symptoms, and preoperative clinical status of the patients using Ranawat grading were recorded. Preoperative plain radiographs, a computed tomography (CT) scan including a CT angiogram for evaluating the course of the vertebral artery, and magnetic resonance imaging of the craniovertebral region were done to assess the C1–C2 joint displacement, the thecal sac compression, and the associated bony and soft tissue anomalies of this region. Relevant blood investigations were also done as a part of preanesthetic work up in all these patients. A preoperative cervical traction was instituted in an attempt to reduce the displaced C1-2 joints.
Indications and limitations of the procedure
Both patients with reducible and irreducible AAD may be subjected to this procedure. The contraindications to performing this procedure include a very high basilar invasion, traumatic or other pathological lesions involving the C1 or C2 facet joints, reducible or irreducible AAD with Chiari malformation More Details, and patients with a large mandible or in whom the angle of the mandible lies below the C3 level, even after maximum possible neck extension.
General anesthesia was used. The patient was placed on a radiolucent table in the supine position. The neck was kept in a position of slight extension by a folded roll placed between the scapulae. A skull traction was applied. A 3–5 cm skin incision that extended horizontally about 2 cm below the margin of mandible was given in a natural skin crease. The platysma muscle was incised along the same line. The cervical fascia was divided horizontally and elevated superiorly, protecting the marginal mandibular nerve. The sternocleidomastoid muscle was mobilized and retracted posteriorly. The hypoglossal nerve was identified, mobilized superiorly, and protected. Lingual and superior thyroid vessels were divided after doubly ligating them with 3-0 silk if they were traversing the trajectory of the approach. The prevertebral fascia over the C1–C2 vertebra was divided and dissected off the vertebral bodies. Gauze pieces tagged with silk sutures were placed along the cranial and caudal ends as well as the right, and left corners of the surgical exposure in order to prevent the prolapsing soft tissue from obscuring the endoscopic field of view [Figure 1].
Figure 1: Gauze pieces placed at the cranial and caudal ends and the right, and left corners of the surgical exposure to prevent soft tissue prolapsing into the endoscopic field
The Destandau set was introduced and further procedure was performed under endoscopic control. The medial part of the longus coli muscle was divided and the articular capsule of the atlantoaxial joint incised with the help of a monopolar cautery and dissector [Figure 2]. Care was taken to prevent injury to an aberrantly located vertebral artery near the C1 facet, a finding that may rarely be present. The anterior arch of C1, vertebral body of C2, and both lateral C1–C2 joints were identified. After release of the anterior constricting tissue, realignment of C1–C2 was attempted by inserting a curette into the atlantoaxial joint and using a lever arm under fluoroscopic guidance. Decortication of the facet joint margin was performed using a curette and drill [Figure 3] after the dislocation was corrected. Autologous bone graft was packed into the joint space [Figure 4]. If the dislocation could not be reduced, steps were undertaken to proceed with an anterior cervical odontoidectomy using the same surgical corridor. The intial step of this procedure involved removal of the soft tissue between the anterior arch of Atlas More Details and the odontoid process. Then, drilling of the odontoid process was done using a high-speed drill [Figure 5]. The anterior arch of the atlas was either spared or only a small portion was drilled, if needed, to reach the tip of the odontoid process [Figure 6]. The entire odontoid process was removed (operative video 1). Only a small part of the anterior portion of the C2 body was removed, whereas a major portion of the posterior part of the C2 body, which was causing compression on the cord, was excised [Figure 7]. Illustrations of the surgical technique are shown in [Figure 8]. The presence of good dural pulsations suggested an adequately wide decompression in the region of C1–C2 vertebrae [Figure 9]. The next part of the procedure was the anterior cervical plating. This involved drilling of the C1 lateral mass approximately 5 mm superior to the mid-point of C1–C2 facet joint [Figure 10]. The titanium plate that was being utilized for C1-2 fusion was installed through the outer tube of the Destandau set after removal of its inner tube. The plate was then rotated to align the plate hole with the hole made in the C1 lateral mass [Figure 11]. A screw was inserted through the hole in the upper end of the plate into the C1 lateral mass that was directed posteriorly with approximately 10° cranial angulation [Figure 12]. The screw that held the plate against C2 vertebral body was inserted into any part of the C2 vertebra from approximately 5 mm below the medial third of the C1–C2 facet joint to just lateral to the midline of C2 body [Figure 13]. The screw was slightly angulated in the proper direction. Lateral angulation was preferred when screw was placed near the midline, whereas a medial angulation was used when it was placed laterally below the medial third of C1–C2 facet joint. C1 lateral mass and C2 body fixation was achieved using the cervical plate and screw and autologous bone grafts [Figure 14]. Drilling of the bone and tightening of the screw was possible through the working channel of the endoscope with the utilization of proper endoscopic equipment. A telescope may also be held by a scope holder to visualize the operative field, and the screws fixing the plate to the bone may be tightened through the outer tube of the Destandau set after removal of the inner tube. The usual length of screws used in adults was 18 mm whereas it was 14 mm in children. Closure was completed with or without suction drain.
Figure 2: Medial part of longus coli, articular capsule of the atlantoaxial joint, and anterior constricting tissues are removed with the help of monopolar cautery
Figure 6: Postoperative CT scan showing (a) right and (b) left-sided C1 lateral mass and C2 screws with plate along with interposed bone graft; (c) removal of odontoid process; and, (d) reconstructed C1–C2 plates and screws on both sides with spared anterior arch of C1
Figure 11: (a) Plate is dropped through the outer tube of Destandau tube after removal of the inner tube; (b) Cranial hole of plate is moved towards hole in the lateral mass; (c) plate hole corresponded with the hole already made on the C1 lateral mass
In 15 patients who underwent this procedure, a minimal follow-up of 3 months was available. Their ages ranged from 7 to 68 years. There were 9 male and 6 female patients. The duration of their syymptoms ranged from 4 to 14 months. All patients had quadriparesis. There were 4 patients with a reducible AAD whereas 11 had an irreducible AAD. There were 14 patients with a congenital AAD and one with a post-tuberculous AAD (that had developed after the course of antituberculous therapy had resolved the infection), respectively. There were 12 and 3 patients in preoperative Ranawat grade 3A and 3B, respectively [Table 1]. Intraoperative reduction of the dislocation could be achieved in 11 patients, and 4 required odontoid excision. A good exposure was obtained in all cases. The anterior arch of atlas was partially drilled in 2 patients, whereas in 13 patients, it was spared. All patients improved after surgery. At follow up ranging between 3-5 months, 11 and 4 patients had achieved Ranawat grade 1 and 2, respectively. The duration of the procedure ranged from 115–175 minutes (average = 145 minutes). The blood loss ranged from 25 to 100 ml (average = 70 ml). There was no permanent complication. Postoperative imaging showed a good decompression and C1–C2 alignment [Figure 6] and [Figure 15].
Table 1: Demography, preoperative status, type of surgery performed, and postoperative condition after endoscopic transcervical approach
No complication was encountered in any of our patients; however, postoperative hoarseness of voice, transient palsy of the marginal mandibular branch of the facial nerve and of the hypoglossal nerve, a salivary fistula, carotid artery occlusion, and carotid artery injury, have been reported while operating in this area.
Versatility of endoscopic approaches
Endoscopic techniques are frequently used now in various cranial ,, and spinal , conditions and in a wide variety of indications. The procedures include endoscopic third ventriculostomy,, brain abscess, arachnoid cyst, and hematomas. A recent report has also focused upon its utilization in the clipping of anterior circulation aneurysms. Its advantages include an adequate visualization of an operative field of view in close proximity to the site of surgery; utilization of a narrow surgical corridor with minimal soft tissue displacement; and, an adequate illumination of every nook and corner of the surgical field.
Alternate surgical techniques
Although the posterior approach has been used frequently and has been found to be effective in most of the cases, a proper C1-2 joint reduction could not be achieved in a significant percentage of patients, who need anterior decompression. Irreducibility after the posterior approach can be seen when there is severe anterior–posterior dislocation, vertical joint alignment, soft tissue interposition between the C1 anterior arch and the odontoid process, presence of contracted tissue anterior to C1–C2, malunion of C1–C2 due to fibrosis or callus, etc. Other operative techniques have been found to be effective in the treatment of AAD such as fixation of lateral atlantoaxial articulations using open anterior approach,,, endoscopically-assisted anterior retropharyngeal release with posterior fixation,, and endoscopic anterior transarticular screw fixation.,
Comparison with other C1–C2 fusion techniques
Transarticular screw fixation of the atlantoaxial joint using either the anterior ,,,,, or the posterior approach  has been found to be safe and effective. Anterior transarticular screw approach has been found to be as stable as the posterior transarticular fixation in all clinically significant planes of motion.,,, Although both procedures, the posterior C1 lateral mass-C2 pedicle screw technique and the posterior transarticular screw fixation, were found to be safe and effective treatment options for C1–C2 instability, no such comparison has been made, to the best of our knowledge, between the techniques of anterior transarticular screw and the anterior C1 lateral mass-C2 body screw placement.
Advantages and limitations of this technique
The endoscopic transcervical approach has been found to be safe and effective in our series. There were no permanent complications. The approach was effective in the proper visualization and effective handling of tissues during surgery. This technique may be effectively used for a simultaneous C1-2 decompression and stabilization, thereby avoiding a two-stage surgery. Anterior transcervical approach has the advantage of minimal tissue disruption, preservation of posterior tension band, and an easy supine positioning of the patient during surgery, when compared to the posterior approach. It avoids the contaminated transoral or transnasal corridor. Risk of injury to the vertebral artery may be avoided while utilizing this procedure. An additional odontoidectomy can be performed simultaneously utilizing the same anterior approach, if C1-2 joint reduction has not been found to be satisfactory after joint manipulation. The procedure also facilitates the relative sparing of the anterior arch of atlas.
A limited experience with the technique, the small number of patients recruited and a short follow-up are the limitations of the technique. Proper fusion may not occur in the presence of osteoporosis. Patients with tuberculous or pathological involvement of the C1–C2 facet joint may not be ideal candidates for this procedure. In a patient who has a posterior thecal compression, an ideal treatment would be to perform decompression utilizing a posterior approach.
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