No abstract

The new technique of C2 screw fixation allows rigid immobilization of the C1-C2 joint without significant risk of vertebral artery injury.

Objective: Surgery is indicated for basilar invagination (BI) in symptomatic patients. In many patients, symptoms and signs occur due to an upward-migrated and malaligned odontoid with fixed or mobile atlantoaxial instability. Posterior distraction and fixation of the atlantoaxial joints has evolved to become the standard of care, but has some inherent morbidity. In this study, we propose that the unilateral anterior submandibular retropharyngeal approach with customized wedge-shaped titanium cages inserted into both atlantoaxial joints and anterior atlantoaxial fixation with a plate screw construct is a safer and easier option in many cases of BI. Methods: From February 2014 to February 2019, 52 patients (age range, 15-78 years; 40 males and 12 females) with symptomatic BI with atlantoaxial dislocation and minimal sagittal facetal inclination and only mild Chiari malformation without syringomyelia were offered anterior submandibular retropharyngeal atlantoaxial distraction and fixation surgery. Results: Neurological improvement occurred in 80% of patients, while the neurological status of 20% remained unchanged. No patients worsened, and no major complications or mortality was observed. Conclusion: In properly selected cases of symptomatic BI, anterior wedge cage distraction with anterior atlantoaxial fixation is a safe and simple option.

Since 2008, 62 patients, 39 patients anterior trans articular screws, 23 patients anterior screw plate fixation, 40 males 22 females, AAD 42, tuberculosis 12, fixed AAD with basilar invagination 8. All patients underwent preoperative dynamic X rays of cranio vertebral junction, computerized tomography CT scan of C1 C2 static and dynamic study with bone window settings and 3D reconstruction, magnetic resonance imaging MRI and MR angiography to study course of vertebral artery. 1 Operative technique Anaesthesia Awake endoscopic nasal intubation and general anaesthesia. Position Supine with extension of the head and mild rotation to left side, lateral X ray image to confirm that mandible is at or above C2 body on extending the head. Skull tongs applied for intra operative manipulation. Stevenson's 1 technique for exposure to reach the prevertebral space at C1 C2. Curved from midline to angle of mandible at a distance of 2 cms below the mandibular margin to protect the marginal mandibular nerve. Skin and platysma flaps reflected bilaterally. Mylohyoid muscle divided from the midline to the angle of the mandible. Upper flap of mylohyoid muscle reflected upwards to expose the mandibular gland and the digastric muscle and stylohyoid muscle Fig. 1 5. Both muscles disconnected from the hyoid bone and reflected upwards to identify the hypoglossal nerve. Hypoglossal nerve separated from surrounding connective tissue to mobilize it upwards for 1 2 cms. Facial artery and vein identified and protected. Internal carotid artery pulsations felt and plane of dissection just medial to the artery to reach the retropharyngeal space on the anterior aspect of the C2 body. X ray imaging is performed to confirm position. Long bladed Langenbeck's retractors 6 8 cms used and anterior surface of C1 exposed with electrocautery and periosteal elevators. The C2 body was cleared of all soft tissue, anterior longitudinal ligament and longus colli divided to expose the atlanto axial joints bilaterally. The anterior joint capsule was cut with a no. 15 blade and the synovium exposed. The joint cartilage on either side was curetted with a 2 3 mm angled Karlin's curette till the posterior margin of the joint. Skull traction could be used manipulate and distract the joint for satisfactory decortications of both the C1 and C2 lateral mass surfaces of the joint till there was some bleeding from the cortical endplates. In cases with fixed C1 C2 dislocation all soft tissue between anterior arch of C1 and odontoid process was removed, a microdrill was used to drill a hole of 3 mm into the base of the odontoid

Unilateral anterior retropharyngeal approach was used in a case of basilar invagination with atlanto-axial instability. This approach provided easy access to both atlanto-axial joints. Wedge-shaped titanium cages were used to distract the joints and reduce the basilar invagination. Titanium plates with screws were used to fix the lateral mass of atlas with the body of axis, bilaterally. The anterior atlanto-axial joint distraction procedure has not been described in literature before seems to be an easy option in selected cases of craniovertebral anomalies and needs to be investigated by more surgeons.