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Abstract

Introduction: Occipito-cervical fusion is a standard treatment for craniovertebral junction (CVJ) instability and myelopathy. The technique has evolved from onlay bone grafting with halo immobilisation to rigid internal fixation with pedicle screws and rods construct, allowing early mobilisation and improving fusion rates. We describe our experience with the posterior-only surgical technique using enabling technologies, avoiding facet joint exposure and its associated complications.

Methodology: A total of 19 patients who underwent occipito-cervical fusion for CVJ pathologies were evaluated. These patients were followed up for a minimum of 24 months. Clinical assessment included Visual Analog Scale (VAS), Neck Disability Index (NDI), Nurick grade, and modified Japanese Orthopaedic Association (mJOA) scores. Radiological parameters, McGregor slope, occiput-C2 angle (O-C2), C2-C7 lordosis, and posterior occipito-cervical angle (POCA), were evaluated on lateral radiographs. Fusion was confirmed via CT scan by the presence of bony trabeculae between the occiput and C2 lamina.

Results: Of the 19 patients, 18 (94.7%) achieved radiological fusion on follow-up CT scan, showing bony trabeculae often forming around the rods. Clinically, mean VAS improved from 7.4 to 1.8, NDI from 38.6 to 15.8, Nurick grade from 3.2 to 0.9, and mJOA from 10.6 to 15.4. Radiologically, the McGregor slope, O-C2 angle, and POCA showed significant improvement postoperatively, indicating better alignment.

Conclusion: Posterior-only occipito-cervical fusion using modern technologies results in high fusion rates, clinical improvement, and radiological correction, while avoiding the morbidity associated with anterior approaches and facet joint exposure.

Introduction

Occipito-cervical fusion, as its name suggests, is the process of fixation of the cranio-vertebral junction (CVJ) with bone grafting to achieve bony fusion between the occiput and the axis or the sub-axial cervical spine. The procedure is widely employed as an umbrella treatment for various CVJ pathologies of congenital, inflammatory, traumatic, infective, or degenerative aetiologies. Foerster described occipito-cervical fusion using a fibula strut graft in 1927 [1]. The technique has evolved immensely over the years from on-lay bone grafting with or without wires, rods, or pins [2-4], providing unstable fixation that demands postoperative immobilization, despite which failure rates have been reported to be high [5,6]. The advent of screws, plates, and rod constructs [7-10], which provide rigid fixation, obviates the need for prolonged immobilization and results in much better fusion rates. This evolution has improved the patient outcomes with reduced complications.

In addition to instrumentation, various methods for achieving occipito-cervical bone grafting have been described. Autologous iliac bone graft has been described to be placed over a trough made in the base of the occiput and fixed with wires or cables [11]. Paired autologous ribs have also been described to be used as a structural bone graft in place of the iliac crest, with the advantage of fitting closely to the anatomy of the occipito-cervical junction [12]. For the reduction of basilar invagination and irreducible atlanto-axial dislocation with atlas assimilation, a novel technique called DCER (Distraction, Compression, Extension, and Reduction) has been described, where the joint between the occipital condyles and the superior articular surface of the atlas lateral mass is explored. A spacer is placed after denuding the cartilaginous surface, which acts as a fulcrum, over which the reduction of the basilar invagination or the atlanto-axial dislocation takes place [13]. However, access to the facet joint is difficult and is associated with significant blood loss, increased surgical time, and chances of inadvertent vertebral injury.

We present our institutional experience of 19 cases of CVJ pathologies, including basilar invagination and atlanto-axial dislocation, who presented with symptoms of myelopathy of variable duration, with or without supra-axial neck pain, managed with occipito-cervical fusion using intra-operative three-dimensional (3D) CT scan and navigation. Neck extension and posterior distraction were performed under intra-operative neuromonitoring (IONM), while connecting the rods from the occiput to screws in the subaxial cervical spine in all cases to reduce basilar invagination and retro-odontoid tilt. This manoeuvre relieves the compression over the spinal cord at the CVJ. A copious amount of autologous cancellous bone graft was harvested from the posterior superior iliac spine, which was placed over the decorticated occiput and laminae to achieve fusion. These patients were evaluated clinically and radiologically for a minimum follow-up period of 24 months. We believe that with the optimal use of enabling technologies, such a complex surgery can be performed efficiently and safely, obviating the need for facet exploration and associated complications.

Materials & Methods

This was a Prospective Cohort Analysis at the Stavya Spine Hospital and Research Institute, Ahmedabad, Gujarat, India. The study was approved by the Institutional Ethics Committee of Stavya Spine Hospital and Research Institute (study protocol code: SSHRI/CS/NS/RetroOCF/BRDDD/50/07.22) and is registered with the Clinical Trials Registry - India (registration number: CTRI/2022/09/045401).

Study population

The primary inclusion criteria were craniovertebral pathologies (basilar invagination or atlanto-axial dislocation) warranting occipito-cervical fusion surgery, only posterior surgeries with screws, plates, and rods, and patients willing to undergo 24-month follow-up. Patients were...(More)

For more info please read, Occipito-Cervical Fusion Using Screw Rod Plate System in Craniocervical Pathologies, by Cureus