Introduction: Conventionally, management of irreducible atlanto-axial dislocation (AAD) requires two operations, transoral odontoidectomy and fusion posteriorly. Both are major surgeries and require two different approaches. Author describes, in cadaver study,a single anterior approach to accomplish realignment and stabilization of irreducible atlanto-axial dislocation without odontoidectomy.
Methods: Anterior craniovertebral junction is exposed in ten cadavers. The odontoid is freed off the soft tissues and ligaments around including cruciate and apical with the help of sharp curved dissectors and knife. Both facet joints cleaned off circumferentially. AAD was created by manually pushing the odontoid backward and a model of irreducible AAD was created by placing a block of hydroxyapatite in the gap between anterior arch of atlas and odontoid. Horizontal limb of “Step-T-Plate” is fixed with cancellous screws on the lateral masses of atlas and vertical limb on axis by inserting a screw partially. The Distractor Blade device is engaged to the horizontal portion of “Step T Plate”superiorly and against the partially inserted screw of axis inferiorly. With distraction action of the device the axis is pulled downwards. The Odontoid Reducer device pulls the odontoid forward. Finally, two screws of atlas and two screws of axis are tightened.
Results: As the odontoid was pulled forward, with the help of Odontoid Reducer, the block of hydroxyapatite started to break into pieces indicating a good pulling force. Reduction was achieved in eight cases.In two cases the Odontoid Reducer slipped out due to poor quality of cadaver bone.
Conclusions: Anterior approach can perform caudal and forward repositioning of odontoid and stabilization, all by one approach without doing odontoidectomy. This approach targets the pathology directly and accomplishes the goal in one approach as against posterior approach which is indirect and involves stripping of major muscles and risk to blood vessels.
Patient Care: In irreducible AAD and probably in basilar invagination too this technique can perform the objective of treatment - reduction and stabilization by a single approach. Thus avoiding the trauma and risks involved in two major surgeries. The author has also introduced “Step T Plate”, Distractor Blade and Odontoid Reducer into the surgical armamentarium.
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Learning Objectives: By the conclusion of this session the participants
1. Will get to know a technique of pulling the Odontoid downwards and forwards by anterior trans-oral approach.
2. Will get introduced to new instruments such as "Step T Plate", Odontoid Distractor Blades and Odontoid Reducer