Transoral Atlantoaxial Release and Posterior Reduction by Occipitocervical Plate Fixation for the Treatment of Basilar Invagination with Irreducible Atlantoaxial Dislocation.

Prior studies have mainly assessed transoral odontoidectomy for basilar invagination with irreducible atlantoaxial dislocation. However, studies evaluating transoral release and posterior reduction with occipitocervical fixation in this setting are scarce.  From 2008 to 2013, 11 patients (6 men and 5 women; 23-67 years of age) with basilar invagination and irreducible atlantoaxial dislocation underwent surgery. They presented signs and symptoms of myelopathy or significant spinal cord injury, and were treated by transoral soft tissue release without odontoidectomy, under skull traction with heavy weight and by posterior reduction with occipitocervical plate fixation.  Patients were followed up for 10 to 42 months (average: 25.4 months). All achieved bony fusion; radiologically complete reduction was achieved in 10 cases, and partial reduction in 1. All patients showed an improved postoperative neurologic condition, indicated by increased muscle strength and decreased or now absent pathologic symptoms. The average Japanese Orthopaedic Association preoperative score of 10.5 points increased to 15.5 points postoperatively. These findings indicated an improvement rate of 76.1%. The efficiency rate was 90.9%.  Anterior transoral atlantoaxial release without odontoidectomy and posterior fixation is an efficient treatment of basilar invagination with irreducible atlantoaxial dislocation.