Sagittal Reconstruction of the Atlantoaxial Lateral Mass Complex with an Intra-Articular Cage Fusion Technique for Degenerative Atlantoaxial Instability

OBJECTIVE: To evaluate outcomes of sagittal recon-struction of the atlantoaxial lateral mass complex using a modified intra-articular cage fusion technique for treating degenerative atlantoaxial instability.METHODS: Data from 15 patients with degenerative atlantoaxial instability were retrospectively reviewed. All patients underwent posterior reduction and intra-articular fusion with a cage filled with local autologous bone. Atlantodental interval values on plain radiography in flexion before and after surgery were recorded. Bone fusion was evaluated on computed tomography recon-struction, and bone fusion time was recorded. Lateral atlantoaxial joint space height before and after surgery was measured on coronal computed tomography recon-struction. Japanese Orthopaedic Association score and visual analog scale score for neck pain before surgery and at final follow-up were compared.RESULTS: Mean follow-up time was 40.7 & PLUSMN; 13.4 months. All patients achieved good reduction and solid bone fusion at follow-up. Mean fusion time was 4.4 & PLUSMN; 1.1 months. Atlantodental interval decreased from 8.6 & PLUSMN; 1.5 mm pre-operatively to 1.9 & PLUSMN; 0.5 mm at final follow-up (P < 0.05). Lateral atlantoaxial joint space height significantly improved from 1.7 & PLUSMN; 0.5 mm preoperatively to 4.7 & PLUSMN; 0.3 mm at final follow-up (P < 0.05). Japanese Orthopaedic Asso-ciation score significantly improved from 14.9 & PLUSMN; 1.5 pre-operatively to 16.7 & PLUSMN; 0.6 at final follow-up (P< 0.05). Visual analog scale score for neck pain markedly decreased from 4.5 & PLUSMN; 1.8 preoperatively to 0.5 & PLUSMN; 0.6 at final follow-up (P < 0.05).CONCLUSIONS: Posterior reduction and intra-articular cage fusion with a C2 nerve root preservation technique is effective in treatment of degenerative atlantoaxial instability. Satisfactory reconstruction of the sagittal alignment and the height of atlantoaxial complex can be achieved.