Lateral Mass Fusion Using 3D-Printed Anatomic Cages for Atlantoaxial Dislocation: A Multicenter Comparison With Iliac Crest Autograft

BACKGROUND AND OBJECTIVES: Atlantoaxial dislocation (AAD) is a high-risk condition that can lead to significant mortality. Lateral mass fusion offers structural stability and reduction, yet no standardized fusion device currently exists for consistent atlantoaxial fixation. This study compares the clinical outcomes of a novel anatomic cage vs iliac crest autograft in treating AAD. METHODS: Radiographic, laboratory, and clinical outcomes were retrospectively compared between 2 surgical groups: one treated with an iliac crest autograft by a traditional posterior approach, the other treated with an anatomic cage using an intermuscular approach. Health-related quality-of-life factors were also analyzed. RESULTS: One hundred nineteen patients underwent fusion with iliac crest autograft and 105 with anatomic cages were finally included. The iliac crest group had a shorter operative time (P = .043), but the anatomic cage group had significantly less intraoperative blood loss, shorter hospitalization, and fewer C2 neurological symptoms (all P < .05). Bony fusion was similar between 2 groups (3.3 [0.6] months vs 3.1 [0.4] months, P = .163). Compared with the iliac crest group, the anatomic cage group showed greater improvements in lateral mass interspace height (LMIH, P < .001). Inflammatory markers were significantly lower at postoperative day 3 in the anatomic cage group. Improvement in pain (Visual Analog Scale) differed significantly between groups (ΔP <.001). Regression analysis showed that age <55 years was independently associated with greater Neck Disability Index improvement (P = .025), while C1-C2 Cobb angle and cervicomedullary angle correlated with postoperative Japanese Orthopaedic Association and Neck Disability Index scores. LMIH was significantly associated with C2 neurological symptoms (P = .015). CONCLUSION: Lateral mass fusion using the 3-dimensional-printed anatomic cages by an intermuscular approach is a safe and effective treatment of AAD. It offers improved radiological outcomes, preserves C2 nerve root integrity, and reduces early postoperative inflammation. In addition, intraoperative restoration of LMIH may reduce neurological symptoms in patients with AAD.