Risk Factors for Subaxial Kyphosis After Posterior C1-C2 Fusion for Atlantoaxial Dislocation.

Area of Science:

• Orthopedics
• Neurosurgery
• Spine Surgery

Background:

• Posterior C1-C2 fusion is a common procedure for atlantoaxial dislocation.
• Understanding the impact on cervical radiologic parameters and risk factors for complications like postoperative subaxial kyphosis (PSK) is crucial.

Purpose of the Study:

• To evaluate changes in the correlation of cervical radiologic parameters after posterior C1-C2 fusion.
• To identify risk factors associated with the development of PSK.

Main Methods:

• Retrospective review of 38 patients undergoing posterior atlantoaxial fusion.
• Measurement of cervical radiologic parameters (O-C1, C1-C2, O-C2, C2-C7 Cobb angles, O-C1 ROM, T1 slope, C2-C7 SVA) preoperatively and one year postoperatively.
• Exclusion of patients with prior cervical surgery, basilar invagination, or extensive fusion.

Main Results:

• The O-C1 angle correlated significantly with the C2-C7 angle postoperatively, unlike preoperatively.
• The incidence of PSK was 23.7%.
• Female sex, decreased O-C1 range of motion (ROM), and a postoperative C1-C2 angle between 15°-25° were significant risk factors for PSK.

Conclusions:

• Posterior C1-C2 fusion alters the correlation between upper and subaxial cervical spine parameters.
• O-C1 angle becomes a critical parameter correlating with the C2-C7 angle post-fusion.
• Female patients, reduced O-C1 ROM, and specific C1-C2 angles are associated with increased PSK risk.