Necessary cervical kyphosis correction angle (NeckCA) for ideal alignment in cervical spinal deformity

Area of Science:

• Orthopedics
• Neurosurgery
• Spinal Surgery

Background:

• Cervical kyphosis correction is complex, with traditional methods sometimes leading to undercorrection due to compensatory changes.
• Achieving and maintaining optimal cervical alignment is crucial for patient outcomes in cervical spinal deformity (CSD) surgery.

Purpose of the Study:

• To propose and validate a novel formula for calculating the necessary cervical kyphosis correction angle (NeckCA).
• To assess the utility of NeckCA in predicting successful cervical alignment after CSD correction surgery.

Main Methods:

• A new radiographic parameter, NeckCA = C2 slope + center of gravity - T1 tilt - 15, was defined.
• Retrospective review of 29 CSD correction surgeries, categorizing patients into favorable (F) and unfavorable (U) radiological outcome groups.
• Receiver operating characteristic (ROC) curve analysis was used to evaluate NeckCA's predictive capacity.

Main Results:

• NeckCA demonstrated significant predictive capability for radiological outcomes (Area Under Curve = 0.806, p=0.006).
• Preoperative C2-7 sagittal vertical axis (SVA) was significantly greater in the unfavorable outcome group.
• No significant differences in preoperative cervical lordosis (CL), C2 slope (C2S), or segmental angle were found between groups.

Conclusions:

• The NeckCA formula provides a practical and predictive tool for preoperative planning in CSD correction.
• Incorporating the center of gravity - T1 tilt (COG-T1 tilt) into planning can counteract undercorrection.
• NeckCA aids in achieving and maintaining optimal cervical alignment, improving surgical outcomes.