Modified techniques to prevent sagittal imbalance after cervical arthroplasty

Area of Science:

• Spine surgery
• Orthopedic biomechanics
• Cervical spine research

Background:

• Cervical arthroplasty aims to preserve motion but faces challenges with kyphosis development.
• Current literature lacks proven methods to prevent kyphosis post-arthroplasty.
• Previous studies on insertion angle focused only on endplate kyphosis, with limited prediction of overall sagittal alignment.

Purpose of the Study:

• To evaluate if modifying disc insertion angle and depth prevents cervical kyphosis after single-level arthroplasty.
• To determine the correlation between insertion parameters and postoperative sagittal alignment.

Main Methods:

• Retrospective analysis of 41 patients undergoing single-level cervical arthroplasty with the Bryan disc.
• Long-term radiographic assessment including neutral cervical radiographs.
• Linear regression analysis of insertion angle, depth, and various spinal alignment parameters.

Main Results:

• Disc insertion angle and depth showed a significant negative correlation with postoperative shell angle.
• A lordotic insertion angle and anterior disc placement resulted in lordosis of the shell angle.
• Insertion angle demonstrated a tendency to correlate with overall sagittal alignment, suggesting potential paradoxical biomechanical stress.

Conclusions:

• Cervical arthroplasty with the Bryan disc yields favorable outcomes but carries risks of adverse events.
• Adjusting disc insertion angle and depth is a viable strategy to prevent postoperative sagittal imbalance.
• Further research is needed to understand unexpected compensatory biomechanical loads.