How to Choose the Measurement Methods for Cage Subsidence Following Anterior Cervical Discectomy and Fusion?

Area of Science:

• Spine surgery
• Orthopedic research
• Radiographic analysis

Background:

• Standardized methods for measuring cage subsidence post-anterior cervical discectomy and fusion (ACDF) are lacking.
• Existing radiographic approaches for assessing subsidence have not been fully validated for reliability and clinical correlation.

Purpose of the Study:

• To evaluate three radiographic methods for measuring cage subsidence following ACDF.
• To identify the most reliable method for assessing subsidence and its clinical relevance.

Main Methods:

• Compared three methods: cage migration into endplate height (ΔCMH), change in disc space height (ΔDH), and change in middle segment height (ΔMSH).
• Assessed reliability using interclass correlation coefficients (ICCs).
• Evaluated clinical relevance using Spearman's correlation coefficient.

Main Results:

• All three methods demonstrated good reliability, with ΔMSH showing the highest intra- and inter-observer ICCs.
• Significant differences were found between ΔDH and ΔCMH/ΔMSH methods, indicating they are not interchangeable.
• ΔMSH measurements correlated well with clinical outcomes, unlike ΔDH and ΔCMH.

Conclusions:

• The ΔDH and ΔCMH/ΔMSH methods are not interchangeable for measuring subsidence in ACDF.
• The ΔMSH method is recommended for measuring cage subsidence due to its superior reliability and clinical correlation.