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

Chengkun Zhao ¹, Shijie Wang ¹, Jingjing Zhang ¹

⁰Department of Orthopedics, The First Affiliated Hospital of Anhui Medical University, Hefei, China.

World Neurosurgery +

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September 19, 2025

View abstract on PubMed

Summary

The change in middle segment height (ΔMSH) method is the most reliable for measuring cage subsidence after anterior cervical discectomy and fusion, showing better clinical correlation than other radiographic techniques.

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.

Keywords:

Cage subsidence Cervical vertebrae Clinical outcomes Measurement method Radiographs Reliability