Predicting cage subsidence after lumbar interbody fusion: a meta-analysis of opportunistic bone quality metrics.
Shaan Patel, Shiva A Nischal, Gargee Sree Nallankuka et al.
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In 30 seconds
This systematic review and meta-analysis assessed whether preoperative CT- and MRI-derived bone quality measures predict cage subsidence after degenerative lumbar interbody fusion. It included 36 observational studies with 5482 patients; 1679 (30.6%) developed subsidence. Patients with subsidence had poorer bone quality across the evaluated measures, including lower Hounsfield units (MD -26.9; p<.01). Pooled diagnostic accuracy was moderate to good, with AUCs ranging from 0.77 to 0.85. Meta-regression found no significant differences in discrimination between metrics, and analyses suggested risk modification rather than definitive rule-in or rule-out performance.
Key findings
- Of 5482 patients, 1679 (30.6%) developed cage subsidence.
- Subsidence was associated with lower Hounsfield units (MD -26.9; p<.01), lower CT-BMD (MD: -33.0; p<.01), and lower DEXA T-scores (MD: -0.77; p<.01).
- Patients with subsidence had higher VBQ (MD: 0.60; p<.01) and EBQ scores (MD: 0.68; p<.01).
- Pooled AUCs ranged from 0.77 to 0.85; differences between metrics were modest and nonsignificant on meta-regression.
Why it matters
Cage subsidence is linked to bone quality at the vertebral and endplate interface. The consistent associations across CT, MRI, and DEXA measures suggest that opportunistic imaging metrics may help characterize preoperative risk. However, their moderate-to-good discrimination and lack of definitive rule-in or rule-out performance mean they should inform risk assessment rather than be treated as conclusive predictors.
What to keep in mind
The evidence came from observational studies, so the findings establish associations rather than causal effects. Diagnostic performance was not definitive, and the abstract does not report a single metric as clearly superior.