Ichiro Okano, Conor Jones, Stephan N. Salzmann, Marie–Jacqueline Reisener, Oliver C. Sax, Colleen Rentenberger, Jennifer Shue, John A. Carrino, Andrew A. Sama, Frank P. Cammisa, Federico P. Girardi, Alexander P. Hughes


May 2020, Volume 29, Issue 5, pp 1131 - 1140 Original Article Read Full Article 10.1007/s00586-020-06348-0

First Online: 04 March 2020

Endplate volumetric bone mineral density measured by quantitative computed tomography as a novel predictive measure of severe cage subsidence after standalone lateral lumbar fusion

Purpose

Quantitative computed tomography (QCT) is an alternate imaging method to dual X-ray absorptiometry to measure bone mineral density (BMD). One advantage of QCT is that it allows site-specific volumetric BMD (vBMD) measurements in a small region. In this study, we utilized site-specific, endplate vBMD (EP-vBMD) as a potential predictive marker of severe cage subsidence in standalone lateral lumbar interbody fusion (SA-LLIF) patients and conducted a retrospective comparative study between EP-vBMD and trabecular vBMDs (Tb-vBMD) in the vertebrae.

Methods

Patients undergoing SA-LLIF from 2007 to 2016 were retrospectively reviewed. EP-vBMD was defined as the average of the upper and lower endplate volumetric BMDs measured in cortical and trabecular bone included in a 5-mm area of interest beneath the cage contact surfaces. We compared Tb-vBMDs and EP-vBMDs between disk levels that had severe cage subsidence and levels with no severe subsidence.

Results

Both EP-vBMD and Tb-vBMD could be measured in 210 levels of 96 patients. Severe cage subsidence was observed in 58 levels in 38 patients. Median (IQR) Tb-vBMD was 120.5 mg/cm3 (100.8–153.7) in the non-severe subsidence group and 117.9 mg/cm3 (90.6–149.5) in the severe subsidence group (p = 0.393), whereas EP-vBMD was significantly lower in the severe subsidence group than the non-severe subsidence group (non-severe subsidence 257.4 mg/cm3 (216.3–299.4), severe subsidence 233.5 mg/cm3 (193.4–273.3), p = 0.026).

Conclusion

We introduced a novel site-specific vBMD measurement for cage subsidence risk assessment. Our results showed that EP-vBMD was a reproducible measurement and appeared more predictive for severe cage subsidence after SA-LLIF than Tb-vBMD.

Graphic abstract

These slides can be retrieved under Electronic Supplementary Material. [graphic not available: see fulltext]


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