• Kwang-Sup Song, Piyaskulkaew Chaiwat, Han Jo Kim, Addisu Mesfin, Sang-Min Park, and K Daniel Riew.
• *Department of Orthopaedic Surgery, Chung-Ang University, College of Medicine, Seoul, Korea; and †Department of Orthopaedic Surgery, Washington University in St. Louis, St. Louis, MO.
• Spine. 2013 Dec 1;38(25):2171-7.

Study DesignRetrospective study developing diagnostic criteria.ObjectiveTo validate 2 computed tomography-based findings, extragraft bone bridging (ExGBB) and intragraft bone bridging (InGBB), as diagnostic criteria for anterior cervical fusion using subsequent surgical confirmation and to demonstrate the different diagnostic accuracy on the basis of the graft material used.Summary Of Background DataThe accuracy and the methodology for evaluating bone bridging on computed tomographic scans to determine anterior cervical fusion status have not been validated or standardized.MethodsOne hundred ten patients with 254 surgically explored segments along with reconstructed computed tomographic scans were included. Bone bridging at each cervical level was assessed for ExGBB and InGBB. ExGBB was defined as complete cortical bridging at any peripheral margins (anterior, posterior, left, or right) of the operated disc space, outside of the graft. InGBB was defined as cortical or trabecular bridging within the confines of the graft only. ExGBB and InGBB were serially evaluated on reformatted coronal and sagittal views by 3 independent raters. The reliabilities and validities correlated with surgical exploration were evaluated.ResultsSurgical exploration revealed 123 fused and 131 pseudarthrosis segments. The reliability of 3 raters showed near perfect agreement for ExGBB and substantial agreement for InGBB. ExGBB also had higher validity for all raters than did InGBB. The autocortical graft group had the highest accuracy for both InGBB and ExGBB, with both values being nearly identical. The allograft group had the next highest validity values. For the cage group, InGBB had the lowest specificity (53.2%) and positive predictive value (35.5%), whereas ExGBB had 100% sensitivity and negative predictive value.ConclusionExGBB seems to be a far more reliable and accurate to determine anterior cervical fusion. The diagnostic criteria using bone bridging should be different based on the intradiscal materials. With cages in particular, InGBB seems unreliable and ExGBB is necessary to determine anterior cervical fusion.

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