Study Design. Retrospective study developing diagnostic criteria.
Objective. To 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 Data. The accuracy and the methodology for evaluating bone bridging on computed tomographic scans to determine anterior cervical fusion status have not been validated or standardized.
Methods. One 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.
Results. Surgical 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.
Conclusion. ExGBB 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.
Level of Evidence: 2
Our study developing diagnostic criteria for anterior cervical fusion indicating extragraft bone bridging (ExGBB) seems to be very reliable and accurate. The patterns of bone bridging as diagnostic criteria could be different according to grafts used. In allograft and, especially cages used, ExGBB is a necessary finding whereas intragraft bone bridging could be unreliable.
*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.
Address correspondence and reprint requests to Kwang-Sup Song, MD, Department of Orthopaedic Surgery, Chung-Ang University Hospital, Heukseok-dong, Dongjak-gu, 224-1, Seoul, Korea; E-mail: firstname.lastname@example.org
Acknowledgment date: April 26, 2013. Revision date: August 22, 2013. Acceptance date: September 9, 2013.
The manuscript submitted does not contain information about medical device(s)/drug(s).
No funds were received in support of this work.
Relevant financial activities outside the submitted work: consultancy, expert testimony, grants, payment for lecture, royalties, stocks, travel/accommodations/meeting expenses.