P54. Quantifying robustness: a novel method for objectively measuring spine fusion quality in a rat model

• Published in: The spine journal Vol. 24; no. 9; p. S89
• Main Authors: Hiltzik, David, Pagadala, Manasa, Lee, Justin, Jacome, Freddy, Cho, Sia, Sollenberger, Christopher, Hsu, Wellington K., Gibly, Romie, Hsu, Erin L.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.09.2024
• ISSN: 1529-9430
• DOI: 10.1016/j.spinee.2024.06.075

Successful spinal fusion is defined by robust bone bridging adjacent vertebrae. Current methods of assessing fusion success in animal models rely on subjective metrics such as manual palpation scoring or visual assessment on imaging. Objective confirmation of spinal fusion success and quantification of robustness would allow for greater confidence in study results as well as more precise comparisons. We propose a methodology for this purpose using 3D particle analysis on micro-computed tomography (uCT). N/A N/A N/A Seven Sprague-Dawley rats underwent L4-L5 posterolateral fusion with tricalcium phosphate putty. Animals were euthanized at 8 weeks postoperatively and fusion assessed via manual palpation (MP) using an established scoring system (scale: 0-2)2. Spines were imaged with uCT with voxel size of 6.5 micrometers. After binary segmentation, the bone formed between L4 and L5 transverse processes (TP) was analyzed using the three-dimensional particle analysis function of the BoneJ plugin for ImageJ. This protocol confirmed the presence/absence of bridging bone spanning L4-L5 . Single-voxel erosions were then applied to the segmented volume until particle analysis registered L4 and L5 as discrete particles, and the number of erosions was recorded (Resistance to Erosion, RtE). MP results were then compared to RtE scores via ROC curve and Bland-Altman analysis. On ROC curve analysis, area under the curve was 0.84 (p=0.035), sensitivity was 85.71%, and specificity was 100.0%. Bland-Altman plot showed the mean bias +/- SD between MP and RtE as 1.62 +/2.68. ROC curve and Bland-Altman analysis indicate that this RtE methodology has high sensitivity and specificity with low systemic bias and more quantitative objectivity compared to MP. Resistance to erosion has been validated as a proxy for robustness in other fields3, however this is the first application of this concept in bone imaging. However, when assessing fusions with multiple discrete paths of bridging bone, this method identifies and measures only the pathway with the largest minimum radius. This will be valuable for research involving spinal fusion as it provides more objective data and precise comparison among subjects than prior approaches. Further research is needed to fully validate this methodology in human and animal models. This abstract does not discuss or include any applicable devices or drugs.