A Comparison of Radiostereometric Analysis and Computed Tomography for the Assessment of Lumbar Spinal Fusion in a Sheep Model

Abstract

Study Design Prospective animal study. Objective The aim of this animal study is to evaluate the accuracy of radiostereometric analysis (RSA) compared with computed tomographic (CT) scan in the assessment of spinal fusion after anterior lumbar interbody fusion (ALIF) using histology as a gold standard. Methods Three non-adjacent ALIFs (L1–L2, L3–L4, and L5–L6) were performed in nine sheep. The sheep were divided into three groups of three sheep. All the animals were humanely killed immediately after having the last scheduled RSA. The lumbar spine was removed and in vitro fine cut CT and histopathology were performed. Results Using histological assessment as the gold standard for assessing fusion, RSA demonstrated better results (100% sensitivity and 66.7% specificity; positive predictive value [PPV] = 27.3%, negative predictive value [NPV] =100.0%) compared with CT (66.7% sensitivity and 60.0% specificity [PPV = 16.7%, NPV = 93.8%]). Conclusions RSA demonstrated higher sensitivity and specificity when compared with CT. Furthermore, RSA has the advantage of much lower radiation exposure compared with fine cut CT. Further studies are required to see if RSA remains superior to CT scan for the assessment spinal fusion in the clinical setting.Assessment of Class of Evidence (CoE) for individual studies of diagnostic test evaluationMethodological principleStudy design Prospective cohort designX Retrospective cohort design Case–control designBroad spectrum of patients with expected condition a Appropriate reference standard usedXAdequate description of test and reference for replicationXBlinded comparison with appropriate referenceXReference standard performed independently of testXEvidence levelII Note: Blank box indicates criterion not met, could not be determined, or information not reported by author or was not reported. aThis study contained nine animal subjects.

RSA in Spine: A Review

“…In addition, RSA measures rotation and translation in 3 dimensions, while DCRA just measures rotation around the transverse axis and translation in the sagittal plane. 28 , 62 – 64 …”

“…They concluded that RSA is as accurate as CT scan with minimal radiation exposure. 63 They also suggested using a special awl in creating the holes for RSA beads and gluing the beads into the hole using bone wax to improve the stability of the beads and improve the accuracy of the assessment. 63 …”