Riew KD, et al. - Authors evaluated and validated the diagnostic accuracies of four radiographic fusion criteria using the results of surgical exploration. Results demonstrated the best association of the presence of extra-graft bridging bone (ExGBB) (anterior, posterior, or lateral to the graft or cage) with surgical exploration. On CT scans, a similar accuracy of the interspinous motion (ISM) criteria to that of conventional bridging bone criteria was seen. The highest validity values were demonstrated by criteria in arthrodesed segments with auto-cortical bone. Researchers noted an acceptable accuracy of ISM and ExGBB in cage group, but the conventional bridging bone and intragraft bridging bone (InGBB) were worse than guessing. They suggested the use of ISM and ExGBB criteria to increase accuracy in patients who undergo arthrodesis with cages.

Methods

• Experts conducted a retrospective, radiographic, comparative study on the patients who required anterior or posterior exploration of a previous anterior cervical arthrodesis level(s) ranging from C3-C4 to C7-T1 for suspected pseudarthrosis or adjacent-segment pathologies.
• In order to determine the four fusion criteria, they underwent radiologic examinations.
• They enrolled the patients whose images were taken at least 1 year after the index surgery, and 82 patients with 151 cervical segments were enrolled.
• They evaluated the inter- and intra-rater reliabilities and validity that correlated with the results of surgical exploration for the four fusion criteria using data (fusion or not) that were collected by two raters.
• They published radiographic fusion criteria viz, interspinous motion (ISM) < 1 mm and superjacent ISM ≥ 4 mm, seen on dynamic radiographs; conventional bridging bone, as seen on computed tomography (CT) scans; and extra-graft bridging bone (ExGBB) and intragraft bridging bone (InGBB), observed on multi-axial reconstructed CT scans.
• Two raters assesed the criteria (spine surgeons with 5 and 7 years of experience).
• Each criterion was evaluated by the raters twice at two different time points, 3-4 weeks apart.
• They assessed the first, ISM and conventional bridging bone on CT scans, followed by ExGBB and InGBB, with a time interval of 4 months.

Results

• Findings suggested that the inter- and intra-rater reliability values of the ExGBB (0.887-0.933) criteria were the highest, followed by those for the ISM (0.860-0.906), bridging bone (0.755-0.907), and InGBB (0.656-0.695) criteria.
• Results demonstrated that the validity values that associated with the exploration results were the highest for the ExGBB criteria (k=0.889), followed by the ISM (k=0.776), bridging bone (k=0.757), and InGBB (k=0.656) criteria and ExGBB showed the highest sensitivity (91.7%) and specificity (98.4%).
• As per data, regarding the graft materials that were used, all criteria had the highest values in the auto-cortical group and lowest values in the cage group .
• Of note, in autocortical group, sensitivity and specificity of ExGBB were 100%.
• Higher validity values for the ExGBB (k=0.663) and ISM (k=0.666) criteria were noted than those for the bridging bone (k=0.504) and InGBB (k=0.308) criteria.