Can Pixel Value Ratio be Used in the Assessment of Ceramic Bone Substitute Incorporation? Observations from a Pilot Study

BACKGROUND: Assessment of bone graft substitute incorporation is critical in the clinical decision making process and requires special investigations. We examined if the pixel value ratio (PVR) obtained in routine follow-up digital radiographs could be used for such assessment. MATERIAL/METHODS: Radiographic images were acquired using either computed radiography or flat panel digital radiography systems. The PVR from radiographs of thirty children with ceramic bone substitute grafting were analyzed using the software from the picture archival and communication system (PACS) workstation. Graft incorporation was also assessed using the van Hemert scale. Three independent observers (A, B, C) measured PVRs at two different time points during the first and the last follow-up visits. PVR was compared with the van Hemert scale scores and analyzed using Spearman’s rank correlation. RESULTS: The mean intra-observer reliability was 0.8996, and inter-observer reliabilities were 0.69 (A vs. C), 0.78 (A vs. B), and 0.85 (B vs. C) for the first follow-up visit and 0.74 (A vs. C), 0.82 (A vs. B), and 0.70 (B vs. C) for the last follow-up measurements. Spearman’s correlation showed a strong negative association between PVR values and van Hemert scale scores, as the healing process advanced on serial measurements at each follow-up (r=–0.94, n=60, z=–7.24, p≤0.0001). The reliability of the PVR measurements was assessed using an aluminum step wedge and ceramic graft. CONCLUSIONS: PVR is potentially a reliable indicator of bone graft incorporation and can aid in clinical decision making provided standard radiographic techniques are used.