• Mikayel Grigoryan, John A Lynch, Anke L Fierlinger, Ali Guermazi, Bo Fan, David B MacLean, Ainsley MacLean, and Harry K Genant.
• Osteoporosis and Arthritis Research Group, Department of Radiology, 350 Parnassus Avenue, Suite 150, San Francisco, CA 94117, USA.
• Acad Radiol. 2003 Nov 1; 10 (11): 1267-73.

Rationale And ObjectivesDevelopment of new agents to induce fracture healing requires more sensitive methods to detect early changes in fracture repair. The aims of this study were to determine quantitative and qualitative features of fracture healing using volumetric computed tomography (CT) and to compare them with conventional radiography during the weeks following uncomplicated fractures of the appendicular skeleton.Materials And Methods39 otherwise healthy men and women with acute, closed fractures of the distal radius, tibial and/or fibular malleoli, or tibial shaft, were enrolled and underwent CT and X-ray imaging at 1, 2, 4, 8, 12, and 16 (tibial shaft only) weeks post fracture. Qualitative assessment included fracture line/margins, fracture gap, external callus appearance, callus-to-cortex ratio, bridging, and radiologic union. Quantitative assessment of CT density changes (Hounsfield units [HU]) in the fracture gap was performed in a subset of 8 fracture patients using MEDx multimodality image analysis software (Sterling,VA). The analysis was performed by drawing free form regions of interest (ROI) covering the fracture gap on baseline (week 1) images and by automated registration of the follow-up images to the baseline co-ordinate system.ResultsThe mean time to achieve radiologic union on CT was slightly shorter than on X-rays for radial and tibial shaft fractures (7.3 vs. 8.0 weeks, P = .1). Blurring of the fracture margins and reactive sclerosis were the earliest signs of healing in both modalities. External callus formation was evident in 11 cases and was detected earlier with CT technique. Overall, CT images allowed for more complete and detailed visualization of healing compared with conventional X-rays, which were limited by cast and fixation hardware superimposition, especially in subjects with malleolar and distal radial fractures. Quantitative evaluation showed good intraobserver and interobserver reproducibility and a statistically significant correlation to qualitative changes.ConclusionOur methods of fracture healing assessment are reliable tools that are able to detect early changes in normal bone healing and may serve as useful additions to subjective image analysis in monitoring fracture healing in clinical trials. CT shows some advantages over conventional X-rays in evaluation of early fracture healing.

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