Quantitative analysis of planar bone scintigraphy in patients with unilateral condylar hyperplasia

This study compares quantitative analysis of planar bone scintigrams with visual interpretation in patients having unilateral condylar hyperplasia (UCH) and normal control subjects. The possibility of using a bony structure in a region near the condyle as an objective measurement of bone activity is assessed.

Planar bone scintigrams from 20 subjects suspected of having active UCH were analyzed both qualitatively and quantitatively. Bone activity was assessed in both condyles as well as in reference sites in the cervical spine and the skull. Percentile activities for both condyle regions and ratios using condyle activity versus reference regions were assessed.

All UCH patients had unilateral increased activity on qualitative visual interpretation of the bone scan. The mean percentile activities of the affected and unaffected condyles in the UCH group were significantly different at 55.3% and 44.7%, respectively (P < .001). No significant difference was found in the control group, with the ratios between left and right condyle being 49.5% and 50.5%, respectively (P = .46). In the ratios between the region of interest (ROI) in the condyles versus the ROIs selected for the cervical spine and the skull, a significant difference was noticed in the UCH group; however, there was a considerable overlap between condyle and reference ROI ratios. Symmetrical uptake of diphosphonate reliably excluded continued asymmetrical growth of the condyles.

Quantitative analysis of planar scintigrams in unilateral condylar hyperplasia patients was not found to be superior to qualitative visual interpretation of the scans. Because of a considerable overlap in condyle/reference ROI ratios, quantified ratios did not seem to be clinically helpful in the differentiation of a hyperplastic condyle from a normal condyle. In the case of unilateral increased condylar uptake of diphosphonate, clinical assessment is mandatory.