Condylar hyperplasia: correlation of histological and scintigraphic features

Scintigaphy using 99mTc-MDP is widely advocated as a method of diagnosis and presurgical assessment of patients with condylar hyperplasia. A previous study has demonstrated that hyperplasia of the mandibular condyle is characterized histologically by the presence of an uninterrupted layer of undiffentiated germinative mesenchyme cells, a layer of hypertrophic cartilage and the presence of islands of chondrocytes in the subchondral trabecular bone. This study was undertaken to determine whether there was any association between the degree of 99mTc-MDP uptake and the histological features of condylar hyperplasia. The parameters examined were trabecular bone volume, depth of cartilage islands and the presence of forming and resorbing surfaces. The images were analyzed by three experienced observers, who ranked the images according to degree of asymmetry between sides and the degree of uptake on the affected side. There was a significant correlation between the proportions of resorbing and osteoid covered bone surfaces and scintigraphic appearances. The rank correlations were rs = 0.55 (P = 0.3) between the resorptive surfaces and degree of symmetry and rs = 0.53 (P = 0.04) between the osteoid surfaces and absolute uptake. The correlation was higher for both methods (rs = 0.64 in each case) when the osteoid surface and resorptive surface measurements were combined. The results indicate that visual examination of radioisotope bone scans by experienced observers is a valid form of assessment of bone activity in condylar hyperplasia.