Asymmetric uptake of Tc-99m HDP on temporomandibular joint predicts prognosis of temporomandibular joint disease

Abstract

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Objectives: There is no reliable prognostic predictor of temporomandibular joint (TMJ) disease. The aim of the study was to evaluate the usefulness of Tc-99m HDP bone scan for the prognosis assessment of TMJ disease.

Methods: 94 TMJ disease patients (M:F=18:76; mean age, 33.4±14.0y) who underwent pre-therapeutic bone scan were enrolled between January 2005 and July 2007. Planar bone scan images were obtained at right and left lateral skull views 3 hrs post Tc-99m HDP injection (1295 MBq). TMJ uptake of Tc-99m HDP was quantitated using 13X13 pixel-square region-of-interest (ROI) over TMJ. Background counts were measured using an ROI over parietal area of lateral skull view. TMJ uptake ratio was calculated as; (TMJ–background)/background. Asymmetricity index for involved TMJ (AI-involve) was defined as; TMJ uptake ratio of involved/non-involved joint. Asymmetricity index for greater uptake TMJ (AI-greater) was defined as; TMJ uptake ratio of greater/smaller TMJ uptake. Splint therapy was applied to all patients with mean duration of 7 months (range; 3-34 months). Therapeutic efficacy was dichotomized as improved or non-improved in consideration of mandibular movement, TMJ noise, pain, and tenderness.

Results: 76 patients experienced improvement, whereas 18 non-improvement. There was no significant difference between improved vs. non-improved patients regarding TMJ uptake ratio of involved joint (2.92±0.82 vs. 2.91±0.66), and AI-involve (1.16±0.22 vs. 1.10±0.12) (p>0.05, t-test). However, AI-greater was significantly higher in improved than non-improved patients (1.20±0.19 vs. 1.13±0.09, p<0.05, t-test).

Conclusions: Regardless of disease involvement of TMJ, asymmetricities of Tc-99m HDP uptake were more frequently found in improved group after therapy. Tc-99m HDP bone scan can predict the prognosis of TMJ disease.