Axis II psychosocial findings predict effectiveness of TMJ hyaluronic acid injections

The objective was to investigate the correlation between levels of depression, somatization, and pain-related impairment, as assessed by the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMDs) axis II, and the treatment outcome of a cycle of five weekly injections of hyaluronic acid immediately following arthrocentesis. 57 consecutive patients with a diagnosis of temporomandibular joint (TMJ) osteoarthritis according to the RDC/TMD underwent the treatment protocol and a follow-up assessment at 6 months. Axis II findings were assessed as potential predictors of improvement in visual analogue scale (VAS) values at the end of the observation period with respect to baseline. The percentage of VAS improvement at the end of treatment was inversely related to all the psychosocial variables. The best fitting model identified pain-related impairment (p<0.001) and disability points (p<0.001) as the most significant predictors of VAS changes. The percentage of variance in the outcome variable explained by the significant predictors was high (R(2) 70.5%). All the RDC/TMD axis II psychosocial scores (depression, somatization, and pain-related impairment levels) were inversely correlated with therapeutic outcome. The clinical relevance of these findings is important, since psychosocial diagnosis may be even more important than physical evaluation in terms of prognostic impact.