The open-mouth temporomandibular joint (TMJ) scan is a better diagnostic tool than closed-mouth TMJ scan and SPECT in temporomandibular osteoarthritis

Objectives We compared the diagnostic performance among closed-mouth planar temporomandibular joint (TMJ) bone scan (CM scan), closed-mouth TMJ SPECT (CM SPECT) and open-mouth planar TMJ bone scan (OM scan) using Tc-99m HDP.

Methods We enrolled 22 patients with suspected TMJ osteoarthritis who underwent CM scan, CM SPECT and OM scan. Positive finding was defined as the presence of focal uptake in TMJ visually. Additionally, we drew two kind of region of interest (ROI) over TMJ site and measured the count from both inner (IC) and outer (OC) square ROI. We induced parameter (localization index, LI) to quantify focal uptake by the equation: IC/(OC - IC). We correlated imaging findings with osteoarthritis, which was defined as presence of both arthralgia and crepitus, and compared the diagnostic performances between these methods with the area under curve (AUC) of receiver operating characteristic curve (ROC) analysis.

Results Fifteen (34.1%) of 44 joints were diagnosed as osteoarthritis. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy is 93.3%, 55.2%, 51.9%, 94.1% and 68.2% (CM scan); 86.7%, 65.5%, 56.5%, 90.5% and 72.7% (CM SPECT); 86.7%, 86.2%, 76.5%, 92.6% and 86.4% (OM scan); , respectively. The AUC of OM scan (0.864) was the largest compared CM scan (0.743) or CM SPECT (0.761) (OM scan vs. CM scan: P=0.027, OM scan vs. CM SPECT: P=0.023, respectively). On the other hand, the diagnostic value of LI in OM scan was not higher than those of other methods in spite of the significant result in ROC analysis (cutoff value: 1.48, AUC=0.680, P=0.031).

Conclusions The diagnostic performance of OM scan is better than CM scan or CM SPECT for TMJ osteoarthritis. Therefore, OM scan should be added for accurate diagnosis in patients with suspected TMJ osteoarthritis.