Comparing apparent diffusion coefficient values of the masticatory muscles on diffusion-weighted magnetic resonance imaging in patients with temporomandibular joint osteoarthrosis

Aim: This study aimed to compare the apparent diffusion coefficient (ADC) values of the masticatory muscles between patients with and without temporomandibular joint osteoarthritis (TMJ-OA) on diffusion-weighted magnetic resonance imaging. Methods: This prospective study included 120 patients with temporomandibular disorders (TMD), including 60 patients with TMJ-OA and 60 without TMJ-OA, and 60 without TMD patients. All patients underwent magnetic resonance imaging of the TMJs at our hospital between November 2011 and January 2017. The regions of interest included the right and left lateral pterygoid muscles, medial pterygoid muscles, and masseter muscles on axial slices. Magnetic resonance images from the TMJ-OA and control groups were independently evaluated by two oral and maxillofacial radiologists. ADC values were compared between the two groups using Mann–Whitney U tests. Results: The respective mean ADC values of the lateral pterygoid muscles in patients with TMJ-OA and controls were 1.18 × 10⁻³ and 1.33 × 10⁻³ mm²/s, respectively. Those for the medial pterygoid muscles were 1.14 × 10⁻³ and 1.25 × 10⁻³ mm²/s, while those for the masseter muscles were 1.20 × 10⁻³ and 1.28 × 10⁻³ mm²/s, respectively. The mean ADC values of the normal lateral pterygoid, normal medial pterygoid, and normal masseter muscles were 1.29 × 10⁻³, 1.09 × 10⁻³, and 1.08 × 10⁻³ mm²/s, respectively. Conclusion: Among patients with TMDs, the ADC values of the masticatory muscles were significantly higher in patients without TMJ-OA than in those with TMJ-OA.