The association between forward head posture and masticatory muscle pressure pain thresholds in patients with temporomandibular joint dissorders: a cross-sectional observational study.

OBJECTIVES: Forward head posture (FHP) is common in patients with temporomandibular joint disorders (TMDs); however, whether it contributes to TMD symptoms remains unclear. The aim of this study was to investigate the association between (1) FHP and masticatory muscle pressure pain thresholds (PPTs) and (2) neck muscle and masticatory muscle PPTs. MATERIALS AND METHODS: A total of 145 patients diagnosed with TMD were recruited between December 2020 and April 2021. Data regarding FHP and neck and masticatory muscle PPTs were collected. FHP was characterized by the craniocervical angle (CVA) measured between the horizontal line through C7 and the line between the tragus of the ear and C7. Patients were divided into either the FHP group (CVA </= 51 degrees ) or the non-FHP group. Differences in the masseter and temporalis muscle PPTs between the two groups were analyzed using the Mann-Whitney U test. The correlation between the CVA, neck, and masticatory muscle PPTs in all patients was determined by Spearman's correlation analysis. RESULTS: There were 70 patients in the FHP group and 75 patients in the non-FHP group. No significant difference in masseter and temporalis muscle PPTs was found between the two groups (p > 0.05). No correlation was found between FHP and masticatory muscle PPTs (p > 0.05). A significant association was found between the neck muscle and masticatory muscle PPTs (p < 0.05). The C5-C6 pillar and masticatory PPTs were either moderately (r = 0.435, masseter muscle) or strongly (r = 0.608, temporalis muscle) correlated, while the correlation between the trapezius and masticatory muscles was moderate (r = 0.378, masseter muscle and r = 0.461, temporalis muscle). CONCLUSION: FHP was not directly associated with masticatory muscle PPTs. Masticatory muscle PPTs were strongly or moderately associated with neck muscle PPTs. Therefore, the presence of neck pain, not the degree of FHP, in patients with TMD is of significance. CLINICAL RELEVANCE: In TMD treatment, we should pay attention to and actively relieve neck pain.