Correlation between neck pressure pain threshold and forward head posture in patients with temporomandibular joint disorders

Objective: To investigate the association between neck muscles pressure pain thresholds (PPT) and forward head posture (FHP) in patients with temporomandibular disorders (TMD). Methods: A total of 145 TMD patients, including 23 males and 122 females with a median age of 28 years, were enrolled in the Department of Rehabilitation Medicine, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine from December 2019 to April 2020. Informations of FHP and neck muscles PPT were collected for all participants. FHP was characterized by the craniocervical angle (CVA) between C7, the tragus of the ear and the horizontal line. Each of the participants completed a questionaire of the neck disability index (NDI). The patients with CVA≤51 ° were asigned into FHP group, otherwise the patients with CVA>51° were asigned into non-FHP group. PPT were measured at the midpoint of the upper trapezius and 1 cm aside from C5-C6 articular pillars. Nonparametric test and Spearman correlation analysis were conducted for the data analysis. Results: There were 70 patients in the FHP group and 75 patients in the non-FHP group. The trapezius PPT of the FHP group [2.82(0.86) kg] was significantly higher than that of the non-FHP group [2.46(0.80) kg] (P 0.05). Low correlation was found between trapezius PPT and FHP negatively (r=-0.273, P 0.05). PPT in trapezius and C5-C6 was negatively correlated with NDI in moderate (r=-0.301, P<0.01) and low (r=-0.206, P<0.05) levels. Conclusions: The trapezius PPT was correlated with FHP negatively. The more FHP, the more pain tolerant of trapezius muscles. There was no correlation between neck function and FHP directly. The higher threshold was followed by better neck function.