Population Analysis of Masseter Muscle Tension Using Shear Wave Ultrasonography across Different Disease States

Abstract

Objective: This study aimed to evaluate the distribution and trends of masseter muscle tension in patients with temporomandibular joint (TMJ) pain, examining gender-specific differences and the impact of various TMJ disorders. Methods: From January 2020 to June 2024, a total of 734 patients presenting with facial pain radiating to the head and neck, localized around and extending from the TMJ, were referred for ultrasonographic examination. After applying exclusion criteria, 535 patients (72.9%) were included in the study. The patient cohort consisted of 343 females (64.1%) and 192 males (35.9%), with muscle tension measured using the Aixplorer ultrasound system equipped with a shear wave device. Data were collected and analyzed across different age groups and TMJ conditions, including "no changes", "exudate", "arthrosis", and "disc displacement". Results: The study found that males exhibited higher muscle tension across all conditions, particularly in the "no changes" (40.4 kPa vs. 32.1 kPa, 25.9% higher) and "exudate" (38.5 kPa vs. 29.7 kPa, 29.6% higher) categories, indicating increased muscle strain and inflammation during middle age. In females, a trend of decreasing muscle tension with age was observed, with a significant reduction from 36.2 kPa in the 20-30 age group to 24.3 kPa in the 60-70 age group (32.9% reduction), suggesting a reduction in muscle mass or strength due to aging. Both genders showed high muscle tension in the presence of exudate, with females peaking in the 40-50 age group at 37.1 kPa and males peaking earlier in the 20-30 age group at 41.2 kPa (10.9% higher in males), highlighting potential gender differences in inflammatory response. In the arthrosis group, males displayed a consistent increase in muscle tension with age, peaking at 37.5 kPa in the 50-60 age group (50.7% increase from the 20-30 age group), while females showed high tension, particularly in the 40-50 age group at 31.0 kPa (82.4% higher compared to the 20-30 age group), indicating the need for targeted joint health interventions in middle-aged women. Conclusions: This study reveals significant gender-specific differences in masseter muscle tension among patients with TMJ pain. Males were found to be more affected by muscle strain and inflammation during middle age, whereas females showed a significant decrease in muscle tension with age. The presence of exudate significantly impacted muscle tension across all age groups for both genders. These findings underscore the importance of tailored clinical interventions and preventive strategies to manage TMJ disorders effectively.

Keywords: elastography; masseter muscle; shear wave; temporomandibular disorders.

Figure 1

An example of ROI placement of the masseter muscle with readings of muscle tension (a). Position of the probe during examination of the patient (b). Distance between black dots where the probe was placed (c).

Figure 2

Scheme presenting the plan of the study and data management (area of statistical analysis).

Figure 3

The distribution of patient numbers in different age groups (five from 20 yo. to 70 yo.) of age groups. Male and female are compared side by side (light blue and red, respectively).

Figure 4

The changes in muscle tension across different age groups for females and males (light grey and blue), which presented no visible changes in the ultrasonographic picture in the female group. In the female group, there was a gradual increase in muscle tension until middle age (40–50), observed then with a decrease in older age. In the male group, there was higher muscle tension in comparison to women, which was observed in younger and middle-aged groups, peaking at 40–50 years.

Figure 5

The changes of muscle tension across different age groups for the female and male groups (light red and red, respectively), which presented exudate (inflammation) in the ultrasonographic picture. In the case of this condition, in the female group, high muscle tension due to inflammation peaked in younger (20–30) to middle age (40–50) and then decreased. However, in men with inflammation, consistently high muscle tension was observed with a peak in younger age (20–30) and marked decrease in older age (60–70).

Figure 6

The changes of muscle tension across different age groups for the female and male groups (light green and green, respectively), which presented arthrosis (degeneration) in the ultrasonographic picture. In the female group, muscle tension increased with age, peaking at 40–50, which may correlate with the progression of joint degeneration. In the male population, higher muscle tension in younger and middle-aged groups in comparison to women was observed, peaking at 50–60, probably with correlation with severe joint debridement.

Figure 7

The changes of muscle tension across different age groups for the female and male groups (yellow and orange, respectively), which presented disk displacement in the ultrasonographic picture. In the male cohort, increased tension was observed in comparison to the female group, with a peak in younger and middle age in females, with joint instability presenting less impact on muscle tension increasing but being relatively stable thought life.

Figure 8

A summary of the influence of the different conditions across females and males of different ages.