Pressure Pain Threshold of the Upper Trapezius Trigger Point: A Systematic Review with Meta-Analysis of Baseline Values and Their Modification after Physical Therapy.

BACKGROUND: Myofascial trigger points (TrP) are diagnosed upon the presence of clinical signs among which hypersensitivity is considered one of the most important. The detection of the pressure pain threshold (PPT) is used to quantify the degree of hypersensitivity. However, there is a lack of normative data about how hypersensitive a TrP is. Therefore, the objective was to quantify the PPT for myofascial TrP in the upper trapezius muscle and its modification after manual or instrumental physical therapy interventions. METHODS: A systematic review and meta-analysis were conducted among three databases (MEDLINE, Cochrane Library, and PEDro). Two independent reviewers conducted the electronic search and assessed the methodological quality of the included studies. RESULTS: Eleven studies with a high-risk bias indicated that the PPT at TrP sites was 105.11 kPa lower (95% CI: -148.93; -61.28) at active TrP sites (Chi-squared = 1.07, df = 1 (p = 0.30), I2 = 7%) compared to the PPT of the upper trapezius muscles of healthy subjects. In addition, the PPT of TrP was also lower than the reference values coming from the pain-free population. Moreover, the PPT increased after both manual and instrumental treatment by 28.36 kPa (95% CI: 10.75; 45.96) and 75.49 kPa (95% CI: 18.02; 132.95), respectively. CONCLUSIONS: The results of the present study show that TrP has a decreased PPT when compared to healthy muscles and that physical therapy may increase the PPT. However, the clinical relevance of this decreased PPT needs to be further elucidated. Further, the high risk of bias in all the retrieved studies undermines the validity of the results.

Short-Term Morphological Changes in Asymptomatic Perimandibular Muscles after Dry Needling Assessed with Rehabilitative Ultrasound Imaging: A Proof-of-Concept Study.

Facial anatomical structures are not easily accessible to manual palpation. The aim of our study is to objectively assess temporomandibular joint and perimandibular muscles dimensions by means of sonographic measurements before and after dry needling (DN) in asymptomatic subjects. Seventeen subjects participated in this before-after study with a within-subject control. After random allocation, one side of the face was used for the intervention and the contralateral as control. DN was performed on the temporal, masseter, and sternocleidomastoid muscles. Each subject was examined bilaterally before, immediately after, and one month after the intervention through Rehabilitative Ultrasound Imaging (RUSI) of the temporomandibular articular disc and the three target muscles. Maximum mouth opening was measured at baseline and at one month. After a single DN session, articular disc thickness significantly decreased; muscles' thicknesses (except for temporal thickness) significantly decreased immediately and at follow-up on the treated side; no significant changes resulted for the control side. The maximum mouth opening increased from 4.77 mm to 4.86 mm. RUSI may be useful to assess the dimensions and thickness of the temporomandibular disc and muscles before and after an intervention. DN influences muscle morphology, and it has a positive influence on mouth opening in the short term.