The goal of this observational study is to define the safe distance that will reduce the risk of pneumothorax through ultrasonographic imaging measurements in both sitting and prone positions to ensure patient safety during these procedures. The main question[s] it aims to answer [is/are]:

The mean distance between the skin and pleura in sitting position during the inhalation and exhalation The mean distance between the skin and pleura in prone position during the inhalation and exhalation

Myofascial pain syndrome is characterized by pain and tenderness at specific points known as trigger points. Tension and spasm occur in the muscles, making it one of the most common causes of musculoskeletal pain. Various treatment options, such as TENS, dry needling, and trigger point injections, are available for the management of myofascial pain syndrome. Trigger point injection is one of the evidence based treatment methods that can provide both temporary and long-term relief.

Trigger point injections can be performed under ultrasound guidance or by blind technique. Although trigger point injection is generally be considered a safe procedure when performed by a skilled practitioner, complications may occur. These complications include pain during and after the procedure, nerve injury, bleeding, infection, and serious complications such as pneumothorax. Pneumothorax may occur when trigger point injections are administered into the chest wall muscles, particularly the trapezius, rhomboid major, or rhomboid minor muscles. Among these muscles, the rhomboid major is very thin, and the thickness of the skin, subcutaneous fat layer, and other soft tissues surrounding it varies between individuals. Since nerves, vascular structures, and the pleura are present in the deeper parts of these muscles, determining the appropriate injection depth is crucial.

In clinical practice, trigger point injections are administered by clinicians in both prone and sitting positions. To the best of our knowledge there is no studies thatinvestigates the determination of a safe distance through measurements in both the sitting and prone positions. In this study we aim to calculate the safe distance using ultrasound that will reduce the risk of pneumothorax through ultrasonographic imaging measurements in both sitting and prone positions during inhalation and exhalation to ensure patient safety during these procedures.

Inclusion Criteria:

• patients diagnosed with Myofascial Pain Syndrome
• patients scheduled for trigger point injections due to Myofascial Pain Syndrome.

Exclusion Criteria:

• under 18 years of age,
• additional diseases other than Myofascial Pain Syndrome,
• the presence of active infection in the interscapular area where ultrasound imaging and measurements will be performed,
• lesions that disrupt skin integrity or affect subcutaneous and muscle structures such as anomalies or masses that could impair imaging quality
• individuals with known lung diseases
• not consent to participate in the study."

Patients scheduled to undergo trigger point injections due to myofascial pain