This pilot study established a minimally invasive biopsy technique to obtain high-quality MTrP tissue samples to evaluate mitochondrial function via high-resolution respirometry.

Myofascial trigger points (MTrPs) are hyperirritable areas in the fascia of the affected muscle, possibly related to mitochondrial impairment. They can result in pain and hypoxic areas within the muscle. This pilot study established a minimally invasive biopsy technique to obtain high-quality MTrP tissue samples to evaluate mitochondrial function via high-resolution respirometry. Secondary objectives included the safety of the biopsy procedure assessed via clinical wound healing (number of patients with signs for local infection and inflammation). For this purpose, twenty healthy males participated in this study, 10 with a diagnosis of myofascial pain in the musculus (m.) trapezius MTrP (TTP group) and 10 with a diagnosis of myofascial pain in the m. gluteus medius (GTP group). The affected muscle was biopsied followed by a biopsy from the vastus lateralis to be used as a control. Measurements of oxygen consumption were carried out using high-resolution respirometry.

Inclusion Criteria:

• Male patients aged 18-45 years
• Clinical diagnosis of myofascial pain syndrome within the region of the shoulder-neck muscles or the lumbogluteal region and the presence of an MTrP, defined as a firm palpation of a hard, tender nodule resulting in a spontaneous pain complaint
• with symptoms present for 1 to 12 months

Exclusion Criteria:

• Signs that the participant's prescriptive compliance was not expected (e.g., lack of cooperation)
• Disorders of the respiratory tract
• Neurological disorders, in particular neurodegenerative and neuromuscular diseases
• Disorders of the cardiovascular system or the musculoskeletal system
• Civil servants and military service personnel.

Assessor doing high Resolution respirometry was blinded with respect to diagnosis, location of biopsy and all Patient related data