Objective measurement of tissue tension in myofascial trigger point areas before and during the administration of anesthesia with complete blocking of neuromuscular transmission.

Objectives: Myofascial trigger points (MTPs) are extremely frequent in the human musculoskeletal system. Despite this, little is known about their etiology. Increased muscular tension in the trigger point area could be a major factor for the development of MTPs. To investigate the impact of muscular tension in the taut band with an MTP and thereby, the spinal excitability of associated segmental neurons, we objectively measured the tissue tension in MTPs before and during the administration of anesthesia using a transducer.

Methods: Three target muscles (m. temporalis, upper part of m. trapezius, and m. extensor carpi radialis longus) with an MTP and 1 control muscle without an MTP were examined in 62 patients scheduled for an operation.

Results: We found significant 2-way interactions (ANOVA, P<0.05) between the analyzed regions of the target muscles dependent on the time of measurement, that is, before and during a complete blocking of neuromuscular transmission. These effects could be demonstrated for each target muscle separately.

Discussion: An increased muscle tension in MTPs, and not a primary local inflammation with enhanced viscoelasticity, was the main result of our investigation. We interpret this increased muscular tension in the taut band with an MTP as increased spinal segmental excitability. In line with this, we assume a predominant, but not unique, impact of increased spinal excitability resulting in an augmented tension of segmental-associated muscle fibers for the etiology of MTP. Consequently, postisometric relaxation might be a promising therapeutic option for MTPs.