Author:  
Kristin Haraldsdottir
Published:  
September 30, 2022

How the Pact Sense was used to track the efficacy of laser therapy in resolving asymmetry in the left and right upper trapezius leading to neck pain

Neck pain is very common, with 30% of adults in the US will experience neck pain in any given year. It can be caused by many different things, including weak and overused neck muscles, wear and tear on the cervical spine, whiplash, and more. Any shift in the spine such as poor posture or muscle imbalance can significantly affect the surrounding muscle, and often the trapezius muscle is affected. The upper trapezius is a complex muscle in that the muscle crosses over a dozen joints. Shortening of any one of the joints will involuntarily contract the upper trapezius and can produce knots and pain. 

Case study- Mary and significant neck pain

We used the Pact Sense to measure asymmetry in the left and right upper trapezius in a physical therapy patient, Mary, who had been experiencing significant neck pain for several years. Mary is in her 70s and often feels more pain on her right side compared to the left, and has experienced paresthesia (tingling and numbing) in her fingertips, as her pain radiates down her arm from her neck.

Mary’s physical therapist has used the Pact Sense to monitor the effects of laser therapy on a client. The physical therapist uses a Class 4 laser that has been shown to be beneficial in musculoskeletal dysfunctions through pain control and tissue repair. The class 4 laser emits 500 mW and promotes blood flow, reduces swelling, and stimulates the production of ATP. As a result, patients experience reduced pain and inflammation, as well as increased range of motion. 

Treatment plan

Mary’s physical therapist has been performing laser therapy on Mary’s upper trapezius muscles to help with the pain and swelling associated with her neck pain. Interestingly, Mary does not report immediate relief following the laser therapy sessions, but has reported incremental consistent subjective improvement. In fact, it has been so effective that was able to stop taking Gabapentin for the pain, which she had been taking for the past 5 years. 

How can the Pact Sense be used in this case?

It is common for patients to report no significant change in their symptoms following a physical therapy session. In this case, Mary’s case of neck pain is so severe that any resolution in symptoms will be important. There are few objective measurements that can be taken to assess muscle and soft tissue properties, leaving practitioners with mostly subjective measures of a patient’s baseline, and subsequent improvement or change during a treatment. We tested the Pact Sense to determine the muscle property symmetry in Mary’s left and right upper trapezius muscles at baseline. Her physical therapist scanned her upper left and right trapezius muscles immediately preceding and following the 20 minute laser treatment. 

What are the muscle properties measured by the Pact Sense?

Pact Sense delivers pulses to the soft tissue and extracts parameters from the depth, stiffness and damping, as measured by the end effector of the Pulse. Parameters of muscle mechanical properties are then calculated, and Stiffness, Damping and Damping slope are represented in this case report. 

  • Stiffness: the degree to which the tissue resists the pulse of the end-effector, representing the tightness of the muscle. 
  • Damping: the response of the tissue at each depth, and represents the underlying tissue’s response to deformity. 
  • Damping slope: How the damping of the tissue changes with increasing depth
What were Mary’s scan results?

In Mary’s pre-treatment scans of the left and right trapezius muscles, there were significant asymmetries in Stiffness (45%), Damping slope (25%) and Damping (52%). In post-treatment scans on the same sites, asymmetries had resolved in both Stiffness and Damping slope, and decreased in Damping to 16%. (Asymmetries less than 10% are considered to be within the range of error, and are thus not considered to be clinically relevant.)

What does her data mean? 

Neck pain often arises from prolonged high tone in a muscle that results in the nervous system sending pain signals to the area. The pain response results in localized inflammation, which can lead to muscle weakness, trigger points and referred pain to other areas of the body. The Pact Sense data found that the left trapezius had significantly higher stiffness, damping and damping slope than the right side before the laser treatment was performed. Following treatment, whereas stiffness and damping slope asymmetries had resolved, damping was higher on the right side than the left, though to a very small degree. A potential mechanism to explain this could be that the laser therapy reduced tone in the left upper trapezius, which had high tone before treatment, and introduced slightly more tone in the right side, through increased blood flow and increased production of ATP.