Evaluation of Middle Scalene Muscle Dynamics During Inspiration in Patients with Traumatic Thoracic Outlet Syndrome Presenting Upper Limb Symptoms

Shintaro Uekawa, Hisato Okanishi, Tetsuhiro Kato
Purpose:

The purpose of this study is to observe the dynamics of the brachial plexus and middle scalene muscle during inspiration using ultrasound imaging (US), and to compare the findings between healthy adults, the non-symptom side, and the symptom side in patients with T-TOS.The purpose of this study is to observe the dynamics of the brachial plexus and middle scalene muscle during inspiration using ultrasound imaging (US), and to compare the findings between healthy adults, the non-symptom side, and the symptom side in patients with T-TOS.

Methods:

This study included 11 patients with T-TOS (6 females, 5 males) who had unilateral upper limb symptoms. A control group consisted of 20 healthy adults (10 males, 10 females). T-TOS diagnosis was confirmed using the Morley test and Roos test. Inspiration was performed using a protocol of 600 ml/sec with an inspiratory trainer. US was used to image the middle scalene muscle in the short axis, adjusting the view to capture the posterior tubercle of C7 and the C5 nerve root. Preliminary experiments on several healthy individuals revealed an increase in the vertical distance between the C5 nerve root and the surface of the middle scalene muscle during inspiration, compared to rest. Based on this finding, the vertical distance at rest between the C5 nerve root and the surface of the middle scalene muscle was defined as distance A, and the vertical distance during inspiration as distance B. The ratio of distance B to distance A was calculated and compared among the symptom side, the non-symptom side, and healthy adults. For the control group, measurements were taken on the right side of the neck.

Results:

There was a significant difference between the symptom side (1.3 ± 0.4) and the non- symptom side (2.0 ± 0.4), as well as between the symptom side and healthy adults (2.2 ± 0.9) (P 0.05)

Conclusion(s):

The increase in the vertical distance between the C5 nerve root and the surface of the middle scalene muscle during inspiration was significantly smaller on the symptom side compared to the non- symptom side and healthy adults.

Implications:

The observation of middle scalene muscle and C5 nerve root dynamics during inspiration using ultrasound may offer an objective method for assessing the pathology of traumatic thoracic outlet syndrome (T-TOS).

Funding acknowledgements:
No funding was received for this study
Keywords:
WAD
inspiration
scalene muscle
Primary topic:
Musculoskeletal: spine
Second topic:
Musculoskeletal: upper limb
Third topic:
Musculoskeletal
Did this work require ethics approval?:
Yes
Name the institution and ethics committee that approved your work:
Institution: Hirabari Kato Orthopaedics Ethics committee: Hirabari Kato Orthopaedics Ethics Committee
Provide the ethics approval number:
Ethics number: 202402
Has any of this material been/due to be published or presented at another national or international conference prior to the World Physiotherapy Congress 2025?:
No

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