gms | German Medical Science

14th Triennial Congress of the International Federation of Societies for Surgery of the Hand (IFSSH), 11th Triennial Congress of the International Federation of Societies for Hand Therapy (IFSHT)

17.06. - 21.06.2019, Berlin

Thoracic outlet and interscalene triangle variations – anatomic research

Meeting Abstract

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  • presenting/speaker Luciano Poitevin - Buenos Aires University Hospital, Buenos Aires, Argentina

International Federation of Societies for Surgery of the Hand. International Federation of Societies for Hand Therapy. 14th Triennial Congress of the International Federation of Societies for Surgery of the Hand (IFSSH), 11th Triennial Congress of the International Federation of Societies for Hand Therapy (IFSHT), 11th Triennial Congress of the International Federation of Societies for Hand Therapy (IFSHT). Berlin, 17.-21.06.2019. Düsseldorf: German Medical Science GMS Publishing House; 2020. DocIFSSH19-1582

doi: 10.3205/19ifssh0473, urn:nbn:de:0183-19ifssh04732

Published: February 6, 2020

© 2020 Poitevin.
This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License. See license information at http://creativecommons.org/licenses/by/4.0/.


Outline

Text

Objectives/Interrogation: Thoracic Outlet Syndrome (TOS) remains controversial. Pathologic fibrous bands as well as a Scalene Minimus muscle have been advocated as causes. However, many authors deny its existence in the absence of a cervical rib.

Are there anatomic variations at the interscalene triangle (IST) thay may explain this entity? Fibrous bands may be normal variations? How often can these possible variations produce symptoms?

Methods: 50 Supraclavicular unembalmbed regions were dissected. Number, origin & insertion of scalene muscles were recorded. Interscalene (IS) distance on the 1st rib was measured and correlated with subclavian artery height over the rib. Insertion, tendon shape & relationship with the trunks of the brachial plexus were registered. Narrow passageways between scalene muscles were defined. Potential compression and/or impingement sites were described.

Results and Conclusions: The scalene muscles originate as a single mass (SM) extending from the cervical spine to the 1st rib and the suprapleural membrane. This SM becomes fragmented by the growth and distal migration of the hand & upper limb bud. The subclavian vein passes in front of this mass, while the subclavian artery & brachial plexus pass through it. The remnant muscle in front of the neurovascular bundle (NVB) become the Anterior Scalene (AS); and that behind the NVB become Middle (MS) and Posterior Scalene.

Muscle remnants of the intermediate part of the SM were indentified as: a) The Superior Intermediate Scalene (SIS) = 18%, extending from the C-VI vertebra to join the AS; b) The Inferior Intermediate Scalene (IIS = Scalene Minimus) = 50%, running from C-VII to the 1st rib & suprapleural membrane.

This arrangement divides the IST into several passageways, reducing its size and potentially compressing the NVB.

In 6%, the IS distance at the level of the 1st rib is 0. (Mean = 9,76mm, range 0-18,2mm) This arrangement lifts the artery and the lower trunk. Also, the MS tendon often displays a concave sharp edge which impinges on the lower trunk.

The IIS is sometimes replaced by a transverse-septo-costal ligament which is not a pathologic fibrous band.

As these are normal anatomic variations; therefore we feel that number, size and shape of the scalene muscles should be associated with extreme sustained positions of the upper limb (e.g. Hyperelevation or shoulder girdle descent) in order to produce NVB symptomatic compressions. We present surgical examples of these symptomatic variations mimicking cubital tunnel or carpal tunnel syndromes.