Originally Posted by sawxray

I work with a number of physicians who treat patients with TOS, including several surgeons. I have observed Dr. Sanders evaluating patients for pec minor release, and have observed him perform one of these procedures, as well.

Although it is not known with certainty why a pec minor release would work in a patient with TOS, there are several theories:

1. The neurovascular bundle (nerves, artery, in vain) pass between the pectoralis minor muscle and the chest wall (the retropectoralis space). Theoretically, release of this muscle would widen this tunnel, and if compression is occurring here, would relieve the compression. However, most experts agree the impression that this site is somewhat unusual, and MRI studies have actually shown that this tunnel is wider in patients with TOS than in normal people.

2. A lot of the neck, chest, and shoulder pain associated with TOS is due to muscle imbalance and strain, and releasing this muscle can resolve some of those issues.

3. The above mentioned muscle imbalance can shift the position of the shoulder girdle, which is attached to the chest wall only through the clavicle (collarbone). Release of the pectoralis minor, which acts to pull the shoulder girdle forward and downwards, would allow the posterior muscles to shift the entire shoulder girdle backwards. Due to the complex shape and motion of the clavicle, this could serve to open up the costoclavicular interval (the space between the clavicle and the first rib). It is very unlikely that the position of the ribs would be altered.

At this time, it is unclear which patients would benefit from the pec minor release, and which ones require scalenectomies or resections of the first rib. However, the pec minor release is a minor procedure, and is certainly less invasive than the first rib resection and scalenectomy procedure used in most patients.

Regarding the nerve block, I have seen people perform it in different ways. Some people inject around the attachment of the pectoralis minor, which may anesthetize the nerves of the brachial plexus as they pass through this region. Other people inject directly into the muscle, which would tend to make the muscle relax and/or feel less pain internally.

I hope this additional information is somewhat helpful.