Human Disharmony Loop: The Role of the Pectoralis Minor in Thoracic Outlet Syndrome

The current understanding of thoracic outlet syndrome (TOS) as neurovascular compression fails to address multiple questions. This includes neck and upper back pain, occipital headaches, scapular protraction, higher prevalence in women, and overall inefficacy of current surgeries. The pectoralis minor (PM) uniquely carries lower trunk innervation and can persistently protract the scapula. Protraction narrows the thoracic outlet and subacromial spaces, stretches the upper trapezius and rhomboids, and irritates the occipital nerves, producing occipital headaches, upper back and neck pain, shoulder weakness, and hand numbness/tingling. We hypothesized that select TOS patients can benefit from PM tenotomy with infraclavicular plexus neurolysis (PM+ICN) alone.

Patients with TOS presenting with coracoid tenderness and scapula protraction on examination were treated with PM+ICN. Outcomes included pain, shoulder abduction range of motion, headaches, scapular dyskinesis, and need for secondary neurolysis.

A total of 144 patients were included. The median age of patients was 50 years; 110 (76%) were women. Following PM+ICN, median pain (out of 10) decreased from 8.0 to 2.0, median shoulder abduction increased from 90 to 180 degrees, occipital headaches decreased from 120 (83%) to 2 (1%) (all P < 0.001). About 16% of patients required secondary neurolysis with only 1% at the thoracic outlet. Median follow-up was 15 months.

In a large series of select patients with TOS, PM+ICN (with infrequent secondary neurolysis) significantly reduced pain and headaches while restoring motion. These findings suggest the PM may play a significant if not central role in TOS management, apart from neurovascular compression, by pathologizing the scapula's connections.