The Human Disharmony Loop: Demystifying Thoracic Outlet Syndrome

BackgroundThoracic outlet syndrome (TOS) remains controversial, with contentious diagnostic criteria and morbid surgeries of questionable efficacy. Although considered neurovascular compression, many mysteries abound, including presence of neck and upper back pain, occipital headaches, scapular protraction, and higher prevalence in women. Previously, we described the Human Disharmony Loop (HDL), where the asymmetric lower trunk innervation to the pectoralis minor (PM) protracts the scapula and deforms its connections. The pathoanatomy includes narrowing the thoracic outlet and subacromial spaces, stretching the upper trapezius and rhomboids, and irritating the occipital nerves, generating occipital headaches, upper back and neck pain, shoulder weakness, and radiating neuropathy. We hypothesize that TOS is a scapular phenomenon produced after PM tightness, and hence these patients will benefit from PM tenotomy with infraclavicular plexus neurolysis (PM+ICN) alone. MethodsTOS patients with 6-month minimum follow-up who met HDL diagnostic criteria were treated with PM+ICN. Outcomes included pain, shoulder abduction range of motion, headaches, scapular dyskinesis, secondary neurolysis. ResultsN = 144 patients were included. Median age was 50; 76% were female. Following PM+ICN, median pain decreased from 8.0/10 to 2.0/10, median shoulder abduction increased from 90 to 180 degrees, occipital headaches decreased from 83% to 1%. Scapular dyskinesis normalized from 99% protraction at rest to 94% no protraction (all p<0.05). 16% required secondary neurolysis with only 1% at the thoracic outlet. Median follow-up was 15 months. ConclusionsIn a large series, isolated PM+ICN normalized scapular mechanics and substantially reduced pain and improved function. These findings suggest that TOS may be an anatomic subset of the HDL: the PM is the true anatomic culprit. The HDL anatomically answers the mysteries of TOS including headaches, neck pain, scapular protraction, and higher prevalence in women. These historically challenging patients may benefit substantially from an effective and low morbid alternative, PM+ICN. Level of EvidenceIV, therapeutic.