#TOS (Thoracic Outlet Syndome) commonly afflicts world class overhand pitchers. My studies of these players has revealed the etiology and rational cure. It is a most interesting bio-dynamic. Discussed in my tweet of 4/06/2019.
Analysis right hand overhand pitch: initially upper body winds clockwise (as seen from above). Next, left upper extremity thrown inferior-posterior; giving momentum to sudden upper body CCW torquing rotation & to counterforce (stabilize) right upper extremity overhead catapult.
Net effect of these initial motions is dynamic exercise of the left S. trapezius, which stabilizes left shoulder as left upper extremity is vigorously thrown inferior; leading to hypertrophy of this muscle. Same time, right upper extremity functions as passive overhead catapult.
As right upper extremity rotates overhead, right S. Trapezius relatively disused & muscles of right shoulder inferior draw (e.g. Pectorals) are dynamically exercised via stabilizing right arm catapult; leading to strength dominance of right Pectorals over right S. trapezius.
NET MORPHOLOGIC EFFECTS: left Superior trapezius > right; lower right shoulder during neutral upright stance (seen grossly in exam room); greater girth (~ 2x) of anterior leading edge of left Superior trapezius; dominance of muscles of inferior draw of right shoulder.
The above described findings would explain why external rotation of throw arm is weakened; hyperdynamic strength of muscles that evoke internal rotation; in males who throw overhead; not expected in women (who throw underhand softball).
The above described findings would explain why external rotation of throw arm is weakened; hyperdynamic strength of muscles that evoke internal rotation; in males who throw overhead; not expected in women (who throw underhand softball).
Above described muscle strength asymmetries of opposing muscle also explanatory for the severe Thoracic Outlet Syndromes (TOS) often observed in major league pitchers’ throw-side shoulders, and which result in thrombosis within subclavian blood veins of throw arm side:
TOS results from relative closure of associated costal-clavicle dimension, the true Thoracic Outlet; caused by concurrent weak S. trapezius and hyperdynamic Pectoralis muscles. The P. minor attaches to corocoid process of scapula and tenderness is common at this insertion site.
Another common finding is a bruit at proximal sub-clavicle region during arm abduction & at a fixed & reproducible degree of abduction; usually found at > 90 degrees of abduction. Doppler/US with Addson’s Maneuvers also diagnostic. Ulnar paresthesias initiate at same elevation.
These are the reasons that two favored surgeries for TOS (performed by Thoracic Surgeons) are: resection of P. minor insertion on corocoid and axillary approach to drawing first rib down to second rib and fixing it there with wire; thereby widening costo-clavicle dimension.
The “Scalenus Anticus” theory of TOS is a red herring, and reason that operative attempts at correcting this “abnormality” were such dismal failures.
Strong catapult function of the throw arm & speed of the ball might be enhanced by relative ipsilateral Superior trapezius weakness. Certainly, the earnings of world-class baseball pitchers might override concern for TOS, and by time it develops a retirement nest egg is likely.
Those interested in the bio-dynamics of an overhand pitch as described above are advised to observe the forceful downward thrust of the contralateral extremity at onset of the pitch. This motion occurs in an instant, and if not looked for is commonly overlooked.
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