Thoracic Outlet Syndrome (TOS) in the overhead thrower is a rare and potentially career ending pathology. Due to the violent nature that pitching places on the surrounding soft tissue structures of the shoulder and neck, hypertrophy of the surrounding tissues can cause compressive forces on the neurovascular structures. Symptoms include pain, weakness, fatigue, numbness in the arm, and cold sensation in the fingertips. For the overhead thrower or pitcher, symptoms are most often pain accompanied with a loss of velocity and command.
There are no sure-fire diagnostic tools that are used to diagnose TOS. There is no test, radiography, or imaging that will alert medical staff to the possibility of TOS. Often times, the absence of other pathology with a “recognition of stereotypical clinical patterns” confirms TOS. Below is a picture of the structures that are involved.
Excessive overhead throwing leads to hypertrophy or tightening of the pec minor and the scalenes and loss of stability in the shoulder complex. This can lead to compression of the brachial plexus which manifests in pain and tenderness along the anterior scalenes. There are also other anatomical anomalies that can predispose athletes to TOS such as posture and position of the scapula.
Neurogenic TOS (nTOS) is compression of the brachial plexus while vascular TOS involves the subclavian artery and vein. The lack of blood flow can lead to fibrous changes in the vein or artery that increases the risk of thrombosis or clot formation.
For our purposes, while we will discuss blood flow later on, the focus is on treatment of nTOS. There are non-operative options to treat nTOS, however, surgery has shown to be more effective. Surgical procedures consist of resectioning the first rib, removal of the anterior and middle scalenes, and brachial plexus nerve decompression.
A number of pitchers have had TOS surgery to reduce the compression of the brachial plexus. Matt Harvey and Phil Hughes are two of the more recent pitchers. Thompson, et. al studied 13 MLB pitchers who underwent nTOS surgical procedures from 2001-2014. 10 of 13 made successful returns to MLB. The average age at the time of surgery was 30.2 and post-operative rehabilitation lasted ~10.8 months.
The researchers used a number of metrics to measure performance after their return to the mound. They used Pitch/Fx data at different time period scenarios prior to and after surgery: 4 weeks, 8 weeks, 12 weeks, 6 months, and 1 year. The 10 pitchers in the study had a mean age of 23.2 years at MLB debut and ~7 years of playing time before injury. The cohort continued to play an average of 2 years after surgery with 6 still active. Four retired due to other issues.
Measuring 72 pitching metrics using PitchF/x, researchers showed 75% of the metrics (54 of 72) were unchanged 8 weeks pre-op compared to 12 weeks post-op. These include ERA, WHIP, SO/BB, H/9, BB/9. 14 metrics saw significant improvement while only 4 metrics showed decline, including FIP and max velocity (Mean decreased 1 mph)
While nTOS decompression surgery has shown to be effective at the highest levels of baseball based on objective PitchF/x metrics, research remains limited, especially in comparison to the more common Tommy John Surgery. Due to the chronicity of the injury, the time for nerves to heal after decompression surgery, and the altered mechanics that come from throwing with pain before diagnosis, rehab is generally one year.
Concerning blood flow, Laudner, et. al researched the effect of blood flow in the throwing arm. They studied 51 professional pitchers and 34 position players. Blood flow was tested at rest (arm by side) and in a “provocative shoulder position”, basically the late cocking phase before acceleration.
Researchers determined that with the arm at rest there was no difference in blood flow volume between throwing and non-throwing arm. However, both pitchers and position players showed a significant decrease in blood flow volume when in the throwing position with pitchers displaying a more significant decrease than position players.
Researchers have shown that when the arm is in the late cocking phase of throwing, the humeral head compresses on the axillary (armpit) artery 83% of the time. There is also evidence that tightness in the pec minor can cause compression of the axillary artery in the late cocking phase. What does this mean? As of now, research is limited. However, the authors noted that the 85 players tested were asymptomatic and pain-free. So what does diminished blood flow volume mean in a symptomatic arm? More research is needed to truly determine any adverse effects of this phenomenon.
When it comes to prevention, stretching the scalenes and pec minor is key. Building strength through the scapular stabilizers and rotator cuff will help build strength and correct altered biomechanics. Posture is extremely important. Rounded shoulders and a forward head posture will lead to increase hypertrophy of the scalenes and pec minor. Ryan Hill at Top Velocity shares some effective videos detailing exercises and stretches to help with prevention. These are basic exercises I use in the clinic to treat other shoulder pathologies, postural re-education, and cervical pain as well.
In closing, what we do know is that decompression surgery and first rib resection has shown to provide positive benefits and similar performance after 1 year of rehab. 68 of 72 PitchF/x metrics have objectively testified to similar if not improved performance on the mound.