The Disabled Throwing Shoulder- The “Dead Arm”

What Is The “Dead Arm”?

“Dead Arm” is a term used in the athletes in sports requiring precision throwing like baseball. The term “dead arm” is defined as any pathological shoulder condition in which the thrower is unable to throw with pre-injury velocity and control due to pain. Dead arm usually occurs during the acceleration phase. This is when the arm is moving forward and the athlete suddenly feels pain. The arm goes “dead” and is no longer able to throw the ball with his usual velocity.

What Are The Causes?

The “Dead Arm” phenomenon is characterized as a disorder with various causes. Some of the causes include psychological factors, calcification in the ball and socket joint, and bone spurs in the acromion. Impingement of the shoulder ligaments, rotator cuff problems, bicep tendonitis, micro-instability, internal impingement and SLAP lesion can also cause a “dead arm”.

What Happens In The “Dead Arm”?

In the painful shoulders of throwing athletes, because of the repetitive arm position being turned out backwards as far as possible (external rotation) to create potential energy in the wind up phase prior to the forward acceleration phase, it has been previously postulated that the pain is due to the shoulder capsule in the front being over stretched. This excessively stretched capsule then allows the shift of the “ball” of the shoulder forward, creating an impingement of the structures in the front of the shoulder joint, hence resulting in pain and the inability to throw.

However, this theory is now being challenged. Some researchers have found “dead arm” to be most commonly associated with Type 2 SLAP (Superior Labral tear from Anterior to Posterior) lesion. SLAP lesion is a tear in the top part of the labrum (which is like the meniscus of the knee). Type 2 SLAP lesion occurs because of tight capsule posterior capsule. This is the capsule at the back of the shoulder joint. This tight capsule forces the ball of the shoulder upwards and backwards into the shoulder joint. This results in a tear in the labrum. The outward sign of this capsular tightness is the loss of forward rotation (internal rotation) of the shoulder joint.

How Do I Know If I Have A “Dead Arm”?

Here is a test to assess the range of forwarding rotation. First, lie down and have your arm placed at 90 degrees relative to your trunk and with the elbow held at the same angle. Keeping the shoulder stable without allowing the shoulder blade to slide up, allow the forearm to drop forward as much possible. Ideally, you should get about 90’ forward movement.

Everyone is different. The best way to assess for loss of range is to compare it with the good arm and use that as a guide. A study found that those who had the loss of range and did stretching to the capsule had a 38% decrease in the incidence of shoulder problems. This is when compared to the non-stretched group. Researchers have defined an acceptable loss of forwarding rotation range as 20 degrees. This is equivalent to less than 10% of the total rotation seen in the non-throwing shoulder.

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Reference:

Burkhart S. S, Morgan CD and Kibler WB. The Disabled throwing shoulder: Spectrum of pathology Part 1: Pathoanatomy and biomechanics. The Journal of ARthoscopic and related Surgery, vol19, no4 (April),2003:pp404-420