Medical Report: Joba Chamberlain's Throwing Motion a Key Factor

Even if Tommy John surgery repairs Joba Chamberlain's elbow, a change in mechanics may be in order.

The legend of Joba Chamberlain took another unexpected twist yesterday when the former New York Yankees' phenom was diagnosed with a torn ligament, requiring Tommy John surgery to repair the damage. Chamberlain now faces 12-16 months of rehabilitation, which puts his career as a Yankee in jeopardy. But could his fate, or that of other pitchers who have required surgical repair of the elbow, have been prevented by making a slight adjustment to his pitching motion?

Experts on pitching mechanics will tell you when it comes to injury risk, timing is everything. Although it is impossible to predict which pitchers will ultimately end up with severe elbow or shoulder damage based on their throwing styles alone, it seems those who have glitches in the sequence of specific components of their pitching motions are more susceptible to injuries.

Two mechanical flaws in particular seem to raise the likelihood of serious shoulder and elbow injuries: these have been described as the "inverted W" and the "inverted L." In either case, it is the accumulation of years of stress on these joints that causes the disabling injury rather than a single event itself.


The inverted W is the dreaded flaw that many consider a key reason pitchers such as Mark Prior, John Smoltz, and Stephen Strasburg have suffered serious arm injuries, including Tommy John surgeries for Smoltz and Strasburg.  
This occurs when, upon removing his pitching hand from the glove, the pitcher places the elbow above and behind the shoulder, well above the ball.

Upon completing the pitching motion, two potentially dangerous movements occur with the inverted W. First, the humerus bone (upper arm bone) twists sharply as it rises above the shoulder, placing stress on the ligaments of the shoulder and the rim of tissue inside the shoulder socket (labrum). Second, the positioning of the arm - as insignificant as it may seem - alters the timing of the pitching sequence. Whereas pitchers with a classic delivery bring the forearm and elbow forward at the same time as the trunk of the body rotates toward the mound, pitchers with an inverted W motion allow their forearm and elbow to lag behind the rotation of the trunk. This puts increased torque and stress on the elbow, and the brunt of the excess force is placed on the ulnar collateral ligament (UCL).


Chamberlain's pitching motion could be considered an inverted L, which also causes increased stress and potential for damage to the shoulder and elbow. The inverted L describes the situation in which the pitcher, upon removing the pitching hand from the glove, brings his arm back into a position where the upper arm and forearm are at a 90 degree angle, with the elbow at the level of the shoulder and the forearm pointing toward the ground.

The concern with an inverted L motion is that the elbow is as far as possible from the shoulder, starting a cascade of potentially harmful events. In order to generate velocity, the shoulder of the throwing arm must rotate forward ahead of the elbow. Then, as the elbow comes forward, it must rotate sharply and externally to sling the forearm forward. Again, it's an issue of excess stress on the shoulder and elbow, and again, it's an issue of timing.

Rivera_motion_medium For comparison, look at the elbow and forearm positioning of Yankees closer Mariano Rivera. As Rivera prepares to send the ball forward, his pitching elbow is never above the level of his shoulders, and as opposed to the inverted L his forearm points skyward. This allows his arm and torso to move toward the plate in concert, eliminating unnecessary torque on the elbow.

It is worth mentioning that Chamberlain was shelved in 2008 due to a shoulder injury, which, in retrospect, may have been exacerbated due to his throwing motion. Given the caution with which the Yankees took in limiting Chamberlain's innings early in his careers, it appears not even the "Joba Rules" were able to compensate for a faulty pitching motion.

Some believe Tommy John surgery, in which the UCL is replaced with a tendon from elsewhere in the body, ultimately provides the pitcher with greater strength and stability than prior to the injury itself. However, although the list of pitchers who have undergone the procedure and returned successfully to the mound continues to grow, there is an increasingly popular school of thought that long-term recovery depends largely on the pitcher's ability to adjust the faulty mechanics that may have contributed to the injury in the first place. For this reason, there is justifiable reason for concern that unless pitchers like Chamberlain and Strasburg work to modify their throwing motion during rehabilitation, over time the repaired elbow ligament may be just as likely to suffer a similar fate as before.

Either way, another chapter yet to be written in the Legend of Joba.

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