What causes Tommy John surgery? Why did a certain pitcher get hurt–and another did not? The answers are often extremely complicated–and, frankly, we are only just beginning to understand all the mechanisms of injury in pitchers.
Arm-related injuries in baseball have three major factors: arm fitness, mechanical efficiency, and anatomical factors (this leaves out trauma-related issues–Mark Prior taking a liner off the elbow, Prior’s collision with Marcus Giles, etc).
Using oft-injured flamethrower Joel Zumaya as the lens, let’s dig a little deeper at what caused his shoulder and elbow injuries. Today, we’ll look into the elbow, since Zumaya’s latest injury was to his UCL, though he’s had a litany of elbow problems in the past – including the rare fracture of the olecranon process. Grab your copy of Gray’s Anatomy (not the terrible TV drama) and let’s go!
The Set-Up: Joel Zumaya’s Background
Joel Zumaya suffered a torn ulnar collateral ligament (UCL) while throwing in the bullpen during Spring Training for the Minnesota Twins in 2012. Zumaya has been one of the most electric relievers to watch, since he was the natural follow-up to Eric Gagne – blistering fastball with a knee-buckling out pitch. Gagne had his “vulcan change,” Zumaya had his knuckle-curve. Zumaya would constantly throw 100+ MPH fastballs 2 feet away from the zone – missing to his arm-side for the most part – which probably didn’t make righties feel all that comfortable.
Zumaya has suffered a long list of injuries, as everyone knows. While some of them were freak accidents (separated shoulder from heavy boxes falling on it, strained flexor tendon from playing too much Guitar Hero), he’s definitely suffered his fair share while throwing baseballs. The injury database shows six major injuries through 2010.
But what caused his elbow and shoulder injuries?
Three Major Factors in Arm-Related Injuries
Fitness can be described with a variety of words – strength, endurance, conditioning, etc – but we’re using it in such a term that covers all of those concepts. When we say a pitcher has poor arm-related “fitness,” it generally means he has insufficient strength in the muscles of the arm, poor endurance, poor soft tissue quality, or other issues that crop up with baseball pitchers.
This isn’t something that can be readily evaluated, of course – without the full list of what a pitcher eats, does in the weight room, does outside for his long toss/throwing program, and how much he pays attention to rehab/prehab, we can basically only guess at his level of fitness.
Zumaya has had a lot of minor elbow-related issues that have kept him out of games here and there, which indicates he might have poor forearm strength. Strengthening the muscles in the forearm that attach to the elbow can help reduce the load the anterior band of the UCL takes on. I wrote a lot about this with regards to Stephen Strasburg – in Dr. Werner’s paper Biomechanics of the elbow during pitching, she wrote:
Triceps, wrist flexorpronator, and anconeus activity during peak valgus stress suggests that these muscles may act as dynamic stabilizers to assist the ulnar collateral ligament in preventing valgus extension overload.
The “wrist flexorpronator” (flexor/pronator) muscle group pronates the forearm, flexes the hand, and flexes the digits of the hand. They have a common tendon, which is called the common flexor tendon. Partial thickness tears to the common flexor tendon (generally just called the flexor tendon) are common (Strasburg’s original diagnosis was a torn flexor tendon and not a ruptured UCL).
Anterior/medial muscles of the forearm help to pronate the arm after ball release and slow down the arm. They also stabilize the elbow, as they attach to the medial epicondyle (through the flexor tendon).
All of the flexor/pronator muscles are held in place by the flexor retinaculum, the deep muscle fascia of the forearm. Soft tissue therapy of the fascia using baseballs, foam rollers, or The Stick can help with mobility and blood flow to the area, which is a vital component of any throwing program for pitchers.
Increasing the contractile strength of the flexor/pronator muscles through specific weight lifting can definitely increase power, brute strength, and endurance of the forearm muscles. Great exercises to do this would include one-arm rows, pull-ups, deadlifts, grip strength exercises, heavy ball throwing (2+ lb iron balls thrown with emphasis on pronation), and specific wrist weight/DB exercises.
In our experience with college and pro athletes, this type of training is not emphasized enough. It’s not enough to simply get a lot of throwing in; you have to work the muscles responsible for stability in the elbow (and shoulder) directly while maintaining good soft tissue through assisted and self myofascial release (SMR).
Zumaya also suffered an olecranon fracture of the elbow, and while news reports don’t specify in which location of the olecranon was fractured (generally divided up into thirds), the generally accepted mechanism of olecranon fractures tends to be when the bones in the forearm – specifically the ulna – collide with the medial wall of the olecranon’s fossa. (Analysis of the pitching arm of the professional baseball pitcher [1969 King, Brelsford, Tullos], Stress injury of the proximal ulna in professional baseball player [2002 Schickendantz et al]) The triceps can also pull a piece of bone away if the bone is weakened; this is called an avulsion fracture. However, this is incredibly rare in baseball pitchers and would only happen to youth athletes who develop very quickly or to hard-throwing pitchers who come back too soon from rehab where their muscles can pull hard on a weakened bone structure. (Spiral fractures of the humerus would fall into the same category.)
Common wisdom says that avoiding these types of fractures isn’t possible. As with a lot of conventional thinking in baseball training, we strongly disagree at Driveline Baseball. Athletes in our MaxVelo Program do partial throws with very heavy implements – up to 3 pounds – to stimulate osteoblasts in the elbow to build bone strength.
This is the most glamorous of them all, and to be fair, it’s likely to be the most relevant when it comes to injuries. Force application technique (better known as pitching mechanics) is largely responsible for how forces are distributed on the body. However, it’s important to note that even with a three-dimensional reconstruction of a pitcher’s mechanics, there are two primary confounding factors that don’t give you all the answers. They are:
- Replication of Forces: When you get kinetics (joint loads, forces, torques) and kinematics (angles, velocities, accelerations) of a baseball pitcher in a lab when he’s wearing sneakers and has a bunch of sticky reflective globes on his body, these are not necessarily the same kinetics and kinematics you’d get in a real game situation. Example: Pitchers in an artificial setting may be throwing 10-20% slower than they would in a game when they are fully adrenalized and wearing their actual game clothing. What are you really learning in a lab setting? (This is why our mobile biomechanical collection techniques can be very useful – we can collect in-game kinetic/kinematic data.)
- Equivalent Joint Loads Aren’t Equal: Let’s say you have two pitchers who have identical peak shoulder internal rotation torques. What can you determine from this? Well, not a whole lot – you can’t say that the infraspinatus is receiving 10 Newton-meters of force, because that type of specificity is not yet available (and probably will never be). A lot of factors go into this – lateral trunk tilt, shoulder abduction, the timing of the peak force, actual weight of the humerus, etc.
With all the boring stuff out of the way, let’s get into the animated GIFs that everyone loves. Here’s Joel Zumaya throwing a blistering 100 MPH fastball:
There are pauses at approximate locations of Stride Foot Contact (SFC) and Ball Release (BR).
So, what do we want to talk about from a pitching mechanics perspective? Let’s quickly discuss how Zumaya has such elite release velocities:
- Violent Trunk Rotation: As I discussed in my Hardball Times article about the fastest throwers in MLB, the myth perpetuated by pitching coaches that “finishing in a solid fielding position” is a good thing is… well, stupid. Zumaya and almost all other flamethrowers finish with their pitching arm shoulder rotated to the target due to the after-effects of violent trunk rotation.
- Great Bracing Action: Zumaya braces with the lead leg extremely well, which allows him to rotate against the front side and have very fast trunk forward flexion. This is also an effect of the outstanding sequencing he has with the lower half.
- Tight Front Side: His glove starts out in front and Zumaya rotates against it and into it, which is a prerequisite for efficient force transfer from the lower half to the top.
But, of course, we’re not here to talk about how he throws hard – we’re here to talk about whether or not his pitching mechanics contributed to injury. Zumaya has a classic case of a very horizontally abducted arm with a lot of shoulder abduction at SFC. In other words, this is the classic case of the Inverted W.
The Inverted W basically describes the mechanical flaw of a pitcher having two factors in combination:
- Elevated upper arm in the frontal plane (shoulder abduction)
- Internally rotated shoulder
These factors, combined with fast rates of pelvic and trunk rotation angular velocities, will cause the pitching forearm to lay back at a much faster rate than someone who does not have these kinematic markers. Some people think that this kinematic sequence helps to engage the Stretch-Shortening Cycle (SSC) in the body, which is a phenomenon not wholly understood in exercise science, but can be best described by an eccentric movement of a muscle immediately followed by a concentric movement of the same muscle.
There are a few problems with this SSC theory, the major one being that there is no research that correlates higher angular velocities of forearm layback with ball velocity! The factors that correlate with ball velocity according to peer-reviewed research are pelvic/trunk angular velocities, elbow extension velocities, knee stabilization/extension, and increased shoulder external rotation. The last part is what the SSC theorists think help to produce high ball velocities, but there’s really no research out there that supports that higher inertial masses of the forearm produced through kinematic sequences like the Inverted W can safely produce higher rates of MER.
This is a major contention between the Marshall and traditionalist camps that flys under the radar – Dr. Marshall’s pitchers can produce near-elite ranges of MER with 30-35% of rMER (speed of forearm layback). Dr. Marshall’s pitchers also produce equivalent peak internal rotation angular velocities AND elbow extension velocities (and torques for both of these kinematic parameters), which means they should throw almost as hard as traditional pitchers. However, they don’t – and our theory is a broken kinetic chain concept due to forced pronation of the forearm causing peak internal rotation angular velocities to occur too early in the delivery and the pronator teres applying a braking force before ball release.
When pitchers have a “late” forearm at SFC, their forearm lays back at a rapid pace, putting major stress on the anterior band of the UCL and the muscles in the forearm. Additionally, the structures in the posterior shoulder move at a much more rapid pace as the scapula tilts backwards to accommodate the massive amount of humeral external rotation.
As the humerus internally rotates and the elbow extends, the arm is accelerated to its peak angular velocities. An early active pronation force here will apply braking pressure to the arm and cause reduced ball velocities despite internal rotation and elbow extension angular velocities that can match much harder throwers. However, a lack of pronation at the right time will not allow the muscles of the forearm to contract at the correct time and will cause the anterior band of the UCL to experience a lot of load. And remember, these kinematic sequences happen in just a few milliseconds, making measurable changes nearly impossible without high-speed video!
While we discussed anatomy at length in the Fitness Factor portion of this article, there are congenital issues in baseball pitchers that can put them at higher (or lower) risk for elbow injury. The most curious case of this is the fact that RA Dickey does not have an Ulnar Collateral Ligament (UCL) yet was able to throw 89-90 MPH in college, which should basically be impossible!
However, there are other, more subtle anatomical varieties in humans that can cause a predisposition to elbow injuries in pitchers. A pitcher could have a hypermobile elbow joint (better known as double-jointed syndrome), causing a lot of laxity around the elbow. Unlike laxity in the shoulders that could be congenital (a sulcus sign or high Beighton score can help diagnose this) being a good thing for increased forearm layback, laxity in the elbow is a very bad thing! Pitchers want a very stable elbow, as the UCL’s entire function is to keep the elbow together as it is literally pulled apart by valgus stress in the pitching delivery.
Pitchers who throw more as a youth athlete will develop humeral retroversion – a twist in the upper arm – due to osseous adaptations. This is literally a deformation of the humerus caused by throwing stuff as a kid! It’s not necessarily a bad thing, however – many researchers and exercise scientists think it’s a necessary adaptation in baseball pitchers that allows for greater laxity in the shoulder joint. For those who didn’t throw much as a kid, not only will they have immature throwing patterns that make it look like they’re “pushing” the ball to the target, they may have anatomical issues that will not allow them to throw 90+ MPH without pain or injuries.
Pitchers overwhelmingly have Type I (flat) acromions, which allow for a lot of room in the shoulders. Most athletes with Type II (curved) and Type III (hooked) acromions simply don’t go on to pitch professional baseball because they are at risk for major soft tissue injuries (commonly known as “impingement,” a word I don’t like to use much for various reasons).
Zumaya doesn’t necessarily have any anatomical issues that contributed to his injuries, but it’s still an important factor that has to be pointed out.
Evaluating pitching arm-related injuries isn’t as simple as saying “That guy has an Inverted W, he is going to have Tommy John!” Demonstrating a risk factor (whether it’s lack of arm fitness, inefficient pitching mechanics or an anatomical issue) is not a sentence to a Tommy John surgery and a lifetime of arm problems. In fact, most of those discussions of which pitching mechanics lead to Tommy John completely neglect the other factors as a consideration–perhaps, your favorite mechanical whipping boy hasn’t had arm problems yet because his arm is incredibly fit.
All three of these factors can be managed in the trainer’s and weight room by using high-speed video to analyze someone’s mechanics and make the necessary changes in their training routine.
Every MLB club should be using some sort of program like this to help improve the performance and increase the durability of their pitchers, and the good news is that this type of “prehab” is becoming more popular, though we’re still a long way away from a total solution.
Coming off a Tommy John surgery? We have a return to throwing program that incorporates ballistic training methods.
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