Home Posts tagged "Growth Plate"

Understanding Elbow Pain – Part 3: Pitching Injuries

In case you missed them, check out Part 1 (Functional Anatomy) and Part 2 (Pathology) of this series from last week.  With that housekeeping out of the way, let's move forward to today's focus: elbow injuries in throwing athletes.  I work with a ton of baseball players and I know we have a lot of not only players, but parents of up-and-coming baseball stars that read this blog - so it's a topic that is near and dear to my heart.  While my primary focus within the paragraphs that follow will be baseball, keep in mind that the many these issues can also be seen in other overhead athletes.  They just tend to be more prevalent and magnified in a baseball population. Obviously, in dealing with loads of baseball guys, I see a lot of elbow issues come through my door.  The overwhelming majority of those folks are medial elbow pain, but we also see a fair amount of lateral elbow pain. What's interesting, though, is that in a baseball population, most of these issues are purely mechanical pain; that is, the discomfort is usually only present with throwing, as it is tough to reproduce the velocities and joint positions present during overhead (or sidearm/submarine) throwing.

bradford

The question, logically, is why do some throwers break down medially while others break down laterally, or even posteriorly? In other to understand why, we first have to appreciate the demands of throwing.  And, that appreciation pretty much always leads back to the valgus and extension forces (termed valgus-extension overload by many) that combine to wreak havoc on an elbow during throwing. At late cocking - where maximal external rotation (or "lay-back") occurs - there is a tremendous valgus force of 64Nm on the elbow, according to Fleisig et al.

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As Morrey et al. determined, the ulnar collateral ligament (UCL) "takes on" approximately 54% of this valgus force - meaning that it's assuming about 35Nm of force on each pitch.  This is all well and good - until you realize that in cadaveric models, the UCL fails at 32Nm.

huh

If the valgus forces are so crazy that they actually exceed the UCL's tolerance for loading, why don't we just rip that sucker to shreds on every pitch?

It's because the UCL doesn't work alone.  Rather, we've got soft tissue structures (namely, the flexor carpi ulnaris and radialis) that can protect it.  This is why cadavers don't usually pitch in the big leagues.  The closest thing I've seen is 84-pound Willie McGee, but he was an outfielder.

williem

Keep in mind that it isn't just the UCL that's stressed in this lay-back position.  Obviously, the flexor-pronator mass takes a ton of abuse in transitioning from cocking to acceleration.  It's also a tremendously vulnerable position for the ulnar nerve as it tracks through some tricky territory.  That just speaks to the medial side of things; there is more to consider laterally.

You see, the same valgus force that can wreak havoc medially also applies approximately 500N on the radioulnar joint during the late cocking phase of throwing; that's about one-third of the total stress on the elbow.  In this case, a picture is worth a thousand words:

compressive-forces

So, the same forces can cause a thrower to break down in multiple areas both medially and laterally!  What usually separate the medial from the lateral folks? Let me ask you this: when was the last time you saw an 8-year old rupture his ACL?  Never. Now, when was the last time you saw an 8-year-old break a bone?  Happens all the time. This same line of reasoning can be applied to the pitching elbow.  The path of least resistance - or the area of incomplete development - will generally break down first.  As such, in a younger population, we generally see more lateral, compression-type injuries to the bones. These are your growth plate issues and Little League Elbows, usually.

llelbow

As athletes mature and the bones become sturdier, we get more muscle/tendon, ligament, and nerve issues on the medial side. This isn't always the case, of course; you'll see young kids with medial elbow pain, and experienced throwers with lateral issues as well. It generally holds pretty true, though. The issues at the cocking-to-acceleration transition would be bad enough by themselves, but there is actually another important injury mechanism to consider: elbow extension.

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This lateral area also takes on about 800N of force at the moment arm deceleration begins with elbow extended out in front as posteromedial impingement occurs between the ulna and the olecranon fossa of the humerus.  This bone-on-bone contact at high velocities (greater than 2,000 degrees/second) can lead to fractures and loose bodies within the joint. This wraps up the causative factors with respect to elbow pain in throwers - but I need to now go into further detail on the specific physical preparation and mechanical factors one needs to consider to avoid allowing these issues to come to fruition.  Stay tuned for Part 4.

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The Truth About Strength Training for Kids

A while back, I attended a seminar in Houston, and while the primary topic was how to improve pitching performance, one of my biggest takeaways was with respect to adolescent physiological development.  Long-time Phillies rehabilitation consultant Phil Donley presented some excellent data on when bones actually become skeletally mature.  The next day, another speaker made a what was, in my opinion, an uninformed comment about how kids shouldn't strength train at young ages because it would stunt their growth.

Let's start with Donley's very intriguing numbers (which have actually been available in the literature for over two decades now); we'll stick with the shoulder girdle just to keep things to-the-point.  In a baseball population, the epiphysial plate most commonly injured from throwing at the shoulder is located at the proximal humerus (Little League Shoulder); this physis (growth plate) accounts for about 80% of humeral growth, and matures by age 19 in most folks.

growthplates

We've seen a lot of kids come through our door with this issue because of throwing (internal rotation of the humerus during throwing is the fastest motion in sports) and even some traumatic falls - but I can honestly say that I've NEVER seen one from strength training.  So, anecdotal evidence for me shows that strength training for kids is far from what could be considered "dangerous" for developing bones.

youthpitcher

Now, here's where it gets more interesting: bone maturation isn't uniform across the body.  While the proximal humeral growth plate might mature at 19, the distal (down by the elbow) physis is finished between ages 10 and 16.  The proximal and distal radius plates might mature anywhere between 14 and 23.  Meanwhile, the clavicle matures at ages 22-25, and the scapula generally matures by age 22.  How many of you have ever heard of a college football being held out of weight training for all four years of his participation because all that bench pressing might stunt the growth of his clavicles and scapulae?  It just doesn't happen!  In reality, we know that the strength training benefits of increased muscle size and strength actually protect him from injury on the field.

youthbaseball

In other words, violent (throwing) and traumatic (falling) events far exceed any stress on a young athlete's bones that we could possibly apply in a strength training setting, where the environment is controlled and overload is gradually and systematically increased over time as the athlete becomes more comfortable with it.  I'd make the argument that a young athlete should start resistance training as early as his/her attention span allows for it; the emphasis, of course, would be on body weight exercises, technical improvement, and - most importantly - keeping things fun.

If you really think about it, an athlete is placing a ton of stress (4-6 times body weight in ground reaction forces, depending on who you ask) each time he/she strides during the sprinting motion.  Kids jump out of trees all the time.  They lug around insanely heavy backpacks relative to their body mass.  Performance, general health, and self-esteem benefits aside, it's only right to give them a fighting chance in trying to avoid injury.

Also, another great point Phil made (although it was on an unrelated topic, it pertains to us) was that as an adolescent athlete grows, his center of gravity moves further up from the ground.  This is a big part of the "lapse" in coordination we see in kids during their growth spurts.  A little bit of strength goes a long way with respect to maintaining the center of gravity within the base of support, and makes an athlete more comfortable "playing low" (hip and knee flexion) to bring that center of gravity closer to the base of support.

All that said, appropriate resistance training is not only safe for kids; it's also tremendously beneficial.  In a review just published by Faigenbaum and Myer, the authors concluded:

Current research indicates that resistance training can be a safe, effective and worthwhile activity for children and adolescents provided that qualified professionals supervise all training sessions and provide age-appropriate instruction on proper lifting procedures and safe training guidelines. Regular participation in a multifaceted resistance training program that begins during the preseason and includes instruction on movement biomechanics may reduce the risk of sports-related injuries in young athletes.

Dr. Avery Faigenbaum has actually published a ton of great research (including position stands for numerous organizations) on the topic of strength training for kids in recent years; you can find all of it by searching for his last name at www.pubmed.com.

In the meantime, I hope this blog can help to eliminate the gross misconception in the general population that resistance training can't be beneficial for children.  When performed correctly and made fun, it is safe and provides tremendous benefits to kids in both the pre-adolescent and adolescent stages.

For more information on the best approaches to training youth athletes, I'd encourage you to check out the International Youth Conditioning Association's High School Strength and Conditioning Certification, a resource I co-authored.

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