Relationship Between the Medial Elbow Adduction Moment During Pitching and Ulnar Collateral Ligament Appearance During Magnetic Resonance Imaging Evaluation
Hurd WJ, Kaufman KR, Murthy NS. Am J Sports Med. 2011 Feb 18. [Epub ahead of print]
The ulnar collateral ligament (UCL) of the elbow is the most common and serious injury that can occur at the elbow of a baseball pitcher. It has also been seen in other overhead athletes including those performing softball, tennis, volleyball, and javelin throwing. Recently, there has been an increased amount of UCL tears among pediatric athletes, which is a major cause for concern. Throwing frequency has been suggested as a mechanism for UCL tears in both youth and adult athletes, due to the large amount of valgus stress during the late cocking and acceleration phases of throwing. However, no study has examined if a relationship exists between valgus stress during throwing and UCL structural adaptations. Therefore this study examined the relationship between the throwing adduction moment (valgus stress) and the appearance of the UCL on MRI. They included 20 asymptomatic high school baseball pitchers. Bilateral elbow MRIs were recorded and 3D motion analysis was conducted to evaluate the adduction moment during the pitching motion. Based on the MRIs the UCL was graded as either normal or abnormal based on the presence of thickening, signal heterogeneity, and discontinuity. Correlations were then established between the MRI and adduction moment results. They found that the pitchers with elbow MRIs listed as abnormal had a larger adduction moment during pitching. The key characteristic seen in pitchers with abnormal MRIs was UCL thickening.
This is a great study attempting to establish a relationship between structure and function of youth throwers. Their results suggest that young pitchers with a larger adduction moment have a thickened UCL (although the thickness wasn’t directly measured). This is a very simple yet important concept that states that increased stress may result in tissue adaptation; however, studies over time will be required to determine causation. At the present time it is not known if this thickening is a positive or negative adaptation. Longitudinal studies that follow these athletes over time and examine the incidence of elbow injury will help answer this important question. However, from my experience at the shoulder, I feel this is a protective adaptation but only to a critical point. As the elbow is stressed overtime the body will respond by creating more tissue to handle this stress. This can be a good thing that helps to support the increased load and keep the UCL injury free. However, what we don’t know is what are the structural characteristics of the thickened tissue. Normally what we see during microscopic injury and healing is more type III collagen production. This collagen is weaker and more disorganized compared to the type I collagen that was there before the remodeling, so the tissue is getting thicker but it may be that it is also weaker and therefore more prone to injury (This can be seen in research by Mary Barbe https://www.ncbi.nlm.nih.gov/pubmed/19743505 and Louis Soslowsky https://www.ncbi.nlm.nih.gov/pubmed/10810684). I believe a great next step to this study would be to identify if indeed the UCL is being replaced with weak disorganized type III collagen. The results of this study suggest that exposure to abnormal stress can lead to UCL changes. As clinicians we can minimize this stress by limiting the amount of throwing, especially in pediatric athletes. Another important way to prevent UCL tears may be by allow more rest between throwing exposures. What are others thoughts or hypothesis on the mechanism of UCL injury? Do you think changes at the shoulder are affecting the elbow? Or even the hip?
Written by: Stephen Thomas
Reviewed by: Jeffrey Driban
Nice post. I agree that repetitive overloading of a tissue will trigger remodeling that can be advantageous to the patient but lets not forget that this adaptation is preceded by inflammation. Based on Dr. Barbe's papers (who you reference) I think the problem starts when the repetitive overloading is associated with a load that is to great (e.g., abnormal pitching mechanics), high number of repetitions (e.g., to many pitches), and/or not enough time to adequately recover (e.g, not providing for inflammation to subside and remodeling to occur). There's a thin line between repetitive loading that leads to healthy adaptations and overuse injuries. As clinicians, we should keep an eye out for risk factors that may predispose our patients to overuse injuries or negative adaptations. When a patient comes in with an overuse injury or signs of negative adaptations we should look for which variables have changed recently (did they change their throwing mechanics, did they throw more than usual, etc).
Jeff thanks for the comment. Those are great points. The difficultly lies in identifying the risk factor or factors. Since pitching is the most dynamic motion the body can produce, any minor change in the kinetic change can increase stress at another location, in this case the elbow. As clinicians we have to do our best at evaluating the athlete and identify the source. With pitching everything from the toes to the head must be considered, which is often very challenging. But you are right based on the current recommendations limiting throwing exposures and adequate rest between outings is a great place to start.
A bit on rest and kinetic changes, if I may. I agree with the rest comment, Steve, absolutley. It can sometimes be hard for me to get through to the coaches, parents, and kids that I work with because of their drives. The coaches and parents are "old school", for the most part, and think that working harder and longer will fix all problems. The kids are reluctant to rest because they fear standing up to their parents, or hold themselves to unrealistic standards. Even with coaches enforcing rest when at the school, many of these kids go home and throw to a friend/father/pitch-back every night.
From the bio-mechanical stand point, I may be off base, but I believe that lack of pitching-mound-height (or drop for the plant leg, if you like)consistency is a serious problem in our league. If the mound is too low, you're going to run into problems with energy transfer up the kinetic chain. This could lead to an shortened late-cocking phase, or an extended acceleration phase. Both of which, it seems to me, would lead to more tensile force applied to the UCL due to increased application of strength to make up for the lack of kinetic transfer, or to increased time of the acceleration. I frequently have to treat my pitchers for elbow soreness after what they almost always complain about as "pitching off a short mound at" whatever school they happened to play at the previous day. After talking with my coaches, the pitch counts and innings pitched were pretty consistent. I realize that this is TOTALLY anecdotal, but the comments made by you and Jeff brought that up in my mind. Keep up the good work!
Thanks for the comment Pete. I agree it is a consistent battle trying to educate the coaches, parents, and players but by using scientific data, establishing a written protocol for pitchers, and never giving up will help you win the battle in the end. Also when parents identify that you are doing this to help their kids, they will start listening (sometimes!!). It's a fight that you should never give up on.
In terms of mound height it was my understanding that the increased height compared to flat ground throwing is what increases stress and ball velocity. This is typically why throwing progressions go from long toss to flat ground throwing to throwing off the mound. What may be happening is that the mounds aren't well maintained and holes are being dug out by the rubber or at the location where the lead leg lands. These changes to the mound could affect pitching mechanics and cause arm soreness. For example if there is a hole next to the pitching rubber it will be more difficult for the pitcher to maintain pelvic balancing during wind up. This will decrease energy recruitment from the lower extremity and require the shoulder and elbow to make up for that deficit later.
I am by no means an expert in pitching mechanics. What are others thoughts on this topic?
Great post Steve.
Great comments also.
In relation to shoulder changes and affects on the elbow.
Some research I read previously (Data collected by Cooper) looked at this topic and linked IR deficit with medial elbow pain with throwers (atleast that is my recollection).
At one clinic I work, we started doing pre/post season screens for local baseball teams. Looking mainly at GIRD and Total Rotational movement. When athletes present with a history of medial elbow pain there was usually an IR deficit present also. SInce reading that data it is one of the first things I look at when an athlete presents with medial elbow pain..
Funny, on another note, most were doing sleeper stretches (or atleast said they were). When reviewing the stretch most did the stretch incorrectly, didn't hold for the appropriate time or perform daily.
Tom thanks for the comment. I'm not sure if thatwas actually ever published in a peer reviewed journal but I do know the data you are referring to. I believe they also stated that the medial elbow pain was decreased after a sleeper stretching program was started. I completely agree with this association. The theory is that with a tight posterior capsule the pitcher will place their arm in more horizontal abduction during the late cocking phase to decrease the tension on the posterior capsule (horizontal adduction places the posterior capsule in more tension). When this occurs the pitcher's elbow will have more valgus loading and therefore more elbow pain and possible a UCL tear.
Proper stretching techniques is a great thing to consider when working with these athletes. Incorrect technique will not benefit them in the long run.
From what I've seen in my clinical rotations, frequency (too many throws) and inadequate rest time seem to be the most prominent factors when it came to UCL tears. When at the University of the Sciences, I worked with the baseball team and saw two UCL tears and the rehab of one from the season before. Both of the pitchers that tore their UCL's during the season pitched three days back to back to back, both with not enough rest time. They were at their opening weekend in Florida. I feel like if they were at least given adequate rest time or a decrease in the amount of throws, their UCL tear could have been prevented. None of the baseball team was on a hip strengthening program either. They all focused on shoulder strength. Possibly having a better core and hip strength could have reduced all of the stress placed on the UCL while pitching.
My son played baseball for years and last year in 8th. grade he made the change to Track and Field. He is throwing Javelin and Pole Vault. He has be doing very well in the Javelin and 5 weeks ago for the first time his elbow started hurting.
Had xrays and the Local ortho said it was a Avulsion at the UCL. then he had a MRI and the Doctor said the same thing.
The MRI Report states no complete avulsion tear is present and that there is a high grade partial tear of the flexor tendon and that there is calcification and that the UCL is intact.
A few doctors have looked at it and said it looks like a small ucl tear with thinking.
So. that this point we don't know what to do and are trying PT
So once the type of collagen being laid down from these microscopic injuries is confirmed is their a possible adaptation to throwing mechanics that can be made to reduce the valgus stress and still be used as an effective throwing motion?
This study sounds like a great look into the high school level pitchers and the strength and adaptation to their UCLs due to pitching, and possibly overuse of pitching. One possible future study that can be looked into is instead of having high school level athletes as your subjects, use middle school level athletes or little league athletes. One possible complication/hassle with this direction of study is getting waivers signed off by the parents of the athletes.
Tyler and Sam thanks for the comments. Tyler its difficult to know what exactly within the throwing motion is causing increased valgus stress therefore "correcting" that is also difficult. Like I said previously I think limiting the volume of throwing will help to minimize this effect. Adolescent baseball players throw at much to large of a volume. Also these athletes need a period of rest from throwing which should occur during the off-season. This will help the tissue to recover. Aside from that its hard to make recommendations without additional research.
Sam I agree. We need to start looking at the young throwers to identify the initial adaptations that are causing the injuries we see at an older age. That research is more difficult but it does need to be done to advance our understanding.
I find this article to be of great interest particularly for pitchers at the collegiate and professional levels. Generally speaking, pitchers who undergo Tommy John surgery for a torn or partially torn UCL (Harvey, Strasburg, Wainwright, etc.) are deemed to have proper throwing mechanics yet still suffer a UCL injury. Anecdotally, the common denominator is pitchers that throw a slider are more likely to injure the UCL. Is there potentially any concrete evidence that throwing a slider puts a pitcher at greater risk for a UCL injury?
It was stated how type III collagen is weaker and more disorganized than type I collagen, therefore possibly making the UCL ligament and its thickened components weaker. However, is the structure really weaker just because type III collagen is being laid down as opposed to type I? It could have the possibility of being stronger than before just not as strong as if type I collagen was being laid down around the UCL.
I found this article to be very interesting. One would believe that a thicker tissue is a stronger tissue. But as the article talks about different collagen fiber types laid down may actually effect the strength of the connective tissue. (Type 1 being stronger than Type 3) I am intrigued to see the results when they do look at collagen type. I think that the real cause is the volume and frequency in which someone pitches, especially with the valgus stress component. The body gets stronger with rest, maybe we are just overdoing it.
This article allows for one to think about how biomechanics can effect the human body. It also allows for me as a student to think and evaluate how biomechanics change the human body and how injuries can occur. In the case of the UCL, you would think that because the ligament is thickening, that it is becoming stronger. But, because of the extra valgus stress on the UCL, the new collagen fibers that are laid down in an opposite pattern than that of the original ligament, increasing chances of UCL rupture. One question I could pose to this article would be what are some effective ways that we, as clinicians can educate about proper biomechanics in order to try and decrease the stress that is put on the ligament?
I think this was a good study, although I think it would have helped if the UCL was measured. I think the thickness of the UCL could have a difference on how much valgus stress is put on the elbow during adduction. I also agree that a persons elbow could adapt to the thickness of their UCL, yet every person is different and their body acts differently. It all depends on how the body reacts to the amount of valgus stress that is put on the UCL. That could have a huge difference on how the UCL tears or gets injured, compared to other people's elbows. This is important for athletic trainers to know so they can compare how a person's UCL may adapt to how they are throwing, compared to the size of others. There could be a pattern that would be important for athletic trainers to know so to go further into this research could be really helpful.
Matt there has been some research suggesting that throwing a slider at a young age will increase the likelihood of elbow pain (https://www.ncbi.nlm.nih.gov/pubmed/12130397). Typically I think kids dont have the ability to throw a slider correctly and that will lead to elbow problems.
Joey and Michael you bring up a good point. If a ligament adapts with increased thickness and that is from type III collagen or other types of collagen other than type I then the structural properties (stiffness) may stay the same but the material properties (modulus) will be different. Often the thicker ligament with type III collagen will be able to withstand the loads but only temporarily since the underlying cause of this tissue adaptation has not been corrected.
Kayleigh that is a great question and unfortunately we still dont have a correct answer. We have yet to identify the biomechanical cause and most likely it is multifactorial and therefore not as straightforward identifying.
Jenn I agree we need to conduct more research in this area to identify the source of the problem which will make us better clinicians.