Thoracic Outlet Syndrome

I was talking with my Dad the other evening about St. Louis Cardinals pitcher Chris Carpenter and his return from surgery to relieve his symptoms due to thoracic outlet syndrome (TOS).  This is not a very common injury, but it can lead to a lot of pain and weakness, which is obviously a major problem for a baseball pitcher.  I will outline the basic principles of TOS below.

Before talking about the syndrome, we first need to define the thoracic outlet.  If you look at the top picture, you will see a group of nerves coming out of the spinal cord, and running down between the scalene muscles, behind the clavicle, and in front of the first rib, and then down into the arm.  This group of nerves is known as the brachial plexus.  The opening between the scalene muscles and the ribcage is the thoracic outlet.  There are also blood vessels not pictured above that pass through this space.  Any time there is a nerve or group of nerves passing through a tight space, there is a chance that some of the structures can "press" on the nerves, which can lead to pain, tingling, numbness, and weakness in the affected area.  In TOS, it could be the scalene muscles, the clavicle, or the first rib pressing on the nerves.

What causes TOS?  There are many potential causes, including a fractured clavicle, tightness or scar tissue in the scalene muscles, the presence of an extra first rib (yes, some people actually have 13 instead of 12 pairs, but the presence of an extra rib does not necessarily lead to TOS), pressure from the normal 1st rib, repetitive stress, such as repeating the overhead throwing motion, or poor posture.  The signs and symptoms include pain along the side of the neck, the upper arm, and possibly the lower arm.  Numbness, tingling, and weakness in the shoulder and arm may also be present.  These symptoms are similar to other conditions, such as a herniated disc, which can make diagnosing TOS difficult.

In the case of Chris Carpenter, his TOS was likely caused due to the repetitive stress of the overhead throwing motion.  He had similar symptoms back in 2008, but they did not resurface again for several years.  His symptoms first resurfaced during spring training, when he was diagnosed with a herniated disc.  He was prescribed rest followed by strengthening exercises for the neck, shoulder, and arm.  After a couple of months of rehab, he attempted to pitch again, but could not because the pain returned.  He was then referred to a specialist who made the diagnosis of TOS and recommend surgery to remove his first rib and release some of the scar tissue around the scalene muscles (I am not sure if he had an extra first rib or not).  He has responded well since the surgery and is attempting to pitch again this year, but at the least he should be healthy to start next season (or relatively healthy for a 37 year old pitcher).

In many cases, therapy and postural changes can relieve most of the symptoms of TOS.  Surgery is often seen as a last option, because it does carry some risks since the surgeon has to operate close to many nerves.  

Gruesome injury

Last Thursday night during a preseason NFL game, Tennessee Titans wide receiver Marc Mariani suffered a compound fracture of his tibia and fibula while returning a punt.  I'm going to place the picture of the injury and video at the bottom of the post in case you don't want to see it.  This was a very bad injury.  It likely resulted in an open fracture, where the broken bone(s) punctures the skin.  This can lead to complications from infection because of the open wound.  What type of loading caused this injury?

The type of loading that caused this injury was bending.  Bending occurs when there is tension (think about making an object longer and skinnier) on one side of the bone, and there is compression  (think about making an object shorter and wider) on the other side of the bone.  To fully understand the injury, you must watch this video.  As Mariani is moving forward, his left foot is stepped on by one of his teammates.  This stops the momentum of his foot.  However, his lower leg and the rest of his body continues to move forward due to their inertia.  His lower leg makes contact with the other players leg a few inches above his ankle.  This stops the momentum of his lower leg, but the rest of his body continues to move forward.  The point of contact between Mariani's lower leg and his teammates lower leg basically acts as a fulcrum, and the bending forces placed on the tibia and fibula exceed the strength of the bones, and they fail (break).  Adult bone is weaker in tension than compression, so the fracture likely started on the side opposite of where his leg made contact with his teammate's leg.

Human bone is very strong, and it can withstand a large amount of force before breaking.  In these cases of extreme fractures on the football field, it is often times an example of all the forces being lined up in just the right positions to cause a fracture like this.  If Mariani's teammate had not stepped on his foot, there is a good chance he would not have sustained an injury at all.  The Titans are reporting that surgery went well, and hopefully he will have a chance of returning to the field next year.

The Stephen Strassburg Debate

If you are a major league baseball fan, then you have probably heard that the Washington Nationals plan on shutting down their ace pitcher, Stephen Strassburg, after he pitches around 170-180 innings this year.  What is their rationale for doing this?  Strassburg is a young pitcher, and he had ulnar collateral ligament reconstruction surgery (Tommy John surgery) a little less than 2 years ago.  Their theory is that by limiting the number of innings he pitches in his first full year of pitching after the surgery, they will help prevent him from becoming injured in the future.  Is this the right approach to take? 

The Argument for shutting him down: There is no doubt that the overhead throwing motion used by baseball pitchers places a lot of stress on the shoulder and elbow.  Most of these pitchers begin pitching at a relatively young age, and the cumulative stress of every inning pitched, bullpen session, and warm-up throws can lead to a degradation of the soft tissue of the shoulder and elbow.  A torn UCL is often times not the result of one traumatic event, but an accumulation of small tears in the ligament that cause it to weaken over time and eventually rupture during the execution of a pitch.  Also, labrum (the cartilage lining of the socket of the shoulder) tears in pitchers often occur due to the repetitive stress placed on the joint from throwing thousands of pitches.  This is why the Nationals want to shut Strassburg down.  He is relatively young, he already had one major surgery, and has the potential to win many games for them in the future.  By shutting him down early, they will help prevent excessive stress from being placed on his arm, and they are counting on this to keep him healthy in the future.

The Argument against shutting him down: From a purely baseball prospective, the goal is to win as many games as possible, make it into the playoffs, and win the World Series.  The Washington Nationals are not a franchise rich in postseason history.  This is their best chance to make it to the World Series.  The franchise has only been to the playoffs one time in their history.  Strassburg is one of the best pitchers in baseball, and to have a good chance of winning in the postseason, you really need your best players to play.  Also, there is no evidence to suggest that by shutting Strassburg down, he will not have a major injury in the future.  There have not been any studies conducted to investigate this question.  Also, Strassburg recently had his UCL reconstructed, so at this point, it should be very strong.  The Nationals should have a good team for the next few years, but in sports, you never know how many chances you are going to have to win a championship.

What would I suggest?  If it were me, I think I would continue to let him pitch, but would closely monitor his pitching mechanics for signs of fatigue and breakdown.  If Strassburg started to make changes to his throwing motion because he was fatigued due to all the pitches he has thrown this season, I would consider shutting him down or giving him a break.  The Nationals could also limit his innings over the last few weeks of the season so he could pitch a few games in the postseason without throwing an excessive number of innings.  However, you have to admire the Nationals organization for taking a pro-active stance on the number of innings they are going to allow him to pitch.  It seems like a majority of the time teams place winning ahead of player safety (especially football), so it is refreshing to see a team take a stand like this.  Hopefully it works out for Strassburg and he is able to have a long and relatively injury free career.  Even if Strassburg does not sustain another major injury for the rest of his career,  it will not be possible to cite his shutdown this year as the cause.  There are too many factors that effect whether or not an athlete sustains an injury to credit one singular event.

First day of classes

Today marks the first day of classes at Mississippi State University.  The first day is always an exciting time, and probably scary for some of the students.  I was talking with my wife the other day, and since we both started Kindergarten at age 5 back in 1987, we have either been in school or working at a university for the past 26 years.  We both love our jobs and interacting with the students.  I tell all my students that I want them to be successful and will do anything I can to help them succeed. 

I am teaching 3 courses this semester, and 2 of the classes are ones I have not taught previously.  I am teaching anatomical kinesiology for the 9th time during my 4 years at Mississippi State, and it is easily one of my favorite classes.  It is basically an overview of musculoskeletal anatomy starting with the foot and working up the body to the head and then down to the shoulder, elbow, and wrist.  My goal for the students by the end of the semester is that when they see a person performing a movement, they can name the joints that are involved, and the muscles that the person is using to accomplish the goal of the movement.

A new class I am teaching this semester is neural control of human movement.  I have previously taught motor development and motor learning, so I have some experience teaching about the nervous system.  To me, the nervous system is the most important system in the body, especially when it comes to human movement.  The nervous system is probably the most complex system as well, which makes the course challenging but fun.  There are many neural processes that occur during voluntary movement that we are not even aware of the majority of the time, and even the smallest disruption can cause errors in movement.  I am planning on starting another series of blog post on neural control very shortly.

The third class I am teaching this semester is a freshman seminar based on the television show "House."  This is a one hour course designed for students that are new to Mississippi State.  I have been a big fan of the show House and all the different medical mysteries on the show.  We are going to examine some the cases on the show and see how realistic they are.  We will also discuss why the doctors choose specific diagnostic tests.  It should be a lot of fun and a learning experience for all of us.

On the research side, we are about to begin a study this Wednesday investigating the relationship between ankle laxity ("looseness in the ankle joint"), balance, and landing kinetics (forces).  The study will examine people that have never sustained an ankle sprain, people that sprain their ankles frequently, and people that have sprained their ankle before but do not have any long term problems.  We are trying to see if there are differences in these variables between these different groups.  Several undergraduate students are taking a prominent role in this study.

All in all, it should be an exciting semester.  I am going to do my best to post at least two blog posts a week, so be sure to check back regularly. 

Just what are the benefits of PED use for baseball players?

Yesterday, major league baseball announced that San Francisco Giants outfielder Melky Cabrera tested positive for excessive testosterone, earning him a 50 game suspension.  Now, the debate has begun again, just like it does anytime an athlete tests positive for PED use, as to just how much of an advantage he or she gained by taking the banned substance.  The problem is, there is no clear answer to this question.

The reason this question cannot be definitively answered is that there is no way to isolate the effects of certain PEDs in a controlled laboratory setting (also, it would be nearly impossible to receive approval to conduct a study where these types of drugs were given to human participants).  There are numerous factors that effect the performance of a baseball player, including, but not limited to, hand-eye coordination, amount of practice/experience, motivation to perform, psychological status, muscular strength, muscular flexibility, etc.  While it is true that Cabrera's batting average has increased 91 points in two years, the effect that the excessive testosterone had on this increase cannot be determined.  Every other factor that could cause improvement in batting average cannot be controlled in order to isolate the effects of the testosterone. 

Now, I am not advocating the use of performance enhancing drugs.  They definitely can help cause increase in muscular strength, and they definitely have some very bad side effects, and they should not be allowed in athletics, as using them is a form of cheating.  However, scientists and researchers cannot quantify specifically how much of an advantage these drugs give an athlete.  Also, the punishment for a first time offense in both MLB and the NFL is not severe enough to discourage athletes from experimenting with PEDs.

Running with a fractured fibula

Although the Olympics are over, there is still time to examine some of the things that occurred over the past two and a half weeks.  One of the most impressive was US sprinter Manteo Mitchell finishing has leg of the men's 4 x 400 meter relay despite the fact that he was running on a fractured fibula.  How was he able to do this?  There are many factors that come into play, including his psychological condition and motivation, pain tolerance, and the fact that he is a world class elite athlete.  The only factors that I am able to analyze are the anatomical and biomechanical factors.

The fibula is the smaller, thinner bone located on the lateral (outer) side of your lower leg.  At the proximal (top) end, it articulates with the tibia (knee), and at the distal (bottom) end, it articulates with the tibia and helps form the ankle.  The "bump" on the lateral side of your ankle is the lateral malleolus, which is part of the fibula.  Due to the placement and size of the fibula, it does not play as large of a role in force absorption and weight bearing as the larger tibia does.  In fact, about 10-15 % of the force from the ground during walking and running is absorbed by the fibula, and the other 85-90% is absorbed by the tibia.  Even though it does not absorb as much force as the tibia, it is still a critical bone to transfer force from the foot and ankle up to the knee, and without a fibula, it would be nearly impossible to walk or run.  If Mitchell had fractured his tibia, he likely would not have been able to finish the race.  Since he fractured his fibula, he was able to finish, which was a very impressive accomplishment, not only because of the intense pain he was in, but also because the fractured fibula disrupted the normal transfer of force between the ground, and his foot, and ankle, and lower leg.  This is just speculation, but there is probably not a high percentage of people that would be able to continue running with a fractured fibula.

Biomechanics and the Olympics:Part X

Since the Olympics are ending on Sunday, this will be the last post of the series.  Again, with track and field being the focus of the Olympics this past week, some of these athletes are putting up really fast times.  Newton's third law is a critical factor in a person's capability to run fast.  Newton's third law is the law of action/reaction: "for every action there is an equal and opposite reaction."

In order for a person to walk or run, they exert a force from their foot into the ground.  The ground will push back with the same amount of force, but in the opposite direction.  This force from the ground is known as the "ground reaction force" and can be measured in a laboratory setting using an instrument called a force platform.  This force is measured in three directions: 1) vertical (straight up and down), 2) anterior-posterior (forward and back), and 3) medial-lateral (side to side). 

The way a person moves is influenced by the magnitude of the force applied as well as the direction the force is applied in.  If you want to jump as high as possible, you push straight down into the ground, and the ground pushes you straight up.  Almost all of the ground reaction force is in the vertical direction.  If you want to jump for maximum horizontal distance, you will apply a force both down and back into the ground, and the reaction force will push you up and out (consider a long jumper, they are trying to jump as far as possible, which has both a horizontal and vertical component).  When a person is running, they have a greater posterior ground reaction force when the foot hits the ground, and a greater anterior reaction force when they push off, which will propel them forward.  If a sprinter wants to increase his or her running velocity, he or she will need a greater anterior ground reaction force than posterior ground reaction force.  These sprinters are able to apply a large amount of force into the ground, at the optimal angle, in order to maximize the ground reaction force and run at very fast velocities.