Josh Donaldson has a dead arm. But what does that mean?

The rumors that Josh Donaldson has been dealing with throwing issues surfaced nationally on opening day.  Donaldson continually exhibited weakness in throwing across the diamond. His throws lacked the velocity and accuracy required to play 3rd base.

As fans and media alike wondered what was going on with Donaldson, both he and manager John Gibbons sought to get out in front of the story by minimizing Donaldson’s injury and reporting that they have been treating it since the start of spring training.  Gibbons reported that Donaldson’s arm “was hanging a bit” throughout the spring and that he is dealing with a “dead arm”.

Donaldson himself has stated that his shoulder is a non-issue.  He has admitted that his shoulder feels “weak” and that if he doesn’t need to air throws out, he won’t.  However, and possibly more importantly to the Jays in 2018, Donaldson states that his shoulder weakness does not affect his hitting.

Donaldson and the organization are seeking to minimize his lack of arm strength while simultaneously trying to avoid a PR nightmare induced by fan speculation.  But what is a dead arm, and what does scientific evidence tell us about its cause? How can a player be rehabililtated while avoiding a stint on the DL?

Dead arm is “any pathologic shoulder condition in which the thrower is unable to throw with preinjury velocity and control because of a combination of pain and subjective unease in the shoulder.”

First, let’s look at the anatomy of the shoulder capsule and define terminology to better understand what is happening. Three bones make up the shoulder girdle: the scapula, clavicle, and humerus.  The humerus and the scapula move together in rhythm during all motions of the arm. Ever seen someone have to shrug to lift their arm? Generally the cause is weakness in the rotator cuff muscles and a lack of mobility of the scapula.  The scapula has to move with the arm for normal motion.

322343.image0

The two form the glenohumeral (GH) joint, a ball and socket joint, that is designed to move in all planes.  The labrum of the shoulder,  thick cup shaped caritlage, reinforces the ball and socket joint. Moreover,the GH joint is housed in a capsule, that separates it from the rest of the body and provides fluid to the joint.  Ligaments provide stability within the capsule while the muscles of the rotator cuff insert on the head of the humerus.

The overhead thrower has developed bony anatomical changes to their humerus over repeated use.  Increased throwing leads to an increase in shoulder horizontal abduction and external rotation range of motion (ROM) compared to the non throwing side.  These anatomical changes to the humerus bone is called humeral retroversion. Greenberg, et. al describe the changes as follows:  “Throwing athletes exhibit a more posteriorly oriented humeral head (humeral retrotorsion) in the dominant arm. This asymmetry is believed to represent an adaptive response to the stress of throwing that occurs during childhood.”

What this means is that as we grow up throwing, our humerus “twists” at the growth plate, allowing us to achieve more external rotation in the late cocking phase.  This asymmetry in the throwing arm is normal.  The bony changes are adaptive in nature and allow for an increase in external rotation (ER).  And when we look at throwers, they will have more ER range of motion and decreased internal rotation (IR) range of motion compared to the non-throwing arm.

Orthopaedists have seen this phenomenon and attributed the lack of IR in throwers as a cause for concern.  However, these adaptive changes are normal.  In the picture above, the main thing to notice is that the total arc of motion is unchanged.  180 degrees of motion is normal. Many researchers have attributed the lack of internal rotation range of motion as problematic and the cause of dead arm syndrome.  They advocate posterior capsular tightness as the culprit.  This theory does not account for humeral torsion and natural adaptations. Throwers need increased ER in order to generate velocity. However, increasing internal rotation ROM would increase the total arc of motion causing the shoulder to become more unstable.

GIRD-glenohumeral-internal-rotation-deficit
https://mikereinold.com/gird-glenohumeral-internal-rotation-deficit/

These IR ROM deficits have been identified as Glenohumeral Internal Rotation Deficit (GIRD).  GIRD is attributed to posteroinferior capsular tightness. The studies I have read seem to ignore the bony changes to the humerus.  They attribute the lack of IR as an abnormality and not an adaptation. The difference in ROM measurements is not due to soft tissue restrictions It is due to the bony adaptations we undergo as adolescents.  I played baseball through high school. My fastball touched 73 miles per hour. However, 20 years later, I still have increased ER and decreased IR compared to my non-throwing arm.

More likely, Donaldson’s dead arm is the result of weakness over his scapular stabilizers (muslcles of the rotator cuff, serratus anterior, middle and lower trapezius), malposition of his scapula and tightness of his pectoral muscles.  If his total arc of rotational motion is less than 180 degrees, rehab would entail stretching of his posteroinferior capsule.

So if GIRD is normal, then what is going on with dead arm?  What is the worse case scenario? Repeated overuse of accelerating the arm in the late cocking phase can cause a superior labral lesion from anterior to posterior (SLAP).  Arthroscopy of throwers diagnosed with SLAP lesions reveal a peel back phenomenon. In the late cocking phase, the bicep can cause a torsional force on the labrum. The “peel back” refers to a peeling of the superior labrum from the bone.  Depending on the severity, SLAP lesions can be treated non operatively through interventions designed to correct throwing biomechanics.  Depending on the size of the lesion, surgery may be indicated.  I don’t want to focus on that simply because I am operating on what we know.  That Donaldson and the Jays have been dealing with this since the start of spring training.  . Assuming the Jays have performed an MRI, we can possibly assure ourselves that there is no labral tear or rotator cuff involvement.  But we can never know for sure. Throwing injuries seem to pop up completely out of the blue.

How does one get dead arm?  As of yet, there is no tested research that says , “If X and Y occur then…”  But what we do know is that over use injuries can present themselves in different ways.  Without knowing Josh Donaldson’s body and his offseason work out regime, I can’t say.  But I can say with absolute certainty that “the overhead throwing motion is a high-velocity, extremely stressful athletic movement. Its repetitive nature places tremendous demands on the entire body, frequently resulting in injury to the throwing shoulder.”

What does that mean for Donaldson, the Blue Jays, and their fans?  Treatment consists of stretching, strengthening (the Advanced Thrower’s Ten), plyometric drills, and an interval throwing program.  What we can deduce based on the evidence is this: dead arm is not something that you play through or tough out.  The arm will not get stronger by throwing more.  The mechanics of the scapula must be corrected.

Rehabilitation will improve position and control of the patient’s scapula.  I haven’t seen a picture of Donaldson’s shirtless back. Nor have I seen how his scapula moves and the position relative to the left scapula. Moreover, I don’t know what his total arc of rotational range of motion is.  So without being able to assess him, let’s assume that his dead arm is due to scapular dyskinesis (faulty movement and malposition of the scapula) and weakness in the rotator cuff. This assumption is based on Donaldson’s description of symptoms and lack of pain.  The above therapeutic exercises and neuromuscular re-education should get him back on the field and at full strength. Based on reports that I’ve read, Donaldson and the Jays medical staff have been treating his shoulder throughout the spring. Gibbons has stated they expect Donaldson to play in the field “within the next couple of days.”  Donaldson has said he feels close to normal.

So I do not believe this “injury” to be serious.  It may linger throughout the season but the absence of pain and Donaldson’s own words about how he feels are all we have to go by.

This is a make or break year for Donaldson.  Set to become a free agent at the end of the season,  Donaldson will need to prove to teams that his arm is healthy in order to maximize his earning potential.

 

**Jason Woodell is a licensed physical therapist assistant at Johns Hopkins All Children’s Hospital Sports Medicine and the James A. Haley Department of Veteran Affairs in Tampa, FL**

 

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s