Thrower's Shoulder

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Definition/Description

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Epidemiology /Etiology

While many sports involve overhead throwing, baseball pitchers compromise a plurality of those throws and over half of the throws made in a baseball game.

The etiology behind a throwing injury can be analyzed by looking at the different phases of an overhead throw. The phases of an overhead throw consist of a wind up, stride, cocking, acceleration, and deceleration phase.. Each phase will illustrate the definition, injury occurrence rate, and lastly pathological possibilities. They are as follows:

Wind up Phase

The wind up phase which is defined as the initial movement to maximum knee lift of stride leg. During the initial movements the pitcher brings his or her hands overhead and lowers to chest level. During these simple movements consider the actions proximally to distally. EMG studies show that the upper trapezius has a maximum voluntary isometric contraction (MVIC) of 18%, serratus anterior 20%, and anterior deltoid 15%. During this phase the muscle activity is quite low and for these reasons risk of injury is low as well.

Arm Cocking Phase

Arm Cocking Phase can be defined as the beginning of lead foot contact and ends at maximum shoulder ER. A substantial amount of kinetic energy is transmitted to the shoulder, approximately 80% bodyweight, from the lower extremities and trunk rotation. Due to the circumstances the scapula and shoulder muscles are highly activated to promote and sustain movements of the shoulder, especially external rotation. Special focus to anterior instability in this phase is vital due to the high ranges of external rotation reached in this phase. In a study of pitchers with chronic anterior instability stimulation of mechanoreceptors within the glenohumeral joint excited and/or inhibited certain muscles. The bicep brachii and supraspinatus are shown to be initiated or excited by these mechanoreceptors and assist with prevention of anterior instability. Overtime the excessive utilization of the bicep brachii could lead to a superior labrum anterior to posterior (SLAP) tear. Simultaneously the pectoralis major, subscapularis, and serratus anterior are inhibited which typically decelerate shoulder external rotation in this phase. When these actions cannot be preformed there is increase likelihood of anterior instability at the glenohumeral joint.

Arm Acceleration Phase

The arm acceleration phase begins at maximum shoulder external rotation and ends at ball release. During this phase it is vital to maintain scapula position due to the forward acceleration of the arm which is equlivant of a peak internal rotation angular velocity of approximately 6500⁰/sec near ball release. Improper positioning of the scapula may cause increase risk of shoulder impingement. Coupled with the arm cocking phase this phase has also been hypothesized to be at increase risk of various shoulder injuries due to the high kinetic energy generated from lower extremities.

Arm Deceleration Phase

The arm deceleration phase begins at ball release and ends at maximum shoulder internal rotation. Typically the concern in this phase is the deceleration of the forward progression of the arm safely. Escamilla et al states that a shoulder compressive force slightly greater than bodyweight is generated to resist shoulder distraction, while a posterior shear force of 40–50% bodyweight is generated to resist shoulder anterior subluxation. Due to the high forces generated in this phase the vulnerability of posterior muscles is highly susceptible to tensile overload undersurface cuff tears, labrum and bicep pathologies, capsule injuries, and internal impingement.

Characteristics/Clinical Presentation

• Thrower's Paradox - The balance between mobility and functional stability. -JM_Wilk Article

The ability to provide the best physical therapy for the throwing patient involves understanding the phases and biomechanics behind throwing. It is important to note that while these athletes are throwing with their arms, that they gain a large, important amount of momentum and force through the use of their legs and torso. This section will mostly pertain to the upper extremity's influence on throwing.

The picture below depicts an overhead view of the alignment of the body during the acceleration phase of throwing. Note the 15 degree angle of the foot away from the center of the mound. The stride ankle also typically lands approximately 10cm away from the same midline with a distance from the rubber averaging 87% of the pitcher's height. Fleisig emphasizes the importance of these values by describing the change in force exhibited on the shoulder when they deviate from the norm. During the cocking phase, Fleisig reports a 3.0N increase in anterior force at the shoulder for every extra cm. and a 2.1N increase in anterior force at the shoulder with every degree increase. Please note that decreasing the distance away from center or decreasing the angle did not result in increased anterior force on the shoulder. So, because of the increased anterior force on the shoulder, it can be assumed that over time the anterior ligamentous structures to the glenohumeral joint may be compromised. This finding is consistent with the anterior glenohumeral instability found in many throwing athletes and emphasizes the importance of proper mechanics throughout the entire kinematic chain.

File:Pitching angle foot and leg.png

Image:Pitching_angle_foot_and_leg.png

 

There is inconclusive evidence as to whether or not glenohumeral external rotation during the earlier phases of throwing (such as stride foot contact) has a positive or negative impact on throwing kinematics or injury occurrence. Some studies claim that increased external rotation increases the risk for injury while others refute the same statement. It is hypothesized that total amount of external rotation at the glenohumeral joint (PROM) may be predictive of increased throwing velocity and increased risk for injury at the glenoid labrum and/or rotator cuff, especially when the loss of internal rotation exceeds the gained external rotation. It is possible that the mechanism for labral tear is caused by the deceleration force imposed by the biceps tendon's attachment to the superior labrum.

Differential Diagnosis

• Rotator Cuff Tear
• Rotator Cuff Tendonosis/itis
• SLAP Lesions
• Subacromial Impingement
• Internal Impingement
• Primary Instability
• Osteophyte Formation
• Acute Traumatic Instability
• Improper Mechanics

Examination

The physical examination of an overhead throwing athlete should involve a thorough upper quarter examination that includes the joints above and below the shoulder.  The injuries incurred by these athletes are wide ranging requiring thourough evaluations to tease out the pathology. The basis of the examniation should involve; observation, palpation, range of motion assessment, flexibility testing, manual muscle testing, joint accessory motion, and special tests. Comparisons should be made between the involved and uninvolved shoulders looking for hyoertrophy or atrophy of muscles as well total ranges of motion. Due to the tremendous involvement of the shoulder girdle, examinations of the the overhead thrower should thoroughly investigate scapulothoracic rythm as well as the individual motions at the AC. SC. and GH joints. The anterior, inferior, and posterior portions of the joint capsule must be evaluated to determine whether a hyper or hypomobility is present:

Capsular Mobility Assessment

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Internal Impingement TIC:

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Rotator Cuff Tear TIC: Drop Arm Sign (Not Shown), Painful Arc, and Infraspinatus muscle test

Biceps Load II Test (For a Labral Tear involving the Biceps Brachii):

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Shoulder Apprehension Test (Anterior Subluxation or dislocation):

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Medical Management (current best evidence)

While preventative and conservative treatments are the most critical components of rehabilitation for common injuries affecting the throwing athlete, concomitant medical management is indicated for certain conditions. The following medical recommendations should be considered:

NSAID & Corticosteroid Injection: These pharmacotherapies are utilized mainly in the initial periods of shoulder pathology in order to decrease pain and inflammation. (Meister 2000, Wilk 2009) The use of NSAIDs is recommended initially in combination with a physical rehabilitation prescription and thermal agents. (Meister 2000) If the athlete does not respond well to this combination of treatment then an intra-articular corticosteroid injection may be considered alongside continued therapy. Corticosteroids have been shown to be effective for short-term pain reduction for sub-acromial impingement and rotator cuff tendonitis but demonstrate poor long-term pain reduction and continued function. (Gaujoux/Cochrane 2009) It should be noted that corticosteroid injections have been known to cause adverse events such as transient pain after injection (10.7%) and skin alterations (4.0%) in addition to deleterious connective tissue effects with repeated use. (Gaujoux/Cochrane 2009) Historically, corticosteroid injections may be selected over NSAID use based upon time of season and demand of the player to perform. Therapeutic consideration of the involved tissues should lead treatment and decisions of return to play as ROM and strength are properly restored.

Imaging Concerns: Failure to demonstrate marked progress by 3 months or return to asymptomatic competition by 6 months necessitates imaging if not already obtained. Additionally, if suspicion of a more notable dysfunction or mechanical abnormality presents then clear imaging is warranted. (Meister 2000)

• In younger throwing athletes, especially pitchers ages 13-16, radiographic images may be useful to rule out a stress fracture to the proximal humeral epiphysis. Termed “Little Leaguer’s” Syndrome, this pathology may present with lateral shoulder pain usually only with hard throwing motions but may progress to include a dull pain at rest. (Meister 2000) Adequate rest from sport followed by progressive rotator cuff strengthening and a return-to-throwing program has demonstrated good outcomes for this condition.
• The radiographic evidence of humeral torsion (retrotorsion) in the dominant arm of the throwing athlete is a normal and benign finding regardless of age, gender, or sport. Such presence has actually demonstrated advantageous mechanical efficiency and may account for partial contralateral limb rotational measurement differences. (Whiteley 2009)
• Imaging may be useful to detect osseous changes or osteophyte formation, especially in the older throwing athlete due to repetitive trauma. This condition typically responds well to supervised rehabilitation but may require surgical excision if conservative treatment proves ineffective (see Internal Impingement). (Wilk 2009)

Imaging is also used to detect type and severity of other conditions such as SLAP lesions, Rotator Cuff lesions, and Rotator Cuff Tears.

SLAP Lesions: Of the four main categories of SLAP lesions, throwing athletes typically present with a Type II tear which includes a full or partial detachment of the biceps brachii tendon from the superior labral attachment in addition to labrum involvement. This injury results from repeated tensile and torsion forces from external rotation in the late cocking phase as well as the eccentric biceps brachii contraction through deceleration. Type II & IV SLAP tears often do not respond well to physical therapy or corticosteroid injection. Arthroscopic debridement and reattachment via suture is the preferred method of repair with successful outcomes and return to prior-level competition ranging from 70-87% for throwing athletes and greater than 90% success for the general population. (Wilk 2005, Dodson 2009) A supervised physical rehabilitation plan is critical for full recovery following surgical SLAP repair. (Click here for additional SLAP Lesion information)

Rotator Cuff Lesions: Injury to the rotator cuff muscles or the bicipital tendon may be due to primary or secondary impingement of the subacromial structures. Although primary impingement is rare in throwing athletes, both conditions typically respond well to conservative therapy. The most common mechanisms for secondary impingement of rotator cuff muscles is joint instability and laxity, most often involving lack of adequate scapular control. Surgical examination and debridement of the involved tissues for this condition is indicated only after failed attempts at proper conservative therapy as there is not strong evidence to support surgery for this condition. (Wilk 2009, Coghlan-Cochrane-2008)

Rotator Cuff Tears: Full or partial thickness tears of the rotator cuff should attempt no less than two bouts of physical therapy to the complete shoulder complex followed by an interval throwing program. (Wilk 2009) Corticosteroid injection may then be administered as a viable trial. Current research demonstrates very poor return to play outcomes for throwing athletes who undergo surgical intervention for full rotator cuff tears, especially baseball pitchers. Neither arthroscopic nor mini-open repairs resulted in acceptable outcomes for full-thickness repairs in baseball players with only 15% and 8% of athletes returning to play, respectively. (Wilk 2009, Mazoue 2006)
Acute Traumatic Instability: Although the majority of pathologies related to the dominant shoulder in the throwing athlete are categorized as overuse or damage resultant from repetitive trauma, the occurrence of acute traumatic instability or dislocation most often indicates surgical management. Recurrent dislocation rates have been found as high has 94.5% with young athletes who undergo nonoperative treatment versus 4% with operation. (Larrain-Cochrane-2001) Arthroscopic surgery using absorbable sutures has not been shown to be of significantly greater benefit than non-absorbable sutures. (Monteiro 2008)

Internal impingement Link here

Physical Therapy Management (current best evidence) 

Pitchers have the option of throwing from "The Stretch" or "The Wind-up" positions. It is important for them to be comfortable with both deliveries and for both to be mechanically similar during the follow-through phase.

"The Stretch" vs. "The Wind-up"

Wilk, Meister, and Andrews define 4 phases to the rehab of the throwing athlete: Acute, Intermediate, Advanced Strengthening, and Return-to-Throwing. They also discuss more specific rehab principles for common injuries to overhead throwing athletes. These rehab specifics will be illustrated in the following charts.

File:Shoulder acute phase rehab2.png

 

File:Shoulder intermediate phase rehab.png

 

File:Shoulder advanced strengthening rehab phase.png

File:Shoulder return to throwing phase.png

Throwers' Ten Exercise Program

Return To Throwing Interval Program - Developed by: Raymond "Smokey" Kubacak, PT

10 Guidelines to Follow:

1. Perform a proper full body warm-up
2. Use proper stretching techniques
3. Throw with proper mechanics
4. Throws must be made on a line (minimize arch in the trajectory of the ball)
5. Throwing needs to be pain-free before progressing to the next level
6. Take a day off between steps to ensure adequate tissue recovery
7. Use legs and trunk during throwing
8. "Crow Hop" at distances of 60 feet or greater Crow Hop Video
9. General soreness is expected - sharp pain and swelling is abnormal - contact appropriate medical professional before continuing with protocol
10. You may take a more conservative approach depending on how you feel

                                        31 day Program:

Lyman et al established the following recommendations for adolescent pitchers:

File:Pitching recommendations.png

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