Five roles of the scapula have been described :

• Being a stable part of the glenohumeral articulation

• Retraction and protraction along the thoracic wall

• Elevation of the acromion

• Being a base for muscle attachment

• Serving as a link in the proximal to distal sequence energy delivery

A dysfunction in one role or a combination of dysfunction in other scapular roles puts the thrower at risk. Normal scapular kinematics are required for optimal movement of the upper limb. The glenoid must be continuously repositioned to correlate with the moving humerus to keep the glenohumeral joint stable. A poorly positioned scapula has been shown to place greater stress on the anterior capsule. The ability of the scapula to retract places the upper extremity in the "full energy reservoir" position for launch, and the ability to extend during labor is required for the scapula to follow the moving humerus providing a stable platform. Elevation of the acromion increases the subacromial space to avoid compression of the rotator cuff. A few pairs of muscular forces are needed to move the scapula through its three axes of motion. In the active scapular plane, ascending rotation has been reported to be 50, posterior tilt in a medial to lateral axis is 30, and external rotation around a vertical axis is 24. Scapular positioning in non-dominant abduction motion patterns and horizontal adduction, as well as in the tasks of reaching and maneuvering with the hands behind the back. An adaptive shift of the increased upward rotation of the scapula in the athlete throwing from above was recognized at an early age and may be a constant feedback in the professional athlete. Myers et al studied this adaptation in throwing athletes compared to a control group. The humeral lift movement in the scapular plane demonstrated a significant increase in upward rotation from 0 to 30, 60 to 90 and 120. Furthermore, the throwing athlete demonstrated a significant increase in retraction in both humeral lift 9 than at 120 in the scapular plane. There were no significant differences in anterior and posterior scapular inclination or scapula elevation and depression. However, in all trial positions there was an increase in internal rotation of the scapula in the throwing group. In a study comparing upward rotation of the scapular in high school and college baseball players, a significant decrease in movement was found in the older age group at both 90 and 120 kidnapped. College players also demonstrated greater scapular protraction when tested on hands on hips and 90 abduction with internal rotation positions. A comparison of the upward rotation of the scapula during humerus elevation in the plane of the scapula of the dominant shoulders of professional position players and professional pitchers revealed a decrease in movement in the four static test positions: rest, 60, 90 and 120. A significant difference was observed between groups in both 60 and 90.

Oyama et al,  in a three-dimensional study, investigated the scapular resting position bilaterally in three male overhand athlete groups: baseball pitchers, volleyball players, and tennis players. The dominant scapula in all groups was more internally rotated and anteriorly tilted. Tennis playershad a more protracted scapula. The investigators suggested that these changes in scapular position could be defined as normal for these populations because all subjects were asymptomatic. Decreased scapular upward rotation was not present in these subjects, and this finding could suggest that this component may be associated with the injured athlete. More often than not, the disabled overhand-throwing athlete clinically presents with a markedly asymmetrical, malpositioned scapula. This malpositioned scapula is referred to by the acronym SICK scapula : (1) scapula, (2) infera, (3) coracoid, and (4) dyskinesis. A SICK scapula is a muscular overuse fatigue syndrome that manifests clinically with three major components. First, the scapula drops or is lower when compared with the nondominant scapula. Second, the scapula

is protracted or lies farther laterally from the spine when compared with the nondominant scapula. Third, the scapula has increased abduction or a greater angle from the spine to the medial scapula border when compared with the nondominant scapula. One, any combination, or all of these components can be present at the time of examination. An athlete often presents with one or more of the following symptoms in association with a SICK scapula:

1. Pain located on the medial aspect of the coracoid

2. Pain located at the superior-medial aspect of the scapula

3. Painful subacromial space

4. Painful acromioclavicular joint

5. Thoracic outlet symptoms or radicular pain

The onset of these symptoms is usually insidious and occurs when the athlete passes a pathologic threshold. A careful medical history does not reveal a single event or rapid progression

to disability. Because of the components of a malpositioned scapula, which is located inferiorly, protected, and abducted, increased tension is placed on the coracoid by virtue of a shortened pectoralis minor tendon and conjoined tendon. With repetitive overhand motions, the restrictive nature of these shortened

tendon structures encourages tendinopathy that results in a painful medial coracoid. Pain located at the superior-medial aspect of the scapula is present in the malpositioned scapula at the insertion of the

levator scapulae, upper rhomboids, and upper trapezius. Because these scapular control muscles originate from the essentially fixed spine, they are required to function in an overtensioned pattern of pain referral into the muscle belly. Most often, the key indicator in this sequence is posterior neck pain on the dominant side. Dyskinesis of the scapula is the primary offender, and a treatment protocol should be

designed to rectify the malposition of the scapula to resolve the posterior neck symptoms. Any attempt to stretch the offended musculature will add insult to the present injury. Subacromial pain often results from the infera component of the SICK scapula, which reduces the subacromial space by essentially lowering the acromion. This reduction of space hinders the function of the rotator cuff in all phases of the overhand throw. The coinciding lack of posterior tilting of the scapula with elevation increases the impingement

symptoms.  A scapular relocation test that relieves these symptoms also increases the athlete’s ability to forward flex, which is often restricted and painful. The acromioclavicular joint becomes symptomatic as a

result of the altered kinematics of the malpositioned scapula. Because the clavicle is more rigidly secured at the sternum, stresses from the infera and from protraction and abduction of the scapula are imposed on the distal clavicle articulation. Thoracic outlet symptoms are present in a few athletes because of the pressure on the neurovascular structures by the unsupported scapula and clavicle. The challenge for the clinician is to recognize the subtle changes in the position of the scapula and the way in which those subtle changes put the glenohumeral joint at risk. The task of repositioning the scapula by stretching the contracted structures and strengthening the supporting musculature in the corrected position is paramount in the sequence of rehabilitation of the overhand-throwing athlete.

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