Shoulder Anatomy, Injuries, Evaluation, Rehabilitation

Presented as a service to our readers by:

Texas Christian University , Athletic Training, Sports Medicine

T.Ross Bailey, M.Ed, ATC, LAT, Associate Athletic Director
Dr. Bert Franks - Team Physician, Primary Care
Dr. Joseph Milne - Orthopedist
Dr. Steve Brotherton - Orthopedist

 

These bones together make up 6 basic articulations or joints

1. Coraco clavicular (not a true joint articulation)
2. Sterno clavicular
3. Acromio clavicular
4. Gleno humeral
5. Scapulo thoracic
6. Sub Acromial space (not a true joint)

Functional stability is almost completely dependent upon the synergism of the ligaments and musculotendinous units. The shoulder is very unstable from a bony standpoint. The only true attachment to the thorax is the junction of the clavicle with the sternum.

15 Muscles move and stabilize the scapula. 9 Muscles provide for Glenohumeral motion and 6 support the scapula on the thorax.

The combinations of these muscles and joints allow for maximal rotation with minimal rotational stress on the proximal fixation point. [ The s\c joint ]

The clavicle [collar bone] is a long slender "s" shaped bone. The curvature is approximately 2/3 convex on the proximal end and 1/3 concave on the distal end. It is stabilized by the trapezius, deltoid, and subclavian muscles. The clavicle holds the scapula [shoulder blade] in the proper degree or angle of abduction (30 degrees) and external rotation. This slight movement of the scapula allows the Gleno humeral joint to function at its maximal level. This forward angle of the scapula is referred to as the plane of the scapula ( P.O.S. ). The plane can be located by placing the practitioners hand and ulnar plane into the superior spine of the scapula along the body of the supraspinatus muscle, the angle formed by the hand and arm of the practitioner that will be approximately 30 degrees forward indicates the plane of the scapula.

This plane is where the rotator cuff muscles are aligned and not overlapping or twisted around each other and thus is the most efficient positioning of the shoulder. The forward angle of the glenoid is also one of the reasons that more GH dislocations are seen anteriorly than posteriorly. Patients with pain have muscular dysfunction which alters their kinematics.  Thus it is important to watch them move their arms overhead and to observe the plane of motion as well as the synergy of function.

In the movement of abduction, if the scapula were firmly attached to the thorax, abduction with the humerus held in internal rotation would be possible to only 60 degrees before the surgical neck and the greater tuberosity of the humerus would become compressed against the underside of the acromion process. [ On the scapula ] External rotation of the humerus allows for 120 degrees of abduction because the tuberosity is rotated out of the way. Adding 30 degrees of scapula rotation adds the final 30 degrees of full abduction to a complete 180 degrees. The scapula follows the curvature on the outside of the ribs and thus is not truly engaged in the movement of abduction even though it must be referred to as such. The ratio of glenohumeral movement to scapulothoracic movement is 2:1. While this is the "standard", the GH/Scapular movement is not always consistent and the ratios may be as high as 12:1 depending upon the position if the shoulder, elbow, and wrist. The clavicular strut system allows for 60 degrees of scapular elevation. This movement is broken down into approximately 20 deg. at the A/C with 40 deg. at the S/C. Rotation is also required of the clavicle to produce elevation at the distal end.

The clavicle allows for abduction of the GH joint because of its "s" shape. The clavicle rotates 50 degrees when the shoulder is fully abducted. Loss of motion in the clavicle at either the a\c or s\c joints affects abduction of the GH joint. 60 % of the clavicular movement occurs at the distal end. This is important to remember when dealing with the patient or athlete with an injury to any of these joints.

The humerus is the long bone of the upper arm that articulates at the proximal head with the glenoid fossa to form the glenohumeral joint and at its distal end with the radius and ulna to form the elbow joint.

While the GH joint is a ball and socket joint much like the acetabular joint, it is much more mobile and less stable. This mobility and instability is due to the flat glenoid fossa, the large round head of the humerus, and the relative laxity of the joint capsule.

The size of the glenoid is roughly that of a silver dollar. It affords the humerus 10 mm of multi axial movement. (4mm anterior, 6 mm posterior) If the positions of the shoulder were broken down into increments of movement, there would be 16,000 positions. The glenoid fossa is deepened somewhat by the fibrocartilaginous rim that surrounds it called the glenoid labrum. The labrum also serves as an attachment site for the glenohumeral ligaments.

The joint capsule [ tendons, ligaments, and connective tissues] of the GH joint is 2 times as large as is the head of the humerus. The capsule originates from the labrum and its surrounding bone and attaches to the shaft of the humerus. It is reinforced by the tendons of the rotator cuff in the anterior, posterior and superior aspects.

The anterior capsular mechanism is comprised of 4 interrelated structures;

1. Subscapularis tendon
2. Labrum
3. Anterior capsular ligaments = coracohumeral & glenohumeral ligaments and the superior, middle, and anterior inferior glenohumeral ligaments ( Z shaped across the anterior shoulder capsule )
4. The anterior inferior glenohumeral ligament is the most important ligament in the shoulder. The gross and microscopic structure of the A.I.G.H.L. complex reveals a distinct histological and functional arrangement that appears to provide support of the abducted humeral head in both internal and external rotation. The I.G.H.L. is the main static stabilizer to both anterior and posterior motion.
5. Anterior synovial pouches and bursae. The sub deltoid bursae is the largest bursae in the body.

The ligaments are likened to pleated horizontal folds in a fan shaped arrangement. An opening may exist between the superior and middle ligaments. This opening may be covered by a thin capsular layer.

The superior capsular ligament is damaged by external rotation and mid abduction. (ie: reaching into the back seat of a car)

The capsule is lined with synovial tissue that may or may not come down to include the biceps groove and the biceps tendon. The bursae that are the most prevalent are the; pre deltoid bursae, the biceps tendon bursae, and the subacromial bursae. These three areas are the sites of the usual irritation that the practitioner sees in the shoulder.

Overall stability of the shoulder complex is dependent upon the subscapularis muscle and tendon, the Glenohumeral ligaments, the labrum, the depth of the glenoid fossa and the shape of the articular surfaces.

Females are predisposed to increased GH movement or laxity. If they have bad mechanics the problem magnifies. The worst age for shoulder instability is approximately 13-14 years of age when rapid growth patterns are developing and the neuro-musculotendinous system is not yet fully developed.

Acromioclavicular joint

Sternoclavicular joint

This joint is the junction of the clavicle with the sternum and is classified as a saddle joint. It has very little motion except for approx. 25 degrees of clavicular rotation and 40 deg. of elevation. This joint serves as the only true bony connection for the shoulder to the thorax. Thus this complete structure is called the clavicular strut and functions much like the front suspension of a car. The joint is supported by the sternoclavicular and costoclavicular ligaments.

This is not a joint that is frequently injured in the athletic setting. However, with more athletes playing on artificial surfaces, this injury has become more prevalent. The most frequent etiology is to have another person fall on the point of the shoulder while the body is perpendicular to the surface with the opposite shoulder fixed into the playing surface. When the axial load on the clavicle is aligned correctly, the force is transmitted through the clavicle and the S/C joint is disrupted. This injury in adolescents might result in a fractured clavicle instead of a separated S/C joint.  Anterior dislocations are the most common and my also occur atraumatically. Posterior dislocations while less common require more kinetic force to occur and thus are associated with higher degrees of associated tissue trauma. These can be associated with soft tissue structures located posterior to the S/C joint such as the esophagus, jugular vein and carotid artery.  

Rotator cuff muscles

The rotator cuff is an interactive coupling of muscular components and a tendinous envelope with neuromuscular and visco elastic properties. The rotator cuff muscles stabilize the glenohumeral joint and aid in abduction and rotation of the GH joint. These muscles are:

1. Supraspinatus
2. Infraspinatus
3. Teres minor
4. Subscapularis (The long head of the biceps is considered by some to be a pseudo rotator cuff muscle.)

The primary functions of the cuff are:

• anterior - posterior stability
• internal - external rotation both eccentrically and concentrically
• elevation, depression
• protraction
• retraction
• joint translation

The cuff muscles are the fine tuners or stabilizers of the GH joint. They also maintain the joint contact areas. The latissimus dorsi, deltoid, and the pectoralis major are the more powerful rotators, abductors and adductors. The rotator cuff muscles lie deep within the shoulder musculature but they can be palpated with careful knowledge of their locations and actions. Only the subscapularis which lies on the anterior portion of the scapula can not be palpated. If the arm is abducted to 110 and externally rotated, the edge of the subscapularis can be felt along the border
of the scapula under the axilla.

The posterior cuff muscles spell S.I.T. Because of their locations.

[ Supraspinatus, infraspinatus, and teres minor ] The supraspinatus initiates abduction until the shoulder reaches 30-60 degrees of abduction. Then the deltoid takes over. However, if the deltoid was to work alone, it would only shrug the humerus.

Torn Pectoralis Muscle on MRI scan

The internal rotators are more powerful and longer than the external rotators. However, the anterior group is also slower in action than are the posterior muscles.

If the shoulder were positioned in neutral, with 45° of abduction, and the strength of the adductors is set at 100 %, the abductors are 50% as strong, the internal rotators are 45% and the external rotators are 30%. The external rotators are 70% as strong as the internal rotators. The ratio of adduction to abduction is 2:1.

The muscles of the shoulder girdle are among the largest and strongest muscles in the body. However, because of their complexity, they should always be examined bilaterally for symmetry. They have to function both concentrically and eccentrically at very rapid speeds, because of this, they are easily weakened and can become dysfunctional quite rapidly. The mobility of the shoulder is instantaneous dependent upon the muscle function and arthokinematics of the clavicular strut.

Movements of the Shoulder

Flexion

Extension

Abduction

Phase One:

0-60° - Very dependent upon the arthrokinematics The supraspinatus, upper trapezius and deltoid work together to help bring the humerus outward and upward. The scapula upwardly protracts and the clavicle externally rotates.

Phase Two:

60-120° - The clavicle elevates to the extreme, the capsule tightens superiorly, then to the middle, and finally interiorly as the humerus is abducted. The cuff is maximally active while the serratus is functioning isometrically. The teres major muscle is the most active when the arm is in abduction and is being used overhead for extended periods of time.

Phase Three:

120-160° - The functional range of motion for most (180 max) athletes is 70-110°. The rotator cuff becomes inactive at 160. The A/C joint is also restricted in the extremes of abduction.

Adduction

External Rotation

Internal Rotation

Scapular elevation ( Scaption ) shoulder shrugs

• trapezius [ spinal accessory nerve ]
• levator scapula [ dorsal scapular nerve c5 ]
• rhomboid major
• rhomboid minor

Retraction [ position of attention ]

• rhomboids
• trapezius

Protraction [ reaching ]

• serratus anterior [ long thoracic nerve c5 ]

The synergy of the shoulder motions should be integrated and harmonious with associated functions. Any dysfunction, will alter the smoothness of the muscular synergy.

Reflex Testing

• C5 - biceps reflex
• C6 - brachioradialis
• C7 - triceps reflex

Dermatomes

• C4 - trapezius
• C5 - lateral arm (Axillary Nerve)
• C6 - lateral forearm, thumb, index, and half of middle finger (sensory branches of musculocutaneous nerve)
• C7 - middle finger
• C8 - ring and little finger, medial forearm
• T1 - medial arm
• T2 - axilla
• T3 - axilla to nipple
• T5 - nipple to pectoralis major - inferior crease

Shoulder injuries

Injuries to the shoulder complex occur as the result of varied etiologies. These injuries have always been thought of as being acute or chronic in nature. However, it is becoming more apparent that some macrotrauma may be the result of microtrauma.

The acute, trauma related injuries of the shoulder are often easier to assess than are the microtrauma - chronic cases that are the result of long term dysfunction, which can be related to myofascial trigger points and or from poor kinematics. Dysfunction is defined as the altered state in the mechanism of the neuromuscular system)

The specific sport demands on the shoulder complex vary from sport to sport. The arthrokinematics of the shoulder are similar for all throwing sports. The loads imposed on the shoulder offer a diverse combination of open and closed chain loads.

Some examples of varying sport demands on the shoulder include:

• defensively - breaking the fall of the body or stopping and object or person
• catching an object - baseball, portions of basketball
• propelling an object - bowling, discus throw
• throwing an object - baseball, serving in tennis, javelin, etc.
• combatively - boxing, stick check in lacrosse or hockey
• skillfully - dribbling a basketball, batting, hockey, etc.
• fine motor skills - pool, darts, archery

Injuries to the shoulder are best prevented. The clinician must make sure that a variety of categories are addressed in an effort to prevent injuries.

• proper equipment protective taping, wrapping, special padding
• sport specific weight training and conditioning
• proper warm up and cool down techniques
• proper sport specific techniques
• preventing overuse syndromes
• pitch counts
• post practice or game treatment
• in season training programs
• rest schedules
• observing the concepts of gradualness and intensity

Acute Trauma - direct

1. Contusions
2. Dislocations - subluxations
3. Fractures

Males are more prone to dislocations than are females. The females have greater shoulder range of motion and flexibility which aids in their avoidance of dislocations and subluxations. Anterior / inferior dislocations are more likely to occur than are posterior dislocations. Offensive linemen in football also show an increased percentage of posterior shoulder subluxations when compared to athletes participating in sports. Current thoughts are centered around the fact that males play more violent sports, while females are involved in less ballistic types of activities. However, females do have a higher rate of multi directional instability than do males.

The recurrence of dislocations is well chronicled the approximate percentages of repeat episodes of dislocation are:

• patient under 18 years of age = 90%
• patient under 30 years of age = 65%
• patient under over 35 years of age = 20%

The older the patient, the less likely they are to re-injure the shoulder. This is due in part to the decreased level of sport activity.

Acute Trauma - indirect

1. A\C separations
2. S\C separations
3. GH dislocations
4. Subluxations
1. Bankart lesion [ involves the anterior glenoid labrum ]
2. Hill - Sachs lesion - Eroded area on the articular surface of the humeral head resulting from increased motion of the humerus caused from instability. This lesion is created by the sharp edge of the posterior glenoid rim.
3. dead arm syndrome
5. Trigger points
6. Rotator cuff tears
7. Labrum tears

 

 

 

 

Over use syndromes

Micro Trauma ( may lead to macrotrauma )

1. Impingement (the greatest compression range of motion is from 80 - 120° of abduction.)
2. Myositis
3. Tendinitis
4. Bursitis (all of the above occur simultaneously and could be considered a single combined condition)

• Overuse injury to the supraspinatus tendon and sub acromial bursae.
• Primary impingement - arm is abducted and flexed horizontally
• Secondary impingement test - arm is abducted, elbow flexed, and the arm is rotated back and forth under the acromial arch.

The dysfunction pattern of the shoulder complex is often circular in nature. The circle is ever changing and can go in either direction. The most common factors are: impingement, instability, and the resulting dysfunction of myositis with secondary sequela of rotator cuff tears.

Some clinicians feel that microtrauma is the result of failure in the eccentric muscular system. The fatigue in the antagonistic muscles in throwing athletes leads to poor arthrokinematics and improper throwing form. The history of the injury will be vague and upon further examination may reveal trigger points and myofascial dysfunction. Overuse syndromes have an etiology that is related to muscular imbalance, poor mechanics, and or associated pathology from either prior acute or chronic injuries. Microtrauma may often lead to macrotrauma. This is a direct correlation of the circular concept of dysfunction. Microtrauma of the cuff may later result in a rotator cuff tear.

Phases of throwing

The pitching motion can produce many and varied injuries to the throwing shoulder. Newer diagnostic techniques, EMG studies, and arthroscopy have helped to increase the knowledge of what happens during each phase of the throwing motion. The clinician has more research and information at their disposal to help determine where in the throwing phase a particular injury may have occurred and to which muscles or anatomical structures the injury is involved.

1. Wind up - This is a relatively slow motion phase that prepares the body posture and balance in preparation of the cocking phase. Individual to the person and the specific sport demands. This phase starts when the ball leaves the glove in baseball or when the upper body starts to move in other throwing motion sports.
2. Cocking - Early phase, the scapula is retracted, the elbow is flexed 60-800, the humerus abducted, laterally rotated, and horizontally abducted. The trunk begins a very slight forward movement related to movement of the lower extremity. Late phase, the trunk rotates forward on the throwing side and the scapula protracts, the humerus adducts and rotates to a maximum when the humerus is at 90 degrees of abduction. The ball is not moved forward during this phase.
3. Acceleration - This is a very fast, explosive, short phase. The scapula continues to protract, the humerus is horizontally adducted and medial rotation of the humerus and elbow extension occur. The body is brought forward with the arm following behind. The degrees per second of movement have been determined in the range of 5000 + dps. The muscles of the posterior cuff start firing eccentrically to check the horizontal adduction movement of the humerus. This action occurs very briefly, but it can produce very strong forces. If the body opens up too soon, the elbow trails behind and is subjected to very high forces.
4. Release - Deceleration - This phase was initially described as the release phase. New research has expanded this phase. This phase has a strong eccentric component. The deceleration forces are approximately double the acceleration forces. The majority of pain in the posterior aspect of the throwing shoulder is related to deceleration forces and the fatigue of the eccentric - antagonistic muscles that must fire to slow the accelerating arm. The exact timing of ball release varies from individual to individual and upon the pitch thrown.
5. Follow through - The body moves forward with the arm which helps to reduce the forces applied to the posterior shoulder complex. The planted opposite leg is the point of fixation to the ground and is responsible for helping maintain the body balance.

SUMMARY

• Make sure to do a good evaluation on the patient and define the problems.
• Use modalities to help control daily changes in soreness and swelling.
• For tissue extensibility, progress at the athletes pace from PROM to AAROM to AROM to RROM to functional activities progress from isometrics to eccentrics to concentrics.
• Vary the workouts using all forms of resistance training: isotonic, isokinetic, and functional activities.
• Return to activity gradually
• Work the large muscle groups first, work small mm last.
• Perform off season workouts with pre and post season evaluations.
• Always follow good stretching, warm-up, and cool down habits.
• Maintain the general level of body conditioning while in rehabilitation the shoulder.
• Give the athlete the home programs and make rehab the athletes responsibility.
• The success of shoulder surgery and outcomes depends largely on the success of the shoulder rehab outcomes.

Discharge Criteria - Return to Play

An important concept to remember is that the larger the ball, the faster the progression can be through the rehabilitation process. Smaller objects (balls) require finer motor control and thus take longer to rehabilitate.

Several factors have to be determined before an athlete can be discharged back into full activity. These are:

• Mental Readiness of the athlete
• Isokinetic Testing - the injured side should be within 10% variance of the non injured side.
• Peak Torque - strength
• Power - explosive power - repeatable
• Work - endurance
• Total work - fatigue
• Eccentric work is hard to test, but it is very important for the throwing athlete or patient.
• Proper biomechanics - arthrokinematics - scapulothoracic mechanics
• Pain free range of motion
• Pain free throwing or sport specific activities
• No impingement symptoms
• Flexibility to within normal limits
• Completion of progressive throwing or sport specific activity program
• Physician release to return to full activity

Progressive Throwing Program

Always stretch prior to throwing and ice the shoulder and elbow after throwing

Phase 1 - Week 1 - Every other day

• 5-10 minute warm-up
• Toss the ball - no wind up
• Limit distance to 30 ft.
• 15 minute max of actual throwing

Phase 2 - Week 2 - Every other day

• 5-10 minute warm-up
• Toss the ball - no wind up
• 5 minutes - 30 ft throw
• 10 minutes - 60 ft throw

Phase 3 - Week 3 - Daily

• 10 minute warm-up
• 5 minutes - 30 ft throw
• 5 minutes - 60 ft throw
• 15 minutes - lob throwing - 90 ft
• All throws continue at « speed with no windup

Phase 4 - Week 4 - Daily

• 10 minute warm-up
• 5 minutes - 60 ft throw - « speed
• 10 minutes - 90 ft lob throw
• 5 minutes - 60 ft throw - on line 3/4 speed
• 5 minute - 60 ft throw - lob throw cool down

Phase 5 - Week 5 - Daily

• 10 minute warm-up
• Windup is OK
• 5 minutes - 60 ft throw - « speed
• 10 minutes - 90 ft lob throw
• 10 minutes - 90 ft - line throw minimal lob 3/4 speed
• 5 minute - 60 ft lob throw cool down

Phase 6 - Week 6 - Daily

• 10 minute warm-up
• 10 minute - 60 ft throw - « speed
• 5 minute - 90 ft lob throw 30 pitches or position specific throws 3/4 speed
• 5 minute - 90 ft 3/4 speed throw 1
• 5 minute - 120 ft lob, 3 hop from outfield to home plate
• 5 minute - 60 ft lob cool down

Phase 7 + Weeks 7-10 - Every other day

• 10 minute warm-up
• Windup is OK
• 15 minutes - 60 ft
• 30 straight balls - « speed
• 10 curve balls - « speed
• 10 sliders - « speed
• 10 fast balls - 3/4 speed
• 10 fast balls - full speed
• Mixed pitches - no more than 50
• 5 minutes rest prior to practice or game

Fielders Progression

• 10 minute warm up
• 30 straight balls - 60 ft - « speed
• 30 straight balls - 90 ft - 3/4 speed
• 30 straight balls - 120 + ft, 2 hop from outfield to home plate
• 15 straight balls - maximum speed
• Position specific throws - no more than 50
• Stretch posterior shoulder muscles Rest 3-5 minutes prior to game or practice

Throwing specifics will vary depending upon the injury, level of rehab, and the procedures used for surgery. Pain should always be a guide and an indication of too much activity.

The information presented in this text is by no means original. It is difficult to quote all of the sources that were used to compile this information.

This page was written and is maintained by Ross Bailey, M.Ed., ATC., LAT