Simple Shoulder Ligament Assessment

SIMPLE SHOULDER

 

The ligaments of the glenohumeral joint are arranged like a clock. At 12 o’clock the long head of biceps (LHB) inserts into the labrum and glenoid, and spans out to attach on the head of the humerus (HOH) at the 1 o’clock position; at 1 o’clock the superior glenohumeral ligament (SGHL) originates and spans to the HOH at 2 o’clock; the middle glenohumeral ligament (MGHL) starts at 2 o’clock and spans to attach on the HOH at 4 o’clock. The inferior glenohumeral ligament (IGHL) has an anterior and posterior band, at roughly 4-5 and 7 o’clock respectively. In between those two bands is the axillary pouch, at the six o’clock swill, a time to grab a drink and let loose (incidentally, the axillary pouch is also loose hanging capsular tissue. It is responsible for inferior stability and acts as a hammock to wrap around the humeral head during elevation and rotation of the shoulder). This clock is accurate when looking at the right shoulder and is reversed on the left.

shoulder

Evidently, thicker capsular ligaments in the front of the shoulder are needed during the afternoon, from 12 to 5 o’clock. The more strenuous work that is required of these ligaments is to stabilize the shoulder, limiting anterior translation of the head of the humerus in various positions of arm elevation. Anterior stability is especially needed during the 90/90 position of abduction and external rotation, such as in baseball pitching and overhead sports.

Once 7 o’clock hits, it is time to wind down and chill. The posterior capsule does not have any glenohumeral ligament thickenings. Instead, the muscles of the posterior rotator cuff help out. From 7 o’clock to just passed midnight, the teres minor, infraspinatus and supraspinatus provide stability to the very thin posterior capsule of the shoulder.

 

Rotator Interval

Between noon and 2 o’clock is the time where workers grab lunch. This period is characterized by lost productivity – the Bermuda Triangle of work. In the shoulder, a similar situation occurs. The rotator interval is a triangular area in the anterior shoulder. Its borders are the supraspinatus (SST) above, subscapularis (SSC) below and coracoid process medially.

rotator interval triangle

The contents of the triangle are analogous to the lunchtime food. In the shoulder, that food is a sandwich. The two buns are the coracohumeral ligament (CHL) on top and the SGHL on the bottom. The long head of biceps tendon runs through the middle and is the meat of the sandwich. Along with the subscapularis tendon, this sandwich forms the biceps reflection pulley that is responsible for stabilizing the LHB within the rotator interval and bicipital groove. The importance of these structures are described below.

rotator interval reflection pulley sandwich

 

Shoulder Ligament Assessment

Assessment of the glenohumeral ligaments is not an exact science as variations in the shoulder joint and differences in muscle length-tension can influence and limit motion of the shoulder. To effectively evaluate the glenohumeral ligaments and capsule, the starting position is extremely important. The shoulder blade rests on the thorax in the scapular plane. As a result, the glenoid faces 30 degrees anterior to the frontal plane in its resting position. Therefore, to have all the ligaments in neutral and not on tension, the arm must be resting in the scapular plane during glenohumeral ligament assessment.

 

scapular plane

Internal Rotation in Neutral

Primary Limiter: Posterior Capsule (superior aspect)

posterior capsule

Clinical Rationale: The superior aspect of the posterior capsule and the adjacent bursa may become thickened, potentially affecting the activation of the posterior rotator cuff throughout its full range of motion. Posterosuperior capsule tightness also limits hand behind back movement. 

 

External Rotation (+/- Inferior Glide) in Neutral 

Primary Limiter: Rotator interval (SGHL and CHL also provide inferior stability in this position)

CHL and SGHL

Clinical Rationale: The rotator interval and anterior joint capsule, predominantly the CHL and MGHL, have been identified as the major ligaments affected in idiopathic frozen shoulder, leading to a loss of external rotation in neutral. The subscapularis muscle is also an anterior restraint in neutral and can limit shoulder ER in this position.

 

Internal Rotation at 45 degrees

Primary Limiter: Posterior Capsule

IR at 45

 

Clinical Rationale: Bilateral differences in internal rotation range of motion are important to note in varying degrees of arm abduction.

 

External Rotation at 45 degrees

Primary Limiter: Middle Glenohumeral Ligament (MGHL)

ER MGHL

Clinical Rationale: As mentioned above, the MGHL is implicated in idiopathic frozen shoulder and is an important anterior stabilizer of the humeral head in a midrange abducted position.

 

Internal Rotation 90 degrees

Primary Limiter: Posterior Band of IGHL

post band IGHL in IR

Clinical Rationale: Loss of glenohumeral internal rotation, also known as GIRD, has been implicated in the development of internal impingement and SLAP tears in throwing athletes. It is important to note that assessment of GIRD must include a consideration of the total arc of motion as well as possible bony changes from sporting demands throughout an athlete’s life.

 

External Rotation at 90 degrees

Primary Limiter: Anterior Band of IGHL

Anterior IGHL in ER

Clinical Rationale: Apprehension or laxity in this position is likely to result from an anterior dislocation, compromising the anterior band of the IGHL.

 

** Anatomical images taken from Physical Examination of the Shoulder (affiliate link):

 

PHYSICAL EXAMINATION OF THE SHOULDER BOOK

 

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