4. Loss of functional muscle depressors of the humeral head
5. Loss of glenohumeral fulcrum (capsular laxity or glenoid or humeral bone loss)
6. Nonunion or malunion of acromion
7. Ununited mesacromial epiphysis
Intrinsic Theories (Vascular Watershed)
The vascularity of the rotator cuff tendons has been studied at length
Most authors (Ling 1990, Lindholm 1933, Moseley 1963) have demonstrated an avascular area in distal part of the supraspinatus tendon just proximal to insertion in the greater tuberosity
Represents anastomosis of vessels derived from muscle and those derived from bone
Codman coined this area the “Critical Zone”
The contact area between the critical zone and Coracoacromial arch increases from 4.77cm2 in 45° of abduction to 7.08cm2 at 90° of abduction
Most impingement occurs at the anterior edge of the acromion
Microtrauma occurs with repetitive activities (ie. overhead sports such as throwing)
Development of myxoid degeneration and tendonopathy (cf. Archilles tendinopathy and lateral epicondylitis in this age group ie. > 40 years)
Probably a combination of both theories
Epidemiology
Common problem in middle aged and elderly patients – male > female
Increased incidence with overhead work and age > 60 years
Throwing sports are associated with rotator cuff disease
Bigliani & colleagues
140 shoulders in 71 cadavers with average age 74.4 years
Identified three types of acromion
Type 1 (flat) 17%
Type 2 (curved) 43%
Type 3 (hooked) 40%
58% had same type of acromion on each side
Incidence of tears
Full thickness tears 33%
Of which
73% in Type 3 acromion
24% in Type 2 acromion
3% in Type 1 acromion
Anatomy
1. Subscapularis
Arises from the medial 4/5 of the costal surface of the scapula, from intermuscular septa which raise bony ridges on this surface and from the concave border of the scapula up to infraglenoid tubercle
Inserts into the lesser tuberosity of the humerus and the medial lip of the intertubercular groove for 2cm below
Supplied by the Upper and Lower Subscapular Nerve (C6, C7)
Acts primarily as internal rotator of humerus and acts with other rotator cuff muscles to stabilize the shoulder
2. Supraspinatus
Arises from whole of the supraspinous fossa and upper surface of the scapular spine
Bipennate in shape
Inserts into the smooth part of upper facet of greater tuberosity
Supplied by the Suprascapular Nerve (C5, C6)
Main action is humeral head stabilizer – Humeral head compressor
Contributes to humeral head abduction with Deltoid
3. Infraspinatus
Arises from beneath deep fascia from medial 3/4 of the infraspinous fossa
Fibrous intramuscular septa allow further attachment of Multipennate fibres
Inserted into smooth area on the middle facet of the greater tuberosity
Supplied by the Suprascapular Nerve (C5, C6)
Primary action is external rotator of the humerus
Also acts with rest of the cuff in stabilizing the G-H joint
Arises from elongated oval area at axillary border of the scapula and inserts into the lower facet of the greater tuberosity
Supplied by the posterior branch of the Axillary Nerve (C5, C6)
Primary action as external rotator and adductor of the humerus
Acts with other cuff muscles to stabilize the joint
Coracoacromial arch
The Coracoacromial arch functions as an additional articular surface of the shoulder joint during abduction and forward flexion
It consists of
1. Coracoid Process
2. Acromion Process
3. Coracoacromial ligament
Subacromial bursa
large bursa lying under the coracoacromial ligament to which the upper layer is attached
The lower layer is attached to the tendon of supraspinatus
Extends beyond the lateral border of acromion with the arm by the side but rolled inwards under the acromion when arm abducted
Coracohumeral ligament
strong ligament that runs from the undersurface of the coracoid laterally across the capsule, to which it is attached at the margin of the greater tuberosity and along the transverse ligament
2 bands
One inserts into the tendinous anterior band of supraspinatus and greater tuberosity
Second inserts into the superior border of subscapularis, transverse ligament and lesser tuberosity
Superficial to shoulder capsule and overlies biceps tendon
Biceps
Long head of Biceps Tendon crosses the rotator cuff in the rotator interval between the Supraspinatus and Subscapularis muscles
It enters the intertubercular groove where it is held down by the Transverse ligament
Rotator Interval
Lies between supraspinatus and subscapularis
Within the interval lies
Coracohumeral ligament (superficial)
SGHL (deep)
Pathology
Classification
1. Impingement
Neer classifies into three broad groups
Stage I
Reversible
Oedema & Haemorrhage
< 25 years
Stage II
Irreversible change
Fibrosis & Tendonitis
25-40 years
Subdivided by Gartsmen
Stage IIA
No tear
Stage IIB
Partial thickness tears
Stage III
Chronic
Partial & Full thickness tears
> 40 years
2. Rotator cuff tears
Neer divided into three groups
Group 1
Traumatic Tears
< 5% of 340 cases
< 40 years of age and result of microtrauma from overhead sports
Group 2
Tears with dislocations
Anterior dislocation
> 40 years and in rotator interval
Multidirectional instability
Cleft tear of rotator interval
Extreme violence at any age with large cuff tear maybe associated nerve injury
Group 3
Impingement tears
> 40 years
50% no history of injury
Partial vs Full thickness
1. Partial thickness – joint side > bursal
Bursal side
Joint side
Intrasubstance
2. Full thickness
Small < 1cm
Medium 1-3cm
Large 3-5cm
Massive > 5cm
3. Cuff Arthropathy
4. Calcific Tendonitis
5. Biceps tendonitis
The first three represent spectrum of disease and often present together
History
Pain
predominant symptom of impingement
Anterior aspect of acromion and coracoacromial ligament area
Can radiate down arm into elbow, medially into chest wall or into trapezius
Pain usually associated with overhead activities (reaching into cupboard, hanging clothes, etc)
Tennis, swimming make it worse
Cannot sleep on affected shoulder
weakness
loss of motion
Examination
Tenderness
over anterolateral edge of acromion or biceps tendon (faces anteriorly at 5-10° of IR)
Movement
Painful arc from 70-120°
Impingement sign
Passively elevating the arm in plane of scapular and reinforced by internal rotation of the arm (ie. Hawkin’s + Neer’s)
Neer’s Impingement Sign
Stabilize scapular and passively abduct in plane of scapular (30° to coronal plane)
pain
Hawkin’s Impingement Sign
Forward flexion to 90° with IR
pain
Bicipital tendonitis/ subluxation
Speed’s test
Resisted elevation of supinated forearm
pain
Yerguson’s test
Resisted supination with shoulder adducted
click or pop with pain
AC joint pathology
Painful if forced cross arm adduction or IR of the extended arm
Weakness of rotator cuff muscles
Subscapularis
Gerber’s lift-off or Napoleon’s
Supraspinatus
test in abduction with thumb down & feel contraction + test power
External rotators (IS and TM)
ER in adduction
Teres minor
Hornblowers (ER at 90° abduction)
Instability
Apprehension and Jobe relocation test if instability considered
Investigations
Neer Impingement Test
HCLA into subacromial bursa makes previously positive impingement sign negative
