SHOULDER (OR GLENOHUMERAL JOINT)
Shoulder joint is a synovial joint of ball and socket variety. It is the most mobile
joint in the body.
Articular surfaces: are formed by the shallow glenoid cavity of scapula and the
large round head of the humerus. This creates a 1:4 disproportion ratio that makes
the joint to be more prone to dislocation than any other joint in the body. A
fibrocartilaginous ring called glenoid labrum is attached to the margin of the glenoid
cavity to deepen it.
Articular cartilage: The articular surfaces are covered by articular cartilage.
Fibrous Capsule: This is thick and strong but lax. It surrounds the joint.
Attachment of the Fibrous Capsule:
▪ Medially, it is attached to the margins of the glenoid cavity beyond the
glenoid labrum.
▪ Laterally, it is attached to the anatomical neck of the humerus except
inferiorly where it is attached to the surgical neck of the humerus at a finger’s
breadth below the articular margin.
▪ Superiorly, it is attached at the upper end of the intertubercular groove where
it is deficient to allow the passage of the long head of biceps brachii.
Fig. 1: Coronal Section of the shoulder joint
Ligaments:
a) Glenohumeral ligament: It comprises three bands, the superior, middle & inferior
glenohumeral ligaments which pass from the anterior part of the joint capsule to
attach on the superior and inferior aspects of the lesser tubercle and anatomical neck
of humerus respectively. They are thickenings of the glenohumeral joint capsule and
are important passive stabilizers of the joint.
❖ Superior glenohumeral ligament:
▪ runs from the superior aspect of the glenoid and coracoid process to
the superior part of the lesser tubercle of the humerus at the medial
edge of the intertubercular sulcus
▪ initially anterior then anteroinferior to the long head of the biceps
tendon
▪ stabilizes the biceps brachii tendon.
❖ Middle glenohumeral ligament:
▪ runs from the anterosuperior glenoid, arising just inferior to the
superior GHL, to the anterior aspect of the anatomic neck of the
humerus.
❖ Inferior glenohumeral ligament:
▪ sometimes referred to as the inferior glenohumeral ligament complex
▪ runs from the inferior two-thirds of the glenoid labrum and/or neck to
the inferior aspect of the anatomical humeral neck
▪ composed of three parts (anterior band, posterior band and axillary
pouch, which is the laxity between anterior and posterior bands
▪ most important of the three glenohumeral ligaments as it prevents
dislocation at extreme range of motion and is the main stabilizer of the
abducted shoulder.
❖ Spiral glenohumeral ligament:
▪ also referred to as fasciculus obliquus
▪ runs from the infraglenoid tubercle and triceps tendon to the lesser
tubercle of the humerus where it shares an insertion with the
subscapularis tendon
▪ mainly demonstrated on both anatomic dissection and MR
arthrography.
b) Coracohumeral ligament: The Coracohumeral ligament is a broad but
strong ligament which strengthens the upper part of the capsule of the shoulder joint
and is a part of rotator cuff interval. It extends from the base of the coracoid process
to the greater tubercle of humerus.
▪ arises from the lateral border of the coracoid process, and passes obliquely
downwards and laterally across the joint capsule to the front of the greater
tubercle of humerus
▪ blends with the tendon of the supraspinatus muscle and extends along the
transverse humeral ligament to cover the long head of biceps tendon
superiorly.
▪ intimately united to the capsule by its posterior and lower border, but its
anterior and upper border presents a free edge, which overlaps the capsule.
▪ has two bands, anterior and posterior, that insert to the margin of the greater
and lesser tubercles of the humerus respectively.
c) Transverse humeral ligament (the Brodie ligament): is a small broad ligament that
extends between the lesser and greater tubercles of the humerus superior to the
epiphyseal line.
▪ bridges the upper end of the intertubercular sulcus.
▪ encloses the tendon of the long head of biceps brachii and its sheath in the
bicipital groove
▪ forming a tunnel that prevents the tendon from subluxing out of the groove
during shoulder movement.
▪ The subscapularis tendon attaches to the lesser tubercle and some deep fibers
may contribute to the ligament, such that a tear of the subscapularis tendon
may uncover the roof of the bicipital groove allowing the tendon to sublux
medially.
d) Coraco-acromial ligament: is a strong triangular band, extending between the
coracoid process and the acromion.
▪ its apex is attached to the medial border of the acromion just in front of the
articular surface for the clavicle
▪ its broad base is attached to the whole length of the lateral border of the
coracoid process.
▪ It overlies the subacromial bursa and indirectly supports the head of
the humerus.
e) The coracoclavicular ligaments are strong supports between the lateral end of the
clavicle and the coracoid process of the scapula. On each side, they are sited medially
and inferior to the acromioclavicular joints. Each ligament is divided into two parts:
❖ conoid ligament:
▪ passes superomedially from the base of the coracoid to conoid tubercle
on the under surface of the clavicle
▪ an 'inverted cone' in shape
❖ trapezoid ligament:
▪ passes horizontally and laterally from the superior surface of the
coracoid to the trapezoid line on the under surface of the clavicle
▪ a flat sheet, it is stronger than the conoid ligament
The two ligaments are usually continuous posteriorly but tend to be perpendicular to
each other anteriorly. The gap anteriorly is filled by a synovial bursa.
The coracoclavicular ligaments have a vital role to play in movements of the pectoral
girdle. The conoid ligament limits anterior movement of the scapula with respect to
the clavicle. The trapezoid limits posterior movement between these two bones. Both
ligaments prevent the coracoid from overriding the lateral end of the clavicle.
Blood supply:
The shoulder joint is supplied by the anterior and posterior circumflex
humeral arteries, which are both branches of the axillary artery. Branches of
the suprascapular artery, a branch of the thyrocervical trunk, also contribute to the
supply.
Veins with similar names drain the shoulder joint and enter the subclavian vein.
Innervation:
The nerves that supply the shoulder joint include axillary, suprascapular and lateral
pectoral nerves.
Movements of the Shoulder joint:
The movements of the shoulder joint and the muscles responsible for their actions
are as follows:
1. Flexion by Pectoralis major (clavicular part), Deltoid (clavicular part),
Coracobrachialis, Biceps brachii (short head)
2. Extension by Deltoid (posterior fibers), Latissimus dorsi, Teres major, long head
of triceps brachi
3. Abduction: 0o-15° by Supraspinatus; 15-90° by Deltoid (middle fibers); Overhead
abduction by Serratus anterior and Trapezius.
4. Adduction by Pectoralis major, Latissimus dorsi and Teres major
5. Medial rotation by Subscapularis, Deltoid (anterior fibers), Pectoralis major, Teres
major and Latissimus dorsi.
6. Lateral rotation by Infraspinatus, Teres minor and Deltoid (posterior fibers)
7. Circumduction: this is the combination of all the movements and their muscles.
Stability of the shoulder joint:
The factors that provide the stability of the shoulder are as follows:
1. Musculotendinous or rotator cuff formed by the flattened tendons of Subscapularis
anteriorly, Supraspinatus superiorly and Infraspinatus and Teres minor posteriorly.
They do not support the joint inferiorly.
2. Coracoacromial arch: prevents the upward dislocation of the head of the humerus.
3. Glenoidal labrum: deepens the glenoid cavity.
4. Ligaments: reinforce the joint capsule.
5. Long head of biceps brachii: prevents the upward dislocation of the head of the
humerus. It acts as a minor humeral head depressor.
Bursae around the shoulder
1. Subacromial (subacromial-subdeltoid) bursa:
This is the largest bursa in the body. It is located inferior to the acromion and above
the tendon of supraspinatus and greater tubercle of humerus. It is continuous with
the subdeltoid bursa present beneath the deltoid muscle, hence may be clinically
referred to as subacromial-subdeltoid (SASD) bursa. It protects the supraspinatus
tendon from friction against acromion during abduction of arm. Subacromial bursitis
is a condition caused by inflammation of the bursa.
The subdeltoid bursa is located deep to the deltoid muscle and the coracoacromial
arch and extends laterally beyond the humeral attachment of the rotator cuff,
anteriorly to overlie the intertubercular groove, medially to the acromioclavicular
joint, and posteriorly over the rotator cuff. The SSB decreases friction and allows
free motion of the rotator cuff relative to the coracoacromial arch and the deltoid
muscle.
2. Subscapularis recess: This is located between the coracoid process superiorly
and the superior margin of the subscapularis tendon. It communicates with the
glenohumeral joint.
But, it does not extend as caudal as the subcoracoid bursa.
3. Subcoracoid bursa (or subcoracoid bursa of Collas): The subcoracoid bursa is
located anterior to subscapularis and below the coracoid process and extends inferior
to the conjoined tendons of coracobrachialis and short head of biceps brachii. Its
function is to reduce friction between the coracobrachialis, subscapularis and short
head of the biceps tendons, thus facilitating internal and external rotation of the
shoulder. The subcoracoid bursa does not communicate with the glenohumeral
joint under normal circumstances, but may communicate with the subacromial
bursa. As such, contrast fluid injected into the glenohumeral joint during
an arthrogram that extends into the subcoracoid bursa is abnormal, and indirectly
implies a full thickness rotator cuff tear.
4. Coracoclavicular bursa: This separates the trapezoid ligament and the
conoid ligament. The coracoclavicular ligament, as described above, serves to
connect the clavicle and the coracoid process of the scapula.
Diagram of normal bursae surrounding the shoulder joint: (1) subacromialsubdeltoid bursa, (2) subscapular recess, (3) subcoracoid bursa, (4) coracoclavicular
bursa, (5) supra-acromial bursa and (6) medial extension of subacromial-subdeltoid
bursa.
5. Supra-acromial bursa: The supra-acromial bursa is located on the superior
aspect of the acromiom and normally does not communicate with the glenohumeral
joint. Since the bursa is supra-acromial, not supraclavicular, fluid-filled masses
located over the acromioclavicular joint or distal clavicle do not correspond to supraacromial bursitis.
6. Medial extension of subacromial-subdeltoid bursa: This is the medial
extension of the subacromial-subdeltoid bursa onto the medial aspect of the joint
capsule
Arterial anastomosis around the scapula
The arteries that supply the shoulder joint form the scapular anastomosis. This is
between the branches of first part of subclavian artery and branches of third part of
axillary artery. It provides collateral circulation in case the distal part of subclavian
artery or proximal part of axillary artery is blocked.
The scapular anastomosis occurs at 2 sites, viz: around the body of scapula and over
the acromion process of the scapula.
❖ Around the body of scapula, it takes place between the:
▪ Suprascapular artery, a branch of the thyrocervical trunk from the first
part of the subclavian artery
▪ Circumflex scapular artery, a branch of the subscapular artery from the
third part of the axillary artery
▪ Deep branch of the transverse cervical artery; a branch of the
thyrocervical trunk.
❖ Over the acromion process, it takes place between the:
▪ Acromial branch of the thoracoacromial artery
▪ Acromial branch of the suprascapular artery
▪ Acromial branch of the posterior circumflex humeral artery
Clinical Aspects: If the subclavian and axillary arteries are blocked anywhere
between the 1st part of subclavian artery and 3rd part of axillary artery, the scapular
anastomosis acts as a potential pathway that provides collateral circulation between
the first part of the subclavian artery and the third part of the axillary artery, to ensure
the adequate circulation to the upper limb.
Wrist joint
This is also referred to as radio-carpal joint. It provides a stable, mobile platform on
which the hand can perform. The anatomy of the wrist joint can be described as
follows;
1) Type: ellipsoid variety of synovial joint.
2) Articular surfaces:
a) proximally, by the inferior surface of the lower end of the radius and the triangular
articular disc (ulna does not participate in the formation of wrist joint).
b) inferiorly, by the proximal surfaces of the scaphoid, lunate and triquetrum.
3) Fibrous capsule: The fibrous capsule of the wrist joint surrounds the joint cavity.
It is lined by synovial membrane and attached to the margins of the articular surfaces.
The capsule is
strengthened by palmar radiocarpal, dorsal radiocarpal, radial and ulnar collateral
ligaments.
4) Ligaments: These are as follows:
a) capsular ligament: surrounds the joint.
b) palmar radiocarpal ligament: On the palmar aspect (from radius to palmar surface
of scaphoid, lunate and triquetrum)
c) palmar ulnocarpal ligament (from ulna to palmar surface of lunate and
triquetrum).
d) dorsal radiocarpal ligament: On the dorsal aspect (from radius to dorsal surface
of scaphoid, lunate and triquetrum)
e) Ulnar collateral ligament: Medially (from styloid process of ulna to triquetrum
and pisiform).
f) Radial collateral ligament: Laterally (from styloid process of radius to scaphoid
bone). It is related to radial artery.
Movements
The wrist comprises two distinct components;
a) radiocarpal joint (including the inter-carpal joints) allowing flexion, extension,
abduction and adduction.
b) inferior radioulnar joint allowing supination and pronation.
i) Flexion (Palmar flexion): The normal range of flexion is 80 degrees. The muscles
involved include, Flexor carpi ulnaris, Flexor carpi radialis, Flexor digitorum
superficialis and Flexor digitorum profundus
ii) Extension (Dorsiflexion): The normal range of extension is 90 degrees. The
muscles responsible for extension movement include, Extensor carpi radialis longus
and brevis, Extensor carpi ulnaris, Extensors of digits (extensor digitorum, extensor
indicis and extensor digiti minimi).
iii) Adduction (ulnar deviation): Flexor carpi ulnaris and Extensor carpi ulnaris. The
range of adduction or ulnar deviation is about 35 degrees.
iv) Abduction (radial deviation): Flexor carpi radialis, Extensor carpi radialis longus
and brevis. The range of abduction is about 25 degrees.
v) The normal range of pronation and supination is 90 degrees and the patient’s
elbow must be rotated to a right angle in order to eliminate rotation at the shoulder.
Arterial supply: by the articular branches derived from the dorsal and palmar carpal
branches.
Nerve supply: anterior interosseous nerve (branch of median nerve) and posterior
interosseous nerve (branch of radial nerve).
Clinical Conditions affecting Wrist Joint
Injuries of the wrist:
1) Fractures of distal radius in adults and children
a) Colle’s fracture: fracture of distal radial epiphysis
b) Smith’s fracture: fracture of distal radial metaphysis
c) Barton’s fracture.
d) Radial styloid fracture.
e) Injuries of the carpus: any of the bones of the carpus may be injured or dislocated.
The common and important injuries are;
i) Scaphoid fracture.
ii) Lunate dislocation.
iii) Peri-lunate dislocation.
iv) Dorsal chip fracture.
a) Colle’s fracture:
This is fracture of the distal end of the radius produced by a fall on to the palm of
the outstretched hand. This injury is uncommon below the age of 50 years. After
this, it is one of the commonest fractures particularly in women, the high incidence
being related to the onset of postmenopausal osteoporosis. Fracture line about 2 to
2.5 cm proximal to the distal articular surface of radius. Distal fragment is shifted
dorsally, proximally into the shaft, angulated radially and supinated. There is always
an associated injury to the inferior radio-ulnar joint.
b) Smith’s fracture:
This is the reverse of Colle’s fracture. The distal fragment is flexed rather than
dorsiflexed. It is uncommon. It is due to a fall on the dorsum of the palmar – flexed
wrist or due to a backward fall on the outstretched hand.
c) Barton’s fracture:
This is an intra-articular fracture of the distal radius with anterior displacement of a
small fragment along with the carpus. Redisplacement is very common after closed
reduction. The fracture is best managed by open reduction and application of an Ellis
T – plate.
d) Radial styloid fracture (Chauffer’s fracture):
This injury occurs following a direct blow on wrist or occasionally following a fall
on the wrist. The fracture line is transverse extending laterally from the articular
surface of radius and the fracture is more often undisplaced.
2) Fractures in children
a) Fracture of distal radial epiphysis:
This is Colle’s fracture in children. It is due to separation of the distal radial
epiphysis resulting in a displacement similar to the Colle’s fracture.
b) Fracture of distal radial metaphysis:
This may occur at any level proximal to the epiphyseal plate. The fracture may be
of the greenstick variety or may be complete.
c) Scaphoid fracture
This is the commonest injury of the carpus. Injury occurs following a fall on an
outstretched hand, typically in young adults.
d) Lunate and peri-lunate dislocation:
The mechanism is fall on the palm of outstretched, dorsiflexed hand which displaces
the whole of carpus backwards leaving only the lunate in contact with radius called
peri-lunate dislocation. The dislocation may reduce but displaces the lunate forward
out of position causing lunate dislocation. This may be associated with fracture of
scaphoid.
e) Dorsal chip fracture:
This ligamentous or capsular avulsion of a flake of bone from the dorsal aspect of
the carpus. It results from forced palmar flexion of the wrist.
f) Articular disorders of the wrist include
i) Deformities
ii) Arthritis
iii) Miscellaneous
i) Deformities: some rare disorders are;
❖ Carpal fusions: Coalescence of two or more of the carpal bones. It is the
commonest congenital abnormality. Inherited as autosomal dominant trait and
may be bilateral and often associated with other abnormalities. Will not cause
problems and treatment is not necessary.
❖ Radial club hand: The infant is born with the wrist in marked radial
deviation. There is absence of the whole or part of the radius and usually also
the thumb or the entire first two rays of the hand. It may occur as an isolated
abnormality or as part of a generalized dysplasia.
ii) Arthritis:
❖ Pyogenic arthritis: Pyogenic arthritis of the wrist is uncommon. Infection
may be haematogenous or it may be introduced through a penetrating wound.
❖ Rheumatoid arthritis:
It commonly affects the wrist and hands and is a major cause of serious loss of
function and ugly deformities. Affected joints are swollen from synovial thickening
and movement is restricted. In the later stages, articular cartilage and the underlying
bones are eroded and the fingers tend to deviate medially – ulnar deviation.
❖ Osteoarthritis:
It is uncommon and develops as a sequel of injury. The commonest predisposing
factors are fracture of the lower end of the radius with involvement of articular
surfaces, fracture of scaphoid bone complicated by avascular necrosis of the distal
fragment, dislocation of the lunate bone, Kienbock’s disease of the lunate bone and
long-established rheumatoid arthritis. Predominant pathological change is
degeneration and wearing away of the articular cartilage lining the joint surfaces.
Patient complains of gradually increasing pain and stiffness of wrist worse on
activity. Movements are markedly limited and painful if forced at the extremes. The
skin temperature is normal.
Flexor Retinaculum
The flexor retinaculum is a thick connective tissue which forms the roof of the carpal
tunnel. It is a modification of deep fascia of the forearm on the anterior aspect of the
wrist, forming a thick fibrous band.
It is attached laterally to scaphoid and crest of trapezium and medially to pisiform
and hook of hamate. It turns the carpal arch into the carpal tunnel by bridging the
space between the medial and lateral parts of the arch.
It is said to originate on the lateral side and inserts on the medial side of the carpal
arch.
Carpal Tunnel
This is an osseofibrous tunnel formed posteriorly by the concave palmar surface of
the carpal bones and bounded anteriorly by the flexor retinaculum. The carpal tunnel
forms a narrow passageway on the anterior portion of the wrist.
It serves as the entrance to the palm for nine tendons and the median nerve.
Structures passing through the carpal tunnel include the following;
a) Median nerve
b) Four tendons of flexor digitorum superficialis muscle
c) Four tendons of flexor digitorum profundus muscle
All these flexor tendons are enclosed in a common synovial sheath, referred to as
the ulnar bursa.
d) Tendon of Flexor pollicis longus which has its own synovial sheath, named as
radial bursa.
e) Tendon of flexor carpi radialis passes through a separate canal in the lateral part
of flexor retinaculum in the groove on trapezium and not within the carpal tunnel
itself.
The structures passing above the flexor retinaculum from lateral to medial are;
a) Palmar cutaneous branch of median nerve
b) Tendon of Palmaris longus
c) Palmar cutaneous branch of ulnar nerve
d) Ulnar artery
e) Ulnar nerve
Applied Anatomy - Carpal tunnel syndrome:
This is the loss of the function of median nerve in the hand. It is caused by
compression of the median nerve in the carpal tunnel. It is the most common
mononeuropathy and its aetiology is, however, most often idiopathic.
Median nerve compression in the carpal tunnel can be caused by the following:
a) Osteoarthritis involving carpal bones.
b) Dislocation of lunate bone.
c) Tenosynovitis due to inflammation of synovial sheaths of long flexor tendons.
d) Myxedema.
e) fluid retention in pregnancy.
The characteristic clinical features present as follows;
❖ Motor loss:
▪ weakness and wasting of thenar muscles which are supplied by median
nerve. Consequently, the thumb cannot be opposed and remains
adducted (adductor pollicis is supplied by ulnar nerve) this is called
‘Ape thumb deformity’ or Ape-like hand.
▪ Index and middle fingers lag behind while making the fist due to
paralysis of 1st and 2nd lumbricals (supplied by median nerve).
❖ Sensory loss:
▪ Tingling or numbness in the skin and loss of sensations over palmar
surface of lateral three and half digits including nail and distal
phalanges on dorsum of hand that are supplied by median nerve.
▪ There is no sensory loss in the skin over thenar eminence, as it is
supplied by palmar cutaneous branch of median nerve which passes
above the flexor retinaculum.
❖ Vasomotor changes:
▪ Skin over the palmar surface of lateral three and half digits of hand feels
warmer due to arteriolar dilation, and drier due to absence of sweating.
This occurs due to loss of sympathetic innervation (postganglionic
sympathetic fibers which accompany median nerve).
▪ Pain will usually radiate to the forearm. Symptoms are often associated
with waking the patient from their sleep and being worse in the
mornings.
Clinical Issues:
Tests for Carpal Tunnel Syndrome can be performed during physical examination
as follows:
❖ Tapping the nerve in the carpal tunnel to elicit pain in median nerve
distribution. This is referred to as Tinel’s Sign
❖ Holding the wrist in flexion for 60 seconds to elicit numbness or pain in
median nerve distribution. This is called Phalen’s maneuver.
❖ Treatment of Carpal Tunnel Syndrome involves the use of a splint, holding
the wrist in dorsiflexion overnight to relieve symptoms or corticosteroid
injections into the carpal tunnel. However, surgical decompression of the
carpal tunnel may be required in severe cases.