Anatomy Flashcards
Types of shoulder joints
-Glenohumeral (glenoid fossa, head of humerus): synovial ball and socket
=Mobility > stability
-Acromioclavicular joint
Ligaments of shoulder
-Glenohumeral: stabilise
=Medial (medial edge to lesser tubercle)
=Superior (apex of glenoid fossa to lesser tubercle)
=Inferior (lower edge to anatomical neck)
-Coracohumeral: strength upper joint capsule
=Superior band (coracoid process to common insertion with supraspinatus tendon on greater tubercle)
=Inferior band (coracoid process to lesser tubercle)
-Coracoacromial (coracoid process to acromion, prevents superior dislocation of humeral head of shoulder joint)
Muscles of the shoulder
-Rotator cuff
=Supraspinatus
=Infraspinatus
=Teres minor
=Subscapularis
-Deltoid
-Pectoralis major
-Teres major
Humerus
-Proximal articulation: glenoid fossa of scapula
-Distal articulations
=Laterally: capitulum with head of radius
=Medially: trochlea with trochlear notch of ulna
-Anatomical neck: attachment of joint capsule
-Surgical neck: inferior to head of humerus
Scapula
-Point of attachment for rotator cuff muscles
-Proximal articulation: the clavicle
-Distal articulation: the head of the humerus
Clavicle
-The clavicle is an S-shaped bone which is contoured by the many muscles which attach to it. It is also the most commonly fractured bone in the body.
-Proximal articulation: the manubrium
-Distal articulation: the acromion of the scapula
Bursae of shoulder
The shoulder joint contains a few fluid-filled sacs called synovial bursae. The function of these is to minimise friction between the articulating surfaces. The bursae located in the shoulder joint include:
-Subacromial-subdeltoid bursa: located between the joint capsule and the deltoid muscle
-Subacromial bursa: located between the joint capsule and the acromion
-Subcoracoid burse: located between the joint capsule and the coracoid process
Rotator cuff muscles
Their main function is to stabilise the shoulder joint and allow its excessive range of motion.
-Supraspinatus
-Infraspinatus
-Teres minor
-Subscapularis
Supraspinatus
-Origin: the supraspinous fossa
-Insertion: the superior facet of the greater tubercle of the humerus
-Function: abduction of the humerus
-Innervation: suprascapular nerve (C5)
-Vascular supply: suprascapular artery
Infraspinatus
-Origin: the infraspinous fossa
-Insertion: the middle facet of the greater tubercle of the humerus
-Function: external rotation of the humerus
-Innervation: suprascapular nerve (C5)
-Vascular supply: suprascapular artery, circumflex scapular artery
Subscapularis
-Origin: the subscapular fossa
-Insertion: the lesser tubercle of the humerus
-Function: internal rotation of the humerus
-Innervation: upper and lower subscapular nerve (C5/6)
-Vascular supply: subscapular artery
Teres minor
-Origin: the lateral border of the scapula
-Insertion: the inferior facet of the greater tubercle of the humerus
-Function: external rotation of the humerus
-Innervation: axillary nerve (C5)
-Vascular supply: posterior circumflex humeral artery, circumflex scapular artery
Deltoid
The deltoid is a large and triangular-shaped muscle. The deltoid muscle plays a significant role in both the range of shoulder joint movement and in preventing joint dislocation when carrying heavy objects.
-Origin: the anterior border of the clavicle, acromion and spine of the scapula
-Insertion: the deltoid tuberosity of the humerus
-Function: abduction, flexion and extension of the shoulder
-Innervation: axillary nerve
-Vascular supply: posterior circumflex humeral artery
Teres major
-Origin: the posterior aspect of the inferior angle of the scapula
-Insertion: the intertubercular sulcus of the humerus
-Function: internal rotation and adduction of the shoulder
-Innervation: lower subscapular nerve
-Vascular supply: subscapular and circumflex scapular artery
Pectoralis major
Pectoralis major is a large muscle located on the anterior chest wall that has several shoulder joint related functions. This muscle works in combination with pectoralis minor which lies underneath it.
-Origin: the clavicular head
-Insertion: the bicipital groove of the humerus
-Function: flexion, adduction and internal rotation of the humerus
-Innervation: lateral and medial pectoral nerve
-Vascular supply: pectoral branch of the thoracoacromial trunk
Latissimus dorsi
-Origin: lower thoracic vertebrae (T8-12), lumbar vertebrae, ribs 9-12, iliac crest
-Insertion: the intertubercular sulcus of humerus
-Function: extension, adduction and internal rotation of the humerus
-Innervation: thoracodorsal nerve
-Vascular supply: thoracodorsal branch of the subscapular artery
Muscles in abduction shoulder
Supraspinatus
Deltoid
Muscles in adduction shoulder
Pectoralis major
Teres major
Latissimus dorsi
Subscapularis
Muscles in internal rotation shoulder
Subscapularis
Teres major
Deltoid
Pectoralis major
Latissimus dorsi
Muscles in external rotation shoulder
Deltoid
Infraspinatus
Teres minor
Muscles in flexion shoulder
Pectoralis major
Deltoid
Brachial plexus into terminal branches
The three cords branch to form the five terminal nerve branches which supply the upper limb:
-The lateral cord gives the musculocutaneous nerve and the lateral root of the median nerve
-The posterior cord gives the axillary nerve and the radial nerve
-The medial cord gives the medial root of the median nerve and the ulnar nerve
Muscles in extension shoulder
Deltoid
Latissimus dorsi
Musculocutaneous nerve
-C5/6/7
-Lateral cord brachial plexus
-It supplies skin of lateral forearm
-The musculocutaneous nerve innervates the anterior compartment of arm (BBC):
=Biceps: flexes elbow, supinates forearm
=Brachialis: flexes elbow
=Coracobrachialis: flexes and adducts the arm at the glenohumeral joint
Clinical features of musculocutaneous nerve palsy
-Sensory loss: numbness over lateral forearm
-Motor deficit: paralysis of anterior compartment of arm with very weak elbow flexion and weak forearm supination. Absent biceps reflex.
-Deformity: wasting of the anterior compartment of the arm. The elbow usually held in extension with forearm pronated.
Axillary nerve
-C5/C6
-Posterior cord
-The axillary nerve supplies the “sergeant’s patch” of skin over the lower part of deltoid muscle.
-Motor:
=Deltoid: abducts, flexes and extends shoulder
=Teres minor: externally rotates shoulder, forms part of rotator cuff which stabilises shoulder joint
Common injuries affecting axillary nerve
-Fracture of surgical neck of humerus
-Stab wounds to posterior shoulder
-Anterior shoulder dislocation
-Pressure of crutches on armpits (“crutch palsy”)
Axillary nerve palsy
-Sensory loss: numbness over “sergeant’s patch”
-Motor deficit: paralysis of deltoid leading to very weak shoulder abduction from 15-90°; weak shoulder flexion and extension. Paralysis of teres minor leading to weak shoulder external rotation.
-Deformity: wasting of deltoid muscle, making the bones of the shoulder joint very prominent and obvious. The shoulder may appear adducted and internally rotated.
Radial nerve
-C5/C6/C7/C8/T1
-Posterior cord
-The radial nerve is responsible for the sensory supply to:
=Posterior arm and forearm
=Lateral ⅔ of dorsum of hand
=Proximal dorsal aspect of lateral 3½ fingers (thumb, index, middle and half of ring finger
-The radial nerve supplies the triceps in the posterior compartment of the arm. The triceps extends and adducts shoulder and extends elbow.
The radial nerve innervates the following muscles in the posterior compartment of the forearm:
=Brachioradialis: flexes elbow
=Anconeus: extends elbow, stabilises elbow joint
=Supinator: supinates forearm
=Extensor carpi radialis longus and brevis: extend and abduct wrist
=Extensor carpi ulnaris: extends and adducts wrist
=Extensor digitorum, extensor pollicis longus and brevis, extensor indicis and extensor digiti minimi: extend thumb and fingers at MCPJs and IPJs
=Abductor pollicis longus: abducts thumb
Radial nerve palsy
-Sensory loss: numbness of skin over posterior arm, posterior forearm and radial distribution of dorsum of hand
-Motor deficit:
paralysis of posterior compartment of arm: weak elbow extension
paralysis of posterior compartment of forearm: weak wrist extension, weak thumb extension and finger MCPJ extension
Finger IPJ extension is still possible due to intact nerve supply to the lumbrical muscles of the hand
Absent triceps and supinator reflexes
-Deformity: “Wrist drop” deformity at rest and on attempted wrist extension (Figure 2). The patient cannot extend their wrist/fingers, resulting in unopposed wrist flexion. In the classical description of a radial nerve injury, the forearm is also pronated, the fingers are flexed, and the thumb adducted. There may also be wasting of triceps and posterior compartment of forearm.
Median nerve
-C5/C6/C7/C8/T1
-Lateral and medial cords
-The median nerve does not supply any sensory innervation to the axilla or upper arm.
-In the hand, the median nerve supplies:
=Skin over thenar eminence
=Lateral ⅔ palm of hand
=Palmar aspect of lateral 3½ fingers
=Dorsal fingertips of lateral 3½ fingers (thumb, index, middle and half of ring finger)
-The median nerve supplies all muscles of anterior compartment of forearm except flexor carpi ulnaris and the medial two parts of flexor digitorum profundus:
Pronator teres and pronator quadratus: pronate forearm
Flexor carpi radialis: flexes and abducts wrist
Palmaris longus: flexes wrist and tenses palmar aponeurosis
Flexor digitorum superficialis: flexes fingers at PIPJs
Lateral two parts of flexor digitorum profundus: flex index and middle fingers at DIPJs
Flexor pollicis longus: flexes thumb at IPJ
The median nerve also supplies the intrinsic muscles of hand (LOAF muscles):
Lateral two lumbricals: flex MCPJs and extend IPJs of index and middle finger
Opponens pollicis: opposes thumb
Abductor pollicis brevis: abducts thumb
Flexor pollicis brevis: flexes thumb at MCPJ
Median nerve palsy
-Sensory loss: numbness of skin over thenar eminence and median distribution of hand. However, in carpal tunnel syndrome, sensation to the palm is usually preserved due to an intact palmar cutaneous branch.
-Motor deficit:
Paralysis of most of anterior compartment of forearm: weak forearm pronation, wrist flexion and abduction, and weak finger flexion with preservation of DIPJ flexion at ring and little fingers.
Paralysis of thenar eminence: weak pincer grip and overall grip strength, weak thumb opposition.
-Deformity: “Hand of benediction” deformity on attempted finger flexion, the patient cannot flex their index or middle fingers, resulting in unopposed extension of those two fingers (Figure 3). They cannot make a fist with all of their fingers. Wasting of anterior compartment of forearm and thenar eminence
Ulnar nerve
-C8/T1
-Medial cord
-Skin over hypothenar eminence
Medial ⅓ palm of hand
Palmar aspect of the medial 1½ fingers
Medial ⅓ dorsum of hand
Dorsal aspect of medial 1½ fingers (little finger and half of ring finger)
-The ulnar nerve innervates two muscles in the anterior compartment of the forearm:
Flexor carpi ulnaris: flexes and adducts wrist
Medial two parts of flexor digitorum profundus: flex ring and little fingers at DIPJs
The ulnar nerve innervates most of the intrinsic muscles of the hand (HILA muscles):
Hypothenar eminence: opponens digiti minimi, flexor digiti minimi brevis and abductor digiti minimi: oppose, flex and abduct little finger
Interossei: palmar interossei adduct, dorsal interossei abduct
Medial two lumbricals: flex MCPJs and extend IPJs of ring and little finger
Adductor pollicis: adducts thumb. adductor pollicis is not part of the thenar eminence and actually lies deep beneath it as a separate structure.
In addition, the superficial branch of the ulnar nerve innervates palmaris brevis.
Ulnar nerve palsy
Sensory loss: numbness over hypothenar eminence and ulnar distribution of hand
Motor deficit:
Paralysis of flexor carpi ulnaris: weak wrist flexion and adduction
Paralysis of medial two parts of flexor digitorum profundus: weak flexion of ring and little finger DIPJs
Paralysis of most of the intrinsic muscles of the hand: weak MCPJ flexion and IPJ extension of ring and little fingers, loss of finger abduction and adduction, loss of opposition of little finger
Deformity: “Claw hand” deformity at rest and on attempted finger extension: the patient cannot extend the IPJs of their ring or little fingers, resulting in fixed flexion of the IPJs and hyperextension of the MCPJs of these two fingers (Figure 4).
The clawed appearance is most pronounced when the nerve is injured at the wrist, for example by compression in Guyon’s canal, as the function of flexor digitorum profundus will be preserved. A claw hand affecting all four fingers is much less common and is usually due to a lesion of the lower part of brachial plexus, such as Klumpke’s palsy. wasting of hypothenar eminence and intrinsic muscles of hand
Inferior gluteal nerve
patient is noted to have impaired hip extension and lateral rotation. He has difficulty rising from a seat and can’t climb stairs
Common peroneal nerve
patient develops foot drop following a fibular neck fracture
Obturator nerve
patient cannot adduct his thigh following an anterior hip dislocation
Superior gluteal nerve
patient is found to have a positive Trendelenburg sign
