Orthopaedic Anatomy and Approaches Flashcards
Describe the boundaries of the cubital fossa
- Proximally - imaginary line running between the medial and lateral epicondyles of the humerus
- Laterally - brachioradialis muscle
- Medially - pronator teres muscle running from medial epicondyle to lateral aspect of the radial shaft
- Roof - deep fascia
- Floor - brachialis and elbow joint capsule
List the contents of the cubital fossa from medial to lateral
- Median nerve
- Brachial artery with flanking venae comitantes
- Biceps tendon
Describe the course of the brachial artery
- Continuation of the axillary artery
- Commences at the lower border of the latissimus dorsi tendon
- Ends at the level of the radial neck by dividing into ulnar and radial arteries
List the branches of the brachial artery
- Profunda brachii (accompanying the radial nerve)
- Superior ulnar collateral artery
- The Nutrient artery (to the humerus)
- Inferior ulnar collateral artery
Describe the course of the axillary nerve
Arises from the posterior cord of the brachial plexus and winds around the surgical neck of the humerus in company with the posterior circumflex humeral vessels through the quadrangular space.
Outline how the brachial plexus is divided
- 5 Roots
- 3 Trunks
- 6 Divisions
- 3 Cords
- 5 Terminal branches
Describe the deforming forces in midshaft clavicle fractures
- SCM pulls medial fragment upward
- Trapezius moves lateral fragment upward
- Pectoralis major pulls lateral fragment medially
- Latissium dorsi pulls arm and lateral fragment downward
Outline the bounds of the Quadrangular space
- Lateral = surgical neck of humerus
- Medial = long head of triceps
- Superior = teres minor
- Inferior = teres major
Contents of the Quadrangular space
- Axillary nerve
- Posterior circumflex humeral artery
Outline the bounds of the Triangular space
- Superior = Teres minor
- Inferior = Teres major
- Lateral = Long head of triceps
Contents of the Triangular Interval
- Radial nerve
- Profunda Brachii Artery
Axillary nerve root value
C5 and C6 (Posterior Cord)
Branches of the superior trunk of the brachial plexus
- Suprascapular nerve
2. Nerve to subclavius
Long thoracic nerve root value
C5-7
What divides the axillary artery into 3 parts
Pectoralis minor muscle
Motor supply of the Axillary nerve
- Deltoid
- Teres minor
- Long head of triceps
Radial nerve root value
C5-T1 (Posterior cord)
Motor supply of the radial nerve
- Triceps brachii
- Brachioradialis
- ECRL
- Anconeus
Motor supply of PIN
All forearm extensors
Describe the path of the radial nerve proper
- Formed from the posterior cord of the brachial plexus
- Moves through the Triangular interval
- Moves along the spiral groove of the humerus in the posterior compartment of the arm
- Travels with Profunda brachii artery and pierces the lateral intermuscular septum 5cm proximal to the elbow to enter anterior compartment
- Lies anterior to the lateral epicondyle before splitting at the level of the radial head
- Divides into superficial radial nerve (sensory) and PIN (motor)
Contents of the Triangular space
Circumflex scapular artery
Bounds of the Triangular interval
- Medial = surgical neck of humerus
- Lateral = long head of triceps
- Superior = Teres major
Describe the path of the superficial radial nerve
- Runs on the lateral side of the radius beneath brachioradialis
- Enters posterior compartment proximal to the wrist
- Superficial branches run superficial to the tendons of the snuffbox to supply the dorsum of the hand
Describe the path of the Posterior Interosseous Nerve (PIN)
- Pierces the supinator 3cm distal to the radial head
- Lies in the extensor forearm compartment beneath the IO membrane to the wrist
- Supplies supinator and all forearm extensors
List the short external rotators from superior to inferior
- Piriformis
- Superior gemellus
- Obturator internus
- Inferior gemellus
- Quadratus femoris
Innervation of gluteus maximus
Inferior gluteal nerve
Origin and insertion of gluteus maximus
- O = ilium posterior to posterior gluteal line, dorsal surface of sacrum and coccyx
- I = Iliotibial tract
Origin and insertion of gluteus medius
- O = external surface of ileum
- I = lateral surface of GT
Origin and insertion of gluteus minimus
- O = external surface of ileum
- I = anterior surface of GT
What muscles does the superior gluteal nerve inervate
- Gluteus medius
- Gluteus minimus
- TFL
What muscles form the tricep of the hip
- Obturator internus
- Superior gemellus
- Inferior gemellus
What does the piriformis divide
Superior and inferior gluteal nerves and vessels
Origin of sciatic nerve
L4-S3
Describe the course of the sciatic nerve
- Originates from L4-S3
- Emerges from greater sciatic foramen below the piriformis
- Crosses posterior surface of ischium
- Descends on adductor magnus deep to the hamstrings
- Crossed by long head of biceps femoris
- Divides into tibial and common peroneal nerve
Outline the incision and dissection of the anterior (Smith-Peterson) approach
- Incision = anterior half of iliac crest and down
- Sup. dissection = window between TFL and sartorius
- Deep dissection = window between rectus femoris and gluteus medius
What structures must you be wary about in the anterior (Smith-Peterson) approach?
- Femoral nerve (medial)
- Lateral femoral cutaneous nerve (lateral)
Outline the incision and dissection of the anterolateral (Watson-Jones) approach
- Incision = 2.5cm posteroinferior to ASIS and curving over GT
- Sup. dissection = interval between TFL and gluteus medius
- Deep dissection = detach abductor mechanism
What structures must you be wary of in the anterolateral (Watson-Jones) approach?
- Femoral nerve
- Femoral artery
Outline the incision and dissection of the lateral (Hardinge) approach
- Incision = centred over GT
- Sup. dissection = through TFL to expose GT
- Deep dissection = gluteus medius and minimus taken off as a cuff
What structures are at risk during a lateral (Hardinge) approach?
- Superior gluteal nerve
- Femoral nerve
Outline the incision and dissection in the posterior (Moore and Southern) approach
- Incision = 2.5cm posterior to GT
- Sup. dissection.= vastus lateralis and gluteus maximus split
- Deep dissection = short ERs are detached
What structures are at risk during the posterior (Moore and Southern) approach?
- Sciatic nerve
- Inferior gluteal artery
What forms the posterior sacroiliac complex
- Anterior SI ligament
- Interosseous ligament
- Posterior SI ligament
- Iliolumbar ligament
Origin of the gluteal arteries
Both superior and inferior originate from internal iliac
Describe the course of the axillary artery
- Begins at the lateral border of the 1st rib as a continuation of the subclavian artery
- Ends at the inferior border of the teres major, becoming the brachial artery
Outline the branches of the axillary artery
- 1st part = superior thoracic
- 2nd part = lateral thoracic, thoracoacromial
- 3rd part = anterior and posterior circumflex humeral, subscapular
List the ligaments of the GH joint
- Glenohumeral (IGHL, MGHL, SGHL)
- Coracohumeral
- Transverse humeral
- Coraco-acromial
List the static restraints of the GH joint
- Bony anatomy
- Capsule
- Labrum (contributes 50% of glenoid depth)
List the dynamic restraints of the GH joint
- Rotator cuff
- Long head of biceps tendon
What does anterior shoulder stability rely on?
- SGHL
- MGHL
- IGHL (main)
Supraspinatus OIIA
O = supraspinatus fossa I = superior facet of GT I = suprascapular nerve (C4-6) A = initiates abduction
Infraspinatus OIIA
O = infraspinatus fossa I = middle facet of GT I = suprascapular nerve (C5/6) A = ER
Teres minor OIIA
O = middle part of lateral scapular border I = inferior facet of GT I = axillary nerve A = ER
Subscapularis OIIA
O = subscapular fossa I = lesser tubercle of humerus I = IR A = upper and lower subscapular nerves
Describe the route of the radial nerve in the arm
Formed by C5-T1 nerve roots and originates from the posterior cord of the plexus. Passes through the triangular space with profunda brachii, winds around the back of the humerus to descend in the spiral groove between the medial and lateral heads of the triceps, it pierces the intermuscular septum 8cm proximal to the lateral epicondyle, it then passes anterior to the lateral epicondyle and splits into PIN and superficial radial nerve at the level of the radial head.
Describe the route of the radial nerve in the forearm
Radial nerve splits into the superficial radial nerve which lies between brachioradialis and FPL, following the course of these muscles distally until it passes to the dorsal aspect of the wrist and gives off its terminal branches. The other branch is the PIN which passes through the supinator muscle and supplies the wrist and finger extensors of the forearm
Describe the route of the ulnar nerve in the arm
Formed from C8-T1 nerve roots and originates from the medial cord. Descends on the posteromedial aspect of the humerus, pierces the intermuscular septum 8cm proximal to the medial epicondyle to pass from anterior to posterior compartment, it passes posterior to the medial epicondyle through the cubital tunnel then exits through the ulnar and humeral head of FCU
Describe the route of the ulnar nerve in the forearm
Ulnar nerve passes from the elbow to the wrist under FCU medial to the ulnar artery and enters the palm of the hand through Guyon’s canal (between pisiform and hook of hamate) along with the deep branch of the ulnar artery
Describe the route of the median nerve in the arm
Formed from the lateral and medial cords of the brachial plexus. Descends lateral to the brachial artery then crosses to the medial side mid-humerus, it then passes through the antecubital fossa medial to the biceps tendon and brachial artery
Describe the route of the median nerve in the forearm
Exits the antecubital fossa through the humeral and ulnar heads of the pronator teres and gives off the AIN at this level which supplies FPL, pronator quadratus and radial half of FDP. The median nerve proper then continues in the forearm between FDS and FDP and gives off a palmar cutaneous branch before passing through the carpal tunnel.
What does the distal radius articulate with?
- Scaphoid
- Lunate
- Distal ulna
Describe the 3 columns of the distal forearm
- Radial column = radial styloid and scaphoid fossa
- Intermediate column = lunate fossa
- Ulnar column = TFCC and distal ulna
Outline the ossification centres of the elbow
- C = capitellum (2 years)
- R = radial head (4 years)
- I = internal epicondyle (6 years)
- T = trochlea (8 years)
- O = olecranon (10 years)
- L = lateral epicondyle (12 years)
When is the radial nerve susceptible to injury
- Trauma of middle 1/3rd of humerus
- Radial head fracture
- Compression between supinator heads
- Crutch and Saturday night palsy
When is the median nerve susceptible to injury?
- Supracondylar fracture
- Wrist laceration
- Carpal tunnel syndrome
- Pronator teres syndrome
When is the musculocutaneous nerve susceptible to injury
- Deltopectoral approach to shoulder
- Compression between coracobrachialis and biceps brachii
When is the ulnar nerve susceptible to injury?
- Medial epicondyle fracture
- Wrist laceration
- Cubital tunnel syndrome
- Guyon canal cyst
Describe Guyon’s canal borders
Fibro-osseous tunnel transmitting the ulnar nerve from the forearm to the hand. It is bordered by:
- Medial = pisiform, FCU, abductor digiti minimi
- Lateral = hook of hamate
- Roof = palmar carpal ligament
- Floor = flexor retinaculum
What is are the contents of Guyon’s canal?
- Ulnar nerve
- Ulnar artery
- Venae comitantes
- Lymphatics
Describe the borders of the cubital tunnel
- Medial = medial epicondyle of humerus
- Lateral = olecranon of ulna
- Floor = elbow joint capsule
- Roof = cubital tunnel retinaculum
List the attachments of the transverse carpal ligament
- Medial = hook of hamate and pisiform
- Lateral = scaphoid and trapezium
What is the contents of the carpal tunnel?
- 4 FDS tendons
- 4 FDP tendons
- 1 FPL tendon
- Median nerve
Muscles of the anterior compartment of the arm
- Biceps brachii
- Brachialis
- Coracobrachialis
Muscle of the posterior compartment of the arm
- Triceps brachii
- Anconeus
Biceps Brachii OIIA
- O = SH (tip of coracoid), LH (supraglenoid tubercle)
- I = radial tuberosity and bicipital aponeurosis
- I = musculocutaneous nerve
- A = supinates forearm, flexes forearm when supine
Coracobrachialis OIIA
- O = tip of coracoid
- I = middle 1/3rd of medial humerus
- I = musculocutaneous nerve
- A = flex and adducts arm
Brachialis OIIA
- O = distal 1/2 of anterior humeral surface
- I = coronoid process and ulna tuberosity
- I = musculocutaenous nerve
- A = flexes forearm in all positions
Triceps Brachii OIIA
- O = LH (infraglenoid tubercle), Lat H (posterior surface of humerus), MH (posterior surface of humerus)
- I = olecranon
- I = radial nerve
- A = extends forearm
Anconeus OIIA
- O = lateral epicondyle of humerus
- I = lateral surface of olecranon
- I = radial nerve
- A = assists extension
How is the anterior compartment of the forearm divided?
- Superficial layer
- Intermediate layer
- Deep layer
Muscles of the superficial layer of the forearm
- FCR
- FCU
- Palmaris longus
- Pronator teres
Muscles of the intermediate layer of the forearm
FDS
Muscles of the deep layer of the forearm
- FDP
- FPL
- Pronator quadratus
Pronator teres OIIA
- O = UH (coronoid), HH (medial epicondyle)
- I = lateral radial surface
- I = median nerve
- A = pronates and flexes forearm
FCR OIIA
- O = medial epicondyle
- I = base of 2nd metacarpal
- I = median nerve
- A = flexes and abducts wrist
Palmaris longus OIIA
- O = medial epicondyle
- I = distal half of flexor retinaculum
- I = median nerve
- A = flexes hand at wrist and tenses palmar aponeurosis
FCU OIIA
- O = HH (medial epicondyle), UH (olecranon)
- I - pisiform, hook of hamate, 5th met
- I = ulnar nerve
- A = flexes and adducts wrist
FDS OIIA
- O = medial epicondyle
- I = shafts of medial phalanges of medial 4 digits
- I = median nerve
- A = flexes middle phalanges at PIPs and MCPs