MSK Session 3 - Elbow and Forearm Flashcards
What is the elbow joint?
- The elbow is the joint connecting the proper arm to the forearm.
- It is marked on the upper limb by the medial and lateral epicondyles, and the olecranon process.
- Structurally, the joint is classed as a synovial joint, and functionally as a hinge joint.
Describe the articulating surfaces of the elbow.
- It consists of two separate articulations:
I. Trochlear notch of the ulna and the trochlea of the humerus
II. Head of the radius and the capitulum of the humerus
- The proximal radioulnar joint is found within same joint capsule of the elbow, but most resources consider it as a separate articulation.
Describe the movement of the elbow joint.
- The orientation of the bones forming the elbow joint produces a hinge type synovial joint, which allows for extension and flexion of the forearm:
I. Extension: Triceps brachii and anconeus
II. Flexion: Brachialis, biceps brachii, brachioradialis
- Pronation and supination do not occur at the elbow – they are produced at the nearby radioulnar joints
Discuss the stability of joint.
- Like all synovial joints, the elbow joint has a capsule enclosing the joint. This in itself is strong and fibrous, strengthening the joint.
- The joint capsule is thickened medially and laterally to form collateral ligaments, which stabilise the flexing and extending motion of the arm.
- The radial collateral ligament is found on the lateral side of the joint, extending from the lateral epicondyle, and blending with the annular ligament of the radius (a ligament from the proximal radioulnar joint).
- The ulnar collateral ligament originates from the medial epicondyle, and attaches to the coronoid process and olecranon of the ulna.
Wha is a bursa?
- A bursa is a membranous sac filled with synovial fluid.
- It acts to cushion the moving parts of a joint, preventing degenerative damage.
Which bursae in the elbow have clinical importance?
There are many bursae in the elbow, but only a few have clinical importance:
- Intratendinous – located within the tendon of the triceps brachii.
- Subtendinous – between the olecranon and the tendon of the triceps brachii, reducing friction between the two structures during extension and flexion of the arm.
- Subcutaneous – between the olecranon and the overlying connective tissue.
Describe the structure of the ulna.
- The ulna is a long bone in the forearm. It lies medially and parallel to the radius, the second of the forearm bones.
- The ulna acts as the stabilising bone, with the radius pivoting to produce movement.
- Proximally, the ulna articulates with the humerus at the elbow joint.
- Distally, the ulna articulates with the radius, forming the distal radio-ulnar joint.
Briefly outline the proximal portion of the ulna, including its important landmarks.
- The proximal end of the ulna articulates with the trochlea of the humerus. To enable movement at the elbow joint, the ulna has a specialised structure, with bony prominences for muscle attachment.
- Important landmarks of the proximal ulna are the olecranon, coronoid process, trochlear notch, radial notch and the tuberosity of ulna.
Identify and describe the important landmarks of the proximal ulna.
- Olecranon – a large projection of bone that extends proximally, forming part of trochlear notch. It can be palpated as the ‘tip’ of the elbow. The triceps brachii muscle attaches to its superior surface.
- Coronoid Process – this ridge of bone projects outwards anteriorly, forming part of the trochlear notch
- Trochlear Notch – formed by the olecranon and coronoid process. It is wrench shaped, and articulates with the trochlea of the humerus.
- Radial Notch – located on the lateral surface of the trochlear notch, this area articulates with the head of the radius.
- Tuberosity of Ulna – a roughening immediately distal of the coronoid process. It is where the brachialis muscle attaches.
Describe the shaft of the ulna.
The ulnar shaft is triangular in shape, with three borders and three surfaces. As it moves distally, it decreases in width.
The shaft of the ulna has three surfaces. Identify and describe them.
- Anterior – Site of attachment for the pronator quadratus muscle distally.
- Posterior – Site of attachment for many muscles.
- Medial – Unremarkable.
The shaft of the radius has three borders. Identify and describe them.
- Posterior – Palpable along the entire length of the forearm posteriorly
- Interosseous – Site of attachment for the interosseous membrane, which spans the distance between the two forearm bones.
- Anterior – Unremarkable.
Describe the structure of the distal portion of the ulna.
- The distal end of the ulna is much smaller in diameter than the proximal end. It is mostly unremarkable, terminating in a rounded head, with distal projection – the ulnar styloid process.
- The head articulates with the ulnar notch of the radius to form the distal radio-ulnar joint.
What is the radius?
- The radius is a long bone in the forearm.
- It lies laterally and parallel to ulna, the second of the forearm bones.
- The radius pivots around the ulna to produce movement at the proximal and distal radio-ulnar joints.
The radius articulates in four places. Identify and describe them.
- Elbow Joint – partly formed by an articulation between the head of the radius, and the capitulum of the humerus.
- Proximal Radioulnar Joint – an articulation between the radial head, and the radial notch of the ulna.
- Wrist Joint – an articulation between the distal end of the radius and the carpal bones.
- Distal Radioulnar Joint – an articulation between the ulnar notch and the head of the ulna.
The proximal end of the radius articulates in both the elbow and proximal radioulnar joints. Identify the important bony landmarks.
- Head of Radius – A disk shaped structure, with a concave articulating surface. It is thicker medially, where it takes part in the proximal radioulnar joint.
- Neck – A narrow area of bone, which lies between the radial head and radial tuberosity.
- Radial Tuberosity – A bony projection, which serves as the place of attachment of the biceps brachii muscle.
Describe the structure of the shaft of the radius.
- The radial shaft expands in diameter as it moves distally.
- Much like the ulna, it is triangular in shape, with three borders and three surfaces.
- In the middle of the lateral surface, there is a small roughening for the attachment of the pronator teres muscle.
Describe the distal region of the radius.
- In the distal region, the radial shaft expands to form a rectangular end. The lateral side projects distally as the styloid process.
- In the medial surface, there is a concavity, called the ulnar notch, which articulates with the head of ulna, forming the distal radioulnar joint.
- The distal surface of the radius has two facets, for articulation with the scaphoid and lunate carpal bones. This makes up the wrist joint.
What are the radioulnar joints?
- The radioulnar joints are two locations in which the radius and ulna articulate in the forearm:
I. Proximal radioulnar joint: This is located near the elbow, and is an articulation between the head of the radius, and the radial notch of the ulna.
II. Distal radioulnar joint: This is located near the wrist, and is an articulation between the ulnar notch of the radius, and the ulnar head.
- Both of these joints are classified as pivot joints, responsible for pronation and supination of the forearm.
Describe the movement of the proximal radioulnar joint.
- Movement is produced by the head of the radius rotating within the annular ligament.
- There are two movements possible at this joint; pronation and supination.
I. Pronation: Produced by the pronator quadratus and pronator teres.
II. Supination: Produced by the supinator and biceps brachii.
Describe the structure of the distal radioulnar joint.
- This distal radioulnar joint is located just proximally to the wrist joint. It is an articulation between the ulnar notch of the radius, and the ulnar head.
- In addition to anterior and posterior ligaments strengthening the joint, there is also a fibrocartilaginous ligament present, called the articular disk. It serves two functions:
I. Binds the radius and ulna together, and holds them together during movement at the joint.
II. Separates the distal radioulnar joint from the wrist joint.
What are three major functions of the connective tissue sheet of the interosseous membrane.
- Holds the radius and ulna together during pronation and supination of the forearm, providing addition stability.
- Acts as a site of attachment for muscles in the anterior and posterior compartments of the forearm.
- Transfers forces from the radius to the ulna.
What is the wrist joint?
The wrist joint (also known as the radiocarpal joint) is a synovial joint in the upper limb, marking the area of transition between the forearm and the hand.
What are the structures of the wrist joint?
Describe the articulating surfaces of the wrist joint.
- The wrist joint is formed by:
I. Distally – the proximal row of the carpal bones (except the pisiform).
II. Proximally – the distal end of the radius, and the articular disk.
- The ulna is not part of the wrist joint – it articulates with the radius, just proximal to the wrist joint, at the distal radioulnar joint. It is prevented from articulating with the carpal bones by a fibrocartilaginous ligament, called the articular disk, which lies over the superior surface of the ulna.
- Together, the carpal bones form a convex surface, which articulates with the concave surface of the radius and articular disk.
Describe the vascular and innervation of the wrist joint.
- The wrist joint receives blood from branches of the dorsal and palmar carpal arches, which are derived from the ulnar and radial arteries.
- Innervation to the wrist is delivered by branches of three nerves:
I. Median nerve – anterior interosseous branch.
II. Radial nerve – posterior interosseous branch.
III. Ulnar nerve – deep and dorsal branches.
The joint capsule and ligaments contribute to the stability of the wrist. Outline the role of the joint capsule in the stability of the wrist joint.
- Joint capsule: Like any synovial joint, the capsule is dual layered.
- The fibrous outer layer attaches to the radius, ulna and the proximal row of the carpal bones.
- The internal layer is comprised of a synovial membrane, secreting synovial fluid which lubricates the joint.
There are four ligaments of note in the wrist joint, one for each side of the joint. Identify the ligaments which has a role in ensuring the stability of the wrist joint.
- Palmar radiocarpal
- Dorsal radiocarpal
- Ulnar collateral
- Radial collateral
Describe the structure and function of the palmar radiocarpal.
- it is found on the palmar (anterior) side of the hand. It passes from the radius to both rows of carpal bones.
- Its function, apart from increasing stability, is to ensure that the hand follows the forearm during supination.
Describe the structure and function of the dorsal radiocarpal.
- It is found on the dorsum (posterior) side of the hand.
- It passes from the radius to both rows of carpal bones.
- It contributes to the stability of the wrist, but also ensures that the hand follows the forearm during pronation.
Describe the structure and function of the ulnar collateral.
- Runs from the ulnar styloid process to the triquetrum and pisiform.
- Works in union with the other collateral ligament to prevent excessive lateral joint displacement.
Describe the structure and function of the radial collateral.
- Runs from the radial styloid process to the scaphoid and trapezium.
- Works in union with the other collateral ligament to prevent excessive lateral joint displacement.
Describe the general movements of the wrist joint as well as the muscles involved.
- The wrist is an ellipsoid type synovial joint, allowing for movement along two axes.
- This means that flexion, extension, adduction and abduction can all occur at the wrist joint.
- All the movements of the wrist are performed by the muscles of the forearm.
I. Flexion – produced mainly by the flexor carpi ulnaris, flexor carpi radialis, with assistance from the flexor digitorum superficialis.
II. Extension – produced mainly by the extensor carpi radialis longus and brevis, and extensor carpi ulnaris, with assistance from the extensor digitorum.
III. Adduction – produced by the extensor carpi ulnaris and flexor carpi ulnaris
IV. Abduction – produced by the abductor pollicis longus, flexor carpi radialis, extensor carpi radialis longus and brevis.
Introduce the muscles of the anterior compartment of the forearm.
- There are many muscles in the forearm.
- In the anterior compartment, they are split into three categories; superficial, intermediate and deep. In general, muscles in the anterior compartment of the forearm perform flexion at the wrist and fingers, and pronation.
Describe the muscles of the superficial compartment of the forearm.
- The superficial muscles in the anterior compartment are the flexor carpi ulnaris, palmaris longus, flexor carpi radialis and pronator teres.
- They all originate from a common tendon, which arises from the medial epicondyle of the humerus.
Describe the attachments, actions and innervation of the flexor carpi ulnaris.
- Attachments: Originates from the medial epicondyle with the other superficial flexors. It also has a long origin from the ulna. It passes into the wrist, and attaches to the pisiform carpal bone.
- Actions: Flexion and adduction at the wrist.
- Innervation: Ulnar nerve.
Describe the structure, attachments, actions and innervation of the pronator teres.
- Structure:The lateral border of the pronator teres forms the medial border of the cubital fossa, an anatomical triangle located over the elbow.
- Attachments: It has two origins, one from the medial epicondyle, and the other from the coronoid process of the ulna. It attaches laterally to the mid-shaft of the radius.
- Actions: Pronation of the forearm.
- Innervation: Median nerve.
Describe the attachments, actions and innervation of the intermediate compartment.
- Attachments: It has two heads – one originates from the medial epicondyle of the humerus, the other from the radius. The muscle splits into four tendons at the wrist, which travel through the carpal tunnel, and attaches to the middle phalanges of the four fingers.
- Actions: Flexes the metacarpophalangeal joints and proximal interphalangeal joints at the 4 fingers, and flexes at the wrist.
- Innervation: Median nerve.
Describe the attachments, actions and innervation of the flexor digitorum profundus.
- Attachments: Originates from the ulna and associated interosseous membrane. At the wrist, it splits into four tendons, that pass through the carpal tunnel and attach to the distal phalanges of the four fingers.
- Actions: It is the only muscle that can flex the distal interphalangeal joints of the fingers. It also flexes at metacarpophalangeal joints and at the wrist.
- Innervation: The medial half (acts on the little and ring fingers) is innervated by the ulnar nerve. The lateral half (acts on the middle and index fingers) is innervated by the anterior interosseous branch of the median nerve.
Describe the attachments, actions and innervation of the flexor pollicis longus.
- Structure: This muscle lies laterally to the FDP.
- Attachments: Originates from the anterior surface of the radius, and surrounding interosseous membrane. Attaches to the base of the distal phalanx of the thumb.
- Actions: Flexes the interphalangeal joint and metacarpophalangeal joint of the thumb.
- Innervation: Median nerve (anterior interosseous branch).
Describe the structure, attachments, actions and innervation of the pronator quadratus.
- Structure: A square shaped muscle, found deep to the tendons of the FDP and FPL.
- Attachments: Originates from the anterior surface of the ulna, and attaches to the anterior surface of the radius.
- Actions: Pronates the forearm.
- Innervation: Median nerve (anterior interosseous branch).
There are 4 anatomical classes of bone - long, short, flat and irregular. Description of a bone fracture depends on the class of bone and the direction of the fracture line.
Describe irregular bone fractures.
- A fracture of a short, flat or irregular bone requires a description determined by its direction through the bone.
- Useful terms include - horizontal, vertical, coronal, sagittal and axial.
- Often a fracture can be seen to pass in more than one direction, in which case a more detailed description may be needed
What is a transverse fracture?
- Transverse Fracture: A fracture in which the break is across the bone, at a right angle to the long axis of the bone.
- Transverse fracture example - Tibia
The fracture passes at right angles to the shaft of the long bone
What is an oblique fracture?
- Oblique fracture: Instead of break being at right angle, it goes in oblique direction to the long axis of the bone. The fracture is confined to one plane. In other words, the bone has broken at an angle.
- Oblique fracture example - Metatarsal
The fracture passes at an angle oblique to the shaft of the long bone
What is spiral fracture?
- Spiral Fracture: This fracture is easily confused with the oblique fracture. Instead of a straight break as in oblique fracture that is only in one plane, the break in this case traverses both the planes. To understand this, you need to imagine a three dimensional view of the bone.
- Spiral fracture example - Tibia
This fracture resulted from a twisting injury. The fracture line spirals along the shaft of the long bone.
What is a comminuted fracture?
- Comminuted Fracture: If the injury results in multiple breaks in the bone, they are visible as different fragments. These fractures are called comminuted fractures.
- Comminuted fracture example – Humerus
Proximal humeral shaft fracture with bone shattering due to high force injury
What are segmental fractures?
- Segmental Fracture: The bone is fractured at two distinct levels. Reduction of this fracture is difficult and non-union common as seen in following X-ray.
- Segmental fracture example - Tibia and fibula
Segments of bone have separated from both the proximal and distal portions of the tibial and fibular shafts.
What are butterfly fractures?
- Butterfly fragment is a popular term for a wedge-shaped fragment of bone split from the main fragments
- Butterfly fragment example - Metacarpal
Comminuted fracture resulting from 2 oblique fractures forming a ‘butterfly fragment’ (shape of a butterfly wing)
What is a sagittal plane fracture?
Sagittal plane fracture example - Tibia
The fracture line passes longitudinally along the long bone shaft in the sagittal plane.
Identify the nerves of the forearm.
Describe the anatomy of the arteries of the forearm.
- In the distal region of the cubital fossa, the brachial artery bifurcates into the radial artery and the ulnar artery.
- The radial artery supplies the posterior aspect of the forearm and the ulnar artery supplies the anterior aspect.
- The two arteries anastomose in the hand, by forming two arches, the superficial palmar arch, and the deep palmar arch.
Describe the anatomy of the veins of the forearm.
Describe elbow dislocations.
- Fall onto out-stretched hand (FOOSH)
- 2nd most common dislocation
- Children and young adults
- Pain/deformity/loss of function
- Usually Posterior +/- Fractures
Describe a supracondylar fracture of the distal humerus
- FOOSH
- M=F, usually 5-7 years
- Pain/marked swelling/bruising/no function
- Neurovascular compromise – paraesthesia, radial pulse, capillary return
- Displaced/Undisplaced
Descrine the radial head/neck fractures.
- FOOSH
- Commonest elbow fracture
- Lateral pain / modest swelling / loss of range
- Occult fracture
- ‘Fat pad’ sign / ‘Sail’ sign – displaced fat looks ‘black’
Describe elbow Rheumatoid Arthritis.
- Systemic Autoimmune disease
- Commonest inflammatory arthropathy
- Synovial pannus -> joint destruction
- Symmetric Polyarthropathy with morning stiffness
- Small & large joints
In terms of swellings around the elbow, outline rheumatoid nodules.
- Commonest extra-articular manifestation of Rheumatoid Arthritis
- 2o% of RhA
- More aggressive disease
- Also fingers / forearm
- Cosmetic concerns
In terms of swellings around the elbow, outline olecranon bursitis.
- Inflammation of bursa due to trauma or friction
- ‘Student’s Elbow’
- Soft, cystic & transilluminates
- Cosmetic concerns
- Can become infected
n terms of swellings around the elbow, outline gout tophi.
- Disorder of nucleic acid metabolism leading to Hyperuricaemia
- Primary & Secondary
- Urate crystal deposition (sodium urate accumulation)
- Joints
- Recurrent attacks of Arthritis
- Soft tissues – ear, elbow and achilles tendon
Outline a scaphoid fracture.
- FOOSH
- Most frequently fractured carpal bone
- Teens and 20’s
- Tenderness in ‘anatomical snuffbox’-
- May be hard to see on initial X-Rays
I. Multiple Views
II. Delayed X-Ray & re-examination / MRI scan
- Tenuous blood supply – poor healing & avascular necrosis
- Delayed presentation
- Risk of arthritis
Describe Colles’ and Smith’s fracture.
- Colles’ Fracture – dorsal displacement and angulation, shortening
- Smith’s Fracture – palmar displacement and angulation, shortening
- FOOSH
- Pain/swelling/’Dinner fork’ deformity
- Young / old (High / low energy)
- Displaced/undisplaced
- Intra-articular / extra-articular
- Outcomes depends on accuracy of reduction
- Risk of further fracture and morbidity – osteoporosis
Describe the embryonic development of dermatomes.
- During embryonic development, nerves grow into the developing limb buds.
- As the limb bud increases in size, the nerves are ‘dragged’ along with the structures they innervate thus eventually producing the adult pattern.
- In the case of the sensory innervation of the upper limb this process may be illustrated diagrammatically as in figure A.
Outline the properties of dermatomes.
- Each dermatome is named according to the spinal nerve which provides most of its sensory innervation.
- In general, contiguous areas of skin are supplied by contiguous spinal nerves.
- There is considerable overlap between adjacent dermatomes so transection (division) of a single dorsal spinal nerve root does NOT USUALLY lead to anaesthesia of the entire dermatomal area.
- The exception to this rule concerns skin areas that abut onto an axial line. Here, as shown in figure A above, contiguous areas of skin are NOT innervated by adjacent spinal segments and there is no overlap across the axial line.
Demonstrate the anatomical distribution of the dermatomes of the upper and lower limbs.
- The upper limb is innervated by the anterior primary rami of spinal nerves originating from neural (not vertebral) levels C5 to T1.
- Together these rami form the brachial plexus and it is from the various parts of this plexus of nerves that the entire neuronal innervation of the upper limb is derived.
- The lower limb receives its motor innervation from branches of either the lumbar or sacral plexus.
- These are formed from the anterior primary rami of L2, 3, 4 and 5 and S1, 2 and 3. The anatomical arrangement of these two plexi will be described.
Utilise your anatomical knowledge to describe the motor and sensory deficits caused by spinal nerve lesions and by peripheral nerve lesions.
- A lesion of a spinal nerve root (near the spinal cord) will cause loss of sensation in the relevant dermatome and also loss of function in the relevant myotome.
- A lesion in a peripheral nerve will cause loss of sensation and muscle weakness in the distribution of the peripheral nerve.
- A carefully-obtained history and a full neurological examination of the upper limb, including testing muscular tone, and tendon reflexes, will help the clinician to determine the most likely site of the lesion.
Distinguish between intracapsular and extracapsular fractures at the hip joint
Risk of avascular necrosis with intracapsular fractures - medial circumflex femoral artery
