What does the bracial fascia of the arm continue into as it travels distally?
The brachial fascia continues distally down the arm and becomes the antebrachial fascia in the forearm, and ultimately becomes the palmar fascia in the palm.
What is the role of the bicipital aponeurosis?
The bicipital aponeurosis reinforces the brachial and antebrachial fascia.
Where does the brachial artery ultimately enter and what does it bifurcate into in this location? With what nerve does the brachial artery enter this area with?
The brachial artery enters into the cubital fossa (along with the median nerve) and bifurcates into the radial and ulnar arteries.
Where can the somatic sensory nerves of the shoulder, arm, forearm, and hand be found?
The sensory somatic nerves of the shoulder, arm, forearm, and hand can be found in the superficial fascia of those respective regions.
What is the origin and distribution of the posterior cutaneous nerve of the forearm and the medial cutaneous nerve of the forearm.
Posterior cutaneous nerve of the forearm
Distribution: lateral head of the triceps, posterior forearm to wrist.
Medial cutaneous nerve of the forearm
Origin: C8, T1
Distribution: skin of anteromedial aspect to wrist
Where does the lateral aspect of the dorsal venous network of the hand drain into? Where does the medial aspect drain into?
Drainage sites for the lateral and media aspects of thedorsal venous network:
Lateral Aspect drains into the cephalic vein
Medial Aspect drains into the median veins of the forearm that drain into the basillic vein.
Through what vessel do the cephalic and basilic veins interconnect and where does this occur?
The cephallic and basilic vein interconnect via the median cubital vein in the cubital fossa.
Where does the cephallic vein travel and what does it eventually join?
The cephallic vein ascends laterally to the deltopectoral groove where it pierces the axillary fascia and joins the axillary vein.
Where does the basilic vein travel and what does it eventually join?
The basilic vein ascends medially along the humerus until it pierces the brachial fascia and joins the axillary vein.
How are the median nerve and brachial artery somewhat protected when the median cubital vein is used for venipuncture?
When the median cubital vein is used for venipuncture (ex: transfusion or intravenous injections), the brachial artery and median nerve are protected from being punctured by the bicipital aponeruosis which separates them from the overlying median cubital vein.
Which of the two forearm bones contributes to the wrist joint and why?
Since the large styloid process of the radius extends farther distally than the head of the ulnar, only the radius contributes to the wrist joint.
What is the most common cause of Colles fracture and what causes the resulting dinner fork deformity?
The most comon cause of Colles fracture is from trying to break one's fall by landing on the hand in the pronated position.
The resulting dinner fork deformity is from a posterior angulation proximal to the wrist due to the posterior displacement and tilt of the distal fragment of the radius.
What is the structure that is responsible for distributing forces received by the radius from the hand to the ulna and humerus?
The fibrous interosseous membrane interconnects the radius and ulna and distributes any force recieved by the radius from the hand.
Identify the structures of the distal row of the wrist (A-D).
Identify the structures of the proximal row of the wrist (E-H).
Which carpal bones articulate with the radius at the wrist joint?
The scaphoid and lunate bones articulate with the radius at the wrist joint.
Which artery is at risk when the scaphoid bone is fractured and what are clinical consequences when arterial injury occurs?
The radial artery is at risk when the scaphoid bone is fractured and if this artery is injured, then avascular necrosis of the proximal fragment of the scaphoid may occur (pathological death of bone resulting from inadequate blood supply).
Why is fracture-separation of the distal radius common in children and what is the prognosis for normal bone growth?
Fracture of the distal radius is common in children because of frequent falls in which forces are transmitted from the hand to the radius.
As long as the ephphysis is placed back into its normal position during reduction, the prognosis for normal bone growth is good.
Define brachydactyly, syndactyly, and polydactyly.
Brachydactyly - when fingers or toes are shortened.
Syndactyly- when two or more fingers or toes are fused together.
Polydactyly - the presence of extra fingers or toes (usually lacks normal muscle connection).
*Image below is respective*
What is the function of most muscles in the anteromedial forearm?
The muscles in the anteromedial forearm contribute mainly to flexion of the wrist.
What is the function of the brachioradialis and what characteristic about it allows it to do this?
The brachioradialis is a muscle of the anterolateral forearm who's function is to assist in forearm flexion mainly in the pronated or semi-pronated position.
The reason it is able to do this is because it crosses the elbow joint and attaches to the distal radius.
What is the main proximal attachment for the superficial and intermediate muscles of the anteromedial forearm?
The medial epicondyle of the humerus is the main proximal attachment for the muscles of the anteromedial forearm.
Which muscles of the forearm mainly flex the hand at the wrist?
There are THREE muscles that flex the hand at the wrist:
1) Flexor carpi radialis
2) Palmaris longus
3) Flexor carpi ulnaris (FCU)
Which muscles of the forearm mainly flex the middle phalanges of digits 2 to 5?
There are TWO muscles that flex the middle phalanges 2-5:
1) Flexor digitorym superficialis (FDS)
2) Flexor digitorum profundus (FDP)
What action of the hand are the FCR and FCU responsible for, respectively?
The Flexor carpi radialis (FCR) is responsible for flexion and abduction of the hand at the wrist.
The Flexor carpi ulnaris (FCU) is responsible for flexion and adduction of the hand at the wrist.
Which muscle of the forearm is responsible for flexion of digit 1?
The Flexor pollicis longus (FPL) is responsible for flexion of digit 1 (thumb).
Identify and explain the function/relationship of muscles A and B.
Which is deeper than the other?
These are synergistic muscles who's function is to pronate the forearm. The Pronator Quadratus (A) is the main pronator and it is deep to the Pronator Teres (B) which is only recruited for pronation when more speed and power is needed.
Which activities cause pronator syndrome and where does pain occur?
Activities that involve repeated pronation can cause pronator syndrome. It is caused by compression of the median nerve near the elbow and pain is generally felt in the proximal aspect of the anterior forearm.
From what cord does the ulnar nerve come from, and what route does the ulnar nerve take to get to the forearm?
The ulnar nerve is a continuation of the medial cord.
It travels along the medial aspect of the arm and passes posterior to the medial epicondyle of the humerus to get to the forearm.
What is the anatomical basis for avulsion of the medial epicondyle in children and which nerve is often injured?
Falling and landing on the elbow in a way that causes severe abduction of the extended elbow will result in avulsion of the medial epicondyle.
The anatomical basis (reason) for the medial epicondyle avulsing easily is because the epiphysis for the medial epicondyle may not fuse with the distal end of the humerus until up to age 20.
Since the ulnar nerve passes posterior to the medial epicondyle it is often affected by this injury.
What does the ulnar nerve innervate as it travels the forearm?
The ulnar nerve passes between the humeral and ulnar heads of the FCU (Flexor carpi ulnaris) then travels distally along the medial aspect of the FDP (Flexor digitorum profundus).
It innervates both FCU & FDP (but only a portion of the FDP).
What makes up the muscular floor of the cubital fossa? What nerve descends from this fossa and what does it innervate?
The brachialis and supinator muscles make up the muscular floor of the cubital fossa.
The median nerve descends from the cubital fossa in the midline of the forearm and innervates the superficial and intermediate muscles of the anteromedial forearm.
What does the median nerve become, and what does this resultant nerve innervate?
The median nerve becomes the anterior interosseous nerve which supplies:
1) the portion of the FDP acting on the 2nd and 3rd digits
2) the pronator quadratus
3) the FPL (Flexor pollicis longus)
What innervates the FDP?
The Flexor Digitorum Profundus has two halves that are innervated by two different nerves:
1) Median Nerve innervates the radial half, which controls 2nd and 3rd digits of the hand.
2) Ulnar Nerve innervates the ulnar half, which controls the 4th and 5th digits of the hand.
How is the palmar carpal ligament typically described?
The palmar carpal ligament is typically described as a thickening of the antebrachial fasia at the wrist.
How many tendons travel within the carpal tunnel? From what muscles do these tendons arise, and which tendon does not share the same flexor sheath as the others?
Nine tendons travel within the carpal tunnel..
...these tendons all arise from the FDS, FDP, and FPL...
...the tendon of FPL does not travel in the common flexor sheath.
The sheath of which digit is continuous with the common flexor sheath? What is the common purpose of all of these sheaths?
The sheath of the 5th digit is continuous with the common flexor sheath.
The purpose of the sheaths is to enable the tendons to slide freely over each other during finger movements.
How does dislocation of the lunate typically occur and what are the resulting symptoms?
Dislocation of the lunate typically occurs from a fall on the dorsiflexed wrist in which the lunate is pused out of its place in the floor of the carpal tunnel toward the palmar surface of the wrist.
The displaced lunate may compress the median nerve and lead to carpal tunnel syndrome. Avascular necrosis of the lunate may also occur.
How are the 4th and 5th digits affected by Dupuytren contracture and how is it treated?
Dupuytren contracture is a disease of the palmar fascia resulting in progressive shortening, thickening, and fibrosis of the palmar fascia and aponeurosis.
The 4th and 5th fingers are pulled into a continual partial flexion at the metacarpophalangeal and proximal interphalangeal joints due to the fibrous degeneration of the longitudinal bands of the palmar aponeurosis on the medial side of the hand.
This is treated by surgical excision of all fibrotic parts of the palmar fascia to free the fingers.
How do the common flexor sheath and the digital synovial sheaths determine the spread of infection from tenosynovitis?
Tenosynovitis (inflammation of the tendon and synovial sheath) can spread from its origin to other parts the hand or forearm depending on which sheath the origin is located.
Tendons in the 2nd, 3rd, and 4th fingers have their own sheaths, so unless there is a proximal rupture in one of these sheaths (due to untreated infection) then the infection will only remain confined to that particular sheath.
The Tendon in the 5th finger is continous with the common flexor sheath so tenosynovitis in the little finger may spread through the palm and carpal tunnel to the anterior forearm into the parona space.
The tendon in the 1st digit is continuous with the synovial sheath of the FPL and infection of the thumb can spread to the forearm via this route.
Where does the brachioradialis reside and what does it do?
The brachioradialis resides in the superficial muscle layer of the anterolateral forearm (the tbl says posterolateral which I'm pretty sure is wrong - fact check) and it flexes the forearm.
What muscle resides in the layer deep to the brachioradialis? Where does this muscle attach proximally/distally?
The supinator muscle resides in the anterolateral forearm (the tbl says posterolateral which I'm pretty sure is wrong - fact check), deep to the brachioradialis and its attachments are:
Proximal - lateral epicondyle of the humerus and proximal ulna
Distal - proximal radius
When does the supinator muscle supinate the forearm and when does the biceps contribute to the supination?
The supinator is the prime mover for slow, unopposed supination, especially when the forearm is extended.
The biceps becomes the prime mover during rapid and forceful supination against resistance when the forearm is flexed.
What is the main proximal attachment for the superficial muscle layer of the forearm?
The lateral epicondyle of the humerus is the main proximal attachment of the superficial muscle layer of the forearm.
At which joint does the extensor digitorum induce extension mainly, at which joint does it induce extension secondarily?
The extensor digitorum induces extension
mainly at the MCP (metacarpophalangeal aka MP) joints
secondarily at the IP (interphalangeal) joints
What is the goal of the four tendons of the digitorum, and how do these tendons achieve this goal?
The four tendons of the digitorum flatten to form extensor expansions (dorsal expansions or hoods). Each hood is a triangular tendinous aponeruosis made up of a median band and two lateral bands that wrap around the dorsal/lateral sides of both the metacarpal and proximal phalanx of each of the medial four digits and attach distally to the distal phalanx.
The goal of these extensor expansions (hoods) is to hold the extensor tendons in the midline of each of the four medial digits (pinky through index) and allow the extensor tendon to secondarily extend the middle and distal phalanges after first extending the proximal phalanges.
What causes elbow tendinitis, what are its symptoms, and when does it lead to lateral epicondylitis?
Elbow tendinitis ("tennis elbow") is caused by repetitive use of the superficial extensor muscles of the forearm.
Repeated forceful flexion and extension of the wrist, which strains the attachment of the common extensor tendon, produces inflammation of the periosteum of the lateral epicondyle (epicondylitis).
How is a long extensor tendon of the finger commonly avulsed from its distal attachment and what is the resultant deformity?
A long extensor tendon is commonly avulsed from its attachment to the phalanx when there is a sudden severe tension on the tendon as a result of hyperflexion of a digit, for example:
- when a baseball is miscaught and the finger is "jammed"
- a finger is jammed into a basepad when sliding
The resulting deformity is called mallet finger and the person cannot extend the distal interphalangeal joint.
What structure acts mainly to extend digit 5?
Digit 5 (the pinky) is mainly extended by the actions of the extensor digiti minimi which is partially detached from the extensor digitorum.
Which structure acts to mainly extend digit 2?
Digit 2 (index finger) is mainly extended by the extensor indicis.
Which muscles enable abduction of the hand? Which muscles enable adduction of the hand? Where do all of these muscles attach distally?
Abduction of the hand:
- Extensor carpi radialis longus (ECRL) - distally at 2nd metacarpal
- Extensor carpi radialis brevis (ECRB) - distally at 3rd metacarpal
Adduction of the hand:
- Extensor carpi ulnaris (ECU) - distally at 5th metacarpal
What is the result of the following synergistic actions:
1) FCR with ECRL & ECRB
2) ECU with ECRL & ECRB
3) FCR & FCU
1) FCR (Flexor carpi radialis) with ECRL & ECRB - abduction of hand
2) ECU (Extensor carpi ulnaris) with ECRL & ECRB - extension of hand
3) FCR & FCU - flexion of hand
Which muscles make up the anatomical snuff box, and name the structures that bound the anatomical snuff box:
What is the artery that runs through this snuff box?
The outcropping muscles of the thumb make up the anatomical snuff box.
a) the APL (abductor pollicis longus) tendon and EPB (extensor pollicis brevis) tendon bounds it anteriorly
b) the EPL (extensor pollicis longus) tendon bounds it posteriorly
The Radial Artery runs through the snuff box.
What are the distal attachments of the EPL, EPB, and APL, respectively? How do these attachments contribute to extension and abduction of the thumb?
Distal Attachments of:
EPL - dorsal aspect of base of distal phalanx of thumb
EPB - dorsal aspect of base of proximal phalanx of thumb
APL - base of 1st metacarpal
Abduction of thumb:
Performed by APL & APB. The APL attaches to the dorsal surface of the base of the 1st metacarpal, and contraction of the muscle alone would only extend the thumb. The APB (abductor pollicis brevis) is attached to the ventral surface of the proximal phalanx of the thumb, and contraction of this muscle alone would only flex the thumb. Contraction of both APL & APB however, results in abduction (neither extension nor flexion)
Extension of the thumb:
Performed by APL, EPL, & EPB. All of these muscles are attached to the dorsal side of the thumb so contraction of these three muscles without an opposing contraction results in a pure extension of the thumb.
Which nerve is a direct continuation of the posterior cord? Where does it travel along and what does this nerve innervate?
The radial nerve is a direct continuation of the posterior cord. It travels along the radial groove, passes anterior to the lateral epicondyle of the humerus and innervates the triceps in the posterior arm.
What fossa does the radial nerve enter? What muscle does it innervate in this fossa and what branches does it bifurcate into while in this fossa?
The radial nerve enters the cubital fossa where it innervates the brachioradialis and bifurcates into the superficial and deep branches.
Which muscles does the deep branch of the radial nerve innervate? What nerve does this branch eventually become and at what point?
The deep branch of the radial nerve innervates the superficial extensor muscles and the supinator.
After it pierces the supinator, it becomes the posterior interosseous nerve which innervates the other muscles of the deep layer.
What is the characteristic clinical sign after radial nerve injury in the radial groove of the humerus?
The characterisitic sign after a radial nerve injury in the radial nerve injury is wrist drop, which results from the inability to extend the wrist and the fingers at the MCP (metacarpophalangeal) joints. The wrist assumes a partly flexed position owing to unopposed tonus of flexor muscles and gravity.
Where do the ulnar and radial arteries terminate?
The ulnar and radial arteries terminate in the palmar arches of the hand.
What does the common interosseous artery branch from, and what does it divide into?
The short common interosseous artery branches from the proximal ulnar artery and divides into the anterior and posterior interosseous arteries.
Which arteries supply the muscles of the anteromedial forearm and which arteries supply the muscles of the posterolateral forearm?
Arteries that supply the anteromedial forearm:
Ulnar artery & anterior interosseous artery
Artery that supplies the posterolateral forearm:
posterior interosseous artery
Where does the radial artery travel and which muscles (anteromedial or posterolateral) does it supply?
The radial artery courses the boundary between the anteromedial and posterolateral muscles so it supplies BOTH.
Name the actions A through E in the image below:
Identify muscles A through D in the image below:
Also, which of these belong to the thenar muscle group?
The flexor pollicis brevis (B) and abductor pollicis brevis (C) and belong to the thenar muscle group.
Identify muscles A through E in the image below:
Also, which of these muscles belongs to the thenar muscle group?
The Flexor pollicis brevis (C), Opponens pollicis (D), and Abductor pollicis brevis (E) belong to the thenar muscle group.
What action does the abductor digiti minimi contribute to?
The abductor digiti minimi contributes to abduction of the 5th digit (pinky).
What are the innervations and functions of the thenar muscles?
Innervations the Thenar Muscles:
ALL ARE INNERVATED BY MEDIAN NERVE (C8, T1)
Function of the Thenar Muscles
1) Opponens pollicis - opposes thumb, draws 1st metacarpal medially to center of palm and rotates it medially
2) Abductor pollicis brevis - abducts thumb and helps oppose it
3) Flexor pollicis brevis - Flexes thumb
Cite the innervations of the four lumbricals. Where do they attach?
The 1st and 2nd lumbricals are innervated by the median nerve (C8, T1)
The 3rd and 4th lumbricals are innervated by the deep branch of ulnar nerve (C8, T1)
They attach proximally to the tendons of the FDP (flexor digitorum profundus)
*image is palmar view*
What muscles are located between the metacarpals and where do their tendons insert? What innervates them?
The palmar and interosseous muscles are located between the metacarpals. Their tendons insert into the extensor expansions and they are all innervated by the deep branch of the ulnar nerve (C8, T1).
What is the action of the Dorsal interossei, 1st through 4th?
The dorsal interossei abduct the 2nd-4th digits from axial line, act with lumbricals in flexing MCP joints and extending IP joints.
What is the action of the Palmar interossei, 1st through 3rd?
The 1st through 3rd palmar interossei adduct the 2nd, 4th, and 5th digit toward the axial line, assist lumbricals in flexing MCP joints and extending IP joints.
Where do the tendons of the lumbrical muscles insert, and what is the result of combined contraction of both interosseous muscles and lumbrical muscles?
The tendons of the lumbrical muscles insert into the extensor expansions.
Combined contraction of the lumbricals and interosseous muscles results in flexion of the MCP joints and extension of the IP joints of the fingers.
In the images below, which nerves innervate the purple, blue, and red areas of hand, respectively? (ignore forearm)
How does the median nerve injury near the elbow affect the ability to make a fist? How does injury of the anterior interosseous nerve alter the ability to make the "okay" sign?
When the median nerve is injured, flexion of the proximal interphalangeal joints of the 1st-3rd digits is lost (1st & 2nd lumbricals are supplied by medial nerve) and flexion of the 4th-5th digits is also weakened.
When the anterior interosseous nerve is injured, paresis (partial paralysis) of the FDP and FPL occurs, which are responsible for flexion of the interphalangeal joints of the thumb and index fingers. Person ends up making a "pinching" sign instead of an "ok" sign.
Where is the ulnar nerve most commonly injured and how is the ability to flex the wrist or make a fist altered? Where does paresthesia occur after the injury?
An ulnar nerve injury most commonly occurs where the nerve passes posterior to the medial epicondyle of the humerus when the medial part of the elbow hits a hard surface and fractures the medial epicondyle (funny bone).
Parasthesia occurs in the median part of the dorsum of the hand.
When an attempt is made to flex the wrist, the wrist is instead drawn laterally by the FCR because the FCU muscle is no longer innervated by the ulnar nerve.
When a fist is attempted, the 4th and 5th digit cannot be flexed at the distal interphalangeal joints.
What are the sensory and motor deficits after injury of the superficial or deep branches of the radial nerve?
Injury of the deep branch of the radial nerve:
Sensory deficits: none because the deep branch is entirely muscular.
Motor deficits: inability to extend the thumb and MPC joints of the other digits
Injury of the superficial branch of the radial nerve:
Sensory deficits: a coin shaped area of anesthesia occurs distal to the bases of the 1st and 2nd metacarpals. (There is considerable overlap from cutaneous branches of the median and ulnar nerves, hence minimal sensory)
Motor deficits: none.
How do cubital tunnel syndrome and Klumpe paralysis alter the ability to flex the wrist or make a fist? Where do the lesions produce paresthesia?
Cubital tunnel syndrome compresses the ulnar nerve in the cubital tunnel formed by the tendinous arch joining the humeral and ulnar heads of attachment of the FCU. Compression of the ulnar nerve interferes with the innervation of the FCU which causes the wrist to be pulled in laterally by the FCR in absence of the FCU when attempting to flex the wrist.
Klumpke paralysis results from an injury to the brachial plexus, usually when the upper limb is suddenly pulled superiorly (when a person grabs something to break a fall).
What are typical causes of carpal tunnel syndrome? Where do paresthesia, hypothesia, or anesthesia occur and which motor functions of the thumb are lost or weakened?
Causes of carpal tunnel syndrome:
1) anything that reduces the size of the carpal tunnel
2) anything that increases the size of some of the nine structures within the carpal tunnel (inflammation, fluid retention, infection, excessive exercise of the fingers)
Paresthesia (tingling), hypoesthesia (diminished sensation), or anesthesia (absence of sensation) occurs in the lateral three and a half digits.
Inability to oppose the thumb as a result of weakness of the APB and Opponens pollicis muscles.
What does the ulnar artery continue as in the palm, and what structure does it supply?
In the palm, the ulnar artery continues as the superficial palmer arch and it supplies the deep palmar arch, which is a continuation of the radial artery.
What gives rise to the arterial branch that generates digital arteries of the thumb?
The radial artery gives rise to the branch that generates the digital arteries of the thumb.
Where is the best place to stop bleeding after laceration of the palmar arches?
Since the palmar arch has numerous communications in the forearm and hand from which it can get blood flow, it is necessary to compress the brachial artery and its branches proximal to the elbow.
What causes Raynaud syndrome and if it becomes a chronic condition, how is it treated?
Raynaud syndrome is idiopathic, meaning the cause is unknown. It is characterized by bilarteral attacks of ischemia of the digits marked by cyanosis and often accompanied by paresthesia and pain.
Raynaud syndrome can be treated by a cervicodorsal presynaptic symathectomy (excision of a segment of a sympathetic nerve) to dilate the digital arteries.