L11: Functional anatomy of the hand and wrist Flashcards
What forms the wrist joint?
Distal radius, triangular fibrocartilage complex (TFCC), the scaphoid and lunate
Ulna not part of wrist
What type of joint is the wrist joint?
Ellipsoid type of synovial joint
Between convex surface or carpal bones and concave surface of radius and triangular fibrocartilage
What types of movement are there at the wrist?
Two axes
Flexion and extension
Abduction (radial deviation) and adduction (ulna deviation)
Circumduction–> all four movements together- move hand in a circle
What stabilises the wrist joint?
Stabilised by ligaments
Dorsal and palmar radiocarpal ligaments
Ulnar and radial collateral ligaments
What do the radiocarpal ligaments ensure?
The hand follows the hand follows the radius during pronation and supination of the forearm
What are the main muscles responsible for flexion of the wrist?
Flexor carpi ulnaris (inserts onto pisiform, hook of hamate and base of 5th metacarpal)
Flexor carpi radialis (inserts onto base of 2nd and 3rd metacarpal)
Palmaris longus (Inserts onto palmar aponeurosis)
What other muscles assist in flexion?
Flexor digitorum superficialis (Base of middle phalanx of 4 fingers)
Flexor digitorum profundus (base of distal phalanx of four fingers)
Flexor pollicis longus (base of distal phalanx of thumb)
What are the main extensors?
Extensor carpi radialis longus (dorsal surface of 2nd metacarpal bone)
Extensor carpi radialis brevis (dorsal surface of 3rd metacarpal bone)
Extensor carpi ulnaris (Base of 5th metacarpal)
What muscles assists extension?
Extensor digitorum (Extensor hood of the 4 fingers)
Extensor indicies (extensor hood of index finger, ulnar side of extensor digitorum)
Extensor digit minimi (extensor hood of little finger)
Extensor pollicis longus (distal phalanx of thumb)
Extensor pollicis brevis (proximal phalanx of thumb)
Abductor pollicis longus (radial side of base of first metacarpal)
What muscles produce ulnar deviation (adduction)?
Flexor carpi ulnaris
Extensor carpi ulnaris
What muscles produce radial deviation (abduction)?
Flexor carpi radialis
Extensor carpi radialis longus and brevis
What is the innervation to the wrist?
3 nerves that supply the hand from the radial, ulnar and median nerves
How many bones are there in the hand?
8 carpal
5 metacarpal
14 phalanges
What are the 8 carpal bones? How are they arranaged?
'Straight Line To Pinky, Here Comes The Thumb!' Proximal row -Scaphoid -Lunate -Triquetrum -Pisiform Distal row -Hamate -Capitate -Trapezoid -Trapezium
Which bones articulate with the radius?
Scaphoid and lunate
Which bones articulate with the metacarpal bones?
Distal row
Hamate, Capitate, Trapezoid and Trapezium
What is significant about the hamate bone?
Hamate has a hook on it
Forms ulna border of carpal tunnel
Radial border of Guyons canal
Attachment site for flexor retinaculum and tendon of flexor ulnaris carpi
What is unusal about the scaphoid?
Unusual blood supply- retrograde flow
Via dorsal carpal branch of the radial artery
Enters dorsal surface of scaphoid distally, supplies proximal 80% of scaphoid by retrograde flow (flow back towards the wrist)
Important to understanding why scaphoid fracture have a high rate of non-union
What do each of the metacarpal bones articulate with?
I- trapezium proximally, proximal phalanx of the thumb distally
II- trapexoid proximally, proximal phalanx of index finger distally
III- capitate proximally, proximal phalanx of middle finger distally
IV- Hamate proximally, proximal phalanx of ring finger distally
V- Hamate proximally, proximal phalanx of little finger distally
What is the structure of the metacarpal bones?
Base, shaft and head
Medial and lateral surfaces are concave (accomodate interossei muscles)
What movements are possible at the thumb?
Flexion* Extension* Radial abduction* Radial adduction Palmar abduction Palmar adduction Opposition Reposition Retropulsion Circumduction
*in coronal plane
What is flexion of the thumb?
Bending of the thumb
Bend at metacarpophalangeal joint and interphalangeal joint
What is extension of the thumb?
Returns flexed thumb to anatomical position
What is radial abduction?
Contunation of extension beyond the anatomical plane
In coronal plane
(if you were to spread your fingers out your thumb would be radially abducted)
What is opposition?
Rotatory movement of the thumb over the palm
Enables the thumb to touch the tips of the fingers
What is reposition?
Returning the thumb to the anatomical position from the position of opposition
What is palmar abduction?
Raising the thumb in the sagittal plane
Perpendicular to the palm
(perpendicular plane to radial abduction)
What is adduction?
Opposite of both palmar abduction and radial adduction
What is retropulsion?
Extending the thumb posteriorly beyond the coronal plane
What is circumduction?
Winding your thumb round in circles
What movement are possible with the fingers?
Flexion Extension Abduction Adduction Circumduction
What is the difference between the intrinsic and extrinsic muscles of the hand?
Intrinsic–> originate within the hand and insert within the hand
Extrinsic–> originate the forearm and insert within the hand
How can the intrinsic muscles of the hand be divided?
Four compartments Thenar compartment Adductor compartment (adductor pollicis) Hypothenar compartment Central compartment
What muscles are in the thenar compartment?
Form the thenar eminence
Abductor pollicis brevis
Flexor pollicis brevis
Opponens pollicis –> largest, lies deepest
What muscles are in the hypothnar compartment?
Abductor digit minimi
Flexor digiti minimi
Opponens digiti minimi–> deepest
What muscles are in the central compartment?
Lumbricals
Interossei
Palamaris Brevis
What is the origin, insertion, innervation and function of the opponens pollicis?
Largest lies deepest
O: Trapezium and flexor retinaculum
I: Lateral border of 1st metacarpal
F: Opposes thumb (by medially rotating and flexing 1st metacarpal)
Innervation: Median nerve
What is the origin, insertion, innervation and function of the abductor pollicis brevis?
O: Scaphoid, trapezium and flexor retinaculum
I: Lateral border of proximal phalanx of thumb
F: Palmar abducts the thumb
Innervation: Median nerve
What is the origin, insertion, innervation and function the flexor pollicis brevis?
O: Superficial head: trapezium and flexor retinaculum
Deep head: Trapezoid and capitate
I: Ulnar aspect of base of proximal phalanx of thumb (with adductor pollicis)
F: Flexes metacarpophalangeal joint of thumb
Innervation: SH: Median nerve
DH: Ulnar nerve
What is the origin, insertion, innervation and function of the adductor pollicis?
O: Transverse head: shaft of 3rd metacarpal
Oblique head: capitate and base of 2nd and 3rd metacarpal
I: Ulnar aspect of base of proximal phalanx
F: Adductor of the thumb both the palmar adduction and radial adduction
Innervation: Ulnar nerve
What is the origin, insertion, innervation and function of the opponens digiti minimi?
Deepest
O: Hook of hamate, flexor retinaculum
I: Ulnar margin of 5th metacarpal
F: Rotates the 5th metacarpal towards the palm, enabling opposition against the thumb
Innervation: ulnar nerve
What is the origin, insertion, innervation and function of the abductor digiti minimi?
O: Pisiform and tendon of flexor carpi ulnaris
I: Base of proximal phalanx of little finger
F: Abduct the little finger (only in coronal plane)
Innervation: Ulnar nerve
What is the origin, insertion, innervation and function of flexor digiti minimi brevis?
O: Hook of hamate and flexor retinaculum
I: Base of proximal phalanx of little finger
F: Flexion of metacarpophalangeal joint of little finger
Innervation: Ulnar nerve
What is the origin, insertion, innervation and function of palmaris brevis?
O: Palmar aponeurosis and flexor retinaculum
I: Dermis of skin on medial margin of hand
F: Wrinkles the skin of hypothenar eminence, deepens the curvature of the palm, improving grip
Innervation: Ulnar nerve
What is the function of the lumbrical muscles?
Link the flexor digitorum tendon to the extensor digitorum tendon
Contract–> flex fingers at the metacarpophalangeal joint and extend at the interphalangeal joints
What is the muscles structure of the lumbircals?
Unipennate–> muscle fibres originate on same side of tendon
–> index and middle finger
Bipennate–> muscle fibres originate on opposite sides of the tendon
–> ring finger and little finger
What is the origin, insertion, innervation and function of each of the lumbricals?
I–> FDP to index finger –> Extensor digitorum (ED) to index finger
II–> FDP to middle finger –> ED to middle finger
III–> FDP to middle and ring finger –> ED to ring finger
IV–> FDP to ring and little finger –> ED to little finger
F: Extend the interphalageal joints, flex the metacarpophalangeal joints
Innervation: I and II–> Median nerve, III and IV–> ulnar nerve
What are the interossei muscles?
Located between the metacarpal bones PADs and DABs Palmar interossei--> adduct Dorsal interossei--> abduct All innervated by the ulnar nerve
What are the dorsal interossei?
Abduct away from the midline
Bipennate muscles
Originate from own metacarpal and adjacent metacarpal bones
What is the origin, insertion, innervation and function of dorsal interossei muscles?
I–> between thumb and first finger
O: Shaft of first and second metacarpals
I: Radial aspect of base of proximal phalanx of index finger and extensor expansion
II–>
O: Shaft of 2nd and 3rd metacarpals
I: Radial surface of base of proximal phalanx of middle finger and extensor expanion
III–>
O: Shaft of 3rd and 4th metacarpals
I: Ulnar surface of base of proximal phalanx of middle finger and extensor expansion
IV–>
O: Shaft of 4th and 5th metacarpal
I: Ulnar surface of base of proximal phalanx of ring finger and extensor expansion
F: Abduction away from the midline assist in flexing the metacarpophalangeal joint and extending the interphalangeal joint
Innervation: Ulnar nerve
What are the palmar interossei? Why is there less?
Adduct towards the midline
Unipennate muscles
Only three muscles
Thumb adduction carried out adductor pollicis
Middle finger is moved side to side by DABs
What is the origin, insertion, innervation and function of the palmar interossei?
O and I: Shaft of second metacarpal–> Ulnar side of base of proximal phalanx of index finger and extensor expansion
Shaft of fourth metacarpal–> Radial side of base of proximal phalanx of ring finger and extensor expanson
Shaft of fifth metacarpal–> Radial side of base of proximal phalanx of little finger and extensor expansion
F: Adduction
Innervation: Ulnar nerve
What are the extrinsic muscles of the hand that insert onto the digits?
Extensor digitorum
Flexor digitroum profundus
Flexor digitorum superficialis
What is the origin, insertion, innervation and function of extensor digitroum?
Posterior forearm muscle
O: Lateral epicondyle
I: Extensor expansion
–> Four tendons onto the phalanges
–> Divided into a central slip and two lateral slips
–> Central slip–>base of middle phalanx
–> Lateral slips–> converge to insert onto base of distal phalanx
F: Extension at the interphalangal joints and metacarpophalangeal joints
Innervation: Radial nerve
What is the origin, insertion, innervation and function of flexor digitorum profundus?
Anterior forearm muscle (deep)
O: Proximal 2/3rds of shaft of ulna and adjacent interosseous membrane on anterior forearm
I: Base of distal phalanx of 4 fingers
F: Flexion of the fingers
Innervation: medial half –> ulnar, radial half–> median nerve
What is the origin, insertion, innervation and function of flexor digitorum superficialis?
Anterior forearm muscle (superificial/ intermediate)
O:
-Humeroulnar head–> medial epicondyle of humerus, ulnar collateral ligament, coronoid process of ulnar
- Radial head–> superior half of radius
I: Base of middle phalanx of four fingers
F: Flexion of the metacarpophalangeal joint
Innervation: Medial
How are the tendons of the FDP and FDS arranged?
FDS tendon splits into two slips at the proximal phalanx
FDP tendon passes in between
What is the carpal tunnel?
Narrow passageway on anterior surface of the wrist
Entrance for tendons and median nerve
What are the borders of the carpal tunnel?
Superficial border: Flexor retinaculum (transverse carpal ligament) Deep border: carpal bones form concavity Lateral (radial): scaphoid, trapezium Medial (ulnar): pisiform, hook of hamate Proximal border: Distal wrist crease
What structures pass through the carpal tunnel?
Flexor pollicis longus tendon
Flexor digitorum superficialis tendon (x4) (tendons of middle and ring finger pass superficial to the index and little finger tendon)
Flexor digitroum profundus tendon (x4)
Median nerve–> lateral to FDS tendons
Which nerve branches off superficial to the carpal tunnel? Why is this important?
Palmar cutaneous branch of the median nerve
Compression of medial nerve in carpal tunnel syndrome doesn’t affect sensation to the palmar surface
What is Guyon’s canal?
Semi-rigid longitudinal canal in the wrist
Allows passage of the ulnar nerve and artery into the hand
Where is Guyon’s canal located?
Superficial to flexor retinaculum
Radial to pisiform bone
Between pisiform bone and hook of hamate
Roof–> palmar carpal ligament (distinct from the transverse carpal ligament (flexor retinaculum))
Why is Guyon’s canal important?
Site of ulnar nerve compression
Ulnar nerve not involved in carpal tunnel syndrome
What is the anatomical snuffbox?
Triangular depression on the radial surface of dorsum of the hand
Level of carpal bones
What are the borders of the anatomical snuffbox?
Radial (lateral) border–> tendon of abductor pollicis longus and extensor pollicis brevi
Ulnar (medial) border–> tendon of extensor pollicis longus
Proximal border–> styloid process of the radius
Floor–> Scaphoid and trapezium
Roof–> skin
What are the contents of the anatomical snuffbox?
Radial artery
Superficial branch of radial nerve
Cephalic vein
What is the arterial supply to the hand?
Radial and ulnar artery supply the hand via deep and superficial palmar arches
Where does the ulnar artery pass?
Crosses anterior to the flexor retinaculum with the ulnar nerve in Guyon’s canal
Lies radial to pisiform bone and ulnar nerve
In hand divides into superficial and deep branches
Anastomose with corresponding branches of radial artery to form superficial and deep palmar arches
Superficial palmar arch–> common palmar digital arteries that supply the fingers
Where does the radial artery pass?
Enters between the tendons of brachioradialis and flexor carpi radialis
GIve off superificial branch that anastomoses with the superficial palmar arch, then passes dorsally to cross the floor of the anatomical snuffbox on dorsum of the hand
Re-enters palm passing between the two heads of adductor pollicis
Radial artery anastomoses with the deep artery to form deep palmar arch
Where do the ulnar and radial artery mainly supply?
Ulnar artery–> mainly superficial palmar arch–> blood supply to fingers
Radial artery–> deep palmar arch–> blood supply to thumb and radial side of index finger
What is the nerve supply to the hand?
Radial, ulnar and medial nerve
Radial–> posterior forearm
Ulnar and median–> anterior forearm and muscles of the hand
What is the motor supply to the muscles of the hand?
All ulnar expect
1/2 LOAF–> (1/2 lumbricals (radial side), Opponens pollicis, abductor pollicis brevis and flexor pollicis brevis (superficial head))–> median nerve
What is the sensory innervation to the palmar surface of the hand?
Fingertip originate on palmar surface of the hand in development
Dragged over to dorsal aspect–> take nerve supply with them
Nerve supply to palmar surface–> palmar cutanous branch of median nerve (Carpal tunnel), palmar cutanous branch of ulnar nerve (Guyon’s canal)
What is the sensory innervation to the fingers?
Palmar digital branches from the median and ulnar nerves in the palm
Palmar digital branch of the median nerve–> thumb, index finger, middle finger and radial border of ring finger
Palmar digitial branch of ulnar nerve–> ulnar border of ring finger and little finger
Innervate the dorsum of these digits over the distal phalanx and nail bed
What is the sensory innervation to the dorsal surface of the hand?
Dorsal cutaneous branch of ulnar nerve
–> main forearm
–> Skin over dorsal aspect of ulnar border of hand
–> Skin over dorsum of ulnar 1.5 digits as far as the distal interphalangeal joint
Superficial branch of the radial nerve
–> Lateral side of dorsal hand and lateral 3.5 digits except the tips (palmar digital branches of the median nerve)
Where would you test the sensory innervation of each of these nerves?
Radial nerve: Dorsum of the first webspace
Median nerve: Palmar surface of the tip of the index finger
Ulnar nerve: Ulnar border of the hand
What are the different fractures that can occur at the wrist?
Scaphoid fracture
Colles’ fracture –> extra articular fracture of the distal radial metaphysis, with dorsal angulation and impaction -(dorsiflexed hand)
Smith fractures–> Fracture of distal radius with volar (palmar) angulation of the distal fracture fragments -(palmar flexed hand)
Which fractures commonly occur due to falling on an outstretched hand? (FOOSH)
What does FOOSH cause?
Scaphoid fracture
Colles fracture
Hyperextension and impaction of scaphoid against rim of radius or direct axial compression of scaphoid
What is the typical presentation of a patient with a scaphoid fracture?
Occur at any age—> most common among adolescent and young adults following FOOSH
Pain in anatomical snuffbox
Made worse by movement
Passive range of movement reduced—> not dramatically
Swelling around radial and posterior aspect of the wrist is common
What are the different types of fracture to the scaphoid?
Fracture to the waist (70-80%)
Fracture to proximal pole (20%)
Fracture to distal pole (10%)—> scaphoid tubercle fracture
What would you see on an X-ray of a fractured scaphoid?
X-ray may not reveal anything
10-14days fracture maybe visible after some bone reabsorption has occurred
MRI, CT scans maybe required
Why are fractures to the scaphoid quite severe?
Retrograde blood supply (distal to proximal supply)
Blood supply to proximal pole tenuous
Fractures to waist of the scaphoid—> avascular necrosis
Displaced fractures through the waist lead to higher risk of non union, malunion, avascular necrosis and late complications of carpal instability and secondary osteoarthritis
Osteaoarthritis more common if there has been non union, malunion or avascular necrosis
What is a Colles’ fracture?
Extra-articular fracture
Fracture of distal radial metaphysis, with dorsal angulation and impaction
Associated ulnar fracture present in 50% of cases
Fall on dorsiflexed hand
Who is most likely to present with a Colles’ fracture what is the mechanism of fracture?
Common in patients with osteoporosis (reduced bone density)–> post menopausal women (young patients usually involved in high trauma accidents)
Most common fracture–> FOOSH
Forearm pronated and wrist in dorsiflexion
Energy transmitted from the carpal to the radius in dorsal direction and along the long axis of radius–> Dorsally angulated and impacted
What is the clinical presentation of Colles’ fracture?
Painful, swollen, deformed wrist –> dinner fork shapped
What would you see on an x-ray of Colles’ fracture?
Fracture line clearly visible
Angulation and impaction visible
How are Colles’ fractures treated?
Reduction and immobilisation in cast
What are some of the complications associated with Colles’ fracture?
Malunion–> dinner fork deformity
Median nerve palsy and post traumatic carpal tunnel syndrome
Secondary osteoarthritis
Tear of extensor pollicis longus tendon- as tendon moves over sharp bone
What is Smith’s fracture?
Fractures of distal radius with volar (palmar) angulation of the distal fracture fragment
Extra-articular–> opposite of Colles’ fracture
Fall onto plantarflexed wrist
How do Smith’s fractures occur?
(Less than 3% fractures)
Young males or elderly females
Fall onto dorsum of flexed wrist or direct blow to back of the wrist
What does a Smith’s fracture usually resemble? What is a complication of this deformity?
Garden spade deformity
Residual volar displacement results in cosmetic deformity
Narrows carpal tunnel–> carpal tunnel syndrome
How does rheumatoid arthritis of the MCPJ and IPJs occur?
Autoimmune disease
Autoantibodies attack the synovial membrane
Inflammed synovial cells proliferate to form a pannus (abnormal layer of granulation tissue)
Penetrates through the cartilage and adjacent bone–> bone erosion and deformity
Why is rheumatoid arthritis of the hand difficult to diagnoses?
Affects multiple joint–> symmetrical distribution
Difficult as no ‘normal’ hand to make a comparison
How does a patient with rheumatoid arthritis of the hands normally present?
Pain and swelling of PIPJs and MCPJs of the fingers
Erythema (redness) overlying joints
Stiffness–> worse in the morning or after periods of inactivity –> difficult to carry out some tasks- doing up buttons
Carpal tunnel syndrome–> compression of median nerve
Fatigue and flu like symptoms–> systemic nature of disease
What are the late features of rheumatoid arthritis?
Nodules over the fingers and elbows
Deformities–> Swan neck and Boutonniere deformity
What are the features of rheumatoid arthritis on an x-ray?
Narrowing of joint space Periarticular osteopenia Juxta-articular bony erosions Subluxation and gross deformities Soft tissue swelling inferred from shadow
What is Swan neck deformity?
PIPJ hyperextends and MCPJ and DIPJ are flexed
PIPJ lax due to adjacent synovitis on volar surface
Imbalance between muscle forces extension>flexion
DIPJ elongation or rupture of insertion of extensor tendon–> flexion (mallet deformity)
What is Boutonniere deformity?
PIPJ flexed and MCPJ and DIPJ hyperextended
Inflammation at PIPJ–> lengthening or rupture of central slip of extensor digitorum as it insert into base of middle phalanx on dorsal surface–> lateral bands slips into side–> acts as flexor at PIPJ and hyperextend at DIPJ
What is psoriatic arthropathy?
Psoriasis that develops into arthritis
Involves small joints of the hand and feet
Develops asymmetrically
What is psoriasis?
Skin condition
Red, flaky patches of skin covered with silvery scales
Usually on knee, elbows, scalp and lower back
Which joints are normally affected in psoriatic arthritis?
DIPJs
80% have nail lesions also–> pitting and onycholysis
Where in the hand does osteoarthritis normally affect?
1st CMC joint –> trapezium and 1st metacarpal
More common in women
What do patients normally present with in osteoarthritis?
Pain in base of their thumb
Exacerbated by movement, relieved by rest
Stiffness follows periods of rest
Swelling around base of thumb
Later stages–> 1st metacarpal subluxes in ulnar direction
Squaring of the hand
Spreads to fingers in fifth or sixth decade of life –> DIPJs
What are Heberden’s nodes?
Classic sign of osteoarthritis and affects DIPJ of fingers
Chronic swelling of affected joint–> sudden onset of pain, swelling and loss of manual dexterity
Cystic swellings develop–> gelatinous hyalronic acid on dorsolateral apsect of DIPJ
Initial pain and swelling eventually subsides–> osteophyte formation instead
What are Heberden’s nodes in the PIPJs called?
Bouchard’s nodes
What is carpal tunnel syndrome?
Compression of the median nerve as it passes through the carpal tunnel
What are the risk factors for carpal tunnel syndrome?
Obesity, pregnancy, repetitive wrist work, rheumatoid arthritis and hypothyroidism
What is the result of compression of the median nerve?
Paraesthesia in thumb, index finger, middle finger and radial half of ring finger
Long standing–> thenar muscle weakness (Flexor Pollicis brevis (superficial head), Abductor Pollicis Brevis and Opponens pollicis)
When does carpal tunnel syndrome become worse?
At night–> flexion of wrist when sleeping–> narrowing of carpal tunnel
Worsen in daily activities such as driving, combing hair, holding a book or phone etc…
What is diminished in patients with carpal tunnel syndrome?
Manual dexterity
Unable to button clothes
Pain in forearm, elbow, shoulder and neck (do not need to know why)
Why is sensation to the palm spared in carpal tunnel syndrome spared?
Palmar cutaneous branch of median nerve branches proximal to carpal tunnel
What is ulnar tunnel syndrome or Guyon’s canal syndrome?
Compression of the ulnar nerve in Guyon's canal Passes radial (lateral) to the pisiform bone over the volar surface of flexor retinaculum
What are the symptoms of Guyon’s canal syndrome?
Paraesthesia in ring and little finger
Long term–> weakness of intrinsic muscles of the hand
What is Dupuytren’s contracture?
Localised thickening and contraction of palmar aponeurosis–> flexion deformity of the adjacent fingers
What are the first signs of Dupuytren’s contracture?
Thickening in palm (nodule)–> painful or painless
Myofibroblast in nodule contract–> cords in palmar fascia–> overlying skin tightly adhered
Progresses to involve the proximal fascia and skin of the fingers
Fingers become stuck in flexed position and cannot be passively straightened
Which fingers are most commonly involved? Who is it most commonly seen in?
Ring and little finger
Males
40-60 years
North European origin
What is the genetics of Dupuytren’s contracture?
Autosomal dominant
70% cases–> family history
Remainder sporadic
What increases the risk of Dupuytren’s contracture?
Type 1 diabetes
Having had adhesive capsulitis of the shoulder (frozen shoulder)
Epilepsy–> drugs
Liver disease and/or excessive alcohol consumption
Smoking
Hypercholersterolaemia
Heart disease
HIV
Hypo-/ Hyper- thyroidism
Trauma to hand or fingers
Vibration-related hand injury (vibrating tools >10yrs)
(LEARN FOUR EXAMPLES!)
Why are fractures to the humerus in the midshaft dangerous?
At risk of damaging the radial nerve
Runs in the spinal groove
Following midshaft humeral fracture will the patient still be able to extend their elbow?
Extension normal or partially compromised
Nerve supply to long and lateral head of triceps given off before the radial nerve enters the spiral groove
Triceps still able to extend
Anconeus–> paralysed but only had minor role in extension
What is the clinical presentation following radial nerve damage?
‘Wrist drop’ –> Flexion of wrist and fingers
Paralysis to extensor muscles (posterior forearm)
Flexed when forearm is pronated due to unopposed flexor muscles and gravity
Sensory innervation–> posterior cutaneous nerve branches before the spiral groove so unaffected
Lower lateral and posterior cutaneous nerve unaffected
Paraesthesia therefore usually in superficial branch of radial nerve–> lateral part of dorsum of the hand from thumb up to middle of ring finger, excluding the tips of all the fingers and thumb
What is the result of a supracondylar fracture of the humerus?
Median nerve damage
Paralysis to flexor muscles of the anterior forearm expect FCU and medial half of FDP
Paralysis to thenar muscles and radial half of lumbricals
Forearm supinated–> unapposed action of supinator (radial nerve) and biceps brachii (musculcutaneous nerve)
Wrist adducted (FCU)
Loss of sensation to radial side of palm up to middle of ring finger and tips of thumb, index and middle finger on dorsal surface
Prolonged–> thenar muscle wasting
What is the clinical test for median nerve damage?
Attempt to make a fist
Ring and little finger will flex into palm normally (FDP and lumbricals intact)
Index and middle finger will remain extended
Thumb will be adducted, lateraly rotated, and extended (IPJ and MCPJ)
Hand of Benediction –> only seen when patient attempts to make a fist
What is the difference if the median nerve is only damaged at the wrist?
Penetrating injury or compression of carpal tunnel
Only muscles paralysed are 1/2LOAF
Ape Hand deformity - thenar eminence is flatterened and thumb us adducted and externally (laterally) rotated
Palmar cutaneous branch of median nerve also spared–> skin over thenar eminence spared
Prolonged–> thenar muscle wasting
What happens if the ulnar nerve is damaged at the wrsit?
Laceration or compression of Guyon’s canal
Loss of function of all muscles of the hand except 1/2LOAF
Claw hand–> little finger and ring finger only
–> Hyperextension of the MCPJ
–> Flexion of PIPJ and DIPJ
Loss of sensation–> Palmar aspect of ulnar 1.5 digits and dorsum of hand over the distal phalanges only
Why do you get hyperextension to the MCPJ and flexion of the PIPJ and DIPJ of the little finger and ring finger in ulnar wrist lesion?
Lumbrical muscles to ring and little finger paralysed
Normally involved in flexion at the MCPJ–> hence hyperextension –> unopposed extensor digitiroum
Extenion of PIPJ and DIPJ–> hence flexion –> unopposed FDS and FDP
What happens to the other muscles of the hand with a ulnar nerve injury to the wrist?
Not involved in claw hand
Interossei, hypothenar muscles, adductor pollicis
Interossei wasting–> guttering between metacarpals
AP and Hypothenar–> wasting of 1st webspace and hypothenar eminence
What could cause an upper nerve lesion? What happens with a high ulnar nerve lesion?
Fracture to medial epicondyle, compression in cubital tunnel
Paralysis of FCU and ulnar half of FDP as well as intrinsic muscles of the hand (except 1/2LOAF)
Loss of sensation of dorsal and palmar cutaneous branch –> little finger and ulnar half of ring finger on palmar and dorsal surface
What is the clinical presentation of a upper ulnar nerve lesion?
Claw hand will be less pronounced
Why?–> FDP is paralysed so no flexion at DIPJ in ring and little finger
Ulnar claw only consists of hyperextension of MCPJ and flexion of PIPJ
What is the difference between upper and lower ulnar nerve lesions called?
Ulnar paradox
Would expect an upper nerve lesion to have more pronounced deformity but in this case it doesn’t
