Upper - Clinical Flashcards
what are HOX genes
complex interplay of gene activation and transcription via many growth and signalling proteins
make sure the boys is in the right places etc, layout of the body
what do the somites develop into
limb muscle
what does the lateral plate mesoderm develop into
limb bones and connective tissue
what are the two divisions of the somites
ventral sclerotome - vertebral column
dorsolateral dermomyotome - dermatome (dermis of skin) and myotome - skeletal muscles
the ventral part of a myotome migrates into limb buds and divides into what two buds
anterior part - muscles of the front of the limb ( flexors)
posterior part - muscles of the back of the limb extensors
what is the upper limb innervated by
branches of the ventral primary rami of nerves C5 to T1
what are the 3 axis of limb development
proximodistal - from the shoulder to the hand (from hip to foot)
craniocaudal - the thumb is the most cranial and the little finger is the most caudal
dorsoventral - the palm of the hand and sole of the foot are ventral and the back of the hand and top of the foot are the dorsal
what is FGF10
fibroblast growth factor which is secreted by mesenchymal core of the limb bud which induces thickening to the overlying ectoderm
what is the progress zone
area of mesenchymal cells underlying the apical ectodermal ridge (AER)
this area maintains proximodistal outgrowth of the limb
what happens when AER is interrupted or removed
inhibits proximodistal outgrowth and forms deformities
what is amelia and meromelia
a - complete absence of limb
m - partial absence of limb
what is supernumerary limbs
ectopic FGF causes growth of another limb
what happens when the central part of the AER fails
caused cleft hand or foot
what is polydactyly
craniocaudal issue
extra fingers or toes
what is nail patella syndrome
defect in LMX1B - abnormality of the nail with small, absent or irregular patellae
what is syndactyly
dorsoventral issue
fused digits due to failure of normal apoptosis
what are some causes of limb abnormalities
genetics - herediatary or spontaneous drugs environmental poisons maternal illness amniotic band syndrome
what is phocomelia
malformation which was caused by thalidomide
digits develop prematurely
proximal elements of limb absent
it inhibits expression of FGF10 and 8 and is thought to inhibit angiogenesis - prevents proximodistal lengthening of the limbs
describe anterior shoulder dislocation and the risks
most common - axillary nerve implicated - first posterior branch of brachial plexus goes behind surgical head - movement of head causes damage to nerve
axillary supplies deltoid
loss of C5-6 sensation (upper limb lateral arm)
describe midshaft humeral fracture and the risks
20% associated with nerve damage - radial nerve runs in radial groove - risk of damage
inability of extensors of arm and wrist
who are more affected by supracondylar humeral fractures and the risks
common in children
distal humeral fracture
what are fat pads
visible anterior small ones are normal
- large anterior fat pads indicate fracture
small or large on posterior indicates fracture
what are ossification centres
ends of long bones in children aged 2-10 may be misinterpret as fractures
what is a colles’ fracture
distal radius fracture but dorsal displacement fragment
what is a smith fracture
opposite of colles - fall on flexed hand (uncommon) distal radius fracture where the dorsal displacement goes palmar
what is a carpal bone fracture and what are the risks
missing carpal bone fracture is most common cause of litigation
include scaphoid fracture
risk of avascular necrosis of radiocarpal joint
(no fat pads to indicate fracture in wrist)
what is a dermatome
skin region innervated by a single nerve or vertebral level
what is a myotome
muscle/groups innervated by a single nerve or vertebral level
what can cause brachial plexus damage
injuries at birth
blunt trauma
penetrating wounds into axilla or neck
disease
what are the different diseases of upper and lower brachial plexus injury
superior - C5/6 - erbs palsy
inferior - C8, T1 - klumpkes palsy
what part of the brachial plexus will 1st rib injuries cause compared to cervical cord injuries
1st rib - affect trunks
CC - affects roots
what is erbs palsy
excessive starching of neck during delivery - damage C5/6
often due to shoulder dystocia
paralysis of shoulder and arm muscles supplied by C5/6 (axillary and musculocutaneous)
causes atrophy of deltoid, biceps and lateral rotator shoulder
how do you acquire erbs palsy as an adult
falls on side of head and shoulder forcing apart - motorbike accidents
MRI shows nerve damage
what is klumpkes palsy in children
damage to inferior trunk of plexus ie c8 and t1 - ulnar nerve
less common than erbs
occurs in delivery if upper limb is excessively pulled
how does klumpkes palsy get acquired in adults
when upper limb is suddenly pulled superiorly - graphing to prevent fall
MRI shows rot damage
what does the ulnar nerve innervate and therefore what muscles are affected by klumopke palsy
nothing in the arm
forearm - FCU, medial half of FDP
in hand - hypothenar eminence, adductor pollicis, all interossei, medial 2 lumbricals
what areas of the skin does klumpkes palsy affect
ulnar nerve damage which provide sensation to medial side of hand and forearm
what is klumpkes palsy commonly associated with
horners syndrome (ptosis, mitosis, anhidrosis, vasodilation) T1 provides some sympathetic input to head and may be damaged
