Chapter 26 - Congenital Hand and Wrist Differences and Brachial Plexus Birth Injury Flashcards
What guides proximal to distal limb development?
Apical ectodermal ridge, also responsible for interdigital apoptosis, and is mediated by FIBROBLAST growth factors
What guides radioulnar development (anterior/posterior)?
Zone of polarizing activity, mediated by sonic hedgehohg
order of carpal ossification
Capitate first (3-4 months), hamate (4-8 months), triquetrum (2 to 3 years), lunate (4 years), scaphoid (4-5 years), trapezium (5 years), trapezoid (6 years), pisiform (6-8 years)
What is the most common carpal coalition?
lunotriquetral
What is PRE-axial polydactyly?
thumb duplication
Genetics of pre-axial polydactyly:
1:10,000 live births, Male»_space; female, whites»_space; blacks
SPORADIC mutations
Wassel classification of pre-axial polydactyly
I: bifid distal phalanx
II: duplicated distal phalanx
III: bifid proximal phalanx
IV: duplicated proximal phalanx
V: Bifid metacarpal
VI: duplicated metacarpal
VII: triphalangism
Type IV most common (43%) followed by type II (15%)
Pollex abductus
Abnormal connection between the EPL and the FPL tendons, seen in ~20% of hypoplastic thumbs, thumb held abducted and no visible IP creases
Which thumb is usually the more hypoplastic one
the radial thumb. treatment involved ablation of the bony elements and reconstruction of the radial collateral ligament
Post axial polydactyly
Duplication of the ulnarmost digit
Autosomal dominant with variable penetrance
AA»caucasians
What syndromes if radial longitudinal deficiency associated with?
Thrombocytopenia absent radius
Holt-Oram
VACTERL
Fanconi Anemia
RLD findings in Thrombocytopenia Absent Radius (TAR)
abset radius
hypoplastic thumb
low platelets at birth that normalize over time
RLD findings in Fanconi anemia
normal platelet and blood counts at birth then rapidly develop pancytopenia
diagnosed with mitomycin-c or diepoxybutane chromosomal challenge
treatment is bone marrow transplant
RLD findings in Holt oram syndrome
mutations in the TBX5 gene
RLD plus cardiac - congenital heart diseases, ASD, VSD
surgical treatment of RLD
Centralization - ulna aligned with LF MC
Radialization - ulna aligned with IF MC (often requires a soft tissue lengthening procedure first
complications and contraindications to surgery for RLD
most common complication - recurrence of deformity
contraaindications - older patients who have adapted already, severe elbow stiffness
Ulnar longitudinal deficiency
5-10 times less common that RLD
usually sporadic but some (Rare) AD
Ulnar longitudinal deficiency
5-10 times less common that RLD
usually sporadic but some (Rare)ass AD
Associated findings with ULD
thumb duplication/hypoplasia, elbow instability, radial head dislocation, proximal synostosis
Macrodactyly clinical features
unilateral, affects the radial digits
syndromes associated with macrodactyly
neurofibromatosis, proteus syndrome, Klippel-Trenaunay-weber syndrome
Associated abnormalities with amniotic band syndrome
Clubfoot, cleft palate, craniofacial defects
what percentage of constriction bands occur distal to the wrist?
> 90%, central digits are more commonly affected
What is the cause of syndactyly?
Failure of differentiation via apoptosis
genetic inheritance of syndactyly?
Autosoman dominant with variable penetrance
Syndromes associated with syndactyly
Poland syndrome: congenital absence of the sternocostal head of the pectoralis major, limb hypoplasia, symbrachydactyly
Apert syndrome: (aka acrocephalosyndactyly) mental retardation, premature fusion of the cranial sutures > high ,broad forehead wth occipital flattening, bulging low set eyes, acrosyndactyly/spade hand
Define simple syndactyly:
conjoined digits - with only soft tissue interposed
Define Complex syndatyly
fusion of the phalanges/bones
define complicated syndactyly
interposition of abnormal bones or accessory phalages
complete syndactyly
webbing goes all the way to the distal tip of the involved digits
incomplete syndactyly
webbing stops proximal to the distal extent of the involved digits
frequence a webspace is involved in syndactyly
third (50%), fourth (30%), second (15%), first (5%)
what type of incision should you avoid in order to prevent scar constracture
avoid longitudinal incisions (use zigzag lateral flaps) to avoid longitudinal scar contracture
Define camptodactyly
flexion contracture of a finger, most commonly of the PIP joint, and most commonly the ulnar digits
genetics of camptodactyly
most are sporadic, few cases of autosomal dominant with variable penetrance
“Congenital” trigger thumb
Constriction of the fpl at the 1 pulley
likelihood of spontaneous correct is 30-60%
“Congenital” trigger finger
10x less common than trigger thumb
Often caused by anomalous anatomy - abnormal lumbrical insertion, proximal decussation of the FDS
can be associated with mucopolysaccharidoses
50% rate of recurrence if you only release A1 - must address the anomalous anatomy (lumbrical, a slip of FDS,e tc)
Clinodactyly definition
angular digit deformity in the radioulnar plane
Genetics of clinodactyly
Autosomal dominant, some syndromic association including trisomy 21
Delta phalanx
a digit with a proximal physis that is NOT oriented perpendicular to the long axis of the physis
shortened side of the phalanx contains the longitudinal epiphyseal bracket
risk factors for brachial plexus birth injury
macrosomia, shoulder dystocia, difficult delivery, previous child with brachial plexus birth injury
Prognosis of brachial plexus birth injury
60-90% spontaneous recovery
if 3/5 biceps by 2 months -> full recovery is expected
if biceps recovery not until >=5 months - incomplete recovery likely
what symptom portends a poor prognosis in BPBI?
Horner syndrome - ptosis, miosis, anhydrosis, suggests a nerve root avulsion, very poor prognosis for recovery
