Chapter 26 - Congenital Hand and Wrist Differences and Brachial Plexus Birth Injury

Question 1

What guides proximal to distal limb development?

Answer 1

Apical ectodermal ridge, also responsible for interdigital apoptosis, and is mediated by FIBROBLAST growth factors

Question 2

What guides radioulnar development (anterior/posterior)?

Answer 2

Zone of polarizing activity, mediated by sonic hedgehohg

Question 3

order of carpal ossification

Answer 3

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)

Question 4

What is the most common carpal coalition?

Answer 4

lunotriquetral

Question 5

What is PRE-axial polydactyly?

Answer 5

thumb duplication

Question 6

Genetics of pre-axial polydactyly:

Answer 6

1:10,000 live births, Male&raquo_space; female, whites&raquo_space; blacks

SPORADIC mutations

Question 7

Wassel classification of pre-axial polydactyly

Answer 7

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%)

Question 8

Pollex abductus

Answer 8

Abnormal connection between the EPL and the FPL tendons, seen in ~20% of hypoplastic thumbs, thumb held abducted and no visible IP creases

Question 9

Which thumb is usually the more hypoplastic one

Answer 9

the radial thumb. treatment involved ablation of the bony elements and reconstruction of the radial collateral ligament

Question 10

Post axial polydactyly

Answer 10

Duplication of the ulnarmost digit

Autosomal dominant with variable penetrance
AA»caucasians

Question 11

What syndromes if radial longitudinal deficiency associated with?

Answer 11

Thrombocytopenia absent radius
Holt-Oram
VACTERL
Fanconi Anemia

Question 12

RLD findings in Thrombocytopenia Absent Radius (TAR)

Answer 12

abset radius
hypoplastic thumb
low platelets at birth that normalize over time

Question 13

RLD findings in Fanconi anemia

Answer 13

normal platelet and blood counts at birth then rapidly develop pancytopenia

diagnosed with mitomycin-c or diepoxybutane chromosomal challenge

treatment is bone marrow transplant

Question 14

RLD findings in Holt oram syndrome

Answer 14

mutations in the TBX5 gene
RLD plus cardiac - congenital heart diseases, ASD, VSD

Question 15

surgical treatment of RLD

Answer 15

Centralization - ulna aligned with LF MC
Radialization - ulna aligned with IF MC (often requires a soft tissue lengthening procedure first

Question 16

complications and contraindications to surgery for RLD

Answer 16

most common complication - recurrence of deformity

contraaindications - older patients who have adapted already, severe elbow stiffness

Question 17

Ulnar longitudinal deficiency

Answer 17

5-10 times less common that RLD
usually sporadic but some (Rare) AD

Question 17

Ulnar longitudinal deficiency

Answer 17

5-10 times less common that RLD
usually sporadic but some (Rare)ass AD

Question 18

Associated findings with ULD

Answer 18

thumb duplication/hypoplasia, elbow instability, radial head dislocation, proximal synostosis

Question 19

Macrodactyly clinical features

Answer 19

unilateral, affects the radial digits

Question 20

syndromes associated with macrodactyly

Answer 20

neurofibromatosis, proteus syndrome, Klippel-Trenaunay-weber syndrome

Question 21

Associated abnormalities with amniotic band syndrome

Answer 21

Clubfoot, cleft palate, craniofacial defects

Question 22

what percentage of constriction bands occur distal to the wrist?

Answer 22

> 90%, central digits are more commonly affected

Question 23

What is the cause of syndactyly?

Answer 23

Failure of differentiation via apoptosis

Question 24

genetic inheritance of syndactyly?

Answer 24

Autosoman dominant with variable penetrance

Question 25

Syndromes associated with syndactyly

Answer 25

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

Question 26

Define simple syndactyly:

Answer 26

conjoined digits - with only soft tissue interposed

Question 27

Define Complex syndatyly

Answer 27

fusion of the phalanges/bones

Question 28

define complicated syndactyly

Answer 28

interposition of abnormal bones or accessory phalages

Question 29

complete syndactyly

Answer 29

webbing goes all the way to the distal tip of the involved digits

Question 30

incomplete syndactyly

Answer 30

webbing stops proximal to the distal extent of the involved digits

Question 31

frequence a webspace is involved in syndactyly

Answer 31

third (50%), fourth (30%), second (15%), first (5%)

Question 32

what type of incision should you avoid in order to prevent scar constracture

Answer 32

avoid longitudinal incisions (use zigzag lateral flaps) to avoid longitudinal scar contracture

Question 33

Define camptodactyly

Answer 33

flexion contracture of a finger, most commonly of the PIP joint, and most commonly the ulnar digits

Question 34

genetics of camptodactyly

Answer 34

most are sporadic, few cases of autosomal dominant with variable penetrance

Question 35

“Congenital” trigger thumb

Answer 35

Constriction of the fpl at the 1 pulley

likelihood of spontaneous correct is 30-60%

Question 36

“Congenital” trigger finger

Answer 36

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)

Question 37

Clinodactyly definition

Answer 37

angular digit deformity in the radioulnar plane

Question 38

Genetics of clinodactyly

Answer 38

Autosomal dominant, some syndromic association including trisomy 21

Question 39

Delta phalanx

Answer 39

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

Question 40

risk factors for brachial plexus birth injury

Answer 40

macrosomia, shoulder dystocia, difficult delivery, previous child with brachial plexus birth injury

Question 41

Prognosis of brachial plexus birth injury

Answer 41

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

Question 42

what symptom portends a poor prognosis in BPBI?

Answer 42

Horner syndrome - ptosis, miosis, anhydrosis, suggests a nerve root avulsion, very poor prognosis for recovery