Congenital Hand Flashcards
1
Q
What triggers upper limb development?
A
Limb buds form in week 4 (days 26–27) via FGF signaling from the AER.
2
Q
What forms in week 5 of upper limb development?
A
The hand paddle, nerves, and arteries begin to develop.
3
Q
When do digital rays appear?
A
Digital rays emerge in week 6 as the hand differentiates.
4
Q
What separates digits in embryogenesis?
A
Apoptosis in week 7, regulated by BMP and TGF-β, separates digits.
5
Q
When is upper limb development complete?
A
By week 8, all major structures (bones, muscles, nerves) are fully formed.
6
Q
What tissues make up the limb bud?
A
Mesenchyme covered by ectoderm drives limb growth through proliferation.
7
Q
When do limb buds first appear?
A
Limb buds emerge at the end of week 4 (days 26–27) from lateral mesoderm.
8
Q
What is the critical period for limb development?
A
Days 24–36 after fertilization are key for limb patterning and growth.
9
Q
When are finger buds visible?
A
Finger buds appear by the end of week 6.
10
Q
When does ossification start in the limb?
A
Ossification begins between weeks 8–12, starting with cartilage.
11
Q
Which hand bones ossify last?
A
Carpal bones start ossifying at 1 year old.
12
Q
Does motor or sensory innervation come first in limbs?
A
Motor axons enter first, followed by sensory axons guided by them.
13
Q
When is hand nervous system myelination complete?
A
Myelination finishes at 2 years old.
14
Q
Why is early intervention key for congenital hand issues?
A
It prevents functional impairment and boosts developmental outcomes.
15
Q
How does the AER drive limb development?
A
The AER controls the proximodistal axis by secreting FGFs to promote outgrowth.
16
Q
What defines the radioulnar axis?
A
Shh from the ZPA patterns the radioulnar axis and regulates HOX genes for digits.
17
Q
How is the dorsoventral axis established?
A
WNT7a from dorsal ectoderm activates Lmx-1b to set dorsal-ventral polarity.
18
Q
What inhibits FGF-8 during digit separation?
A
BMP and TGF-β block FGF-8 in the AER to trigger interdigital apoptosis.
19
Q
What genes regulate limb patterning?
A
HOX genes control digit and axis patterning with Shh.
20
Q
What happens if the AER is disrupted?
A
Proximodistal growth fails, potentially causing truncated limbs.
21
Q
How does Shh from the ZPA shape limbs?
A
It sets the radioulnar axis and drives HOX gene expression for digit identity.
22
Q
What role does BMP play in digit separation?
A
BMP inhibits FGF-8 in the AER to promote interdigital apoptosis.
23
Q
What does WNT7a do in limb development?
A
It establishes the dorsoventral axis by activating Lmx-1b in dorsal mesenchyme.
24
Q
How does the AER regulate interdigital apoptosis?
A
The AER balances FGF-8 with BMP/TGF-β to control digit separation.
25
How many phalanges does a normal thumb have?
A normal thumb has two phalanges: proximal and distal.
26
What enables thumb opposition?
Two phalanges, stable MCP/CMC joints, and thenar muscles enable opposition.
27
What stabilizes the thumb’s MCP joint?
Strong ligaments and thenar muscles stabilize the MCP joint.
28
What supports the thumb’s CMC joint?
The CMC joint relies on ligaments and a saddle shape for stability.
29
What classifies congenital hand anomalies today?
The OMT (Oberg-Manske-Tonkin) system classifies anomalies.
30
What are the main OMT categories?
Malformations, deformations, dysplasias, and syndromes.
31
What suggests a syndrome in hand anomalies?
Family history, bilateral involvement, and other anomalies point to syndromes.
32
What is syndactyly?
Syndactyly is finger fusion due to failed separation in embryogenesis.
33
When does syndactyly occur?
It develops in weeks 6–7 due to absent apoptosis.
34
How common is syndactyly?
It occurs in 1 in 2,000–3,000 live births, more in males and Caucasians.
35
Which digits are most fused in syndactyly?
The 3rd and 4th digits are fused in 55% of cases.
36
What defines simple syndactyly?
Simple syndactyly involves only soft tissue fusion.
37
What defines complex syndactyly?
Complex syndactyly includes bone or nail fusion.
38
Is syndactyly usually unilateral or bilateral?
It’s often bilateral, affecting hands and feet.
39
What’s the inheritance pattern of syndactyly?
Most cases are sporadic; some are autosomal dominant.
40
What are the goals of syndactyly surgery?
Separate digits fully, using zig-zag flaps and grafts if needed.
41
What complication occurs in 7–60% of syndactyly surgeries?
Distal web creep, where the web reforms distally.
42
Which syndromes link to syndactyly?
Apert (complex) and Timothy (with long QT) syndromes are associated.
43
What features define Apert syndrome?
Coronal craniosynostosis, complex syndactyly, and midface hypoplasia.
44
What’s unique about Timothy syndrome?
Syndactyly with prolonged QT interval, risking cardiac issues.
45
What is polydactyly?
Polydactyly is the presence of extra digits, either preaxial or postaxial.
46
What’s the most common hand anomaly?
Postaxial polydactyly (extra ulnar digit) occurs in 1 in 1,000 live births.
47
What defines preaxial polydactyly?
Preaxial polydactyly is an extra digit on the thumb side.
48
What defines postaxial polydactyly?
Postaxial polydactyly is an extra digit on the ulnar side.
49
What’s Wassel type IV polydactyly?
A bifid thumb with two proximal phalanges; the most common thumb duplication.
50
What mutation links to preaxial polydactyly?
Shh pathway mutations disrupt digit patterning.
51
What’s the goal of thumb duplication surgery?
Preserve the dominant thumb and reconstruct joints and muscles.
52
What is a triphalangeal thumb (TPT)?
TPT has three phalanges instead of two, altering length and function.
53
What shapes can TPT’s extra phalanx take?
Wedge-shaped (causing clinodactyly) or rectangular (finger-like).
54
Why is TPT often functional?
It’s opposable, supporting tasks, though opposition may be weaker.
55
What imaging best evaluates TPT bones?
Plain radiographs show phalanx number and shape for surgery planning.
56
When is MRI used for TPT?
MRI assesses soft tissues (tendons, ligaments) for complex cases.
57
What’s the functional goal of TPT surgery?
Enhance opposition and grip by shortening the thumb and stabilizing joints.
58
What’s the aesthetic goal of TPT surgery?
Reduce length and correct deformities for better appearance.
59
What technique is key in TPT surgery?
Precise phalanx resection and joint stabilization minimize complications.
60
What are common TPT surgery complications?
Stiffness, instability, or deformity recurrence require careful follow-up.
61
Which syndrome ties TPT to bone marrow failure?
Fanconi anemia links TPT with anemia.
62
What other syndromes associate with TPT?
Holt-Oram syndrome and radial ray defects are linked.
63
What’s the inheritance pattern of TPT?
Autosomal dominant; about two-thirds of cases are hereditary.
64
Is TPT more unilateral or bilateral?
Bilateral, often due to genetic causes.
65
When does TPT form in embryogenesis?
Between weeks 4–8, during limb bud and phalanx development.
66
What surgery suits a 5-year-old with bilateral TPT?
Shortening with phalanx removal and joint reconstruction improves grip.
67
How might TPT affect child development?
Fine motor issues or social stigma may arise, but many adapt.
68
What should parents know about TPT?
Surgery benefits/risks, timing, and possible multiple procedures.
69
What is radial longitudinal deficiency?
A radial club hand with an underdeveloped radius; 1 in 30,000 births.
70
What are key features of thumb hypoplasia?
Short thumb, unstable joints, weak thenar muscles, narrow web space.
71
What classifies thumb hypoplasia?
The Blauth system grades it from I (mild) to V (absent).
72
What’s the first treatment for radial deficiency?
Stretching and casting improve alignment non-surgically.
73
What surgery treats severe radial deficiency?
Wrist centralization or radialization corrects alignment.
74
What treats Blauth IV thumb hypoplasia?
Pollicization converts the index finger into a thumb.
75
What is camptodactyly?
A flexion contracture of the PIP joint, often in the little finger.
76
How is severe camptodactyly treated?
Splinting, then surgery if deformity exceeds 60 degrees.
77
What is clinodactyly?
Finger curvature in the radioulnar plane, often from a delta phalanx.
78
How is severe clinodactyly treated?
Wedge osteotomy corrects the phalanx curvature.
79
Which syndromes link to clinodactyly?
Down syndrome and Rubinstein-Taybi syndrome are associated.
80
What’s the X-ray finding in clinodactyly?
A delta phalanx causes finger curvature.
81
What is Madelung deformity?
Wrist deformity with palmar/ulnar radius tilt and dorsal ulnar shift.
82
What mutation causes Madelung deformity?
SHOX gene mutations link to skeletal dysplasias.
83
What surgery corrects severe Madelung deformity?
Vicker ligament release or dome osteotomy aligns the wrist.
84
What is congenital radioulnar synostosis?
Bony fusion of proximal radius and ulna, limiting rotation.
85
How is radioulnar synostosis diagnosed?
X-ray shows bony fusion in the proximal third of radius and ulna.
86
What’s the goal of radioulnar synostosis treatment?
Optimize forearm rotation via osteotomy or release.
87
What is transverse deficiency?
Limb absence distal to a level, often from amnion band syndrome.
88
What is symbrachydactyly?
Short, malformed fingers from vascular disruption in development.
89
What distinguishes amnion band from symbrachydactyly?
Amnion band is extrinsic (constriction); symbrachydactyly is intrinsic.
90
How is amnion band syndrome treated?
Surgical release of bands and reconstruction of affected areas.
91
What is macrodactyly?
Digit overgrowth due to PIK3CA-related overgrowth spectrum.
92
What causes macrodactyly?
PIK3CA mutations drive abnormal digit growth.
93
What mutation links to Holt-Oram syndrome?
TBX5 mutations affect heart and upper limb development.
94
What are Apert syndrome’s key features?
Coronal craniosynostosis, complex syndactyly, midface hypoplasia.
95
What’s unique about Timothy syndrome?
Syndactyly with prolonged QT interval affects cardiac function.
96
How does congenital radial head dislocation differ from traumatic?
Congenital is posterolateral with hypoplastic capitellum; traumatic is anterior.
97
What are features of ulnar longitudinal deficiency?
Short forearm and missing/hypoplastic ulnar digits.
98
What counsel should parents of a TPT child receive?
Discuss surgery benefits, risks, timing, and non-surgical options.
99
What principles guide syndactyly surgery?
Avoid both sides of a finger at once, use zig-zag flaps, graft if needed.
100
What are common syndactyly surgery complications?
Distal web creep (7–60%), scars, or keloids.
101
What’s the first step in treating radial deficiency?
Non-surgical stretching and casting to improve alignment.
102
What are surgical options for thumb duplication?
Reconstruct joints, ligaments, and muscles around the dominant thumb.
103
How is camptodactyly treated in young children?
Splinting and therapy reduce contracture.
104
What syndromes link to transverse deficiency?
Amnion band syndrome and thalidomide exposure are associated.
105
What’s the typical finding in congenital radioulnar synostosis?
X-ray shows bony fusion in the proximal third of radius and ulna.
106
What are the goals of severe radial deficiency surgery?
Centralize the wrist and improve hand function.
107
What’s the prevalence of thumb hypoplasia?
It accounts for 5–15% of congenital hand anomalies.
108
Is thumb hypoplasia more unilateral or bilateral?
Bilateral in over 50% of cases.
109
What diagnostic tests are used for thumb hypoplasia?
Cardiac/abdominal ultrasound, X-rays, and hematology tests.
110
What is pollex abductus in thumb hypoplasia?
An abnormal FPL-EPL connection, seen in one-third of cases.
111
What’s Blauth I thumb hypoplasia?
A smaller, shorter thumb with mild issues.
112
What’s Blauth II thumb hypoplasia?
MCP instability, reduced web space, and thenar hypoplasia.
113
What’s Blauth III thumb hypoplasia?
Global instability and thenar aplasia; IIIA has stable CMC, IIIB doesn’t.
114
What’s Blauth IV thumb hypoplasia?
A floating thumb (pouce flottant).
115
What’s Blauth V thumb hypoplasia?
Complete thumb absence.
116
What therapy suits Blauth I thumb hypoplasia?
Hand therapy or no treatment.
117
What therapy suits Blauth II-IIIA thumb hypoplasia?
Reconstruction of ligaments and muscles.
118
What therapy suits Blauth IIIB-V thumb hypoplasia?
Pollicization of the index finger.
119
What surgery deepens the 1st web space in thumb hypoplasia?
Z-plasty or kite flap widens the web.
120
What’s the prevalence of radial longitudinal deficiency?
1 in 30,000 live births.
121
Is radial longitudinal deficiency unilateral or bilateral?
50% unilateral, 50% bilateral.
122
What syndromes link to radial deficiency?
VACTERL, Fanconi anemia, TAR, Holt-Oram.
123
What are goals for radial deficiency treatment?
Stable shoulder, supple elbow, well-positioned wrist.
124
What’s the prevalence of ulnar longitudinal deficiency?
1 in 120,000 live births.
125
Is ulnar longitudinal deficiency syndromic?
Mostly isolated and unilateral.
126
What features mark ulnar longitudinal deficiency?
Thumb malformation (75%) and syndactyly (30%).
127
What’s the prevalence of Madelung deformity?
Rare (2% of anomalies), more in females, bilateral.
128
When does Madelung deformity present?
Between ages 8–14, often bilateral.
129
What structures cause Madelung deformity?
Short Vicker ligament and bony physeal bridge.
130
What syndromes link to Madelung deformity?
Leri-Weill dyschondrosteosis and Turner syndrome.
131
What happens to the radius in Madelung deformity?
Distal radius shortens with palmar-ulnar tilt.
132
What happens to the ulna in Madelung deformity?
Ulna elongates and shifts dorsally.
133
What treats Madelung in young patients?
Vicker ligament release and physeal bridge resection.
134
What treats Madelung in older patients?
Dome osteotomy and possible ulnar shortening.
135
Link to Madelung deformity?
Leri-Weill dyschondrosteosis and Turner syndrome.
136
What’s the prevalence of congenital radial head dislocation?
Bilateral or unilateral?
Two-thirds are isolated; one-third with anomalies.
137
When does congenital radial head dislocation show?
Around school age, with limited elbow motion or pain.
138
How does X-ray distinguish congenital vs. traumatic radial head dislocation?
Congenital: posterolateral, convex head; traumatic: anterior, concave head.
139
What causes congenital radioulnar synostosis?
Failed separation of radius-ulna cartilage during apoptosis.
140
What’s the family history rate in radioulnar synostosis?
20% have a positive family history.
141
What syndromes link to radioulnar synostosis?
Apert, Carpenter, Klinefelter, arthrogryposis.
142
What are clinical signs of radioulnar synostosis?
Fixed pronation and no forearm rotation.
143
What are X-ray findings in radioulnar synostosis?
Bony connection in proximal radius-ulna third.
144
What’s Type A postaxial polydactyly?
A fully formed extra digit with bone.
145
What’s Type B postaxial polydactyly?
A rudimentary soft tissue extra digit.
146
Are syndromes common in postaxial polydactyly?
No, they’re rare in postaxial cases.
147
What causes symbrachydactyly?
Vascular insufficiency disrupts finger development.
148
Is symbrachydactyly bilateral?
Rarely bilateral; usually affects one hand.
149
What features define symbrachydactyly?
Rudimentary nails, pulps, and short fingers.
150
What’s the Bilhaut-Cloquet procedure?
Reconstruction for Wassel I/II thumb duplication.
151
When is thumb duplication surgery optimal?
Between 12–18 months for functional pinch.
152
Which population has more postaxial polydactyly?
African populations, often autosomal dominant.
153
What’s the Wassel classification for?
It grades thumb duplication into seven types.
154
What’s Wassel I thumb duplication?
A split thumb tip with shared bone.
155
What’s Wassel II thumb duplication?
Two separate distal phalanges.
156
What’s the most common Wassel type?
Type IV (bifid thumb), 43% of cases.
157
What’s clinodactyly’s prevalence?
Affects 1% of people, often bilateral little fingers.
158
What’s camptodactyly’s prevalence?
Less than 1%, often bilateral little fingers.
159
What X-ray shows in camptodactyly?
Parrot beak deformity of phalanges.
160
What syndromes link to camptodactyly?
Marfan, arthrogryposis, craniofacial syndromes.
161
What surgery treats severe camptodactyly?
FDS release or checkrein ligament release.
162
What causes macrodactyly’s overgrowth?
Increased vascular or neural supply drives growth.
163
What vascular issues cause macrodactyly?
AV fistulas or Klippel-Trenaunay syndrome.
164
What neural issues cause macrodactyly?
Lipofibrohamartomas or neurofibromatosis.
165
What’s PIK3CA’s role in macrodactyly?
PIK3CA mutations cause overgrowth and malignancy risk.
166
What’s Flatt Type I macrodactyly?
Lipofibromatosis of nerves, most common type.
167
What indicates macrodactyly treatment?
Progressive deformity, function loss, or cosmetics.
168
What treats macrodactyly?
Debulking, physeal arrest, or amputation if severe.
