Congenital Hand Flashcards
A neonate is born with unilateral edema of the arm. During the ensuing day, there is worsening edema and bullae formation. Which of the following is the most appropriate next step in management of this patient?
A) Administration of intravenous antibiotics and elevation of the arm
B) Compartment release
C) Continued observation and dressing change
D) Debridement and skin grafting
E) Treatment in a hyperbaric chamber
The correct response is Option B.
Compartment release should be performed early and urgently. The other treatments above may play a role in secondary treatment. Volkmann’s ischemia is not rare and awareness of the diagnosis is important. The sentinel lesion of neonatal compartment syndrome is bullous formation on the dorsum of the hand or arm. Etiology is often in utero and can be amniotic bands, umbilical cord loops, forceps extraction, oligohydramnios, preeclampsia, and excessive maternal weight. Diastolic pressures in neonates are usually 40 mmHg or less. Small increases in compartment pressure are therefore not tolerated well. The six P’s of compartment syndrome, which include pain, paresthesias, pulselessness, pallor, paralysis, and pressure, will not be seen in the neonate. The three A’s, which precede the six P’s in children, are agitation, anxiety, and increasing analgesic requirements; and will not be seen in the neonate.
2018
A 1-year-old boy is brought to the office by his parents for evaluation and correction of the findings shown in the photograph. The patient is otherwise healthy. Which of the following techniques is most appropriate to reconstruct the apex of the web space in this patient?
A) Bilobed flap from the dorsal hand
B) Cross-finger flap
C) Full-thickness skin grafting
D) Proximally based dorsal rectangular flap
E) Split-thickness skin grafting
The correct response is Option D.
Full-thickness skin grafts are usually used to close the resultant defects of the fingers after release of congenital syndactyly. Several local dorsal flaps have been described to reconstruct the web space with differing shapes to avoid the use of skin grafts, including rectangular, a V-Y island, a dorsal flap interdigitated with a small palmar V and a dorsal V-shape. A bilobed flap has been described for treating web creep in adults, but would not routinely be used.
2018
A 4-month-old infant is brought to the office for evaluation of a unilateral, seven-fingered hand with a central index finger flanked on each side by long, ring, and little fingers, with no thumb present. Abnormal expression of which of the following controlling substances is most likely responsible for this developmental anomaly?
A) Bone morphogenetic protein
B) Fibroblast growth factor
C) Sonic hedgehog protein
D) Wingless protein
The correct response is Option C.
The infant’s described anomaly is that of a mirror hand, which is an abnormality of the anteroposterior (radioulnar) axis of limb development. Sonic hedgehog protein (SHH) is expressed in the zone of polarizing activity (ZPA) on the posterior (ulnar) surface of the developing limb bud and is the main controlling substance for this axis of development. Direct expression of SHH results in development of the ulna, the ulnar two columns of the carpus, the little finger, the ring finger, and the ulnar half of the long finger. Diffusion of SHH, or long range signaling, results in development of the radial half of the long finger and the index finger. Absence of SHH results in the development of the radius, the radial column of the carpus, and the thumb. Ectopic expression of SHH, such as with duplication of the ZPA at the anterior (radial) margin of the limb bud, results in duplication of the ulnar-sided structures found in a mirror hand.
Fibroblast growth factors (FGF) are the main controlling substances in the apical ectodermal ridge (AER) and are responsible for the proximodistal axis of limb bud development. Bone morphogenetic proteins (BMP) are expressed in the AER and are also thought to be involved in digital separation, the lack of which leads to syndactyly. Wingless proteins (WNT) are also expressed in the AER, but it is the WNT signaling pathway from the dorsal surface of the limb bud that controls the dorsoventral axis of limb development. Dorsal ectodermal WNT also maintains SHH in the ZPA such that lack of WNT leads to lack of ulnar ray development. This is contrary to the ectopic expression of SHH leading to duplication of the ulnar rays in mirror hand. Fibroblast growth factors, bone morphogenetic proteins, and wingless proteins are not principal controlling substances for the anteroposterior (radioulnar) axis of development of the limb.
2018
A 6-month-old boy is brought to the office with a Blauth type IV (pouce flottant) thumb deficiency. Reconstruction with pollicization is planned. Which of the following is the most appropriate new function of the first palmar interosseous muscle?
A) Abductor pollicis brevis
B) Abductor pollicis longus
C) Adductor pollicis
D) Extensor pollicis longus
E) Flexor pollicis brevis
The correct response is Option C.
The most appropriate new function of the first palmar interosseous muscle is the adductor pollicis.
Thumb deficiencies can be categorized according to the Blauth classification, ranging from hypoplasia (type I) to complete absence (type V). In deficiencies of type IIIB and greater, pollicization of the index finger is the recommended treatment.
In pollicization, the index finger is transferred on its neurovascular bundle and a new thumb carpometacarpal (CMC) joint is created using the metacarpophalangeal joint of the index finger. The tendons and muscles of the index finger are used to recreate functions of the new thumb. The extensor digitorum communis is used for the abductor pollicis longus, the dorsal interosseus becomes the abductor pollicis brevis, and the palmar/volar interosseous becomes the adductor pollicis. The extensor indicis proprius is used for the extensor pollicis longus. The flexor tendon is not typically disturbed.
2018
A 2-year-old boy is treated for congenital constriction band of the left upper extremity with distal edema. The child undergoes excision of 50% of the circumferential constriction band with direct closure. This intervention is most likely to have which of the following effects on the edema of the distal limb?
A) Gradual improvement during childhood development
B) Gradual worsening during childhood development
C) Significant improvement within a few weeks of surgery
D) Significant worsening during childhood development
E) No effect
The correct response is Option C.
Congenital constriction band syndrome is a sporadic condition with an incidence varying from 1:1200 to 1:15,000 live births. There is a significant predilection for the upper extremities and distal limbs. The two main objectives for the treatment of congenital constriction band syndrome are improvement of function and improvement of cosmetic appearance. Different surgical techniques, such as Z-plasty, have been described and used for decades; however, direct closure after the excision of the constricting band is a simple yet effective treatment.
With complete circumferential constriction bands, it is recommended that a two-stage correction approach be used. At the first operation, one-half of the circumference is excised; the other half can be excised after 3 to 6 months. This will avoid any problems to the distal circulation in the limb, which may already be compromised. Edema, when present, will significantly improve within a few weeks of the first surgery.
2018
A 14-month-old girl is evaluated for surgical management of the condition shown in the photograph. Which of the following is the most appropriate classification of this congenital difference?
A) Duplication
B) Failure of differentiation
C) Failure of formation
D) Overgrowth
E) Undergrowth
The correct response is Option C.
The image shown is a patient with a typical cleft hand, or ectrodactyly. This is classified as a Swanson type I (failure of formation) congenital difference of the upper extremity. This deformity is caused by a longitudinal growth deficiency of one or more central digits. This condition may have a genetic underpinning and is most commonly inherited in autosomal dominant fashion with approximately 70% penetrance.
Ectrodactyly presents with significant heterogeneity. Many patients with cleft hand do not require any type of surgical management. The most important determinants of surgical management are establishment of an appropriate thumb to index webspace for gripping and grasping and release of syndactyly. Surgical management includes elevation of skin flaps, transposition of the index finger to the ulnar side of the cleft, and creation of a web space between the thumb and index finger.
Cleft hand is classified with the Thumb-Index Classification of Central Deficiency proposed by Manske. This generally guides the treatment approach in conjunction with management of syndactyly. A myriad of techniques have been employed based upon the severity of the webspace contraction and the presence of syndactyly adjacent to the cleft.
2018
During embryonic limb development, limb bud outgrowth is controlled by which of the following families of signaling proteins?
A) Bone morphogenetic proteins
B) Fibroblast growth factor
C) Retinoic acid
D) Sonic hedgehog (SHH)
E) Wingless-type proteins
The correct response is Option B.
The most appropriate answer is fibroblast growth factor. Limb bud development begins at the fourth week of gestation via an outgrowth of lateral plate somatic mesoderm covered by ectoderm. The lower limb bud forms a few days after the upper limb and is formed opposite of the L3-5 vertebrae. The cells at the tip of the limb bud ectoderm thicken to form the apical ectodermal ridge (AER). Fibroblast growth factor 10 (FGF10) from the mesenchyme induces the formation of the AER, which produces FGF8. This signaling induces mitosis of the underlying cells leading to limb elongation.
A group of mesenchymal cells on the posterior of the limb bud form the zone of polarizing activity (ZPA). Cells from the ZPA secrete sonic hedgehog protein, which acts as a short range signaling molecule. The ZPA is responsible for the anteroposterior axis formation of the limb bud.
Retinoic acid, a derivative of vitamin A, plays a role in the proximal-distal development of the limb but is not the primary signaling molecule. The precise mechanism and action of retinoic acid is debated. A retinoic acid gradient is necessary for normal limb development. Retinoic acid may act as an inhibitor of FGF8, which then allows forelimb budding to occur. Retinoic acid is not thought to be involved in hindlimb formation.
During limb development, the digits are initially connected by tissue that regresses via apoptosis. Apoptosis of interdigital tissue is dependent on BMP signaling under the influence of sonic hedgehog from the ZPA. Proteins from the wingless type family, especially Wnt7a, are responsible for the dorsal-ventral patterning of the overlying ectoderm. The presence of Wnt7a is necessary to dorsalize the limb.
2017
A 3-month-old male infant is evaluated for polydactyly and mirror hand. Which of the following is the most likely genetic anomaly in this patient?
A) Engrailed-1 (EN1)
B) Fibroblast growth factor-2 (FGF2)
C) LIM homeobox transcription factor 1-beta (LMX1B)
D) Sonic hedgehog (SHH)
E) Wingless type (WNT)
The correct response is Option D.
This patient presents with polydactyly and mirror hand. The most likely genetic anomaly is in sonic hedgehog (SHH).
Limb development is controlled by signaling pathways that are located within 3 different signaling centers. These control the proximal-distal, anterior-posterior, and dorsal-ventral axes of limb development.
The limb develops in a proximal-distal direction, from shoulder to wrist, which is controlled by the apical ectodermal ridge (AER), a thickened layer of ectoderm over the limb bud. Fibroblast growth factors secreted within the AER signal the underlying mesoderm to differentiate. Disruption of the AER results in truncation of the limb.
Growth in the anterior-posterior (radioulnar) axis is determined by the zone of polarizing activity (ZPA). This is located in the posterior margin of the limb bud. The sonic hedgehog protein (SHH) acts to signal development of the limb into radial and ulnar aspects. Alterations in this pathway can result in mirror duplication.
Dorsal-ventral limb development is signaled by the Wnt signaling pathway, which produces a transcription factor, Lmx-1 that induces the development of dorsal structures. In the ventral portion of the limb, the Engrailed-1 gene product blocks the Wnt pathway, leading to ventralization.
A variety of other transcription factors encoded by Hox and T-Box genes also govern limb and organ development, and alterations in these can give rise to various developmental differences.
2017
A 3-year-old boy is scheduled to undergo the first stage of separation of syndactyly of the right hand. Photographs are shown. Which of the following anatomical structures is most likely to limit how far the digits can be separated proximally?
A) Artery
B) Extensor tendon
C) Flexor tendon
D) Nerve
E) Vein
The correct response is Option A.
Digital veins, due to their larger number and relative redundancy, do not normally limit which tissues can be separated to what level. Division of one branch of the digital artery is not normally a problem when only two digits are involved in syndactyly; the digital artery on the unaffected side is normally sufficient to perfuse the digit. For a central digit when three or more digits are involved, dissection must either stop at the bifurcation of the artery, or revascularization, such as with a vein graft, must be done.
The digital nerve often exists as a single unit at least partially down the length of the joined fingers, but it can be separated into two proper digital units with intrafascicular dissection to a level proximal to the neo-web space.
Flexor and extensor tendons are not involved in syndactyly.
2017
A 7-month-old male infant with complete syndactyly is evaluated for surgical release. Which of the following is the most appropriate technique for reconstruction of the web space?
A) Coverage with a distally based zigzag flap
B) Coverage with a dorsal rectangular flap
C) Coverage with a volar triangular flap
D) Full-thickness skin grafting
E) Split-thickness skin grafting
The correct response is Option B.
The most appropriate technique for reconstruction of the web space in patients with complete syndactyly is coverage with a dorsal rectangular flap.
In patients with compete syndactyly, separation does not typically result in sufficient skin to resurface both digits entirely. Reconstruction of the web space is a priority and is typically achieved with a proximally-based dorsal rectangular flap. Interdigitating skin flaps are designed, and skin grafts are placed to replace skin deficiency. Full-thickness skin grafts are preferred to split-thickness skin grafts because of the decreased likelihood of contracture; however, these grafts are not typically placed in the web space.
2016
A 3-month-old boy is brought for evaluation because of bilateral simple syndactylies between the long and ring fingers. During which gestational age range did this developmental anomaly most likely occur?
A) Days 0-15
B) Days 20-35
C) Days 40-55
D) Days 65-80
E) Days 85-100
The correct response is Option C.
Syndactyly is the most common congenital limb malformation. Digital separation is the result of distal to proximal apoptosis, likely mediated by bone morphogenic proteins (BMP) signaling TGF-beta. Overexpression of BMP inhibitors and persistent fibroblast growth factor (FGF) function have been found to lead to syndactyly.
The exact dates of digital separation vary by publication, but occur approximately between days 44 and 54. Limb buds appear by day 26, and a hand paddle by day 33. By day 56, the phalangeal tips are ossified.
2016
A 3-month-old male infant is brought to the clinic by his parents for evaluation of craniofacial and hand anomalies. Genetic testing confirms an FGFR2 abnormality consistent with Apert syndrome. Which of the following hand anomalies is most likely in this infant?
A) Camptodactyly
B) Clinodactyly
C) Ectrodactyly
D) Macrodactyly
E) Syndactyly
The correct response is Option E.
The hand anomaly most associated with Apert syndrome is syndactyly.
Apert syndrome, or acrocephalosyndactyly, is a syndrome resulting from a defect in chromosome 10q, the site of the fibroblast growth factor-2 receptor. This syndrome consists of coronal craniosynostosis, mid face hypoplasia with retrusion, and syndactylies of the hands and feet. These may be type I (syndactyly of digits 2–4 with a free thumb; “spade hand”), type II (syndactyly of digits 2–4 with a simple syndactyly of the thumb; “mitten hand”), or type III (complex syndactyly of all digits with complex thumb syndactyly; “rosebud hand”).
The other choices are not typically associated with Apert syndrome. Camptodactyly is a fixed-flexion deformity of the proximal interphalangeal (PIP) joint(s), most commonly the little finger. Macrodactyly involves the localized overgrowth of bone and soft tissue. Clinodactyly is congenital deviation of a digit in the radioulnar plane. Ectrodactyly refers to a split-hand/split-foot malformation.
2015
A 52-year-old man is evaluated because of a congenital deficiency of the upper extremity. A photograph is shown. This patient’s developmental abnormality most likely occurred during which of the following periods of gestation?
A) 0–4 weeks
B) 5–8 weeks
C) 9–13 weeks
D) 14–18 weeks
E) 19–23 weeks
The correct response is Option B.
The most likely period of time during gestation for this abnormality is 31 to 45 days.
This patient presents with transverse deficiency of the upper limb (phocomelia). This can result from abnormal development of the limb with an interruption in longitudinal growth.
The limb develops with formation of a limb bud at 26 days after gestation, which rapidly enlarges with growth of the embryo until approximately 47 days. At around 52 to 53 days after gestation, the fingers are separate. Embryogenesis is complete by 8 weeks, and all limb structures are present.
Limb development is controlled by signaling pathways that are located within three different signaling centers. These control the proximal-distal, anterior-posterior, and dorsal-ventral axes of limb development.
The limb develops in a proximal-distal direction, from shoulder to wrist, which is controlled by the apical ectodermal ridge (AER), a thickened layer of ectoderm over the limb bud. Fibroblast growth factors secreted within the AER signal the underlying mesoderm to differentiate. Disruption of the AER results in truncation of the limb.
Growth in the anterior-posterior (radioulnar) axis is determined by the zone of polarizing activity (ZPA). This is located in the posterior margin of the limb bud. The sonic hedgehog protein acts to signal development of the limb into radial and ulnar aspects. Alterations in this pathway can result in mirror duplication.
Dorsal-ventral limb development is signaled by the Wnt signaling pathway, which produces a transcription factor, LMX1 that induces the development of dorsal structures. In the ventral portion of the limb, the EN1 gene product blocks the Wnt pathway, leading to ventralization.
A variety of other transcription factors encoded by Hox and T-Box genes also govern limb and organ development, and alterations in these can give rise to various developmental differences.
Most limb abnormalities occur during the period of 4 to 8 weeks. In this case, the transverse deficiency likely occurred earlier in the process of limb outgrowth, while abnormalities of the digit would have taken place towards the end of this period.
A 1-month-old male newborn is brought to the office by his parents for evaluation of complete simple syndactyly between the second and third toes of the left foot. The parents are concerned about the newborn’s development and ability to achieve normal ambulation. Which of the following is the most appropriate intervention at this time?
A) Surgical correction is optional but not necessary because there is no functional deficit
B) Surgical correction with a dorsal local flap and ligament reconstruction
C) Surgical correction with a dorsal local flap only
D) Surgical correction with a dorsal local flap, skin grafting, and ligament reconstruction
E) Surgical correction with skin grafting only
The correct response is Option A.
Syndactyly of the toes most commonly affects the second and third digits of the lower extremities. Various levels of webbing are possible, from partial to complete. In general, syndactyly is a condition that is primarily cosmetic and rarely requires treatment. If surgery is desired, it should be postponed until the child is old enough to take part in the decision-making process. Surgery is often performed to avoid emotional and psychological problems.
Surgical correction most commonly consists of a dorsal rectangular flap and simultaneous full-thickness or split-thickness skin grafts. However, some surgeons are performing syndactyly repair of both the upper and lower extremities with dorsal local flaps and allowing the skin defects to epithelialize in order to avoid donor-site morbidity of a skin graft. If there is only soft-tissue involvement, ligament reconstruction is not needed.
2014
A 12-month-old male infant is brought to the office for evaluation of a small right thumb. Physical examination shows instability of the metacarpophalangeal joint and hypoplasia of the first web space. The carpometacarpal joint is stable. The patient has difficulty moving the thumb. Which of the following is the next best step in management?
A) Free toe transfer
B) Metacarpal lengthening
C) Opponensplasty
D) Pollicization
E) Continued observation
The correct response is Option C.
This patient presents with a Blauth Grade 2 or 3A thumb hypoplasia. Surgical management is warranted and includes treatment of the absent or hypoplastic thenar musculature with opponensplasty; release of the first web space; and management of MCP instability.
Pollicization is reserved for Blauth Grade 3B or more severe deficiencies. The distinction between a Blauth 3A and 3b hypoplastic thumb is determined by the stability of the CMC joint.
Blauth classification of Thumb Hypoplasia:
2019
A 2-month-old infant is brought to the office for evaluation of bilateral complex syndactyly of the hands and feet. Which of the following is the most likely gene involved?
A) Engrailed-1 (EN1)
B) Fibroblast growth factor receptor-2 (FGFR2)
C) LIM Homeobox transcription factor-1 beta (LMX1B)
D) Sonic hedgehog (SHH)
E) Wingless type (Wnt)
The correct response is Option B.
This patient presents with complex syndactyly of hands and feet consistent with Apert syndrome. This is an autosomal dominant condition that can be caused by mutation in the fibroblast growth factor receptor-2 gene.
Limb development is controlled by signaling pathways that are located within three different signaling centers. These govern the proximal-distal, anterior-posterior, and dorsal-ventral axes of limb development.
The limb develops in a proximal-distal direction, from shoulder to wrist, which is controlled by the apical ectodermal ridge (AER), a thickened layer of ectoderm over the limb bud. Fibroblast growth factors secreted within the AER signal the underlying mesoderm to differentiate. Disruption of the AER results in truncation of the limb.
Growth in the anterior-posterior (radioulnar) axis is determined by the zone of polarizing activity (ZPA). This is located in the posterior margin of the limb bud. The sonic hedgehog protein (SHH) acts to signal development of the limb into radial and ulnar aspects. Alterations in this pathway can result in mirror duplication.
Dorsal-ventral limb development is signaled by the Wnt signaling pathway, which produces a transcription factor, LMX1B, that induces the development of dorsal structures. Deficiency in LMX1B has been associated with nail-patella syndrome. In the ventral portion of the limb, the Engrailed-1 gene product blocks the Wnt pathway, leading to ventralization.
A variety of other transcription factors encoded by Hox and T-Box genes also govern limb and organ development, and alterations in these can give rise to various developmental differences.
2019
Which of the following techniques is most commonly used for reconstruction of a Blauth IIIB thumb hypoplasia in the United States?
A) Great toe to thumb transfer
B) Index pollicization
C) Metacarpophalangeal (MCP) joint stabilization with opponensplasty
D) Second toe to thumb transfer
E) Toe wrap around transfer
The correct response is Option B.
Blauth classification of Thumb Hypoplasia:
The most severe forms of thumb hypoplasia (types IIIB, IV, and V) require amputation of the existing thumb and reconstruction, most commonly by index pollicization.
2019
A 2-year-old male infant presents with a congenital deformity of the ring finger. A photograph and x-ray study are shown. The patient’s parents report that the condition limits his ability to make a full fist but is otherwise painless. Which of the following is the most likely diagnosis in this patient?
A) Amniotic band syndrome
B) Camptodactyly
C) Congenital trigger finger
D) Macrodactyly
E) Syndactyly
The correct response is Option A.
Amniotic band syndrome (ABS) has an incidence of 1/1200 to 1/15,000 births. Some congenital anomalies have been associated with ABS including cleft palate, imperforate anus, equinovarus, and body wall defects.
The etiology of ABS has two theories. The intrinsic defect theory endorses genetic abnormalities which lead to mesenchymal hypoplasia and scarring. The extrinsic theory endorses amniotic tissue which entangles fetal parts leading to constriction.
Constriction varies leading to a spectrum of clinical manifestations from skin dimpling to digital amputation. Neurovascular injury can manifest as peripheral nerve palsy, lymphedema and arterial insufficiency. Syndactyly is common, and acrosyndactyly is pathognomonic of ABS. The Patterson classification system has four subtypes. The first is a simple constriction ring. The second has a constriction ring that affects the digit distal to the ring, with or without lymphedema. The third consists of constriction rings with acrosyndactyly. The fourth is characterized by amputation at any level.
Camptodactyly is defined as a painless and progressive non-traumatic contracture of the proximal interphalangeal (PIP) joint. It affects around 1% of the population and the great majority of the cases are extremely mild and asymptomatic. The cause of the contracture is controversial. There have been descriptions of malformations of the superficial flexor of the fingers, lumbrical muscles, and the transverse and oblique retinacular ligaments. There may also be alterations to the configurations of the PIP joint.
Congenital trigger finger differs from congenital trigger thumb. Congenital trigger finger is rare and presents more commonly in the ulnar digits with associated malformations of the superficial and deep flexors. It presents with sporadic locking. Release of the A1 pulley alone is not adequate, with tenoplasty of the chiasm and partial opening of the A2 pulley generally necessary.
Syndactyly is a variable fusion between two adjacent fingers, and is one of the most common congenital
deformities, occurring in 1:2000 live births.
Classification includes:
Simple: fusion only through the skin
Complex: bone connection.
Complete: the entire commissure is involved, including the nail bed
Incomplete: the nail bed is not involved.
Complicated: involvement of vascular tissues, tendons or nerves.
It can occur separately or as a manifestation of a syndrome, such as Streeter, Apert or Poland, in which the severity of the syndactyly is more significant.
Macrodactyly is a congenital overgrowth disorder and represents 0.9% of upper extremity congenital anomalies. Digital enlargement involves all tissue types and maintains patterns of growth and anatomic relationships within the affected portion of the hand.
The term “macrodactyly” is reserved for nonsyndromic, congenital enlargement of a digit or digits that occurs in isolation without associated limb hemihypertrophy or vascular anomaly.
Which of the following failures in embryologic development is most likely to have caused the deformity pictured in the photographs shown?
A) Differentiation of the zone of polarizing activity
B) Formation of the apical ectodermal ridge
C) Inhibition by en-1
D) Longitudinal formation
E) Programmed cell death
The correct response is Option E.
The hand plate initially forms with webbed digits. In order to have separate fingers, the interdigital tissue must undergo programmed cell death/apoptosis. Bone morphogenetic protein (BMP) plays an essential role in this process. A complex interplay creates failure of longitudinal formation (i.e., radial club hand). Removal of the apical ectodermal ridge (AER) results in limb truncation. The zone of polarizing activity (ZPA) is present in the posterior aspect of the developing upper limb and helps direct the anteroposterior axis (radial-ulnar axis). Sonic hedgehog (SHH) is the critical signaling factor. ZPA transplantation or excess SHH results in mirror hand deformity. The dorsoventral axis is another pathway critical for appropriate limb development. The WNT7A signaling molecule is expressed in the developing upper limb dorsal ectoderm, activating the LIM homeodomain, resulting in the expression of LMX1B transcription factor from the dorsal mesenchyme, whereas the ventral ectoderm induces the expression of en-1. These signaling factors are necessary for the formation of dorsal versus palmar structures of the hand.
2020
A 6-month-old male infant presents with bilateral radial longitudinal deficiency and thumb hypoplasia. X-ray study is shown. Which of the following studies is most likely to rule out Fanconi anemia in this patient?
A) Bone marrow biopsy
B) Chromosomal breakage testing
C) Complete blood count with differential
D) Peripheral blood smear
E) Renal ultrasonography
The correct response is Option B.
All children with radial longitudinal deficiency (RLD) should undergo a thorough physical examination because of the frequency of associated syndromes. Common conditions associated with RLD include thrombocytopenia-absent radius (TAR) syndrome, Holt-Oram syndrome, VACTERL syndrome and Fanconi anemia.
Thrombocytopenia-absent radius (TAR) syndrome is an autosomal recessive disorder characterized by an absent radius with a relatively normal thumb. Holt-Oram syndrome is an autosomal-dominant disorder in which RLD is accompanied by either an atrial or ventricular cardiac septal defect. Fanconi anemia is an autosomal-recessive pancytopenia, once invariably fatal, that is now routinely treated with bone marrow transplantation. One should consider further screening with spinal x-ray studies, cardiac echocardiography, renal ultrasonography, and complete blood count.
Because children with Fanconi anemia often do not manifest aplastic anemia on routine blood testing until after age 3 years, it is also recommended that patients with RLD undergo a chromosomal breakage test for earlier detection of this potentially fatal disease. Routine genetic counseling is also recommended.
A peripheral blood smear and bone marrow biopsy would not be helpful in making this diagnosis.
2020
An 18-month-old male infant with an isolated Blauth Type IV thumb (floating) is scheduled to undergo pollicization of the index finger. A photograph is shown. The index finger metacarpal head becomes which of the following structures in the pollicized thumb?
A) Articular surface of the carpometacarpal (CMC) joint
B) Distal articular surface of the proximal interphalangeal (PIP) joint
C) Proximal articular surface of the PIP joint
D) Scaphoid
E) Trapezoid
The correct response is Option A.
Thumb pollicization is a challenging yet functionally rewarding procedure. It is indicated for Blauth Type IIIB or higher thumbs. If done correctly, this technique can greatly enhance the function of the hand and provide a strong, stable thumb analog for grip and pinch. The procedure involves many stages and is technically demanding. Although beyond the scope of this description, the procedure requires shortening of the index finger metacarpal and repositioning of the metacarpal head in hyperextension against the preserved metacarpal base. Thus, the index metacarpal phalangeal joint becomes the new thumb’s carpometacarpal joint, the index proximal interphalangeal joint becomes the new thumb’s metacarpophalangeal joint, and the index distal interphalangeal joint becomes the new thumb’s interphalangeal joint.
2020
A 12-month-old boy comes to the office for evaluation of a congenital thumb deformity. A photograph is shown. Which of the following is the most appropriate management of the thumb?
A) First metacarpal distraction osteogenesis
B) First web space deepening
C) Flexor digitorum superficialis opponensplasty
D) Free great toe transfer
E) Index finger pollicization
The correct response is Option E.
This patient has a type IV (floating thumb or pouce flottant) thumb hypoplasia best managed with thumb ablation and index finger pollicization. Thumb hypoplasia can range from a minor decrease in size to complete absence. Thumb hypoplasia may also be associated with VACTERL (vertebral abnormalities, anal atresia, cardiac abnormalities, tracheoesophageal fistula or esophageal atresia, renal agenesis and dysplasia, and limb defects), TAR syndrome, Fanconi anemia, and Holt-Oram syndrome. Given the possible association with these conditions, a workup of all potentially affected organ systems should be performed. This includes a renal ultrasound, an echocardiogram, spine x-ray studies, a complete blood count, and a chromosomal challenge test.
Thumb hypoplasia may occur in an isolated fashion or in combination with radial hypoplasia, as seen in this case. The most important and difficult distinction is between types IIIa and IIIb hypoplastic thumbs. A type IIIa thumb has a stable thumb carpometacarpal (CMC) joint, whereas a type IIIb thumb does not. If the child uses the thumb for integrated pinch, the CMC joint is deemed stable. If the thumb is bypassed in favor of scissor pinch between the index and middle fingers, the CMC joint is either unstable or absent; in this case, a pollicization is recommended.
A free great toe transfer is not indicated in children with thumb hypoplasia because the existing thumb CMC is not stable and pollicization would provide a better functional outcome. Flexor digitorum superficialis or abductor digiti minimi opponensplasty are both options for thumb hypoplasia reconstruction in the presence of a stable CMC joint. A first webspace deepening is typically combined with opponensplasty and metacarpophalangeal joint stabilization in children with reconstructible hypoplastic thumbs, but not for children undergoing pollicization. The patient in the image does not have a first metacarpal, and therefore cannot undergo distraction osteogenesis.
2021
A 4-month-old male infant is brought to the office with the multiple extremity findings shown in the photographs. Which of the following additional clinical findings is most commonly seen with this condition?
A) Absence of the sternocostal head of the pectoralis major
B) Bilateral symmetric anomalies
C) Clubfoot
D) Craniosynostosis
E) Hematopoietic changes
The correct response is Option C.
This child has constriction ring syndrome (CRS). CRS is a rare occurrence, with the incidence reported from 1 in 1200 to 15,000 births. CRS frequently affects multiple extremities asymmetrically, with an average of three extremities involved, most often at the distal aspect of the extremity. Several characteristics are most often seen in the affected extremities including constriction rings, amputations, lymphedema distal to the ring, and acrosyndactyly (digits are fused distally, but proximally have fenestrations as fusion occurred after apoptosis in utero). Amputation or hypoplasia is usually seen distal to the ring, whereas the proximal aspect is intact and usually well-formed. CRS affecting the hands most frequently affects the index, middle, and ring fingers. Associated anomalies include syndactyly, oligodactyly, clubfoot, limb absences, body-wall defects (e.g., gastroschisis), and craniofacial anomalies, particularly facial clefts.
Symbrachydactyly, which is associated with Poland syndrome, is usually present in one limb. There is true hypoplasia of the affected extremity with absent or rudimentary digits with nubbins and frequent syndactyly. Symbrachydactyly usually impacts the central digits. Poland syndrome is defined by the absence of the sternocostal head of the pectoralis major.
Hematopoietic changes can be seen in radial hypoplasia. Fanconi anemia and thrombocytopenia (thrombocytopenia absent radius syndrome) are both associated with radial hypoplasia.
Children with Apert syndrome (acrocephalosyndactyly) have bilateral relatively symmetric complex syndactyly, symphalangism, and craniosynostosis.
2022
A 5-year-old boy is evaluated because of the deformity of the left hand shown in the photograph. Three months ago, the boy fell from a chair, and his parents report that he has been unable to extend his thumb. X-ray studies obtained by his pediatrician showed no fracture or dislocation. Physical examination today discloses a palpable mass at the volar aspect of the metacarpophalangeal joint flexion crease. Which of the following is the most appropriate treatment for this patient?
A) Corticosteroid injections
B) Extensor tendon repair
C) Manipulation with anesthesia
D) Percutaneous transection
E) Surgical incision
The correct response is Option E.
The cause of a pediatric trigger thumb is considered congenital by some and acquired by others. Because children hold their thumb in the palm naturally, the flexed position of the interphalangeal joint is often not observed by the family until after a fall or injury that prompts a closer evaluation. The Notta nodule is often mistaken for a bony mass.
Although some authors have recommended a period of splinting or observation, the majority of pediatric trigger thumbs presenting as locked in flexion require surgical release since the rate of spontaneous resolution is low. For those cases that did resolve with splinting and therapy or observation alone, it took many months to years to achieve resolution.
Open surgical intervention is performed with release of the A1 pulley and sometimes a portion of the oblique pulley. The Notta nodule at the time of surgical release is shown in the photograph.
Percutaneous release, although used with success in adult trigger fingers, is not appropriate for children because of the close proximity of the neurovascular structures.
There is no literature addressing the treatment of pediatric trigger thumb with steroid injections; therefore, it is not recommended.
Manipulation with anesthesia might be an appropriate treatment for a dislocation, which this child does not have.
2023
A 6-month-old female infant is brought to the office because of cleft-type symbrachydactyly affecting the left hand. X-ray studies are shown. Which of the following is the most appropriate recommendation regarding a prosthesis for this patient?
A) The child currently has no functional need for a prosthesis
B) Fit the child with an activity-specific prosthesis immediately
C) Fit the child with an articulating finger prosthesis immediately
D) Schedule the child for skeletal augmentation prior to fitting for a prosthesis
E) Schedule the child for targeted muscle reinnervation prior to fitting for a prosthesis
The correct response is Option A.
In contrast to traumatically injured patients, children with upper limb differences use prosthetics more for social purposes than functional ones. This is because the prosthesis effectively covers up the sensation of the terminal limb and, in effect, interferes with the child’s use of the limb. Furthermore, the prosthetic socket, by blocking sensory feedback, may limit the development of functional strategies. For this reason, the rejection rate is high and there is no functional difference seen in patients who use a prosthesis versus patients who do not use one. For children and families who choose to use a prosthesis, the key timeline for fitting is to provide a passive (not activity-specific or articulating) prosthesis when the child has obtained the ability to sit balanced, usually at 9 months of age. Children fitted after 2 years of age have an even higher rate of rejection of the prosthesis.
Skeletal augmentation is not required for this patient to be eligible for a prosthetic. Some children may present with nonfunctional anatomy that can be removed, although families usually choose not to. The prosthetic fitting can be performed to accommodate these parts. If the child continues to use a prosthesis, nonfunctional parts can be removed later in life to allow for more advanced prosthetic fitting.
Targeted muscle reinnervation is a surgical technique used to enhance control of myoelectric prosthetics for patients after traumatic amputation. It is not an appropriate technique for a congenital limb difference.
2023
