The Journal of Bone and Joint Surgery (American) 85:1564-1576 (2003)
© 2003 The Journal of Bone and Joint Surgery, Inc.
Upper-Extremity Congenital Anomalies
Scott H. Kozin, MD
Scott H. Kozin, MD
Shriners Hospitals for Children, 3551 North Broad Street, Philadelphia, PA 19140. E-mail address: skozin{at}shrinenet.org
The author did not receive grants or outside funding in support of his research or preparation of this manuscript. He did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the author is affiliated or associated.
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Introduction
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•Embryogenesis of the upper extremity occurs between the fourth and eighth week of gestation and is guided by signaling centers within the developing limb bud.
•Certain upper-limb anomalies are associated with concomitant systemic disorders, whereas others occur in isolation or in combination with other musculoskeletal problems.
•Radial deficiency is associated with Holt-Oram syndrome, thrombocytopenia-absent-radius syndrome, VACTERL association (vertebral abnormalities, anal atresia, cardiac abnormalities, tracheoesophageal fistula, esophageal atresia, renal defects, radial dysplasia, lower-limb abnormalities), and Fanconi anemia.
•A chromosomal challenge test is currently available to detect Fanconi anemia prior to the onset of aplastic anemia, which allows additional time to search for a suitable bone-marrow donor.
•Postaxial polydactyly is frequently inherited in an autosomal dominant pattern but has a variable penetrance pattern. A small nubbin or rudimentary postaxial element can be safely removed by tying its base in the nursery.
Congenital anomalies affect 1% to 2% of newborns, and approximately 10% of those children have upper-extremity abnormalities
1,2 . The anomalies require an accurate diagnosis and communication of relevant information to the family. The era of managed care has changed the patterns of referral of children with limb anomalies. Frequently, the child is referred directly to the orthopaedic surgeon by the pediatrician. This referral pattern has placed an added burden on the orthopaedic surgeon, who may have to deal with an anomaly for which there has not been a sufficient workup and counsel parents who are desperate for information. The clinician must possess a basic understanding of embryogenesis, limb formation, and inheritance patterns to relay relevant knowledge to the family. Certain upper-extremity anomalies occur in isolation, whereas others are associated with systemic conditions. These associated disorders often take precedence over the limb anomaly and must be assessed with appropriate diagnostic testing. The purpose of this review is to provide the practicing orthopaedic surgeon with an update on congenital anomalies of the upper extremity and to highlight those anomalies that require referral for systemic evaluation.
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Classification of Limb Anomalies
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There are numerous systems for classification of upper-limb anomalies on the basis of embryology, teratologic sequencing, and/or anatomy. Each proposal had merit at the time of its inception, although many systems became outdated as our understanding of limb development and genetics was expanded
3,4 . Embryologic classification defines the defect according to the malformation during limb development. Teratologic sequencing grades congenital anomalies according to the severity of expression. Varying degrees of damage and expression within the limb lead to variable phenotypes. Classifying or ranking congenital anomalies according to their severity of expression is popular because the extent of the pathology often determines function and provides a basis on which to guide treatment. An example of teratologic sequencing is classification of thumb hypoplasia into five types of increasing severity
5-7 . Anatomical classification schemes provide useful descriptive analyses and often offer therapeutic guidelines for treatment based on pathoanatomy.
The most widely accepted classification of congenital limb anomalies was proposed by Frantz and O'Rahilly
8 and presented by Swanson
9 . This work eliminated much of the confusing Greek and Latin terminology and has been accepted by the American Society for Surgery of the Hand, the International Federation of Societies for Surgery of the Hand, and the International Society for Prosthetics and Orthotics. This system defines the anomalies according to the embryonic failure during development and relies on the clinical diagnosis for categorization. Each limb malformation is classified according to the most predominant anomaly and is placed into one of seven categories (
Table I ). Different clinical presentations of similar categories of embryonic failures are explained by varying degrees of damage within the organization of the limb mesenchyme.
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Embryology Update
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Embryogenesis of the upper extremity commences with formation of the upper-limb bud on the lateral wall of the embryo four weeks after fertilization. Eight weeks after fertilization, embryogenesis is complete and all limb structures are present
3,10,11 . The majority of congenital anomalies of the upper extremity occur during this period of rapid limb development.
Animal models have been used to dissect and manipulate the crucial signaling centers that affect limb development and orientation
10,12,13 . Three signaling centers that control different aspects of limb development have been discovered: the apical ectodermal ridge, the zone of polarizing activity, and the Wingless-type (Wnt) signaling center (
Table II )
3,4,10,11 . The apical ectodermal ridge is a thickened layer of ectoderm that condenses over the limb bud and acts as a signaling center to guide the underlying mesoderm to differentiate into appropriate structures
3,11 . The apical ectodermal ridge is obligated for limb development in a proximal-to-distal direction and is responsible for interdigital necrosis, which separates the webbed hand. The zone of polarizing activity resides within the posterior margin of the limb bud and functions as a signaling center for anterior-to-posterior (radioulnar) limb development
3,13 . The signaling molecule necessary for limb orientation is the sonic hedgehog protein
13 . The Wnt signaling center resides in the dorsal ectoderm and secretes factors that induce the underlying mesoderm to adopt dorsal characteristics
12 . This center mediates the development of dorsal-to-ventral axis configuration and alignment of the limb with a dorsal orientation (dorsalization). The apical ectodermal ridge, zone of polarizing activity, and Wnt pathway all function in a coordinated effort to ensure proper limb-patterning and growth during embryogenesis
3 . Abnormalities within one signaling center indirectly prohibit adequate functioning of the other two remaining centers and affect limb formation.
Certain limb anomalies have been directly related to alterations in these signaling centers. Removal of the apical ectodermal ridge during embryogenesis yields a truncated limb similar to a congenital amputation
11 . Furthermore, failure of the apical ectodermal ridge prohibits longitudinal interdigital necrosis between the digits and results in syndactyly. Transplantation of the zone of polarizing activity (or sonic hedgehog signaling protein) to the anterior part of the developing chick limb bud results in duplication of the elements along the radioulnar axis
11,13 . This misplacement of the signaling center or molecule offers a plausible explanation for the rare mirror hand deformity. Finally, inactivation of the Wnt pathway prevents dorsalization of the mouse limb and results in ventral pads on both sides of the foot
12 .
During the period of embryogenesis, other organ systems are developing and maturing as well. An error during limb formation can also disturb formation of these other systems. Certain upper-limb anomalies are associated with concomitant systemic disorders. Other limb anomalies occur in isolation or in combination with other musculoskeletal problems. Discrimination between the various types of anomalies by the evaluating physician is important. Many of the systemic conditions are more consequential than the limb anomaly and require accurate evaluation to treat life-threatening problems, such as cardiac anomalies. Conversely, an extensive workup for an anomaly that is not associated with systemic conditions (e.g., a transverse deficiency) is unnecessary and causes financial and emotional strain on the family.
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Radial Deficiency
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One of the classic anomalies associated with systemic conditions is radial deficiency, which affects the preaxial border of the limb
14,15 . The degree of preaxial deficiency can range from mild thumb hypoplasia to complete absence of the radius (
Table III )
16 . Irrespective of the degree of expression, all forms warrant systemic evaluation for syndromes or associations. Holt-Oram syndrome, thrombocytopenia-absent-radius syndrome, VACTERL association (vertebral abnormalities, anal atresia, cardiac abnormalities, tracheoesophageal fistula, esophageal atresia, renal defects, radial dysplasia, and lower-limb abnormalities), and Fanconi anemia are the primary concerns
15 . The principal systems involved in these syndromes are cardiac, renal, and hematologic. Children with VACTERL association can also have vertebral, tracheoesophageal, and anal problems (
Table IV ).
The appropriate workup for radial deficiency associated with systemic conditions requires coordination with the child's pediatrician and referral to subspecialists. The heart is usually evaluated with auscultation and echocardiography. The kidneys are examined with ultrasound, and the platelet status is assessed with a blood-cell count and peripheral blood smear. The most devastating associated condition is Fanconi anemia. As children with Fanconi anemia do not have signs of bone-marrow failure at birth, the diagnosis is not apparent initially. The median age of onset of aplastic anemia is approximately seven years, and the majority of children experience symptoms between the ages of three and twelve years. However, a chromosomal challenge test that detects the disease prior to the onset of bone-marrow failure is available
17,18 . In this assay, a sample of the lymphocytes is subjected to diepoxybutane or mitomycin C, which causes chromosomes within Fanconi anemia cells to break and rearrange. In contrast, lymphocytes from unaffected children are stable when treated with these agents. Since bone-marrow transplantation is the only cure for Fanconi anemia, this prefatory diagnosis is crucial for the child and affected family. Early diagnosis provides ample time to search for a suitable bone-marrow donor or for the parents to consider pre-implantation genetic diagnosis
19,20 . Pre-implantation genetic diagnosis is a sophisticated technique that involves in vitro fertilization, sampling of the blastocyte to ensure HLA similarity without Fanconi disease, and reimplantation until birth. At delivery, cord blood is harvested from the newborn and is used as a source of stem-cell transplantation for the affected sibling. Since pre-implantation genetic diagnosis takes time, early detection with a chromosomal challenge test is critical and may ultimately save the affected child.
Children with VACTERL association warrant additional evaluation for spinal abnormalities, such as congenital scoliosis, and often require radiographs of the spinal column. It should be noted that children with VACTERL association often appear similar to children with Fanconi anemia. They often are of small stature, have feeding difficulties, and have similar musculoskeletal anomalies. Therefore, a chromosomal challenge test is warranted for a child with a presumed diagnosis of VACTERL association.
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Ulnar Deficiency
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Ulnar deficiency is four to ten times less common than radial deficiency
21,22 . This anomaly affects the postaxial border of the limb and can be confused with radial deficiency by a physician who is not familiar with upper-extremity congenital anomalies. Most importantly, unlike radial deficiencies, ulnar deficiencies are not associated with systemic conditions. Ulnar deficiencies are, however, associated with other musculoskeletal abnormalities that warrant a careful physical examination supplemented by radiographs (
Fig. 1 )
21,22 . An accurate diagnosis of ulnar deficiency obviates the need for the kind of extensive workup for systemic disorders that is indicated for patients with radial deficiency. At first consideration, one would expect a clear difference between radial and ulnar deficiencies. This distinction, however, is not always evident for multiple reasons. The remaining radius assumes characteristics similar to an ulna and can be fused with the distal part of the humerus (radiohumeral fusion). This prevents identification of the proximal part of the radius and results in a bone that resembles an ulna. As another confounding factor, the hand can have radial-sided anomalies ranging from a narrow web space to an absent thumb (
Table V )
23 . These radial-sided deficiencies do not transform an ulnar anomaly into a radial deficiency that warrants systemic evaluation. A careful clinical examination and scrutiny of the radiographs differentiates the two entities. Serial evaluations are occasionally necessary in equivocal cases.
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Fig. 1: A three-year-old child with ulnar deficiency of the right upper extremity. The elbow is fused, and the hand has two fingers and no thumb. An examination for other musculoskeletal abnormalities revealed congenital scoliosis secondary to a hemivertebra.
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Central Deficiencies
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Cleft hand results from a longitudinal deficiency of the central rays of the hand (index, long, and ring fingers). During development, the differentiation of these rays occurs at a different time than the differentiation of the radial and ulnar rays (thumb and small finger). There are two types of cleft hand, typical and atypical, and they possess separate features and require discrimination from each other (
Table VI ). In fact, there are major differences between typical and atypical cleft hand (a form of symbrachydactyly) that may warrant placement of the two types into different categories of embryologic malformation
24-26 . These findings suggest that typical cleft hand may result from fusion of, rather than absence of, digital rays. In contrast, atypical cleft hand is caused by necrosis of mesenchymal tissue and the body's attempt to regenerate deficient structures.
The typical cleft hand has a v-shaped defect with varying degrees of long-ray absence; most commonly the phalanges are missing, and the metacarpals are present
27,28 . This type of central deficiency is often bilateral and is usually inherited as an X-linked dominant trait with incomplete penetrance (
Fig. 2 ). There may be syndactyly of the ring-small or thumb-index web space, and associated foot involvement is common. Typical central deficiency is also associated with cleft lip and palate.
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Fig. 2: Three generations of typical central deficiency with different degrees of expression. Both of the grandmother's hands (bottom) and the mother's left hand (center) are missing only the long finger. The mother's right hand and both of the infant's hands are also missing the adjacent index and/or ring finger.
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Atypical cleft hand is a form of symbrachydactyly that involves the central three digits (index, long, and ring fingers)
26,27,29 . Symbrachydactyly is a spectrum of hand deficiencies ranging from short fingers (brachydactyly) that may be connected (syndactyly) to the absence of the central three fingers to complete absence of the digits, similar to a transverse deficiency. In atypical cleft hand, the index, long, and ring fingers are absent while the metacarpals are present. This deficiency creates a u-shaped cleft instead of the v-shaped configuration associated with typical cleft hand, as seen in
Figure 2 . An atypical cleft hand is not associated with systemic conditions and is not inherited. The deficiency is usually unilateral, sporadic, and not associated with foot involvement
30,31 . All forms of symbrachydactyly (including atypical cleft hand) can be associated with Poland syndrome, which is characterized by an ipsilateral chest wall deficiency (
Figs. 3-A and
3-B )
32 . Both symbrachydactyly and Poland syndrome are attributed to a deficient blood supply to the developing limb. A more proximal arterial insufficiency of, for example, the axillary or subclavian artery, results in Poland syndrome, whereas a distal deficiency affects the apical ectodermal ridge and results in symbrachydactyly. The relationship between symbrachydactyly and Poland syndrome requires careful examination of the chest wall. Absence of the sternocostal portion of the pectoralis major muscle is the most common chest-wall finding, although absence of additional muscles and breast underdevelopment can also be found
32 . Considerable chest or breast asymmetry may require referral to a plastic surgeon after adolescence. Interestingly, the amount of hand deficiency does not correlate with the degree of chest-wall abnormality. Therefore, even when a patient presents with mild symbrachydactyly, a complete evaluation of the integrity of the chest wall is required.
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Fig. 3-A: Figs. 3-A and 3-B A two-year-old child with Poland syndrome. Fig. 3-A The right upper extremity has an atypical cleft hand, a form of symbrachydactyly.
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Fig. 3-B: The chest wall shows absence of the sternocostal portion of the pectoralis major muscle and breast underdevelopment.
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Transverse Deficiencies
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Congenital transverse deficiency is defined according to the last remaining bone segment. A short below-the-elbow amputation is the most common transverse deficiency of the upper extremity
33 . The residual limb is usually well cushioned, and rudimentary nubbins or dimpling can be found on the end. These anomalies are usually unilateral, sporadic in occurrence, and rarely associated with other anomalies
v . The diagnosis should not be confused with amniotic disruption sequence (also known as constriction band syndrome), which is the result of entrapment of developing embryonic tissue by an amniotic band. This can manifest as amputation of a part and most commonly affects the digits (of the hands or feet). The diagnosis of amniotic disruption sequence requires the presence of a constriction band either affecting the involved extremity or elsewhere
34 .
A less common level of transverse deficiency is through the hand or metacarpals. This deficiency creates considerable unilateral impairment that can be lessened by prosthetic fitting and/or advanced surgical procedures, such as toe-to-hand transfers
35 . The long residual limb, however, dissuades the child from accepting a prosthesis and promotes the use of this limb as a sensate helper. The ultimate goal is restoration of prehension to allow independent usage. Advances in pediatric microsurgery have offered reasons to be optimistic concerning this lofty goal. Single and multiple toe-to-hand transfers are being applied to congenital and traumatic amputations at this level. The procedure requires considerable expertise and careful postoperative monitoring. Successful toe-to-hand transfers achieve some form of prehensile activity and augment function
35,36 .
Phocomelia represents a longitudinal failure of formation with an absent intervening segment of the extremity (intercalary aplasia). The missing segment can be the arm or forearm, or both, with the hand attached directly to the shoulder. This deformity is uncommon, with the exception of the markedly increased prevalence (60%) that occurred in association with thalidomide taken during the first trimester of pregnancy. Surgery is rarely indicated and prosthetic fitting is very beneficial, especially for patients with bilateral involvement. Prosthetic fitting can be difficult, however, because of the extreme shortening of the limb.
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Syndactyly
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Syndactyly is defined as an abnormal interconnection between adjacent digits and is described according to the magnitude and extent of the linkage
37 . The interconnection may encompass the entire length of the adjacent digits (complete) or it may discontinue proximal to the fingertip (incomplete). The syndactyly may involve only skin and fibrous tissue (simple) or include bone (complex). Syndactyly that occurs with other anomalies (e.g., Apert syndrome) is referred to as complicated syndactyly.
Syndactyly is a common congenital anomaly, with an incidence of approximately two or three per 10,000 live births, and it tends to occur in families
37,38 . Inheritable syndactylism is associated with genetic defects involving particular candidate regions on the second chromosome
39 . The mode of transmission is considered to be autosomal dominant with variable expressivity and incomplete penetrance
37,39 . This terminology signifies familial propagation, although the syndactyly may skip a generation and not be present in full form (variable phenotype). Familial syndactyly is associated with syndactyly of the second and third toes but not with systemic conditions
37 . Syndactyly can also occur sporadically, and this form is also not ordinarily associated with systemic conditions.
Complicated syndactyly is a broad category that encompasses many difficult forms of abnormal web-space connection and osseous abnormalities. Many of these cases are associated with a syndrome, most notably Poland syndrome (symbrachydactyly), constriction bands, or acrocephalosyndactyly (also known as Apert syndrome)
32,34,37,40-42 . As is the case with atypical cleft hand, syndactyly can occur with Poland syndrome. The mildest hand anomaly associated with Poland syndrome is a small hand with incomplete, simple syndactyly.
Amniotic disruption sequence results in digital amputation with or without pseudosyndactyly
34,37 . This type of syndactyly has discrete characteristics that differ from those of inheritable or sporadic cases. First, the fingers may be truncated secondary to band constriction and amputation. Second, a small cleft resides where the normal web space formed prior to entanglement with the amniotic band. Third, formation of a constriction band around the lower extremity and/or clubfoot deformity is common
34 .
Apert syndrome or acrocephalosyndactyly is rare and represents a constellation of congenital anomalies that necessitates a multidisciplinary approach to management
40-42 . These physically and mentally challenged children require care from various subspecialists, including neurosurgeons to monitor the cranial deformities, maxillofacial surgeons to manage the midfacial anomalies, otolaryngologists to address the potential airway obstruction, and hand surgeons to treat the upper-extremity anomalies. Depending on the position of the thumb and the overall appearance, the hands have been described as resembling a spade, spoon, mitten, rosebud, or hoof (
Fig. 4 )
40-42 . The most severe forms incorporate the thumb into the complex syndactyly, forming a broad conjoined nail (synonychia) and osseous fusion between the radial four digits. The congested palm is cup-shaped and laden with deep crevasses. Correction of syndactyly is a formidable task that requires multiple procedures to obtain digital independence. Early recognition of the Apert hand is necessary to guide referral and to achieve a multidisciplinary approach to the management of these impaired children.
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Fig. 4: A five-year-old child with typical facial features of Apert syndrome and bilateral hand syndactyly after separation of the index-long web space. Clinodactyly of both thumbs is typical of Apert syndrome.
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Polydactyly
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Polydactyly can occur on the preaxial (radial) and the postaxial (ulnar) side of the limb. Preaxial polydactyly is more common in whites, and postaxial polydactyly is more common in blacks. Postaxial polydactyly in a white individual is uncommon and is often indicative of an underlying syndrome (e.g., chondroectodermal dysplasia or Ellis-van Creveld syndrome) (
Fig. 5 )
43 .
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Fig. 5: A one-year-old white child with left postaxial polydactyly. Systemic workup for associated syndromes is warranted in this situation.
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Postaxial polydactyly is frequently inherited in an autosomal dominant pattern, but it has a variable penetrance pattern. The supernumerary digit is either well developed (type A) or rudimentary and pedunculated (type B)
43 . A small nubbin or scrawny postaxial element (type B) can be safely removed by tying the base with a suture in the nursery. The digit will turn gangrenous and fall from the hand. A residual bump or nubbin is the most common complication. A large or nearly normal digit (type A) requires operative ablation. The extra digit is removed, and any important functional parts (e.g., the ulnar collateral ligament and the abductor digiti quinti) are transferred to the adjacent finger.
Even though preaxial thumb duplication demonstrates a racial predilection toward whites, most cases are unilateral, sporadic, and not associated with systemic problems
44 . Further subclassification depends on the degree of skeletal replication
45 . The most common type of preaxial polydactyly (about 50% [fifty-three] of 100 cases
44,45 ) involves duplicated proximal and distal phalanges that share a common articulation with a bifid metacarpal head. Treatment often requires use of portions of each component, so-called "spare parts," to construct a properly aligned and functional thumb
46 .
Central polydactyly is an extra digit within the hand and not along its borders. The central polydactyly may be hidden within a concomitant syndactyly (i.e., synpolydactyly). Identification requires careful examination supplemented by radiographic verification. A particular form of central polydactyly (ring finger duplication) combined with syndactyly has a familial propagation and has been linked to a mutation of the HOXD13 gene on chromosome two
47 .
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Camptodactyly
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Camptodactyly is a painless flexion contracture of the proximal interphalangeal joint of the small finger that is usually gradually progressive
48-50 . There is no intra-articular or periarticular swelling. The metacarpophalangeal and distal interphalangeal joints are not affected, although compensatory deformities of these joints may develop. Camptodactyly is believed to occur in <1% of the population, although most cases are asymptomatic and many affected individuals do not seek medical attention
49 . Camptodactyly is bilateral in approximately two-thirds of patients, although the degree of contracture is usually not symmetrical. Other digits can be affected, although the prevalence decreases toward the radial side of the hand.
Camptodactyly has been divided into three categories
48,51 . A type-I deformity is the most common form and becomes apparent during infancy. The deformity is usually an isolated finding and is limited to the small finger. This congenital form affects males and females equally. A type-II deformity has similar clinical features, although it is not apparent until preadolescence. This acquired form of camptodactyly develops between the ages of seven and eleven years and affects females more often than it does males. It usually does not improve spontaneously, and it may progress to a severe flexion deformity
49,52 . During the growth spurt of adolescence, the flexion deformity of the proximal interphalangeal joint progresses and can reach 90°
50 .
A type-III deformity is often severe, usually involves multiple digits of both extremities, and is associated with a variety of syndromes (most commonly arthrogryposis). The extent of the involvement of the two hands is often asymmetric. This syndromic camptodactyly can occur in conjunction with craniofacial disorders, short stature, and chromosomal abnormalities (
Table VII and
Fig. 6 )
49,51 . Recognition of syndromic camptodactyly is usually straightforward, as numerous digits are involved and the condition is associated with facial distortion and limb contractures.
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Fig. 5: A sixteen-year-old boy with otopalatodigital syndrome and bilateral hand camptodactyly. Flexion deformities of all fingers are present; they are most severe in the ring and small digits.
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Many other disorders present with a flexion deformity of the fingers, and these diagnoses must be considered during the evaluation of a patient with suspected camptodactyly (
Table VIII )
53,54 . A thorough history and physical examination can exclude the majority of these etiologies. Finger contractures associated with syndactyly, central deficiencies, or brachydactyly are not regarded as camptodactyly.
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Clinodactyly
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Clinodactyly is more common than camptodactyly but is less problematic. The abnormal deviation is in the coronal or radioulnar plane
49 . Clinodactyly typically affects the middle phalanx of the small finger and produces an angulation of the distal interphalangeal joint. The deviation is usually in a radial direction. A deviation of <10° is so common, it may be considered normal
49,55 . On occasion, clinodactyly can involve several digits and is usually related to one or more delta-shaped middle phalanges. The deformity is usually fixed, and there is no intra-articular or periarticular swelling.
Clinodactyly can be inherited and is considered to be an autosomal dominant trait with variable expressivity and incomplete penetrance
56 . Familial clinodactyly is usually not associated with systemic conditions. However, clinodactyly is a physical finding of many genetic syndromes and chromosomal abnormalities, most notably Down syndrome, in which the prevalence is between 35% and 79%
49,57 . Thumb clinodactyly is a prominent feature of Apert syndrome, Rubinstein-Taybi syndrome, diastrophic dwarfism, and triphalangeal thumbs (
Fig. 4 )
40,58,59 .
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Macrodactyly
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Macrodactyly represents overgrowth of all structures of the involved digit and is different from an isolated enlargement of the bone (e.g., an enchondroma) or vessels (e.g., a hemangioma). This disfiguring condition can affect one digit or multiple fingers. The radial fingers are more commonly involved. Macrodactyly is usually an isolated abnormality, but it can occur with neurofibromatosis or Klippel-Trenaunay-Weber syndrome (limb hypertrophy, hemangiomas, and varicose veins) (
Fig. 7 )
60,61 .
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Fig. 7: A fourteen-year-old girl with Klippel-Trenaunay-Weber syndrome and bilateral macrodactyly. The right hand has enlargement of the index, long, and ring fingers. The left hand has macrodactyly of the index and long fingers.
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The etiology remains unknown, and both static and progressive forms have been observed. Static macrodactyly consists of an enlarged digit that is present at birth and grows proportionately over time. Progressive macrodactyly is more common and begins in childhood. The involved digit or digits increase in size throughout growth and stiffen during enlargement. Progressive growth persists until physeal closure occurs with skeletal maturity.
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Synostosis
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Synostosis is a generic term that indicates an osseous union between bones that are normally separate. Synostosis can occur as an independent entity or as part of a more general condition (e.g., complex syndactyly or ulnar deficiency). Synostosis most commonly involves the elbow and is usually not associated with systemic conditions. Radioulnar synostosis can be isolated or associated with a radial head dislocation. As is the case with camptodactyly and clinodactyly, radioulnar synostosis can be one of the physical findings a variety of syndromes, including trisomy (13 or 21) and fetal alcohol syndrome
62,63 . These syndromes present numerous problems that are more compelling than the absence of forearm rotation, and this is usually the reason for a delayed diagnosis of radioulnar synostosis. In addition, shoulder and wrist motion can compensate for the lack of forearm rotation during many childhood daily activities. Even in a healthy child, a delay in presentation is common until the child begins engaging in more complex daily activities, such as catching a ball or eating soup. A careful examination is necessary to identify a lack of forearm rotation, particularly in the presence of compensatory intercarpal rotation. Mild degrees of fixed pronation or supination are well tolerated and require no treatment
62 . Extremes of position create functional handicaps and may require a rotational osteotomy through the fusion mass to place the hand in a more functional position.
Synostosis can also occur in other parts of the upper extremity. A synostosis of the radiohumeral joint can occur as part of ulnar deficiency (
Fig. 1 ). In the hand, metacarpal transverse synostosis occurs most commonly between the ring and small fingers and is frequently bilateral (in 60% to 80% of patients)
64 .
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Thumb Hypoplasia
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There are various grades of thumb hypoplasia, which occurs most commonly as part of radial deficiency. The underdeveloped thumb has been classified into five types to guide treatment recommendations (
Table IX )
5-7 . A type-I deficiency represents the least involvement, with generalized thumb hypoplasia and without discrete absence of structures. A type-II deficiency is characterized by thumb-index web-space narrowing, absence of the thenar muscles, and instability of the metacarpophalangeal joint of the thumb. Type-III hypoplasia includes the intrinsic anomalies associated with a type-II deformity as well as additional skeletal and extrinsic musculotendinous abnormalities (e.g., involvement of the flexor pollicis longus). Type-III anomalies are divided into IIIA and IIIB subtypes, depending on the presence or absence of a stable carpometacarpal joint. Type-IV deficiency represents a severe expression of thumb hypoplasia and denotes a "pouce flottant" or residual digit
5,6 . Type V is complete absence of the thumb
2,5,6 .
The main distinction between a thumb that can be reconstructed and one that requires ablation is the presence of a carpometacarpal joint. A stable carpometacarpal joint provides a foundation for thumb reconstruction. An absent carpometacarpal joint excludes the possibility of thumb reconstruction and is best treated by ablation and pollicization. The clinical differentiation between types IIIA and IIIB can be difficult
7 . The child's behavior during the development of pinch and grasp often helps the physician to discriminate between a type-IIIA and type-IIIB deficiency. A stable, type-IIIA thumb is incorporated into routine use, whereas an unstable, type-IIIB thumb is ignored as prehension develops between the index and long digits. The index finger tends to reposition itself by pronation and rotation out of the palm. In equivocal cases, the decision may be further complicated by the delayed ossification of the trapezium and trapezoid, which normally ossify between four to six years of age.
Pollicization is the procedure of choice for types IIIB, IV, and V hypoplasia
2,5,6 . Attempts at microsurgical joint transfer to restore the carpometacarpal joint in types IIIB and IV have been reported. Currently, the results appear mediocre compared with those of index-finger pollicization and involve considerable microsurgical expertise
65 . The results of pollicization are directly related to the status of the transposed index digit and the surrounding musculature
2,6,66 . A mobile index finger transferred to the thumb position will provide stability for grasp and mobility for pinch. In contrast, a stiff index finger will provide a stable thumb for gross grasp but will not participate in pinch. For this reason, pollicization of the index finger provides good functional and cosmetic results in patients with isolated thumb hypoplasia but is less reliable in patients with radial forearm deficiencies. Early good results have been shown to persist into adulthood
66 .
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Overview
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Discoveries surrounding embryogenesis, limb formation, and the human genome are directly affecting our ability to detect and manage limb anomalies. Currently, only a small aggregate of limb anomalies has been mapped to specific chromosomal segments and even fewer have been mapped to the molecular level, but the number is rapidly increasing. Further identification of an abnormal gene or set of genes will expand the role of clinical geneticists and increase the availability and clinical applicability of genetic testing for limb malformations.
Detection of abnormalities is also being enhanced by high-resolution ultrasound examination of the developing fetus. The identification of fetal anomalies has resulted in the field of in utero surgery. This approach is being used for relief of renal obstructions, correction of diaphragmatic hernias, and closure of myelomeningoceles. As is true of many innovative procedures, the surgery is currently high risk, but advances in investigation and technique will decrease its morbidity. Separation of a syndactyly and release of a constricting amniotic band are just a couple of possible future applications of this technique.
Advances in detection and surgery will result in parallel social and ethical conflicts. These issues will require scrutiny and careful consideration with regard to use and misuse of these innovative techniques. Such steps are necessary to ensure appropriate application of modern strategies for the diagnosis and treatment of anomalous conditions.
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References
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- Flatt AE. Classification and incidence. In:
The care of congenital hand anomalies. 2nd ed. St. Louis, MO: Quality Medical Publishing; 1994. p 47-63.
- McCarroll HR. Congenital anomalies: a 25-year overview. J Hand Surg [Am], 2000;25: 1007-37. [Medline]
- Bamshad M, Watkins WS, Dixon ME, Le T, Roeder AD, Kramer BE, Carey JC, Jorde LB. Reconstructing the history of human limb development: lessons from birth defects. Pediatr Res, 1999;45: 291-9.
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Introduction
Classification of Limb Anomalies