Congenital anomalies of hand

Congenital anomalies of hand

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  CONGENITAL ANOMALIES OF HAND 14THJUNE 2019 DR OLAGUNJU OLUWAJUWON FEDERAL MEDICAL CENTER, BIRNIN KEBBI NIGERIA
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  EMBRYOLOGY OF HAND Development of the upper limb begins at around day 24 of gestation, when arm buds of the somatopleuric lateral plate mesoderm, capped by their overlying ectoderm, begin proliferating bilaterally in the lower cervical regions.
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   Over thefollowing 4 weeks, these buds enlarge and differentiate, and with the added migration of other cell types into the buds from deeper embryonic structures, form all the tissues of the limb.
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   As thelimb bud elongates, it must differentiate in three axes to provide the complex structures of the limb:  proximodistal,  craniocaudal and  dorsoventral.
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   The firstmanifestation of this patterning is the appearance of the apical ectodermal ridge (AER), a thickening of specialised ectoderm that runs craniocaudally along the rim of the limb bud tip.
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   The AERmaintains limb bud growth and influences the differentiation of the proliferating mesoderm, being laid down beneath it in a region called the progress zone (PZ)
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  PROXIMODISTAL  Factors secretedfrom the AER inflence gene expression in the PZ mesoderm, most importantly the genes encoding firoblast growth factors (FGFs). As the limb bud grows, it ‘lays down’ mesoderm and variations in PZ gene expression during this process result in the generation of different skeletal elements in each upper limb region.
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   Central tothis are the Hox genes in the PZ mesoderm, which undergo a transcription cascade with HOXD9 and HOXD10 expressed in the arm segment, HOXD11 the forearm, and HOXD12 and HOXD13 in the carpus, metacarpals and phalanges. The principal signalling factors from the AER for this include FGF4 and FGF2.
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  CRANIOCAUDAL  The mesodermdeep to the caudal edge of the AER is called the zone of polarising activity (ZPA) and is stimulated (again, primarily by AER FGFs) to create a polarising signal gradient of the morphogen protein sonic hedgehog (Shh).
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   At thecaudal edge of the limb bud, the Shh concentration is highest, which creates the structures of the ulnar side of the hand; progressively more radial structures are formed as the gradient decreases cranially.
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   Shh actsvia a variety of signalling pathways that include bone morphogenic proteins (BMPs) and it also stimulates sequential Hox gene activation.
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  DORSOVENTRAL  Patterning tocreate the dorsal and palmar (volar) structures of the hand appears to be governed by expression of Wnt-7a, which is restricted to the dorsal ectoderm of the limb bud.
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   Wnt-7a activitystimulates expression of the Lmx-1 transcription factor, while a different transcription factor, En-1, expressed in the ventral ectoderm, inhibits Wnt-7a expression.
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   Again, thisactivity is probably linked to Shh secretion and sequential Hox gene expression
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  TISSUE TYPES  Thesesignalling mechanisms direct  the lateral plate mesoderm of the limb bud to generate the bones, ligaments, tendons and vasculature of the limb.
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   However, themusculature and nerves are derived from cells migrating into the bud as it forms.  Somatic mesoderm migrates into the limb bud as separate dorsal and ventral condensations, giving rise to the extensor and flxor muscle groups, and with them the dorsal and ventral primary rami of spinal nerves C5–T1.
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   The Schwanncells of these nerves and melanocytes in the limb are derived from neural crest cells which migrate in to the bud in a similar way.
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  TIMETABLE OF UPPERLIMB DEVELOPMENT  Day 24 – limb bud growth initiated.  Day 33 – arm, forearm and hand plate can be distinguished. Blood circulation has begun.  Day 38 – hand has developed a carpal region and digital plate.  Day 44 – digital rays are visible as the intervening digital plate mesenchyme undergoes apoptosis.
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   Day 47– the limb has rotated medially to lie in a parasagittal (rather than coronal) plane, bringing the hand medially and the elbow dorsally. The cutaneous innervation patterns to the limb, i.e. its dermatomes, spiral as a consequence.
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   Day 56– all regions are well defied. Fingers have visible tactile pads (pulps) and overlap in the midline.
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  CLASSIFICATION OF CONGENITALHAND ABNORMALITIES
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   Although manyclassifiation systems of congenital upper limb abnormalities have been proposed, the International Federation of Societies for Surgery of the Hand has for a long time adopted is to use the system proposed by Swanson in 1976. This classifis seven groups on the basis of abnormal embryogenesis
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  Radial longitudinal deficiency Previously termed radial club hand, radial longitudinal defiiency (RLD) is a variable failure of formation of the longitudinal radial (pre-axial) structures, primarily the radius itself. It occurs in 1:30,000–1:100,000 live births, is more common in males than in females and most prevalent among Caucasian populations.
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   RLD isassociated with environmental and genetic factors, occurs in isolation or as part of a recognised syndrome, and is thought to be caused by a defiiency in ZPA morphogenic signalling. Associated environmental agents include thalidomide, phenobarbital and ethanol.
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   The largestsyndromic group is VACTERL (with a minimum of three out of the following: vertebral, anorectal, cardiac, tracheo-oesophageal, renal and limb abnormalities). However, Holt–Oram syndrome, Fanconi’s anaemia and thrombocytopenia-absent radius (‘TAR’) syndrome are also frequently associated.
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   Although thewhole limb may be involved, the most signifiant defiiencies are always at the hand and wrist. The right side is affected twice as often as the left, but the condition is bilateral in up to 50% of cases. The forearm is short with an absent or distally defiient radius, causing the (usually) short, curved ulna to bend the forearm radially
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   The scaphoidand trapezium are affected or absent, and variable thumb hypoplasia is frequently seen. The radial artery and superfiial radial nerve are often absent, with an abnormal median nerve compensating for this.
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   The conditionis classified into four groups (Bayne and Klug, 1987):  Type 1– short distal radius (second commonest)  Type 2 – hypoplastic radius (least common)  Type 3 – partial radial aplasia  Type 4 – complete radial aplasia (commonest)
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  ULNAR LONGITUDINAL DEFIIENCY Ulnar longitudinal defiiency (ULD) is a variable failure of formation of the longitudinal post-axial structures, primarily the ulna. It has an incidence of 1:100,000 live births and equal sex preponderance.  ULD is typically sporadic and is not associated with any syndrome, although 50% of cases are associated with other musculoskeletal abnormalities (e.g. fiular hemimelia).
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   Its aetiologyis linked to ZPA injury preventing adequate signalling to develop the ulnar structures.  There is a clinical spectrum of ulnar hypoplasia and, in contrast to RLD, the wrist is stable while the elbow is defiient, in the most severe cases with flxion contracture and pterygium.
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   Ulnar sideddigits are usually absent, but all digits may be affected and thumb hypoplasia may also be present.  Syndactylies are also common: both simple and complex.  The left side is more often affected than the right and the ratio of unilateral to bilateral is 4:1
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   Ulnar defiiencycan be classifid into four groups (Bayne, 1982):  Type 1 – hypoplastic ulnar  Type 2 – partial ulnar aplasia (proximal third present)  Type 3 – complete ulnar aplasia  Type 4 – humeroradial synostosis
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  CLEFT HAND (ECTRODACTYLY) Cleft hand is a variable failure of formation of the central ray, producing a characteristic cleft hand.  It has an incidence of 1:30,000–1:100,000 live births.  Unilateral clefting is usually sporadic, but the classical bilateral condition is autosomal dominant, affecting both hands and feet.
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   It isassociated with cleft lip and palate, syndactyly, polydactyly, ventricular septal defects, and ectrodactyly–ectodermal dysplasia clefting syndrome.  The cleft is caused by complete or partial absence of one or more of the central rays (phalanges and metacarpals), with frequent syndactyly of the thumb–index finger and the ring–little fingers.
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   Abnormal phalangesmay lie transversely in the cleft web, causing it to widen as they grow. With increasing severity, the radial structures of the hand become absent.  Children with cleft hand often have good function but suffer signifiant social stigma.  Their main functional issues relate to the state of their fist web space.
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   Hence, theclassifiation system relates to the quality of the fist web rather than to the cleft itself (Manske and Halikis, 1995).  Type 1 – normal fist web.  Type 2 – narrowed fist web.  Type 3 – syndactylised fist web.  Type 4 – merged fist web. Index digit is suppressed and the fist web is merged with the cleft.  Type 5 – absent fist web. Thumb absent and only the ulnar rays remain.
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  THUMB HYPOPLASIA  Althoughsometimes classifid as undergrowth, congenital thumb hypoplasia is closely related to RLD.  Blauth’s classifiation is the most widely recognised (Blauth, 1967), but has been recently modifid by Manske et al. (1995) (subdivision of type 3 thumbs) and Smith (2002) (subdivision of type 2 thumbs).
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   Type I– small thumb, all structures present  Type 2 – thenar hypoplasia, fist web adduction contracture. MCPJ ligamentous laxity  Type 2a – uniplanar laxity, particularly that of the ulnar collateral ligament  Type 2b – global joint laxity
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   Type 3– variable thenar, metacarpal and thumb extrinsic muscle hypoplasia and MCPJ laxity  Type 3a – stable carpometacarpal joint (CMCJ)  Type 3b – unstable CMCJ  Type 4 – metacarpal aplasia (pouce flottant)  Type 5 – complete thumb aplasia
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  SYNDACTYLY  Congenital syndactylyis a failure of digital separation during development.  It is one of the commonest congenital hand abnormalities, and has an incidence of 1:650–1:2000 live births.  Males are twice as likely to be affected as females.
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   The conditionmay be sporadic, inherited (20% of cases are autosomal dominant) or associated with various syndromes including Apert’s, Poland, Aarskog’s and many others.  Acrosyndactyly, in which there are distal digital fusions and proximal fenestrations, is seen as part of constriction ring syndrome.
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   Syndactylies areclassifid as:  Incomplete or complete (extending to digital tip)  Simple (soft tissue only) or complex (bony synostosis)  Single or multiple  Unilateral or bilateral  Hand, foot or both.
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  ARTHROGRYPOSIS  Arthrogryposis describesa collection of non-progressive joint contractures affecting at least two areas that are present at birth. It affects 1:3000 live births and is usually sporadic.  The principal aetiology is thought to be viral infection of the spinal cord anterior horn cells.
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  CAMPTODACTYLY  Camptodactyly isdefied as a congenital flxion deformity of the PIPJ. It affects 1% of the population and often goes unreported.  It tends to present either in infancy, when the sex distribution is equal, or at the start of adolescence, when females tend to be more affected than males.
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   Familial casesare inherited in an autosomal dominant fashion.  Camptodactyly is also associated with a number of syndromes, but the underlying aetiology remains unclear.
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   The littlefiger is most commonly affected, but the condition may affect multiple digits.  Bilateral presentation is more common than unilateral.  X-ray fidings in severe cases include joint space narrowing and flattening of the proximal phalanx head and middle phalanx base.
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  CLINODACTYLY  Clinodactyly isa congenital inclination of a digit in the radioulnar (craniocaudal) axis, usually at the level of the middle phalanx.  It is common and often familial (with autosomal dominant inheritance).  The little figer is most frequently affected (bent toward the ring figer), and most cases are bilateral.
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   The causeis often an abnormal bracketed epiphysis which leads to the formation of a deviating delta or trapezoidal phalanx.  The aetiology remains unclear.
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  POLYDACTYLY  Polydactyly isthe congenital formation of an extra digit (whole or part).  Alongside syndactyly, it is the commonest congenital hand abnormality.  The duplication may be pre-axial (radial), i.e. thumb duplication, central (affecting index, Middle or ring figers) or post-axial (ulnar).
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   The littlefiger is most commonly affected (ulnar polydactyly; inheritance is autosomal dominant) and most prevalent among Afro- Caribbean populations.
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   Ulnar polydactylyis classifid into three groups (Stelling, 1963):  Type 1 – soft tissue mass without bone and often a small pedicle  Type 2 – complete digit with all tissues  Type 3 – complete ray including metacarpal.
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  THUMB DUPLICATION  Pre-axial(thumb) polydactyly occurs in 8:100,000 live births.  It is usually unilateral and sporadic (with the exception of the triphalangeal thumb).  Both parts of the duplicated thumb are usually hypoplastic, but the radial duplicate tends to be most affected.
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   It isdescribed by the Wassel (1969) classifiation according to the level of duplication:  Type 1 – bifi distal phalanx  Type 2 – duplicated distal phalanx (second commonest)  Type 3 – bifi proximal phalanx  Type 4 – duplicated proximal phalanx (most common)  Type 5 – bifi metacarpal  Type 6 – duplicated metacarpal (third commonest)  Type 7 – triphalangeal thumb.
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  MACRODACTYLY  Macrodactyly (digitalgigantism) describes the congenital overgrowth of any digit. It is rare (2:100,000 live births), representing only 1% of all congenital hand abnormalities.  Primary and secondary causes are seen aetiologically.  Primary cases are usually sporadic, and thought to be due to abnormal innervation resulting in generalised enlargement of the digital lipofbromatous tissue.
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   This followsa varying distribution around the digital or median nerves, which also enlarge.  Secondary cases are associated with syndromes or other conditions, and result in overgrowth of other tissue types, e.g. vascular malformations in Klippel–Trenaunay syndrome, congenital lymphoedema, bone overgrowth in acromegaly, neurofiromatosis and multitissue hyperplasia in Proteus syndrome.
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   Most presentationsare unilateral and 70% involve more than one digit (index and middle, most commonly).  The distal part of the digit is usually the worst affected.  The enlargement may interfere with function, may be aesthetically debilitating and, in some cases, nerve compression can result, necessitating release.
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  SYMBRACHYDACTYLY  This isa variable failure of formation of the digits, with a tendency to preserve the thumb.  It has an incidence of 1:10,000–1:30,000 live births and, although usually sporadic, may be associated with Poland syndrome.  It is thought to be due to a mesenchymal defect that leaves ectodermal remnants as skin and nail nubbins.
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   Also calledamniotic band syndrome.  Constriction ring syndrome occurs when tight bands encircle the foetus in utero, impairing vascular and lymphatic function to create characteristic deformities distal to the ring.  This occurs in 1:15,000 live births.
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   The causeis still poorly understood and two aetiologies have been proposed:  the intrinsic model suggests a germ cell layer defect that creates vascular disruption to the embryo,  while the extrinsic model suggests that disruption to the amnion releases bands of this tissue which encircle and strangulate the growing foetus.
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   It isassociated with oligohydramnios in the mother, and affected children can also suffer cleft lip and palate, talipes equinovarus and other congenital defects.  No hereditary basis has been identified.
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   The constrictionscan affect any part of the body, but are commonest in the limbs and may be complete or incomplete.  Distal limb parts are worst affected, and defects are usually multiple on more than one limb.
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   Four subtypeshave been described (Patterson, 1961):  Type 1 – simple circular groove with normal distal structures  Type 2 – deeper groove with distal deformity ± lymphoedema  Type 3 – rings and associated distal acrosyndactyly  Type 3a – digits fused at tips  Type 3b – tips fused, and associated with web creep  Type 3c – complete syndactyly  Type 4 – intra-uterine amputation.
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