Chapter 72: Congenital Hand Anomalies

In contrast to adults, where clinical assessment can be directed by specific commands and copied movements, the examination of young children can be far more challenging. It is often most effective to observe the child in a calm environment with toys and see how they utilize their hand/s and assess what function is possible and what deficiencies are evident. Congenital hand anomalies are relatively common, with an incidence of up to 1:626 live births1 and many children with such deformities generally function very well as they adapt to the limbs with which they are born. When meeting with parents for the first time in clinic, it is important to provide sufficient information without overloading them. Parents often go through a grieving process over the loss of the “perfect baby” that was expected,2 and many families will not have known about the congenital difference until the baby was born. Therefore, the first visit with a family and their new born will involve careful counseling. Further information can be provided in subsequent consultations and supported with appropriate written and web-based resources. The timing of surgery is multifactorial and there is no hard and fast rule around age. In general, it is preferable to delay elective surgery in children until they reach 1 year of age from an anesthetic perspective. Surgery may be technically easier if the hand is bigger and on this basis leaving surgery until later may be preferable. Early surgery is sometimes indicated for reasons such as differential growth in border digits in syndactyly, and in general surgery preschool is helpful for psychosocial reasons. Compliance fluctuates with age and temperament and children tend to be quite robust and fair well after surgery at most ages. When surgery has been performed it is vital to protect the limb from interference in the early phases of healing. For this reason, a meticulous, nonconstrictive dressing that is unlikely to spontaneously be removed is imperative. An above-elbow full cast with the elbow flexed at 90 degrees is frequently necessary in order to protect skin grafts or osteotomies. Prolonged postoperative immobilization is tolerated much better by children than adults, and persistent stiffness is rare.1,2

2. Waters PM, Bae DS, eds. Pediatric Hand and Upper Limb Surgery: A Practical Guide. Philadelphia: Lippincott Williams & Wilkins; 2012 Embryologic development of the limb occurs primarily between weeks 5 and 8. Growth and development occur in three main directions: proximal to distal (axial), radial to ulnar (preaxial and postaxial), and volar to dorsal. The zone of polarizing activity (ZPA) is a cluster of mesenchymal cells on the postaxial (ulnar) border and plays a role in preaxial/postaxial (radial to ulnar) differentiation. It induces ulnar formation and the four ulnar sided digits in the hand. Consequently, interference with the ZPA results in abnormal ulnar side development such as ulnar longitudinal deficiency. Volar/dorsal development is controlled by the dorsal ectoderm and the wingless- type protein (WNT7) and Lim homeodomain transcription factor (LMX1B). Altered development in this field can result in absence of the fingernails. The apical ectodermal ridge (AER) is an ectodermal thickening at the leading edge of the limb bud, responsible for axial development. Its removal leads to limb truncation. Progressive loss of fibroblast growth factor (FGF) function at the AER leads to a loss of radial structures (e.g., thumb hypoplasia).1–4

Swanson1 described the uniformly accepted classification system for congenital hand anomalies in 1976. This has been adopted by most hand authorities, including the International Federation of Societies for Surgery of the Hand and the American Society for Surgery of the Hand. It has seven categories and is a popular topic for examination questions (Table 72.1). Syndactyly is the congenital fusion of two or more digits and is an example of failure to differentiate. The precise cause is unknown, but the theory is that there may be a failure of digital patterning, failure of apoptosis between the digits, or failure of the apical ectodermal ridge (AER) regression.2 Examples of failure to form would be phocomelia or radial/ulnar longitudinal deformities. Examples of duplication include polydactyly and mirror hand. An example of overgrowth would be macrodactyly, while an example of undergrowth would be brachydactyly. There are two further categories to this classification: constriction band and generalized anomalies and syndromes. Constriction band syndrome (congenital band syndrome or Streeter’s syndrome) represents a range of abnormalities where limbs or digits have linear indentations or, when severe, become circumferentially constricted leading to deformity or loss of the distal part. It is also associated with acrosyndactyly and may be confused with symbrachydactyly. It is thought to occur secondary to abnormal amniotic band material settling on the developing embryo in utero. Some conditions such as trigger thumb are not considered to be true congenital deformities and so do not fit within the classification scheme. Table 72.1 Classification for Congenital Hand Anomalies1 Type Examples I Failure of formation Phocomelia, hypoplastic thumb, radial, central, or ulnar longitudinal deficiency II Failure of differentiation Synostosis, syndactyly, radial head dislocation, symphalangism, camptodactyly, clinodactyly, Kirner’s deformity III Duplication Polydactyly, mirror hand, duplicate thumb IV Overgrowth Macrodactyly V Undergrowth Brachydactyly VI Constriction band Constriction band VII Generalized

4. Oberg KC, Feenstra JM, Manske PR, Tonkin MA. Developmental biology and classification of congenital anomalies of the hand and upper extremity. J Hand Surg Am 2010;35(12):2066–2076

The most common site for syndactyly is the third web space, with the first web space being seen least often. In the United States, the incidence of syndactyly is 1:2,000 live births. This condition is 10 times more common in white people than in black people and up to 40% of cases have a family history of syndactyly. Syndactyly is much less common than camptodactyly, the incidence of which is probably closer to 1:100. It is difficult to define the optimal time for surgery, but it is commonly performed between 1 and 2 years of age provided it does not affect the border digits. If border digits are involved, correction is usually carried out earlier so that differential growth of the digits is not affected.1–3

Wassel1 classified thumb duplication according to the underlying bony anatomy (Fig. 72.2). Type I: Least common, occurs in 2%2 Type IV: Most common, occurs in 43%2 Type VII: Most complex, requires at least one triphalangeal thumb. Syndactyly is classified into incomplete/complete, simple/complex/complicated, according to both soft-tissue and skeletal features. Classification systems for other abnormalities have also been described and these are largely based on clinical appearance. Blauth3 classified hypoplastic thumb anomalies, and Manske and McCaroll4 modified them as follows: Type 1: Diminution of thenar muscle bulk, smaller thumb elements Type 2: Absence of thenar intrinsic muscles, decreased thumb–index web space, metacarpophalangeal (MCP) joint instability from the ulnar collateral ligament Fig. 72.1 A, Typical type I or spade-shaped hand. B, Type II or mitten hand. C, Type III or rosebud hand. A B C Type 3A: Type 2 with extrinsic muscle abnormalities, even less bony (metacarpal) element, stable carpometacarpal (CMC) joint Type 3B: Type 3A with an unstable CMC joint Type 4: Floating thumb (pouce flottant): Small pedicle holding a floating thumb Type 5: Completely absent thumb A key point is that the presence or absence of a stable CMC joint will guide surgical management. Patterson5 classified constriction ring syndrome as follows: Type I: Simple constriction ring Type II: Constriction ring with deformity of the distal part Type III: Constriction with variable fusion of distal parts (acrosyndactyly) Type IV: Complete intrauterine disruption Upton6 classified macrodactyly as follows: Type I: Macrodactyly with lipofibromatosis of the nerve(s) Type II: Associated with neurofibromatosis (von Recklinghausen’s disease) Type III: Macrodactyly with hyperostosis (very rare) Type IV: Macrodactyly with hemihypertrophy

Camptodactyly is a common condition typically affecting the little finger. It can be present and first noticed at birth or it can worsen with accelerated growth and only become evident around the time of puberty. Females are more commonly affected than males and presentation is common at this age. The underlying cause is not I II III IV V VI VII Fig 72.2 Wassel classification of thumb polydactyly. confirmed, but theories include abnormal flexor digitorum superficialis (FDS), tendons (such as additional FDS slips), abnormal extensor tendons, bony deformities of the proximal interphalangeal (PIP) joint, or abnormal lumbrical muscle insertions. Mild contractures should be managed with physiotherapy and extension splinting. More severe contractures may occasionally require surgical release; however, surgery has a high failure rate. Plain radiographs should be obtained to exclude bony abnormalities. The lateral view is particularly important to assess the joint shape and articular surfaces.1–3

Clinodactyly refers to a curvature of the finger in a radial/ulnar direction and often features an abnormal middle phalanx. The physis may be C-shaped (bracketed) around one corner of the phalangeal base (Fig. 72.3). The middle phalanx may be triangular or trapezoidal in shape and the former is termed a “delta” phalanx. These features prevent normal growth on one side resulting in uneven growth of the digit. The presence of a deformed head of the proximal phalanx is more typical of camptodactyly. Clinodactyly is usually painless and affects the little finger most frequently. Surgical correction nearly always requires a stabilizing K-wire. A Z-plasty may be required to release the soft tissues. Splinting is not an effective treatment for clinodactyly.1–4

Polydactyly is a condition where there are more than five digits on one hand. In well-developed ulnar-side polydactyly, there is a 30% risk of syndromic association; therefore, a full workup should be arranged in such cases. In contrast, mild ulnar polydactyly is rarely associated with other conditions and normally represents an isolated finding. Although conditions such as Holt-Oram syndrome and Fanconi anemia are more common with radial longitudinal deficiency, an association also exists between them and radial polydactyly (specifically, triphalangeal thumb or Wassel type VII). Therefore, it is prudent to ensure that the children with radial polydactyly are also fully assessed by a pediatrician.1,2 Polydactyly is classified as preaxial or postaxial, depending on whether the radial or ulnar digits are duplicated. Postaxial subtypes are classified as A or B, depending on how well the extra digit is formed (A is well formed and B is rudimentary). Preaxial subtypes are classified using the Wassel system.3 Both classifications are useful to guide management. Incidence is estimated to be between 1:300 and 1:3,000 depending on subtype and race. These may be underestimates because of autoamputation of rudimentary digits at an early age. Complex surgery is not required for the majority of polydactyly cases. Treatment requirements depend on the subtype and extent of the abnormality. For example, mild ulnar polydactyly may autoamputate or be managed with simple ligation, whereas complex radial polydactyly may require complex reconstruction of the thumb with ligamentous, bony, and muscle insertion alteration. Fig. 72.3 Clinodactyly caused by a longitudinally bracketed physis.

correct? Macrodactyly is a condition of overgrowth of a digit and is usually an isolated unilateral finding but may be associated with other conditions such as neurofibromatosis. For this reason, a full assessment of the other features associated with neurofibromatosis should be explored. The etiology of macrodactyly is largely unknown, but the most common theory is that the growth is somehow nerve induced. There are different types of macrodactyly (static or progressive) and growth may therefore be proportional or disproportionate to other digits. Both soft tissue and bone are usually affected, and amputation may be the best option for some patients, although debulking is generally performed as a first-line treatment. The psychological effects of this condition can be severe, so a multidisciplinary approach including counseling is advised.1–3

Radial longitudinal deficiency is a congenital condition affecting the radial structures of the arm and may include either a hypoplastic or absent radius and thumb anomalies. It is essential to evaluate such patients for other associated conditions. Holt-Oram syndrome is an autosomal dominant condition where patients have a radial longitudinal deformity and a number of cardiac defects including septal defects, tetralogy of Fallot, mitral valve prolapse, and a patent ductus arteriosus. VACTERL syndrome involves vertebral, anal, cardiac, tracheoesophageal fistula, renal and lower extremity abnormalities, as well as the radial longitudinal deficiency. Blood dyscrasias associated with radial longitudinal deficiency include TAR syndrome (thrombocytopenia and absent radius) and Fanconi anemia which is an autosomal dominant condition with bone marrow failure. Pollex abductus is a situation where the long thumb flexor tendon inserts onto the extensor mechanism, thereby causing abduction on forced thumb flexion. It may be present in radial longitudinal deficiency or polydactyly. All patients with radial longitudinal deficiency should receive a cardiac workup (auscultation, echocardiography), a renal ultrasound, complete blood count (CBC) with differential and medical genetics referral. However, in most cases, these have already been done by the referring team prior to review in the plastic surgery clinic.1–4

deformity? Thumb hypoplasia is a type of radial longitudinal deficiency with a spectrum of severity that is classified using the modified Blauth system. This classification is useful clinically, as it directs likely treatment. Type I is a mild deformity where the thenar intrinsic muscles are hypoplastic and the thumb is generally reduced in size. This rarely requires surgical intervention. Type 2 involves thenar intrinsic hypoplasia with a narrowed first web space, metacarpophalangeal (MCP) joint instability from ulnar collateral ligament (UCL) laxity. Type 3A is similar to type 2 but also involves extrinsic muscle abnormalities, hypoplastic bony elements, and a stable carpometacarpal (CMC) joint. Both 2 and 3a subtypes are treated with web space deepening such as Z-plasties or a jumping man flap. Opponensplasty with ring finger FDS, extensor indicis proprius (EIP), or Huber transfer may be required. UCL stabilization may also be needed. Type 3B has the same features as type 3A, but the defining difference is the lack of a stable CMC joint. Type 4 is a floating thumb and type 5 is a complete aplasia. Therefore, types 3B and above are typically treated with pollicization. Routine use of the thumb by the child helps the clinician to distinguish a type 3A from a type 3B deformity, as the child will tend to ignore the thumb, instead preferring a scissor grip with the index and long fingers.1–4

Typical cleft hand is normally bilateral and familial. Syndactyly is a common finding. Hand function is usually very good, but cosmesis is poor. For this reason, Flatt described it as a “functional triumph, but a social disaster.” Metacarpal abnormalities are common, as these bones can be absent, bifid, or duplicated. This condition may be associated with cleft lip or cleft palate; so, the oral cavity should be assessed during examination. Atypical cleft hand differs from typical cleft hand and can occur as part of Poland’s syndrome. Therefore, it can be associated with any of the other common features of Poland’s syndrome such as chest wall deformity, upper limb abnormality, or breast hypoplasia. Atypical cleft hand is unilateral and spontaneous with syndactyly occurring infrequently. The remaining digits can be markedly hypoplastic.1,2

incorrect? Vascular compromise in the toe warrants prompt surgical release. However, it is advisable to release no more than 50% of the circumference at one time to reduce the risk of exacerbating vascular compromise. If the toe were simply lymphedematous, observation and elevation would be sufficient at this early stage. As a child grows, constriction bands can interfere with deeper structures, and plain radiographs can be helpful to monitor the underlying ankle joint. Hair tourniquets around the toes of infants are commonly referred to plastic surgery for review. The hair is usually very difficult to visualize even with loupe magnification and management may require blade division of the hair down to or through the skin to ensure adequate release.1–3

Trigger thumb in a child is treated differently from that in adults. Half of all cases of pediatric trigger thumb will settle without surgery within 6 months with conservative measures including stretching. Steroid injections and splinting usually provide no benefit. It is bilateral in only a quarter (not half) of cases, and imaging is rarely indicated unless trauma has occurred. Notta’s node is a thickening on the FPL tendon that catches on the A1 pulley. This pulley is surgically released only in persistent cases. The diagnosis should be explained to the parents and follow-up planned for approximately 6 to 8 weeks.1,2