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Syndactyly
SYNDACTYLY BY SCOTT H. KOZIN, MD
Syndactyly is a common congenital anomaly that interferes with normal hand function. Inheritable, spontaneous, and syndromic forms have been identified with various similarities and dissimilarities. Inheritable syndactylism is associated with genetic defects involving particular candidate regions on the second chromosome. Syndactyly separation follows established principles with regard to timing, technique, and postoperative management. Early release of border digits is mandatory to promote function and prevent contracture. Proper flap design provides commissure reconstruction and avoids the use of skin graft within the web space. Identification of neurovascular anomalies and preservation of critical vascular inflow preserves digital perfusion. Postoperative dressings provide compression to skin-grafted areas and protection to the underlying digits. Adherence to recognized principles yields acceptable results, although complications can emerge requiring additional management. Copyright © 2001 by the American Society for Surgery of the Hand he normal hand contains a thumb and 4 digits, all separated by web spaces with supple skin to allow interdigital movement. The normal interdigital abduction is at least 35° between the fingers and 70° between the thumb and index.1 The integrity of the commissure and the extent of web connection influences independent digital movement. The normal web space allows digital abduction/adduction and individual flexion/extension, which are required for optimum hand function. The natural commissure gently slopes from dorsal to palmar (45° to 50°) and extends approximately two thirds the length of the proximal phalanx.2 The shape of the
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From Shriners Hospitals for Children, Philadelphia, PA, and the Department of Orthopaedic Surgery, Temple University, Philadelphia, PA. Address reprint requests to Scott H. Kozin, MD, Shriners Hospitals for Children, 3551 North Broad Street, Philadelphia, PA 19140. E-mail: [email protected] Copyright © 2001 by the American Society for Surgery of the Hand 1531-0914/01/0101-0001$35.00/0 doi:10.1053/jssh.2001.21778
commissure also varies across the hand to accommodate varying function. The index-long and ring-small commissures are more rectangular in shape, which increases the breadth of the hand during broad grasp.2 The long-ring space appears more V in configuration, which assists in stabilization of the central rays. In syndactyly, the extent and intensity of digital union is variable, which guides the classification scheme.1,2 The extent of syndactyly is either incomplete if the skin bridge does not extend the full length of the involved digits or complete if the connection encompasses the entire length (Fig 1). Complete syndactyly can also produce a shared or common fingernail (synonychia) (Fig 2). The intensity of syndactyly is either soft tissue alone (simple) or in conjunction with bone (complex). Complex syndactyly implies fusion of adjacent phalanges or interposition of accessory bones (Figs 3 and 4). There are also atypical forms of syndactyly that are labeled complicated and present with either convoluted soft tissue abnormalities or a hodgepodge of abnormal bones. Many of these atypical configurations occur in accordance with a variety of
JOURNAL OF THE AMERICAN SOCIETY FOR SURGERY OF THE HAND 䡠 VOL. 1, NO. 1, FEBRUARY 2001
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FIGURE 1. Adult man with incomplete ring-small syndactyly that has not interfered with function.
syndromes and defy standard terminology and classification. The term complicated can be incorporated into subtypes of simple and complex syndactyly. This would create a classification scheme that guides treatment (Table 1). This article discusses syndactyly with reference to inheritance, clinical picture, surgery, postoperative management, outcome, and complications. An understanding of the etiology and pathoanatomy coupled with surgical experience is the passport to effective treatment.
FIGURE 3. Six-month-old child with complex syndactyly of ulnar 2 digits.
occurs in families.1,3 The mode of transmission is considered autosomal dominant with variable expressivity and incomplete penetrance. 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. Syndactyly is more prevalent in male offspring, which may indicate a decreased penetrance in females. Syndactyly can also occur sporadically without a familial history.
SIMPLE SYNDACTYLY Genetics Simple syndactyly occurs with an incidence of approximately 2 to 3 per 10,000 live births and often
FIGURE 2. Three-month-old child with bilateral complete long-ring-small syndactyly and common nail plate.
FIGURE 4. Radiograph indicates fusion of the adjacent middle and distal phalanges.
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TABLE 1 Syndactyly Classification Simple syndactyly (SS) Standard (SSs) Complicated (SSc)
Urgent (SSu) Complex syndactyly (CS) Standard (CSs) Complicated (CSc)
Unachievable (CSu)
Straightforward simple syndactyly of nonborder digit. Surgery can be delayed until 18 months of age. Simple syndactyly associated with additional soft tissue interconnections, syndromes (eg, Poland’s syndrome, central deficiency), or abnormal bony elements (eg, hypoplasia). Treatment must be individualized, and beware of neurovascular anomalies. Soft tissue syndactyly of border digits or digits of unequal length, girth, or joint level. Requires early separation to prevent angular and rotational deformity of tethered digit. Complex syndactyly of adjacent phalanges without additional bony anomalies (eg, delta phalanx, symphalangism). Complex syndactyly associated with additional bony interconnections (eg, transverse phalanges, symphalangism, polysyndactyly), or syndromes (eg, constriction band syndrome). Treatment must be individualized and digits may function better as a unit. Complex syndactyly with severe anomalies of the underlying bony structures that often prohibits formation of a 5-digit hand without extensive surgical intervention.
Abbreviations: c, complex; s, straightforward; u, urgent.
The sequencing of the human genome and investigation into the molecular basis of limb development has provided particulars about chromosomal markers for syndactyly.3,4 The classic autosomal dominant syndactyly has been localized to a specific candidate region of a responsible gene (2q34-q36).3 Syndactyly combined with ring finger duplication (synpolydactyly) has been linked to a gene mutation (HOXD13 gene) that is also located on chromosome 2 (2q31).4 This information provides further insight into the genetic basis of syndactyly and offers potential diagnostic and treatment options. Etiology Embryogenesis of the upper extremity commences at 4 weeks and is complete 8 weeks after fertilization.5 Most upper extremity congenital anomalies occur during this period of rapid limb development. By 5 weeks gestation, the hand segment appears in the form of a paddle covered by the apical ectodermal ridge (AER). The AER regulates proximal to distal limb axis configuration and secretes proteins that influence the development of the underlying tissues. During embryogenesis, the AER fragments around the hand paddle, which results in longitudinal interdigital necrosis between the digits. Failure of the AER to separate is the most prevalent explanation for syndactyly and represents a failure of differentiation. In both simple and complex syndactyly, the middle-ring web space is most frequently involved, fol-
lowed by the ring-little interspace.1,2 The thumbindex web space develops earlier than the fingers and is the least common pairing. Thumb-index syndactyly may accompany other anomalies (eg, central deficiency, Apert’s acrocephalosyndactyly). Surgical Decision Making Mild incomplete syndactyly that does not interfere with function does not require treatment (Fig 1). In contrast, simple syndactyly of any considerable degree warrants surgical reconstruction of the web space for improved function and appearance. The timing of release and technique of separation are both controversial but abide by certain guidelines.1,2 Of primary importance, border digits (thumb-index and ringsmall web spaces) have marked differences in their respective lengths and should be separated within the first few months of life. Early intervention allows the thumb to participate in prehensile function and prevents tethering of the longer digit, which results in a flexion contracture and rotational deformity (Fig 5). In contrast, long-ring syndactyly combines digits of relatively equal lengths, which negates the development of a flexion contracture. Therefore, separation can be delayed until the child is older and the hand larger, which facilitates surgical reconstruction. This delay is valuable, because surgery performed after 18 months of age has a lower incidence of complications and unsatisfactory results (eg, web creep).6 The second principle of syndactyly also involves the timing of
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FIGURE 5. Four-month-old child with complete syndactyly of bilateral ring-small web spaces and subsequent development of ring finger flexion contracture and pronation deformity.
digital separation. Surgical reconstruction should only include one side of an affected digit at a time to avoid vascular compromise of the skin flaps or digit. The skin flaps are more in jeopardy than the digits, because ischemia is unlikely unless marked arterial anomalies are present and inadvertent vessel injury occurs.1 Therefore, complete separation of 3 connected adjacent fingers requires staged surgical procedures. The third dictum deals with surgical separation of complete syndactyly and the need for supplemental skin graft. This dogma specifies that after release of a complete syndactyly, there will be a skin deficiency that requires additional skin grafting. Because the circumference of 2 digits separated is 22% greater than those digits conjoined and because flap designs cannot mobilize additional skin, graft is always required.1,2 The last tenet also involves surgical reconstruction, specifically the formation of an appropriate commissure. This edict emphasizes the need for supple skin within the commissure so that use of skin graft can be avoided. This requires creation of a flap to recreate the commissure, which avoids interdigital contracture and motion-limiting scar. Surgical Technique Syndactyly release is performed under general anesthesia by using a pediatric tourniquet and loupe magnification. A skin graft donor site is selected to provide a source for supplemental skin. The groin is preferred to allow full-thickness harvest with minimal
morbidity. The graft is drawn in an elliptical fashion to allow primary wound closure, and it is outlined lateral to the femoral artery to decrease the chance of hair growth during puberty. Other skin graft donor options include the antecubital fossa, wrist crease, hypothenar area, and lower abdomen. A multitude of flap designs have been proposed for syndactyly release, and surgeons appear to have their own preferences.1,2,7 However, there are general guidelines that should be followed during flap configuration. First, a local flap must be designed to ensure commissure reconstruction. This flap can be based dorsal and/or palmar, although the dorsal skin has certain inherent advantages. This dorsal skin is thinner and easier to mobilize than the glabrous palmar skin. The dorsal flap also recreates the normal dorsal-to-palmar commissure slope (Fig 6). The flap begins at the level of the metacarpal heads and encompasses two thirds of the length of the proximal phalanx. On the palmar surface of the dorsal commissure flap, a rectangular flap is fashioned to resurface the proximal area of a digit adjacent to the commissure. The proximal transverse incision represents the level of commissure reconstruction, and the distal transverse edge equals the length of the dorsal commissure flap. Subsequently, interdigitating zigzag dorsal and palmar flaps are constructed distal to the dorsal commissure and palmar rectangular flap (Fig 7). The dorsal zigzag incision begins at one distal corner of the commissure flap, whereas the palmar starts at the opposite corner of the rectangular flap. The dorsal
FIGURE 6. Syndactyly release begins with elevation of dorsal flap for commissure reconstruction.
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FIGURE 7. Interdigitating zigzag dorsal and palmar flaps to resurface the separated digits.
incision extends to the midline of the proximal interphalangeal joint of the adjacent finger and back across to the midline of the distal interphalangeal joint. At this level, the incision extends distal between the tips of the interconnected digits. The palmar flaps are based opposite the dorsal flaps (mirror images), with the base centered over the opposite proximal and distal interphalangeal joints to allow for interdigitation. This orientation minimizes the tendency for formation of a flexion scar contracture and maximizes coverage potential. The volar rectangular flap (opposite the dorsal commissure flap) and zigzag construct can be biased to cover one digit entirely, leaving residual bare areas on the adjacent digit that requires skin grafting. The flaps are elevated by sharp dissection with meticulous hemostasis of the underlying tissue. The dorsal flaps are usually elevated first, preserving the paratenon surrounding the extensor tendon. Next, the volar flaps are raised, and the underlying neurovascular bundles are isolated. The digits are separated from distal to proximal with protection of the neurovascular bundles. Manual spreading of the digits places the intervening tissue under tension, which facilitates digital separation. The stout transverse fascial bands are incised along with the natatory ligament to allow for adequate proximal placement of the commissure.
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The transverse intermetacarpal ligament is not divided for fear of instability. The bifurcation between the common and proper neurovascular structures is identified during proximal dissection. A distal split of the digital nerves can easily be separated by microdissection. A distal arterial junction requires surgical decision making, because ligation of a proper digital artery for an acceptable commissure placement may be required. Selection of the proper digital artery to ligate depends on the status of the proper digital artery on the adjacent sides of the digits being separated. If both digits have intact proper digital arteries on both sides, the smaller-caliper artery is usually ligated. However, if one of the digits still requires additional surgery (eg, staged syndactyly release), it is appropriate to consider ligation of the larger artery. If the status of the opposite digital artery is unclear, vascular clamps can be applied to the digital arteries and the tourniquet deflated to ensure adequate perfusion of each digit.1 Failure of either digit to perfuse is rare and requires preservation of both digit arteries. Options include distal insetting of the commissure without vessel ligation or microsurgical reconstruction of the proper digital arteries. Fortunately, vascular anomalies are unusual in simple syndactyly, but they can be encountered in complex or complicated cases. Before insetting of the flaps, the adjacent sides of the separated digits are defatted.2 This step decreases the tension across the flaps and improves the overall
FIGURE 8. Dorsal flap sutured for commissure reconstruction and zigzag flap prepared for insetting.
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dactyly separation. Webbing that extends past the proximal interphalangeal joint is managed with similar flap design and skin grafting. A smaller amount of webbing can be treated with local flap coverage without supplemental skin grafting. Placement of 2 opposing Z-plasties (aka butterfly flap) is a favored technique that provides a wide dorsal flap for commissure reconstruction (Fig 11).2 However, this technique requires supple skin and is not applicable when there is scar contracture about the web space, such as during revision surgery. In these instances, standard syndactyly technique combined with additional skin graft is preferred.
COMPLEX SYNDACTYLY FIGURE 9. Closure after release of complete syndactyly and addition of supplemental skin graft.
appearance of the separated digits. The commissure flap is sutured first to assess placement and configuration of the web space (Figure 8). Subsequently, the interdigitating flaps are approximated, and excessive tension is avoided. An absorbable 5-0 or 6-0 suture is used for closure. The remaining skin defects are covered with a full-thickness skin graft (Fig 9). Proper postoperative dressings are an essential part of the operation (Fig 10). The dressings must apply compression across the skin graft sites and protect the separated digits. Nonadhering dressing and moist cotton are placed into the web spaces and reinforced by large amounts of soft gauze. In young children, the compressive hand dressing must be reinforced by above-the-elbow plaster immobilization to prevent inadvertent removal. A sugar-tong splint wrapped around the elbow and over the hand protects the digits and allows the elbow to be positioned in greater than 90° of flexion. The dressings are removed 2 weeks after surgery, and gentle washing and wound care are initiated. The wounds are kept covered for an additional week until the scabs desiccate and detach. Normal hand use is encouraged, and formal therapy is usually not required. Scar massage, silicone gel sheets, or elastomere products can treat areas of hypertrophic scarring. Simple Incomplete Syndactyly Web-space deepening of partial webbing of the fingers follows the same principles as complete syn-
omplex syndactyly adjoins the soft tissue and bone along a portion or the entire length of the adjacent digits. This form of syndactyly is less common than simple syndactyly and more challenging to treat, especially as the quantity of bony union increases. Union between the distal phalanges creates a combined fingertip with a coalescence of the nail bed. Proximal flap design follows identical principles as simple syndactyly release. After elevation of the proximal flaps, incision along the groove in the nail divides the terminal synostosis and synonychia. Separation of the fingertips creates exposed bone and absence of a nail fold that require particular treatment. The fingertip can be treated by excision of a central nail and matrix wedge, which allows closure and formation of a lateral nail fold (Fig 12). This reduction maneuver
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FIGURE 10. Sugar-tong splint wrapped above the elbow immobilization and over the hand to protect the digits and minimize chance of inadvertent dressing removal.
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FIGURE 11. Diagram of 2 opposing Z-plasties (aka butterfly flap) to provide commissure reconstruction in incomplete syndactyly.
provides adequate closure but tends to narrow the fingertip. A variety of coronal or palmar flaps have been offered as alternatives to provide nail fold recreation and skin coverage without sacrificing width.8 These long flaps recreate the nail margin but require careful handling to prevent necrosis. Composite grafts harvested from the toes have also been used to provide pulp tissue and better nail margins.9 These grafts should be slightly oversized (25% to 33%) to compensate for the linear contraction of the dermis and attrition of the adipocytes. Another option involves using a preliminary pedicle flap (thenar or abdominal)
to augment pulp tissue before formal syndactyly reconstruction.1 Determining the correct plane of cleavage, realigning the joints, and managing the soft tissue are the difficult issues in complex syndactyly. Identifying the proximal and distal extents of the bony connection and probing for an interconnecting ridge or axilla can guide division. Actual separation of the bone into individual components can be accomplished by using a knife blade. The soft tissue coverage is more difficult, and neurovascular anomalies are more frequent, which complicates surgical reconstruction. Strict guidelines for surgical reconstruction are impossible to provide, and treatment must be individualized.
COMPLICATED SYNDACTYLY omplicated syndactyly is a broad category that encompasses many difficult forms of abnormal web space connection and bony abnormalities. Many of these cases are associated with a syndrome, most notably Poland’s (symbrachydactyly), constriction bands, or acrocephalosyndactyly. The treatment algorithm is more involved and often requires experience in congenital hand surgery. A meticulous physical examination and parental discussion are essential components during formulation of a treatment strategy. In many instances, the definitive surgical plan cannot be developed during a single examination, and repeat
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FIGURE 12. Reduction of fingertip via excision of a central nail and matrix wedge for formation of a lateral nail fold with subsequent narrowing of the fingertip.
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FIGURE 13. Four-year-old girl with complicated syndactyly of ring-small fingers (dorsal view).
assessment of the child is necessary. A variety of props and gentle persuasion are required to evaluate overall hand and individual digit use. There are instances of complicated syndactyly that represent contraindications to surgical intervention (Figs 13-16). In these instances, the connected digits function better as a unit than as separate entities. This is especially applicable in children with a normal thumb and a conglomeration of fingers with bizarre bone and joint anomalies. This decision requires a careful explanation to the parents with reference to the importance of a normal thumb and opposable digit(s) for hand function. The decision not to intervene is often more difficult to explain to the parents than the decision to perform surgery. However, the creation of multiple individual digits with insufficient motion for hand function must be avoided. The surgical treatment of complicated syndactyly uses many of the established principles for simple syndactyly, although modification is necessary to circumvent many of the peculiar findings. In addition, intricate skin and soft tissue procedures have been
FIGURE 14. Palmar view indicates relatively equal lengths and skin (joint) creases.
FIGURE 15. Radiograph shows intact distal and middle phalanges but absent metacarpal and proximal phalanges.
developed for various types of complicated syndactyly. The following section will discuss particular forms of complicated syndactyly associated with a variety of generalized skeletal anomalies or syndromes. Symbrachydactyly and Chest Wall Anomaly (Poland syndrome) Poland syndrome is an ipsilateral anomaly of the hand and chest wall.10 The clinical findings are variable, ranging from mild to severe. The mild form is classically described as a small hand with incomplete simple syndactyly and an absence of the sternocostal
FIGURE 16. Full flexion and ability to make a fist coupled with absence of proximal support negates attempts at digital separation.
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FIGURE 17. Seven-month-old child with constriction band syndrome affecting both hands. Right hand shows rings of varying severity. Left hand shows acrosyndactyly and proximal sinus cleft.
portion of the pectoralis major muscle. The brachydactyly component characteristically involves the middle phalanx. More severe forms involve progressive bony reduction beginning in the central digits and resembling a central deficiency. Successive thumb and small finger involvement can occur, culminating in a complete transverse deficiency of all digits. The proximal muscle deficiencies and breast underdevelopment can also progress to a hollow chest wall deformity with complete absence of the breast. Simple incomplete syndactyly associated with Poland’s syndrome is separated in a manner similar to conventional syndactyly. Distal bifurcation of the neurovascular bundles is fairly common and must be treated accordingly. The digital hypoplasia, associated neurovascular anomalies, and underlying syndrome appropriately classify this syndactyly as complicated. The extent of involvement between the digits dictates the necessity of supplemental skin graft. The commissure should be placed further proximal to create digits that appear longer. Despite proximal commissure placement, the affected digits and limb will always be undersized, and realistic expectations must be conveyed to the parents. Syndactyly and Constriction Band Syndrome Syndactyly associated with constriction bands is not hereditary and is often referred to as pseudosyndactyly or acrosyndactyly (distal connection of digits)(Fig 17). The cause remains controversial with intrinsic and extrinsic theories.11 The intrinsic theory states that the amniotic bands represent a localized lack of mesodermal development, similar to a normal skin crease. The depth of the mesodermal defect deter-
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mines the severity of clinical presentation. The extrinsic theory reasons that either the amniotic membrane traps the developing hand or an amniotic band encircles the affected part, leading to a variable amount of injury. Mild digital damage initiates an embryonic repair process and yields variable amounts of circumferential stricture. This inflammatory response can merge adjacent digits distal to the rudimentary web. Complete vascular ischemia results in truncation of the digits and syndactyly of the affected parts at the site of amputation. Currently, the extrinsic hypothesis is favored, because amnion has been found in the constriction ring, and the bands tend occur in a straight line across multiple digits. Irrespective of the magnitude of constriction, a web space or sinus cleft remains present between the volar and dorsal aspects of the digits (Fig 18). Surgical reconstruction follows the principles established for syndactyly release, although modifications are necessary to accommodate the peculiar anatomy. Unfortunately, any available web space is often placed too distal, and formal commissure reconstruction is required. The cleft or sinus tract often represents an obstacle to flap design and is usually excised and discarded. The skin proximal to the residual web space can be incorporated into the commissure flap design.
FIGURE 18. One-year-old child with distal syndactyly and truncation of long and ring finger. A small proximal cleft is present, which is characteristic of constriction band syndrome.
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FIGURE 19. Three-year-old child with central deficiency and marked narrowing of the thumb-index web space.
FIGURE 20. Elevation of rabbit-ear flap from cleft for transposition into thumb-index web space.
The distal parts of the digits may be conglomerated or ballooned into a single mass, which creates considerable surgical difficulty. Determination of the digital orientation, growth potential, and function is often difficult. Future surgical procedures and the ultimate functional goal of the involved hand are important components to consider. In certain cases, digital separation is not possible. In other instances, digits of unequal length can be treated with a 2-staged reconstruction. The initial procedure divides the distal connection between the digits to prevent progressive angular deformity. Formal commissure reconstruction is delayed until an accurate analysis of digit individuality can be performed.
dorsal rotation flap for adequate deepening. Severe thumb-index narrowing can be treated at the time of cleft closure by using an ingenious flap harvested from the cleft and transposed into the thumb-index commissure (Figs 20 and 21).13 Apert Syndrome Apert syndrome, or acrocephalosyndactyly, is rare and represents a constellation of congenital anomalies that necessitates a multidisciplinary approach to management.14-16 These physically and mentally challenged children require care from various subspecialists. Neurosurgeons must monitor the cranial deformities, maxillofacial surgeons manage the mid-
Syndactyly and Central Deficiency Central deficiency and syndactyly can occur jointly in the same hand.12 The syndactyly affects the ringsmall and/or thumb-index web space. The ring-small web space syndactyly is usually purely soft tissue (simple) and is treated by conventional release and skin grafting. The extent of thumb-index syndactyly is variable and requires individualized treatment (Fig 19). Progressive syndactyly is associated with malrotation of the thumb into the plane of the other digits, intrinsic muscle anomalies (primarily opposition), and extrinsic tendon dysfunction.12 Mild thumb-index syndactyly can be managed by web deepening and local flap coverage. A 4-flap Z-plasty deepens the web and provides a more rounded contour than a 2-flap configuration. Moderate involvement requires a local
FIGURE 21. Cleft closure and flap insetting to narrow the central deficiency and resurface the thumb-index commissure.
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FIGURE 22. Five-year-old child with type I syndactyly (spade hand) with coronal syndactyly of central digits and simple incomplete syndactyly of ring-small web space.
fascial anomalies, otolaryngologists address the potential airway obstruction, and hand surgeons treat the upper-extremity anomalies. The hand anomalies are consistent and include a shortened thumb with radial deviation, complex syndactyly of the index, long, and ring digits with symphalangism, and simple syndactyly of the ringsmall web space.15,16 There are 3 types of hands defined according to the thumb position and overall appearance.15 Type I (“spade hand”) is the least involved and is characterized by a coronal syndactyly of the central digits (distal ends), creating a flat palm (Figs 22 and 23). The radially deviated thumb is not incorporated into the central syndactyly, although the web space is shallow. Type II (“spoon hand” or “mitten hand”) is more involved, because the thumb is drawn into the index digit, creating an incomplete or complete syndactyly. The thumb retains a separate nail matrix and the palm is concave. Type III (“rosebud hand” or “hoof hand”) is the most severe form and incorporates the thumb into the complex syndactyly forming a broad conjoined nail (synonychia) and bony fusion between the radial four digits. The small finger remains segregated from the bony union, but simple complete syndactyly is present. The congested palm is cup-shaped and laden with deep crevasses. The presence of metacarpophalangeal joints provides markers for commissure reconstruction. Considerable neurovascular anomalies are present, especially
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within the central conglomeration of digits.15 Distal bifurcation of the common digital arteries and median nerves is frequent, which complicates separation of the complex central syndactyly. Extrinsic flexor and extensor tendon abnormalities are also widespread, and peculiar intrinsic muscle anatomy is prevalent. Syndactyly correction in these cases is a formidable task that requires multiple procedures to obtain digital independence.14,16 Similar to simple syndactyly, priority is given to separation of border syndactyly for prehensile function and to allow unimpeded growth without additional deformity. The thumb-index and ring-small web spaces can be created at the same time. The technique for first web reconstruction varies with the extent of web space insufficiency. Mild deformity can be corrected with a 4-flap Z-plasty, moderate involvement may require a local dorsal rotation flap, and severe syndactyly necessitates more complex alternatives (eg, radial forearm flap). A distal branching pattern of the princeps pollicis artery to the index digit is frequently encountered during reconstruction of the first web space and must be managed appropriately.16 An effort to preserve this branch will facilitate later separation of the index, long, and ring syndactyly. The ring-small web space is recreated using standard techniques for syndactyly separation. The index finger is released about 6 months after separation of the border digits (Fig 24). A standard dorsal commissure flap and interdigitating zigzag incisions are used with skin grafting to the residual uncovered areas. Neurovascular anomalies are common, and the bundles must be identified and treated accordingly. An attempt is made to preserve any blood
FIGURE 23. Bilateral hand radiographs show distal union of central digits with associated symphalangism.
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FIGURE 24. Syndactyly separation and commissure reconstruction of index-long web space with supplemental skin graft.
supply to the central conglomerate in preparation for later division. After segregation of the thumb, index, and small digits, the long-ring syndactyly is assessed for possible release. Complex interconnections and marked skin deficiency must be considered when planning separation. Options include leaving the digits conjoined, amputating the long digit at the metacarpophalangeal joint (ie, creation of a 3-fingered hand), and performing syndactyly release with pedicle groin flap coverage.1,14,16 The specific reconstruction varies with the patient (intellect, compliance, motivation), mobility of the digits, and surgeon preference. Complications Certain complications are predictable and should be discussed with the parent before surgery. One third of patients with isolated syndactyly and two thirds of those with complex or complicated syndactyly will require additional surgery.1 Therefore, follow-up should continue until adulthood. The parents should also be informed that surgery for complex or complicated syndactyly cannot transform anomalous digits into normal counterparts. Underlying deficiencies in the bones, joints, and tendons prohibit such extraordinary results. Acute. Skin graft failure can occur as a result of hematoma, seroma, or loss of the postoperative bandages. Skin graft loss is more common in infants,
because graft tension is more difficult to obtain and dressings are more prone to inadvertent removal. A very small amount of graft loss is inconsequential and will heal by secondary intention. However, any substantial loss requires repeat grafting to prevent hypertrophic cicatrix formation, which leads to an unacceptable result. Flap loss is less common and is associated with improper design or excessive tension. A zigzag configuration with tip angles of less than 45° increases the incidence of necrosis and should be avoided.1 Appropriate width of the flaps (ie, midline to midline) ensures adequate digital coverage and lessens tension during insetting. Judicious defatting of the subcutaneous tissue also decreases flap tension and eases insetting. Circumferential tension created by flap tightness can also jeopardize digital perfusion. Digital circulation must be assessed before dressing application, which should be compressive but not constrictive. Digital loss is exceptionally rare after syndactyly release. Inadvertent vessel injury requires detection and appropriate management dependent on the status of the other proper digital artery. Prompt intervention may be necessary to restore vascular inflow and avoid digital loss. Chronic. Web creep is the distal migration of the reconstructed commissure with growth (Fig 25). The reported incidence is extremely variable (7.5% to
FIGURE 25. Twelve-year-old child with distal migration of the web space (web creep) requiring revision.
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60%) and partly related to the inaccuracies in normal web space determination.17 A variety of methods have been used including clinical evaluation, photographs, line drawings and radiographs.1,17 In addition, there is more to a commissure than measurement alone, and many aesthetic components are not readily quantifiable. Radiograph determination appears to be the most accurate and has been defined according to bone age and degree of ossification.17 However, radiation exposure, cost, and inability to apply the measurement technique in patients with bony abnormalities hinder its clinical applicability. The development of web creep is multifactorial and related to age at surgery, surgical technique, and any acute postoperative problems. Patients younger than 18 months at the time of surgery tend to have more web creep and less-successful outcomes.6 Flawed flap design can lead to inadequate commissure reconstruction, which promotes distal migration of the web. Skin graft characteristics also influence the amount of web creep. Split-thickness grafting is associated with an 8-fold increase in web migration compared with full-thickness.1 Skin graft loss is another cause of web creep secondary to scar formation. Irrespective of proper flap design and meticulous full-thickness grafting, web creep can still occur over time.
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FIGURE 26. Adolescent with persistent nail plate abnormalities after release of complete syndactyly.
Residual Nail Deformity Despite valiant attempts at nail fold and pulp reconstruction, residual nail deformity is common after separation for complete syndactyly with associated synonychia (Fig 26). Irregular nail appearance and flawed nail formation are often present. Reconstruction options are available, although most patients accept the residual deformity.
ACKNOWLEDGMENT The author would like to thank James H. Dobyns, MD, for his continued support and dialogue.
REFERENCES 1. Eaton CJ, Lister GD. Syndactyly. Hand Clin 1990;6:555574. 2. Flatt AE. The care of congenital hand anomalies. 2nd ed. St. Louis, MO: Quality Medical Publishing, 1994:228-275. 3. Bosse K, Betz RC, Lee YA, et al. Localization of a gene for syndactyly type 1 to chromosome 2q34-q36. Am J Hum Genet 2000;67:492-497. 4. Muragaki Y, Mundlos S, Upton J, Olsen BR. Altered growth and branching patterns in synpolydactyly caused by mutations in HOXD13. Science 1996;272:548-551. 5. Riddle RD, Tabin CJ. How limbs develop. Sci Am 1999;280: 74-79. 6. Keret D, Ger E. Evaluation of a uniform operative technique to treat syndactyly. J Hand Surg [Am] 1987;12A:727-729. 7. Bauer TB, Tondra JM, Trusler HM. Technical modification in repair of syndactylism. Plast Reconstr Surg 1956;17:385-392. 8. Golash A, Watson JS. Nail fold creation in complete syndactyly using Buck-Gramcko pulp flaps. J Hand Surg [Br] 2000;25B:11-14. 9. Sommerkamp TG, Ezaki M, Carter PR, Hentz VR. The pulp-plasty: a composite graft for complete syndactyly fingertip separations. J Hand Surg [Am] 1992;17A:15-20.
10. Ireland DCR, Takoyama N, Flatt A. Poland’s syndrome: a review of 43 cases. J Bone Joint Surg Am 1976;58A:52-58. 11. Wiedrich TA. Congenital constriction band syndrome. Hand Clin 1998;14:29-38. 12. Richterman I, Dupree J, Kozin SH, Thoder J. Radiographic analysis of web height. J Hand Surg [Am] 1998;23A:10711076. 13. Cole RJ, Manske PR. Classification of ulnar deficiency according to the thumb and first web. J Hand Surg [Am] 1997;22A:479-488. 14. Snow JW, Littler JW. Surgical treatment of cleft hand. Transactions of the International Society of Plastic and Reconstructive Surgery, 4th Congress. Rome: Excerpta Medica Foundation, 1967:888-893. 15. Hoover GH, Flatt AE, Weiss MW. The hand and Apert’s syndrome. J Bone Joint Surg Am 1970;52A:878-895. 16. Upton J. Classification and pathologic anatomy of limb anomalies. Clin Plast Surg 1991;18:321-355. 17. Zuker RM, Cleland HJ, Haswell T. Syndactyly correction of the hand in Apert syndrome. Clin Plast Surg 1991;18:357-364.
Syndactyly is a common congenital anomaly that interferes with normal hand function. Inheritable, spontaneous, and syndromic forms have been identified with various similarities and dissimilarities. Inheritable syndactylism is associated with genetic defects involving particular candidate regions on the second chromosome. Syndactyly separation follows established principles with regard to timing, technique, and postoperative management. Early release of border digits is mandatory to promote function and prevent contracture. Proper flap design provides commissure reconstruction and avoids the use of skin graft within the web space. Identification of neurovascular anomalies and preservation of critical vascular inflow preserves digital perfusion. Postoperative dressings provide compression to skin-grafted areas and protection to the underlying digits. Adherence to recognized principles yields acceptable results, although complications can emerge requiring additional management. Copyright © 2001 by the American Society for Surgery of the Hand he normal hand contains a thumb and 4 digits, all separated by web spaces with supple skin to allow interdigital movement. The normal interdigital abduction is at least 35° between the fingers and 70° between the thumb and index.1 The integrity of the commissure and the extent of web connection influences independent digital movement. The normal web space allows digital abduction/adduction and individual flexion/extension, which are required for optimum hand function. The natural commissure gently slopes from dorsal to palmar (45° to 50°) and extends approximately two thirds the length of the proximal phalanx.2 The shape of the
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From Shriners Hospitals for Children, Philadelphia, PA, and the Department of Orthopaedic Surgery, Temple University, Philadelphia, PA. Address reprint requests to Scott H. Kozin, MD, Shriners Hospitals for Children, 3551 North Broad Street, Philadelphia, PA 19140. E-mail: [email protected] Copyright © 2001 by the American Society for Surgery of the Hand 1531-0914/01/0101-0001$35.00/0 doi:10.1053/jssh.2001.21778
commissure also varies across the hand to accommodate varying function. The index-long and ring-small commissures are more rectangular in shape, which increases the breadth of the hand during broad grasp.2 The long-ring space appears more V in configuration, which assists in stabilization of the central rays. In syndactyly, the extent and intensity of digital union is variable, which guides the classification scheme.1,2 The extent of syndactyly is either incomplete if the skin bridge does not extend the full length of the involved digits or complete if the connection encompasses the entire length (Fig 1). Complete syndactyly can also produce a shared or common fingernail (synonychia) (Fig 2). The intensity of syndactyly is either soft tissue alone (simple) or in conjunction with bone (complex). Complex syndactyly implies fusion of adjacent phalanges or interposition of accessory bones (Figs 3 and 4). There are also atypical forms of syndactyly that are labeled complicated and present with either convoluted soft tissue abnormalities or a hodgepodge of abnormal bones. Many of these atypical configurations occur in accordance with a variety of
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FIGURE 1. Adult man with incomplete ring-small syndactyly that has not interfered with function.
syndromes and defy standard terminology and classification. The term complicated can be incorporated into subtypes of simple and complex syndactyly. This would create a classification scheme that guides treatment (Table 1). This article discusses syndactyly with reference to inheritance, clinical picture, surgery, postoperative management, outcome, and complications. An understanding of the etiology and pathoanatomy coupled with surgical experience is the passport to effective treatment.
FIGURE 3. Six-month-old child with complex syndactyly of ulnar 2 digits.
occurs in families.1,3 The mode of transmission is considered autosomal dominant with variable expressivity and incomplete penetrance. 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. Syndactyly is more prevalent in male offspring, which may indicate a decreased penetrance in females. Syndactyly can also occur sporadically without a familial history.
SIMPLE SYNDACTYLY Genetics Simple syndactyly occurs with an incidence of approximately 2 to 3 per 10,000 live births and often
FIGURE 2. Three-month-old child with bilateral complete long-ring-small syndactyly and common nail plate.
FIGURE 4. Radiograph indicates fusion of the adjacent middle and distal phalanges.
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TABLE 1 Syndactyly Classification Simple syndactyly (SS) Standard (SSs) Complicated (SSc)
Urgent (SSu) Complex syndactyly (CS) Standard (CSs) Complicated (CSc)
Unachievable (CSu)
Straightforward simple syndactyly of nonborder digit. Surgery can be delayed until 18 months of age. Simple syndactyly associated with additional soft tissue interconnections, syndromes (eg, Poland’s syndrome, central deficiency), or abnormal bony elements (eg, hypoplasia). Treatment must be individualized, and beware of neurovascular anomalies. Soft tissue syndactyly of border digits or digits of unequal length, girth, or joint level. Requires early separation to prevent angular and rotational deformity of tethered digit. Complex syndactyly of adjacent phalanges without additional bony anomalies (eg, delta phalanx, symphalangism). Complex syndactyly associated with additional bony interconnections (eg, transverse phalanges, symphalangism, polysyndactyly), or syndromes (eg, constriction band syndrome). Treatment must be individualized and digits may function better as a unit. Complex syndactyly with severe anomalies of the underlying bony structures that often prohibits formation of a 5-digit hand without extensive surgical intervention.
Abbreviations: c, complex; s, straightforward; u, urgent.
The sequencing of the human genome and investigation into the molecular basis of limb development has provided particulars about chromosomal markers for syndactyly.3,4 The classic autosomal dominant syndactyly has been localized to a specific candidate region of a responsible gene (2q34-q36).3 Syndactyly combined with ring finger duplication (synpolydactyly) has been linked to a gene mutation (HOXD13 gene) that is also located on chromosome 2 (2q31).4 This information provides further insight into the genetic basis of syndactyly and offers potential diagnostic and treatment options. Etiology Embryogenesis of the upper extremity commences at 4 weeks and is complete 8 weeks after fertilization.5 Most upper extremity congenital anomalies occur during this period of rapid limb development. By 5 weeks gestation, the hand segment appears in the form of a paddle covered by the apical ectodermal ridge (AER). The AER regulates proximal to distal limb axis configuration and secretes proteins that influence the development of the underlying tissues. During embryogenesis, the AER fragments around the hand paddle, which results in longitudinal interdigital necrosis between the digits. Failure of the AER to separate is the most prevalent explanation for syndactyly and represents a failure of differentiation. In both simple and complex syndactyly, the middle-ring web space is most frequently involved, fol-
lowed by the ring-little interspace.1,2 The thumbindex web space develops earlier than the fingers and is the least common pairing. Thumb-index syndactyly may accompany other anomalies (eg, central deficiency, Apert’s acrocephalosyndactyly). Surgical Decision Making Mild incomplete syndactyly that does not interfere with function does not require treatment (Fig 1). In contrast, simple syndactyly of any considerable degree warrants surgical reconstruction of the web space for improved function and appearance. The timing of release and technique of separation are both controversial but abide by certain guidelines.1,2 Of primary importance, border digits (thumb-index and ringsmall web spaces) have marked differences in their respective lengths and should be separated within the first few months of life. Early intervention allows the thumb to participate in prehensile function and prevents tethering of the longer digit, which results in a flexion contracture and rotational deformity (Fig 5). In contrast, long-ring syndactyly combines digits of relatively equal lengths, which negates the development of a flexion contracture. Therefore, separation can be delayed until the child is older and the hand larger, which facilitates surgical reconstruction. This delay is valuable, because surgery performed after 18 months of age has a lower incidence of complications and unsatisfactory results (eg, web creep).6 The second principle of syndactyly also involves the timing of
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FIGURE 5. Four-month-old child with complete syndactyly of bilateral ring-small web spaces and subsequent development of ring finger flexion contracture and pronation deformity.
digital separation. Surgical reconstruction should only include one side of an affected digit at a time to avoid vascular compromise of the skin flaps or digit. The skin flaps are more in jeopardy than the digits, because ischemia is unlikely unless marked arterial anomalies are present and inadvertent vessel injury occurs.1 Therefore, complete separation of 3 connected adjacent fingers requires staged surgical procedures. The third dictum deals with surgical separation of complete syndactyly and the need for supplemental skin graft. This dogma specifies that after release of a complete syndactyly, there will be a skin deficiency that requires additional skin grafting. Because the circumference of 2 digits separated is 22% greater than those digits conjoined and because flap designs cannot mobilize additional skin, graft is always required.1,2 The last tenet also involves surgical reconstruction, specifically the formation of an appropriate commissure. This edict emphasizes the need for supple skin within the commissure so that use of skin graft can be avoided. This requires creation of a flap to recreate the commissure, which avoids interdigital contracture and motion-limiting scar. Surgical Technique Syndactyly release is performed under general anesthesia by using a pediatric tourniquet and loupe magnification. A skin graft donor site is selected to provide a source for supplemental skin. The groin is preferred to allow full-thickness harvest with minimal
morbidity. The graft is drawn in an elliptical fashion to allow primary wound closure, and it is outlined lateral to the femoral artery to decrease the chance of hair growth during puberty. Other skin graft donor options include the antecubital fossa, wrist crease, hypothenar area, and lower abdomen. A multitude of flap designs have been proposed for syndactyly release, and surgeons appear to have their own preferences.1,2,7 However, there are general guidelines that should be followed during flap configuration. First, a local flap must be designed to ensure commissure reconstruction. This flap can be based dorsal and/or palmar, although the dorsal skin has certain inherent advantages. This dorsal skin is thinner and easier to mobilize than the glabrous palmar skin. The dorsal flap also recreates the normal dorsal-to-palmar commissure slope (Fig 6). The flap begins at the level of the metacarpal heads and encompasses two thirds of the length of the proximal phalanx. On the palmar surface of the dorsal commissure flap, a rectangular flap is fashioned to resurface the proximal area of a digit adjacent to the commissure. The proximal transverse incision represents the level of commissure reconstruction, and the distal transverse edge equals the length of the dorsal commissure flap. Subsequently, interdigitating zigzag dorsal and palmar flaps are constructed distal to the dorsal commissure and palmar rectangular flap (Fig 7). The dorsal zigzag incision begins at one distal corner of the commissure flap, whereas the palmar starts at the opposite corner of the rectangular flap. The dorsal
FIGURE 6. Syndactyly release begins with elevation of dorsal flap for commissure reconstruction.
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FIGURE 7. Interdigitating zigzag dorsal and palmar flaps to resurface the separated digits.
incision extends to the midline of the proximal interphalangeal joint of the adjacent finger and back across to the midline of the distal interphalangeal joint. At this level, the incision extends distal between the tips of the interconnected digits. The palmar flaps are based opposite the dorsal flaps (mirror images), with the base centered over the opposite proximal and distal interphalangeal joints to allow for interdigitation. This orientation minimizes the tendency for formation of a flexion scar contracture and maximizes coverage potential. The volar rectangular flap (opposite the dorsal commissure flap) and zigzag construct can be biased to cover one digit entirely, leaving residual bare areas on the adjacent digit that requires skin grafting. The flaps are elevated by sharp dissection with meticulous hemostasis of the underlying tissue. The dorsal flaps are usually elevated first, preserving the paratenon surrounding the extensor tendon. Next, the volar flaps are raised, and the underlying neurovascular bundles are isolated. The digits are separated from distal to proximal with protection of the neurovascular bundles. Manual spreading of the digits places the intervening tissue under tension, which facilitates digital separation. The stout transverse fascial bands are incised along with the natatory ligament to allow for adequate proximal placement of the commissure.
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The transverse intermetacarpal ligament is not divided for fear of instability. The bifurcation between the common and proper neurovascular structures is identified during proximal dissection. A distal split of the digital nerves can easily be separated by microdissection. A distal arterial junction requires surgical decision making, because ligation of a proper digital artery for an acceptable commissure placement may be required. Selection of the proper digital artery to ligate depends on the status of the proper digital artery on the adjacent sides of the digits being separated. If both digits have intact proper digital arteries on both sides, the smaller-caliper artery is usually ligated. However, if one of the digits still requires additional surgery (eg, staged syndactyly release), it is appropriate to consider ligation of the larger artery. If the status of the opposite digital artery is unclear, vascular clamps can be applied to the digital arteries and the tourniquet deflated to ensure adequate perfusion of each digit.1 Failure of either digit to perfuse is rare and requires preservation of both digit arteries. Options include distal insetting of the commissure without vessel ligation or microsurgical reconstruction of the proper digital arteries. Fortunately, vascular anomalies are unusual in simple syndactyly, but they can be encountered in complex or complicated cases. Before insetting of the flaps, the adjacent sides of the separated digits are defatted.2 This step decreases the tension across the flaps and improves the overall
FIGURE 8. Dorsal flap sutured for commissure reconstruction and zigzag flap prepared for insetting.
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dactyly separation. Webbing that extends past the proximal interphalangeal joint is managed with similar flap design and skin grafting. A smaller amount of webbing can be treated with local flap coverage without supplemental skin grafting. Placement of 2 opposing Z-plasties (aka butterfly flap) is a favored technique that provides a wide dorsal flap for commissure reconstruction (Fig 11).2 However, this technique requires supple skin and is not applicable when there is scar contracture about the web space, such as during revision surgery. In these instances, standard syndactyly technique combined with additional skin graft is preferred.
COMPLEX SYNDACTYLY FIGURE 9. Closure after release of complete syndactyly and addition of supplemental skin graft.
appearance of the separated digits. The commissure flap is sutured first to assess placement and configuration of the web space (Figure 8). Subsequently, the interdigitating flaps are approximated, and excessive tension is avoided. An absorbable 5-0 or 6-0 suture is used for closure. The remaining skin defects are covered with a full-thickness skin graft (Fig 9). Proper postoperative dressings are an essential part of the operation (Fig 10). The dressings must apply compression across the skin graft sites and protect the separated digits. Nonadhering dressing and moist cotton are placed into the web spaces and reinforced by large amounts of soft gauze. In young children, the compressive hand dressing must be reinforced by above-the-elbow plaster immobilization to prevent inadvertent removal. A sugar-tong splint wrapped around the elbow and over the hand protects the digits and allows the elbow to be positioned in greater than 90° of flexion. The dressings are removed 2 weeks after surgery, and gentle washing and wound care are initiated. The wounds are kept covered for an additional week until the scabs desiccate and detach. Normal hand use is encouraged, and formal therapy is usually not required. Scar massage, silicone gel sheets, or elastomere products can treat areas of hypertrophic scarring. Simple Incomplete Syndactyly Web-space deepening of partial webbing of the fingers follows the same principles as complete syn-
omplex syndactyly adjoins the soft tissue and bone along a portion or the entire length of the adjacent digits. This form of syndactyly is less common than simple syndactyly and more challenging to treat, especially as the quantity of bony union increases. Union between the distal phalanges creates a combined fingertip with a coalescence of the nail bed. Proximal flap design follows identical principles as simple syndactyly release. After elevation of the proximal flaps, incision along the groove in the nail divides the terminal synostosis and synonychia. Separation of the fingertips creates exposed bone and absence of a nail fold that require particular treatment. The fingertip can be treated by excision of a central nail and matrix wedge, which allows closure and formation of a lateral nail fold (Fig 12). This reduction maneuver
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FIGURE 10. Sugar-tong splint wrapped above the elbow immobilization and over the hand to protect the digits and minimize chance of inadvertent dressing removal.
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FIGURE 11. Diagram of 2 opposing Z-plasties (aka butterfly flap) to provide commissure reconstruction in incomplete syndactyly.
provides adequate closure but tends to narrow the fingertip. A variety of coronal or palmar flaps have been offered as alternatives to provide nail fold recreation and skin coverage without sacrificing width.8 These long flaps recreate the nail margin but require careful handling to prevent necrosis. Composite grafts harvested from the toes have also been used to provide pulp tissue and better nail margins.9 These grafts should be slightly oversized (25% to 33%) to compensate for the linear contraction of the dermis and attrition of the adipocytes. Another option involves using a preliminary pedicle flap (thenar or abdominal)
to augment pulp tissue before formal syndactyly reconstruction.1 Determining the correct plane of cleavage, realigning the joints, and managing the soft tissue are the difficult issues in complex syndactyly. Identifying the proximal and distal extents of the bony connection and probing for an interconnecting ridge or axilla can guide division. Actual separation of the bone into individual components can be accomplished by using a knife blade. The soft tissue coverage is more difficult, and neurovascular anomalies are more frequent, which complicates surgical reconstruction. Strict guidelines for surgical reconstruction are impossible to provide, and treatment must be individualized.
COMPLICATED SYNDACTYLY omplicated syndactyly is a broad category that encompasses many difficult forms of abnormal web space connection and bony abnormalities. Many of these cases are associated with a syndrome, most notably Poland’s (symbrachydactyly), constriction bands, or acrocephalosyndactyly. The treatment algorithm is more involved and often requires experience in congenital hand surgery. A meticulous physical examination and parental discussion are essential components during formulation of a treatment strategy. In many instances, the definitive surgical plan cannot be developed during a single examination, and repeat
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FIGURE 12. Reduction of fingertip via excision of a central nail and matrix wedge for formation of a lateral nail fold with subsequent narrowing of the fingertip.
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FIGURE 13. Four-year-old girl with complicated syndactyly of ring-small fingers (dorsal view).
assessment of the child is necessary. A variety of props and gentle persuasion are required to evaluate overall hand and individual digit use. There are instances of complicated syndactyly that represent contraindications to surgical intervention (Figs 13-16). In these instances, the connected digits function better as a unit than as separate entities. This is especially applicable in children with a normal thumb and a conglomeration of fingers with bizarre bone and joint anomalies. This decision requires a careful explanation to the parents with reference to the importance of a normal thumb and opposable digit(s) for hand function. The decision not to intervene is often more difficult to explain to the parents than the decision to perform surgery. However, the creation of multiple individual digits with insufficient motion for hand function must be avoided. The surgical treatment of complicated syndactyly uses many of the established principles for simple syndactyly, although modification is necessary to circumvent many of the peculiar findings. In addition, intricate skin and soft tissue procedures have been
FIGURE 14. Palmar view indicates relatively equal lengths and skin (joint) creases.
FIGURE 15. Radiograph shows intact distal and middle phalanges but absent metacarpal and proximal phalanges.
developed for various types of complicated syndactyly. The following section will discuss particular forms of complicated syndactyly associated with a variety of generalized skeletal anomalies or syndromes. Symbrachydactyly and Chest Wall Anomaly (Poland syndrome) Poland syndrome is an ipsilateral anomaly of the hand and chest wall.10 The clinical findings are variable, ranging from mild to severe. The mild form is classically described as a small hand with incomplete simple syndactyly and an absence of the sternocostal
FIGURE 16. Full flexion and ability to make a fist coupled with absence of proximal support negates attempts at digital separation.
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FIGURE 17. Seven-month-old child with constriction band syndrome affecting both hands. Right hand shows rings of varying severity. Left hand shows acrosyndactyly and proximal sinus cleft.
portion of the pectoralis major muscle. The brachydactyly component characteristically involves the middle phalanx. More severe forms involve progressive bony reduction beginning in the central digits and resembling a central deficiency. Successive thumb and small finger involvement can occur, culminating in a complete transverse deficiency of all digits. The proximal muscle deficiencies and breast underdevelopment can also progress to a hollow chest wall deformity with complete absence of the breast. Simple incomplete syndactyly associated with Poland’s syndrome is separated in a manner similar to conventional syndactyly. Distal bifurcation of the neurovascular bundles is fairly common and must be treated accordingly. The digital hypoplasia, associated neurovascular anomalies, and underlying syndrome appropriately classify this syndactyly as complicated. The extent of involvement between the digits dictates the necessity of supplemental skin graft. The commissure should be placed further proximal to create digits that appear longer. Despite proximal commissure placement, the affected digits and limb will always be undersized, and realistic expectations must be conveyed to the parents. Syndactyly and Constriction Band Syndrome Syndactyly associated with constriction bands is not hereditary and is often referred to as pseudosyndactyly or acrosyndactyly (distal connection of digits)(Fig 17). The cause remains controversial with intrinsic and extrinsic theories.11 The intrinsic theory states that the amniotic bands represent a localized lack of mesodermal development, similar to a normal skin crease. The depth of the mesodermal defect deter-
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mines the severity of clinical presentation. The extrinsic theory reasons that either the amniotic membrane traps the developing hand or an amniotic band encircles the affected part, leading to a variable amount of injury. Mild digital damage initiates an embryonic repair process and yields variable amounts of circumferential stricture. This inflammatory response can merge adjacent digits distal to the rudimentary web. Complete vascular ischemia results in truncation of the digits and syndactyly of the affected parts at the site of amputation. Currently, the extrinsic hypothesis is favored, because amnion has been found in the constriction ring, and the bands tend occur in a straight line across multiple digits. Irrespective of the magnitude of constriction, a web space or sinus cleft remains present between the volar and dorsal aspects of the digits (Fig 18). Surgical reconstruction follows the principles established for syndactyly release, although modifications are necessary to accommodate the peculiar anatomy. Unfortunately, any available web space is often placed too distal, and formal commissure reconstruction is required. The cleft or sinus tract often represents an obstacle to flap design and is usually excised and discarded. The skin proximal to the residual web space can be incorporated into the commissure flap design.
FIGURE 18. One-year-old child with distal syndactyly and truncation of long and ring finger. A small proximal cleft is present, which is characteristic of constriction band syndrome.
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FIGURE 19. Three-year-old child with central deficiency and marked narrowing of the thumb-index web space.
FIGURE 20. Elevation of rabbit-ear flap from cleft for transposition into thumb-index web space.
The distal parts of the digits may be conglomerated or ballooned into a single mass, which creates considerable surgical difficulty. Determination of the digital orientation, growth potential, and function is often difficult. Future surgical procedures and the ultimate functional goal of the involved hand are important components to consider. In certain cases, digital separation is not possible. In other instances, digits of unequal length can be treated with a 2-staged reconstruction. The initial procedure divides the distal connection between the digits to prevent progressive angular deformity. Formal commissure reconstruction is delayed until an accurate analysis of digit individuality can be performed.
dorsal rotation flap for adequate deepening. Severe thumb-index narrowing can be treated at the time of cleft closure by using an ingenious flap harvested from the cleft and transposed into the thumb-index commissure (Figs 20 and 21).13 Apert Syndrome Apert syndrome, or acrocephalosyndactyly, is rare and represents a constellation of congenital anomalies that necessitates a multidisciplinary approach to management.14-16 These physically and mentally challenged children require care from various subspecialists. Neurosurgeons must monitor the cranial deformities, maxillofacial surgeons manage the mid-
Syndactyly and Central Deficiency Central deficiency and syndactyly can occur jointly in the same hand.12 The syndactyly affects the ringsmall and/or thumb-index web space. The ring-small web space syndactyly is usually purely soft tissue (simple) and is treated by conventional release and skin grafting. The extent of thumb-index syndactyly is variable and requires individualized treatment (Fig 19). Progressive syndactyly is associated with malrotation of the thumb into the plane of the other digits, intrinsic muscle anomalies (primarily opposition), and extrinsic tendon dysfunction.12 Mild thumb-index syndactyly can be managed by web deepening and local flap coverage. A 4-flap Z-plasty deepens the web and provides a more rounded contour than a 2-flap configuration. Moderate involvement requires a local
FIGURE 21. Cleft closure and flap insetting to narrow the central deficiency and resurface the thumb-index commissure.
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FIGURE 22. Five-year-old child with type I syndactyly (spade hand) with coronal syndactyly of central digits and simple incomplete syndactyly of ring-small web space.
fascial anomalies, otolaryngologists address the potential airway obstruction, and hand surgeons treat the upper-extremity anomalies. The hand anomalies are consistent and include a shortened thumb with radial deviation, complex syndactyly of the index, long, and ring digits with symphalangism, and simple syndactyly of the ringsmall web space.15,16 There are 3 types of hands defined according to the thumb position and overall appearance.15 Type I (“spade hand”) is the least involved and is characterized by a coronal syndactyly of the central digits (distal ends), creating a flat palm (Figs 22 and 23). The radially deviated thumb is not incorporated into the central syndactyly, although the web space is shallow. Type II (“spoon hand” or “mitten hand”) is more involved, because the thumb is drawn into the index digit, creating an incomplete or complete syndactyly. The thumb retains a separate nail matrix and the palm is concave. Type III (“rosebud hand” or “hoof hand”) is the most severe form and incorporates the thumb into the complex syndactyly forming a broad conjoined nail (synonychia) and bony fusion between the radial four digits. The small finger remains segregated from the bony union, but simple complete syndactyly is present. The congested palm is cup-shaped and laden with deep crevasses. The presence of metacarpophalangeal joints provides markers for commissure reconstruction. Considerable neurovascular anomalies are present, especially
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within the central conglomeration of digits.15 Distal bifurcation of the common digital arteries and median nerves is frequent, which complicates separation of the complex central syndactyly. Extrinsic flexor and extensor tendon abnormalities are also widespread, and peculiar intrinsic muscle anatomy is prevalent. Syndactyly correction in these cases is a formidable task that requires multiple procedures to obtain digital independence.14,16 Similar to simple syndactyly, priority is given to separation of border syndactyly for prehensile function and to allow unimpeded growth without additional deformity. The thumb-index and ring-small web spaces can be created at the same time. The technique for first web reconstruction varies with the extent of web space insufficiency. Mild deformity can be corrected with a 4-flap Z-plasty, moderate involvement may require a local dorsal rotation flap, and severe syndactyly necessitates more complex alternatives (eg, radial forearm flap). A distal branching pattern of the princeps pollicis artery to the index digit is frequently encountered during reconstruction of the first web space and must be managed appropriately.16 An effort to preserve this branch will facilitate later separation of the index, long, and ring syndactyly. The ring-small web space is recreated using standard techniques for syndactyly separation. The index finger is released about 6 months after separation of the border digits (Fig 24). A standard dorsal commissure flap and interdigitating zigzag incisions are used with skin grafting to the residual uncovered areas. Neurovascular anomalies are common, and the bundles must be identified and treated accordingly. An attempt is made to preserve any blood
FIGURE 23. Bilateral hand radiographs show distal union of central digits with associated symphalangism.
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FIGURE 24. Syndactyly separation and commissure reconstruction of index-long web space with supplemental skin graft.
supply to the central conglomerate in preparation for later division. After segregation of the thumb, index, and small digits, the long-ring syndactyly is assessed for possible release. Complex interconnections and marked skin deficiency must be considered when planning separation. Options include leaving the digits conjoined, amputating the long digit at the metacarpophalangeal joint (ie, creation of a 3-fingered hand), and performing syndactyly release with pedicle groin flap coverage.1,14,16 The specific reconstruction varies with the patient (intellect, compliance, motivation), mobility of the digits, and surgeon preference. Complications Certain complications are predictable and should be discussed with the parent before surgery. One third of patients with isolated syndactyly and two thirds of those with complex or complicated syndactyly will require additional surgery.1 Therefore, follow-up should continue until adulthood. The parents should also be informed that surgery for complex or complicated syndactyly cannot transform anomalous digits into normal counterparts. Underlying deficiencies in the bones, joints, and tendons prohibit such extraordinary results. Acute. Skin graft failure can occur as a result of hematoma, seroma, or loss of the postoperative bandages. Skin graft loss is more common in infants,
because graft tension is more difficult to obtain and dressings are more prone to inadvertent removal. A very small amount of graft loss is inconsequential and will heal by secondary intention. However, any substantial loss requires repeat grafting to prevent hypertrophic cicatrix formation, which leads to an unacceptable result. Flap loss is less common and is associated with improper design or excessive tension. A zigzag configuration with tip angles of less than 45° increases the incidence of necrosis and should be avoided.1 Appropriate width of the flaps (ie, midline to midline) ensures adequate digital coverage and lessens tension during insetting. Judicious defatting of the subcutaneous tissue also decreases flap tension and eases insetting. Circumferential tension created by flap tightness can also jeopardize digital perfusion. Digital circulation must be assessed before dressing application, which should be compressive but not constrictive. Digital loss is exceptionally rare after syndactyly release. Inadvertent vessel injury requires detection and appropriate management dependent on the status of the other proper digital artery. Prompt intervention may be necessary to restore vascular inflow and avoid digital loss. Chronic. Web creep is the distal migration of the reconstructed commissure with growth (Fig 25). The reported incidence is extremely variable (7.5% to
FIGURE 25. Twelve-year-old child with distal migration of the web space (web creep) requiring revision.
SYNDACTYLY 䡠 KOZIN
60%) and partly related to the inaccuracies in normal web space determination.17 A variety of methods have been used including clinical evaluation, photographs, line drawings and radiographs.1,17 In addition, there is more to a commissure than measurement alone, and many aesthetic components are not readily quantifiable. Radiograph determination appears to be the most accurate and has been defined according to bone age and degree of ossification.17 However, radiation exposure, cost, and inability to apply the measurement technique in patients with bony abnormalities hinder its clinical applicability. The development of web creep is multifactorial and related to age at surgery, surgical technique, and any acute postoperative problems. Patients younger than 18 months at the time of surgery tend to have more web creep and less-successful outcomes.6 Flawed flap design can lead to inadequate commissure reconstruction, which promotes distal migration of the web. Skin graft characteristics also influence the amount of web creep. Split-thickness grafting is associated with an 8-fold increase in web migration compared with full-thickness.1 Skin graft loss is another cause of web creep secondary to scar formation. Irrespective of proper flap design and meticulous full-thickness grafting, web creep can still occur over time.
13
FIGURE 26. Adolescent with persistent nail plate abnormalities after release of complete syndactyly.
Residual Nail Deformity Despite valiant attempts at nail fold and pulp reconstruction, residual nail deformity is common after separation for complete syndactyly with associated synonychia (Fig 26). Irregular nail appearance and flawed nail formation are often present. Reconstruction options are available, although most patients accept the residual deformity.
ACKNOWLEDGMENT The author would like to thank James H. Dobyns, MD, for his continued support and dialogue.
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10. Ireland DCR, Takoyama N, Flatt A. Poland’s syndrome: a review of 43 cases. J Bone Joint Surg Am 1976;58A:52-58. 11. Wiedrich TA. Congenital constriction band syndrome. Hand Clin 1998;14:29-38. 12. Richterman I, Dupree J, Kozin SH, Thoder J. Radiographic analysis of web height. J Hand Surg [Am] 1998;23A:10711076. 13. Cole RJ, Manske PR. Classification of ulnar deficiency according to the thumb and first web. J Hand Surg [Am] 1997;22A:479-488. 14. Snow JW, Littler JW. Surgical treatment of cleft hand. Transactions of the International Society of Plastic and Reconstructive Surgery, 4th Congress. Rome: Excerpta Medica Foundation, 1967:888-893. 15. Hoover GH, Flatt AE, Weiss MW. The hand and Apert’s syndrome. J Bone Joint Surg Am 1970;52A:878-895. 16. Upton J. Classification and pathologic anatomy of limb anomalies. Clin Plast Surg 1991;18:321-355. 17. Zuker RM, Cleland HJ, Haswell T. Syndactyly correction of the hand in Apert syndrome. Clin Plast Surg 1991;18:357-364.