Syndactyly
Syndactyly describes a variable fusion of the soft tissue or skeletal elements or both of adjacent digits, and it occurs when the normal processes of digital separation and web space formation fail to some degree. During normal development, the digits form as condensations of mesoderm within the terminal paddle of the embryonic upper limb. Spaces form between the fingers in a distal to proximal direction to the level of the normal web space by a process of regulated apoptosis. This process is dependent on the apical ectodermal ridge and the molecular signaling of several cytokines, including bone morphogenetic proteins, transforming growth factor-β, fibroblast growth factors, and retinoic acid. The normal web space slopes 45 degrees in a dorsal to palmar direction from the metacarpal heads to the midproximal phalanx ( Figure 36.1 ). The second and fourth webs are wider than the third web, allowing greater abduction of the index and small fingers. The first web space is a broader diamond-shaped expanse of skin composed of the glabrous skin of the palm and thinner mobile skin dorsally.
General Considerations
Epidemiologic Findings
Isolated syndactyly is a common congenital anomaly of the hand, with an incidence of approximately 1 in 2000. It occurs bilaterally in 50% of cases. Between 10 and 40% of cases demonstrate a positive family history that is inherited as an autosomal dominant trait. Variable expressivity and incomplete penetrance account for the male predominance (2 : 1) and the variable phenotype that is often seen within a family pedigree. Syndactyly is also seen with other deformities, such as polydactyly, clinodactyly, brachydactyly, symphalangism, and synostosis, as part of a broader anomaly of a child’s hand, either as a sporadic occurrence or as part of a syndromic association. In isolated syndactyly, the long finger/ring finger web space is most commonly affected (57%), followed by the ring finger/small finger web space (27%). Thumb/index finger and index finger/long finger web syndactylies are the least common. In syndromic cases, the thumb/index finger and index finger/long finger web spaces are relatively more frequently affected.
Pathologic Findings and Classification
The conjoined digits may show abnormalities of the nails, the digital neurovascular bundles, the skeleton, and the tendon systems. The skin envelope of the fused digits is inadequate to resurface the circumference of each independent digit. The abnormal underlying fascia has a continuous thickened, lateral digital sheet that spans the length of the syndactyly across the potential interdigital web space. Syndactyly is described as complete if the web space extends to include the fingertip and incomplete when the web space occurs anywhere between the normal commissure and the fingertips. Simple syndactyly has only skin or soft tissue connections ( Figure 36.2 ). The joints are usually normal, and the flexor tendon and extensor tendon mechanisms are usually independent. The digital neurovascular anatomy is usually normal, although the bifurcation of the common digital structures may be distal to the level of a normal web. Complex syndactyly is marked by skeletal anomalies. The most common form of complex syndactyly is a side-to-side fusion at the distal phalangeal tuft level ( Figure 36.3 ). This distal synostosis is usually reflected in a synonychia with loss of the paronychial fold and flattening of the nail matrix across the bony mass. Complex complicated syndactylies are those with accessory phalanges or digits interposed within the abnormal web space. The incidence of tendon and neurovascular abnormalities increases with the complexity of the syndactyly.
Preoperative Evaluation
When evaluating a patient with syndactyly, the important features to consider are which web space(s) is involved, the extent of the syndactyly, the involvement of the nail, and the presence of other anomalies. Lack of differential motion between the digits may indicate bony fusion or an extra digit, or both, concealed within the conjoined digits. Examination should include the entire upper limb, the contralateral hand, the chest wall, and the feet. Radiographs may reveal skeletal fusion, a concealed extra digit (synpolydactyly), or other bony or articular deformities. Further imaging with ultrasound or magnetic resonance imaging can be useful in determining the flexor tendon and vascular anatomy in complex cases.
Management Considerations
Syndactyly can have cosmetic, functional, or developmental impacts on the growing child. The appearance of the hand is altered, more so with complete complicated forms of syndactyly. Syndactyly of the first web space hampers grasp and the development of pinch. Syndactyly of the second, third, and fourth web spaces inhibits independent digital motion, particularly abduction, and therefore reduces the span of the hand. Syndactyly between digits of unequal length causes tethering of the longer digit, which deviates toward the shorter digits and may also cause a flexion contracture at the proximal interphalangeal joint (PIP) that progresses with growth ( Figures 36.4 and 36.5 ).
Surgery is indicated for most cases, but contraindications include mild incomplete syndactyly without functional impairment, medical conditions that preclude surgery, or complex syndactylies that risk further functional impairment with attempted separation. On occasion, there are insufficient components in the fused mass to produce independent, stable, and mobile digits ( Figures 36.6 and 36.7 ). This situation typically arises in central brachysyndactyly or synpolydactyly, and separation risks reducing function.
Several important surgical principles apply to the correction of syndactyly, including the timing of the procedure or procedures, staging the releases of multiple web space syndactylies, creation of a commissure, techniques of separation and resurfacing of the digits, and postoperative dressing and aftercare.
Timing of Surgery
Syndactyly release has been performed in the neonatal period or during infancy, or it has been delayed until childhood. Long-term reviews by Flatt and Ger have shown better outcomes with release after 18 months, although early surgery may be dictated by progressive skeletal deviation or deformity. The goal is to complete all the releases by school age. Syndactyly involving multiple web spaces requires staging of the release procedures because only one side of an affected digit should be released at a time to avoid vascular compromise of the skin flaps or digits. Syndactyly of all web spaces is usually treated in two stages. The first procedure separates the thumb/index finger and long finger/ring finger web spaces. Three months later, a second procedure separates the index finger/long finger and ring finger/small finger web spaces. In addition, the first procedure can be combined with isolated release of the fingertips and distal phalangeal fusions of all the digits to reduce the tethering effect between surgical procedures.
Commissure Reconstruction
A basic tenet of syndactyly release is reconstruction of the interdigital commissure with a local skin flap. The most frequently used methods incorporate a proximally based rectangular flap raised from the dorsum of the syndactyly ( Figure 36.8 ). Several modifications have been proposed, including a trapezoid-shaped dorsal flap or a dorsal flap supplemented with lateral wings used to resurface the digits adjacent to the commissure. Alternative choices for commissure skin are available. Skin from the dorsum of the hand raised as an island flap can be advanced in a “V-Y” fashion into the web space. The palmar surface of the syndactyly alone or in combination with the dorsal surfaces of the syndactyly can be introduced into the web space as opposing triangular flaps. Where the syndactyly is incomplete and restricted to the proximal digit, the web may be repositioned by deepening or lengthening the existing web alone by a simple “Z”-plasty, a four-flap “Z”-plasty, or a double-opposing “Z”-plasty (butterfly flap) ( Figure 36.9 ). Other methods in this situation include combinations of local flaps, such as the three-flap web-plasty or an “X-M”-plasty. Incomplete syndactyly can be deceptive, as there often appears to be an abundance of local skin available. However, following commissure reconstruction and transposition of the local flaps, a skin defect is common in the proximal digital surface, with excess skin located distally. Brennan has described a technique to address this situation by raising the distal skin as island flaps that are advanced in a proximal direction and combined with triangular flaps for commissure reconstruction.
Syndactyly of the first web space presents a special problem and varies in extent. First web syndactyly is more common in syndromic disorders such as Apert syndrome and is often associated with a thumb deformity. It hampers hand function more severely than does syndactyly of the other web spaces. Mild to moderate first web space syndactyly can be treated with a local flap, such as a four-flap “Z”-plasty ( Figure 36.10 ). Other options include a transposition flap from the index finger, a combination of transposition flaps from the radial and ulnar borders of the index and thumb, respectively, or a “V-to-Y” advancement of the central web.
Severe syndactyly with marked thumb/index web narrowing may require more skin than is available in local flaps. In this situation, skin may be imported from the dorsum of the hand after tissue expansion or as a rotation advancement flap ( Figure 36.11 ). Pedicled flaps such as the radial forearm or free flaps from distant sites such as the groin can also be used. Despite the complexity, free flaps import skin of excellent quality to the hand in cases of severe skin deficiency associated with syndromic syndactyly.
Separation and Resurfacing of the Digits
Release of syndactyly requires careful planning to optimize use of the available skin and to allow surgical exposure for separation of digits and structures. Incision design must be placed such that inevitable scar contraction will avoid joint or web space contracture. Numerous patterns of skin incisions have evolved, including laterally based triangular and rectangular flaps. Cronin’s technique of a combination of palmar and dorsal triangular flaps with matched zigzag incisions on both surfaces of the conjoined digits remains the basis of most techniques ( Figure 36.12 ). Modifications of this pattern have been proposed to redistribute the available skin in an unequal manner to avoid skin grafting on both sides of the commissure ( Figure 36.13 ). Syndactyly release has also been performed with straight-line midlateral incisions closed with skin grafts, which are splinted to prevent contracture and subsequently serially excised to leave an acceptable midlateral scar, or with direct closure after defatting of the skin flaps. This is a departure from the traditional technique but may be of benefit when grafts and scars are at risk of pigmentation and hypertrophy. Another alternative approach is the “open finger” technique of Sommerlad, where the residual skin defects resulting from separation of the digits are left open to heal by secondary intention. However, most surgeons fear the secondary cicatrix formation with scar contracture and hypertrophic scarring and so are reluctant to endorse this method.
Separation of the digits requires division or excision of fascial interconnections between the digits, with care taken to identify and preserve the individual neurovascular bundles and the venous plexus on the dorsum of the digits and of the commissure flap ( Figures 36.14 and 36.15 ). Bifurcation of the common digital nerve and artery may be distal to the planned position of the web space. In this situation, the digital artery can be ligated provided the other side of the digit is unoperated or the contralateral digital artery is known to be intact. Otherwise the web release is limited to the level of the arterial bifurcation or the artery is extended with a vein graft (very rarely necessary). When multiple digits are released, each digit must have at least one digital artery remaining; hence, the importance of precise operative records in such cases. Distal bifurcation of the digital nerve is managed by interfascicular dissection and proximal separation.
Resurfacing the digits is achieved with the palmar and dorsal flaps raised from the conjoined digits supplemented with skin grafts. Full-thickness skin grafts are preferred over split-thickness skin grafts to lessen secondary graft contracture. Skin grafts are usually obtained from the inguinal donor site. Alternative donor sites include the antecubital fossa, the hypothenar border of the hand ( Figure 36.16 ), the forearm/wrist ( Figures 36.17 and 36.18 ), and the skin of an accessory digit. The foreskin has been used, although it tends to take poorly and develop pigmentation. The authors favor the medial upper arm, believing skin from this area is less likely to manifest unpredicted hair growth at maturity and is less likely to develop pigmentation than the inguinal grafts. Regardless of the chosen donor site, a careful explanation and consent are mandatory because the scar may hypertrophy.
Resurfacing the digits without skin graft has been performed to improve overall skin match and to avoid the risk of contracture associated with graft loss. This technique may require some reduction of digital diameter by excising the subcutaneous fat of the digit while preserving the dorsal venous system. Extensive defatting, however, carries the risk of vascular or nerve injury and may lead to a thin finger after the involution of the fat of infancy. Another option to avoid skin grafting is to import skin from the dorsum of the hand and/or adjacent digits ( Figure 36.19 ). The authors favor a dorsal flap from each adjacent finger as part of a trilobed commissural flap. In theory, more skin can be generated with tissue expanders, although this technique has limited success in syndactyly. Tissue expansion has also been achieved with transverse soft tissue stretching through the use of a distraction frame. Neither of these techniques has been widely adopted.
Paronychial Fold Formation
Release of a complete syndactyly, particularly when associated with distal phalangeal fusion, requires the formation of a paronychial fold. The distal phalangeal tufts may be covered using the technique described by Buck-Gramcko. Laterally based long narrow triangular flaps are raised from the hyponychium of the conjoined digital mass and folded around to form the lateral nail fold ( Figure 36.20 ). Alternatively, the defect may be resurfaced with a skin flap from the conjoined pulp for one of the nail folds and a subcutaneous fat flap from the conjoined pulp covered with a graft for the other nail fold. Distant skin flaps including a thenar flap have been used, but this technique requires delayed division and a second surgical procedure and in all but the youngest child, risks a PIP joint contracture. A composite graft of skin and subcutaneous fat harvested from the toe can also be used to reconstruct the fingertip.
Outcome
The complexity and technical demands of syndactyly release are often underestimated. What appears to be simple surgery requires careful three-dimensional planning, careful technique, and meticulous wound closure. The procedure is often time consuming and demands patience. An acceptable outcome with independent digits that are freely mobile is usually achieved with simple syndactyly separation. In contrast, the outcome after complex syndactyly separation is often limited by associated anomalies and severe skin shortage, which result in increased scarring and diminished mobility.
Complications
Early complications include vascular compromise, infection, wound dehiscence, and graft loss. Tension-free wound closure is mandatory to prevent dehiscence and may require judicious defatting or skin grafts or both. Over time, the commissure may be drawn in a distal direction (web creep) by scar contraction ( Figure 36.21 ). Poor flap design with placement of longitudinal scars at the base of the finger can precipitate web creep. Web creep is also associated with areas of skin graft loss that heal by secondary intention, the use of split-thickness grafts, or the dehiscence of the commissure flap. Joint contractures are a result of contracture of scars on the palmar surface of the interphalangeal (IP) joint. This complication may require scar revision with further skin grafting or, where there is adequate skin, a “Z”-plasty to reorient and lengthen the scar. In the fingertip, inadequate soft tissue bulk and scarring can produce a beaked nail deformity or an inadequate paronychial fold. Lastly, joint instability may occur after separation of complex syndactyly owing to insufficient collateral ligaments.
Authors’ Preferred Method of Treatment
In simple syndactyly , the preferred technique depends on the specifics of the deformity. Where the syndactyly is incomplete or loose and resurfacing without skin graft is feasible, that is our preferred method. Because incisions differ between techniques, the decision of whether a graft will be needed must be made prior to surgery.
Release of syndactyly is performed with the patient under general anesthesia using a tourniquet and loupe magnification.
If release will involve skin grafts, an hourglass-shaped dorsal flap is preferred for commissure reconstruction (see Figure 36.8 ). The flap begins at the level of the metacarpal heads and extends for 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 (see Figure 36.13 ). The proximal transverse incision represents the palmar 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. The dorsal zigzag incision begins at one distal corner of the commissure flap, whereas the palmar incision starts at the opposite corner of the rectangular flap (see Figures 36.8 and 36.13 ). The dorsal incision extends to the midline of the PIP joint of the adjacent finger and back across to the midline of the distal interphalangeal (DIP) joint. At this level, the incision extends distally 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 PIP and DIP joints to allow for interdigitation. It can be helpful to mark the level of the peak of each flap with encircling ink-stained suture material to facilitate accurate apposition of the peak on one digit with the trough of the opposite digit. This orientation minimizes the tendency for formation of a flexion scar contracture and maximizes coverage potential. The palmar rectangular flap (opposite the dorsal commissure flap) and zigzag construction is often biased to cover one digit entirely, leaving residual bare areas on the adjacent digit that requires skin grafting. This has an advantage in requiring fewer grafts and a shorter operative time.
The flaps are elevated by sharp dissection with hemostasis using bipolar electrocautery. Dorsal flaps are elevated first, preserving the paratenon surrounding the extensor tendon. Next, the palmar flaps are raised and the underlying neurovascular bundles identified distally. The digits are separated from distal to proximal while protecting the neurovascular bundles. Manual spreading of the digits places the intervening tissue under tension, which facilitates digital separation (see Figure 36.14 ). The sturdy transverse fascial bands are incised to allow for sufficient proximal placement of the commissure. The bifurcation between the common and proper neurovascular structures is identified during proximal dissection (see Figure 36.15 ). A distal split of the digital nerves is easily separated by microdissection. The surgical options when the arterial bifurcation is distal to the desired web position are described in the text above. Ligation of a proper digital artery for an acceptable commissure placement is usually 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 artery is usually ligated. However, if one of the digits still requires additional surgery (e.g., staged syndactyly release), then ligation of the larger artery may be considered. If the status of the opposite digital artery is unclear, microvascular clamps are applied to the digital arteries and the tourniquet is deflated to ensure adequate perfusion of each digit.
Before insetting of the flaps, the adjacent sides of the separated digits are defatted ( Figure 36.22 ). Defatting decreases the tension across the flaps and improves the overall appearance of the separated digits. Abnormal or contracted fascial structures may be encountered and are also released or excised at the time of this defatting. The commissure flap is sutured first to assess placement and configuration of the web space. Subsequently, the interdigitating flaps are approximated, avoiding excessive tension. An absorbable 5-0 or 6-0 suture is used for closure, and sutures are placed very close to the skin edges to avoid cross-hatched scarring. The remaining skin defects are covered with full-thickness skin graft ( Figures 36.23 and 36.24 ).
In select cases, an experienced surgeon may decide that skin grafts may be avoided with a trilobed dorsal flap for construction of the commissure. This design requires the harvesting of skin from the dorsum of the adjacent digits, and so, in return for a potentially more pliable web and no pigmented skin grafts, a less discrete dorsal scar is formed.
Proper postoperative dressings are an essential part of the operation. The dressings must apply gentle compression across the skin graft sites and protect the separated digits. Nonadherent dressings and moist cotton are placed into the web spaces and reinforced with large amounts of soft gauze. In young children, the compressive hand dressing is reinforced by above-the-elbow plaster or a soft cast (Scotchcast, 3M, St. Paul, MN) to prevent inadvertent removal. The elbow is positioned in at least 90 degrees of flexion to minimize the chances of the cast sliding off the arm. The dressings are removed 3 weeks after surgery, and then gentle washing and wound care are needed. The wounds are protected until they are dry and healed. Normal hand use is allowed after the dressing has been removed. Physiotherapy is usually not required. Once healing has taken place, an elasticized compression glove may be fitted and worn for up to 3 months for scar management. Scar massage, silicone gel sheets, or elastomere products can be used to treat areas of hypertrophic scarring.
Special Cases of Syndactyly
Acrosyndactyly
Acrosyndactyly is a syndactyly with a fenestration between the digits proximal to the distal fusion and is characteristic of constriction ring syndrome (amniotic disruption sequence) ( Figure 36.25 ). It is bilateral in 50% of cases and is associated with absent digits in 50% of patients. The syndactyly can vary from a simple syndactyly to a complex anomaly with distal fusion of multiple digits producing a jumble of fingertips. The sinus is variable in size (from the size of a pin tract to a broad passage) and is usually distal to the normal commissure level ( Figure 36.26 ). The digits distal to the constriction ring may be edematous, atrophic, or skeletally disrupted.
Management is dependent on the severity of the distal deformity and the position and size of the sinus. Mild deformities with well-preserved distal digits can be released with the standard techniques as described previously. The sinus may be incorporated during resurfacing of the digits or excised. For more complex deformities, staged release of the fingertips followed by delayed commissure reconstruction is recommended. Staging allows unimpeded growth of the digits. In severe deformities, amputation of disorganized or atrophic fingertips may be preferred because the potential for reuniting them with the parent digit is limited. In addition to the syndactyly release, associated constriction rings can be managed by excision and “V-Y” plasty.
Apert Syndrome
Apert syndrome describes the combination of bicoronal craniosynostosis and midfacial hypoplasia with severe complex syndactyly of the hands and feet. It is due to a mutation of the fibroblast growth factor receptor type 2 gene (FGFR2), which is located on chromosome 10q. Several other acrocephalosyndactyly syndromes have been identified; however, the hand deformities are typically less complex than those of Apert syndrome. In addition to the characteristic hand deformity, upper limb manifestations include abnormalities of the shoulder and elbow. The development of the glenohumeral joint is asymmetric, with relative overgrowth of the greater tuberosity and a hypoplastic glenoid fossa. Shoulder movements become more restricted with growth. Elbow anomalies most commonly involve the radiocapitellar articulation.
The hand deformities in Apert syndrome include complex syndactyly of the index, long, and ring fingers and a simple syndactyly between the ring and small fingers. Varying degrees of first web space syndactyly prevent useful prehension, which is exacerbated by radial clinodactyly of the thumb ( Figure 36.27 ). The fingers are short, and IP joints are stiff in the central rays. In the most severe cases, the distal phalanges of all of the fingers are fused to each other and growth of the fingers results in a rosebud or bunched appearance with a deep hollow in the palm caused by the tethering distally. Frequently, nail fold infections result from overlapping and ingrowth of the tightly adjacent nail plates. A capitohamate coalition and synostosis between the ring and small metacarpals is frequent ( Figure 36.28 ). This finding is clinically important because it prevents opposition of the fifth digit toward an already restricted thumb. There is an inverse relationship between the severity of the hand and craniofacial deformities. The hand deformity has been classified according to the involvement of the first web space and conformation of the central mass ( Table 36.1 ).
| Type | First Web | Central Mass | Fourth Web |
|---|---|---|---|
| Type 1 Obstetrician hand or spade hand | Incomplete simple syndactyly | Digital mass flat in palmar plane. Good metacarpophalangeal joints with variable degree of symphalangism at interphalangeal joints | Incomplete simple syndactyly |
| Type II Mitten hand or spoon hand | Complete simple syndactyly | Digital mass forms palmar concavity with splaying of metacarpals proximally and tight fusion of fingertips distally with synonychia of central digital mass | Complete simple syndactyly |
| Type III Hoof hand or rosebud hand | Complete complex syndactyly | Thumb incorporated into mass, which is tightly cupped; synonychia of all digits apart from the small finger; skeletal abnormalities of index ray; Complicated by paronychial infections and maceration of palmar skin | Simple syndactyly, usually with metacarpal synostosis of fourth and fifth metacarpals |
The management of hand anomalies in patients with Apert syndrome must be performed in concert with the management of the craniofacial and other associated anomalies. In practice, this is complex surgery requiring careful coordination between hand surgeons and the craniofacial service. The goal of surgery is to complete separation of the digits and correct the thumb deformity before 2 years of age to allow for growth and the development of function. Surgery to mobilize the small finger by release of the ring and small metacarpals’ synostosis may be beneficial because it allows cupping of the palm and some function between the often better articulated fifth finger and the thumb. Surgery is rarely performed about the shoulder and elbow.
Separation of the digits requires careful planning. Reconstruction of an adequate first web space is the first priority. Sequential single-stage release of the skin and fascia, intrinsic muscle lengthening, and capsulotomy of the carpometacarpal (CMC) joint allow the thumb ray to be positioned in 45 degrees of abduction ( Figure 36.29 ). Minor first web space narrowing can be addressed with local flaps such as a four-flap “Z”-plasty. Considerable narrowing with deficient skin requires a dorsal advancement rotation flap or preliminary tissue expansion on the dorsum of the hand. We prefer to use a transposition flap from the radial border of the index finger for incomplete thumb/index finger syndactyly. The index finger flap can lengthen the first web space and be positioned into the thenar crease to correct any associated flexion-adduction contracture. For severe contracture of the first web space, Buck-Gramcko has described successful release with a large dorsal rotation flap, but our preference is to import new skin to the very deficient hand integument. A free groin is used ( Figure 36.30 ), and this allows the import of large areas of pliable skin while minimizing the donor defect. The groin donor has the potential disadvantage of future pigmentation and hair growth, but the vessels lie within the territory of the flap and appose themselves to the recipient vessels accurately. Substantial tissue is placed within the first web space ( Figures 36.31 and 36.32 ). Contrary to prevalent belief, the vessels within the first web space and the flap are adequate for microvascular anastomosis. However, this is daunting microsurgery, requiring highly specialized anesthesia, and should only be contemplated in units with the resources and experience to perform this surgery. The least disfiguring alternative is probably the dorsal rotation advancement flap; we eschew the pedicled forearm flaps because of the scarring that results and the division of a major axial vessel.
The thumb clinodactyly must be corrected with an osteotomy of the phalanx. An opening wedge osteotomy and a bone graft are preferred to lengthen the shortened thumb. This is best done at the same stage, so that the fixation of the thumb web space release is combined with fixation of the bone graft. The bone graft can be taken from the division of the synostosis between the fourth and fifth metacarpals. Usually, there is a resultant skin shortage on the radial aspect of the thumb that can be addressed with “Z”-plasty.
Release of the finger syndactylies is usually staged, though release of the syndactyly in a single stage has been reported. Anomalies of the neurovascular bundles are common. The surgical plan is influenced by the extent of the first web space reconstruction and the status of the index finger. A severely deformed index finger may be sacrificed if it is unlikely to yield a stable finger of adequate length, though our preference is to preserve all digits. More information about the skeletal abnormality can be assessed with three-dimensional computed tomography, which may be combined with the craniofacial imaging.
When the thumb is released, the opportunity may be taken in the tightly bunched or rosebud hand to release the distal osseous unions via a simple linear incision and to line the raw lateral surfaces with skin grafts, thereby converting the tight bunched hand into the flat “spade” of the type I deformity. This simple maneuver prevents growth distortion, buys time to allow other surgeries, and also serves to prevent the recurrent nail infections that can dominate the early months of hand care in these children. Subsequent releases of the multiple syndactylies are staged to avoid surgery to both sides of the digit at the same sitting.
In this way, we have staged the release of the severely deformed hand by releasing the distal osseous fusion and dividing the common nail plate through dorsal incisions between the distal digits. This converts the complex syndactyly to a simple syndactyly and releases the digits from the osseous tether. The interdigital defects are resurfaced with full-thickness grafts to allow some differential motion between the digits. The grafts generate enough pulp skin to provide adequate pulp and paronychial flaps for the release of the fingers at a later stage. The digits in the Apert hand are stiff in extension, and therefore the release of the proximal part of the syndactyly can be achieved with a straight-line incision, as there is not the same risk of IP joint contracture with longitudinal scars in these digits. The defects are resurfaced with full-thickness grafts, which may need to be harvested as a lower abdominal ellipse rather than from the groin because of the extensive area of graft required. Emphasis does need to be given to the commissure reconstruction to allow freedom of independent metacarpophalangeal joint movement. A dorsal commissure flap is usually used.
Surgery to free the small finger may be required if the finger is functional. Release of the synostosis between the ring and small metacarpals should include fascia or fat interposition to prevent recurrence. Upton’s experience suggests that this procedure is best delayed until 5 years of age to decrease the incidence of recurrence, although we like to use the bone resected as a graft for the thumb clinodactyly. Therefore, we accept the risk of recurrence requiring an additional release. The position of the fifth ray may be improved by release of the CMC joint to allow flexion of the metacarpal.
Symbrachydactyly
Symbrachydactyly is from the Greek for “short webbed digits.” Symbrachydactyly occurs sporadically but may be a feature of Poland syndrome. The anomaly is almost always unilateral, and the severity varies from almost complete absence of digits to relatively well-formed short fingers. When the digits are well formed, the syndactyly component requires intervention. The technique may be modified to include division of the transverse metacarpal ligament to increase the mobility and apparent length of the fingers, though the commissure should not be placed in such a proximal position between the metacarpal heads that there is a risk of producing a narrowed, “V”-shaped web space.
Poland Syndrome
Poland syndrome has been attributed to disruption of the blood flow in the subclavian artery in the embryo (hence, it is also called subclavian artery disruption sequence); a spectrum of hypoplastic anomalies in the upper limb is produced. The syndrome consists of absence of a shoulder girdle muscle and abnormalities in the hand, which may be very minor. In fact, there is no correlation between the severity of each component of the deficiencies. Commonly seen conditions are aplasia of the sternocostal head of the pectoralis major (although the clavicular head may also be absent); brachydactyly affecting the index, long, and ring fingers; hypoplasia of the hand; and syndactyly of the digits. The chest wall anomalies may be extensive and include hypoplasia of the breast, aplasia of the pectoralis minor and latissimus dorsi, and skeletal thoracic wall anomalies ( Figure 36.33 ). The hand deformity is variable, but the central digits are most commonly affected and are generally shortened secondary to an undersized middle phalanx. The syndactyly is usually simple and either complete or incomplete. Surgical separation follows the timing and technique described previously. In our service we like to set up a treatment schedule extending from infancy to sexual maturity that combines the management of the thoracic deformity (usually, by ipsilateral muscle transfer) with staged reconstruction of the female breast. The hand surgery should be integrated into this treatment schedule.
Dystrophic Epidermolysis Bullosa
Syndactyly in dystrophic epidermolysis bullosa is not truly a congenital anomaly but rather a consequence of the scarring from this blistering condition of the squamous epithelial surfaces. Epidermolysis bullosa encompasses a rare heterogeneous group of congenital blistering conditions. The skin structure is disrupted by a loss of the normal adhesion between the various lamina of the skin. The variants are classified according to the level and cause of blistering. Epidermolysis bullosa simplex variants blister at the basal keratinocyte level, junctional epidermolysis bullosa blisters within the lamina lucida of the basement membrane, and dystrophic epidermolysis bullosa blisters because of abnormal anchoring collagen VII fibrils within the papillary dermis. Dystrophic epidermolysis bullosa is associated with repeated dermal injury. The inevitable scarring produces syndactyly and contracture in the hands. Autosomal dominant and recessive forms of dystrophic epidermolysis bullosa have been recognized, with the recessive form being the most severe. Typically, the hand deformity progresses toward flexion contractures of the digits that become cocooned into a common mass ( Figure 36.34 ). The thumb can be included within the cocoon. The hand problem, however, is only part of a complex condition that requires a multidisciplinary approach to management. These patients should be managed in specialized multidisciplinary centers with experts in treating the skin, gastrointestinal, ocular, oral, oncologic, psychological, and anesthetic aspects of the disease. The hand surgery is based around release and resurfacing of the syndactyly and contractures. Radical release, particularly of the first web space, is recommended to maintain some hand function. The syndactyly (also named pseudosyndactyly) in this condition is usually caused by adhesion between digits and can be achieved with blunt dissection after removal of the encasing membrane of scar. The dermal scarring generally produces flexion contractures of the digits or first web contractures. We believe that the maintenance of the first web space is the key to useful hand function in these children. For this reason, we consider free tissue transfer from an unscarred flexion area of the body (such as the groin) to be desirable where other considerations permit. Local flaps are usually impossible because of the extensive scarring and cocooning in these highly abnormal hands. The skin deficits can be allowed to heal by secondary intention or by using the skin of the cocoon, skin flaps from filleted fingers, or grafts. Split-thickness skin grafts are preferred, although we have successfully used free groin flaps to resurface the vital first web space. Despite initially satisfactory results, recurrence is common, with reoperation rates of over 50%.
- •
Syndactyly may involve only the soft tissue (simple) or include bony connections (complex).
- •
Atypical forms of syndactyly are labeled complicated and involve either convoluted soft tissue abnormalities or a hodgepodge of abnormal bones. Many atypical configurations occur in conjunction with a variety of syndromes.
- •
Mild incomplete syndactyly that does not interfere with function does not require treatment. In contrast, simple syndactyly of any considerable degree warrants surgical reconstruction of the web space for improved function and appearance.
- •
Border digits (thumb/index finger and ring/small finger web spaces) have marked differences in their respective lengths and should be separated within the first few months of life. This prevents tethering of the longer digit, which results in a flexion contracture and rotational deformity.
- •
Syndactyly that combines digits of relatively equal length (e.g., long/ring finger web space) negates the development of deformity. Separation may be delayed until the child is older and the hand larger to facilitate surgical reconstruction.
- •
Surgical reconstruction should only include one side of an affected digit at a time to avoid vascular compromise of the skin flaps or digit, or both.
- •
Surgical reconstruction of the commissure must be free of skin graft. Creation of a flap to recreate the commissure avoids interdigital contracture.
- •
Complex syndactyly is more challenging to treat, especially as the degree of bony union increases.
Expected Outcomes
The expected outcome of syndactyly release in children with simple syndactyly is a natural-appearing web commissure with pliable skin, unrestricted function, and no distal creep of the web with time; however, it may be complicated by contracture or hypertrophy of the scars associated with surgery and lead to distal creep of the web position. This may require further surgery to reposition the web. The outcomes in complex or complicated cases depend on the extent of the osseous syndactyly and associated anomalies, which often lead to stiffness or deformity of the digit or digits.
Polydactyly
Ulnar Polydactyly
Epidemiologic Findings
Polydactyly can occur on the preaxial (radial) and postaxial (ulnar) sides of the limb. Postaxial polydactyly is frequently inherited via an autosomal dominant pattern but has a variable penetrance pattern. Postaxial polydactyly is more common in Africans and African-Americans. The polydactyly can be bilateral ( Figure 36.35 ). Preaxial polydactyly is more frequent in Caucasians. The prevalence of postaxial polydactyly in African-Americans is estimated to be 1 in 143 live births. In comparison, the prevalence of postaxial polydactyly in Caucasians is estimated to be 1 in 1339 live births. Postaxial polydactyly in a Caucasian individual is sometimes indicative of an underlying syndrome (e.g., chondroectodermal dysplasia or Ellis–van Creveld syndrome) ( Figure 36.36 ).
Classification and Treatment
The supranumerary digit is either well developed (type A) or rudimentary and pedunculated (type B). A small nubbin or scrawny postaxial element (type B) can be removed by ligating the base in the nursery or using local anesthesia with epinephrine and electrocautery in the office ( Figure 36.37 ). Suture or vessel clips can be applied to the base of the digit. The digit will turn gangrenous and fall from the hand. A residual bump or nubbin is the most common complication ( Figure 36.38 ), though other complications have been reported.
A well-developed or nearly normal digit (type A) requires operative ablation. The extra digit is removed, and any important functional parts (e.g., ulnar collateral ligament and abductor digiti quinti) are transferred to the adjacent finger.
Surgical Technique
An elliptical incision around the digit is outlined ( Figure 36.39 ). The incision is extended in a proximal direction to allow adequate exposure. Anomalous tendons are removed with the extra digit. The digital nerves are incised and the digital arteries coagulated. If the ablated digit contains the abductor digiti quinti, the muscle and tendon to the adjacent digit are transferred to restore digital abduction. The skin is closed with absorbable suture and the limb immobilized in a long-arm cast for 3 weeks to protect any ligament and/or muscle-tendon transfer.
- •
Postaxial polydactyly is frequently inherited in an autosomal dominant pattern but has a variable penetrance pattern. Postaxial polydactyly is more common in African-Americans and preaxial polydactyly is more frequent in white individuals.
- •
A small nubbin or rudimentary postaxial element can be removed safely by tying the base in the nursery or using local anesthesia and electrocautery in the office.
- •
Well-developed postaxial polydactyly requires operative ablation with transfer of any important parts (e.g., ulnar collateral ligament and abductor digiti quinti) to the adjacent finger.
Central Polydactyly
Epidemiologic Findings
Central polydactyly is an extra digit within the hand as opposed to along its borders. Central polydactyly is uncommon in comparison with border polydactyly. The ring digit is the most common duplication, followed by the long finger and finally the index digit. Central polydactyly occurs in isolation or as part of a syndrome, such as Grebe chondrodysplasia ( Figure 36.40 ). The central polydactyly may be hidden within a concomitant syndactyly (i.e., synpolydactyly) ( Figures 36.41 and 36.42 ). Identification of synpolydactyly requires careful examination supplemented by radiographic verification ( Figure 36.43 ). Central polydactyly (ring finger duplication) combined with syndactyly has a familial inheritance pattern and has been linked to a gene mutation (HOXD13 gene) on chromosome 2.
Treatment
Treatment depends on the status and extent of the extra digit and the presence or absence of concurrent anomalies, such as syndactyly. A central polydactyly that has a fully formed digit and normal function does not require removal to restore the normal complement of digits ( Figure 36.44 ). An isolated central polydactyly with limited motion is treated by resection of the ray. The span of the hand is maintained by transposition of the adjacent digits or intermetacarpal ligament reconstruction (or both). Synpolydactyly is treated by separation of the syndactyly and reduction of the concealed polydactyly. Surgery is quite difficult and is unlikely to restore normal motion and alignment. Complete removal of the redundant bones is difficult to accomplish without jeopardizing joint structure or digital circulation. Wide surgical exposure is necessary. Flaps are designed for extensive exposure of the underlying bony elements and isolation of the neurovascular structures ( Figure 36.45 ). Creativity and intraoperative flexibility may be required to restore the best functioning digit with components from each part ( Figure 36.46 ). A combination of resection and osteotomy is often necessary to obtain the best digit possible ( Figure 36.47 ). The result is often incomplete resection of the surplus bones, which enhances appearance but does not improve motion. Partial central polydactyly is treated with principles similar to those used for reconstruction of the duplicated thumb ( Figure 36.48 ). Multiple surgeries may be required for central polydactyly, and the outcome may still be disappointing. Similar to complex syndactyly, duplicated digits with complicated connections may be better left untreated rather than separated into individual digits with limited motion and instability.
- •
Central polydactyly is uncommon in comparison with border polydactyly.
- •
Central polydactyly may be hidden within a concomitant syndactyly (i.e., synpolydactyly).
- •
Synpolydactyly is difficult to treat. Separation of the syndactyly and reduction of the concealed polydactyly often result in incomplete resection of the extra bones without an increase in motion.
- •
Central synpolydactyly with complicated connections may better be left untreated than separated into individual digits with limited motion and instability.
Mirror Hand
Mirror hand is a rare congenital anomaly characterized by symmetric duplication of the limb in the midline. Typically, there is a central digit with three digits on each side that represent the middle, ring, and small digits in mirrored symmetry ( Figure 36.49 ). Despite the seven digits, the thumb is absent. Within the forearm, there are two ulnas but no radius is present. The ulnas support duplicated ulnar carpal elements ( Figure 36.50 ); hence the term ulnar dimelia . The preaxial ulna is often short, and the hand is positioned in radial deviation. The soft tissue anatomy is bizarre and complicated. Unpredictable anatomic variations are commonplace. Varying degrees of the deformity complicate the classification and treatment strategies.
The theory that mirror hand is part of a spectrum that culminates in the exceedingly rare anomaly of multiple hands has been presented ( Table 36.2 ).
| Type | Name | Clinical Features |
|---|---|---|
| 1 | Ulnar dimelia | Multiple fingers with two ulnas Type A: Each ulna well formed Type B: Preaxial ulna hypoplastic |
| 2 | Intermediate form | Multiple fingers with two ulnas and one radius |
| 3 | Intermediate form | Multiple fingers with one ulna and one radius Type A: Radius well formed Type B: Hypoplastic radius |
| 4 | Syndromic form | Bilateral, mirror feet and nasal defects characteristic Type A: Sandrow syndrome: two ulnas Type B: Martin syndrome: one ulna and one radius |
| 5 | Multiple hand | Complete duplication of the hand, including the thumb; forearm normal |
Etiologic Findings
The etiologic findings have been attributed to replication of the signaling center that controls radioulnar development. The zone of polarizing activity (ZPA) within the posterior margin of the limb bud polarizes the limb into a radioulnar axis and governs preaxial-postaxial limb development. Transplantation of the ZPA or its signaling molecule, sonic hedgehog protein, causes mirror duplication of the ulnar aspect of the limb (see Embryology section).
Examination of the mirror hand begins with an inventory of the number and function of the digits. The amount of wrist, forearm, and elbow motion is recorded. Limited wrist extension is common secondary to concomitant deficiency of the wrist extensor tendons. There is limited forearm and elbow motion because the presence of two ulnas prevents normal movement. The amount of elbow flexion present is variable and is related to the degree of abnormal elbow anatomy.
Treatment
Treatment is designed to reduce the number of digits to four and reconstruct a thumb from the deleted digits. Selective ablation of the supernumerary digits and thumb reconstruction are the mainstays of surgery. The procedure must reconstruct the first web space and augment the motor function of the preserved thumb via tendon transfer ( Figure 36.51 ). The principles of pollicization and the use of “spare parts” guide construction of the thumb ( Figure 36.52 ). We select the most mobile radial digit for pollicization and remove the stiffer radial digits ( Figure 36.53 ). The skin forming the ablated digits is used to augment the first web space ( Figure 36.54 ).
- •
Mirror hand is rare and characterized by symmetric duplication of the limb in the midline. Typically, there is a central digit with three digits on each side and absence of the thumb.
- •
The forearm often has two ulnas but no radius is present.
- •
The etiologic findings have been attributed to transplantation or replication of the ZPA from the posterior margin of the limb bud into the anterior region.
- •
Treatment consists of reduction of the number of digits to four and reconstruction of a thumb from the deleted digits.
Brachydactyly
The term brachydactyly describes a short finger in which the elements of the digital skeleton are present but one or more are reduced in size. The description can be extended by specification of the bone involved. Brachytelephalangy, brachymesophalangy , and brachybasophalangy refer to short distal, middle, and proximal phalanges, respectively. Brachymetacarpia refers to shortening of the metacarpal. These specific terms are rarely used anymore, because brachydactyly has become the preferred term. Brachydactyly may occur in isolation, as part of a complex hand anomaly, as a constituent of a generalized syndrome, or as a consequence of trauma ( Table 36.3 ). The functional and aesthetic aspects of brachydactyly can range from minimal to considerable, depending on the degree of shortening and the status of the remaining digits. The diagnostic aspects and genetic implications are pertinent to the patient and family.
| Generalized brachydactyly |
|
| Underdevelopment of distal phalanges |
|
| A3 brachydactyly (short middle phalanx of little finger) |
|
| D brachydactyly (stub thumb brachydactyly) |
|
| Brachydactyly with metacarpal shortening |
|
| Brachydactyly with short first metacarpal |
|
| Brachydactyly with polydactyly |
|
| Brachydactyly with syndactyly |
|
| Brachydactyly with cone-shaped epiphyses |
Acrodysostosis |
| Miscellaneous |
|
Epidemiologic Findings
Brachydactyly, as a feature of congenital hand anomalies, is quite common. Anomalies in which brachydactyly is the dominant feature are rare and are typically inherited anomalies with an autosomal dominant pattern of inheritance. These have been classified by Bell into brachydactyly types A to E based on phenotypes expressed within pedigrees. Following the initial description in 1951, the classification has been modified by numerous authors, with additions of variants and subclassifications ( Table 36.4 ). Brachydactyly may also occur as a sporadic anomaly or may be part of a systemic syndrome that does not conform to the classification ( Figure 36.55 ). For example, short metacarpals are seen with pseudohypoparathyroidism or pseudopseudohypoparathyroidism. Lastly, noncongenital brachydactyly can occur after growth plate injury from trauma, infection, or frostbite.
| Type A | A1: Farabee brachydactyly | Principal feature: Short middle phalanges (sometimes fused to distal phalanges). Associated feature: short proximal phalanges of thumbs and great toes. |
| A2: Mohr-Wriedt brachydactyly | Principal feature: Short delta phalanx deformity of middle phalanges, index fingers, and second toes. | |
| A3: Bauer brachydactyly–clinodactyly (brachymesophalangy V) | Principal feature: Short rhomboid or delta middle phalanx of the small finger. | |
| A4: Temtamy brachydactyly | Principal feature: Short middle phalanges of index and small fingers. Associated features: Ring finger middle phalanx short, middle phalanges of toes short, and talipes calcaneovalgus. | |
| A5: Bass brachydactyly | Principal feature: Absent middle phalanges, hypoplastic nails in fingers and toes. Associated feature: Hypoplastic distal phalanges. | |
| Type B | Mackinder brachydactyly | Principal feature: Hypoplastic distal phalanges with absent nails. Associated features: Thumbs and great toes may be normal or duplication of distal phalanges may occur; symphalangism. Syndactyly. |
| Type C | Drinkwater brachydactyly | Principal feature: Short middle phalanx of index and middle fingers. Short delta middle phalanx of small finger. Hyperphalangism of index and middle fingers, with ulnar deviation of these digits. Associated features: Short metacarpals. Symphalangism. |
| Type D | Breitenbecker brachydactyly (stub thumb) | Principal feature: Short distal phalanx of thumb. |
| Type E | Bell brachydactyly (brachymetacarpia/brachymetatarsia) Subclassified by Hertzog | Principal feature: Short metacarpals and metatarsals with phalanges of normal length. Associated features: Short stature. Joint laxity. |
| Type E1 | Short fourth metacarpals and metatarsals. | |
| Type E2 | Variable combinations of short metacarpals and phalanges. | |
| Type E3 | Variable combinations of short metacarpals and normal phalanges. | |
| Other types | Pitt-Williams brachydactyly | Short distal phalanges of ulnar digits, short metacarpals, and normal stature. |
| Sugarman brachydactyly | Short proximal phalanges with symphalangism. | |
| Smorgasbord brachydactyly | Combination of types A2 and D brachydactyly. |
Pathologic Findings
Recent research has identified candidate genes for some forms of brachydactyly through pedigree analysis and DNA examination. Various mutations have been identified that affect digital length. Brachydactyly E has been linked to a Glypican 1 gene mutation on Ch2q; brachydactyly B has been associated with mutations of ROR2 , a tyrosine kinase receptor gene at Ch9q22; brachydactyly Al has been related to nucleotide mutations within the Indian hedgehog gene; and brachydactyly C has been associated with mutations in the gene for growth differentiation factor-5. Deficiencies in a cartilage-derived morphogenetic protein have also been associated with various forms of brachydactyly. The Grebe and Hunter-Thompson chondrodysplasias are associated with severe brachydactyly and have been directly related to a cartilage-derived morphogenetic protein deficiency (see Figure 36.40 ). These mutations account for some forms of brachydactyly; however, a variety of additional genetic mutations have yet to be determined to explain the numerous phenotypes.
Clinical Features
The severity of the digital shortening is variable. Mild shortening may be apparent only because the normal cascade of the digits is disrupted. The most commonly affected phalanx is the middle phalanx, which is the last component of the digital skeleton to ossify. The small finger and the index finger are the most commonly affected digits. Associated anomalies, such as syndactyly, clinodactyly, and/or symphalangism, also exist and often create a greater functional problem than the brachydactyly ( Figure 36.56 ). Careful examination of the remainder of the upper limb, the pectoral girdle, the contralateral upper limb, and the lower limbs is a requisite. Additional limb or chest wall involvement may lead to a diagnosis of a specific form of brachydactyly or a more inclusive anomaly, such as Poland syndrome. Examination of parents and siblings may reveal further evidence of an inherited anomaly, although the phenotype may not be uniform throughout the affected family members because of variable expression. Traumatic brachydactyly is usually identified via a history of injury and subsequent radiographs that reveal physeal arrest.
Management
The management of brachydactyly depends on the degree of shortening, associated anomalies, and status of the remaining digits. In a complex anomaly, brachydactyly may be a relatively minor component compared with the syndactyly, clinodactyly, or symphalangism (or any combination of these abnormalities). As an isolated deformity, the indications for intervention are aesthetic and functional. The appearance of the hand is most affected when there is disruption of the normal hand cascade, particularly the central digits. A short central metacarpal head may be palpable in the palm and interfere with power grip.
Isolated shortening of one metacarpal (brachymetacarpia) is a common finding and commonly affects the ring finger metacarpal in girls. Enthusiasm for surgery on the part of the parents, patient, or surgeon must be tempered by potential problems of lengthening, including joint stiffness, contracture, and loss of hand function. Lengthening of the shortened digital skeleton requires subperiosteal osteotomy of the shortened element, distraction to the desired length, and either bone grafting or fixation until the intercalated subperiosteal defect has ossified (callatosis) or waiting for the bone of the lengthened skeleton to regenerate. The technique varies with regard to the approach, configuration of the osteotomy, and method of bone lengthening (i.e., immediate lengthening versus gradual distraction osteogenesis).
The majority of lengthening techniques have used a dorsal approach to the phalanx or metacarpal. Saito and colleagues described a palmar approach for lengthening short central metacarpals to avoid the dorsal scar, although care is required to preserve the deep branch of the ulnar nerve. Most authors achieve lengthening using a simple transverse osteotomy and a distraction frame for lengthening. Single-stage lengthening has been performed using a variety of bony cuts to achieve stability, including a step-cut osteotomy, chevron osteotomy ( Figure 36.57 ), or dowel-shaped osteotomy. Immediate lengthening of the metacarpal may require soft tissue release, reconstruction of the transverse metacarpal ligaments, and/or advancement of the origins of the interosseous muscles ( Figure 36.58 ). Intercalary bone graft is not usually required in young children but may be required in teenagers, and the callatosis is stabilized with the distraction frame until the skeleton is consolidated. The alternative approach is distraction osteogenesis with osteotomy and gradual lengthening using a distraction frame. Alignment is best maintained with two fixation pins on each side of the osteotomy to prevent palmar or dorsal angulation. Dhalla and colleagues described a technique suited to small bones using only one pin on each side of the osteotomy, supplemented with an intramedullary Kirschner wire to maintain alignment. Advantages of distraction callatosis are concomitant soft tissue lengthening, limiting contracture and stiffness, and the formation of regenerate bone that can negate the need for bone graft. Published results of distraction lengthening for congenital short digits and metacarpals are positive, with mean gains in length of up to 15 mm without the need for bone grafting. Distraction osteogenesis, however, is time consuming and requires cooperation of the patient and parents. The external fixation frame is often in place for more than 4 months to achieve consolidation of the skeleton. Pin loosening and pin site infections can complicate the process, and skeletal lengthening may exceed the soft tissue envelope capacity, producing tender bony prominence of the fingertip.
Authors’ Preferred Method of Treatment
The authors’ treatment preference for brachydactyly secondary to short phalanges is to avoid surgery. Hand function is often normal in patients with brachydactyly, and lengthening is complex; it often produces a stiff or contracted digit, and the aesthetic result may be disappointing. Distraction lengthening of the phalanges has been used in selected cases of shortening combined with an associated deformity, such as angulation. Immediate lengthening combined with angulatory correction is the preferred approach for brachydactyly combined with angulation. An opening wedge osteotomy and insertion of a trapezoidal bone graft restore alignment and achieve length in a single setting. A closing wedge osteotomy should be avoided in a short digit. On occasion, a single flail shortened hypoplastic digit within an otherwise normal or nearly normal hand is treated by ray amputation.
For brachydactyly secondary to a short metacarpal, lengthening is often recommended to restore the hand contour, particularly if a central metacarpal is involved, as is often the case. The authors’ preference is distraction lengthening using a uniaxial distractor. The first stage requires application of the external fixator and osteotomy. Two open or percutaneous pins are placed into the metacarpal on each side of the planned osteotomy site. A dorsal approach is used with the aid of an image intensifier to ensure accurate placement. A distraction frame is applied across the metacarpal. The metacarpal is exposed at the site of osteotomy with retraction of the extensor tendon(s) and cutaneous nerves. A longitudinal incision is made in the periosteum, and subperiosteal dissection is performed to expose the osteotomy site while preserving a sleeve of periosteum. A transverse osteotomy is performed using an osteotome or fine-bladed saw, and the wound is closed. Distraction of the osteotomy site is begun between 4 and 7 days after surgery at a rate of 0.25 to 0.5 mm twice a day. Distraction continues until the desired length is achieved. The frame is not removed until consolidation of the metacarpal (i.e., three cortices visualized on the anteroposterior and lateral films) is apparent radiographically. In some cases, secondary bone grafting may be required. Throughout the period of distraction and consolidation, the patient requires close supervision by the surgeon and hand therapist to ensure that digital range of motion is maintained. Regular radiographs are required to assess the progress of the distraction and identify potential complications of pin displacement and/or failure of the apparatus.
- •
Brachydactyly refers to shortening of the digit or ray within the hand. It can occur sporadically or as part of a syndrome, including a number of inherited anomalies with specific patterns of skeletal anomaly.
- •
The functional and aesthetic impact of brachydactyly varies according to the extent of shortening, the number of digits involved, and whether associated anomalies such as syndactyly, clinodactyly, or symphalangism are present as well.
- •
The most commonly affected bone is the middle phalanx, which is the last component of the digital skeleton to ossify.
- •
Short bones may be lengthened either by bone grafting or by distraction osteogenesis. This may be of specific functional benefit for restoration of pinch function or, in the case of brachymetacarpia, for restoration of the normal cascade of the hand.
- •
The potential complications of lengthening in a congenitally shortened skeleton relate to the associated soft tissues. Joint contracture or stiffness can develop in the lengthened digit and, in some cases, in adjacent normal digits. Enthusiasm for lengthening, particularly of the markedly shortened digit, must be tempered by this consideration.
Brachydactyly
The term brachydactyly describes a short finger in which the elements of the digital skeleton are present but one or more are reduced in size. The description can be extended by specification of the bone involved. Brachytelephalangy, brachymesophalangy , and brachybasophalangy refer to short distal, middle, and proximal phalanges, respectively. Brachymetacarpia refers to shortening of the metacarpal. These specific terms are rarely used anymore, because brachydactyly has become the preferred term. Brachydactyly may occur in isolation, as part of a complex hand anomaly, as a constituent of a generalized syndrome, or as a consequence of trauma ( Table 36.3 ). The functional and aesthetic aspects of brachydactyly can range from minimal to considerable, depending on the degree of shortening and the status of the remaining digits. The diagnostic aspects and genetic implications are pertinent to the patient and family.
| Generalized brachydactyly |
|
| Underdevelopment of distal phalanges |
|
| A3 brachydactyly (short middle phalanx of little finger) |
|
| D brachydactyly (stub thumb brachydactyly) |
|
| Brachydactyly with metacarpal shortening |
|
| Brachydactyly with short first metacarpal |
|
| Brachydactyly with polydactyly |
|
| Brachydactyly with syndactyly |
|
| Brachydactyly with cone-shaped epiphyses |
Acrodysostosis |
| Miscellaneous |
|
Epidemiologic Findings
Brachydactyly, as a feature of congenital hand anomalies, is quite common. Anomalies in which brachydactyly is the dominant feature are rare and are typically inherited anomalies with an autosomal dominant pattern of inheritance. These have been classified by Bell into brachydactyly types A to E based on phenotypes expressed within pedigrees. Following the initial description in 1951, the classification has been modified by numerous authors, with additions of variants and subclassifications ( Table 36.4 ). Brachydactyly may also occur as a sporadic anomaly or may be part of a systemic syndrome that does not conform to the classification ( Figure 36.55 ). For example, short metacarpals are seen with pseudohypoparathyroidism or pseudopseudohypoparathyroidism. Lastly, noncongenital brachydactyly can occur after growth plate injury from trauma, infection, or frostbite.
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
