Plastic surgery

PART VIII

HAND

CHAPTER 89  COMMON CONGENITAL HAND ANOMALIES

ROBERT J. HAVLIK

Congenital anomalies of the hand and upper extremity constitute one of the most frequent disorders that afflict newborn children. The cumulative incidence is often underappreciated because of the large variety of anomalies. Although the exact incidence is difficult to establish because of methodology issues, variability in reporting, and also the racial variations of the individual disorders, the most commonly occurring congenital anomalies of the upper limb are polydactyly, syndactyly, and camptodactyly. To frame this discussion, it is important to remember that approximately 95% of all pregnancies carried to term are “normal.” Overall, the incidence of syndactyly is estimated to be approximately 1 in 2,000 births.1-3 In England and Wales, where detailed population-based comprehensive health statistics are available, the incidence of syndactyly has been established as 1 in 2,400 births.4 Polydactyly shows considerable racial variation and is autosomal dominant in many African Americans. However, if one assumes a relatively similar incidence of syndactyly, camptodactyly, and polydactyly across the broader population, then the combined incidence of these three congenital anomalies of the upper limb would be approximately 1 in 750 births. This places the combined incidence of congenital upper limb anomalies within the same range as that of the most common major congenital anomaly—orofacial clefting, which has an incidence of approximately 1 in 700 births.5 The more complex congenital hand anomalies are less frequent. As a point of reference, Apert syndrome, one of the less frequent anomalies, has an approximate incidence of approximately 1 in 100,000 births. Expanding this incidence figure to the birth rate of the United States, with 4 million births per year, there would only be expected to be 40 children born per year with Apert syndrome in the entire United States.

Optimal management of the child with a congenital anomaly of the hand is a challenging undertaking. Unlike the adult patient, the child is not able to effectively communicate or participate in an examination. The planning for operative treatment must be communicated with the parents. The surgeon must recognize that there is a burden on the family to take time off of work and accompany the child to office visits and the hospital, and therefore should try to maximize clinical progress with each visit. Operative care can be challenging from several perspectives. Appropriate anesthesiology expertise must be available. Of course, one of the most challenging aspects of the more complex hand anomalies is that the anatomy can be, and is often, atypical. A complete and thorough understanding of “normal” anatomy is essential before undertaking the more complex congenital cases. Postoperative care can potentially be limited by noncompliance, both on the part of the child and also by his/her family. Particular care and attention is paid to the postoperative dressing because it can be dislodged. Despite these considerations, the management of congenital hand anomalies represents one of the most gratifying experiences for hand surgeons.

Detailed classification criteria have been developed for congenital hand anomalies. Perhaps, the most recognized comprehensive classification is that developed by the International Federation of Societies for Surgery of the Hand (IFSSH). The IFSSH classification classifies congenital hand anomalies based upon seven categories: (1) failure of formation; (2) failure of differentiation; (3) polydactyly; (4) overgrowth; (5) undergrowth; (6) amniotic band syndrome; and (7) generalized skeletal syndromes.6 The fine details of this classification lie outside the scope of this chapter, but the classification is useful for clarity in communication. The focus of this chapter is upon diagnosis and management of the common congenital anomalies of the hand.

EXAMINATION

Examination of the child’s hand requires some special considerations. The examination is one component of a comprehensive examination, including the torso, head and neck, and lower extremities. Often, the hand surgeon will be the first to recognize important findings that can have significant implications for the child’s overall growth and development. Examination includes a catalog of all components of the upper extremity, from torso to fingertips. Specific attention should be directed toward the musculature of the torso and upper extremities, and to the size of the upper extremity relative to the contralateral side. Passive range of motion is carefully assessed over a full range of motion of the entire upper extremity. Often, this requires that the child be distracted in some manner to accomplish a detailed examination. Although the child may not be able to follow directions, careful examination should be made for the presence or absence of digital flexion and extension creases on the hand and upper extremity. Absence of these creases indicates the absence of motion, which can be secondary to joint, tendon, or neuromuscular anomalies. If the surgeon has questions about the extent of innervation of the hand, the hand can be immersed in lukewarm water for 10 to 15 minutes to assess for “pseudomotor activity,” manifested as wrinkling of the skin over the digital fingertips (Figure 89.1). This can provide significant information regarding digital innervation and denervation.

FIGURE 89.1. Child with median nerve injury and digital ulceration showing wrinkling of ring and little fingers (pseudomotor activity) with lack of pseudomotor activity in median nerve distribution following immersion of hand in lukewarm water for 15 minutes.

EMBRYOLOGY OF THE HAND

In “normal” development, the hand “plate” develops between the fifth and eighth weeks of intrauterine growth.7-9 Hand development is largely driven by concentration gradients of growth factors in local tissues. The hand “plate” develops five ridges through the process of apoptosis, or programmed cell death, between the ridges at 48 days of gestational age.7,9 The process of apoptosis starts distally and progresses proximally. An elegant series of micrographs by Sulik has elucidated this process (Figure 89.2). Digital separation is completed by 51 days of intrauterine age. During the time of digital separation, the ridges undergo progressive proliferation of the mesenchymal tissue, and by 56 days of gestational age, the digits have undergone segmentation and the development of “touch pads.” The appearance of the hand has largely been defined between 48 to 56 days of gestational growth. The failure of apoptosis to occur leads to the occurrence of syndactyly. This pattern of morphogenesis accounts for the relatively low occurrence of thumb–index finger syndactyly, because the first ray is known to separate early in the sequence of differentiation of the hand.

SYNDACTYLY

Syndactyly is derived from the Greek “syn”—meaning together, and “dactylos”—meaning digits. As noted above, the incidence of syndactyly is approximately 1 in 2,000 live births. Syndactyly occurs approximately twice as frequently in males as in females. The most frequently afflicted web space is the long-ring web in the hand, and the second–third toe web in the foot. The long finger–ring finger web space accounts for approximately 50% of all cases of syndactyly,3 whereas the ring finger–little finger syndactyly accounts for approximately 30%, the index finger–long finger syndactyly about 10%, and the thumb–index finger fusion is relatively rare and accounts for only 5% of all cases of syndactyly.1 The majority of syndactyly cases present as isolated occurrences, but 10% to 40% of cases are familial in origin, depending on the series.1 All patterns of genetic inheritance have been postulated based upon pedigree analysis, but the most common pattern seems to be autosomal dominant inheritance with incomplete penetrance.2 Syndactyly is classified by many schemes, but the most direct description classifies syndactyly as complete (extending through the finger tips) or incomplete (extending only partially along the length of the digit), and simple (soft tissue only) or complex (bone or joint fusion).

FIGURE 89.2. (A–C) Embryonic hand development at 48, 51, and 56 days of age illustrates apoptosis between digital rays, separation of rays, and segmentation of individual digits with development of finger pads. (Courtesy of Kathy Sulik, Ph.D., University of North Carolina.)

Depending upon the location within the hand, syndactyly may cause little functional impairment or may cause severe impairment with growth disturbance. The most common syndactyly, with long finger–ring finger involvement, shows little impact on growth because of the similarity in length of the mature digits. In contrast, involvement of the border digits (ring-little or long-index) can cause significant impact on growth, and the uncommon thumb–index fusion causes both severe functional and growth disturbance. Developmentally, the abilities to establish the position of the thumb in space (a cortical function) and to grasp are established by 1 year of age, with further refinement of skills occurring up to 3 years of age.10 Therefore, in cases with thumb–index fusion, separation should be accomplished before 6 months of age. Those cases with involvement of the border digits also require earlier separation because of the inherent length discrepancy of the long-index and ring-little fingers, and the potential for growth disturbance of the afflicted digits. The tethering can cause angular deformity of the longer digit. These digits should certainly be separated by 6 to 9 months of age. Complex syndactyly that involves bony fusion should also be separated by 6 to 9 months of age to prevent growth irregularities. In complex syndactyly with multiple digits involved, such as Apert syndrome, there exists a therapeutic imperative to plan a sequence of operations for completion of digital separation early in life. The timing for surgical release should recognize that maintaining a dressing on the upper extremity to protect the surgical site can become challenging after 12 to 18 months of age.

Surgical planning for separation of syndactyly must observe the three primary goals of hand surgery: (1) enable the patient to position the hand and fingers in space; (2) provide adequate and sensate skin cover; and (3) provide a satisfactory power grasp with the ability to handle objects precisely.1 In the surgical correction of syndactyly, there exist six primary tenets that are observed to obtain these goals: (1) complete separation of all osseous and soft tissue; (2) optimal preservation of both nerves and blood supply; (3) the development of an adequate web space between the digits through the use of an appropriate flap(s) inset without tension; (4) interdigitating flap coverage over the proximal interphalangeal (PIP) joint; (5) development of appropriate distal phalanges and finger tips; and (6) the use of perforated full-thickness grafts for digital resurfacing to minimize the effects of secondary contractures.

In separating the digits, it is generally accepted that for reasons of vascular safety, only one side of a digit should be separated at any given operative procedure. All skin must be meticulously preserved and utilized, but it must also be recognized that skin grafting will be necessary, because there is always a definite deficiency of skin (Figure 89.3). A flap(s) must be created for web space resurfacing, as it provides superior characteristics in terms of healing and suppleness in the web space compared with grafting, which is reserved for shorter segments overlying bony phalanges. One of the most widely used techniques is that using a dorsal skin flap, which was first described by the Indiana plastic surgeons Bauer, Tondra, and Trusler.11 The dorsal flap is designed to extend two-thirds of the distance from the metacarpal heads to the PIP joint (Figure 89.4A). Following this, the second step is designing triangular flaps to cover the PIP joints and break up the grafted area on the lateral finger surface to smaller areas. These flaps provide a more favorable aesthetic result if the dorsal flap is based on the ulnar digit, and the palmar flap is based on the radial digit. Once these PIP flaps are designed, the adjacent triangular flaps extending proximally and distally on both the palmar and dorsal surfaces can be designed (Figure 89.4A). Interdigitating flaps are designed and elevated from the finger tips to create the paronychial folds, as described by Buck-Gramcko12 (Figure 89.4B). The dorsal flap is then elevated en bloc with the underlying fat off of the conjoined Cleland’s ligaments (Figure 89.4C). These ligaments normally provide points of attachment for the lateral digital skin to the bony phalanx, but in syndactyly these ligaments are conjoined. The neurovascular bundles lie palmar to these conjoined ligaments. Following elevation of the dorsal web space flap, the distal dorsal skin flaps are incised and elevated. Once these dorsal flaps are elevated, the conjoined Cleland ligaments can be isolated through limited blunt dissection, freeing the digital neurovascular bundles off of the palmar surface of the conjoined ligaments, and the ligaments cut under direct vision with scissors. The neurovascular bundles are identified and preserved. Following division of Cleland ligaments, the palmar flaps are incised (Figure 89.4D). If there is a distal bifurcation of the blood supply, a microvascular clamp should be applied to assess digital perfusion before any vessel is divided. The tourniquet is released at this point to assess perfusion, so all steps requiring a bloodless field should be completed prior to tourniquet release. If there is no distal bifurcation of the vessels, the palmar skin incisions can be made, preserving the underlying neurovascular bundles. Nerves can be “teased” apart bluntly as indicated. Following digital separation, flaps are transposed and sewn in place, making sure that the inset is not too tight to limit perfusion. If this happens, the flaps are recessed to allow for improved perfusion and larger areas will need to be grafted. The goal is to provide flap coverage in the web space and over the PIP joint. Flap coverage over the PIP joint provides more supple coverage and avoids large sheets of grafted skin that are prone to graft loss (Figure 89.4E, F). Templates can be fashioned and full-thickness grafts harvested from an appropriate site (groin, lower abdominal wall, etc.). The grafts are defatted to the dermal layer, perforated, and then sewn in place. Interrupted sutures allow serum and blood to drain from beneath the graft. Appropriate dressings are meticulously placed and consist of bridal veil (Interface, Dermanet, etc.) with petrolatum, followed by petrolatum-laden gauze (Vaseline gauze or Xeroform gauze) and then cotton batten. A light gauze wrap, or a formal tie-over bolster, is then placed to anchor the web space dressing in place. Next, immobilization of the digits, hand, and extremity is performed. In infants, this can include either a “soft cast” or a long arm cast with the elbow maintained in 90° of flexion to prevent dislodgement. The dressing should be placed with the understanding that if it becomes dislodged, it often requires a return to the operating room under general anesthesia to appropriately replace the dressing and minimize the chance of graft loss. Effective immobilization is crucial to successful graft “take” and survival, which in turn is crucial to the success of the operation. Loss of the graft can lead to distal migration of the web space due to cicatricial contracture of the digit.

FIGURE 89.3. Diagram illustrating basis of skin deficiency in syndactyly.

FIGURE 89.4. Separation of syndactyly. A. Markings for separation of syndactyly. B. A dorsal flap extending from dorsal metacarpal heads two-thirds of the distance to the PIP joint is designed. C. Draw dorsal and palmar flaps over PIP joint. D. Draw flaps for separation of the distal phalanges, complete design of other dorsal and palmar flaps. E. Appearance at end of case. F. Transposition of flaps should avoid large sheet of grafting as in upper illustration, with flaps over PIP joint for flexibility as in lower illustration.

APERT SYNDROME: ACROCEPHALOSYNDACTYLY

Comprehensive treatment of the hand anomalies of Apert syndrome is beyond the scope of this chapter. Apert syndrome consists of both craniofacial and hand anomalies and is associated with a disturbance in the cell surface receptor for fibroblastic growth factor13 (Chapter 23). Hand involvement varies in severity, but has been characterized into three discrete types: (1) type I—obstetrician’s or Spade hand, in which the four fingers are fused and the thumb is largely free; (2) type 2—mitten or spoon hand, in which the thumb is typically joined to the thumb mass by a simple syndactyly; and type 3—rosebud or hoof hand, in which the thumb is joined as a tight osseous or cartilaginous fusion of the thumb to the finger mass.13 Apert is a complex anomaly, with abnormal bones, nerves, joints, and tendons, and represents the severe end of the syndactyly spectrum.

SYMBRACHYDACTYLY

Symbrachydactyly is a frequent component of Poland syndrome, an uncommon deformity of the hand, upper extremity, and chest wall seen in approximately 1 in 25,000 births.14,15 The chest wall deformity includes an absence of the sternal head of the pectoralis major muscle, with preservation of the clavicular head.16,17 In addition, there can be other rib and muscular abnormalities present. In females, there is a hypoplasia or an absence of development of the breast. The severity is variable. The hand can be relatively normal, but is frequently characterized by shortened hypoplastic digits with soft tissue fusion between them. The thumb is frequently involved and may demonstrate syndactyly or a constrained first web space.12 Surgical treatment of these digits requires special considerations. First, if the digits are very hypoplastic, they may be unstable, and separation may not produce significant gain and may actually be a detriment until the child is slightly older and the hand has grown further. Second, the digital neurovascular bundles may divide distally, and this must be taken into consideration in operative planning. Finally, these considerations do not generally apply to the first web space syndactyly/constrained web in symbrachydactyly, and so this surgery should be released and resurfaced earlier.

POLYDACTYLY

Polydactyly, or the presence of an extra digit, is one of the most common congenital anomalies of the hand, with an incidence of approximately 1 in 1,000 births. Polydactyly can occur on either the radial side of the hand (preaxial) involving duplication of thumb, central polydactyly involving any of the central three rays, or polydactyly involving the ulnar side of the hand (postaxial polydactyly).

Preaxial polydactyly, or duplication of the thumb, is classified according to the Wassel classification system.18 In this system, the number of the duplication corresponds to the axial level of the duplication. A Wassel type I duplication involves the distal phalanx (Figure 89.5); a Wassel type II classification involves the interphalangeal joint and distal phalanx; a Wassel type III involves the proximal and distal phalanges; a Wassel type IV involves duplication at the metacarpophalangeal (MCP) joint level and the proximal and distal phalanges, a type V involves duplication at the metacarpal level and the proximal and distal phalanges; and a type VI thumb has two separate metacarpals with articulating phalanges—Wassel even numbers involve duplication at the joints and odd numbers involve duplications at a level of conjoined bone, physis, or epiphysis. Most thumb duplications are symmetrical, and in these cases, the surgeon will generally try and preserve the ulnar thumb, thereby preserving stable ulnar collateral ligaments for pinch against the index finger. This decision regarding which digit to preserve must also consider the integrity of the flexor and extensor systems, as this may alter the decision. Surgery may also involve tendon and musculotendinous realignment. In most cases of surgical correction, the radial collateral ligaments are maintained on a proximally based flap of periosteum and secured to the radial aspect of the retained ulnar distal segment. In duplications at the Wassel type IV level and higher, the thenar musculature is advanced and attached to the radial side of the proximal phalanx as well. In some cases of duplication at the Wassel IV level, there may be a pollex abductus deformity present, with fusion of the extensor and flexor tendons on the radial side of the retained ulnar thumb, necessitating release and realignment of these tendons for optimal function. The surgeon must be aware of this possibility and carefully inspect the anatomy of the flexor and extensor tendons prior to deletion of a digit. As noted previously, it is essential to establish the integrity of the flexor and extensor systems prior to deciding which digit to ablate.

FIGURE 89.5. Wassel classification system of thumb duplication.

Central polydactylies are much less common than the preaxial or postaxial irregularities and are most often complex. The involvement may occur at the phalangeal or metacarpal levels. Deletion of the duplication frequently requires accurate delineation of joint function, extensor tendons, flexor tendons, and both intrinsic muscles and tendons to define which digit should be preserved. In all of these cases, surgical treatment must be carefully planned and executed to maximize function.

Postaxial polydactyly shows marked racial variation. In African-Americans, it is common, and often transmitted as an autosomal dominant trait. In contrast, in Caucasians, it is much less frequent, and formal genetics consultation should be strongly considered. Postaxial polydactyly is classified into two main groups: type A, with a broad stalk of attachment and a tendency toward associated anomalies; and type B, with a thin, narrow stalk. Type A abnormalities are more frequently associated with other congenital anomalies, including Laurence-Moon-Biedl syndrome, and appropriate diagnostic screening should be considered. Type B polydactyly is less frequently associated with these anomalies. Some have advocated simple ligation of type B deformities, but this inevitably leads to the presence of a “nubbin” that remains over the ulnar aspect of the fifth digit. An additional concern is that it is commonplace to pull up on the digital remnant while attempting to “sink” the ligature as close to the finger as possible to minimize the prominence of the “nubbin.” This can ensnare the proper digital nerve to the retained digit into the ligature, thereby creating a neuroma and sensory loss distally on the ulnar aspect of the fifth finger. A more prudent approach is to simply excise the extra digit under local anesthetic in the nursery through an elliptical incision under loupe magnification with the aid of an assistant. The neurovascular bundle can readily be isolated and ligated directly. Type A irregularities can often be handled in similar direct fashion, but will frequently require a limited setup in the operating room with tourniquet and anesthesia support.

CAMPTODACTYLY

Camptodactyly describes digits that show deviation of the digit in the palmar–dorsal plane of the hand, most often manifest as a flexion deformity. This non-traumatic disorder frequently affects the ring and little fingers, and typical findings are flexion at the PIP joint and hyperextension at the MCP joint.19 Most cases arise during the first year of life, but there is a smaller group of patients made up of predominantly females in whom camptodactyly may present during adolescence.20 Approximately two-thirds of the cases occur bilaterally.21 The disorder is asymptomatic and painless. Most mild cases are ignored by the parents and child, and so an exact incidence is difficult to determine because of underreporting. Some cases can progress to a moderate to severe flexion deformity of the PIP joint.

Camptodactyly refers to the posture or position of the finger and does not imply a diagnosis or pathogenesis. Although many cases occur sporadically, the disorder can be transmitted in an autosomal dominant fashion and can also be a manifestation of other syndromes, such as trisomy 13, oculodentodigital syndrome, orofacialdigital syndrome, Aarskog’s syndrome, and cerebrohepatorenal syndrome.19 The etiology of this deformity has been attributed to anomalous joint architecture, laxity of the extensor mechanism at the PIP level, anomalous fascial bands from the A1 pulley, abnormal flexor tendons, abnormal lumbrical muscles, and/or anomalous intrinsic muscles. As Smith and Kaplan have pointed out, “Virtually every structure at the base of the finger has been implicated as a deforming factor.”22 The most common identified anomalies include an anomalous lumbrical muscle or an absence or anomaly of the flexor digitorum superficialis (FDS) tendon. McFarlane et al.23 and Kay24 reported anomalies of the lumbrical muscles in 100% of their cases.

Treatment for camptodactyly includes nonoperative management in the majority of cases. Nonoperative management includes home stretching exercises and splinting. Stretching the PIP joint should be performed two to three times per day, taking care to deliver dorsally directed force to the middle phalanx and not the distal phalanx. Otherwise, DIP hyperextension deformity may result. Stretching exercises are supplemented with splinting. Splinting should consist of a forearm-based splint worn a minimum of 8 hours per night, and extending up to 23 hours per day. If the deformity persists after 6 to 12 months of stretching and splinting, consideration is given to operative management in moderate to severely afflicted individuals (>30° PIP flexion deformity).

Operative exploration should focus upon the lumbrical and FDS musculotendinous systems. Stabilization of the MCP joint to prevent hyperextension can be obtained through any of the classic procedures, including the Zancolli lasso procedure, volar plate tightening procedures, and/or tendon transfer. FDS tendon can undergo tenolysis, Z-lengthening, or even release. With such a wide distribution of potential etiologies, it is not surprising that the outcomes vary widely. Engber and Flatt20 reported that 80% of their cases showed a progression of the deformity, and only 20% of cases showed improvement with nonoperative therapy, and only one-third of those who underwent surgery showed improvement. Siegert et al.25 reported that only 18% of their patients with mild to moderate deformities (contracture less than 60°) showed improvement with surgery, whereas two-thirds improved with nonoperative treatment. In general, many surgeons would not recommend operative treatment if the contracture is less than 30°, and if more severe would consider operative management only in selective cases in which nonoperative management has failed.24

CLINODACTYLY

Clinodactyly describes digits that show congenital deviation within the radial–ulnar plane of the hand. Most frequently, the small finger is deviated in a radial direction at the level of the middle phalanx. Clinodactyly can occur sporadically, be inherited in an autosomal dominant trait with variable penetrance, or be associated with several syndromes, including chromosomal abnormalities.26 When inherited as an autosomal dominant trait, the disorder is frequently present bilaterally. Clinodactyly is often caused by a trapezoidal- or triangular-shaped bone of the phalanges, most commonly the middle phalanx, but all bones and all rays of the hand can be involved, including the thumb. This trapezoidal bone, often termed a “delta phalanx,” creates a deviation of the interphalangeal joints from the normal parallel orientation of the joint surfaces, leading to deviation in the ulnar–radial plane. In some cases, the deviation is caused by a longitudinally bracketed epiphysis, wherein the physis, or growth plate, is irregularly shaped and spans the axial length of the phalanx. In these cases, growth will often lead to progressive deformity, and surgical correction is often necessary to prevent functional deficit.

Clinodactyly is frequently associated with little functional impairment. Mild deviation of the digit (<10° to 15°) may even be considered within the range of “normal.” In fact, clinodactyly frequently goes unnoticed by both the child and parents, particularly in inherited cases. When the deformity is more severe, it can cause functional impairment or significant aesthetic deformity. In these cases, repair by corrective osteotomy is considered. Corrective osteotomy should be undertaken at an age when the bone fragments are large enough to allow for accurate control, positioning, and stabilization. In many cases, the surgery must be deferred until the child is 10 to 12 years of age to allow for adequate technical control. In the case of a longitudinally bracketed epiphysis, the physis must be disrupted and tissue interposed to prevent healing. This can, and often should, be performed at an earlier age to prevent progressive deformity.

CONSTRAINED FIRST WEB SPACE

A soft and supple first web space is crucial to thumb positioning and function. Although the first web space is seldom involved in a true syndactyly (less than 5% of cases of syndactyly), the motion of the thumb can be constrained as a result of a narrowed first web space. In these cases, the narrowed distance between the thumb and the index finger can limit thumb motion, and effectively decreases the “span” of the hand. The effectiveness in grasping larger objects is limited. In the normal hand, the thumb contributes approximately 40% of total hand function (AMA guide to permanent impairment), based upon MCP level amputation.27 In hands with limitations from other associated congenital anomalies, the thumb’s degree of contribution to hand function may be even greater. The normal range of motion for an adult thumb is 50° of radial abduction, 8 cm of opposition (measured from palmar base of long finger to palmar tip of thumb in direct opposition), and 8 cm of adduction (measured from thumb tip to MCP joint of small finger).27 Adduction contracture is considered significant if the intermetacarpal angle is less than 40°.27

Release of the first web space is determined by the severity of the constraint. In many cases, the deficiency only involves skin and subcutaneous tissues. A number of techniques have been described for this situation. All make use of local or remote flaps, as opposed to skin grafts, to allow for supple resurfacing of the first web space, and to create a natural U-shaped web (rather than a steep V-shaped web). For this reason, double z-plasties are preferred to one large z-plasty. Three primary techniques include the four-flap z-plasty, the double z-plasty, and the double-opposing z-plasty (Figure 89.6). These are reliable techniques, and the procedure chosen depends largely on the surgeon’s preference. In larger expansions of the web, alternative reconstructions may be necessary, such as a dorsal hand rotation flap. It is critical that the degree of release obtained of the web space not be compromised by an inadequate surface area of skin or a tight closure.

In some cases, additional deeper structures may require release. Following design and elevation of the skin flaps, the degree of motion is assessed. If the web space remains constrained, then release of the myofascia investing the adductor pollicis muscle and the first dorsal interosseous muscle is performed. If adequate gain is still not obtained, then further release such as a partial release of the origin of the first dorsal interosseous muscle from the first metacarpal shaft is executed. Great care must be taken to avoid injury to the digital neurovascular bundles and to the adductor pollicis muscle, since this is crucial for grasp. Following release and first web space resurfacing, it is sometimes beneficial to cross pin the first and second metacarpal shafts to maintain the gain in width during the period of healing.

FIGURE 89.6. Constrained first web space treated with (A) double z-plasty or (B) double-opposing z-plasty.

RADIAL COLUMN (PREAXIAL) ABNORMALITIES

Abnormalities of the preaxial (radial) side of the hand vary from a relatively normal delay in maturation of the neuromuscular units to agenesis of the radius and thumb. The thumb is so crucial to hand function (40% of total hand function, as noted previously18) that a basic understanding of these irregularities is essential.

One spectrum of these anomalies occurs when the thumb is held in a flexed position. This may occur as a result of a delay in maturation of the radial neuromuscular units, a “trigger” thumb, or a “clasped” thumb. These can sometimes be difficult to differentiate. In many children, the long extensors of the thumb undergo a delay in maturation, and there is weakness or absence of thumb extension resulting in adduction and flexion of the thumb. The flexion is usually at the MCP joint. Splinting the thumb into abduction may prevent secondary changes while maturation occurs, and the thumb extends normally. A forearm-based splint is used on a 23-hour a day basis until maturation occurs. These children require close follow-up, however, since these findings may indicate a congenital clasped thumb that will require surgical intervention.

In “trigger” thumb, the thumb is typically held in the flexed position at the interphalangeal joint and the patient cannot straighten it. Once the thumb is flexed, the child generally holds it in this position, presumably because the sensation created by the thumb triggering is uncomfortable. Less commonly, the thumb is held in extension, with an inability to flex at the interphalangeal joint, despite the presence of flexion creases on the palmar surface of the thumb. In both of these cases, the nodule in the flexor tendon is usually palpable over the palmar surface of the thumb. Treatment is guided by the fact that this disorder will frequently resolve spontaneously.28,29 Consideration for surgery is usually deferred until the child is 9 to 12 months of age to allow for spontaneous resolution. Splinting has been shown to be of inconsistent benefit. If the trigger thumb persists, then surgery is performed carefully through a transverse incision at the level of the proximal flexion crease of the thumb. Surgery must carefully avoid the neurovascular bundles, which are located more centrally on the palmar surface of the thumb than in the fingers. Following identification of these nerves, the A1 pulley is carefully released along the radial aspect. Full excursion of the thumb without restriction should be demonstrated prior to wound closure.

If the thumb is held in a flexed position at the MCP joint, then this indicates a much more complex problem known as clasped thumb. Congenital clasped thumb can be divided into two subtypes: supple and complex.30 The supple subtype has only a deficiency of the extensor mechanism, whereas the complex type will also have a variable degree of MCP tightness, with a severe amount of skin deficiency, collateral ligament abnormality, thenar muscular hypoplasia, and tightness of the flexor pollicis longus musculotendinous unit. The “complex” type of clasped thumb is frequently seen in association with other abnormalities, including Freeman-Sheldon syndrome (also known as whistling face deformity or craniocarpaltarsal dysplasia) and is frequently present bilaterally. Initial management of clasped thumb consists of a forearm-based splint for the thumb and splinting the wrist in a neutral position.

RADIAL CLUB HAND/THUMB HYPOPLASIA

Longitudinal radial deficiency, or radial club hand, is caused by undergrowth or absence of the radius and has an incidence of between 1 in 30,000 and 1 in 100,000 births.31 The disorder is believed to be caused by an insult to the apical ectodermal ridge during the fourth to seventh weeks of intrauterine development.32 Thumb absence or hypoplasia is almost always present to some extent, the radius is hypoplastic or absent, and the radial artery is usually absent. The scaphoid and trapezium are also frequently absent from the carpus, and the muscles on the radial side are frequently absent or hypoplastic (extensor carpi radialis longus, extensor carpi radialis brevis, flexor carpi radialis, brachioradialis, and thenar muscles). The disorder is associated with other disorders, including Fanconi’s anemia, thrombocytopenia absent radius syndrome, VATER syndrome (vertebral, anal atresia/imperforate anus, tracheoesophageal fistula, esophageal atresia, and renal defects), or Holt-Oram syndrome (associated cardiac anomalies). All radial deficiency patients are investigated for the presence of these disorders. Initial management for radial club hand is provided by the range of motion exercises to the wrist and stretching the wrist over the distal ulna, accompanied by serial splinting. In severe cases, application of an external distractor may be necessary. Once the wrist is supple and aligned over the distal ulna, the wrist is “centralized” over the distal ulna by resection of the fibrous anlage of the radius and rebalancing of the musculotendinous structures at the wrist level.12,33

Thumb hypoplasia is almost always present to some degree in radial club hand/longitudinal ray deficiency, but thumb hypoplasia may exist without an anomalous radius. The hypoplastic thumb is categorized by the Blauth classification system34 which characterizes the size of the thumb, the thenar musculature, web space, and joint stability at the carpometacarpal joint. This characterization is important in defining treatment options. In general, in children with instability of the carpometacarpal joint (Blauth IIIB) or a higher degree of thumb aplasia,35 most surgeons would recommend deletion of the hypoplastic thumb and pollicization, that is, transfer of the index finger into position to function as a thumb. During this surgery, the index metacarpal is truncated and the index finger is rotated into a position of opposition, with tendon transfers to the extensor mechanism to assist in thumb adduction, abduction, and extension. It is important to note that the new thumb will not have all of the characteristics of a “thumb,” but should allow for opposition and grasp, functions not possible when all digits are coplanar.

CONSTRICTION RING SYNDROME

Constriction ring syndrome, also known as amniotic band syndrome, is a well-known disorder that affects the extremities far more frequently than it affects the face. The disorder is sporadic and is not inherited, and the results can vary from minor to severe, with an overall incidence of 1 in 15,000 births.36 The cause of the disorder has been extensively debated, with some experts believing that the disorder is caused by an “intrinsic defect” of the mesodermal tissue leading to the characteristic rings in the extremities, whereas most now believe that this is caused by an “external force.” This external force is most widely believed to be a filament, or “amniotic band,” that encircles and compresses areas of the fetus and leads to the characteristic abnormalities that are present at birth. This etiology is supported by the straight line that exists across adjacent digits, the finding of a filamentous structure wrapped around many afflicted extremities that is “unwound” following birth, and the occurrence of acrosyndactyly—where digits that were separated at one point during development undergo apparent refusion at the site of the band, with the presence of an epidermal-lined sinus tract proximal to the site of fusion.36 Constriction rings can extend down through the skin and subcutaneous tissues to the bone and can lead to ischemia (Figure 89.7), neural deficit, or amputation. In those cases of threatened limb or digital loss, decompression of the site is a surgical emergency. Most surgeons prefer to release the areas using a z-plasty–based technique and prefer to decompress only one-half the circumference of the afflicted limb at one stage. Buck-Gramcko12,36 reported no complications using a single-stage release, but most surgeons prefer the two-stage approach.

CONGENITAL TUMOROUS CONDITIONS

The tumors present in congenital hand deformities are distinctly different from their adult counterparts. Overall, the vast majority of these tumors are benign. Hemangiomas and vascular malformations account for over 50% of all such cases.37 Lymphangiomas also occur with isolated upper extremity involvement. In addition, disorders of connective tissue specific to this age group can occur—juvenile aggressive fibromatosis and infantile digital fibromatosis, both of which can be problematic to treat and are prone to recurrence. Cartilagenous tumors such as enchondromas can exist in isolation or as multiple enchondromas as a part of the uncommon OIlier’s disorder or the rare Mafucci’s syndrome. Neurofibromas can also occur in the upper extremity and require evaluation to exclude the occurrence of neurofibromatosis-1 (Nf-1) (Chapter 28) and may merit excision depending upon the child’s symptoms.

Vascular

Vascular lesions of the upper extremity include both hemangiomas and vascular malformations (Chapter 21). Vascular tumors are the most common tumors of infancy, and they are overwhelmingly benign.38,39 Malignant vascular tumors account for less than 2% of reported series.38,39 Mulliken and Young40,41 described a classification system, and Upton extended this classification system to the upper extremity and has provided significant insight into the management of these lesions in the upper extremity. Hemangiomas may be present at birth, or arise shortly after birth, and undergo a characteristic rapid proliferative growth phase during the first 6 months of life. They occur predominantly in females. Hemangiomas account for more than one-half of the vascular anomalies of the upper extremity, and they behave as they do elsewhere in the body.37,39,42 During the rapid growth phase, up to 30% of the lesions will ulcerate and bleed.37,39 Hemangiomas reach a plateau phase after 6 to 12 months of growth, and then undergo involution. Fifty percent of hemangiomas involute by 5 years of age and 90% by 9 years of age (Bower’s criteria43). If the lesions become symptomatic or ulcerate, treatment with steroids may be useful (oral prednisone 2 to 4 mg/kg/d for 4 to 6 weeks or direct intralesional injection of triamcinolone). Hemangiomas may, in some cases, require resection. After involution, it may be necessary to remove the residual adipose tissue and “crepe paper” skin. Vascular malformations are always present at birth and show no sexual predilection. Vascular malformations are further characterized as capillary malformations, venous malformations, lymphatic malformations, lymphatico-venous malformations, and arteriovenous malformations.40 Diagnosis is usually made by careful physical examination. In general, diagnostic imaging is not routine and should be reserved for more complex lesions when a therapeutic intervention is planned. Capillary malformations, or port-wine stains, are often successfully treated with laser. In some cases, deeper structures are involved and hypertrophy of the skeleton and soft tissues is present. Venous malformations are the most common type of vascular malformation and are characterized by diffuse involvement, but tend to follow defined anatomic tissue planes. Venous malformations can be associated with overgrowth and with other syndromes (Klippel-Trenaunay or Parkes Weber). Magnetic resonance imaging scans provide excellent anatomic detail when necessary. Treatment can be provided with compression garments, direct injection sclerotherapy, or if the patient is symptomatic due to a mass effect, surgical resection. If the decision is made for surgery, it is important to remove as much of the lesion as possible, since the first surgery usually provides the best anatomic detail evident, crucial in upper extremity surgery. Similarly, lymphatico-venous and lymphatic malformations are often treated with compression garments. Strict attention must be paid to the possibility of infection, because infection causes exacerbation of the swelling, and this may not be reversible. β-Hemolytic strep is the usual offending agent, and patient’s families are given a prescription for penicillin in case they suspect an infection. These lesions are also improved by excision, and similar to venous malformations, the initial surgery is the most favorable time to perform near-total or total excision, because of the clarity of the anatomy unaffected by the scar tissue. Arteriovenous malformations account for less than 5% of vascular anomalies that presented to a major referral center.37,39 However, they are characterized by fast-flow and represent difficult management problems. Upton has classified these lesions based upon the extent of their fistula formations: type A—single or multiple arteriovenous fistulas, aneurysms, or ectasias isolated to the arterial side of the circulation; type B—microfistulas or macrofistulas isolated to a single axial artery; and type C with diffuse arteriovenous malformations and multiple arteriovenous fistulas diffusely present in the upper extremity.37 Management is usually via embolization followed by surgery, but repeated attempts may be necessary, and the prognosis for type C lesions is limited, with over one-half requiring amputation.37

FIGURE 89.7. Constriction ring syndrome of premature child with ischemic thumb and ring finger (A) who underwent semi-circumferential operative release of both digits with z-plasties under operative microscope and demonstrated improved perfusion (B).

Connective Tissue

Infantile digital fibroma, or Reye’s tumor, may occur as a single nodule or as multiple lesions on the fingers and toes.44 The lesions characteristically arise as smooth dome-shaped nodules on the extensor surface of the fingers and toes, and 80% of the time arise during the first year of life.45 Conservative treatment is indicated, but if deformity or functional problems arise, then surgery is indicated. Surgery is the treatment of choice but recurrence rates as high as 60% have been noted, so the lesion is also known as recurrent digital fibroma.45 If the lesion recurs, wide excision should be performed in a non-mutilating fashion.

Juvenile aggressive fibromatosis, or desmoid tumor, arises from connective tissue or muscle. It can develop as early as 1 month of age, but the mean age of onset is the third decade. The lesion presents as a painless mass and approximately 5% of the lesions arise in the hand as slow-growing, painless lesions.46 This tumor is benign, but aggressive, with recurrence rates as high as 73%. Recurrence is low with negative margins, but as high as 90% with positive margins, and can recur within 3 months of excision.46

Neural Tissue

In children, neurofibromas may exist as isolated entities or as part of Nf-1 (Chapter 28). Nf-1 is relatively common, with over 100,000 cases in the United States alone, an incidence of 1 in 4,000, and is genetically transmitted as an autosomal dominant trait.47,48 Neurofibromas occur in five main types: localized cutaneous neurofibroma, diffuse cutaneous neurofibromas, localized intraneural neurofibroma, plexiform neurofibroma, or massive soft tissue neurofibroma.49 Localized neurofibromas are the most common type of neurofibroma, may be single or multiple, and are typically slow-growing lesions that increase in prominence over life. Diffuse cutaneous neurofibromas present as enlarged plaque-like thickenings of skin and subcutaneous tissue that are soft and compressible. Localized intraneural fibroma is the second most common type of neurofibroma overall, but the most common type in the upper extremity accounting for 85% of cases, and represents the fusiform enlargement of a peripheral nerve.50 Plexiform neurofibromas are virtually unique to Nf-1, occur as the growth of nerve sheath cells along the length of a nerve, and can be associated with both soft tissue hypertrophy and destruction or compression of adjacent tissue. Massive neurofibromas, previously known as elephantiasis neurofibromatosa, are rare in Nf-1 and rare in the upper extremity.

Despite a potentially higher occurrence of malignant degeneration over a lifetime than might have been previously appreciated,51,52 surgical management of neurofibromatosis in a child is almost always based upon balancing the benefits of tumor excision/debulking versus the potential loss of sensory or motor function. An additional major consideration in the child is the diagnosis of Nf-1, if present. This must be considered and evaluated based upon the implications this diagnosis has for autosomal dominant genetic transmission and the higher incidence of malignant degeneration in afflicted individuals.52 Despite localization of the Nf-1 gene to band 11.2 of the long arm of chromosome 17, the diagnosis of Nf-1 remains clinically based upon the six National Institutes of Health criteria (six or more café-au-lait spots, two or more neurofibromas, axillary or inguinal freckling, two or more Lisch nodules, optic glioma, a distinctive osseous lesion [e.g., sphenoid wing dysplasia], and/or a first-degree relative with Nf-1).47,48

Skeletal

Enchondromas are the most common skeletal tumor of the hand, and these tumors are benign (Chapter 86). They usually occur as single isolated lesions that are amenable to curettage and healing, with or without bone grafting. Rarely, they may be multiple and be associated with either Ollier’s disease, which is uncommon and in which the lesions will continue to grow until maturity, or Mafucci’s syndrome, which is rare and in which the patients also have multiple hemangiomas.53,54 The potential for malignant degeneration is present in both these disorders (approximately one-third) and is frequently associated with the onset of pain. Both groups of patients must be followed clinically and radiographically.53,54

SUMMARY

Congenital hand surgery is one of the most challenging aspects of surgery. The hand surgeon is routinely confronted with significantly aberrant anatomy, frequently limited by the ability of the patient to comply with treatment regimens, and also the potential for anesthetic and operative risks. However, the ability to provide function where function is limited or nonexistent, and to be able to provide this for an individual over his entire lifetime, is some of the most gratifying of all surgeries. The “impact factor” of successful management yields a lifetime of rewards for the afflicted child.

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