Syndactyly Treatment & Management


Practice Essentials

Syndactyly is the most common congenital malformation of the limbs, with an incidence of 1 in 2000-3000 live births. [123 It is a failure of differentiation in which the fingers fail to separate into individual appendages. This separation usually occurs during the sixth and eighth weeks of embryologic development. The term syndactyly is derived from the Greek prefix syn- ("with, together") and the Greek noun daktylos ("finger, digit").

Syndactyly can be an isolated finding, or it can be found in association with other abnormalities (eg, polydactyly, cleft hands, ring constrictions, and craniofacial syndromes). [4 It is a shared feature of more than 28 syndromes, including PolandApert, and Holt-Oram syndromes.

Classification is based on the severity of the clinical presentation (see Classification). Syndactyly can be classified as simple when it involves soft tissues only and as complex when it involves the bone or nail of adjacent fingers. 

Unreleased syndactyly can significantly impair finger and hand function. The impairment is worse when the syndactyly is complete, is complex, or involves the border digits with fingers of uneven lengths, such as the ring and small fingers or the thumb and index finger (see the images below).

Complete simple syndactyly of ring and small fingeComplete simple syndactyly of ring and small fingers. Note ring finger proximal interphalangeal (PIP) joint flexion deformity due to complete syndactyly between border digits.
Complete simple ring and small finger syndactyly. Complete simple ring and small finger syndactyly. Note ulnar deviation of ring finger due to syndactyly of small finger.

In itself, a minor incomplete syndactyly is not an indication for surgery if the only issue is its incongruous appearance. However, a syndactyly that prevents full range of motion in the involved fingers warrants surgical release to increase functionality of the fingers. Most patients with syndactyly benefit from surgical release. The timing of surgery is variable; however, if more fingers are involved and the syndactyly is more complex, release should be performed earlier. 

Etiology

Several genetic abnormalities have been associated with syndactyly. [567 Approximately 10-40% of cases are familial with variable penetrance. Syndactyly may occur as part of a syndrome or as sporadic events that are nonhereditary and nonsyndromic. One report indicated that there is an association between syndactyly and smoking during pregnancy. [8]

Epidemiology

Syndactyly is the most common congenital abnormality of the hand, with a rate of 1 per 2000-3000 births. [9101112The male-to-female ratio is 2:1.

Prognosis

Despite appearing relatively straightforward, syndactyly release is a complex operation requiring well-honed skills. If the procedure is properly performed, the rate of complications is low, and the results are extremely gratifying for the parents and beneficial to the patients in improving hand functionality and in providing normal-appearing hands and fingers.



History and Physical Examination

Although many patients with syndactyly have been evaluated by multiple specialists and referred by their primary care pediatrician, the hand surgeon should also obtain a thorough antenatal, postnatal, and familial history. In addition to the hand being examined, the cranium, face, torso, and lower extremities should be examined for anomalies.

The hand evaluation should proceed systematically, as follows:

  • Note and document the number of digits present, the level of web involvement, the length of the finger, and the appearance of the fingernails
  • Often, photographing or drawing a picture of the hands during the initial visit is helpful
  • Passively move the fingers to determine bony union; differential motion occurs only if no underlying bony union is present; fusions of the fingernails often are associated with bony union, and a broad fingernail also may indicate a hidden polydactyly
  • The extent of anomaly of tendons and neurovascular structures reflects the complexity of the syndactyly; in a simple complete or a complex syndactyly involving only the distal phalanx, the underlying tendon and neurovascular structures are usually normal, but in an individual with brachysyndactyly or complicated syndactyly, the bifurcation of the nerves and digital vessels may be located more distally, or only one side may be present
  • Always obtain radiographs to help identify any other anomalies (eg, bony synostosis, delta phalanx, or symphalangism)

Classification

Classification of syndactyly is based on the severity of the clinical presentation.

The mildest form is simple syndactyly, which refers to fingers joined only by soft tissue. In simple syndactyly, the third web space between the long finger and the ring finger is the area most commonly involved, followed by the fourth, second, and (rarely) first web spaces. Bilateral involvement is found in 50% of patients.

When the soft-tissue union is only partial and does not extend to the fingertips (see the first and second images below), the condition is referred to as incomplete simple syndactyly. When the soft-tissue union extends to the fingertip, the condition is referred to as complete simple syndactyly (see the third and fourth images below).

Dorsal view of hand demonstrating simple incompletDorsal view of hand demonstrating simple incomplete syndactyly between left long finger and ring finger. Note incidental café-au-lait spot.
Palmar view of hand with syndactyly. Level of syndPalmar view of hand with syndactyly. Level of syndactyly, just proximal to proximal interphalangeal (PIP) joint, can be clearly seen on this view.
Dorsal view of hand of 1-year-old child with complDorsal view of hand of 1-year-old child with complete simple syndactyly. Note that both long finger and ring finger have distinct nail plates with trough separating them.
Palmar view of hand of 1-year-old child with complPalmar view of hand of 1-year-old child with complete simple syndactyly.

Complex syndactyly refers to fingers joined by bone or cartilaginous union, usually in a side-to-side fashion at the distal phalanges.

The most severe form is classified as complicated syndactyly, which refers to fingers joined by bony fusion in other than a side-to-side fashion. It can include bony abnormalities, such as extra, missing, or duplicated phalanges and abnormally shaped bones (eg, delta phalanges). (See the image below.) Abnormalities in the musculotendinous and neurovascular structures may also be present.

Radiograph of left hand of patient with type III ARadiograph of left hand of patient with type III Apert syndrome. Note complicated syndactyly with osseous union in distal phalanges of all fingers. Symphalangism is present between proximal and middle phalanges, without formation of proximal interphalangeal (PIP) joint in ring, long, and index fingers.

Associated Syndromes

Syndactyly can be an isolated finding, or it can be found in association with other abnormalities, such as polydactyly, cleft hands, ring constrictions, or craniofacial syndromes. [4]

Apert syndrome is the best known of the craniofacial syndromes. Another syndrome that may develop is Poland syndrome, in which the pectoralis muscle abnormality is found in association with symbrachydactyly or other anomalies of the ipsilateral upper extremity. [13 Constriction band syndrome can be associated with syndactyly, but the etiology of the syndactyly is different.

Apert syndrome

Apert syndrome, or acrocephalosyndactyly, is a rare anomaly, occurring in 1 per 160,000-200,000 live births. [141516 Besides the characteristic facial anomalies of Apert syndrome, it is also defined by the associated upper- and lower-limb anomalies. The anomalies in the hands are mirror images of each other and are characterized by the following four common features:

  • Radial deviation of a short thumb as a result of an abnormally shaped proximal phalanx (ie, delta phalanx)
  • Complex syndactyly of the index, long, and ring fingers
  • Symbrachyphalangism of the central segments of the index, long, ring, and small fingers
  • Simple syndactyly of the web space between the ring and small fingers

The web space between the thumb and the index finger is variable, and the extent of syndactyly at this web space serves as the basis for the classification of Apert syndactyly into three types, as follows.

Type I is the most common and the least severe of the three types. The thumb is foreshortened and associated with a radial clinodactyly as a result of a delta phalanx of the proximal phalanx. Although it is separate from the index finger, the first web space is shallow.

A complex syndactyly includes the index, long, and ring fingers because of osseous or cartilaginous union of the distal phalanges. Simple syndactyly of the small and ring fingers is present; this syndactyly may be complete or incomplete. The distal interphalangeal (DIP) joint of the small finger is well formed and functional. Type I hands are often referred to as spade hands. (See the images below.)

Dorsal view of hand of 6-month-old patient with tyDorsal view of hand of 6-month-old patient with type I Apert syndrome. Note that thumb is separate.
Radial view of hand of 6-month-old patient with tyRadial view of hand of 6-month-old patient with type I Apert syndrome. Index fingernail is separate, and syndactyly is complete. Small fingernail is also separate from rest of hand. Simple syndactyly between small finger and rest of hand is present. Note that broad thumb and abnormal curvature of thumb is due to presence of delta phalanx, seen in following radiograph.
Radiograph of hand of 6-month-old patient with typRadiograph of hand of 6-month-old patient with type I Apert syndrome demonstrates distinctive characteristics of this syndrome. In small finger, distal interphalangeal (DIP) joint is formed. Although rudimentary proximal interphalangeal (PIP) joint is present, clinically this joint is stiff. In ring, long, and index fingers, no PIP joint is present, and symphalangism is present between middle and proximal phalanges. Distal phalanges of ring and long fingers are fused. In thumb, proximal phalanx is shaped abnormally and is referred to as delta phalanx. Synostosis of ring and small finger metacarpals is present.

Type II is more severe and is characterized by a simple incomplete or complete syndactyly of the thumb with the index ray, without any osseous union. The thumbnail matrix remains separate from the index fingernail. The hand has a large, concave palm. The bony union of the distal phalanges of the index, long, and ring fingers are more extensive than in type I. The ring finger–small finger syndactyly remains simple but complete. Type II hands have been referred to as mitten hands or spoon hands (see the image below).

Apert type II hand. Note complete syndactyly betweApert type II hand. Note complete syndactyly between ring and the small fingers. Patient's hand was complicated by chronic paronychia and skin maceration preoperatively.

Type III is the most severe and, fortunately, least common form. A tight osseous or cartilaginous union is present between all five fingers. All five nailplates are conjoined, and they sometimes have longitudinal ridges, which indicate separate underlying distal phalanges. The thumb is indistinguishable from the index ray. The small finger, although joined by a common fingernail, does not have an osseous union at the distal phalanx and remains a simple but complete syndactyly. Usually, metacarpal synostosis of the small and ring finger rays is present.

Type III hands have been termed rosebud or hoof hands (see the first and second images below). Radiographs are difficult to obtain and interpret because of the overlap of osseous structures (see the third image below). [15]

Apert syndrome (type III), dorsal view. Apert syndrome (type III), dorsal view.
Apert syndrome (type III), volar view. Apert syndrome (type III), volar view.
Radiograph of left hand of patient with type III ARadiograph of left hand of patient with type III Apert syndrome. Note complicated syndactyly with osseous union in distal phalanges of all fingers. Symphalangism is present between proximal and middle phalanges, without formation of proximal interphalangeal (PIP) joint in ring, long, and index fingers.

As stated, the goal of treating complex syndactyly is the surgical release of the fingers to increase the functionality of the hand. The timing of surgery is critical because the child requires multiple operations for other abnormalities of the cranium, midface, and orbits associated with Apert syndrome.

Poland syndrome

Poland syndrome is a sporadic congenital anomaly characterized by the absence of the sternal head of the pectoralis major muscle, along with hypoplasia or aplasia of the breast or nipple, with deficiency of the subcutaneous fat and axillary hair. There can be associated abnormalities of the rib cage and the ipsilateral upper extremity. It was first described by Alfred Poland in 1841 as a medical student, when he reported the absence of the sternocostal portion of the pectoralis major during a cadaver dissection.

In the hand and fingers, anomalies include symphalangism, syndactyly with hypoplasia, brachydactyly, or aplasia of the fingers. Two variations of hand anomalies with syndactyly in patients with Poland syndrome can be seen in the images below.

Poland syndrome. Dorsal view of left hand in patiePoland syndrome. Dorsal view of left hand in patient with Poland Syndrome with brachydactyly (short fingers) and adactyly (missing fingers) with associated simple incomplete syndactyly between ring and small fingers.
Volar view of preceding hand in patient affected wVolar view of preceding hand in patient affected with Poland syndrome.
Right hand of patient with Poland syndrome. Note iRight hand of patient with Poland syndrome. Note incomplete syndactyly between hypoplastic right index and long fingers.
Volar view of index and long fingers in incompleteVolar view of index and long fingers in incomplete syndactyly in patient with Poland syndrome.

Constriction band syndrome

The syndactyly found in constriction band syndrome (also known as amniotic band syndrome) is not the result of failure of differentiation during embryogenesis. In this condition, the fingers are already formed, and because of the injuries due to the constricting amniotic bands, the fingers heal together at the site of injury, causing postinjury syndactyly. [17 The extent of involvement may be mild, with only a rudimentary small skin bridge connecting the two fingers (see the images below).

Dorsal view of right hand of a 1.5-year-old patienDorsal view of right hand of a 1.5-year-old patient with constriction band syndrome. Fingers can still be identified individually. Note presence of fistula tract between affected fingers, particularly between long finger and ring finger.
Palmar view of right hand of a 1.5-year-old patienPalmar view of right hand of a 1.5-year-old patient with constriction band syndrome. Fingers can still be identified individually. Note presence of fistula tract between affected fingers, particularly between long finger and ring finger.
Right hand of 1.5-year-old patient with constrictiRight hand of 1.5-year-old patient with constriction band syndrome. Radiograph demonstrates that level of amputation was at proximal interphalangeal (PIP) joints.

The extent of involvement may be more severe, with a complete soft-tissue fusion in association with amputated fingers (see the images below).

Dorsal view of left hand of 1.5-year-old patient wDorsal view of left hand of 1.5-year-old patient with constriction band syndrome. Left hand is more severely involved than right, with all fingers being nearly indistinguishable from one another. Note presence of pits between fingers where normal webs would be. Most prominent one is between ring and small fingers. They often represent fistulas between dorsal and volar surfaces of hand and are often all that remains of previous normal web space.
Volar view of left hand of 1.5-year-old patient wiVolar view of left hand of 1.5-year-old patient with constriction band syndrome. Left hand is more severely involved than right, with all fingers being nearly indistinguishable from one another. Note presence of prominent fistula between small finger and ring finger.
Radiograph of left hand of 1.5-year-old patient wiRadiograph of left hand of 1.5-year-old patient with constriction band syndrome. Level of amputation is through midportion of proximal phalanges of involved fingers.

Occasionally, epithelialized sinuses or fistula tracts can be found usually proximal to the level of the syndactyly (see the images below). The finger distal to the constriction ring is usually atrophic, or it has been amputated in utero as a result of ischemia. These findings in the fingers may be isolated or associated with other constrictions on the proximal arm, leg, or face.

Dorsal view of right hand of a 1.5-year-old patienDorsal view of right hand of a 1.5-year-old patient with constriction band syndrome. Fingers can still be identified individually. Note presence of fistula tract between affected fingers, particularly between long finger and ring finger.
Palmar view of right hand of a 1.5-year-old patienPalmar view of right hand of a 1.5-year-old patient with constriction band syndrome. Fingers can still be identified individually. Note presence of fistula tract between affected fingers, particularly between long finger and ring finger.
Right hand of 1.5-year-old patient with constrictiRight hand of 1.5-year-old patient with constriction band syndrome. Radiograph demonstrates that level of amputation was at proximal interphalangeal (PIP) joints.

If the syndactyly is minimal, standard techniques and skin grafts may be used to release the syndactyly (see the image below).

Left hand of 1.5-year-old patient with constrictioLeft hand of 1.5-year-old patient with constriction band syndrome after second reconstructive procedure following release of second and fourth web spaces. Syndactyly partially recurred because of skin-graft loss. During second-stage operation to separate long finger and ring finger, recurrences in second and fourth web spaces were re-revised. Thus, sutures are present on both sides of ring finger and long finger.

If sinus tracts or fistulas exist within the syndactyly, these tracts can often be released to reveal epithelialized web spaces, which do not require skin grafts (see the image below). The markings made prior to the syndactyly then require modification.

Palmar view of right hand of 1.5-year-old patient Palmar view of right hand of 1.5-year-old patient with constriction band syndrome after previously staged syndactyly release. No skin graft was needed for release between long and ring fingers. Patient also underwent revision of web space between index and long fingers.

Imaging Studies

Obtain radiographs of the hands to evaluate for any other bony anomalies, such as synostosis, delta phalanx, or symphalangism.

Procedures

If the infant has no associated medical conditions, a formal preoperative evaluation by the anesthesia team usually is not necessary. However, should there be any congenital syndromes or associated medical conditions, patients should be scheduled for operative clearance with the preoperative evaluation service of the hospital where the surgery will be done. Generally, if there is no issue with postoperative monitoring, many of these cases can be handled as outpatient procedures.

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