Systematic evaluation of the affected hand is important for assessing syndactyly. Evaluation is based on both history and physical examination. In most of the cases there will be a clear family history of syndactyly. Family history gives important information on the experience and may help in deciding the treatment plan. Syndactyly occurs in five different phenotypic forms.

• Type I syndactyly is characterized by complete or partial fusion. For example, cutaneous fusion between 3rd and 4th fingers. In some cases bone fusion may be noted at the level of distal phalanges. 
• Type II syndactyly is manifested by polysyndactyly of 3rd and 4th fingers with duplication of finger 3 or 4 in the web. Feet may also show syndactyly in the 4th and 5th toes. Fifth toe may show duplication in the web. Variability may be shown in clinical manifestations in the same family. 
• Type III syndactyly is characterized by complete and bilateral soft tissue syndactyly between 4th and 5th fingers. Osseous fusion of the distal phalanges may be noted in some patients. Middle phalanx of the 5th digit may be short or rudimentary. It is usually associated with spastic paraplegia in the same family. 
• Type IV syndactyly is manifested by complete cutaneous syndactyly of all fingers in both hands. Usually associated with pre- or post-axial hexadactyly. The extra digit is often fully developed with metacarpal duplication. When flexed the palm may have a peculiar cup-shaped form. It is usually not associated with bone fusion. 
• Type V syndactyly is rare when compared to other forms of syndactyly. It is a soft tissue syndactyly seen with metacarpal and metatarsal synostosis. Fusion is usually seen in 3rd and 4th fingers, but may be more extensive. 

Complexity of syndactyly can be assessed on the basis of extent of anomaly of tendons and neurovascular structures.

• Surgical Procedure

  The Center for Plastic and Reconstructive Surgery offers a full range of surgical procedures for syndactyly. Surgeons use leading-edge technology and world-class surgical techniques. [cedars-sinai.org]

  The goal of syndactyly release is to create a functional hand with the fewest surgical procedures while minimizing complications. [mayoclinic.pure.elsevier.com]

  The technique is rapid, safe, easily performed, and reproducible and requires a single surgical procedure. [ncbi.nlm.nih.gov]

  For this reason, patients with multiple fingers involved will often require more than one surgical procedure. In rare instances involving minimal functional or cosmetic problems, surgery may not be required. [cedars-sinai.edu]

  The exact surgical procedure to correct webbed toes depends on the severity of the webbing and the structures it involves. [medicalnewstoday.com]

• Arachnodactyly

  Of his five siblings one sister was diagnosed as Beals congenital arachnodactyly. Other siblings were normal. Routine X-rays showed middle third and lower third pseudarthrosis in both arms and elbow was free and mobile with no stiffness whatsoever. [posi.in]

• Cough

  When to call the doctor Following surgery, parents should call the doctor if any of these symptoms occur: Unexpected bleeding from the wound An oral temperature of over 101 degrees Pain that is nor relieved by pain medication A persistent dry cough Nausea [healthofchildren.com]

• Nausea

  When to call the doctor Following surgery, parents should call the doctor if any of these symptoms occur: Unexpected bleeding from the wound An oral temperature of over 101 degrees Pain that is nor relieved by pain medication A persistent dry cough Nausea [healthofchildren.com]

  Shortly after the second cycle of chemotherapy, she developed significant abdominal pain, nausea, vomiting, and diarrhea, requiring admission. [cureus.com]

• Vomiting

  […] call the doctor Following surgery, parents should call the doctor if any of these symptoms occur: Unexpected bleeding from the wound An oral temperature of over 101 degrees Pain that is nor relieved by pain medication A persistent dry cough Nausea or vomiting [healthofchildren.com]

  Shortly after the second cycle of chemotherapy, she developed significant abdominal pain, nausea, vomiting, and diarrhea, requiring admission. [cureus.com]

• Failure to Thrive

  […] to thrive Cataract Delayed speech and language development Myopia Frontal bossing Microphthalmia Delayed skeletal maturation Narrow mouth Long nose Telecanthus Thin vermilion border Short foot Delayed eruption of teeth Microcornea Hypoplasia of the maxilla [mendelian.co]

• Hand Deformity

  Syndactyly and polydactyly are the most common types of congenital hand deformities. Syndactyly is webbing or fusing between the digits (fingers or toes). The digits can be partially fused or fused along their entire length. [birthdefects.org]

  There is a familial tendency to develop this deformity. This deformity usually involves both hands, and males are more often affected than females. If the fingers are completely fused together, it is considered complete. [stanfordhealthcare.org]

  Syndactyly & Polydactyly (Webbed Fingers & Toes) | University of Utah Health Syndactyly is a hand deformity where two or more fingers (or toes) are fused together creating a webbed look. [healthcare.utah.edu]

• Fussiness

  After your child goes home, call the surgeon if you notice the following: Fever Fingers that tingle, are numb, or have a bluish tinge Severe pain (your child may be fussy or constantly crying) Swelling Outlook (Prognosis) The repair is usually successful [pennstatehershey.adam.com]

• Irritability

  This resulted in poor fit of the glove and chronic irritation of web. Note radial deviation of small finger due to contracture from patient's first surgery. Web space was deepened with local flaps and full-thickness skin grafts from left groin. [emedicine.medscape.com]

• Seizure

  We report on a de novo 0.5 Mb triplication (partial tetrasomy) of chromosome 17q25.3 in a 10-year-old girl with severe intellectual disability, infantile seizures (West syndrome), moderate hearing loss, Dandy-Walker malformation, microcephaly, craniofacial [ncbi.nlm.nih.gov]

  Another rare cause of the disorder is Fetal Hydantoin Syndrome, a result of the mother's use of the anti-seizure medication hydantoin, commonly known as dilantin, during pregnancy. [orthomedctr.com]

  […] clped1|ed4|syndactyly-ectodermal dysplasia-cleft/lip palate|cleft lip/palate-syndactyly-pili torti syndrome|ectodermal dysplasia, margarita island type|ectodermal dysplasia, cleft lip and palate, mental retar Related symptoms: Intellectual disability Seizures [mendelian.co]

Imaging techniques like transvaginal ultrasound is used to obtain images of fetal finger buds at 9 to 10 weeks of gestation. More detailed images can be obtained at 12 to 13 weeks of gestation [8]. Presence of family history of a child with an autosomal recessive syndrome associated with polydactyly, calls for first trimester imaging for diagnosis of fetal genetic syndrome. Detailed images of the fetal hands may be obtained during second-trimester survey. Multiple two-dimensional images may be required to see all the fingers [9]. Abnormal angulation in one or more of the digits is an indication of polydactyly. As the fingers are deformed, complex syndactyly is clear and easy to diagnose with ultrasound. In many cases, the hand appears mitten shape. Bone anomalies like synostosis, delta phalanx, or symphalangism, can be identified using radiographs.

Surgical repair is needed for most forms of syndactyly. Surgical procedure can be done at 5 to 6 months of age for infants who are full-term. Complex syndactyly may be associated with paronychia and in this case, hands are washed thoroughly with soap and water. Topical antibacterial solution or ointment is used. Oral antibiotics may be recommended in some cases. Early release of digits is important with respect to complex syndactyly. This will prevent malrotation and angulation that arise due to differential growth rates [10]. In complex syndactyly the first release is done after 6 months which will prevent the formation of permanent deformities. If more than one syndactyly is present, simultaneous surgical release is performed. And when fusion is present in both hands, bilateral release surgery can be performed. For children above 18 months, surgery should be planned unilaterally.

Good amount of antibiotic ointment is applied on the operated hand with a bulky dressing. Cotton fluffs are placed within the space of the web. Graft site is closed with steristrip and absorbable sutures. The dressing on the skin graft site is removed after 3 days, while the long splint on the hand is removed after 3 weeks. For a complex form of syndactyly, the next release may be performed after 6 months. Surgical release of syndactyly may lead to complications like recurrence, ischemia, and also complications associated with skin-graft. Distal migration of the web is also seen in many.

Simple forms of syndactylies are repaired within 12 to 14 months and this gives a good prognosis. Repair of simple syndactylies are avoided in newborns. Surgical repair at the right time helps to retain the functionality of the digits. If performed properly, surgical release of syndactyly will have very few complications. It can improve functioning of the hands and also provide normal appearance to the fingers and hands.

Failure of differentiation of fingers is the most common etiologic factor. It has an autosomal dominant pattern of inheritance and is strongly expressed in families [1]. Of the five different phenotypes of the condition, type I is caused by a mutation in a gene or genes in 2q34-q36. Type II and type V are caused by mutation in HOXD13. Type III results from mutation in the gene encoding GJA1. Mutations in gene that encodes for LMBR1 caused type IV [2] [3]. This condition is also associated with a number of syndromes. Complicated syndactyly is almost always associated with conditions like Apert syndrome. Syndactyly may also occur in association with other anomalies of hand like cleft hand and ulnar dysplasia. One of the studies has reported an association between syndactyly and smoking during pregnancy [4].

Syndactyly is the most common form of congenital malformation of limbs, found at a rate of 1 per 2000-3000 births [5]. The defect is twice as frequent among males when compared to females. It is also more common among whites than in blacks. Both right and left limbs are affected similarly by this condition. For any specific types of syndactyly, no difference is noted in the age of mother and father. It is seen as an inherited condition in about 10% of the cases and in most of the cases it is bilateral. The most commonly affected region is the third web space. This is followed by fourth, second and first.

Development of fingers occur during 8-10 weeks of gestation. Partitioning of digits occurs by programmed cell apoptosis and failure of this programmed cell death results in syndactyly [6]. Formation of interdigital clefts are mediated by apical ectodermal ridge. This proceeds from apex to the proximal part of the digit. Failure of the complete interdigital separation also results in syndactyly. Fusion of fingers causes impaired functioning of the hands and fingers. This impairment increases when fusion is complete or complex. Syndactyly in general represents skin shortage [7]. Webbing looks like presence of additional skin joining the digits. But studies show that there is 22% less skin covering syndactylized digits.

There are no known preventive measures.

Syndactyly is a common hereditary limb malformation characterized by fusion of two or more fingers due to incomplete differentiation of digital rays. Syndactyly is classified as simple syndactyly when only skin and soft tissues are involved in the fusion. Complex syndactyly refers to the involvement of soft tissues, bones and nails in the fusion. Syndactyly may also be grouped into complete and partial, depending on the extent of fusion. Partial syndactyly has the proximal segments of digits fused together, while complete syndactyly refers to fusion of the digits till the tip. Acrosyndactyly is the fusion of the distal portions of the digits. This condition is found to be associated with a number of syndromes including Poland syndrome and Apert syndrome. The most severe form of syndactyly is referred to as complicated syndactyly, characterized by fusion of bones and bone anomalies. Most forms of these malformations are treated through surgical repair between 12 to 14 months.

Syndactyly is one of the most common congenital malformations characterized by fusion of fingers and toes. Syndactyly may vary in severity from complete fusion of fingers or partial in one part of the finger. Partial syndactyly may show webbing of skin between the fingers. In complex syndactyly, bones and nails also may be involved in the fusion. Syndactyly may occur simultaneously with polydactyly in which an extra finger or toe may be present. Syndactyly may occur without any other birth defects or be associated with many syndromes. Syndactyly is seen one in 2000 births. It is found to run in families and is two times more common among males when compared to females. The most common affected finger is the third one. Both the sides are equally affected by this condition.

Genetic factors are the most important cause of syndactyly. Mutations in many genes that control the differentiation of fingers in fetus lead to their fusion during development. Development of fingers occur during 8-10 weeks of pregnancy. The gene is a dominant one and when one parent has the gene, each offspring has 50% chances of having syndactyly. Syndactyly may affect the functioning of the finger and growth may be limited. The condition can occur in isolation or sporadically. It may also occur as a part of genetic syndrome. Impairment of finger is more with complete or complex syndactyly.

Syndactyly is visible during initial physical examination after birth. Image of the fetal fingers can be obtained through transvaginal ultrasound at 9 to 10 weeks of gestation. Detailed image of the hand can be obtained during second trimester survey. Complex syndactyly is more clear and easy to diagnose with ultrasound. Radiography is used to identify bone anomalies along with fusion of fingers.

Most forms of syndactyly require surgical release. It is usually done at 5 to 6 months of age in children who are full-term. Early surgical repair will help in preventing complications and permanent deformities. If more than one fingers are fused, simultaneous surgical repair may be performed. When fusion is present in both hands, bilateral surgery is performed. If the child is more than 18 months, surgery is usually done unilaterally. Surgical repair may result in complications like recurrence, ischemia and graft-related complications.

1. Rypens F, Dubois J, Garel L, Obstetric US: watch the fetal hands. Radiographics. 2006;26:811-830. 
2. Boss K, Betz RC, Lee YA, etal. Localization of a gene for syndactyly type I to chromosome.2q34-q36.Am J Hum Genet. 2000;67:492-497. 
3. Sarfarazi M, Akarsu AN, Sayli BS. Localization of the syndactyly type II (synpolydactyly) locus to 2q31 region and identification of tight linkage to HOXD8 intragenic marker. Human Mol Genet. 1995;4:1453-1458. 
4. Man LX, Chang B. Maternal cigarette smoking during pregnancy increases the risk of having a child with a congenital digital anomaly. Plast Reconstr Surg. 2006;117(1):301-8.
5. Lamb DW, Wynne-Davies R, Soto L. An estimate of the population frequency of congenital malformations of the upper limb. J Hand Surg [Am]. 1982;7(6):557-62.
6. Light TR, Manske P. Congenital hand malformations and deformities of hand. Instr Course Lect. 1989;38:31-71. 
7. Eaton CJ, Lister SD. Syndactyly. Hand Clin. 1990;6(4):555-575. 
8. Bromley B, Shipp TD, Benaceraff B. Isolated polydactyly: prenatal diagnosis and perinatal outcome. Prenat Diagn. 2000;20:905-908. 
9. Budorick NE, Pretorius DH, Johnson DD, et al. Three-dimensional ultrasound examination of the fetal hands: normal and abnormal. Ultrasound obstet Gynecol. 1998;12:227.
10. Vekris MD, Lykissas MG, Soucacos PN, Korompilias AV, Beris AE. Congenital syndactyly: outcome of surgical treatment in 131 webs. Tech Hand Up Extrem Surg. 2010;14(1):2-7.