Polydactyly is a

birth defect A birth defect is an abnormal condition that is present at birth, regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can range from mild to severe. Birth de ...

that results in

extra Extra, Xtra, or The Extra may refer to: Arts, entertainment and media Film * The Extra (1962 film), ''The Extra'' (1962 film), a Mexican film * The Extra (2005 film), ''The Extra'' (2005 film), an Australian film Literature * Extra (newspaper), ...

fingers or toes. The hands are more commonly involved than the feet. Extra fingers may be painful, affect

self-esteem Self-esteem is confidence in one's own worth, abilities, or morals. Self-esteem encompasses beliefs about oneself (for example, "I am loved", "I am worthy") as well as emotional states, such as triumph, despair, pride, and shame. Smith and Macki ...

, or result in clumsiness. It is associated with at least 39 genetic mutations. It may either present alone or with other defects. Cases may run in families. The underlying mechanism involves an error in

limb bud The limb bud is a structure formed early in vertebrate limb development. As a result of interactions between the ectoderm and underlying mesoderm, formation occurs roughly around the fourth week of development. In human embryonic development, the ...

formation during

early development Prenatal development () involves the development of the embryo and of the fetus during a viviparous animal's gestation. Prenatal development starts with fertilization, in the germinal stage of embryonic development, and continues in fetal deve ...

. Diagnosis may occur before birth via

prenatal ultrasound Obstetric ultrasonography, or prenatal ultrasound, is the use of medical ultrasonography in pregnancy, in which sound waves are used to create real-time visual images of the developing embryo or fetus in the uterus (womb). The procedure is a stand ...

as early as nine weeks. X-rays may be useful after a child is a year old. The opposite is

oligodactyly Oligodactyly () is the presence of fewer than five digits (fingers or toes) on a hand or foot.cautery to more involved surgery. While putting a tight band around the base has been carried out, this is not typically recommended. If surgery is required, this is often done around two years of age. Occasionally multiple surgeries are required. Polydactyly is present in about 4 to 12 per 10,000 newborns. It is the most common defect of the hands and feet. In the United States,

Black people Black is a racial classification of people, usually a political and skin color-based category for specific populations with a mid- to dark brown complexion. Not all people considered "black" have dark skin and often additional phenotypical ...

are more commonly affected than white people. The term is .

Signs and symptoms

In humans/animals this condition can present itself on one or both hands or feet. The extra digit is usually a small piece of soft tissue that can be removed. Occasionally it contains bone without joints; rarely it may be a complete functioning digit. The extra digit is most common on the

ulna The ulna or ulnar bone (: ulnae or ulnas) is a long bone in the forearm stretching from the elbow to the wrist. It is on the same side of the forearm as the little finger, running parallel to the Radius (bone), radius, the forearm's other long ...

r (little finger) side of the hand, less common on the

radial Radial is a geometric term of location which may refer to: Mathematics and Direction * Vector (geometric), a line * Radius, adjective form of * Radial distance (geometry), a directional coordinate in a polar coordinate system * Radial set * A ...

(

thumb The thumb is the first digit of the hand, next to the index finger. When a person is standing in the medical anatomical position (where the palm is facing to the front), the thumb is the outermost digit. The Medical Latin English noun for thumb ...

) side, and very rarely within the middle three digits. These are respectively known as postaxial (little finger), preaxial (thumb), and central (ring, middle, index fingers) polydactyly. The extra digit is most commonly an abnormal fork in an existing digit, or it may rarely originate at the wrist as a normal digit does. Polydactyly can be divided into three major types, which are discussed below, which depend on the location of the additional digit. In 2019 it was found that in cases of polydactyly with a fully functional additional digit, muscles to control the extra digit may be duplicated, resulting in increased motor control that allows the patient to carry out certain tasks with one hand that would normally require two. File:Polydactyly (cropped).jpg, Male with unilateral preaxial polydactyly affecting the left thumb. The supernumerary digit had normal sensation but no joint and hence could not move independently. File:Polydactyly Left Hand.jpg, Type 1 ulnar polydactyly. An extra digit is attached by skin and nerves. File:Preaxial polydactyly right hand.jpg, Preaxial polydactyly

Ulnar or postaxial

This is the most common situation, in which the extra digit is on the ulnar side of the hand, thus the side of the little finger. This can also be called postaxial polydactyly. It can manifest itself very subtly, for instance only as a nubbin on the ulnar side of the little finger, or very distinctly, as a fully developed finger. Most commonly, the extra finger is rudimentary, consisting of an end

phalanx The phalanx (: phalanxes or phalanges) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar polearms tightly packed together. The term is particularly used t ...

with a nail, and connected to the hand with a small skin pedicle. Mostly one neurovascular bundle can be identified, with no tendons present in the extra digit. In case of a fully developed extra finger, the duplication usually presents itself at the level of the metacarpophalangeal joint. A triplication of the little finger is very rare. Ulnar polydactyly occurs ten times more often in African populations. The incidence in Caucasians is reported as 1 in 1,339 live births, compared with 1 in 143 live births in Africans. Ulnar polydactyly is also often part of a syndrome. In patients with African ancestry ulnar polydactyly mostly occurs isolated, whereas the presentation in Caucasians is often associated with a syndrome, though in a retrospective review, only 4 of 37 cases of ulnar polydactyly in Caucasians were syndromic.

Radial or preaxial

This is a less common situation, in which the affectation is on the side of the hand towards the thumb. Radial polydactyly refers to the presence of an extra digit (or extra digits) on the radial side of the hand. It is most frequent in Indian populations and it is the second most common congenital hand disorder. The incidence of radial polydactyly is reported as 1 in every 3,000 live births. The clinical features of radial polydactyly will depend upon the extent of duplication. Radial polydactyly varies from a barely visible radial skin tag to complete duplication. Thumb polydactyly varies from barely visible broadening of the distal phalanx to full duplication of the thumb including the first metacarpal. Radial polydactyly is frequently associated with several syndromes.

Central

This is a rare condition, in which the extra digit is on the ring, middle or index finger. Of these fingers, the index finger is most often affected, whereas the ring finger is rarely affected. This type of polydactyly can be associated with

syndactyly Syndactyly is a condition wherein two or more digits are fused together. It occurs normally in some mammals, but is an unusual condition in humans. The term is . Classification Syndactyly can be simple or complex. * In simple syndactyly, adja ...

cleft hand Ectrodactyly, split hand, or cleft hand () involves the deficiency or absence of one or more central digits of the hand or foot and is also known as split hand/split foot malformation (SHFM). The hands and feet of people with ectrodactyly (ectr ...

, and several other syndromes. Polysyndactyly presents various degrees of syndactyly affecting fingers three and four.

Causes

Polydactyly is associated with different mutations, either mutations in a gene itself or in a

cis-regulatory element ''Cis''-regulatory elements (CREs) or ''cis''-regulatory modules (CRMs) are regions of non-coding DNA which regulate the transcription of neighboring genes. CREs are vital components of genetic regulatory networks, which in turn control morpho ...

responsible for the expression of a specific gene. Mutations in Hoxa- or Hoxd clusters are reported leading to polydactyly. Interactions of Hoxd13 and GLI3 induce

synpolydactyly Synpolydactyly (SPD) is a joint presentation of syndactyly (fusion of digits) and polydactyly (production of supernumerary digits).Goodman FR, Mundlos S, Muragaki Y, et al. Synpolydactyly phenotypes correlate with size of expansions in hoxd13 poly ...

, a combination of extra and consolidated digits. Other signal transduction pathways in this context are the

Wnt signaling pathway In cellular biology, the Wnt signaling pathways are a group of signal transduction pathways which begin with proteins that pass signals into a cell through cell surface receptors. The name Wnt, pronounced "wint", is a portmanteau created from the ...

or Notch. In the specific case of preaxial polydactyly (Hemingway mutant), a cis-acting mutation approximately 1Mb upstream of SHH gene has been implicated. Normally SHH is expressed in an organiser region, called the

zone of polarizing activity The zone of polarizing activity (ZPA) is an area of mesenchyme that contains signals which instruct the developing limb bud to form along the anterior/posterior axis. Limb bud is undifferentiated mesenchyme enclosed by an ectoderm covering. Event ...

(ZPA) on the posterior limb side. From there it diffuses anteriorly, laterally to the growth direction of the limb. In the mutant, smaller ectopic expression in a new organiser region is seen on the anterior side of the limb. This ectopic expression causes cell proliferation delivering the raw material for one or more new digits. Polydactyly can occur by itself, or more commonly, as one feature of a

syndrome A syndrome is a set of medical signs and symptoms which are correlated with each other and often associated with a particular disease or disorder. The word derives from the Greek language, Greek σύνδρομον, meaning "concurrence". When a sy ...

of congenital anomalies. When it occurs by itself, it is associated with

autosomal dominant In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the Phenotype, effect of a different variant of the same gene on Homologous chromosome, the other copy of the chromosome. The firs ...

mutations in single genes, i.e. it is not a multifactorial trait. But mutation in a variety of genes can give rise to polydactyly. Typically the mutated gene is involved in developmental patterning, and a syndrome of congenital anomalies results, of which polydactyly is one feature or two. Polydactyly has been linked to the prenatal environment in a 2020 study showing a relationship to maternal

PM10 Particulate matter (PM) or particulates are microscopic particles of solid or liquid matter suspended in the air. An ''aerosol'' is a mixture of particulates and air, as opposed to the particulate matter alone, though it is sometimes defined ...

pollution exposure in China. Types include:

Syndromes

Because polydactyly can be part of a

(known genetic defect) or association (genetic defect not known), children with a congenital upper extremity deformity should be examined by a

geneticist A geneticist is a biologist or physician who studies genetics, the science of genes, heredity, and variation of organisms. A geneticist can be employed as a scientist or a lecturer. Geneticists may perform general research on genetic process ...

for other congenital anomalies. This should also be done if a syndrome is suspected, or if more than two or three generations of the family are affected. As of 2009, 97 genetic syndromes have been associated with different kinds of polydactyly. Examples of syndromes include

Diamond–Blackfan anemia Diamond–Blackfan anemia (DBA) is a congenital pure red blood cell aplasia that usually presents in infancy. DBA causes anemia, but has no effect on the other blood components (platelets, white blood cells). This is in contrast to Shwachman–B ...

, and the

VACTERL association The VACTERL association (also VATER association, and less accurately VACTERL syndrome) refers to a recognized group of birth defects which tend to co-occur (see below). This pattern is a recognized association, as opposed to a syndrome, because th ...

acrocallosal syndrome Acrocallosal syndrome (also known as ACLS) is an extremely rare Dominance (genetics), autosomal recessive syndrome characterized by corpus callosum agenesis, polydactyly, multiple dysmorphic features, motor and intellectual disabilities, and other ...

, basal cell nevus syndrome, Biemond syndrome, ectrodactyly-ectodermal dysplasias-cleft lip/palate syndrome, mirror hand deformity, Mohr syndrome, oral-facial-digital syndrome, Rubinstein–Taybi syndrome, short rib polydactyly.

Ulnar

Ulnar polydactyly is often bilateral and associated with

and polydactyly of the feet. This can be a simple or complex polydactyly. Ulnar polydactyly occurs as an isolated congenital condition, but can also be part of a syndrome, such as: Trisomy 13,

Greig cephalopolysyndactyly syndrome Greig cephalopolysyndactyly syndrome is a disorder that affects development of the limbs, head, and face. The features of this syndrome are highly variable, ranging from very mild to severe. People with this condition typically have one or more ...

Meckel syndrome Meckel may refer to: People German anatomist/physician family Meckel * Johann Friedrich Meckel, the Younger (1781–1833), German anatomist * Johann Friedrich Meckel, the Elder (1724–1774) German anatomist, grandfather of the Younger * Ph ...

, Ellis–van Creveld syndrome,

McKusick–Kaufman syndrome McKusick–Kaufman syndrome (MKS) is a rare genetic condition caused by mutations in the '' MKKS'' gene, which affect how cells develop and function. It is named after Dr. Robert L. Kaufman and Victor McKusick, who studied the condition and helped ...

, Down syndrome,

Bardet–Biedl syndrome Bardet–Biedl syndrome (BBS) is a ciliopathic human genetic disorder that produces many effects and affects many body systems. It is characterized by rod/cone dystrophy, polydactyly, central obesity, hypogonadism, and kidney dysfunction in ...

Smith–Lemli–Opitz syndrome Smith–Lemli–Opitz syndrome is an inborn error of metabolism, inborn error of cholesterol synthesis. It is an autosome, autosomal recessive (genetics), recessive, multiple malformation syndrome caused by a mutation in the enzyme 7-Dehydrochole ...

Radial

Type VII of radial polydactyly is associated with several syndromes:

Holt–Oram syndrome Holt–Oram syndrome (also called atrio-digital syndrome, atriodigital dysplasia, cardiac-limb syndrome, heart-hand syndrome type 1, HOS, ventriculo-radial syndrome) is an autosomal dominant disorder that affects bones in the arms and hands (th ...

Fanconi anemia Fanconi anemia (FA) is a rare, autosomal recessive genetic disease characterized by aplastic anemia, congenital defects, endocrinological abnormalities, and an increased incidence of developing cancer. The study of Fanconi anemia has improve ...

(aplastic anemia by the age of 6), Townes–Brocks syndrome, and Greig cephalopolysyndactyly (also known to occur with ulnar polydactyly).

Central

The syndromes associated with central polydactyly are:

, Pallister–Hall syndrome, Legius syndrome,

. Central polydactyly can also be associated with

and

Evolution

From an evo-devo point of view, polydactyly is a phenotypic variation or innovation, as the fingers and toes arise in places where nothing is phenotypically present in the wild type. Although it is initiated by a point mutation, it occurs as a

polyphenism A polyphenic trait is a trait for which multiple, discrete phenotypes can arise from a single genotype as a result of differing environmental conditions. It is therefore a special case of phenotypic plasticity. There are several types of polyphen ...

with different numbers of toes. The analysis of the additional toe numbers of

Maine Coon The Maine Coon is a large Domestication, domesticated breeds of cats, cat breed. One of the oldest natural breeds in North America, the breed originated in the U.S. state of Maine, where it is the official List of U.S. state mammals, state cat ...

cats revealed that the number of toes follows a developmental bias: 2 additional toes occur much more frequently than 4, these more frequently than 6 or 8 additional ones. Also, for the evo-devo theory, polydactyly cannot be adequately explained by genetic mutation alone, but only by constructive development, i.e. the ability of development to produce a complex phenotypic output. The corresponding symbolic generation of toes can now be shown in computer models.

Diagnosis

Classification is performed by using x-ray imaging to see the bone structures. In 1961, Frantz and O'Rahilly proposed that congenital anomalies of the limb could be classified in seven categories, based on the embryonic failure causing the clinical presentation. These categories are failure of formation of parts, failure of differentiation, duplication, overgrowth, undergrowth, congenital constriction band syndrome, and generalized skeletal abnormalities. In 1976 this was modified by Swanson. Polydactyly belongs to the category of duplication. As of 2009, research has shown that the majority of congenital anomalies occur during the 4-week embryologic period of rapid limb development.

Ulnar

The classification of ulnar polydactyly exists of either two or three types. The two-stage classification, according to Temtamy and McKusick, involves type A and B. In type A there is an extra little finger at the metacarpophalangeal joint, or more proximal including the carpometacarpal joint. The little finger can be hypoplastic or fully developed. Type B varies from a nubbin to an extra, non-functional little finger part on a pedicle. According to the three-type classification, type I includes nubbins or floating little fingers, type II includes duplications at the MCPJ, and type III includes duplications of the entire ray.

Radial

The Wassel classification is the most widely used classification of radial polydactyly, based upon the most proximal level of skeletal duplication. The most common type is Wassel 4 (about 50% of such duplications) followed by Wassel 2 (20%) and Wassel 6 (12%).

Central

The classification of central polydactyly is based on the extent of duplication and involves the following three types: Type I is a central duplication, not attached to the adjacent finger by osseous or ligamentous attachments; it frequently does not include bones, joints, cartilage, or tendons. Type IIA is a nonsyndactylous duplication of a digit or part of a digit with normal components, and articulates with a broad or bifid metacarpal or phalanx. Type IIB is a syndactylous duplication of a digit or part of a digit with normal components, and articulates with a broad or bifid metacarpal or phalanx. Type III is a complete digital duplication, which has a well-formed duplicated metacarpal. File:Polydactyly_01_Lhand_AP.jpg,

X-ray An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...

of type III central polydactyly. The middle fingers are the same length. File:X-ray of feet in polydactyly.jpg, Right-sided duplication of the right little toe in an 8.5 months old male, with two toes (fifth and sixth) apparently forming joints with the fifth metatarsal bone, which is mildly broadened distally. The duplicated toes have almost normal growth. The fifth toe has mild varus angulation, and the sixth toe has substantial valgus angulation. File:Polydactyly 01 Lfoot AP.jpg, Left foot with postaxial polydactyly of 5th ray

Treatment

Ulnar

Ulnar polydactyly usually does not interfere with hand function, but for social reasons it can be treated operatively.

Type A

The treatment of Type A ulnar polydactyly is complex as its goal is to remove the accessory digit while maintaining a stable, functional small finger. When the duplicated proximal phalanx articulates with a common, broad metacarpal head, the ulnar collateral ligament must be considered. In those cases with a common articulation or with a sixth metacarpal the muscle executing the abduction of the little finger (''abductor digiti minimi'') must be preserved. In patients with a common metacarpal articulation an elliptical incision at the base of the post-axial digit is made. This incision may be extended proximally in order to adequately expose the ''abductor digiti minimi''. The ulnar collateral ligament and the insertions of the ''abductor digiti minimi'' are then elevated with a periosteal sleeve. The duplicated extensor and flexor tendons to the ulnar digit are transected and after that the digit is amputated at its articulation with the metacarpal. If the articular surface is wide the metacarpal may be shaved. At last the collateral ligament and ''abductor digiti minimi'' are reinserted at the base of the preserved proximal phalanx and a wire is then placed across the reconstructed joint. In patients with a duplicated metacarpal, the accessory digit is amputated in a standard ray fashion with transfer of the ''abductor digiti minimi'' to the retained small finger.

Type B ulnar

In this situation there is an absence of osseous and ligamentous structures. The surgical technique is analogous to radial polydactyly, in which the level of duplication and anatomical components should guide operative treatment. The pedicled ulnar extra digit can be removed by suture ligation to devise the skin bridge of the newborn child. This might be easier than an excision of the extra digit when the child is 6 to 12 months old. Ligation occludes the vascular supply to the duplicated digit, resulting in dry gangrene and subsequent autoamputation. This must be done with consideration of the presence of a neurovascular bundle, even in very small skin bridges. When the ligation is done inappropriately it can give a residual nubbin. Also, a neuroma can develop in the area of the scar. An excision can prevent the development of a residual nubbin and the sensitivity due to a neuroma. For infants with ulnar type B polydactyly the recommended treatment is ligation in the neonatal nursery. A 2011 study opined that excision of an extra digit in the neonatal nursery was a safe and simple procedure with a good clinical and cosmetic outcome. As of 2022, for infants with ulnar type B polydactyly the recommended treatment is surgical excision or suture ligation, when no bony structures exist. Complications of ligation include infection, neuroma or cyst formation.

Radial

Because neither of the two thumb components is normal, a decision should be taken on combining which elements to create the best possible composite digit. Instead of amputating the most hypoplastic thumb, preservation of skin, nail, collateral ligaments and tendons is needed to augment the residual thumb. Surgery is recommended in the first year of life, generally between 9 and 15 months of age. Surgical options depend on type of polydactyly.

Bilhaut-Cloquet procedure

This type of procedure is recommended for Wassel types 1 and 2 (in which both thumbs are severely hypoplastic) by some congenital hand surgeons. The technique contains a composite wedge resection of the central bone and soft-tissue. This will be achieved with approach of the lateral tissue of each thumb. The goal is to achieve a normal thumb, what concerns the size, which is possible. If the width of the nail bed is greater than 70% of the contralateral thumb, it may be split.

Ablation with collateral ligament reconstruction

This type of procedure is used for all Wassel types of polydactyly and is the most commonly used technique. It is recommended in all cases of thumb duplication with a hypoplastic, less-functional thumb. Otherwise, one could consider the Bilhaut-Cloquet. The ulnar thumb is preferably preserved as it is the more developed one in most cases. By detaching the radial collateral ligament from distal to proximal, a periosteal sleeve can be preserved. In this way, the radial collateral band of the radial digit will function as the absent radial collateral ligament of the preserved ulnar thumb. Elevation of the APB and FPB is performed in Wassel type 4 duplication; this can be accomplished via the periosteum or separately. As the tendons insert proximally, the elevation is performed proximally too to potentially rebalance the ulnar thumb. After the radial thumb is amputated, the ulnar elements are centralized and fixed with a

Kirschner wire Kirschner wires or K-wires or pins are sterilized, sharpened, smooth stainless steel pins. Introduced in 1909 by Martin Kirschner, the wires are now widely used in orthopedics and other types of medical and veterinary surgery. They come in differ ...

. In most cases, a longitudinal and sagittal osteotomy is needed to centralize the bony parts of the ulnar thumb. While the soft-tissue of the radial thumb was preserved, it is now attached to the radial side of the ulnar thumb together with the periosteal sleeve. The APB and FPB of the ablated radial thumb are attached to the distal phalanx for more stability. If necessary, the extensor pollicis longus and the flexor pollicis longus are reattached to centralize their course. In Wassel type 5 and 6 the opponens pollicis muscle must be transferred to the ulnar metacarpal. Soft tissue with collateral ligament reconstruction is used to avoid any angular deformity in the preserved thumb. Tendon centralization is also often used for correction. Still, cases with osseous deformities may happen. To provide alignment, osteotomies are necessary to be done. This operation may need bone grafting, which is obtained from the amputated thumb.

On top plasty procedure

This type is indicated when one thumb is larger proximally and the other thumb has a larger distal component. (The procedure is initially described as a way to lengthen amputated digits.) The goal is to create a functional thumb by combining less-hypoplastic components. On top plasty procedure is rarely employed in the treatment of congenital thumb duplication. It might be necessary for Wassel types 4, 5, 6. At the level of the mid-proximal phalanx or mid-metacarpal, the distal component is transferred to the proximal component. The tendons of the distal component are preserved as the rest of the distal component is amputated. The neurovascular bundle which supplies the distal component is reserved and transferred proximally.

Central

Early osteotomy and ligament reconstructions should be done to prevent deformities, such as angular growth deformities. The surgical treatment of central polydactyly is highly variable. After the surgery the hand must be functional and stable, but also aesthetically pleasing. This requires intraoperative creativity and flexibility. The surgeon must also consider whether retention of a fully functional supranumerary digit is preferable to surgical intervention. In contrast, a functional, four-fingered hand achieved via ray amputation may be preferable to a five-fingered hand with a deformed or stiff reconstructed finger. Cases of polysyndactyly are approached through a standard opposing zig-zag incision. The incision is favored toward the accessory digit, preserving extra skin for subsequent closure. Depending on the level and extent of duplication, the flexor and extensor tendons may require centralization or rebalancing. Also, the collateral ligaments must be preserved or reconstructed. Wide articular surfaces should be narrowed and phalangeal wedge osteotomies may be required to provide an axial alignment. Attention must also be given to reconstruct the intermetacarpal ligament. Furthermore, one should take in mind the provision for adequate web-space soft tissue.

Complications

Complications include: painful scarring, infection, joint instability, residual deformity, angulated growth, growth arrest, joint stiffness, and nail bed deformities. A 2014 study reported a 19% revision rate for preaxial polydactyly for pain or instability.

Prognosis

Ulnar

Type A

There are no substantive outcome studies regarding the function of these hands following surgical intervention. This is mainly caused by the fact that there is a generally normal function of these patients' hands following ablation with collateral ligament reconstruction. In a study on 27 patients undergoing surgical excision for Type A ulnar polydactyly, only one complication was noted in the form of an infection. However, no investigators have objectively reviewed functional range of motion or articular stability.

Type B

In a study on 21 patients with Type B ulnar polydactyly treated with suture ligation it was found that the duplicated digit was typically amputated at an average of 10 days and no complications of infection or bleeding were reported. In a large study on 105 patients treated with suture ligation an overall complication rate of 23.5% was reported, citing a residual tender or unacceptable bump in 16%, infection in 6%, and bleeding in 1% of patients. In general, suture ligation is safe and effective when applied to appropriate cases of Type B polydactyly in which no substantial ligamentous or osseous structures are present within the pedicle. Parents should be educated as to the progression of necrosis, and that revision of residual tissue or scar may be necessary when the child is six months of age or older.

Radial

Bilhaut procedure

Advantages: By combining two hypoplastic thumbs a sufficient thumb size is acquired. Furthermore, the IP and MCP joints are very stable as the collateral ligaments are not violated during reconstruction. Disadvantages: Violation during reconstruction can lead to growth arrest or asymmetric growth. Nail deformity could also occur after reconstruction. Although the joints are stable, restriction of flexion may be possible. The average IP flexion in a reconstructed thumb is 55 degrees less than the contralateral thumb. MCP flexion averaged 55 degrees in reconstructed thumbs, compared to 75 degrees in the contralateral thumb.

Ablation with colateral ligament reconstruction

Advantages: The reconstructed joints tend to remain flexible. Also, it preserves the nail bed and physis, this increases the prevention of nail deformities over time. Disadvantages: Although surgeons try to obtain a stable thumb of appropriate size, instability of the IP and MCP joint may occur, as well as a size mismatch. Thumbs are defined as unacceptable if IP joint deviation exceeds 15 degrees, MCP joint deviation exceeds 30 degrees, and thumb size is inappropriate based on the examiner's assessment. Also, thumb size one-third greater or less than the contralateral thumb is defined as unacceptable.

On-top plasty procedure

No surgical outcomes studies exist for evaluating the function of the thumbs after an on-top plasty reconstruction.

Central

Few clinical outcome studies exist regarding the treatment of central polydactyly. Tada and colleagues note that satisfactory surgical correction of central polydactyly is difficult to achieve and that outcomes are generally poor. In Tada's study, 12 patients were reviewed. All patients required secondary surgical procedures to address flexion contractures and angular deviation at the IP joint level. However, several primary factors contribute to the complexity of central polydactyly reconstruction. Hypoplastic joints and soft tissues that predispose the reconstructed finger to joint contracture, and angular deformities as well as complex tendon anomalies, are often difficult to address. Therefore, treatment is wholly dependent on the anatomic components present, the degree of syndactyly, and the function of the duplicated finger.

Epidemiology

The condition has an estimated occurrence of 0.3–3.6 per 1000 live births. Postaxial hand polydactyly is most frequent in the United States in Black males. Preaxial polydactyly occurs in 0.08 to 1.4 in 1,000 live births. In the United States, it is more common in White people and also relatively frequent in Native American and Asian people. A 1994 study by Finley et al. combined data from Jefferson County,

Alabama Alabama ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South, Deep Southern regions of the United States. It borders Tennessee to the north, Georgia (U.S. state), Georgia to the east, Florida and the Gu ...

, United States, and

Uppsala County Uppsala County () is a county or '' län'' on the eastern coast of Sweden, whose capital is the city of Uppsala. It borders the counties of Dalarna, Stockholm, Södermanland, Västmanland, Gävleborg, and the Baltic Sea. Province The nor ...

, Sweden. This study found incidence of all types of polydactyly at rates of 2.3 per 1000 live births of White males, 0.6 per 1000 live births of White females, 13.5 per 1000 live births of Black males, and 11.1 per 1000 live births of Black females.

Society and culture

People affected

* Antonio Alfonseca, retired MLB professional baseball pitcher known as ''El Pulpo'' (Spanish for "the Octopus") for his extra digit on each extremity. *

Endre Ady Endre Ady (Hungarian: ''diósadi Ady András Endre,'' archaic English: Andrew Ady; 22 November 1877 – 27 January 1919) was a turn-of-the-century Hungarian poet and journalist. Regarded by many as the greatest Hungarian poet of the 20th centur ...

, Hungarian poet born with six fingers, but one was removed as a child. The poet later interpreted it as a sign of his selection (according to the ancient Hungarian belief, the

táltos The táltos (; also "tátos") is a figure in Hungarian mythology, a person with supernatural power similar to a shaman. Description The most reliable account of the táltos is given by Roman Catholic priest Arnold Ipolyi in his collection of fol ...

are born with more bones, such as six fingers). * Brites de Almeida, a legendary Portuguese woman who killed seven hiding Castilian soldiers in her oven after the

Battle of Aljubarrota The Battle of Aljubarrota was fought between the Kingdom of Portugal and the Crown of Castile on 14 August 1385. Forces commanded by King John I of Portugal and his general Nuno Álvares Pereira, with the support of English allies, opposed the a ...

, had six fingers on each hand. * The actress

Gemma Arterton Gemma Christina Arterton (born 2 February 1986) is a British actress. After her stage debut in Shakespeare's ''Love's Labour's Lost'' at the Globe Theatre (2007), Arterton made her feature-film debut in the comedy '' St Trinian's'' (2007). She p ...

was born with six fingers on each hand, the additional fingers being removed after birth. * Robert Chambers, purported author of ''

Vestiges of the Natural History of Creation ''Vestiges of the Natural History of Creation'' is an 1844 work of speculative natural history and philosophy by Robert Chambers. Published anonymously in England, it brought together various ideas of stellar evolution with the progressive tra ...

'', and his brother William had six digits on each limb. * Lucille Clifton, an African-American poet and civil rights advocate. * Zerah Colburn, American prodigious math calculating savant. * Calvin Choy, a Hong Konger singer and actor nicknamed "Sir One One" (Sir11) as he has six digits on his right hand. * Fourteen members of a Da Silva family in

São Paulo São Paulo (; ; Portuguese for 'Paul the Apostle, Saint Paul') is the capital of the São Paulo (state), state of São Paulo, as well as the List of cities in Brazil by population, most populous city in Brazil, the List of largest cities in the ...

, Brazil, have six functional fingers on each hand (the thumb is doubled) and six toes on each foot. * Danny Garcia, boxing champion, has six toes on his right foot. * Yoandri Hernández Garrido, nicknamed ''Veinticuatro'' ("twenty four" in Spanish), has six fully formed fingers on both hands and six perfect toes on each foot. *

Hampton Hawes Hampton Barnett Hawes Jr. (November 13, 1928 – May 22, 1977) was an American jazz pianist. He was the author of the memoir ''Raise Up Off Me'', which won the Deems-Taylor Award for music writing in 1975. Early life Hampton Hawes was born on No ...

jazz Jazz is a music genre that originated in the African-American communities of New Orleans, Louisiana, in the late 19th and early 20th centuries. Its roots are in blues, ragtime, European harmony, African rhythmic rituals, spirituals, h ...

pianist A pianist ( , ) is a musician who plays the piano. A pianist's repertoire may include music from a diverse variety of styles, such as traditional classical music, jazz piano, jazz, blues piano, blues, and popular music, including rock music, ...

, was born with six fingers on each hand (the extra fingers were surgically removed shortly after birth). *

Henry II the Pious Henry II the Pious (; 1196 – 9 April 1241) was Duke of Silesia and High Duke of Poland as well as Duke of South-Greater Poland from 1238 until his death. Between 1238 and 1239 he also served as regent of Sandomierz and Opole– Racibórz. He ...

, High Duke of Poland 1238–1241, had six toes on his left foot. * A boy named Hong Hong born in

Pingjiang County Pingjiang County () is a county in the northeast of Hunan province, China. It is the easternmost county-level division of the prefecture-level city of Yueyang. The county is located on the eastern margin of the province, the Miluo River runs ...

Hunan province Hunan is an inland province in Central China. Located in the middle reaches of the Yangtze watershed, it borders the province-level divisions of Hubei to the north, Jiangxi to the east, Guangdong and Guangxi to the south, and Guizhou and Chon ...

, China, has 31 fingers and toes. * Kamani Hubbard, a boy in California, was born in 2009 with a rare case of polydactyly, with 12 fingers and 12 toes, all fully functional. * Johann Jacob Freiherr von Moscon (1621–1661), Lower Styrian baron, is depicted with six fingers at his left hand on a portrait from Brežice, Slovenia. *

Jiang Qing Jiang Qing (March 191414 May 1991), also known as Madame Mao, was a Chinese communist revolutionary, actress, and political figure. She was the fourth wife of Mao Zedong, the Chairman of the Chinese Communist Party, Chairman of the Communis ...

Mao Zedong Mao Zedong pronounced ; traditionally Romanization of Chinese, romanised as Mao Tse-tung. (26December 18939September 1976) was a Chinese politician, revolutionary, and political theorist who founded the People's Republic of China (PRC) in ...

's fourth wife, reportedly had six toes on her right foot. *

Hrithik Roshan Hrithik Roshan (; born 10 January 1974) is an Indian actor who works in Hindi cinema. He has portrayed a variety of characters and is known for his dancing skills. One of the highest-paid actors in India, he has won many awards, including si ...

, a

Bollywood Hindi cinema, popularly known as Bollywood and formerly as Bombay cinema, is primarily produced in Mumbai. The popular term Bollywood is a portmanteau of "Bombay" (former name of Mumbai) and "Cinema of the United States, Hollywood". The in ...

actor born with a supernumerary thumb on his right hand. *

Nayanthara Nayanthara (born Diana Mariam Kurian; 18 November 1984) is an Indian actress and producer known for her work in Tamil cinema, Tamil, Telugu cinema, Telugu and Malayalam cinema, Malayalam films. One of the highest-paid actresses in India, she ...

, an Indian actress, has a rudimentary finger on her left hand. * J. J. Weaver, an American college football outside linebacker, has six fingers on his right hand. * Akshat Saxena from

Uttar Pradesh Uttar Pradesh ( ; UP) is a States and union territories of India, state in North India, northern India. With over 241 million inhabitants, it is the List of states and union territories of India by population, most populated state in In ...

, India, is the world record holder for highest number of digits. He was born in 2010 with seven digits on each hand and 10 digits on each foot, for a total of 34 digits. *

Garfield Sobers The Right Excellent Sir Garfield St Aubrun Sobers, NH, AO, OCC (born 28 July 1936), also known as Sir Gary or Sir Garry Sobers, is a Barbadian born former cricketer who played for the West Indies between 1954 and 1974. A highly skilled bowle ...

, West Indian

cricket Cricket is a Bat-and-ball games, bat-and-ball game played between two Sports team, teams of eleven players on a cricket field, field, at the centre of which is a cricket pitch, pitch with a wicket at each end, each comprising two Bail (cr ...

er, had an extra finger on each hand which he removed himself during childhood "with the aid of

catgut Catgut (also known as gut) is a type of cord that is prepared from the natural fiber found in the walls of animal intestines. Catgut makers usually use sheep or goat intestines, but occasionally use the intestines of cattle, hogs, horses, mules, ...

and a sharp knife". * Theodore Roosevelt "Hound Dog" Taylor, Chicago-based American blues guitarist, was born with polydactyly on both hands, although around age 41, he removed the extra finger on his right hand. * Varalakshmi V, a girl from

Bangalore Bengaluru, also known as Bangalore (List of renamed places in India#Karnataka, its official name until 1 November 2014), is the Capital city, capital and largest city of the southern States and union territories of India, Indian state of Kar ...

with eight fingers on each hand and about four to five extra toes on each foot. *

Volcacius Sedigitus Volcacius Sedigitus () (alternative spelling Volcatius) was the ''titulus'' of a Roman literary critic who flourished around 100 , noted for his ranking of those he considered the best Latin comics. Nothing is known about Sedigitus beyond that Pli ...

, a Roman poet of the 1st century, probably received his epithet, signifying "Sixfinger", because he was born with six fingers on each hand, according to Pliny.''

Natural History Natural history is a domain of inquiry involving organisms, including animals, fungi, and plants, in their natural environment, leaning more towards observational than experimental methods of study. A person who studies natural history is cal ...

'', by

Pliny the Elder Gaius Plinius Secundus (AD 23/24 79), known in English as Pliny the Elder ( ), was a Roman Empire, Roman author, Natural history, naturalist, and naval and army commander of the early Roman Empire, and a friend of the Roman emperor, emperor Vesp ...

; volume 2, p.214. * Zhu Yunming, a Chinese calligrapher, had six fingers on his right hand. * Reggy B, a drag queen and contestant on the second season of Drag Race Holland, revealed on the show that she was born with an extra thumb on her left hand, three extra toes on one foot, and two extra toes on her other foot. Her extra fingers and toes were surgically removed at a young age.

Fictional people

* In '' The Silence of the Lambs'',

Hannibal Lecter Dr. Hannibal Lecter is a character created by American novelist Thomas Harris. Lecter is a cannibalistic serial killer and former forensic psychiatrist; after his incarceration, he is consulted by FBI agents Will Graham and Clarice Starling ...

is described as having mid-ray duplication polydactyly (a duplicated middle finger) on his left hand, which he later removes in ''

Hannibal Hannibal (; ; 247 – between 183 and 181 BC) was a Punic people, Carthaginian general and statesman who commanded the forces of Ancient Carthage, Carthage in their battle against the Roman Republic during the Second Punic War. Hannibal's fat ...

'' as part of his cosmetic surgery to disguise himself. * In the

Disney XD Disney XD is an American pay television television channel, channel owned by the Disney Branded Television and Disney Entertainment units of The Walt Disney Company. The channel is aimed primarily at older children ages six to eleven years old ...

2012 cartoon series ''

Gravity Falls ''Gravity Falls'' is an American Mystery fiction, mystery television comedy, comedy animated television series created by Alex Hirsch for Disney Channel and Disney XD. The series follows the adventures of Dipper Pines (Jason Ritter) and his twi ...

'', Stanford Pines ("Grunkle Ford") has six fingers on both of his hands, a trait which also identifies him in the show's mythology. He uses a tracing of his right hand to create the iconic gold detail on the covers of each of his journals. * Tyrone Rugen, a Count in '' The Princess Bride'', is described many times as "the six-fingered man". * Void, an antagonist of the manga series '' Berserk'', has six fingers on each hand. * Zigzag, an antagonist from '' The Thief and the Cobbler'', had six fingers on each hand. * Billy, a character from ''

Adventure Time ''Adventure Time'' is an American fantasy animated television series created by Pendleton Ward and co-produced by Frederator Studios for Cartoon Network. The series follows the adventures of a boy named Finn the Human, Finn (Jeremy Shada) and ...

'', had six fingers on each hand. * Kinzo Ushiromiya, the head of the Ushiromiya household from the visual novel ''

Umineko When They Cry is a Japanese dōjin soft visual novel series produced by 07th Expansion. Its first episode debuted at Comiket 72 for Windows in August 2007. The story focuses on a group of eighteen people on a secluded island for a period of two days, ...

'', had six toes on each foot. Among the many previous Ushiromiya family heads, those with polydactyly were known for their wisdom. * In ''

For Better or For Worse ''For Better or For Worse'' is a Canadian comic strip by Lynn Johnston that ran originally from 1979 to 2008 chronicling the lives of the Patterson family and their friends, in the town of Milborough, a fictional suburb of Toronto, Ontario. Now ...

'', Leah Nichols was born with 6 fingers on each hand. * In ''

Gattaca ''Gattaca'' is a 1997 American dystopian science fiction film written and directed by Andrew Niccol in his List of directorial debuts, feature directorial debut. It stars Ethan Hawke and Uma Thurman with Jude Law, Loren Dean, Ernest Borgnine, Go ...

'', Ryan Dorin plays a pianist with six fingers on each hand who throws his gloves to the audience at the concert's end.

Other animals

Polydactyly occurs in numerous types of animals. The condition is sporadically seen in livestock, where it affects cattle, sheep, pigs, and occasionally horses. Conversely, it is a common trait in several heritage

chicken breeds There are hundreds of chicken breeds in existence. Domesticated for thousands of years, distinguishable breeds of chicken have been present since the combined factors of geographical isolation and selection for desired characteristics created re ...

. Chickens normally have 4 toes on each foot. The chicken breeds known for being polydactyl are the

Dorking Dorking () is a market town in Surrey in South East England about south-west of London. It is in Mole Valley, Mole Valley District and the non-metropolitan district, council headquarters are to the east of the centre. The High Street runs ro ...

, Faverolle, Houdan, Lincolnshire Buff, Meusienne,

Sultan Sultan (; ', ) is a position with several historical meanings. Originally, it was an Arabic abstract noun meaning "strength", "authority", "rulership", derived from the verbal noun ', meaning "authority" or "power". Later, it came to be use ...

, and non-bearded Silkie Bantams. The breed standard of these varieties of chickens calls for five toes on each foot, although sometimes more than five toes will occur. The extra digit in these breeds presents as an extra "thumb" that does not touch the ground. Mixed-breed chickens may also have extra digits if the aforementioned breeds are part of their genetic makeup. Polydactyly also occurs in dogs, cats, and small mammals such as guinea pigs and mice.

Cat The cat (''Felis catus''), also referred to as the domestic cat or house cat, is a small domesticated carnivorous mammal. It is the only domesticated species of the family Felidae. Advances in archaeology and genetics have shown that the ...

s normally have five digits on the front paws and four on the rear.

Polydactyl cat A polydactyl cat is a cat with a congenital physical anomaly called polydactyly (also known as polydactylism or hyperdactyly), which causes the cat to be born with more than the usual number of toes on one or more of its paws. Cats with this ...

s have more, and this is a moderately common condition, especially in certain cat populations. Dogs, like other

canid Canidae (; from Latin, ''canis'', "dog") is a family (biology), biological family of caniform carnivorans, constituting a clade. A member of this family is also called a canid (). The family includes three subfamily, subfamilies: the Caninae, a ...

s, normally have four claws on their rear paws; a fifth is often called a

dewclaw A dewclaw is a digit – vestigial in some animals – on the foot of many mammals, birds, and reptiles (including some extinct orders, like certain theropods). It commonly grows higher on the leg than the rest of the foot, such that in di ...

and is especially found in certain dog breeds, including the Norwegian Lundehund and Great Pyrenees. A number of mutations of the

LMBR1 Limb region 1 protein homolog is a protein that in humans is encoded by the ''LMBR1'' gene. This gene encodes a member of the LMBR1-like membrane protein family. Another member of this protein family has been shown to be a lipocalin transmembran ...

gene, in dogs, humans, and mice, can cause polydactyly. A 2014 report indicated that mice could also exhibit polydactyly arising from mutation in the VPS25 gene. In cattle, it appears to be

polygenic A polygene is a member of a group of non- epistatic genes that interact additively to influence a phenotypic trait, thus contributing to multiple-gene inheritance (polygenic inheritance, multigenic inheritance, quantitative inheritance), a type ...

with a dominant gene at one locus and a

homozygous Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism. Mos ...

recessive at another. Polydactyly is believed to have been common in early

tetrapods A tetrapod (; from Ancient Greek τετρα- ''(tetra-)'' 'four' and πούς ''(poús)'' 'foot') is any four- limbed vertebrate animal of the clade Tetrapoda (). Tetrapods include all extant and extinct amphibians and amniotes, with the lat ...

, particularly the extinct amphibians that represented the earliest landliving vertebrates. Their number of toes fluctuated until the early

Carboniferous period The Carboniferous ( ) is a geologic period and system of the Paleozoic era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the Permian Period, Ma. It is the fifth and penultimate perio ...

when they finally began developing a uniform number of toes.

Amniotes Amniotes are tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial and semiaquatic vertebrates. Amniotes evolved from amphibious stem tetrapod ancestors during the ...

settled on five toes per limb, while

amphibians Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...

developed four toes on each front limb and five toes on each back limb. (For more information, see

Polydactyly in early tetrapods Polydactyly in stem-tetrapods should here be understood as having more than five digits to the finger or foot, a condition that was the natural state of affairs in the earliest stegocephalians during the evolution of terrestriality. The polydacty ...

). Polydactyly also occurs in modern

extant Extant or Least-concern species, least concern is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Exta ...

reptiles and amphibians. Polydactyly was a non-pathological, reacquired condition in extinct

marine reptile Marine reptiles are reptiles which have become secondarily adapted for an aquatic or semiaquatic life in a marine environment. Only about 100 of the 12,000 extant reptile species and subspecies are classed as marine reptiles, including mari ...

s such as

ichthyosaur Ichthyosauria is an order of large extinct marine reptiles sometimes referred to as "ichthyosaurs", although the term is also used for wider clades in which the order resides. Ichthyosaurians thrived during much of the Mesozoic era; based on fo ...

s and hupehsuchians, some of which containing upwards of ten digits within their flippers. File:The five toed cock of Aldrovandi.jpg, Rooster with feathered legs (Aldrovandi himself did not notice the five toes)Ornithologiae, Ulisse Aldrovandi (ill. Cristoforo Coriolano), 1599 File:The multiple toes of a polydactyl kitten.jpg, Kitten with 23 toes File:Cairina moschata subspecies foot.jpg, Muscovy duck, both feet have five toes File:Cairina moschata subspecies 0.jpg, Muscovy duck, both feet have five toes

References

External links

{{Congenital malformations and deformations of musculoskeletal system Autosomal dominant disorders Congenital disorders of musculoskeletal system Fingers Supernumerary body parts