Polydactyly or polydactylism (), also known as hyperdactyly, is an anomaly in
human
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
s and animals resulting in
supernumerary
Supernumerary means "exceeding the usual number".
Supernumerary may also refer to:
* Supernumerary actor, a performer in a film, television show, or stage production who has no role or purpose other than to appear in the background, more commonl ...
fingers and/or toes.
Polydactyly is the opposite of
oligodactyly
Oligodactyly (from Ancient Greek ''oligos'' 'few' and δάκτυλος ''daktylos'' 'finger') is the presence of fewer than five fingers or toes on a hand or foot. (fewer fingers or toes).
Signs and symptoms
![Polydactyly](https://upload.wikimedia.org/wikipedia/commons/a/ab/Polydactyly.jpg)
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 (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...
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, a directional coordinate in a polar coordinate system
* Radial set
* A bearing f ...
(
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.
The incidence of congenital deformities in newborns is approximately 2%, and 10% of these deformities involve the upper extremity.
Congenital anomalies of the limb can be classified in seven categories, proposed by Frantz and O’Rahilly and modified by Swanson, 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.
Polydactyly belongs to the category of duplication.
Because there is an association between polydactyly and several syndromes, children with a congenital upper extremity deformity should be examined by a geneticist 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.
Research has shown that the majority of congenital anomalies occur during the 4-week embryologic period of rapid limb development.
Polydactyly has been associated with 39 genetic mutations.
More specific loci and genetic mechanisms responsible for disorders of duplications will be defined with time, as molecular research continues.
Polydactyly can be divided into three major types, which are discussed below, which depend on the location of the additional digit.
Research conducted by the
University of Freiburg
The University of Freiburg (colloquially german: Uni Freiburg), officially the Albert Ludwig University of Freiburg (german: Albert-Ludwigs-Universität Freiburg), is a public university, public research university located in Freiburg im Breisg ...
,
Imperial College London
Imperial College London (legally Imperial College of Science, Technology and Medicine) is a public research university in London, United Kingdom. Its history began with Prince Albert, consort of Queen Victoria, who developed his vision for a cu ...
,
Lausanne University Hospital
The Lausanne University Hospital (french: Centre hospitalier universitaire vaudois, CHUV), in Lausanne, is one of the five university hospitals in Switzerland.
The Lausanne University Hospital is linked to the Faculty of Biology and Medicine of ...
and
EPFL as a case study in ''
Nature Communications
''Nature Communications'' is a peer-reviewed, open access, scientific journal published by Nature Portfolio since 2010. It is a multidisciplinary journal and it covers the natural sciences, including physics, chemistry, earth sciences, medici ...
'' in 2019 found that in cases of polydactyly that result in 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.
Ulnar or postaxial polydactyly
![Polydactyly postaxial](https://upload.wikimedia.org/wikipedia/commons/e/e6/Polydactyly_postaxial.gif)
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 ( grc, φάλαγξ; plural phalanxes or phalanges, , ) was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar pole weapons. The term is particularly use ...
with a
nail
Nail or Nails may refer to:
In biology
* Nail (anatomy), toughened protective protein-keratin (known as alpha-keratin, also found in hair) at the end of an animal digit, such as fingernail
* Nail (beak), a plate of hard horny tissue at the tip ...
, 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 and African Americans. 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 polydactyly
![Polydactyly preaxial](https://upload.wikimedia.org/wikipedia/commons/6/64/Polydactyly_preaxial.gif)
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 polydactyly
This is a very rare situation, 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, cleft hand and several syndromes.
Polysyndactyly presents various degrees of syndactyly affecting fingers three and four.
Causes
![Shh ectopic expression](https://upload.wikimedia.org/wikipedia/commons/f/f3/Shh_ectopic_expression.gif)
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 morphoge ...
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, a combination of extra and consolidated digits. Other signal transduction pathways in this context are the
Wnt signaling pathway
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 is a portmanteau created from the names Wingless and Int-1. Wnt signaling p ...
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. Ev ...
(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.
In addition to the study of genetic causes of polydactyly, limb patterning models are used to simulate the
congenital disorder
A birth defect, also known as a congenital disorder, 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 ...
at the limb, being able to explain the development paths of polydactyly.
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 σύνδρομον, meaning "concurrence". When a syndrome is paired ...
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 effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and t ...
mutations in single genes, i.e. it is not a
multifactorial trait
A quantitative trait locus (QTL) is a locus (section of DNA) that correlates with variation of a quantitative trait in the phenotype of a population of organisms. QTLs are mapped by identifying which molecular markers (such as SNPs or AFLPs) ...
. 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, however, with a recent study showing a relationship to maternal pollution exposure in China.
Types include:
97 genetic syndromes have been associated with different kinds of polydactyly.
Ulnar polydactyly
Ulnar polydactyly is often bilateral and associated with
syndactyly
Syndactyly is a condition wherein two or more digits are fused together. It occurs normally in some mammals, such as the siamang and diprotodontia, but is an unusual condition in humans. The term is from Greek σύν, ''syn'' 'together' and δάκ ...
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. The syndromes which occur with ulnar polydactyly are:
Trisomy 13
A trisomy is a type of polysomy in which there are three instances of a particular chromosome, instead of the normal two. A trisomy is a type of aneuploidy (an abnormal number of chromosomes).
Description and causes
Most organisms that reprodu ...
,
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
* Phi ...
,
Ellis–van Creveld syndrome,
McKusick–Kaufman syndrome
McKusick–Kaufman syndrome is a genetic condition associated with MKKS.
The condition is named for Dr. Robert L. Kaufman and Victor McKusick. It is sometimes known by the abbreviation MKS. In infancy it can be difficult to distinguish between MK ...
,
Down syndrome
Down syndrome or Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is usually associated with physical growth delays, mild to moderate intellectual dis ...
,
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 som ...
,
Smith–Lemli–Opitz syndrome
Smith–Lemli–Opitz syndrome is an inborn error of cholesterol synthesis. It is an autosomal recessive, multiple malformation syndrome caused by a mutation in the enzyme 7-Dehydrocholesterol reductase encoded by the DHCR7 gene. It causes a bro ...
.
Radial polydactyly
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 (the u ...
,
Fanconi anemia
Fanconi anaemia (FA) is a rare genetic disease resulting in impaired response to DNA damage. Although it is a very rare disorder, study of this and other bone marrow failure syndromes has improved scientific understanding of the mechanisms of nor ...
(aplastic anemia by the age of 6),
Townes–Brocks syndrome
Townes–Brocks syndrome (TBS) is a rare genetic disease that has been described in approximately 200 cases in the published literature. It affects both males and females equally. , and
Greig cephalopolysyndactyly
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 ...
(also known to occur with ulnar polydactyly).
Central polydactyly
The syndromes associated with central polydactyly are:
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 som ...
,
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
* Phi ...
,
Pallister–Hall syndrome
Pallister–Hall syndrome (abbreviated PHS) is a disorder that affects the development of many parts of the body.
It is named for Judith Goslin Hall, Judith Hall and Philip Pallister.
Presentation
Most people with this condition have extra fing ...
,
Legius syndrome
Legius syndrome (LS) is an autosomal dominant condition characterized by cafe au lait spots.["Legius syndrome ...](_blank)
,
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 (the u ...
.
Also, central polydactyly can be associated with
syndactyly
Syndactyly is a condition wherein two or more digits are fused together. It occurs normally in some mammals, such as the siamang and diprotodontia, but is an unusual condition in humans. The term is from Greek σύν, ''syn'' 'together' and δάκ ...
and
cleft hand.
Other syndromes including polydactyly include
acrocallosal syndrome
Acrocallosal syndrome (also known as ACLS) is an extremely rare autosomal recessive syndrome characterized by corpus callosum agenesis, polydactyly, multiple dysmorphic features, motor and intellectual disabilities, and other symptoms. The syndr ...
,
basal cell nevus syndrome,
Biemond syndrome
Biemond syndrome is a genetic disorder characterised by brachydactyly, nystagmus, strabismus, cerebellar ataxia and intellectual disability.
Signs and symptoms
The family described by Biemond had a few members across four generations who had b ...
,
ectrodactyly-ectodermal dysplasias-cleft lip/palate syndrome,
mirror hand deformity,
Mohr syndrome
Orofaciodigital syndrome or oral-facial-digital syndrome is a group of at least 13 related conditions that affect the development of the mouth, facial features, and digits in between 1 in 50,000 to 250,000 newborns with the majority of cases bei ...
,
oral-facial-digital syndrome,
Rubinstein-Taybi syndrome,
short rib polydactyly, and
VATER 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 t ...
.
It can also occur with a
triphalangeal thumb
Triphalangeal thumb (TPT) is a congenital malformation where the thumb has three phalanges instead of two. The extra phalangeal bone can vary in size from that of a small pebble to a size comparable to the phalanges in non-thumb digits. The true ...
.
Diagnosis
![X-ray of feet in polydactyly](https://upload.wikimedia.org/wikipedia/commons/f/f5/X-ray_of_feet_in_polydactyly.jpg)
Classification is performed by using x-ray imaging to see the bone structures.
Ulnar polydactyly
![Polydactyly Left Hand](https://upload.wikimedia.org/wikipedia/commons/0/07/Polydactyly_Left_Hand.jpg)
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 polydactyly
The
Wassel classification The Wassel classification is used to categorise radial polydactyly, based upon the most proximal
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from ...
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 polydactyly
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.
Treatment
Ulnar polydactyly
Ulnar polydactyly usually does not interfere with hand function, but for social reasons it can be treated operatively.
![Polydactyly 01 Lfoot AP](https://upload.wikimedia.org/wikipedia/commons/d/d8/Polydactyly_01_Lfoot_AP.jpg)
Type A ulnar polydactyly
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 polydactyly
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
A neuroma (; plural: neuromata or neuromas) is a growth or tumor of nerve tissue. Neuromas tend to be benign (i.e. not cancerous); many nerve tumors, including those that are commonly malignant, are nowadays referred to by other terms.
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. Studies have shown that excision of the extra digit in the neonatal nursery is a safe and simple procedure with a good clinical and cosmetic outcome.
Radial polydactyly
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 polydactyly
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.
Prognosis
Ulnar polydactyly
Type A ulnar polydactyly
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 ulnar polydactyly
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 polydactyly
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 collateral 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 polydactyly
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
![Preaxial polydactyly right hand](https://upload.wikimedia.org/wikipedia/commons/e/ed/Preaxial_polydactyly_right_hand.jpg)
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
(We dare defend our rights)
, anthem = "Alabama (state song), Alabama"
, image_map = Alabama in United States.svg
, seat = Montgomery, Alabama, Montgomery
, LargestCity = Huntsville, Alabama, Huntsville
, LargestCounty = Baldwin County, Al ...
, United States, and
Uppsala County
Uppsala County ( sv, Uppsala län) 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.
Provi ...
, 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 with polydactyly
* Antonio Alfonseca
Antonio Alfonseca (; ; born April 16, 1972) is a Dominican former relief pitcher. He last pitched in Major League Baseball for the Philadelphia Phillies in . Alfonseca also played for the Florida Marlins (–, ), the Chicago Cubs (–), the Atla ...
, retired MLB professional baseball pitcher known as "''El Pulpo''" – Spanish for "the Octopus" with regard to 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 century ...
, 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 fo ...
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 (; see 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 Engli ...
, had six fingers on each hand.
* The actress Gemma Arterton
Gemma Christina Arterton (born 2 February 1986) is an English actress and producer. 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'' ...
was born with six fingers on each hand, the additional fingers being removed after birth.
* Anne Boleyn
Anne Boleyn (; 1501 or 1507 – 19 May 1536) was Queen of England from 1533 to 1536, as the second wife of King Henry VIII. The circumstances of her marriage and of her execution by beheading for treason and other charges made her a key ...
, former Queen of England, was rumoured to have six fingers on one hand. However, considering that this rumour first emerged in the 1580s from a Catholic dissenter, it is generally deemed false.
* 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 tr ...
'', and his brother William had six digits on each limb.
* Lucille Clifton
Lucille Clifton (June 27, 1936 – February 13, 2010) was an American poet, writer, and educator from Buffalo, New York. From 1979 to 1985 she was Poet Laureate of Maryland. Clifton was a finalist twice for the Pulitzer Prize for poetry.
Li ...
, 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.
* Several members of a Da Silva family in São Paulo
São Paulo (, ; Portuguese for 'Saint Paul') is the most populous city in Brazil, and is the capital of the state of São Paulo, the most populous and wealthiest Brazilian state, located in the country's Southeast Region. Listed by the GaWC a ...
, Brazil, have two thumbs on each hand.
* Vicente Fox
Vicente Fox Quesada (; born 2 July 1942) is a Mexican businessman and politician who served as the 62nd president of Mexico from 1 December 2000 to 30 November 2006. After campaigning as a Right-wing populism, right-wing populist, Fox was elec ...
, former President of Mexico, has 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 ...
, 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, with its roots in blues and ragtime. Since the 1920s Jazz Age, it has been recognized as a major ...
pianist
A pianist ( , ) is an individual musician who plays the piano. Since most forms of Western music can make use of the piano, pianists have a wide repertoire and a wide variety of styles to choose from, among them traditional classical music, ja ...
, 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 ( pl, Henryk II Pobożny; 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 ...
, High Duke of Poland 1238–1241, had six toes on his left foot.
* A boy named Hong Hong born in Pingjiang County, Hunan province
Hunan (, ; ) is a landlocked province of the People's Republic of China, part of the South Central China region. Located in the middle reaches of the Yangtze watershed, it borders the province-level divisions of Hubei to the north, Jiangxi t ...
, 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
Brežice (; german: Rann ) is a town in eastern Slovenia in the Lower Sava Valley, near the Croatian border. It is the seat of the Municipality of Brežice. It lies in the center of the Brežice Plain ( sl, Brežiško polje), which is part of the ...
, Slovenia.
* Jiang Qing
Jiang Qing (19 March 191414 May 1991), also known as Madame Mao, was a Chinese communist revolutionary, actress, and major political figure during the Cultural Revolution (1966–1976). She was the fourth wife of Mao Zedong, the Chairman o ...
, Mao Zedong
Mao Zedong pronounced ; also romanised traditionally as Mao Tse-tung. (26 December 1893 – 9 September 1976), also known as Chairman Mao, was a Chinese communist revolutionary who was the founder of the People's Republic of China (PRC) ...
'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 films. 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 six ...
, a Bollywood
Hindi cinema, popularly known as Bollywood and formerly as Bombay cinema, refers to the film industry based in Mumbai, engaged in production of motion pictures in Hindi language. The popular term Bollywood, is a portmanteau of "Bombay" (fo ...
actor born with a supernumerary thumb on his right hand.
* Nayanthara
Diana Mariam Kurian, known professionally as
Nayanthara, is an Indian actress and film producer who is known for her work in Tamil, Telugu and Malayalam films. She was in the ''Forbes India'' "Celebrity 100" 2018 list, with her total annual ...
, an Indian actress who is a polydactyl, with a rudimentary finger on her left hand.
* Akshat Saxena from Uttar Pradesh
Uttar Pradesh (; , 'Northern Province') is a state in northern India. With over 200 million inhabitants, it is the most populated state in India as well as the most populous country subdivision in the world. It was established in 1950 ...
, India
India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
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
Sir Garfield St Aubrun Sobers, (born 28 July 1936), also known as Sir Gary or Sir Garry Sobers, is a former cricketer who played for the West Indies between 1954 and 1974. A highly skilled bowler, an aggressive batsman and an excellent fielder, ...
, West Indian cricket
Cricket is a bat-and-ball game played between two teams of eleven players on a field at the centre of which is a pitch with a wicket at each end, each comprising two bails balanced on three stumps. The batting side scores runs by striki ...
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 Gut (anatomy), intestines. Catgut makers usually use sheep or goat intestines, but occasionally use the intestines of cattle, Domest ...
and a sharp knife".
* Theodore Roosevelt "Hound Dog" Taylor, American Chicago-based 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
Bangalore (), officially Bengaluru (), is the capital and largest city of the Indian state of Karnataka. It has a population of more than and a metropolitan population of around , making it the third most populous city and fifth most ...
with eight fingers on each hand and about four to five extra toes on each foot.
* Volcacius Sedigitus, 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
Pliny may refer to:
People
* Pliny the Elder (23–79 CE), ancient Roman nobleman, scientist, historian, and author of ''Naturalis Historia'' (''Pliny's Natural History'')
* Pliny the Younger (died 113), ancient Roman statesman, orator, w ...
,['' Natural History'', by ]Pliny the Elder
Gaius Plinius Secundus (AD 23/2479), called Pliny the Elder (), was a Roman author, naturalist and natural philosopher, and naval and army commander of the early Roman Empire, and a friend of the emperor Vespasian. He wrote the encyclopedic '' ...
; volume 2, p.214.
* Zhu Yunming
Zhu Yunming (; 1461–1527) was a Chinese calligrapher, poet, writer, and scholar-official of the Ming dynasty, known as one of the "Four Talents of Wu" (Suzhou). Most admired for his accomplishment in calligraphy, he is also a popular cultural ...
, 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.
* (), a biblical Philistean figure who fought against King David
David (; , "beloved one") (traditional spelling), , ''Dāwūd''; grc-koi, Δαυΐδ, Dauíd; la, Davidus, David; gez , ዳዊት, ''Dawit''; xcl, Դաւիթ, ''Dawitʿ''; cu, Давíдъ, ''Davidŭ''; possibly meaning "beloved one". w ...
's army. The Bible mentions he was a relative to Goliath
Goliath ( ) ''Goləyāṯ''; ar, جُليات ''Ǧulyāt'' (Christian term) or (Quranic term). is a character in the Book of Samuel, described as a Philistine giant
In folklore, giants (from Ancient Greek: ''gigas'', cognate giga-) a ...
.
Fictional people
* In '' The Silence of the Lambs'', Hannibal Lecter
Dr. Hannibal Lecter is a Character (arts), fictional character created by the novelist Thomas Harris. Lecter is a serial killer who Human cannibalism, eats his victims. Before his capture, he was a respected Forensic psychiatry, forensic psychi ...
is described as having mid-ray duplication polydactyly (a duplicated middle finger) on his left hand, which he later removes in ''Hannibal
Hannibal (; xpu, 𐤇𐤍𐤁𐤏𐤋, ''Ḥannibaʿl''; 247 – between 183 and 181 BC) was a Carthaginian general and statesman who commanded the forces of Carthage in their battle against the Roman Republic during the Second Puni ...
'' as part of his cosmetic surgery to disguise himself.
* In the cartoon series ''Gravity Falls
''Gravity Falls'' is an American mystery 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 twin sister Mabel (Kristen Schaal) wh ...
'', Stanford Pines ("Grunkle Ford") has six fingers on both of his hands, a trait which also identifies him in the show's mythology.
* Tyrone Rugen, a Count in ''The Princess Bride The Princess Bride may refer to:
* ''The Princess Bride'' (novel), 1973 fantasy romance novel by American writer William Goldman
William Goldman (August 12, 1931 – November 16, 2018) was an American novelist, playwright, and screenwriter. He ...
'', is described many times as the "six-fingered man."
* Void, an antagonist of the manga series '' Berserk'', has six fingers on each hand.
* Billy, a character from ''Adventure Time
''Adventure Time'' is an American fantasy animated television series created by Pendleton Ward for Cartoon Network and distributed by Warner Bros. Domestic Television. The series follows the adventures of a boy named Finn (Jeremy Shada) and ...
'' had six fingers on each hand.
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 Selective breeding, selection for desired characte ...
. 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 of London. It is in Mole Valley District and the council headquarters are to the east of the centre. The High Street runs roughly east–west, parallel to the Pipp Br ...
, Faverolle, Houdan
Houdan () is a commune of the Yvelines department west of Paris in the north of France.
History
The name has evolved from the Saxon "Hoding," meaning "settlement on the hill". Houdan is thought to have been inhabited since the 5th century. B ...
, Lincolnshire Buff, Meusienne, Sultan
Sultan (; ar, سلطان ', ) 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 ...
, 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'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...
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 (or polydactylism, also known as 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 ge ...
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 biological family of dog-like carnivorans, colloquially referred to as dogs, and constitutes a clade. A member of this family is also called a canid (). There are three subfamilies found withi ...
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 digit ...
and is especially found in certain dog breeds, including the Norwegian Lundehund
The Norwegian Lundehund (Norwegian: ''Norsk lundehund'') is a small dog breed of the Spitz type that originates from Norway. Its name is a compound noun composed of the elements ''lunde'', meaning puffin (Norwegian ''lunde'', "puffin", or ''lunde ...
and Great Pyrenees
The Pyrenean Mountain Dog
(french: Chien de Montagne des Pyrénées) is a breed of livestock guardian dog from France, where it is commonly called the Patou. The breed comes from the French side of the Pyrenees Mountains that separate France an ...
.
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 transmembrane ...
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
Vacuolar protein-sorting-associated protein 25 is a protein that in humans is encoded by the ''VPS25'' gene.
It is a component of the endosome-associated protein complex, complex ESCRT-II (Endosomal Sorting Complexes Required for Transport protei ...
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 of ...
with a dominant gene at one locus
Locus (plural loci) is Latin for "place". It may refer to:
Entertainment
* Locus (comics), a Marvel Comics mutant villainess, a member of the Mutant Liberation Front
* ''Locus'' (magazine), science fiction and fantasy magazine
** ''Locus Award' ...
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.
Mo ...
recessive at another.[
Polydactyly was believed to be common in early ]tetrapods
Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids (pelycosaurs, extinct therapsids ...
, the extinct amphibians that represented the earliest landliving vertebrates. Their number of toes fluctuated until the early Carboniferous period
The Carboniferous ( ) is a Period (geology), geologic period and System (stratigraphy), system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago (Myr, Mya), to the beginning of the Permian Period, ...
when they finally began developing a uniform number of toes. Amniotes
Amniotes are a clade of tetrapod vertebrates that comprises sauropsids (including all reptiles and birds, and extinct parareptiles and non-avian dinosaurs) and synapsids (including pelycosaurs and therapsids such as mammals). They are distingu ...
settled on five toes per limb, while amphibians
Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arbore ...
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 very first stegocephalians during the evolution of terrestriality. The polydac ...
). Polydactyly also occurs in modern extant
Extant 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
* Extant taxon, a taxon which is not extinct, ...
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.
The earliest marine reptile mesosaurus (not to be confused with mosasaurus), arose in the Permian period during the ...
s such as ichthyosaur
Ichthyosaurs (Ancient Greek for "fish lizard" – and ) are large extinct marine reptiles. Ichthyosaurs belong to the order known as Ichthyosauria or Ichthyopterygia ('fish flippers' – a designation introduced by Sir Richard Owen in 1842, altho ...
s and hupehsuchia
Hupehsuchia is an order of diapsid reptiles closely related to ichthyosaurs. The group was short-lasting, with a temporal range restricted to the late Olenekian age, spanning only a few million years of the Early Triassic. The order gets its na ...
ns, 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