There are multiple classifications for the triphalangeal thumb. The reason for these different classifications is the heterogeneity in appearance of the TPT.

The classification according to Wood describes the shape of the extra phalanx: delta (Fig. 4), rectangular or full phalanx (Table 1). With the classification made by Buck-Gramcko a surgical treatment can be chosen (Table 1). Buck-Gramcko differentiates between six different shapes of the extra phalanx and associated malformations.

Table 1: Classifications of Wood and Buck-Gramcko

The goals of surgical treatment are: reducing length of the thumb, creating a good functioning, a stable and non deviated joint and improving the position of the thumb if necessary. Hereby improving function of the hand and thumb.

In general the surgical treatment is done for improvement of the thumb function. However, an extra advantage of the surgery is the improvement in appearance of the thumb. In the past, surgical treatment of the triphalangeal thumb was not indicated, but now it is generally agreed that operative treatment improves function and appearance. Because an operation was not indicated in the past, there’s still a population with an untreated triphalangeal thumb. The majority of this population doesn’t want surgery, because the daily functioning of the hand is good. The main obstacle for the untreated patients might not be the diminished function, but the appearance of the triphalangeal thumb.

The timing of surgery differs between Wood and Buck-Gramcko. Wood advises operation between the age of six months and two years, while Buck-Gramcko advises to operate for all indications before the age of six years.

- For TPT types I and II of the Buck-Gramcko classification, the surgical treatment typically consists of removing the extra phalanx and reconstructing the ulnar collateral ligament and the radial collateral ligament if necessary.

- For type III of Buck-Gramcko classification proposable surgical treatments:

- For type IV of Buck-Gramcko classification the surgical treatment typically consists of an osteotomy which reduces the middle phalanx and arthrodesis of the DIP. This gives a shortening of 1 to 1.5 cm. In most cases, this technique is combined with a shortening, rotation and palmar abduction osteotomy at metacarpal level to correct for position and length of the thumb. The extensor tendons and the intrinsic muscles are shortened as well.

- For type V of the Buck-Gramcko classification the surgical treatment proposably consists of a "pollicization". With a pollicization the malpositioned thumb is repositioned, rotated and shortened, the above-described rotation reduction osteotomy of the first metacarpal can be performed as well.

- For type VI of the Buck-Gramcko classification, the surgical treatment typically consists of removing the additional mostly hypoplastic thumb(s). Further procedures of reconstruction of the triphalangeal thumb are performed according to the shape of the extra phalanx as described above.

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

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.

Diagnosis of clubfoot deformity is by physical examination. Typically, a newborn is examined shortly after delivery with a head to toe assessment. Examination of the lower extremity and foot reveals the deformity, which may affect one or both feet. Examination of the foot shows four components of deformity.

- First, there is a higher arch on the inside of the foot. This component of the deformity can occur without the other aspects of clubfoot deformity. In isolation, this aspect of the deformity is called cavus deformity.

- Second, the forefoot is curved inward or medially (toward the big toe). This component of the deformity can occur without the other aspects of clubfoot deformity. In isolation, this aspect of the deformity is called metatarsus adductus.

- Third, the heel is turned inward. This is a natural motion of the heel and subtalar joint, typically referred to as inversion. In clubfoot deformity, the turning in (inversion) of the heel is fixed (not passively correctable) and considered a varus deformity.

- Fourth, and finally, the ankle is pointed downward. This is a natural motion of the ankle referred to as plantar flexion. In clubfoot deformity, this position is fixed (not correctable) and is referred to as equinus deformity.

A foot that shows all four components are diagnosed as having clubfoot deformity. These four components of a clubfoot deformity can be remembered with the acronym CAVE (cavus, forefoot adductus, varus, and equinus).

The severity of the deformity can also be assessed on physical exam, but is subjective to quantify. One way to assess severity is based on the stiffness of the deformity or how much it can be corrected with manual manipulation of the foot to bring it into a corrected position. Other factors used to assess severity include the presence of skin creases in the arch and at the heel and poor muscle consistency.

In some cases, it may be possible to detect the disease prior to birth during a prenatal ultrasound. Prenatal diagnosis by ultrasound can allow parents the opportunity to get information about this condition and make plans for treatment after their baby is born.

Other testing and imaging is typically not needed. Further testing may be needed if there are concerns for other associated conditions.

There are several classifications for cleft hand, but the most used classification is described by Manske and Halikis see table 3. This classification is based on the first web space. The first web space is the space between the thumb and the index.

Table 3: Classification for cleft hand described by Manske and Halikis

When surgery is indicated, the choice of treatment is based on the classification. Table 4 shows the treatment of cleft hand divided into the classification of Manske and Halikis.

Techniques described by Ueba, Miura and Komada and the procedure of Snow-Littler are guidelines; since clinical and anatomical presentation within the types differ, the actual treatment is based on the individual abnormality.

Table 4: Treatment based on the classification of Manske and Halikis

Type II should be managed conservatively whereas type I and Ia requires to be treated surgically. Surgery involves four major steps:

- Development of the calcaneal part of the foot

- Repositioning of the navicular bone

- New adjustment of the ankle, and

- Various stabilization measures including the Grice operation and transposition of various tendons.

Oligodactyly (from the Ancient Greek "oligos" meaning "few" and δάκτυλος "daktylos" meaning "finger") is the presence of fewer than five fingers or toes on a hand or foot.

It is quite often incorrectly called "hypodactyly", but the Greek prefixes and are used for scales (e.g. in hypoglycaemia and hypercholesterolemia). This as opposed to or scales, where and should be used (e.g. in oligarchy and polygamy). Oligodactyly is therefore the opposite of polydactyly. Very rare, this medical condition usually has a genetic or familial cause.

Oligodactyly is sometimes a sign or symptom of several syndromes including Poland syndrome and Weyer Ulnar Ray Syndrome. It is a type of Dysmelia.

Ectrodactyly is an extreme instance of oligodactyly, involving the 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 are often described as "claw-like" and may include only the thumb and one finger (usually either the little finger, ring finger, or a syndactyly of the two) with similar abnormalities of the feet.

People with oligodactyly often have full use of the remaining digits and adapt well to their condition. They are not greatly hindered in their daily activities, if at all. Even those with the most extreme forms are known to engage in tasks that require fine control, such as writing and bootmaking as well as working as a cab driver.

Vadoma people of Zimbabwe have a high frequency of oligodactyly.

The main diagnostic tools for evaluating FND are X-rays and CT-scans of the skull. These tools could display any possible intracranial pathology in FND. For example, CT can be used to reveal widening of nasal bones. Diagnostics are mainly used before reconstructive surgery, for proper planning and preparation.

Prenatally, various features of FND (such as hypertelorism) can be recognized using ultrasound techniques. However, only three cases of FND have been diagnosed based on a prenatal ultrasound.

Other conditions may also show symptoms of FND. For example, there are other syndromes that also represent with hypertelorism. Furthermore, disorders like an intracranial cyst can affect the frontonasal region, which can lead to symptoms similar to FND. Therefore, other options should always be considered in the differential diagnosis.

Initial diagnosis often is made during routine physical examination. Such diagnosis can be confirmed by a medical professional such as a neurologist, orthopedic surgeon or neurosurgeon. A person with foot drop will have difficulty walking on his or her heels because he will be unable to lift the front of the foot (balls and toes) off the ground. Therefore, a simple test of asking the patient to dorsiflex may determine diagnosis of the problem. This is measured on a 0-5 scale that observes mobility. The lowest point, 0, will determine complete paralysis and the highest point, 5, will determine complete mobility.

There are other tests that may help determine the underlying etiology for this diagnosis. Such tests may include MRI, MRN, or EMG to assess the surrounding areas of damaged nerves and the damaged nerves themselves, respectively. The nerve that communicates to the muscles that lift the foot is the peroneal nerve. This nerve innervates the anterior muscles of the leg that are used during dorsi flexion of the ankle. The muscles that are used in plantar flexion are innervated by the tibial nerve and often develop tightness in the presence of foot drop. The muscles that keep the ankle from supination (as from an ankle sprain) are also innervated by the peroneal nerve, and it is not uncommon to find weakness in this area as well. Paraesthesia in the lower leg, particularly on the top of the foot and ankle, also can accompany foot drop, although it is not in all instances.

A common yoga kneeling exercise, the Varjrasana has, under the name "yoga foot drop," been linked to foot drop.

Treatment is usually with some combination of the Ponseti or French methods. The Ponseti method includes the following: casting together with manipulation, cutting the Achilles tendon, and bracing. The Ponseti method has been found to be effective in correcting the problem in those under the age of two. The French method involves realignment and tapping of the foot is often effective but requires a lot of effort by caregivers. Another technique known as Kite does not appear as good. In about 20% of cases further surgery is required.

Diplopodia is a congenital anomaly in tetrapods that involves duplication of elements of the foot on the hind limb. It comes from the Greek roots diplo = "double" and pod = "foot". Diplopodia is often found in conjunction with other structural abnormalities and can be lethal. It is more extreme than polydactyly, the presence of extra digits.

Dysmelia (from Gr. δυσ- "dys", "bad" + μέλ|ος "mél|os", "limb" + Eng. suff. -ia) is a congenital disorder of a limb resulting from a disturbance in embryonic development.

A squitten is a cat with unusually short forelegs and/or unusually long hind legs that resembles a squirrel. It is an example of a cat body type genetic mutation. The word is a portmanteau of squirrel and kitten.

The term kangaroo cat is also, rarely, used; this derives from a 1953 specimen known as the Stalingrad Kangaroo Cat.

Dysmelia can refer to

- missing (aplasia) limbs: amelia, oligodactyly, congenital amputation e.g. Tibial or Radial aplasia

- malformation of limbs: shortening (micromelia, rhizomelia or mesomelia), ectrodactyly, phocomelia, meromelia, syndactyly, brachydactyly, club foot

- too many limbs: polymelia, polydactyly, polysyndactyly

- others: Tetraamelia, hemimelia, Symbrachydactyly

Synpolydactyly is a joint presentation of syndactyly (fusion of digits) and polydactyly (production of supernumerary digits). This is often a result of a mutation in the HOX D13 gene.

Types include:

Rocker bottom foot, also known as congenital vertical talus, is an anomaly of the foot. It is characterized by a prominent calcaneus (heel bone) and a convex rounded bottom of the foot. It gets its name from the foot's resemblance to the bottom of a rocking chair.

It can be associated with Edwards' syndrome (trisomy 18), Patau syndrome (trisomy 13), Trisomy 9 and mutation in the gene HOXD10.

It can also be associated with Charcots foot.

There are few good estimates of prevalence for pes cavus in the general community. While pes cavus has been reported in between 2 and 29% of the adult population, there are several limitations of the prevalence data reported in these studies. Population-based studies suggest the prevalence of the cavus foot is approximately 10%.

The term squitten is generally used to refer to cats with the condition radial hypoplasia (underdeveloped radius bones) or foreleg micromelia (small forelegs) and related conditions known as radial aplasia (absent radius bones), radial agenesis (failure of radius bones to form) that produces stunted forelegs. The mutation sometimes occurs in the random-breeding population, particularly in inbred populations where recessive genes may be exhibited. Such cats have also been called twisty cats; In the late 1990s, several were deliberately bred at Karma Farms, a horse farm and cattery in Marshall, Texas, resulting in a public outcry against the operators of the farm.

Radial hypoplasia is related to one form of polydactyly, sometimes called patty feet or hamburger feet by cat lovers to distinguish them from thumb cat polydactyls. Ordinary mitten cat polydactyls are not affected.

Cats with radial hypoplasia or similar mutations often sit on their rump with their forelegs unable to touch the floor; this gives them a resemblance to a squirrel or kangaroo. This raises special care considerations for owners of affected cats. Kittens may be unable to knead effectively with their short forelegs; kneading is required to stimulate milk flow in the mother. The short or twisted forelegs cause mobility problems and such cats may adapt by using their hindlegs in a hopping gait.

A corresponding condition affecting the hind legs is called femoral hypoplasia and has only been reported three times in cats.

Typical characteristics of a squitten are short forelegs, with a short radius and ulna which may be twisted or absent, extra front toes, and normal-length hind legs.

Congenital limb deformities are congenital musculoskeletal disorders which primarily affect the upper and lower limbs.

An example is polydactyly.

The Wassel classification is used to categorise radial polydactyly, based upon the most proximal level of skeletal duplication.

Evaluations by certain specialists should be performed following the initial diagnosis of Duane-radial ray syndrome. These evaluations will be used to determine the extent of the disease as well as the needs of the individual.

- Eyes - Complete eye exam by an ophthalmologist especially focusing on the extraocular movements of the eye and the structural eye defects

- Heart - evaluation by a cardiologist along with an echocardiogram and ECG

- Kidneys - Laboratory tests to check kidney function and a renal ultrasound

- Hearing

- Endocrine - evaluation for growth hormone deficit if growth retardation present

- Blood - CBC to check for thrombocytopenia and leukocytosis

- Clinical genetics consultation

Although the origin of the disease is unknown, there is speculation that it is an aggressive healing response to small tears in the plantar fascia, almost as if the fascia over-repairs itself following an injury. There is also some evidence that it might be genetic.

In the early stages, when the nodule is single and/or smaller, it is recommended to avoid direct pressure to the nodule(s). Soft inner soles on footwear and padding may be helpful.

MRI and sonogram (diagnostic ultrasound) are effective in showing the extent of the lesion, but cannot reveal the tissue composition. Even then, recognition of the imaging characteristics of plantar fibromatoses can help in the clinical diagnosis.

Surgery of Ledderhose's disease is difficult because tendons, nerves, and muscles are located very closely to each other. Additionally, feet have to carry heavy load, and surgery might have unpleasant side effects. If surgery is performed, the biopsy is predominantly cellular and frequently misdiagnosed as fibrosarcoma. Since the diseased area (lesion) is not encapsulated, clinical margins are difficult to define. As such, portions of the diseased tissue may be left in the foot after surgery. Inadequate excision is the leading cause of recurrence.

Radiotherapy has been shown to reduce the size of the nodules and reduce the pain associated with them. It is approximately 80% effective, with minimal side-effects.

Post-surgical radiation treatment may decrease recurrence. There has also been variable success in preventing recurrence by administering gadolinium. Skin grafts have been shown to control recurrence of the disease.

In few cases shock waves also have been reported to at least reduce pain and enable walking again. Currently in the process of FDA approval is the injection of collagenase. Recently successful treatment of Ledderhose with cryosurgery (also called cryotherapy) has been reported.

Cortisone injections, such as Triamcinolone, and clobetasol ointments have been shown to stall the progression of the disease temporarily, although the results are subjective and large-scale studies far from complete. Injections of superoxide dismutase have proven to be unsuccessful in curing the disease while radiotherapy has been used successfully on Ledderhose nodules.

MRI imaging can be used to detect whether the abducens nerve is present.