There is no consensus on what degree of angulation justifies a diagnosis, an incline between 15° and 30° is typical. A similar-sounding term, camptodactyly, is a fixed flexion deformity of a digit.

Three main points in diagnosing thumb hypoplasia are: width of the first web space, instability of the involved joints and function of the thumb. Thorough physical examination together with anatomic verification at operation reveals all the anomalies. An X-ray of the hand and thumb in two directions is always mandatory. When the pediatrician thinks the condition is associated with some kind of syndrome other tests will be done. More subtle manifestations of types I and II may not be recognized, especially when more obvious manifestations of longitudinal radial deficiency in the opposite extremity are present. Therefore, a careful examination of both hands is important.

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

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

When it comes to treatment it is important to differentiate a thumb that needs stability, more web width and function, or a thumb that needs to be replaced by the index finger. Severe thumb hypoplasia is best treated by pollicization of the index finger. Less severe thumb hypoplasia can be reconstructed by first web space release, ligament reconstruction and muscle or tendon transfer.

It has been recommended that pollicization is performed before 12 months, but a long-term study of pollicizations performed between the age of 9 months and 16 years showed no differences in function related to age at operation.

It is important to know that every reconstruction of the thumb never gives a normal thumb, because there is always a decline of function. When a child has a good index finger, wrist and fore-arm the maximum strength of the thumb will be 50% after surgery in comparison with a normal thumb. The less developed the index finger, wrist and fore-arm is, the less strength the reconstructed thumb will have after surgery.

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

Surgical treatment of the cleft hand is based on several indications:

Improving function

- Absent thumb

- Deforming syndactyly (mostly between digits of unequal length like index and thumb)

- Transverse bones (this will progress the deformity; growth of these bones will widen the cleft)

- Narrowed first webspace

- The feet

Aesthetical aspects

- Reducing deformity

Syndactyly of the border digits (thumb/index finger or ring/small fingers) is treated at early age to prevent the larger digit from curving towards the smaller digit with growth. Typically, syndactyly of these digits is treated at six months of age. The treatment of syndactyly of the other digits is elective and is more commonly performed when the digits have grown, at 18–24 months of age.

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

Due to a developmental arrest there is an abnormal alignment of the joint surfaces at either interphalangeal joint causing angulation in the plane of the palm. The finger may be slightly bent or have a very prominent bend.

There is no standard treatment for the hand malformations in Apert due to the differences and severity in clinical manifestations in different patients. Every patient should therefore be individually approached and treated, aiming at an adequate balance between hand functionality and aesthetics.

However, some guidelines can be given depending on the severity of the deformities.

In general it is initially recommended to release the first and fourth interdigital spaces, thus releasing the border rays.

This makes it possible for the child to grasp things by hand, a very important function for the child's development. Later the second and third interdigital spaces have to be released.

Because there are three handtypes in Apert, all with their own deformities, they all need a different approach regarding their treatment:

- Type I hand usually needs only the interdigital web space release. First web release is rarely needed but often its deepening is necessary. Thumb clynodactyly correction will be needed.

- In type II hands it is recommended to release the first and fifth rays in the beginning, then the second and the third interdigital web spaces have to be freed. The clynodactyly of the thumb has to be corrected as well. The lengthening of the thumb phalanx may be needed, thus increasing the first web space. In both type I and type II, the recurrent syndactyly of the second web space will occur because of a pseudoepiphysis at the base of the index metacarpal. This should be corrected by later revisions.

- Type III hands are the most challenging to treat because of their complexity. First of all, it is advised to release the first and fourth webspace, thus converting it to type I hand. The treatment of macerations and nail-bed infections should also be done in the beginning. For increasing of the first web space, lengthening of the thumb can be done. It is suggested that in severe cases an amputation of the index finger should be considered. However, before making this decision, it is important to weigh the potential improvement to be achieved against the possible psychological problems of the child later due to the aesthetics of the hand. Later, the second and/or third interdigital web space should be released.

With growing of a child and respectively the hands, secondary revisions are needed to treat the contractures and to improve the aesthetics.

There are a few different classifications conceived to categorize the spectrum of variety of congenital clasped thumb. In literature X classifications have been described for clasped thumb. The two most relevant of the existing classifications, to our opinion, are the classifications of McCarrol and Tjuyuguchi et al.

The most global format is the classification of McCarrol, which divides the congenital clasped thumbs into two groups. Group I includes the supple clasped thumb, when the thumb is only passively correctable. While complex clasped thumbs, thumbs which cannot be moved neither passively or actively, belong to group II.

Tjuyuguchi et al. designed a classification existing of three groups:

- Group I: The supple clasped thumb, where the thumb is passively abductable and extendable against the resistance of thumb flexors, without other digital anomalies.

- Group II: The clasped thumb with hand contractures, where the thumb is not passively extendable and abductable, with or without other digital anomalies.

- Group III: The clasped thumb which is associated with arthrogryposis.

There is no cure for this condition. Treatment is supportive and varies depending on how symptoms present and their severity. Some degree of developmental delay is expected in almost all cases of M-CM, so evaluation for early intervention or special education programs is appropriate. Rare cases have been reported with no discernible delay in academic or school abilities.

Physical therapy and orthopedic bracing can help young children with gross motor development. Occupational therapy or speech therapy may also assist with developmental delays. Attention from an orthopedic surgeon may be required for leg length discrepancy due to hemihyperplasia.

Children with hemihyperplasia are thought to have an elevated risk for certain types of cancers. Recently published management guidelines recommend regular abdominal ultrasounds up to age eight to detect Wilms' tumor. AFP testing to detect liver cancer is not recommended as there have been no reported cases of hepatoblastoma in M-CM patients.

Congenital abnormalities in the brain and progressive brain overgrowth can result in a variety of neurological problems that may require intervention. These include hydrocephalus, cerebellar tonsillar herniation (Chiari I), seizures and syringomyelia. These complications are not usually congenital, they develop over time often presenting complications in late infancy or early childhood, though they can become problems even later. Baseline brain and spinal cord MRI imaging with repeat scans at regular intervals is often prescribed to monitor the changes that result from progressive brain overgrowth.

Assessment of cardiac health with echocardiogram and EKG may be prescribed and arrhythmias or abnormalities may require surgical treatment.

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

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.

Because the circumference of the conjoined fingers is smaller than the circumference of the two separated fingers, there is not enough skin to cover both digits once they are separated at the time of surgery. Therefore, the surgeon must bring new skin into the area at the time of surgery. This is most commonly done with a skin graft (from groin or anterior elbow). Skin can also be used from the back of the hand by mobilizing it (called a "graftless" syndactyly correction), which requires planning over a period of months prior to surgery.

Three main support groups of this syndrome are the ASGA in Australia, The Association for Children with Genetic Disorders in Poland, and the Association of People of Genetic Disorders in Greece.

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.

Omphalocele has been described in two patients with Apert syndrome by Herman T.E. et al. (USA, 2010) and by Ercoli G. et al. (Argentina, 2014). An omphalocele is a birth defect in which an intestine or other abdominal organs are outside of the body of an infant because of a hole in the bellybutton area. However, the association between omphalocele and Apert syndrome is not confirmed yet, so additional studies are necessary.

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:

The inheritance of Impossible syndrome is suspected to be autosomal recessive, which means the affected gene is located on an autosome, and two copies of the gene - one from each parent - are required to have an infant with the disorder.

There is no causative / curative therapy. Symptomatic medical treatments are focussing on symptoms caused by orthopaedic, dental or cardiac problems. Regarding perioperative / anesthesiological management, recommendations for medical professionals are published at OrphanAnesthesia.

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

Treatment of congenital clasped thumb includes two types of therapy: conservative and surgical.