Triphalangeal thumb (TPT) is a

congenital 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 ...

malformation where the

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 ...

has three

phalanges The phalanges (singular: ''phalanx'' ) are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones. ...

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 incidence of the condition is unknown, but is estimated at 1:25,000 live births.Lapidus PW, Guidotti FP, Coletti CJ, Triphalageal thumb. Surg Gynecol Obstet, 1943 In about two-thirds of the patients with triphalangeal thumbs, there is a hereditary component.Temtamy SA, McKusick VA, the genetics of hand malformations, Birth defects Orig Artic Ser, 1978 Besides the three phalanges, there can also be other malformations. It was first described by Columbi in 1559.H. Kelikian, Hyperphalangism, congenital deformities of the hand and forearm, 1974

Signs and symptoms

The triphalangeal thumb has a different appearance than normal thumbs. The appearance can differ widely; the thumb can be a longer thumb, it can be deviated in the radio-ulnar plane (

clinodactyly Clinodactyly is a medical term describing the curvature of a digit (a finger or toe) in the plane of the palm, most commonly the fifth finger (the "little finger") towards the adjacent fourth finger (the "ring finger"). It is a fairly common iso ...

), or thumb strength can be diminished. In the case of a five-fingered hand it has a finger-like appearance, with the position in the plane of the four fingers,

thenar muscle The thenar eminence is the mound formed at the base of the thumb on the palm of the hand by the muscles of the thumb#Intrinsic, intrinsic group of muscles of the thumb. The skin overlying this region is the area stimulated when trying to elicit ...

deficiency, and additional length. There is often a combination with radial

polydactyly Polydactyly or polydactylism (), also known as hyperdactyly, is an anomaly in humans and animals resulting in supernumerary fingers and/or toes. Polydactyly is the opposite of oligodactyly (fewer fingers or toes). Signs and symptoms In humans ...

Complications

Generally, triphalangeal thumbs are non-opposable. In contrast to most people with

opposable thumbs 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 ...

, a person suffering from TPT cannot easily place his or her thumb opposite the other four digits of the same hand. The opposable thumb's ability to effortlessly utilize fingers in a "pinch" formation is critical in precision gripping. For the thumb to adequately grip, certain thumb criteria must be met (e.g. suitable position and length, stable

joints A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animal's skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiology. 7th ed. McGraw- ...

and good

strength).Zguricas J, Raeymaecker DM, Snijder PJ, Psychomotor development in children with triphalangeal thumbs, J Hand Surg Br Vol, 1998 Because triphalangeal thumbs cannot easily oppose and do not possess many of the optimal qualities found in most opposable thumbs, they tend to cause the hand to be less effective in use and, therefore, prove to be more problematic in daily life.

Cause

Malformations of the upper extremities can occur in the third to seventh embryonic week.Qazi Q, Kassner EG, Triphalangeal thumb, J Med Genet, 1988 In some cases the TPT is hereditary. In these cases, there is a mutation on

chromosome 7 Chromosome 7 is one of the 23 pairs of chromosomes in humans, who normally have two copies of this chromosome. Chromosome 7 spans about 159 million base pairs (the building material of DNA) and represents between 5 and 5.5 percent of the total DN ...

q36. If the TPT is hereditary, it is mostly inherited as an autosomal dominant trait, non-opposable and bilateral. The sporadic cases are mostly opposable and unilateral.

Syndromes

Triphalangeal thumb can occur in syndromes but it can also be isolated. The triphalangeal thumb can appear in combination with other malformations or syndromes. Syndromes include: *

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 ...

* Aase syndrome *

Diamond–Blackfan anemia Diamond–Blackfan anemia (DBA) is a congenital erythroid aplasia that usually presents in infancy. DBA causes low red blood cell counts (anemia), without substantially affecting the other blood components (the platelets and the white blood cells) ...

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.

Malformations include: *Radial polydactyly *

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� ...

*Claw-like hand or foot

Diagnosis

Classifications

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 Wood, treatment of the triphalangeal thumb, Clin Orthop, 1976 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.Buck-Gramcko, congenital and development conditions, the interphalangeal joints- hand and upper limb, 1987 Table 1: Classifications of Wood and Buck-Gramcko

Treatment

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,Zuidam JM, de Kraker M, Selles RW, Hovius SE, Evaluation of function and appearance of adults with untreated triphalangeal thumbs, J Hand Surg Am, 2010 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,Wood VE, The triphalangeal thumb, Operated hand surgery, 1998 while Buck-Gramcko advises to operate for all indications before the age of six years.Buck-Gramcko, The triphalangeal thumb, Congenital malformations of the hand and forearm, 1998 * 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 Ulnar collateral ligament (or UCL), may refer to: * Ulnar carpal collateral ligament * Ulnar collateral ligament of elbow joint The ulnar collateral ligament (UCL) or internal lateral ligament is a thick triangular ligament at the medial aspec ...

and the radial collateral ligament if necessary. * For type III of Buck-Gramcko classification proposable surgical treatments: :- smaller trapezoidal phalanx and under six years: removal of the extra phalanx and reconstruction of the ulnar collateral ligament. Lengthening of the radial collateral ligament is only indicated when the clinodactyly is still present after reconstruction of the ulnar collateral ligament. :- trapezoidal phalanx and older than six years: partial removal of the extra phalanx with correction of the angle.

Arthrodesis Arthrodesis, also known as artificial ankylosis or syndesis, is the artificial induction of joint ossification between two bones by surgery. This is done to relieve intractable pain in a joint which cannot be managed by pain medication, spli ...

of the

distal interphalangeal joint Distal interphalangeal joints are the articulations between the phalanges of the hand or foot. This term therefore includes: * Interphalangeal joints of the hand * Interphalangeal joints of the foot The interphalangeal joints of the foot are bet ...

(DIP). * For type IV of Buck-Gramcko classification the surgical treatment typically consists of an

osteotomy An osteotomy is a surgical operation whereby a bone is cut to shorten or lengthen it or to change its alignment. It is sometimes performed to correct a hallux valgus, or to straighten a bone that has healed crookedly following a fracture. It is ...

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.

References

External links

{{Commons category, Triphalangeal thumb Congenital disorders Fingers Plastic surgery