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Despite being a rare congenital limb anomaly, triphalangeal thumb is a subject of research in various scientific fields, providing new insights in clinical research and evolutionary biology. The findings of triphalangeal thumb can be predictive for other congenital anomalies as part of an underlying syndrome. Furthermore, triphalangeal thumb is still being used as a model in molecular genetics to study gene regulation by long-range regulatory elements. We present a review that summarizes a number of scientifically relevant topics that involve the triphalangeal thumb phenotype. Future initiatives involving multidisciplinary teams collaborating in the field of triphalangeal thumb research can lead to a better understanding of the pathogenesis and molecular mechanisms of this condition as well as other congenital upper limb anomalies. [ABSTRACT FROM AUTHOR]

Triphalangeal thumb is a rare congenital anomaly in which the thumb has three phalanges. Clinical presentation of triphalangeal thumb can vary considerably and can be present in both hands or unilateral. The thumb can be long with a finger-like appearance. The presence of clinodactyly depends on the shape of the extra phalanx varying from wedge-shaped to rectangular. Various joints, ligaments, muscles, and tendons of the first ray can be hypoplastic or absent, with varying degrees of stiffness or instability. The aim of surgical treatment is to reconstruct or correct the anatomic anomalies to obtain greater function and a more acceptable appearance. In our series, operations varied from removal of the delta phalanx with ligament reconstruction to multiple osteotomies and rebalancing of soft tissues. Results in these often complex cases can be rewarding if the surgeon has sufficient knowledge of the underlying anatomic differences. This review summarizes our current concepts of presentation and management of the triphalangeal thumb. [ABSTRACT FROM AUTHOR]

The surgical strategy of treatment of the opposable triphalangeal thumb is correction of the radio-ulnar deviation, reduction of the additional length and joint stabilization. The commonest procedures are: (1) removal of the extra phalanx and stabilization of the remaining joint; and (2) a combined reduction osteotomy with resection of the distal joint followed by arthrodesis. We treated 20 patients (33 hands). In 17 hands the extra phalanx was removed, and in 16 hands we used the combined osteotomy procedure of distal joint removal and arthrodesis. None of the patients in either group had an unstable interphalangeal joint. The mean radial or ulnar deviation in the interphalangeal joint was 5° degrees and 9°, respectively. Mean active flexion in the interphalangeal joint was 35° and 46°, respectively, in the two groups. Results for both procedures are similar, for both objective measures and self-rated function and activities of daily living. Either surgical approach seems reliable.Therapeutic, Level of evidence: Level III [ABSTRACT FROM AUTHOR]

Strength is regarded as normal in patients with an opposable triphalangeal thumb. Our clinical impression is, however, that intrinsic musculature is probably affected in all forms of triphalangeal thumb. Therefore, we established the strength of 38 thumbs in patients with a triphalangeal thumb. Patients were excluded if the intrinsic musculature was enhanced or if osteotomies of the first metacarpal were performed. On average, strength of all thumb functions was significantly diminished, up to 63% for opposition strength. Strength of the power grip was on average 70%. As shown in this study, strength of the musculature of the thumb is affected in all types of triphalangeal thumb. Although strength of the thumb is diminished, in the investigated group it is apparently sufficient in daily life, as these individuals did not seek surgical enhancement. However, reconstructive procedures that enhance intrinsic musculature must be considered in all types of triphalangeal thumb. [ABSTRACT FROM PUBLISHER]

Abnormal function in the triphalangeal thumb is partly due to its extra length, which is due not only to the extra phalanx, but also to differences in the length of the first metacarpal. This study investigated whether the additional length of the first metacarpal is influenced by the growth plate location alone, or also by the type of triphalangeal thumb. Fifty-nine hands in 37 patients with triphalangeal thumbs were examined for thumb type (delta 31, trapezoid nine and full type 19), growth plate location and relative length of the first metacarpal. The first metacarpals in all three types of triphalangeal thumbs were significantly longer than in the normal population. The length of the first metacarpal was related to the site of the growth plate. The type of triphalangeal thumb did not affect the length. These findings suggest that a corrective procedure on the first metacarpal should be considered in all types of triphalangeal thumbs. [ABSTRACT FROM PUBLISHER]