The effect of the epiphyseal growth plate on the length of the first metacarpal in triphalangeal thumb

Surgical Reconstruction for the Triphalangeal Thumb

The triphalangeal thumb poses a complex reconstructive challenge to the congenital hand surgeon due to its rarity and variable anatomy. We discuss the available evidence, reporting clinical characteristics and outcomes of surgical reconstructive procedures of triphalangeal thumb alongside a representative case. The congenital hand surgeon must approach each patient with triphalangeal thumb individually to optimize the use of available tissues to maximize functional and aesthetic outcomes.

Triphalangeal thumb: clinical features and treatment

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.

The missing segment of the autopod 1st ray: new insights from a morphometric study of the human hand

Whether the 1st segment of the human autopod 1st ray is a 'true' metapodial with loss of the proximal or mid phalanx or the original basal phalanx with loss of the metacarpal has been a long-lasting discussion. The actual knowledge of the developmental pattern of upper autopod segments at a fetal age of 20-22 weeks, combined with X-ray morphometry of normal long bones of the hand in the growing ages, was used for analysis of the parameters, percentage length, position of epiphyseal ossification centers and proximal/distal growth rate. The symmetric growth pattern in the fetal anlagen changed to unidirectional in the postnatal development in relation to epiphyseal ossification formation. The percentage length assessment, the distribution of the epiphyseal ossification centers, and differential proximal/distal growth rate among the growing hand segments supported homology of most proximal segment of the thumb with the 2nd-5th proximal phalanges and that of the proximal phalanx of the thumb with the 2nd-5th mid phalanges in the same hand. Published case reports of either metanalysis of 'triphalangeal thumb' and 'proximal/distal epiphyseal ossification centers' were used to support the applied morphometric methodology; in particular, the latter did not give evidence of growth pattern inversion of the proximal segment of the thumb. The presented data support the hypothesis that during evolution, the lost segment of the autopod 1st ray is the metacarpal.

Outcome of two types of surgical correction of the extra phalanx in triphalangeal thumb: is there a difference?

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.

Complete pseudoepiphyses with associated enhanced growth in hands and feet: a report of 2 siblings--case report

We present 2 siblings with multiple complete pseudoepiphyses in their hands and feet with associated symptomatic enhanced growth. Physical examination of the 6-year-old boy revealed long slender fingers and hyperplastic great toes. Radiography showed complete pseudoepiphyses in the first metacarpals, proximal and middle phalanges of the hands, and proximal phalanges of the feet. The patient's younger brother had a similar phenotype with slightly milder functional complaints. Genetic analysis did not reveal an underlying syndrome in these siblings.

Metapodial or phalanx? An evolutionary and developmental perspective on the homology of the first ray's proximal segment

The first mammalian metapodial (MP1) has periodically been argued to actually be a phalanx, because the first ray has one less element than the four posterior rays, and because the MP1 growth plate is proximal like those of all phalanges, rather than distal as in metapodials 2-5. However, growth plates are formed at both ends in non-therian tetrapod metapodials, and phylogenetic analysis demonstrates that growth plate loss is a therian synapomorphy that postdates the establishment of the mammalian phalangeal formula. These data, along with results of developmental and morphological studies, suggest that the MP1 is not a phalanx. The singular, proximal growth plates in MPs 2-5 are likely to be an adaptation to dynamic erect quadrupedal gait which was characterized by conversion of the posterior metapodials into rigid struts with the carpus/tarsus. While the adaptive significance of the reversed ossification of MP1 is less clear, we present three functional/developmental hypotheses.

Evaluation of function and appearance of adults with untreated triphalangeal thumbs

PURPOSE

Triphalangeal thumb is a congenital malformation characterized by an additional phalanx of the thumb. Although surgical treatment of this condition is common practice, in the past this was not generally advised. Therefore, a population with an untreated triphalangeal thumb is still present. The purpose of this study is to compare function and appearance of adults with an untreated triphalangeal thumb to a normal population.

METHODS

Twelve adults with 23 hands with an untreated triphalangeal thumb, unilateral or bilateral, were examined using objective measurements (thumb movement, joint instability, pain, and strength) and subjective measurements (visual analog scale; Disabilities of the Arm, Shoulder, and Hand questionnaire; and Short Form 36 health survey).

RESULTS

Objective measurements showed no limitations in range of motion or in grip and pinch strength. No joint instability was found in the interphalangeal joints. Five thumbs had instability in the metacarpophalangeal joint. Strength of the thumb in anteposition was diminished to 64% compared to a normal population. Opposition was diminished to 62%, and metacarpophalangeal joint flexion strength was diminished to 61%. The patients scored lower compared to a normal population for the domain of social functioning in the Medical Outcome Study 36-item short form health survey; the Disabilities of the Arm, Shoulder, and Hand questionnaire showed no differences. Visual analog scale scores for appearance of the thumb were scored low (2.2 of 10) by the adults, in contrast to visual analog scale scores for function (7.7).

CONCLUSIONS

The examined group of adults with an untreated triphalangeal thumb had adequate thumb movement. Thumb strength was diminished for all specific thumb functions (anteposition, opposition, and thumb flexion), as low as 55%, compared to normal controls. Self-rated scores indicate that patients perceived their functionality as good. The appearance, however, was rated much lower, implying a dislike of the thumb by the patients. This indicates that the main impact of an untreated triphalangeal thumb in daily functioning might not be the diminished function but rather the dissimilar appearance.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Implications for treatment of variations in length of the first metacarpal in different types of triphalangeal thumbs

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.

Growth plate formation and development in alligator and mouse metapodials: evolutionary and functional implications

Mammalian metapodials (metacarpals and metatarsals), unlike most long bones, form a single growth plate, and undergo longitudinal growth at only one end. The growth dynamics of non-mammalian tetrapod metapodials have not been systematically examined in order to determine if unidirectional growth is unique to mammals. Here we compare murine metapodial ossification in growth stages that parallel those of embryonic, juvenile and subadult American alligators (Alligator mississippiensis). Safranin O staining was used for qualitative histology, and chondrocyte differentiation and proliferation were assessed via immunohistochemistry for type X collagen and proliferative cell nuclear antigen (PCNA). We establish that growth plates form at both ends of alligator metapodials and are maintained in the subadult. PCNA results show that alligators and mice share common patterns of chondrocyte proliferation during growth plate formation. In addition, while alligators and mice differ initially in the degree of organization and pace of chondrocyte differentiation, these parameters are largely similar in established growth plates. However, the replacement of cartilage by bone is highly irregular throughout growth in the alligator, in contrast to the more uniform process in the mouse. These results indicate that while alligators and mammals share common mechanisms of chondrocyte regulation, they differ substantially in their processes of ossification. Phylogenetic analysis indicates that the direct ossification of one epiphysis and reliance on a single growth plate is a derived character (synapomorphy) in therian mammals and likely indicates an adaptation for erect quadrupedal gait.

Triplicated thumbs: a rarity?

SUMMARY

Triplication of the thumb is supposed to be a rare condition and a complex form of radial polydactyly. However, we encountered an unusually high number of triplicated thumbs at our unit. Is triplication of the thumb indeed a rare condition? In our study, 121 patients with radial polydactyly were recorded between 1933 and 2005. In nine patients of this group, triplicated thumbs, either unilateral or bilateral, were identified. This complex type of radial polydactyly occurs in various forms. A total of 11 triplicated thumbs were found, and all cases were combined with triphalangeal components. Only one of these 11 triplicated thumbs could be classified according to currently used classifications. In all cases, aberrant rays were excised, thumb length and alignment restored by osteotomies, joints were stabilised, tendons reinserted and nails and nail walls corrected if necessary. Also, in all cases, a correction of triphalangeal components was carried out. Triplications are a rarity, and have only been presented in single case reports. We found that triplicated thumbs are not so rare. The likely explanation for this is the identification of a genetic isolate (a deformity located at chromosome 7q36) with radial polydactyly and triphalangeal thumbs in the southwest region of the Netherlands. Treatment for the presented triplicated thumbs was based on the same general principles as for less complex forms of radial polydactyly (i.e. to assemble useful elements of the separate [partial] thumbs to reconstruct one functioning, stable thumb).