Thumb polydactyly with radius hypoplasia--a case report

Clinical evidence of the association between radial longitudinal deficiency and radial polydactyly: a case series

Radial longitudinal deficiency (RLD) is commonly associated with thumb hypoplasia. The association between RLD and radial polydactyly (RP) is uncommon, but case reports or case series have been reported. We report our experience of managing patients with this association. A total of 97 patients with RLD were seen in our department, of which six were children with concomitant RLD and RP. Four children had both RLD and RP in the same limb; of them, three also had RLD in the contralateral limb. The mean age at presentation was 11.6 months. Awareness of this association alerts the clinician to look for RLD in the presence of RP and vice versa. This case series supports recent experimental and clinical evidence that RP and RLD may be part of the same developmental spectrum. Further studies may guide its inclusion as a possible new category in the Oberg-Manske-Tonkin (OMT) classification of congenital upper-limb anomalies.Level of evidence: IV.

Thumb Hypoplasia Occurring in Patients With Preaxial Polydactyly

PURPOSE

Thumb polydactyly and thumb hypoplasia are generally regarded as separate clinical entities. However, several case reports indicate that hypoplasia of both the thumb and the radius can occur in patients with thumb polydactyly and improved understanding of the genetics of the developing upper limb may give an embryologic explanation for this occurrence. Our hypothesis was that patients with preaxial polydactyly can have ipsilateral thumb hypoplasia that may not be recognized until after surgical reconstruction of the extra digit.

METHODS

We searched our surgical database for all procedures performed on patients with a diagnosis of preaxial polydactyly between 2002 and 2014. We reviewed the medical record for demographic data, surgical procedures, and follow-up information. In addition, all available radiographs were reviewed. Through this, we identified patients with a diagnosis of ipsilateral thumb hypoplasia, including when in the course of treatment the diagnosis was made, and any related subsequent procedures.

RESULTS

We reviewed 132 patients who underwent reconstruction of thumb polydactyly, 10 of whom were identified as having evidence of ipsilateral thumb hypoplasia, an incidence of 8.2%. The diagnosis of thumb hypoplasia was made before surgery in 3 of the 10 patients. One additional patient was noted to have a duplicate thumb on one side and a hypoplastic thumb on the contralateral side.

CONCLUSIONS

This study supports the hypothesis that children with preaxial polydactyly can have ipsilateral thumb hypoplasia that may not be noted before surgery. In this study group, 8% of patients with preaxial polydactyly had ipsilateral hypoplasia.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic IV.

Experimental evidence that preaxial polydactyly and forearm radial deficiencies may share a common developmental origin

Preaxial polydactyly is a congenital hand anomaly predominantly of sporadic occurrence, which is frequently associated with abnormalities of the Sonic hedgehog signalling pathway. In experimentally induced preaxial polydactyly, radial aplasia is also frequently observed. To determine if there is a correlation between preaxial polydactyly and radial aplasia, we induced ectopic Sonic hedgehog signalling during chicken limb development with application of a smoothened-agonist (SAG) or retinoic acid. Application of SAG caused malformations in 71% limbs including preaxial polydactyly (62%) and forearm abnormalities (43%). Retinoic acid application induced malformations in 56% of limb including preaxial polydactyly (45%) and forearm abnormalities (50%). Radial dysplasia and ulnar dimelia were observed in both experimental conditions. We demonstrate that ectopic Sonic hedgehog signalling may cause both preaxial polydactyly and predictable forearm anomalies and that these conditions could potentially be classified as one embryological group. We propose a unifying model based on known models of ectopic Sonic hedgehog signalling.

The association between preaxial polydactyly and radial longitudinal deficiency in syndromic cases: a report on nine families

Preaxial polydactyly and radial longitudinal deficiency are usually viewed as two different entities. We present nine families with different disorders in which both preaxial polydactyly and radial longitudinal deficiency were seen in the phenotype. This indicates that both entities may be caused by the same developmental error or insult. The pathogenesis is complex and may be related to the interactions of two signalling loops: the first loop (named as the radial longitudinal deficiency loop) contains genes/proteins responsible for the development of the radial ray; and the second loop (named as the preaxial polydactyly loop) contains the Sonic Hedgehog involved in the pathogenesis of preaxial polydactyly. This entity is named as the preaxial polydactyly-radial longitudinal deficiency association and should be included in the description of the preaxial polydactyly spectrum.

LEVEL OF EVIDENCE

IV.

The distribution of the types of thumb polydactyly in a Middle Eastern population: a study of 228 hands

Several series have reported the distribution of the types of thumb polydactyly in the Caucasian and Far Eastern populations. No data are available for the Middle East. A total of 196 Saudi patients (228 hands) with thumb polydactyly were reviewed. The most common type was Wassel type IV (33.8%) and the least common was Wassel type I (0.4%). A total of 26 hands (11.4%) did not fit into the classic Wassel types including 18 cases of rudimentary duplications, two cases of thumb triplication, and five cases of thumb duplication with symphalangism. Concurrent ipsilateral little finger triplication (one case) and contralateral thumb aplasia/hypoplasia (two cases) were seen and the developmental biology of these cases are discussed. After reviewing our results and other series in the literature, we concluded that Wassel types IV and I remain to be the most and least common types respectively in almost all races. However, the genetic pools of various races greatly affect the distribution of other non-classic duplications (unclassifiable by Wassel classification) such as rudimentary duplication in the Far East, triplication in the Southwestern region of the Netherlands, and symphalangism in Asia.

Two rare cases of association of thumb hypoplasia and polydactyly of the homolateral foot

This paper presents two cases of radial deficiency and thumb aplasia associated with polydactyly of the homolateral foot and a supernumerary toe resembling a thumb. To our knowledge, this association of malformations has not been described previously.

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).