Soft tissue abnormalities in Wassel Type VI radial polydactyly: a detailed anatomical study

Radiographic features of congenital thumb duplication type C2 of Wu et al. classification: new subtypes and surgical strategies

Objective

This study aimed (i) to evaluate the radiographic characteristics of patients with congenital thumb duplication (CTD) type C2 according to the classification of Wu et al., (ii) to describe the various subtypes of type C2 CTD, and (iii) to propose a classification system that allows the identification of different surgical strategies based on the radiographic anatomy of this specific subtype of duplication.

Methods

We retrospectively reviewed 92 patients (92 thumbs) with type C2 CTD according to the Wu et al. classification in our institution between August 2015 and April 2021. All CTDs were classified according to the interphalangeal joint alignment of the main thumb at the posteroanterior radiograph of the thumb before operation: type I (no deviation), type II (ulnar deviation), and type III (radial deviation).

Results

All CTDs (n = 92) could be classified according to the proposed classification system: 76 (82.6%) were type I, 10 (10.9%) were type II, and six were type III (6.5%). According to the Kim system of subtype classification, there were 55 (59.8%) type 1, 24 (26.1%) type 2, and 13 (14.1%) type 3 cases.

Conclusions

The suggested classification completes the Wu et al. system and has the potential to guide surgical treatment in children with type C2 CTD.

Level of evidence

III.

Modified Wassel-Flatt Type III Radial Polydactyly: Subtypes and Their Outcomes

PURPOSE

We aimed to subdivide modified type III radial polydactyly and evaluate the applied surgical procedures and outcomes according to the subtypes.

METHODS

This study included 32 thumbs of 32 patients treated for modified Wassel-Flatt type III radial polydactyly from March 2008 to December 2018. Each patient was subclassified into parallel, divergent, and convergent types according to the alignment of the duplicated digit. The parallel type was further divided according to the treatment method applied. The parallel A group comprised patients treated with reconstructing the radial collateral ligament of the interphalangeal (IP) joint after removing only the distal phalanx and preserving the proximal phalanx of the extra digit, and the parallel B group comprised patients treated with excision of the extra digit at the bifurcation site of the proximal phalanx. We evaluated the Japanese Society for Surgery of the Hand scores and radiographic angulation of the IP and metacarpophalangeal joints at a mean follow-up of 38 months.

RESULTS

Fourteen cases were parallel type (6 and 8 in the parallel A and B groups, respectively), 14 were divergent type, and 4 were convergent type. Patients in the parallel A group had significantly better IP and metacarpophalangeal joint angulation and Japanese Society for Surgery of the Hand scores than those in the parallel B group. Patients in the parallel A group had significantly better Japanese Society for Surgery of the Hand scores than those in the divergent and convergent groups.

CONCLUSIONS

Reconstructing the radial collateral ligament of the IP joint after removing only the distal phalanx and preserving the proximal phalanx of the extra digit was associated with better outcomes than the excision of the extra digit at the bifurcation site in the parallel type cases. The parallel type treated with proximal phalanx preservation and ligament reconstruction had better clinical outcomes than other types of modified Wassel-Flatt type III radial polydactyly.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic IV.

Triplication and tetraplication of the thumb: a modification of the Rotterdam classification

We proposed a modification of the Rotterdam classification for thumb triplication and tetraplication. Twenty-one patients were included (24 cases of thumb triplication and four cases of tetraplication). These were analysed and classified according to a modification of the Rotterdam classification involving three steps; from the radial to ulnar side, we first identified each thumb on radiographs and gross appearance to divide into triplication or tetraplication. Second, we define the levels of duplication and established the nomenclature. Third, the aberrant features and their location were assigned for each thumb, again from radial to ulnar side. A surgical algorithm was also proposed. This modified classification may be helpful for characterizing the rare conditions of thumb triplication and tetraplication for use in patient and management and communication between surgeons.Level of evidence: III.

Wassel VI Thumb Duplication With Triphalangeal Radial and Ulnar Thumbs: Anatomy and Surgical Reconstruction

A 6-year-old otherwise healthy girl presented with a Wassel VI duplication of the left thumb metacarpal and triphalangeal radial and ulnar thumbs. The patient underwent successful thumb reconstruction by transposition of the distal ulnar thumb onto the radial thumb metacarpal. To the best of our knowledge, this case report represents the first published anatomical dissection and surgical reconstruction of a Wassel VI duplication with triphalangeal radial and ulnar thumbs.

Intraoperative Observation of the Proper Digital Nerves in Wassel-Flatt Type Ⅳ Radial Polydactyly

PURPOSE

The aim of the study was to present the intraoperative findings of the relevant digital nerves of the duplicated thumbs in an excision and reconstruction procedure for the Wassel-Flatt type Ⅳ radial polydactyly.

METHODS

The study was conducted on patients with Wassel-Flatt type IV radial polydactyly who underwent excision and reconstruction between 2018 and 2021 at our institution. The ulnar digital nerve of the radial thumb and the radial digital nerve of the ulnar thumb were identified and traced intraoperatively. The level of the bifurcation of the nerves and abnormal findings were documented.

RESULTS

A total of 123 hands in 119 patients were included in this study. In 114 hands, the bifurcation of the nerves was located within 1 cm of the metacarpophalangeal flexion crease. The radial digital nerve to the ulnar thumb was abnormally compressed in deep fascial tissue in 7 of these 114 hands. In 5 hands, the level of bifurcation was more than 1 cm proximal to the crease. No radial digital nerve to the ulnar thumb was identified in the remaining 4 hands.

CONCLUSIONS

Although rare, abnormal nerve compression of the digital nerve may exist in duplicated thumbs of Wassel-Flatt type IV radial polydactyly.

CLINICAL RELEVANCE

In an excision and reconstruction procedure, we suggest that the bifurcation of the nerves should be identified before the nerve to the radial thumb is excised to avoid injuring the nerve to the main ulnar thumb.

Use of the duplication range concept for understanding morphology and predicting prognosis in thumb polydactyly

This study systematically and comprehensively analysed 129 thumb polydactylies in 122 patients using a duplicating range concept based on the level of skin and skeletal bifurcation. Numerical levels were defined along the longitudinal axis of the ulnar thumb duplicate from distal to proximal: level 0 (thumb tip) to level 6 (carpometacarpal joint). The relationships between duplication range and morphological parameters were evaluated. Nail asymmetry was associated with skin bifurcation levels 0 to 2. Proximal phalangeal asymmetry and interphalangeal joint deviation, associated with skin bifurcation levels were assigned scores of 1 to 2.5 and 1 to 2, respectively. Metacarpophalangeal joint deviation had a bimodal distribution, at levels 1.5 and 4 of the longitudinal axes. Morphological similarity was found in patients with the same duplication range. The duplication range concept could potentially improve our understanding of morphology variation and predicting prognoses in thumb polydactyly.Level of evidence: III.