|Year : 2021 | Volume
| Issue : 2 | Page : 102-109
Radial polydactyly: A modification of wassel/flatt classification system and clinical series
Sinem Ciloglu1, Alpay Duran2
1 Department of Plastic, Reconstructive and Aesthetic Surgery, Haydarpasa Numune Training and Research Hospital, Istanbul, Turkey
2 Department of Plastic, Reconstructive and Aesthetic Surgery, Avicenna Hospital, Istanbul, Turkey
|Date of Submission||04-Apr-2020|
|Date of Acceptance||10-May-2020|
|Date of Web Publication||26-Mar-2021|
Dr. Alpay Duran
Department of Plastic, Reconstructive and Aesthetic Surgery, Avicenna Hospital, Istanbul
Source of Support: None, Conflict of Interest: None
Purpose: The purpose is to propose a modification of Wassel/Flatt classification system for radial polydactyly based on radiological findings and previously described classification systems. Materials and Methods: Thirty-five patients with radial polydactyly were included in the study. There were 47 supernumerary fingers. Patients' clinical and radiological data were evaluated retrospectively. Family history, sex, age, unilateral or bilateral placement, the origin of radial polydactyly, coexisting anomalies, and syndromes of each patient were documented. We classified cases into 13 different subgroups, according to X-rays and clinical findings. Results: One supernumerary digit was rudimentary Type, 2 were hypoplastic type, one was Wassel Type I, 3 were Wassel Type II, and 5 were Wassel Type III, 12 were Wassel Type IV, 5 were Wassel Type V, 7 were Wassel Type VI, 9 were Wassel Type VII, one was symphalangism, one was complicated type. Conclusion: We think it is beneficial to add complicated type (tetraplication, triplication) symphalangism, rudimentary and hypoplastic malformations together as a single comprehensive classification system to better define diagnosis and treatment plans.
Keywords: Polydactyly, radial polydactyly, rudimentary, tetraplication, Wassel classification
|How to cite this article:|
Ciloglu S, Duran A. Radial polydactyly: A modification of wassel/flatt classification system and clinical series. Turk J Plast Surg 2021;29:102-9
| Introduction|| |
IFSSH Scientific Committee on Congenital Conditions updated the category of congenital upper extremity anomalies as malformations, deformations, dysplasias, and syndromes in 2014. Thumb polydactyly, which is in abnormal radial-ulnar axis formation/differentiation subgroup in the Oberg, Manske, and Tonkin classification, which classifies anomalies based on developmental biology and pathogenesis rather than on morphologic features, and recognizes that processes such as formation and differentiation occur together and not independently.,,, Radial polydactyly is a relatively common congenital hand malformation, and several studies have reported the distribution of its various subtypes in the different geographical populations. Radial polydactyly ranges from a fully formed finger to a skin nub or a triplication/tetraplication malformation and really includes cases that were not able to be categorized according to existing radial polydactyly classification systems.
Historically, radial polydactyly categorized based on osseous anatomy findings in plain radiographs. The first studies to classify thumb polydactyly were not developed until the last century. Egawa and Millesi organized the various presentation patterns of thumb polydactyly into classification systems in 1966 and 1967, respectively. In 1969, Wassel proposed a classification system based on the duplication level of supernumerary parts. Similarly, Temtamy and Mckusick classified polydactylies as central, radial, and postaxial in 1969. Wassel and Temtamy-Mckusick classification systems were widely used because they are simple and understandable. Flatt's 1977 modification of the Wassel classification system included only Types I through VI and excluded the triphalangeal thumb, considering this presentation a distinct type of thumb deformity. Similarly, Tada and Egawa excluded triphalangeal thumb, which was Type VII in Wassel classification and added hypoplastic/floating type as Type VII They described floating supernumerary digit (as Type VII instead of triphalangism) as no osseous or articular connection with a principal thumb but contains bony elements. Rudimentary malformation was first described by Islam et al. and was added to the Wassel classification system in 1992. Appendage type described as hypoplastic extra digit on the radial surface of the thumb at any level and its base was unstable or floating, without ligamentous or bony structure. The pathology in the radial polydactyly has a wide spectrum, ranging from severe hypoplasia of one or both thumbs to symmetrical or asymmetrical malformation that reaches the metacarpal or carpal levels. Extra parts are not necessarily replicas in either size or shape. Hence, many surgeons prefer the term malformation to duplication.,,, This diversity in the presentation of radial polydactyly creates differences in the definition of radial polydactyly cases. In the last decades, authors such as Tada and Egawa, Zuidam et al., Al-Qattan, Islam et al. and Chung et al. have carried out studies on different classification systems, including cases not classified by Wassel/Flatt classification.,,,,
There are several large studies about radial polydactyly reported in the literature.,,, However, significant differences were noticed in the distribution of subtypes and presentation patterns of radial polydactyly in these studies due to possible gene pools accompanying the geographical populations.,,,,,,,,,,,,,, Classifications are important in terms of eliminating this problem, guiding surgical treatment, and providing a common language for diagnosis. Here, we propose a modification of Wassel/Flatt classification system for radial polydactyly based on radiological findings and previously described classification systems. The proposed system includes the complicated type (triplication or tetraplication), rudimentary type, hypoplastic type, symphalangism, and Wassel I-IX polydactyly types in a single classification system.
| Materials and Methods|| |
We performed a retrospective review after we received institutional review board approval. Thirty-five patients diagnosed with radial polydactyly, who presented to Department of Plastic, Reconstructive and Aesthetic Surgery, Haydarpasa Numune Training and Research Hospital and Sanlıurfa Mehmet Akif Inan Training and Research Hospital plastic surgery outpatient clinics between December 2015 and May 2017, were included in the study. There were 47 supernumerary fingers. Patients' clinical and radiological data were evaluated retrospectively. Family history, sex, age, unilateral or bilateral placement, the origin of radial polydactyly, coexisting anomalies, and syndromes of each patient were documented. We classified cases into 13 different subgroups, according to X-rays and clinical findings [Table 1].
The proposed classification system
- Rudimentary: Small appendage with a narrow pedicle without bony structure
- Hypoplastic: Defined as no osseous or articular connection with a principal thumb but contains hypoplastic distal or proximal phalanx or metacapal
- Wassel I: Bifid distal phalanx
- Wassel II: Duplicated distal phalanx
- Wassel III: Bifid proximal phalanx
- Wassel IV: Duplicated proximal phalanx
- Wassel V: Bifid metacarpal
- Wassel VI: Duplicated metacarpal
- Wassel VII: Thumb duplication with triphalangism
- Wassel VIII: Partial duplication of the carpals
- Wassel IX: Complete duplication of the carpals
- Complicated type: Described as triplication (three thumbs at the same or different levels; one or more components may show triphalangism) or tetraplication (four thumbs at the same or different levels; one or more components may show triphalangism) of thumb or polysyndactyly or coexistence of both
- Symphalangism: Wassel Types II-VII with symphalangism in one of the duplicated rays.
| Results|| |
We included 35 patients in the study. There were 47 supernumerary fingers. Twenty-third patients had unilateral polydactyly and 12 had bilateral polydactyly. The mean age was 3.8 years (range, 6 months to 22 years) and 16 patients (46%) were male, 19 were female. Seven patients (14%) had a family history of polydactyly in the little finger. Among unilaterally affected patients, 10 were right-sided and 13 were left-sided anomalies. One supernumerary digit was the rudimentary type, 2 were hypoplastic type [Figure 1], [Figure 2],[Figure 3], one was Wassel Type I, 3 were Wassel Type II [Figure 4], and 5 were Wassel Type III, 12 were Wassel Type IV [Figure 5], 5 were Wassel Type V [Figure 6], 7 were Wassel Type VI [Figure 7], 9 were Wassel Type VII [Figure 8], one was symphalangism [Figure 9], one was complicated type [Figure 10] and [Table 2] There is no case of triplication and Wassel Type VIII-IX in our study. In non-syndromic cases, three patients had malformation of the great toe, 5 had coexisting ulnar polydactyly, 1 had hydrocephaly, and 3 had coexisting cleft lip, 1 had coexisting microtia, 1 had coexisting hypospadias. One patient also had trisomy 21. Parental consanguinity was present in 3 patients.
|Figure 1: Clinical appearance of hypoplastic malformation with a residual distal phalanx remnant|
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|Figure 10: Radiological appearance of a tetraplication case (Two main thumb duplicated at the MCP joint. Radial sided thumb is triphalangeal. Radial sided triphalangeal thumb has a duplication starting from the IP joint (duplicated distal phalanges) and ulnar sided thumb has a duplication starting from distal phalanx (bifid distal phalanges)|
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| Discussion|| |
The Wassel classification is the most widely accepted classification system in the hand surgery literature for the past 50 years. Wassel reported on a series of 112 patients with radial polydactyly and proposed a classification system, which was based on the origin of the thumb duplication. While defining all these types, Wassel based on symmetry as can be understood from duplication and bifid terms. According to Wassel classification, Type I, bifid distal phalanx; Type II, duplicated distal phalanx; Type III, bifid proximal phalanx; Type IV, duplicated proximal phalanx; Type V, bifid metacarpal; Type VI refers to duplicated metacarpal. In addition to these types, Type VII indicates duplication containing the triphalangeal component. However, due to the fact that complex and asymmetric radial polydactyly cases have been reported by various authors over the years, the term of malformation is used instead of the term of duplication. Although the Wassel classification system is a simple, comprehensible, and frequently used classification system, it is insufficient to classify cases with triplication, tetraplication, hypoplastic, symphalangism, rudimentary radial polydactyly cases. This problem led to the idea of the search for alternative classification systems, in which more complex cases were categorized. The classification systems reported in the literature are summarized in [Table 3].
|Table 3: Previously Reported Classification Systems of Radial Polydactyly and Classification System in the Current Study|
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In the majority of the reported studies of radial polydactyly, the most common malformation was reported as Wassel Type IV, and the least common was the Wassel Type I.,,, Naasan and Page retrospectively analyzed the 43 radial polydactyly cases in the UK and reported the distribution of cases using the Wassel classification. Although, the rarest form was Wassel Type I, the most common malformation was reported as Wassel Type II in this study in contrast to the other large series in the literature. An interesting detail is in these studies that although Wassel Type I is the rarest form in all of these studies, there are triplication, rudimentary/floating, hypoplastic, or symphalangism cases in various degrees due to the regions where the studies are performed. For this reason, many authors shared the idea of adding these malformations in the classification systems.,,
Rudimentary malformation was first described by Islam et al. and this malformation was added to the Wassel classification system in 1992. This malformation defined as a small appendage with a narrow pedicle without ligamentous or bony structure by Islam et al. and Al-Qattan., Rudimentary malformation is very common in the Far Eastern populations and is very rare in the Caucasian population. Islam et al. reported that 14.6% of the radial polydactyly cases was rudimentary in the Far East Study. In the Middle East study, Al-Qattan reported that 7.9% of the radial polydactyly cases were rudimentary. However, there is no case of rudimentary malformation in the British and The Netherland series., In our study, rudimentary malformations were seen in 2.1% of cases.
In 2008, Zuidam et al. proposed the Rotterdam classification system by categorizing the malformations in radial polydactyly. The most interesting aspect of this study was that the incidence of triplication is so high. In The Netherlands, an extremely high rate of thumb triplication is seen, which is attributed to the genetic pooling of the zone of polarizing activity regulatory sequence (ZRS) mutations. ZRS is a limb specific SHH enhancer on chromosome 7q36. Thumb triplication and triphalangeal thumbs are known to be more prevalent in populations with genetic isolates and mutations located at chromosome 7q36. The example of this genetic isolate is the Southwestern region of the Netherlands, where triplication of the thumb is seen in 8% of cases and radial polydactyly with triphalangism in 25% of cases. In our population, 19% of all subjects were classified as Type VII (triphalangism), but there was no triplication case. The remaining world literature includes only a few cases of reports about triplication. The inclusion of the triphalangeal thumb to classification systems, in particular, has always been controversial. In fact, Flatt's 1977 modification of the Wassel classification system included only Types I through VI and excluded the triphalangeal thumb., Similarly, in Rotterdam Classification, triplication and triphalangeal malformations were defined as a subgroup in the complete duplication of the proximal phalanx (Wassel Type IV) and a subgroup in the complete duplication of the metacarpal (Wassel Type VI) However, in most cases, the triplication malformation contains more complex anatomy rather than a duplication. First, Al-Qattan defined the triplication malformation as a different type of radial polydactyly in 2009. Triplication was defined as three thumbs (the triplication may be at the same or different levels; one or more components may show triphalangism) by Al-Qattan. In this study, Al-Qattan classified 228 radial polydactyly and presented the distribution of radial polydactyly types in the Middle East region. The author reported that rudimentary type was seen as 7.9%, triplication 0.9%, symphalangism 2.2% and unclassified cases 0.4%. Furthermore, in this study, 11.4% of the cases could not be classified by Wassel classification. There was no case of triplication in our study. However, there are five case reports in the literature except the Zuidam's and Al-Qattan studies and 3 of them were from Turkey.,,,, [Table 4] Therefore, although our study does not include triplication of thumb, we believe that it is useful to determine triplication as a complicated type in our classification systems.
In 2014, Dijkman et al. evaluated the plain radiographs of 520 patients diagnosed with radial polydactyly in two congenital hand surgery centers in Germany and the Netherlands, and classified these cases with the Wassel classification and the Rotterdam Classification as described by Zuidam et al. As a result of this study, it was reported that 40% of the cases could not be classified by Wassel classification. The unclassifiable cases were most commonly triphalangeal (63%), deviating (43%), or hypoplastic (39%). The authors reported that all cases were classified by the Rotterdam Classification system. Although it was emphasized that all 520 cases included in the study were classified by Rotterdam classification, the absence of any rudimentary malformation due to the gene pools of the geographical regions where the study was carried out was the limitation of the study. Since the rudimentary type is indispensable in different parts of the world, and many authors describe rudimentary malformations as a type of radial polydactyly.,
Although hypoplastic malformations were mentioned in the Rotterdam and Chung's classifications, Tada and Egawa described firstly Type VII thumb polydactyly as a ''floating or hypoplastic'' thumb rather than a triphalangeal thumb in 1983., Chung et al. also proposed an alternative classification based on the anatomic morphologic features of the origin of the duplicated digit to guide surgical decision-making and assess outcomes. Type I (joint type) defined as a duplicated digit with its own epiphysis that forms an articulation at its origin from the main digit. Type II (single epiphyseal type) defined as thumb duplication in which the accessory and main digits share a common epiphysis. Type III (osteochondroma-like type) defined as a digit in which the duplicated digit arises from the metaphysis of the main digit, resembling an osteochondroma. Type IV (hypoplastic type) defined as a digit that arises from the dominant digit by soft tissue alone without an identifiable osseous connection. Hypoplastic malformation includes a hypoplastic osseous or nail structure unlike rudimentary malformations, and the extra finger does not have a pedicle or articular connection with the interphalangeal joint or metacarpophalangeal joint. In this study, there is two examples of the hypoplastic type. The first case has a hypoplastic distal phalanx residue and a nail tissue; the second case has a hypoplastic proximal phalanx. These cases cannot be classified by the Wassel classification. However, Zuidam et al. have introduced a definition of hypoplastic form in the Rotterdam classification with the help of abbreviations (h: Hypoplastic) in Wassel classification. However, in our opinion, it is often not possible to describe these cases with the Wassel classification. Wassel described the subtypes of radial polydactyly as an extra finger originating a common epiphysial plate (bifid) or an extra finger originating from its own plate. Therefore, we think that it would be useful to classify these cases as a different group which cannot be described as rudimentary malformation.
Tetraplication malformation was first described by Jalili in the hand surgery literature. There was radial and carpal bone duplication associated with tetraplication in the case. In this study, there is only one case with tetraplication of the thumb, and there are no cases similar to this case in the other large radial polydactyly series except for the case reported by Jalili. Although it is a rare malformation, we think that it is useful to integrate tetraplication malformation into classification systems [Table 5].
Symphalangism was introduced to the classification systems by Zuidam et al. as a subgroup of radial polydactyly. First, Al-Qattan has identified malformations containing symphalangism as a separate type of radial polydactyly. In Al-Qattan's study, it was reported that five patients (2.2%) had symphalangism. The world literature contains only 15 well-documented cases of thumb malformation with symphalangism. It is interesting to note that most cases were from Asia, and in all, the symphalangism was seen in the radial ray. In this study, symphalangism was observed in only one case. In our case, there was a symphalangism with Wassel Type III polydactyly,,,,, [Table 6].
|Table 6: The well documented cases of thumb malformation with symphalangism|
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| Conclusion|| |
We think it is beneficial to add complicated type (tetraplication/triplication), symphalangism, rudimentary, and hypoplastic malformations together as a single comprehensive classification system to better define diagnosis and treatment plans.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]