Clinical Characteristics and Distribution of Thumb Polydactyly in South China: A Retrospective Analysis of 483 Hands

Epidemiology of congenital polydactyly and syndactyly in Hunan Province, China

OBJECTIVE

To describe the prevalence and epidemiology of congenital polydactyly and syndactyly in Hunan Province, China, 2016-2020.

METHODS

Data were obtained from the Birth Defects Surveillance System in Hunan Province, China, 2016-2020. Prevalence of birth defects (polydactyly or syndactyly) is the number of cases per 1000 births (unit: ‰). Prevalence and 95% confidence intervals (CI) were calculated by the log-binomial method. Chi-square trend tests (χ2trend) were used to determine trends in prevalence by year. Crude odds ratios (ORs) were calculated to examine the association of each demographic characteristic with polydactyly and syndactyly.

RESULTS

Our study included 847,755 births, and 14,459 birth defects were identified, including 1,888 polydactyly and 626 syndactyly cases, accounting for 13.06% and 4.33% of birth defects, respectively. The prevalences of total birth defects, polydactyly, and syndactyly were 17.06‰ (95%CI: 16.78-17.33), 2.23‰ (95%CI: 2.13-2.33), and 0.74‰ (95%CI: 0.68-0.80), respectively. Most polydactyly (96.77%) and syndactyly (95.69%) were diagnosed postnatally (within 7 days). From 2016 to 2020, the prevalences of polydactyly were 1.94‰, 2.07‰, 2.20‰, 2.54‰, and 2.48‰, respectively, showing an upward trend (χ2trend = 19.48, P < 0.01); The prevalences of syndactyly were 0.62‰, 0.66‰, 0.77‰, 0.81‰, and 0.89‰, respectively, showing an upward trend (χ2trend = 10.81, P = 0.03). Hand polydactyly (2.26‰ vs. 1.33‰, OR = 1.69, 95%CI: 1.52-1.87) and hand syndactyly (0.43‰ vs. 0.28‰, OR = 1.42, 95%CI: 1.14-1.76) were more common in males than females. Polydactyly (2.67‰ vs. 1.93‰, OR = 1.38, 95%CI: 1.26-1.51) and syndactyly (0.91‰ vs. 0.62‰, OR = 1.47, 95%CI: 1.26-1.72) were more common in urban areas than in rural areas. Compared to maternal age 25-29, hand polydactyly was more common in maternal age < 20 (2.48‰ vs. 1.74‰, OR = 1.43, 95%CI: 1.01-2.02) or ≥ 35 (2.25‰ vs. 1.74‰, OR = 1.30, 95%CI: 1.12-1.50).

CONCLUSION

In summary, we have described the prevalence and epidemiology of polydactyly and syndactyly from hospital-based surveillance in Hunan Province, China, 2016-2020. Our findings make some original contributions to the field, which may be valuable for future research.

Classification of radial polydactyly based on physical characteristics

BACKGROUND

Previous classifications in polydactyly of the thumb were by the level of duplication on radiography. This study aimed to develop a practical algorithm based on physical characteristics for treatment guidelines.

METHODS

The polydactylies were stratified using four physical characteristics: floating, symmetry, dominant side, and joint angulation/nail size. The algorithm identified the hypoplastic type and then stratified the polydactylies as symmetric and asymmetric. The asymmetric type was divided into ulnar dominant and radial dominant. The symmetric type was divided into adequate type and inadequate type. The prediction of treatments was studied retrospectively by the distribution of surgical procedures in 500 patients with 545 affected thumbs, by the new classification and the Wassel-Flatt classification.

RESULTS

Of the 545 polydactylies, 78 (14.5%) were categorized as the hypoplastic type, 369 (67.5%) as the ulnar-dominant type, 8 (1.5%) as the radial-dominant type, 70 (12.8%) as the symmetric adequate nail type, and 20 (3.7%) as the symmetric inadequate type. Treatments were excision and reconstruction in 403 polydactylies (73.9%), simple excision in 135 polydactylies (24.8%), and the Bilhaut-Cloquet procedure, ray amputation, and on-top plasty procedures were only performed in 7 polydactylies (1.3%). The distribution of surgical procedures was distinct among the new classification types and was similar among the Wassel-Flatt types.

CONCLUSIONS

The new classification stratified polydactylies by physical findings in a stepwise manner. Though surgical technical details are not included, this simple classification is useful for paediatricians and parents to understand how a surgical decision is made.

LEVEL OF EVIDENCE

Diagnostic Level IV.

Modified Radiographic Classification System for Congenital Thumb Duplication: An Analysis of 2,300 Thumbs in 2,108 Children

PURPOSE

The objectives of this study were to (1) evaluate the radiographic characteristics of children with congenital thumb duplication (CTD) seen in our institution between August 2015 and April 2021; (2) introduce a modified radiographic classification system (MCS) capable of including all cases of CTD based on their radiographic pathoanatomy; and (3) evaluate the inter- and intrarater reliability of the new classification system.

METHODS

We retrospectively reviewed 2,108 patients with 2,300 CTDs. The MCS is based on the Wassel-Flatt and Chung et al classification systems and includes specific subtypes from the Rotterdam and modified Wassel-Flatt classifications. The MCS is characterized by 4 groups according to the anatomical morphology of the duplication: A (joint), B (epiphysis), C (bone), and D (soft tissues). Each group includes 4 subtypes according to the location of the CTD, with subtypes 1-3 extending from the distal phalanx to the metacarpal or interphalangeal joints, then to the carpometacarpal joint, and with subtype 4 only including the triphalangia of the main thumb.

RESULTS

Among the 2,300 fingers, 360 (15.7%), 2 (0.1%), and 3 (0.1%) CTDs could not be classified according to the Wassel-Flatt, Chung et al, and Rotterdam classifications, respectively. According to the MCS, the 2 most common forms of CTD were A2 (680/2,300; 29.6%) and D2 (308/2,300; 13.4%). All cases could be classified according to this classification system. The MCS showed excellent intrarater (0.875) and interrater (0.851) reliability relative to the Wassel-Flatt (0.863 and 0.820, respectively), Chung et al (0.793 and 0.822, respectively), and Rotterdam (0.873 and 0.836, respectively) systems.

CONCLUSIONS

The MCS is a potential radiographic classification for CTD that enables the classification of all patients and has excellent inter- and intrarater reliability.

CLINICAL RELEVANCE

Existing classification systems do not allow classification of the full spectrum of CTD and are not always related to surgery, and some existing systems are complex, with many categories that are rarely encountered, or are difficult to use widely in clinical practice.

Atypical Wassel type VI thumb duplication treated with on-top plasty

Congenital thumb duplication is estimated to occur between 0.08 and 7.6 times per 1,000 live births; however its cause is still undetermined. In this report, we present a case of Wassel type VI thumb polydactyly. clinical examination revealed an optimal functional position and an aesthetically pleasing shape of the ulnar thumb as well as a superior nail and pulp. However, preoperative X-ray indicated a well formed carpometacarpal joint of the radial thumb compared to an underdeveloped CMC joint of the ulnar thumb. Through surgical procedure we combined the best parts of both thumbs with on-top plasty to achieve the most optimal outcome. In conclusion, it is important to determine an adequate treatment strategy for a patient based on both clinical and radiological assessments.

[Soft tissue balance technique by flexor pollicis longus tendon transfer for Wassel -D thumb duplication in children]

Objective

To investigate the effectiveness of soft tissue balance technique by flexor pollicis longus (FPL) tendon transfer for Wassel Ⅳ-D thumb duplication in children.

Methods

A clinical data of 14 children with Wassel Ⅳ-D thumb duplication met the selection criteria between January 2017 and January 2021 was retrospectively analyzed. There were 5 boys and 9 girls with an average age of 21.6 months (range, 18-35 months). Ten cases were left hand deformity and 4 cases were right hand deformity. During operation, the radial thumb was excised, and the FPL tendon of the radial thumb was used to reconstruct the soft tissue balance of the ulnar thumb. Postoperative evaluation included the range of motion (ROM) of passive flexion and extension of the interphalangeal joint (IP) and metacarpophalangeal joint (MCP), the alignments of the IP and MCP, the percentage of the width of the nail plate and the circumference of the thumb at the level of the IP to contralateral thumb.

Results

All operations were completed successfully, and all incisions healed by first intention. The children were followed up 12-36 months (mean, 21.7 months). At last follow-up, the ROM of passive flexion and the deviation of the IP, and the deviation of the MCP significantly improved when compared with those before operation (P<0.05); the ROM of passive extension of the IP and the ROM of passive flexion of the MCP did not significantly improve when compared with those before operation (P>0.05). The ROMs of passive extension of the MCP were 0° before and after operation. The width of the nail plate was 76.6%±4.1% of the unaffected side, and the circumference of the thumb at the level of the IP was 92.0%±9.1% of the unaffected side.

Conclusion

The soft tissue balance technique by FPL tendon trasfer can effectively correct the alignment of the Wassel Ⅳ-D thumb duplication in children, and maintain the correction effect effectively, but further follow-up and comprehensive evaluation are needed to investigate the long-term effectiveness.

Epidemiological characteristics and distribution of congenital thumb duplication in south China: An analysis of 2,300 thumbs in 2,108 children

OBJECTIVE

The objective of this study was to evaluate epidemiological and anatomical characteristics of children with congenital thumb duplication (CTD).

METHODS

We retrospectively reviewed 2108 children with CTD. Data regarding sex, age at the surgery, laterality, uni- or bilateral involvement, and dominant side were retrieved from the medical charts. Plain radiographs were used to classify all CTD according to Wassel-Flatt, Rotterdam and Chung classification systems and to evaluate the patho-anatomy of the duplication as well as the presence of associated anomaly.

RESULTS

A total of 796 girls and 1,312 boys with CTD (n = 2,300 thumbs) met the inclusion criteria. The male to female and unilateral to bilateral ratio were 1.6:1 and 10:1, respectively. Associated anomaly was found in 238/2108 patients (11.3%), and the middle phalanx deformity of the 5th finger was the most common one. A dominant thumb, larger and more developed, was on the ulnar side in 2270/2,300 cases (98.7%).According to the Wassel-Flatt classification, type IV (40.2%) was the most common deformity and the extra thumb was connected to the main thumb by a joint in most cases (437/780); overall, 15.7% of thumbs (n = 360) did not fit the Wassel-Flatt classification.According to the Rotterdam classification, type IV (51.3%) was the most common form; in most cases (363/1180) the thumb was hypoplastic or floating. Overall, 3/2,300 thumbs (0.1%) could not be classified according to Rotterdam classification.According to the Chung classification, type A was the most common subtype (44.1%); in most cases (716/1015) the duplication was at the level of the metacarpal bone. Overall, 2/2,300 thumbs (0.1%) did not fit the Chung classification.

CONCLUSIONS

In patients from southern China, CTD shows male and right-sided predominance with ulnar-dominant thumb. Abnormalities of the middle phalanx of the 5th finger are more frequent in patients with associated anomaly. The development of a simple and comprehensive classification system is needed to guide treatment and to adequately assess the epidemiological characteristics of patients with CTD in order to facilitate comparison between different patients' populations.

LEVEL OF EVIDENCE

III.