Statewide Prevalence of Congenital Hand Anomalies: A 6-Year Review of Patients Presenting to Mississippi's Only Children's Hospital

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Serious birth defects including limb deformities, neural tube defects, and chromosomal abnormalities affect 1 in every 33 children born in the United States each year.¹ These congenital anomalies are a leading cause of infant mortality and carry a large economic burden, accounting for over $2.6 billion dollars in spending annually.² Although less immediately life-threatening than these defects, congenital upper extremity anomalies can negatively impact a child's life physically, psychologically, socially, and financially.

Previously, congenital limb anomalies were classified by the International Federation of Societies for Surgery of the Hand IFFSH)/Swanson Classification that delineated 7 separate classes: failure of formation, failure of differentiation, duplication, overgrowth, undergrowth, congenital constriction band syndrome, and generalized skeletal abnormalities.³ Currently, congenital anomalies of the hand and upper extremity are classified using the Oberg, Manske, and Tonkin (OMT) classification system, which is divided into 3 groups: malformation, deformation, and dysplasia.^4,5 Malformation is the main group in the OMT classification system, comprising abnormalities of entire upper limb or abnormalities of hand plate formation related to failure of formation, failure of differentiation, duplication, and limb undergrowth.^4,5

Malformations involving the hand plate comprise the majority of congenital hand defects and are classified based on the axis of the hand plate that they affect: proximodistal, radioulnar, dorsoventral, or unspecified.⁵ Diagnoses on the proximodistal axis include brachydactyly, symbrachydactyly, transverse deficiency, and cleft hand. There are numerous diagnoses for abnormalities involving the radioulnar axis, including radial and ulnar longitudinal deficiencies, radial and ulnar polydactyly, triphalangeal thumb, and ulnar dimelia, also known as mirror hand. The unspecified axis includes clinodactyly as well as any diagnosis of syndactyly, which is an abnormal connection between adjacent digits. Syndactyly ranges in severity from simple to complex, depending on bony involvement, and incomplete to complete, depending on nail bed involvement.⁵ Deformation and dysplasia are the other 2 classes of the OMT classification system. Deformations include constriction ring sequences and those not otherwise specified. Dysplasia includes variant growth patterns, tumorous conditions, and congenital contractures, such as camptodactyly and thumb in palm deformity.⁵

While the OMT classification system seems to be an improvement from the Swanson system of classification, there remains a significant lack of incidence and prevalence data for congenital hand and upper extremity anomalies in the literature.⁵ This deficit is likely multifactorial, stemming from (1) lack of federal and/or state reporting requirements, (2) absence of a centralized database for tracking such differences, (3) poor communication between electronic medical record (EMR) systems, (4) limited access to care, and (5) insufficient provider referral networks for the most-at-risk populations. As Mississippi's only pediatric hospital and the location of the only congenital hand clinic in the state, the University of Mississippi Medical Center (UMMC) is uniquely well-positioned to capture and report the per capita rate of congenital upper extremity anomalies. The goal of this study was to evaluate and report the rates of congenital limb anomalies of all pediatric patients presenting to UMMC from 2015 to 2020.

Following institutional review board approval, a retrospective chart review was performed using the institution's Epic EMR system. All patients presenting from 2015 to 2020 were identified via predefined International Classification of Diseases (ICD-9 and ICD-10) codes, including trigger thumb, congenital deformity of finger(s) and hand, polydactyly, syndactyly, reduction defect of upper limb, and other congenital malformations. These ICD codes are provided in Supplementary Table 1.

Inclusion criteria for this study included age less than 18 years at presentation with a confirmed diagnosis of congenital upper extremity anomaly. Exclusion criteria included age greater than 18 years at presentation, defects secondary to known trauma, and ICD codes for an isolated lower extremity. Additionally, for congenital trigger thumbs only, patients were excluded if they presented at greater than 2 years of age to ensure their diagnosis represented a true congenital contracture.

Demographic data collected included date of birth, gestational age, race, ethnicity, sex, county and zip code at time of birth, current county and zip code, and insurance status. Diagnosis data included each associated ICD code with named diagnosis, any associated syndromes, any associated lower extremity involvement, date of first presentation, laterality, location, and date of surgical correction(s). Maternal demographic data was collected if it was readily available in the patient's chart including date of birth, smoking status, and family history of upper extremity anomalies. Birth rates for the state were provided by the Department of Health.⁶

A 2-way frequency table was used to calculate the expected count for each variable. To examine the statistical significance of the observed findings, a chi-square test was used for categorical variables, and a 2-tailed test was used for continuous variables. The threshold for statistical significance was set at P < .05 for all analyses. Efforts were made to adhere to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines.

Demographics

Retrospective chart review of all pediatric patients presenting with congenital upper extremity anomaly resulted in 647 patients. Following application of inclusion and exclusion criteria, 473 patients with 500 upper extremity anomalies were included in this study. The average age of diagnosis was 236.5 ± 348.9 days. The majority of patients were male (n = 285, 60.3%), while 39.7% (n = 188) of patients were female. The most common maternal age range of patients born with congenital upper extremity anomalies was 20 to 24 years of age at 33.7%, followed closely by the 25 to 29 years at 33.2%. Finally, while the state of Mississippi is predominantly White at 58.8% followed by Black or African American at 38%, the majority of our patients presenting with congenital upper extremity anomalies were Black or African American at 65.5% followed by White at 27.3%. The racial distribution of preaxial polydactyly, postaxial polydactyly, and syndactyly was analyzed. Regarding preaxial polydactyly, 54.6% (n = 24) of patients were White and 31.8% (n = 14) were Black or African American. Postaxial polydactyly predominantly affected Black or African American patients, with 86.6% of patients being Black or African American and 9.9% being White. Syndactyly was more evenly spread, with 46% (n = 17) being Black or African American and 48.7% (n = 18) being White. Demographic results are summarized in Table 1 and Table 2.

Table 1. Patient and Maternal Demographic Data

Table 2. Racial Distribution of Polydactyly and Syndactyly

Diagnoses

A total of 500 congenital upper extremity anomalies were seen in 473 of the 222,408 live births (LBs) in Mississippi during this 5-year time frame, giving an average rate of 21.5 children affected by congenital upper extremity anomalies per 10,000 LBs or 22.5 upper extremity anomalies per 10,000 LBs. The 3 most common upper extremity anomalies were polydactyly at 13.1 per 10,000 LBs, congenital trigger thumb at 2.74 per 10,000 LBs, and syndactyly at 1.66 per 10,000 LBs. The polydactyly group was further divided into preaxial polydactyly with 1.98 per 10,000 LBs and postaxial polydactyly at 10.9 per 10,000 LBs. Most patients with polydactyly were affected only in the upper extremities (73.8%); however, 26.2% of patients had concomitant polydactyly of the lower extremities, and 62.5% of patients with upper extremity polydactyly were affected bilaterally.

Of the 37 patients with a syndactyly diagnosis, 32 records had sufficient data to analyze specific syndactyly describers: 62.5% (n = 20) had simple syndactyly, 37.5% (n = 12) had complex syndactyly, 25% (n = 8) were incomplete, and 75% (n = 24) were complete. Approximately 48% (n = 15) of patients were affected only on the right, 19% (n = 6) on the left, and 32% (n = 10) of patients had syndactyly of both hands. Diagnosis data are summarized in Table 3.

Table 3. Patient Congenital Upper Extremity Anomalies, Percentage of Total Births, and Incidence per 10,000 Live Births

Specific chromosomal abnormalities and other syndromes were reported in 28 of these patients and included Adams Oliver syndrome, Apert syndrome, Carpenter syndrome, cerebral palsy, Cornelia de Lange syndrome, ectrodactyly and cleft lip (EEC) syndrome, fetal alcohol syndrome, focal dermal hypoplasia, Joubert syndrome, Klippel-Trenaunay-Weber syndrome, mosaic trisomy 8, Nager syndrome, oral facial digital syndrome, Pierre Robin sequence, Poland syndrome, Rubenstein Taybi syndrome, short rib polydactyly disorder, TAR syndrome, trisomy 13, VATER/VACTERL, and Williams syndrome.

Geographic location

Utilizing addresses listed on patient's birth certificates, an incidence map of Mississippi was created to determine areas of higher incidence of congenital upper extremity anomalies in the state. Overall, Holmes County had the highest incidence of congenital upper extremity anomalies with 63.97 per 10,000 LBs, followed by Yazoo County and Hinds County, with rates of 63.16 and 62.08 per 10,000 LBs respectively. When polydactyly was studied individually, it followed a similar pattern, with a rate of 56.86 per 10,000 LBs in Holmes County, followed by 52.63 per 10,000 LBs in Yazoo County and 50.74 per 10,000 LBs in Hinds County. Examining patterns of patients with isolated syndactyly demonstrated different geographical patterns, and we found the highest incidence in Choctaw County at a rate of 20.04 per 10,000 LBs, followed by Wayne County and Neshoba County with rates of 11.76 and 11.50 per 10,000 LBs, respectively. Overall prevalence of all anomalies in Mississippi is depicted in Figure 1. There were no patients treated at our hospital for congenital upper extremity anomalies in 24 of Mississippi's 82 counties.

Figure 1. Overall incidence map of patients presenting with congenital upper extremity anomalies by county.

Assuming that all patients in Mississippi with congenital upper extremity anomalies presented to Mississippi's only congenital hand center, such anomalies over the 6-year time period from 2015 to 2020 were present in 21.5 children per 10,000 LBs with a rate of 22.5 congenital upper extremity anomalies per 10,000 LBs. The most common diagnosis was postaxial polydactyly followed by congenital trigger thumb with incidence rates of 10.9 per 10,000 LBs and 2.74 per 10,000 LBs, respectively. Our diagnosis data were compared with the available incidence and prevalence studies in New York City, New York State, Sweden, and Western Australia with overall congenital hand anomaly rates of 33 per 10,000 LBs⁷, 27.2 per 10,000 LBs⁷, 21.3 per 10,000 LBs⁸, and 19.8 per 10,000 LBs⁹ respectively. Data from the New York Congenital Malformations Registry published by Goldfarb et al showed a higher prevalence of polydactyly cases in New York City but a higher prevalence of all other upper extremity anomalies throughout the state of New York. This difference in prevalence was attributed to racial disparities, with African Americans comprising 25.7% of the population in New York City versus 8.7% in New York State.⁷ Examining Mississippi Census data revealed similar trends. African Americans comprise 38% of the state's population, but 57.7%, 73.5%, and 83.1% in Yazoo County, Hinds County, and Holmes County, respectively.¹⁰ Syndactyly appeared to equally affect White and Black patients. After examining geographic data, we found syndactyly was the most common in Choctaw County, occurring in 20.4 per 10,000 LBs. Census data for this county showed 68.8% of the population was Caucasian and 29.2% was African American.¹⁰

The patient's residential location as well as financial means must also be considered. Although Children's Hospital of Mississippi is centrally located in the state, it may be geographically closer for some patients in Mississippi to pursue specialized care in other states, such as USA Children's and Women's Hospital in Mobile, Alabama; Children's Hospital of New Orleans in Louisiana; or Le Bonheur Children's Medical Center in Memphis, Tennessee. Depicted in Figure 2, the proximity of nearby Le Bonheur Children's Hospital likely explains this study's lack of representation in the northernmost counties of Mississippi. Financial considerations must also be addressed, as the median per capita income in Mississippi was $42,129, markedly lower than the national average per capita income of $59,510 in 2020.¹² This consideration may explain the lower reported prevalence rates in counties with lower financial means.

Figure 2. Map of the southeastern United States with selected children's hospitals in surrounding states.

This study is limited by the lack of mandatory reporting requirements as well as the assumption that all children will present to UMMC for clinical evaluation. Thus, our reported rate of 22.5 congenital upper extremity anomalies per 10,000 LBs is certainly underestimating the true prevalence rate in Mississippi. This study captured only patients reporting to Children's Hospital of Mississippi; these case numbers were then compared with the birth data released by the Mississippi Department of Health encompassing the entire state. For polydactyly, the most common anomaly identified, it can be safely assumed that the identified prevalence rate is an underestimation of true prevalence, as many clinic-based providers will simply suture ligate the extra digit during a pediatric visit.¹¹

In the past 5 years, only New York State has published similar findings delineating the incidence of congenital hand anomalies through their Birth Defect Registry. The prevalence of upper extremity defects presenting to UMMC from 2015 to 2020 was 21.5 per 10,000 LBs; however, 5 specific counties had significantly higher prevalences that ranged from 53.65 to 63.97 per 10,000 LBs. With socioeconomic barriers to health care and inadequate data collection for a registry, the true prevalence in the state of Mississippi is likely much greater than our data represents. To develop effective programs to comprehensively treat these pediatric patients, accurate reporting and data collection mechanisms are critical.

Supplementary Table 1: International Classification of Diseases (ICD) Codes for EPIC™ Data Query