A Nationwide Epidemiological Analysis of Finger Infections Presenting to Emergency Departments in the United States From 2012 to 2016

Abstract

Background: There is a paucity of literature exploring the epidemiology of finger infections presenting to emergency departments (EDs) on a national scale. The purpose of this study was to determine the national incidence of and risk factors for finger infections. Methods: Finger infections presenting to EDs between 2012 and 2016 were identified in the National Electronic Injury Surveillance System database. Finger infections were characterized by mechanism and type, with subanalyses for sex, race, and age. Results: Over this 5-year period, finger infections accounted for 80 519 visits to EDs in the United States. The annual incidence increased significantly from 4.4 per 100 000 person-years in 2012 to 6.2 in 2016. The 3 most common causes of finger infections were nail manicuring tools, knives, and doors. The most common diagnosis was finger cellulitis (46.3%). Significantly more men developed finger infections than women (relative risk of 1.4). The highest overall incidence was observed in 40- to 59-year-old men (7.8 per 100 000 person-years). Tenosynovitis resulted in the largest proportion of admissions (25%). Conclusions: We have demonstrated a rising incidence of finger infections presenting to EDs, with 40- to 59-year-old patients most at risk. The most common mechanism was the use of nail manicuring tools, such as nail clippers. Patient education may decrease finger infection incidence from these activities, and early detection of finger infections may be crucial to minimizing hospital admissions and invasive treatments.

Introduction

Undiagnosed or delayed diagnosis of bacterial and fungal finger infections can lead to significant local and systemic complications. These complications include early purulent infection and/or systemic sepsis, necessitating urgent surgical intervention and management with intravenous antibiotics, to late sequelae, such as chronic osteomyelitis or functional impairment from tendon adhesions. Fowler and Ilyas ¹ and Chong et al ² independently describe the epidemiology of causative organisms, antibiotic resistance, and patient risk factors associated with hand infections in an urban medical center and regional populations. Several papers including those by Salgado et al ³ and Harrison et al ⁴ further examine the epidemiologic rise in methicillin-resistant Staphylococcus aureus (MRSA) infections.

However, little information exists regarding the prevalence or epidemiology of finger infections in the United States. The purpose of this study was to use the National Electronic Injury Surveillance System (NEISS) database to determine the incidence and risk factors associated with finger infections in a cohort of patients that is representative of the US population. Understanding the epidemiology and risk factors associated with finger infections will help providers understand the societal burden associated with these infections. In addition, knowledge regarding risk factors that predispose patients to finger infections can help providers optimize the management of finger infections by helping them identify high-risk patients and educate those at risk regarding signs and symptoms of early infections and the need for medical care.

Methods

Data Collection

This was a retrospective study using data from the NEISS, a public database operated by the US Consumer Product Safety Commission (CPSC). As the NEISS database contains deidentified, public data, this study was considered exempt from institutional review board approval per statute 45 CFR 46.102.

The NEISS receives data on all injury-related visits to the emergency departments (EDs) from within 100 hospitals. These hospitals are a stratified sample of all hospitals containing EDs in the United States and its territories that are inclusive of adult and children’s hospitals, as well as trauma centers and community hospitals in both rural and urban areas. Each case is assigned a statistical weight based on the inverse probability of being selected. The CPSC annually ensures the accuracy of the sample by using a new sampling frame each year to allow NEISS sample weights to accurately reflect the total number of ED visits that occur nationally during a specific year. Variables included in the NEISS database for each case are the treatment date, patient age, sex, race, diagnostic category, body part injured, patient disposition, place of injury, and 2 descriptive narrative fields. The NEISS database has been used to analyze injury epidemiology with US population census data, for which the data set is specifically configured.^5-9

To isolate all potential finger infections, the NEISS database was queried for all finger-related visits (code 92) diagnosed as infections (71) from 2012 to 2016. Injury narratives were reviewed to only select cases with a clear diagnosis of finger infections. All identified finger infections were categorized into one of the following diagnoses: felons/abscesses, cellulitis, paronychia, tenosynovitis, and infection-other for those not fitting into the other 4 aforementioned categories.

Statistical Analysis

To determine incidence rates, the US Census Bureau ¹⁰ population statistics were used to calculate person-years at risk, according to sex and age. For ease of calculation, patients were divided into 20-year age groups. The incidence of finger infections was calculated using NEISS sample weights. Injury incidence was reported per 100 000 person-years at risk to standardize injury rates and allow for an easier comparison between other injury types. Ninety-five percent confidence intervals were calculated for all national incidence estimates.

Analysis of variance and χ² analyses were used for the comparison of continuous and categorical data, respectively. Z-test column proportions were used for post hoc analysis following χ² analysis. P values were adjusted using the Bonferroni method. Analysis was performed using Microsoft Excel (Microsoft Corporation, Redmond, Washington), SPSS version 24 (SPSS Inc., Chicago, Illinois), and OpenEpi version 3.02 (Emory University, Atlanta, Georgia). A value of P < .05 was defined as statistically significant.

Results

Over a 5-year period, finger infections accounted for 80 519 visits to EDs in the United States. The incidence increased significantly from 4.4 in 2012 to 6.2 per 100 000 person-years in 2016 (P < .001), for an overall incidence of 5.0 per 100 000 person-years (Figure 1). The most common diagnoses were finger cellulitis (46.3%), paronychia (29.9%), finger abscess/felon (12.9%), and tenosynovitis (2.5%). Significantly more men developed finger infections compared with women, with an incidence rate ratio of 1.4 (P < .01).

Figure 1.

Annual incidence of finger infections in the United States from 2012 to 2016 by sex.

The 3 most common causes of finger infections were nail manicuring tools, knives, and doors (Table 1). The largest overall incidence was observed in 40- to 59-year-old men (7.8 per 100 000 person-years) and women (5.4 per 100 000 person-years) (Figure 2). Seven percent of finger infections required hospital admission. Tenosynovitis was associated with the highest proportion of admissions (25%) compared with all other diagnoses (P < .01).

Table 1.

Most Common Mechanisms of Finger Infections in the United States From 2012 to 2016.

Abscess/felon			Cellulitis			Paronychia			Tenosynovitis			Infection-other
Mechanism	No.	%	Mechanism	No.	%	Mechanism	No.	%	Mechanism	No.	%	Mechanism	No.	%
1. Manicure equipment	1559	15.0	1. Knife-related	3740	10.0	1. Manicure equipment	9291	38.6	1. Knife-related	402	20.1	1. Knife-related	955	14.4
2. Door-related	1164	11.2	2. Fishing	2478	6.6	2. Door-related	2098	8.7	2. Computer-related	247	12.3	2. Manicure equipment	799	12.0
3. Knife-related	695	6.7	3. Manicure equipment	2347	6.3	3. Pins or needles	1248	5.2	3. Door-related	110	5.5	3. Door-related	428	6.5

Note. The number and percentage of finger infections of various types caused by the most common mechanisms of injury.

Figure 2.

Annual incidence of finger infections in the United States from 2012 to 2016 by age.

Discussion

Documenting more than 80 000 ED visits between 2012 and 2016, our analysis of the NEISS database demonstrates that finger infections are associated with a substantial burden to the US health care system. Without prompt diagnosis and treatment, progression of infection may lead to devastating systemic or local complications with resultant morbidity and mortality. The results of this study establish that ED visits for finger infection in the United States have significantly increased in volume from 2012 to 2016, suggesting the importance of educating patients with risk factors regarding infection prevention and early recognition if they do occur. The most common equipment associated with finger infections was nail manicuring tools, knives, and doors—all traumatic causes—consistent with reports of several smaller studies which found trauma to be the leading cause of finger infections.^11-15 Most frequently, we found these infections manifested as finger cellulitis, paronychia, and finger abscesses or flexor tenosynovitis. However, in prior literature, incidence of paronychia was much less common than in our population.^12-14

Our data demonstrate that middle-aged men were the most at-risk demographic for finger infections, which is consistent with the current literature.^{2,11-14,16,17} In a retrospective analysis of 94 hand infections (54 of whom had finger infections) undergoing surgical drainage, Turker et al ¹⁸ found that sex distribution was in a 2:1 ratio of male to female, with a mean age of 42 years. Chong et al ² noted that men comprised approximately 70% of patients with hand infection who underwent surgical intervention in a single-center study in Singapore. Interestingly, these researchers also noted a trend toward younger patients more frequently having hand infections in 2009 compared with 2000 (mean age in 2000, 58.4 years; mean age in 2009, 49.1 years). As observed in Figure 2, our findings are consistent with these results, with younger patients experiencing higher incidence of finger infections in 2016 compared with 2012. Accordingly, patients within the older cohorts are observed to have a decreased incidence of such infections over the same time frame.

Trauma is widely reported to precede hand and finger infections, with diabetic and immunosuppressed patients at particularly high risk of developing subsequent infections.^1,18 We found that manicure equipment, knives, and doors were most commonly associated with traumatic mechanisms preceding infection. In a smaller cohort, Chong et al ² described penetrating trauma to be the most frequent antecedent cause of hand infection. Thus, it is reasonable to suggest that patient behavior, such as occupation or personal activities, predisposes to clinically relevant finger infection. People giving or receiving manicures and using knives in the workplace or home are particularly susceptible to developing finger infection. Manicures have been previously described as a primary risk factor in the development of paronychia. ¹⁹ Our data demonstrate that manicuring tools were the traumatic cause of nearly 40% of all paronychias, which is over 4 times greater than any other equipment-related mechanism. In addition, manicuring tools were also found to be the leading cause of abscess or felon (Table 1).

Using the NEISS database, we found that 7% of patients with finger infection required hospitalization, with 25% of those admitted being diagnosed with flexor tenosynovitis. This relatively low hospitalization rate is in accordance with the most common diagnosis observed—paronychia—which can be treated in the outpatient setting with drainage and anti-staphylococcal antibiotics. ²⁰ As confirmed by our study, Jebson et al previously claimed that fingertip infections such as paronychias and felons are the most common hand infections. ²¹ Although we found cellulitis and paronychia to be the most common diagnoses of finger infection encountered in the ED, several other prior cohorts more frequently observed deep infections.^18,22 This is very likely attributed to the differences in cohorts studied.

Although we did not examine culture results in our study, several studies have reported that MRSA and methicillin-sensitive Staphylococcus aureus make up the highest percentage of culture-positive finger infections reporting to EDs, with community-acquired MRSA being the most common. Streptococcus species are also among the most common identified.^12,14,17,18 Unexpectedly, these studies found mixed results regarding the relationship between MRSA-positive finger infections and diabetes, intravenous drug use, and smoking.^13,16 However, studies consistently report increased complication rates for such patients.^14,23,24 In a case series of 103 acute fingertip infections, polymicrobial cultures were identified in 16.5% of cases, second in incidence to S aureus. ²⁵ Polymicrobial infections were also noted in 19% of acute bacterial hand infections by Fowler and Ilyas, ¹ particularly in intravenous drug users, animal bites, and diabetes. Greyling et al ²² found an association between HIV infection and gram-negative organisms in a series of patients with hand infections. Therefore, in consideration of the current literature, we recommend that high-risk patients presenting to the ED with finger infections be treated empirically for MRSA after cultures are obtained. Such high-risk patients include those with diabetes and other immunocompromised patients, as these patients are more likely to experience serious complications such as sepsis and amputation if not appropriately managed expeditiously. Depending on the mechanism and specific location of injury, common polymicrobial pathogens should also be appropriately covered.

There is a paucity of literature that discusses current, nationwide incidence rates of finger infection. Previous literature has focused on regional medical center and inpatient populations, examining the causative organisms, sensitivities, and treatment options for hand infections, without specific emphasis on finger infections. As such, our study examines finger infection trends nationally as opposed to those seen at 1 center, allowing this investigation to have both the largest sample size and the most external validity compared with previous studies. While this is a substantial strength, this study is not without limitations. We were unable to identify patient comorbidities, culture data, and patient outcomes, which limits our ability to compare our results with previous literature and perform a more rigorous multivariate analysis to examine multiple independent risk factors for finger infections. Another weakness of this study is that the NEISS database only captures patients presenting to the ED and not patients presenting to outpatient clinics of urgent care centers. Furthermore, prior studies on hand and finger infection often considered patients of greater illness severity, such as those who underwent surgical intervention or were hospitalized, whereas we considered all patients diagnosed with finger infections in the emergency setting.

Our study is consistent with the results of other studies that have identified middle-aged men as the most at-risk demographic for presenting to the ED with finger infection. In recent years, there has been a notable trend toward younger patients presenting with finger infections, particularly following sharp and penetrating trauma. Superficial finger infections such as cellulitis and paronychia were among the most common diagnoses, with only 7% of emergency visits with these diagnoses requiring hospital admission. There may be utility in education targeted toward these at-risk populations at the primary care level in explaining signs and symptoms necessitating medical attention, particularly for those patients in occupations at high risk of hand trauma. Given the relatively low hospital admission rate upon emergency presentation with a finger infection, the primary care practitioner may also benefit from education regarding the demographics and epidemiology described in this article to further assist in appropriate education, triage, and referral of patients with finger infections.