Seasonal Trends in Traumatic Digit Amputations: Experience of a Level І and a Level ІІ Hospital in a Northeastern State

Abstract

Background: Traumatic digit amputations are common hand injuries in the United States. The primary aim of our study was to describe the relationship between season and mechanisms of amputation. Methods: The Emergency Department and Orthopaedic Surgery Billing Department databases of our level І institution in the Northeast were reviewed to identify patients with a traumatic digit amputation between January 2010 and December 2015. Inclusion criteria were defined as any patient presenting with a partial or complete amputation through Verdan zone I or II. All patient information was entered into a secure database, including date of injury, demographic information, digits amputated, mechanism of injury (crush, laceration, avulsion, bite, blast, saw, snow blower, or lawn mower), and Verdan zones of amputation. In addition to descriptive statistics, Fisher exact and χ² tests were used to compare the incidence of these traumatic digit amputation mechanisms between seasons. Results: For this 6-year period, an average of 24 patients presented each season for treatment of a traumatic digit amputation. Of all seasons, spring had the highest proportion of lawn mower amputations (62.5%; P < .0001), summer had the highest proportion of blast amputations (75.0%; P = .011), and winter had the highest proportion of snow blower amputations (90.9%; P < .0001). All other traumatic digit amputation mechanisms had no significant seasonal variation in incidence (P > .30). Conclusions: Given that certain traumatic digit amputation mechanisms occur predictably during certain seasons, seasonal public education has the potential to prevent these debilitating injuries.

Introduction

The hand and digits were the site of injury for 4.8 million people in the United States in 2001. In 2001 and 2002, an average of 30 673 nonoccupational digit amputations was seen in the emergency departments (EDs) in the United States each year. Children and the elderly are the most likely to amputate their digits, particularly around doorways and with power tools, respectively.¹ Overall, crush and laceration injuries are most common.^2,3

Patient outcomes of traumatic digit amputations are strongly influenced by the mechanism of injury. Patients who experience amputation by laceration or bite have an increased risk of unplanned secondary revision and other adverse outcomes.^3,4 However, to the best of our knowledge, no studies have reported on the seasonal variation in mechanisms of injury that results in digit amputation.

Given the paucity of literature regarding the seasonal trends in digit amputation mechanisms, the primary aim of our study was to describe the variability of digit amputation mechanisms presenting to our institution. Our null hypothesis was that the mechanisms of digit amputations presenting to our institution would be similar among seasons.

Methods

After institutional review board approval, our institution’s ED and Orthopaedic Surgery Billing databases were used to identify patients seen from January 1, 2010, to December 31, 2015, for traumatic digit amputations through Verdan zone I or II (zone I: from the distal insertion of flexor digitorum superficialis [FDS] on the middle phalanx to the distal insertion of the flexor digitorum profundus on the distal phalanx; zone II: from A1 pulley to the distal insertion of FDS). The ED database included records from 2 hospitals within a health system in a Northeastern state, including an academic level I trauma center and a level II trauma center community hospital. Codes from the International Classification of Diseases, Ninth and Tenth Revisions and the Current Procedural Terminology constituted the initial search criteria (Tables 1 and 2).

Table 1.

ICD-9 and ICD-10 Codes Used for Initial Criteria for Patient Inclusion in the Chart Review.

	Diagnosis
ICD-9 codes
885.0	Traumatic amputation of thumb (complete) (partial), without mention of complication
886.0	Traumatic amputation of other finger(s) (complete) (partial), without mention of complication
887.0	Traumatic amputation of arm and hand (complete) (partial), unilateral, below elbow, without mention of complication
959.4	Hand, except finger injury
959.5	Finger injury NOS
E920.1	Accidents caused by other powered hand tools
E919.4	Accidents caused by woodworking and forming tools
ICD-10 codes
S60-S69	Injuries to the wrist, hand, and fingers
W27	Contact with nonpowered hand tool
W29	Contact with other powered hand tools and household machinery
W31	Contact with other and unspecified machinery

Note. ICD-9 = International Classification of Diseases, Ninth Revision; ICD-10 = International Classification of Diseases, Tenth Revision; NOS = not otherwise specified.

Table 2.

CPT Codes Used to Select Patients Who Were Billed for Procedures Relating to Digit Revision Amputation or Replantation.

CPT code	Procedure
26951	Amputation, finger or thumb, primary or secondary, any joint or phalanx, finger, including neurectomies; with direct closure
26952	Amputation, finger or thumb, primary or secondary, any joint or phalanx, finger, including neurectomies; with local advancement flaps (V-Y, hood)
20808	Replantation, hand (includes hand through metacarpal joints); complete amputation
20816	Replantation, digit, excluding thumb (includes metacarpophalangeal joint to insertion of flexor sublimis tendon); complete amputation
20822	Replantation, digit, excluding thumb (includes distal tip to sublimis tendon insertion); complete amputation
20824	Replantation, thumb (includes carpometacarpal joint to MP joint); complete amputation
20827	Replantation, thumb (includes distal tip to MP joint); complete amputation
11732	Avulsion of nail plate, partial or complete, simple; each additional nail plate
11750	Excision of nail and nail matrix, partial or complete (eg, ingrown or deformed nail) for permanent removal
11752	Excision of nail and nail matrix, partial or complete (eg, ingrown or deformed nail) for permanent removal; with amputation of tuft of distal phalanx
11762	Reconstruction of nail bed with graft
11765	Wedge excision of skin of nail fold (eg, for ingrown toenail)
64774	Excision of neuroma; cutaneous nerve, surgically identifiable
64778	Excision of neuroma; digital nerve, each additional digit (list separately by this number)
26910	Amputation, metacarpal, with finger or thumb (ray amputation), single, with or without interosseous transfer

Note. CPT = Current Procedural Terminology; MP = metacarpophalangeal.

Each patient’s chart was reviewed for date of injury, demographics, mechanism of injury, partial or complete amputation, and Verdan zones of amputation, and this information was entered into a secure database. Amputation mechanisms included the following: crush, laceration, avulsion, bite, blast, saw, snow blower, and lawn mower. Seasons included the following: winter (January to March), spring (April to June), summer (July to September), and fall (October to December). Patients were grouped by mechanism and by season and were excluded if their data were incomplete or incorrectly coded. In addition to descriptive statistics, Fisher exact and χ² tests were used to compare incidence between seasons, with statistical significance set at P < .05 a priori.

Results

Demographics

A total of 572 patients at an average age of 46.2 (range: 1.5 to 98) years incurred 719 traumatic digit amputations. Most patients were Caucasian (n = 442, 77.2%) and male (n = 497, 86.9%) (Table 3).

Table 3.

Patient Demographics.

Patients	Amputated digits	Average age, y	Race	Gender	Insured	Injured at work
572	719	46.2	Caucasian (442, 77.2%)	Male (497, 86.9%)	284 (49.7%)	239 (41.8%)

Injury Characteristics

The middle digit was the most frequently amputated digit (222, 30.8%), followed by the index (185, 25.7%) and ring (153, 21.3%) digits. Verdan zone I amputations were more common than zone II amputations, accounting for 609 (84.7%) amputations. Amputations through zone I of the middle digit (193, 26.8%) and zone I of the index digit (148, 20.6%) were the most frequent amputation locations. Crush (208, 36.4%) and saw (147, 25.7%) were the most common amputation mechanisms (Table 4). The distribution of digits amputated by season is given in Table 5.

Table 4.

The Most Frequent Digit, Verdan Zone, and Mechanism of Amputation.

Digit	Verdan zone	Mechanism
Middle (222, 30.8%)	Zone I (609, 84.7%)	Crush (208, 36.4%)

Table 5.

Distribution of Digits Amputated by Season.

Season	Thumb	Index	Middle	Ring	Small	Total injured digits
Winter, No. (%)	19 (12.0)	42 (26.6)	42 (26.6)	35 (22.2)	20 (12.7)	158 (100)
Spring, No. (%)	26 (13.2)	47 (23.9)	57 (28.9)	43 (21.8)	24 (12.2)	197 (100)
Summer, No. (%)	14 (7.9)	49 (27.7)	57 (32.2)	34 (19.2)	23 (13.0)	177 (100)
Fall, No. (%)	18 (9.6)	47 (25.1)	66 (35.3)	41 (21.9)	15 (8.0)	187 (100)
Grand total, No. (%)	77 (10.7)	185 (25.7)	222 (30.9)	153 (21.3)	82 (11.4)	719 (100)

Seasonal Trends in Digit Amputation Mechanisms

For this 6-year period, an average of 24 patients presented each season for treatment of a traumatic digit amputation. Of all seasons, spring had the highest proportion of lawn mower amputations (62.5%; P < .0001), summer had the highest proportion of blast amputations (75.0%; P = .011), and winter had the highest proportion of snow blower amputations (90.9%; P < .0001) (Figure 1). All other injury mechanisms had incidences that were similar between seasons (P > .30).

Figure 1.

Seasonal variation in mechanism of digit amputation. Spring had the highest proportion of lawn mower amputations, whereas summer and winter had the highest proportions of blast and snow blower amputations, respectively. No other amputation mechanisms exhibited notable seasonal trends.

Discussion

Traumatic digit amputations are common causes of morbidity.¹ Replantation success rates between 55% and 93% for total amputations have been published.⁵ Digit survival depends not only on the zone of injury, number of digits, ischemia time, age, and smoking status but also on the mechanism of injury.^5,6 Saw and laceration amputations are more likely to be successfully replanted than crush amputations, for example, due to differences in soft tissue involvement.^2,5 The mechanism of injury influences the success of replantation and revascularization and the need for subsequent surgeries after revision amputation.^3,5,6 We sought to determine when the different mechanisms of traumatic digit amputations predominate to help clinicians treat these frequent injuries, as well as to provide a baseline to monitor the effectiveness of public health awareness and prevention strategies.

We found that lawn mower, blast, and snow blower amputations are the most seasonal, predominating in the spring, summer, and winter, respectively. The other mechanisms of injury showed no significant seasonal patterns. These results indicate that resources should be devoted to public education around the safe use of lawn mowers in the spring, fireworks in the summer, especially in July, and snow blowers in the winter. Our analysis shows that these mechanisms are the most predictable temporally, and the literature tells us that they can be the most mutilating as well.^7-12 For example, Matheron et al⁷ found that firework amputations often involve multiple digits and both hands and tend to be serious. Education to inform the public of these predictable increases in specific traumatic digit amputation mechanisms could potentially prevent these devastating injuries, reducing the burden on hospital systems and patients. A decreased incidence of avoidable amputations would also mean a decreased total cost of health care, which currently represents 6.6% of our gross domestic product.¹³

Our findings are not entirely applicable to the entire country because our institution is in a Northeastern state with 4 seasons, including significant snowfall in winter. However, the finding that blast injuries are the most common in summer may be true nationwide due to the use of fireworks, although the precise incidence may vary by state (and with state law).

Most of the literature regarding lawn mower injuries focuses on children. One study found that a child is injured by a lawn mower in the United States every hour. Voluntary safety specifications for lawn mowers were first published in 1987 and have been revised periodically and have led to improvements in lawn mower design.¹⁴ From 1990 to 2014, the rate of lawn mower injuries dropped by more than 50%, likely due, in part, to design changes and increased awareness.¹⁵ There may be some hope drawn from the example of power saw hand injuries, which had an annual 5.8% decrease in incidence after mandatory regulations were put in place in 2007; previously, the incidence had been rising 18% annually.¹⁶

Our results are consistent with previous studies about firework injuries, which have found that 50% to 95% of injuries occur during the period immediately surrounding July 4 (as well as other holidays worldwide celebrated with fireworks).^17,18 However, safety legislation and public education have been shown to be effective in some cases to significantly reduce the injury burden,^19-21 although it still remains a public health issue. In the United States, firework injuries dropped nearly 30% from 2000 to 2010, driven in large part by a decrease in injuries from illegal fireworks. Children and men are most likely to be injured by fireworks, and hand injuries most commonly involve the thumb and the first web space.^8,17,22

Snow blower injuries to the hand are not necessarily caused by operator inexperience or lack of awareness; in fact, experienced operators are more likely to be injured.¹² Most injuries occur when the operator places his or her hand in the exit chute to remove an obstruction, after the machine has been shut down. Unfortunately, the mechanism has residual potential energy that is released when the obstruction is cleared, causing the injury. Interestingly, most operators are aware of the safety warnings regarding the exit chute before their injury.¹²

Limitations of our study include the number of hospitals (2) and the lack of diversity in our patient population (77.2% Caucasian). As discussed, the major limitation of this study is that it was performed in a Northeastern state with 4 seasons. Different states with different climates may have altered injury patterns and conclusions.

The mechanisms of digit amputations varied depending on the season, with lawn mower, blast, and snow blower mechanisms showing predilections for spring, summer, and winter, respectively. Given that amputations occur predictably at specific times of year, seasonal public education has the potential to prevent these debilitating injuries.