Abstract
Purpose
To identify which patients and canines are involved in dog bites of the head and neck, and how they impact health systems.
Materials and methods
This is a single center, retrospective cohort study conducted from January 2012 to June 2013 in an academic, tertiary care center situated between multiple suburban and urban communities. Patients were identified by queried search for all bite-related diagnoses codes.
Results
334 unique dog bites were identified, of which 101 involved the head and neck. The mean patient age was 15.1 ± 18.1 years. Of the more than 8 different breeds identified, one-third were caused by pit bull terriers and resulted in the highest rate of consultation (94%) and had 5 times the relative rate of surgical intervention. Unlike all other breeds, pit bull terriers were relatively more likely to attack an unknown individual (+ 31%), and without provocation (+ 48%). Injuries of the head and neck had an average follow-up of 1.26 ± 2.4 visits, and average specialty follow-up of 3.1 ± 3.5 visits.
Conclusions
The patients most likely to suffer dog bite injuries of the head and neck are children. Although a number of dog breeds were identified, the largest group were pit bull terriers, whose resultant injuries were more severe and resulted from unprovoked, unknown dogs. More severe injuries required a greater number of interventions, a greater number of inpatient physicians, and more outpatient follow-up encounters. Healthcare utilization and costs associated with dog bites warrant further investigation.
1
Introduction
Animal bites are a preventable public health issue, and yet these injuries have been on the rise. Canine bites became a national concern with the 1985 CDC release that reported as many as 4.7 million Americans are annually bitten by dogs . Of these 4.7 million people, approximately 800,000 dog bite victims seek medical care . At the time of this report, dog bites were not a new issue; this CDC report was one of the first times this type of injury shifted from a local or regional concern to the national stage . Despite this national attention, the rate of dog ownership has continued to increase. In 2001, Shuler and her colleagues estimated that nearly 70 million dogs are owned in the United States, and that over 112 million people, or 40% of the population, have at least one dog in their home . With this increase in ownership, it is now estimated that lifetime risk of being bitten by a dog approaches 50% .
Dog bites account for over 80% of mammalian bites . Dog bites, unlike the bites of cats, rats or human are crush injuries . At first glance, these injuries can appear less severe than wounds from these other bites because the superficial tissue may remain intact. While the dermis may not be broken, the underlying tissue may still be devitalized by crushing, tearing, and/or avulsing the supporting blood supply . The force applied by a dog’s jaw is often estimated to be between 300 and 450 pounds per square inch (PSI) . There are reports of some canine bites having forces of upwards of 1800 PSI, but the primary sources for this claim cannot be verified . The force generated from some dog bites can fracture bone, dependent on the patient, dog breed and site of bite .
Dog bites injuries found in the head and neck disproportionately affect children, and have been previously reported to account for 3%-4% of all pediatric emergency visits, and up to 40% of all pediatric traumas . These injuries can lead to disfiguring scars and lengthy treatments. The need for facial plastic and reconstructive surgery and scar revisions for these injuries has been previously reported to be as high as 77% for these patients . The treatment of dog bite injuries has been reported as the 5th most common ICD-9 code used by plastic surgeons . Primary closure of open dog bite injuries of the head and neck is an accepted treatment due to the significant morbidity associated with scarring from healing from secondary intention .
Due to the significant morbidity and controversy surrounding dog bite injuries, this investigation was initiated to identify which patients and canines are involved in these injuries of the head and neck, and how these injuries are currently treated. The objectives of this study include the following: 1) describe the patient population that suffer dog bites in the head and neck, 2) determine the dog breeds and circumstances responsible for these head and neck injuries, and 3) evaluate the current treatment and follow-up care associated with dog bite injuries of the head and neck. We sought to test the following hypotheses : 1) The patients who present with dog bite injuries of the head and neck will be significantly younger, than those bitten in other anatomical locations. 2) The dogs responsible for these injuries will be known to the patient and will be more likely to bite these patients after they are provoked. 3) We further hypothesized that the most severely injured patients would require significantly more resources, measured by consultation, operations, and follow-up.
2
Materials and methods
This is a single center retrospective cohort study conducted using patient data from January 2012 through June 2013. The study was performed at the University of California Davis Health System, a public, academic, tertiary care center, which is situated between multiple suburban and urban communities in Sacramento, California. UC Davis is one of three trauma centers in the greater Sacramento area, and is the sole Level 1 Trauma Center for a catchment area of over two-million people. Prior to the initiation of this study it was approved under the supervision of the UC Davis Institutional Review Board.
Patients in the UC Davis Electronic Medical Record (EMR) were identified by queried search for all bite-related chief complaints and bite-related diagnoses codes (Emergency Department (ED) and/or admit). Patients with non-dog bite injuries were excluded from the study. For each encounter, the following information was extracted from the EMR: date of service, medical record number, name, age, sex, length of stay, chief complaint, diagnosis code, location of incident, insurance provider, and discharge date and time. Further data were extracted from the primary encounter narrative and all subsequent follow-up visits. This extracted data included: time of incident, breed, bodily location of injury, dog’s vaccination status, consultations, interventions, inpatient and outpatient antibiotics, relation of dog to patient, circumstances associated with the bite, tetanus and rabies vaccine administration, complications, and follow-up visit encounters. For clarity, the site of injury was dichotomized to general population (GP) of patients where bites affecting the body (including injuries of the head and neck) and those bites of only the head and neck region ( H&N) .
The Dog Bite Complication Index (DBCI, Table 1 ), a scale created prior to this investigation, was developed for the purpose of evaluating dog bites on any anatomic portion of the body. We created the scale for the entire body because, to our knowledge, one had not been previously developed and we intend to use this scale to compare dog bites and treatments in different anatomic locations. The scale was informed by the work of Lackmann et al., who previously developed a scale for categorizing facial dog bit injuries . Lackmann’s scale has previously been used by a number of authors to control for injury when comparing various treatments and surgical interventions for injuries of the head and neck . We also incorporated the efforts of Dire et al. and Cummings in order to determine anatomic locations at highest risk for complication following dog bite .
| Label | Description | Score |
|---|---|---|
| Minor | 3 cm or smaller simple laceration | 1 |
| Without join involvement | ||
| Without laceration/breaking of dermis in hand or foot | ||
| Mild | Greater than 3 cm simple laceration | 2 |
| Can involve hands or feet | ||
| Can involve the face, without neck or eye injury | ||
| Does not involve poorly vascular structures (joints, cartilage, etc.) | ||
| Moderate | Greater than 3 cm complex lacerations | 3 |
| Requires surgical exploration of wound or surrounding structures | ||
| Involvement of poorly vascular structures | ||
| Involvement of neck or eye | ||
| Severe | Tissue maceration | 4 |
| Bone involvement | ||
| Avulsion and removal of tissue | ||
| Other destruction of vascular supply |
Statistical analysis was performed using RStudio Version 0.98 (RStudio IDE, Boston, MA). Means are reported with the standard deviation (SD). The data set was evaluated using the Student t -test, Chi-squared, two-tailed population proportionality test, and generalized linear regression. Significance was determined with P values less than 0.05.
2
Materials and methods
This is a single center retrospective cohort study conducted using patient data from January 2012 through June 2013. The study was performed at the University of California Davis Health System, a public, academic, tertiary care center, which is situated between multiple suburban and urban communities in Sacramento, California. UC Davis is one of three trauma centers in the greater Sacramento area, and is the sole Level 1 Trauma Center for a catchment area of over two-million people. Prior to the initiation of this study it was approved under the supervision of the UC Davis Institutional Review Board.
Patients in the UC Davis Electronic Medical Record (EMR) were identified by queried search for all bite-related chief complaints and bite-related diagnoses codes (Emergency Department (ED) and/or admit). Patients with non-dog bite injuries were excluded from the study. For each encounter, the following information was extracted from the EMR: date of service, medical record number, name, age, sex, length of stay, chief complaint, diagnosis code, location of incident, insurance provider, and discharge date and time. Further data were extracted from the primary encounter narrative and all subsequent follow-up visits. This extracted data included: time of incident, breed, bodily location of injury, dog’s vaccination status, consultations, interventions, inpatient and outpatient antibiotics, relation of dog to patient, circumstances associated with the bite, tetanus and rabies vaccine administration, complications, and follow-up visit encounters. For clarity, the site of injury was dichotomized to general population (GP) of patients where bites affecting the body (including injuries of the head and neck) and those bites of only the head and neck region ( H&N) .
The Dog Bite Complication Index (DBCI, Table 1 ), a scale created prior to this investigation, was developed for the purpose of evaluating dog bites on any anatomic portion of the body. We created the scale for the entire body because, to our knowledge, one had not been previously developed and we intend to use this scale to compare dog bites and treatments in different anatomic locations. The scale was informed by the work of Lackmann et al., who previously developed a scale for categorizing facial dog bit injuries . Lackmann’s scale has previously been used by a number of authors to control for injury when comparing various treatments and surgical interventions for injuries of the head and neck . We also incorporated the efforts of Dire et al. and Cummings in order to determine anatomic locations at highest risk for complication following dog bite .
| Label | Description | Score |
|---|---|---|
| Minor | 3 cm or smaller simple laceration | 1 |
| Without join involvement | ||
| Without laceration/breaking of dermis in hand or foot | ||
| Mild | Greater than 3 cm simple laceration | 2 |
| Can involve hands or feet | ||
| Can involve the face, without neck or eye injury | ||
| Does not involve poorly vascular structures (joints, cartilage, etc.) | ||
| Moderate | Greater than 3 cm complex lacerations | 3 |
| Requires surgical exploration of wound or surrounding structures | ||
| Involvement of poorly vascular structures | ||
| Involvement of neck or eye | ||
| Severe | Tissue maceration | 4 |
| Bone involvement | ||
| Avulsion and removal of tissue | ||
| Other destruction of vascular supply |
Statistical analysis was performed using RStudio Version 0.98 (RStudio IDE, Boston, MA). Means are reported with the standard deviation (SD). The data set was evaluated using the Student t -test, Chi-squared, two-tailed population proportionality test, and generalized linear regression. Significance was determined with P values less than 0.05.
3
Results
Excluding insect and human bites, 421 charts returned from the query of the UC Davis EMR. Of those charts, 62 were identified as non-dog bites and 26 were return visits to the ED, thus, yielding a total of 334 unique dog bites. Of these 334 bites, 101 involved the head and neck ( Fig. 1 ). The demographic data for these patients can be found in Table 2 . The mean age of the patients with head and neck bites was 15.1 ± 18.1 years (range 11 months to 73 years, median of 6). This value is significantly less than the general dog bite population (t-test, p < 0.0001) where the mean age was 28.6 ± 21.5 years (range 11 months to 95 years, median of 26). Of these patients with head and neck bite injuries, 57% of them were below the age of 10, and these bites to the head and neck accounted for 70% of all the dog bite injuries experienced by individuals under the age of 18. The gender distribution was equal in the bites of the head and neck group (male, n = 47; female, n = 53), while the general population of dog bites trended towards men (men, n = 186; women, n = 147) (Test of Equal Proportions, p < 0.05).
| GP Bites | H&N Bites | P value | |
|---|---|---|---|
| N | 334 | 101 | |
| Sex | |||
| Male | 47 | 186 | < 0.05 c |
| Female | 53 | 147 | |
| Age (Years) | |||
| Mean | 28.6 ± 18.1 | 15.1 ± 18.1 | < 0.0001 d |
| Range | 0.92–95 | 0.92–73 | |
| Median | 26 | 6 | |
| Breed | |||
| Pit Bull | 114 (34%) | 32 (32%) | |
| Police Dog b | 21 (6%) | 0 (0%) | |
| German Shepherd | 14 (4%) | 5 (5%) | |
| Chihuahua | 10 (3%) | 3 (3%) | |
| Retriever | 8 (2%) | 6 (6%) | |
| Boxer | 8 (2%) | 4 (4%) | |
| Rottweiler | 8 (2%) | 3 (3%) | |
| All Others | 28 (8%) | 14 (14%) | |
| Not Reported | 123 (37%) | 34 (34%) | |
| Circumstance | |||
| Provoked | 84 (25%) | 40 (40%) | |
| Unprovoked | 134 (7%) | 27 (27%) | |
| Police Animal b | 22 (40%) | 0 (0%) | |
| Not Reported | 94 (28%) | 33 (33%) | |
| Relationship | |||
| Known | 197 (59%) | 73 (72%) | |
| Unknown | 87 (26%) | 16 (16%) | |
| Police Dog b | 28 (8%) | 4 (4%) | |
| Not Reported | 22 (7%) | 7 (7%) | |
| DBCI | |||
| Mean | 1.83 ± 1.22 | 2.63 ± 1.04 | < 0.0001 e |
| Median | 2.0 | 3.0 |
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