Blunt Force Trauma

Etiology

Blunt impact injuries result from direct contact of a blunt object with a body. A contusion results from the blunt impact of significant force to rupture capillaries underneath the skin surface while leaving the skin surface intact, while an abrasion results from scraping off of the superficial epidermis. Contusions and abrasions may show distinct patterns which can be used to match a specific wound to a potential weapon or implement; for example, a contusion over the forehead with multiple parallel, zig-zag lines may be matched to the sole of a shoe collected at the crime scene. A laceration results from the blunt impact of significant force to tear the skin, leaving strands of subcutaneous tissues bridging the wound. [4]Contusions and lacerations may also be present on internal organs. Blunt impact of significant force to a bone results in a fracture.

Epidemiology

Blunt impact injuries are commonly seen in living and deceased patients. The appearance of wounds depends on multiple factors, including the force, speed, length of time of impact, the surface area of contact, and elasticity of tissues impacted. A large, crushing force applied to a sizable area over several minutes will result in vast tissue damage; for example, failure of the integrity of a retaining wall at a construction site will likely cause significant blunt impact injury if the wall collapses on and traps the legs of an individual. Alternatively, a smaller force applied to a smaller area will result in less tissue damage; for example, the impact of a thrown baseball to the shoulder of an individual will likely cause minor blunt trauma.

Head trauma and exsanguination are the most common early causes of death due to blunt traumatic injury. 

Pathophysiology

Blunt trauma may result in internal or external hemorrhage depending on location and mechanism. Recent contusions are typically red/purple and go through a series of color changes as they heal. In general, a red/purple contusion will be more recent than a yellow/green contusion on the same patient. Similarly, recent abrasions and lacerations are typically red/purple and heal through the process of scab formation which imparts a tan/brown, crusted appearance to the wound. Postmortem abrasions will demonstrate a more tan/yellow, parchment-paper-like appearance indicating the absence of blood flow at the time the injury occurred.[5][6] Fractures heal through the process of callus formation and bony remodeling, features which can be examined microscopically to estimate the approximate age of the fracture and time since the injury.

History and Physical

Patients presenting with acute blunt trauma should be carefully assessed to ensure serious injuries are not missed. This entails obtaining a history of mechanism, events, comorbidities, allergies, medications, and last meal. Primary, secondary, and tertiary surveys are important, with appropriate intervention and resuscitation as required.

Blunt impact injuries usually manifest immediately after impact; however, deep contusions may not be visible on the skin surface for several days after the injury occurs. Examination of adjacent or underlying subcutaneous soft tissues may aid in distinguishing between contusion, in which there will be hemorrhage due to rupture of blood vessels, and lividity, a postmortem change in which blood is contained within blood vessels. Characteristics of fractures and associated soft tissue and/or skeletal muscle injuries may aid in establishing directionality of the impact causing the wound; for example, bumper impact to a pedestrian's legs often results in comminuted fractures of the tibia and/or fibula with a triangular bone fragment pointing in the direction the vehicle was moving.

Evaluation

The Advanced Trauma Life Support course was developed by the American College of Surgeons to promote a standardized, methodical approach to the evaluation of trauma patients. [7][8]The course teaches the initial assessment of trauma patients with a focus on preparation, triage, the primary survey, resuscitation, adjuncts to primary survey and resuscitation, consideration of the need for patient transfer, secondary survey, adjuncts to post-resuscitation monitoring, and reevaluation and definitive care. 

Diagnosis of various blunt impact injuries and estimation of time since the injury occurred are made by gross and microscopic examination of wounds. Recent blunt impact injuries are typically characterized by acute hemorrhage microscopically without evidence of organization or hemosiderin deposition, while older blunt impact injuries show evidence of red and white blood cell degeneration, fibroblast proliferation, and hemosiderin deposition.

Treatment / Management

Victims of blunt trauma who meet certain triage criteria have been demonstrated to have improved outcomes when managed in a trauma center. Patients with a Glasgow coma scale score greater than 13, respiratory rates less than 10/min. or greater than 29/min, or patients who need ventilatory support warrant triage to a trauma center. [9][10][11]Patients with two or more long bone fractures, crushed or pulseless extremities, amputations proximal to the ankle or wrist, pelvic fractures, paralysis, or depressed skull fractures warrant trauma center triage based on injuries.  The mechanism is also important as victims of high-risk auto crashes, falls from heights, motorcycle crashes, and pedestrian accidents with significant impact should be managed in a trauma center. Elderly patients, pregnant patients, anticoagulated patients, and young children should be managed in trauma centers capable of providing specialized care.

Mortality from trauma is declining for those who survive to reach trauma centers, representing improvements in resuscitation and management. A methodical approach that adheres to evidence-based guidelines for resuscitation and treatment is critical. Many traumatic injuries will heal with supportive care alone, while some may require surgery or interventional radiology for hemorrhage control. [12][13](B2)

Differential Diagnosis

• Domestic violence

• Hemorrhagic stroke

• Hypovolemic shock

• Lower genitourinary trauma

• Penetrating abdominal trauma in emergency medicine

• Pregnancy trauma

• Upper genitourinary trauma