CLOSED SOFT TISSUE INJURIES

Closed injuries are characterized by variable degrees of damage to skin and underlying soft tissue and are an inevitable component of any fracture (see Plate 7-1). Blood vessels are most vulnerable to injury; thus, closed soft tissue injuries usually produce bleeding and swelling beneath the skin. The pathophysiologic process of a soft tissue injury can be broken down into three phases: inflammatory, proliferative, and reparative. The initial trauma injures the blood vessels, causing local bleeding, disruption of the microcirculation, and exposure of subendothelial collagen, which triggers the cellular inflammatory and clotting pathways. Inflammatory mediators increase capillary permeability, leading to edema, further local impairment of perfusion, and local tissue hypoxia and acidosis. Chemotactic factors also attract immune cells; mainly neutrophils and macrophages in the acute stage—neutrophils to defend against bacteria and macrophages for debridement of necrotic tissue. This phase reaches a maximum intensity at 1 to 3 days after the injury. The second, or proliferative, phase involves fibroblast production of extracellular matrix proteins and revascularization via endothelial ingrowth. The third, or reparative, phase involves scarring and fibrosis. Bleeding results from disruption of the blood vessels, and swelling results from damage to the endothelial lining of the blood vessels, which allows plasma to leak into the soft tissue spaces.

The most common soft tissue injury is a contusion (bruise) caused by blunt trauma that damages blood vessels and results in bleeding or swelling into the soft tissues. Usually the blood and the edema fluid dissect between the cells of the soft tissues, causing localized swelling. Bleeding produces the typical black-and-blue discoloration of a contusion. If large vessels are disrupted, the pressure of the escaping blood can induce separation of the tissue planes, leading to the accumulation of a large hematoma beneath the skin or between the deeper layers of soft tissue.

Contusion and hematoma formation may accompany more serious injuries of the limbs, such as fractures, dislocations, and sprains. The clinical examination of a patient with a painful contusion must rule out more serious underlying problems. A simple contusion or hematoma is treated with the immediate application of ice, a gentle compression dressing, and elevation of the injured part. Temporary restriction of activity—voluntary or with the application of a compression dressing or splint—facilitates the body’s ability to repair a soft tissue injury. The simple mnemonic ICES (Ice, Compression, Elevation, and Splinting) can be used to remember the principles of treatment. Because soft tissue injuries rarely cause significant disruption of important soft tissue structures, the body reabsorbs the extravasated blood and edema fluid within a few days, allowing gradual return of function. A large hematoma may take several weeks to resolve, however.

Soft tissue injuries associated with fractures (closed) can be described according to the classification system of Oestern and Tscherne, which grades soft tissue injuries from 0 to 3:

Grade 0: minimal soft tissue damage usually from an indirect injury to the limb and typically associated with a simple underlying fracture pattern

Grade 1: superficial abrasions or contusions typically associated with a mild underlying fracture pattern

Grade 2: deep abrasions with skin or muscle contusion usually from direct trauma to the limb and typically with a severe underlying fracture pattern

Grade 3: extensive skin contusion or crush, severe damage to underlying muscle, subcutaneous avulsion, and compartment syndrome and typically seen with a severe fracture pattern

This grading system is often used to guide timing and surgical planning when operative fixation is needed. It has also been shown to be predictive of the time to return to function.

An internal degloving injury is a unique type of soft tissue injury that may be seen with or without fracture. It results from significant shear forces causing the separation of subcutaneous tissues from underlying fascial or osseous structures with a resultant collection of liquefied fat, blood, and necrotic tissue. It is most commonly seen over the greater trochanter, where it is referred to as a Morel-Lavallée lesion, but can be seen in the flank or lumbodorsal regions as well. These injuries can compromise the overlying skin and soft tissue if not addressed surgically and present a risk for infection and a challenge in planning for operative fixation of underlying fractures.