Anatomy

The skin receives its blood supply by means of well-defined vascular territories termed angiosomes.5 Angiosomes are the vascular equivalent of dermatomes, which describe the cutaneous distribution of peripheral nerves. Analogous to dermatomes, angiosomes describe the vascular territory of cutaneous blood flow based on the arteries. Knowledge of these angiosomes forms the basis of many types of flaps used to cover soft tissue defects,6–13 and can guide the surgeon when considering surgical approaches, extension of traumatic wounds, or reoperations through previously traumatized skin.

Common angiosomes of the arm and leg are shown in Figs. 2.1 and 2.2 . The blood supply to a given cutaneous angiosome arises from the deeper source vessels through the perforating vessels. These perforating vessels travel to the fascia and skin of a given angiosome through either muscle or the intramuscular septa (Fig. 2.3). Once these cutaneous perforating vessels reach the deep fascia, they distribute axially along the fascia and send branches superficially to the subdermal plexus of the skin. At the fascial and subdermal levels, there are longitudinal networks of vessels connecting the vascular territories of adjacent perforating vessels. Within the interconnecting zones of separate angiosomes are smaller-caliber anastomotic vessels known as choke vessels that regulate blood flow between angiosomes. When a neighboring angiosome sees a decrease in blood flow, these choke vessels may dilate to enable lateral flow to this angiosome.

This concept of blood supply explains the well-recognized adage that wounds around the ankle joint, knee, and anterior tibia have higher complication rates than those in other anatomic regions. In these areas, there are watershed zones at the junctions between neighboring angiosomes where blood supply may not be as robust. Blood supply to the soft tissue in these watershed areas relies heavily on longitudinal flow through the fascia and subdermal plexus from neighboring perforating vessels. These watershed areas commonly occur in tissue directly overlying tendon, bone, or joints where perforators are less prevalent.

Clinically, the vascular anatomy in these areas has several important implications. First, when dissecting down to deeper structures in these watershed zones, it is important to maintain the skin and underlying fascia as a unit and avoid undermining the skin. This careful dissection will best preserve the blood supply to the skin edge. Second, when planning an incision or deciding how far to undermine the fascia while gaining exposure, it is important to be mindful of the location of the perforating vessels that feed the over-lying tissue. In trauma and in reoperations, the condition of the perforating vessels must be assessed, as these vessels may have been injured or previously ligated. Careful treatment of the tissue and an understanding of vascular anatomy are essential to successfully designing operative exposures and local flaps in the orthopaedic patient.

Initial Assessment and Classification

The assessment of a wound involves an initial survey assessment of the wound in the emergency department, whereas a more comprehensive assessment is performed in the operating room. In the emergency department, the surgeon should begin with an evaluation of the overall condition of the patient. Careful attention to the patient′s physiology is required. Factors such as resuscitation status, medical comorbidities, more urgent surgical considerations, and smoking history should be ascertained.

In a teaching setting, only one clinician, such as an orthopaedic resident, should examine the wound directly, because repeated examinations by multiple clinicians are associated with a higher incidence of infection. A digital camera may be used to accurately convey the extent of the injury to the senior surgeons. The degree and type of contamination should be assessed. Time also is a factor in decision making. For example, a wound that was exposed to water for a prolonged period of time or that is already 12 hours old is different from a wound that occurred in a motor vehicle accident 2 hours ago and may lead the surgeon to suspect different organisms.

Two classification systems are used to describe soft tissue injury. The Tscherne classification of closed fractures was developed in 1982 (Table 2.1).14 It relies on a relatively subjective description of the general condition of the soft tissues based on observation, mechanism of injury, and severity of the fracture. This classification system, which is applied only to closed fractures, is inherently subjective and entails moderate interobserver variability; nevertheless, it is widely used.

The Tscherne classification was expanded by the AO Foundation to provide a more objective system of classification that incorporates injury grading of each component of soft tissue. In this system, wounds are classified by the extent of injury to the integument, muscle and tendon, and neurovascular tissue (Table 2.2). This classification system is very complicated and difficult to use in practice, but it does encourage the surgeon to think systematically about the injury to soft tissue.

In the management of a patient with soft tissue trauma, it is less important to appropriately classify the wound than to critically examine all aspects of the soft tissues and plan surgical treatment appropriately. The surgeon should consider the injury to each component of the soft tissue and the implication of that injury in terms of healing the fracture.

Open fractures are classified used the Gustilo-Anderson classification. Type I injuries have a skin wound that measures less than 1 cm, and have minimal periosteal stripping and little bony comminution, suggesting a low-energy mechanism of injury. Type II injuries have more periosteal stripping with a larger skin wound, 1 to 10 cm. Type III injuries are associated with larger skin wounds, extensive periosteal stripping, and a much higher energy fracture pattern. They are further classified into IIIa, which have the above characteristics; IIIb, which require flap coverage for closure; and IIIc, which require vascular repair. The classification system is intended to place more emphasis on the degree of injury to soft tissue and the degree of contamination of the wound, rather than strictly on the size of the external wound. Therefore, certain injuries such as those caused by high-energy weapons, shotguns, and farm or battlefield injuries are automatically classified as type III because of the potential for contamination and extensive soft tissue injury. Although this classification system is generally well known and universally reported in the literature, several authors have reported that it has less than good inter-rater correlation.15,16

Source: Tscherne H, Gotzen L. Pathophysiology and classification of soft tissues associated with fractures. In Fractures with Soft Tissue Injuries. Berlin: Springer-Verlag; 1984.

Source: Südkamp NP. Soft tissue injuries of the tibia. In Thomas P. Ruedi, Richard E. Buckley, Christopher G. Moran, Eds. AO Principles of Fracture Management. Stuttgart: Thieme; 2007

A newer classification has been developed by the Orthopaedic Trauma Association17 to address the issue of inter-rater reliability. This system includes a more objective rating of the various tissues involved in fractures, such as skin, muscle, and arteries, as well as bone loss and the degree of contamination. Each aspect of the fracture is rated according to a three-tier assessment (see text box).

This classification has been evaluated for inter-rater agreement and seems to be an improvement over the Gustilo-Anderson classification.18 This classification has not yet gained widespread use.

Soft Tissue Handling

Many surgeons, especially more junior surgeons, do not appreciate the extent to which careful soft tissue handling can improve the viability of the wound bed. They cannot alter the damage done to soft tissues at the time of injury, but they can avoid further damage by learning good soft tissue techniques.

Proper soft tissue handling is an art that is either learned from years of conscientious self-examination and correction or from learning by observation of the masters. Unfortunately, it is difficult to teach soft tissue techniques in a book. However, there are some basic principles that can be taught didactically. This section provides some guidelines that may prove useful to both experienced and novice surgeons.

Instrument Handling

A common mistake when using the scalpel is to allow the blade to skive the soft tissues. The blade should always dissect perpendicular to the skin to avoid devitalizing the skin. Scissors, when used to dissect down to the fascia, should remain in the plane of the incision, avoiding undermining of the skin (Fig. 2.4). Forceps should be used to retract, rather than pick up, damaged tissue. They should never squeeze injured tissue. When possible, pick up fascia rather than skin. In areas with poor blood supply, retractors should be used only after exposing the deep fascia and should be placed below the fascia. Retractors should be relaxed whenever they are not needed for exposure. Self-retaining retractors are particularly dangerous, because they are not smart enough to know when to relax.

Internal Fracture Reduction

Periarticular fractures can be reduced from within the fracture itself. Fig. 2.5 shows an approach to central depression of an articular fracture that allows fixation and bone grafting with minimal soft tissue dissection. This is accomplished by planning the skin incision over a cortical fracture line that would facilitate access to the depression fracture. The cortical wall fragment is displaced with a lamina spreader, and the depressed fragment is reduced. Bone graft is placed in the metaphysis. The cortical fragment is then closed and stabilized with a percutaneous screw or a plate placed using a percutaneous technique to place the proximal screws.

“No-Touch” Technique

The “no-touch” technique for the treatment of calcaneus fractures is widely accepted. Using this technique, the surgeon exposes the calcaneus through a lateral approach and then places a Kirschner wire (K-wire) in the fibula and the talar neck as retractors for the remainder of the reduction and fixation (Fig. 2.6). This technique reduces injury to the flap by maintaining constant, firm retraction on the soft tissue flap. This same technique can be used elsewhere, such as the distal tibia.

Wound Conditioning

Wound conditioning refers to efforts to improve the likelihood that a wound can be successfully closed. It may include efforts to reduce swelling, improve vascularity, decrease bacterial colonization, provide temporary coverage for wounds, or prevent retraction of skin edges.

Skin Traction (Rubber Bands and Staples)

A very effective technique for achieving wound closure during a subsequent surgery is the use of vessel loops and staples. This technique is applicable when wounds cannot be closed as a result of swelling of the soft tissues. This is commonly the case with fasciotomies done for compartment releases,21 but it may be applied to other injuries where a wound cannot be closed simply because of the soft tissue swelling. It is not successful with wounds in which there is tissue missing. Using this technique, a vessel loop is stapled to the apex of a wound near the wound edge (Fig. 2.7), and then, in a fashion similar to shoelaces, the vessel loop and staples are alternated back and forth across the wound. This technique produces constant pressure on the skin edges, and, as the swelling decreases, the skin edges may be reapproximated sufficiently to allow using suture at a second surgery. This technique may also be used in cases where one wishes to avoid wound retraction while awaiting definitive skin grafting.

Related posts:

Treatment of Fractures in Geriatric Patients Musculoskeletal Infection Associated with Skeletal Trauma Thoracic Spine Injuries Distal Humeral Fractures Femoral Neck Fractures Pelvic Ring Injuries

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