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Necrotizing Fasciitis: An Overview

David Speers, CO
Donald Shurr, CPO, PT

As orthotists, we are commonly called upon to help people ambulate by returning stability to a compromised extremity. There are numerous reasons why a patient can experience a loss of function in the lower extremity. Some of the more common conditions observed are cerebrovascular accident, posterior tibial tendon disorder, multiple sclerosis, and cerebral palsy. These pathologies are seen regularly; therefore, most orthotists understand the benefits from the use of an orthosis. In these situations, it is usually an ankle-foot orthosis (AFO) or, less commonly, a knee-ankle-foot orthosis (KAFO).

However, sometimes we see a case in which the cause of the impairment is a condition that is not so common. One of these conditions is necrotizing fasciitis, commonly known as the flesh-eating disease. The purpose of this article is to define necrotizing fasciitis and to describe the pathomechanics of the disease and how it is treated. In addition, the article will discuss the role of the orthotist in assisting a patient with ambulation.

Soft-tissue infections that cause necrosis are by no means new. Cases of necrotizing fasciitis, which was a feared military disease, were documented as far back as the 18th century. During the 19th century, civilian outbreaks of this feared infection were seen and it was referred to as the "malignant ulcer." In 1883, Fournier described a necrotizing soft-tissue infection of the male perineum, which was termed "Fournier's gangrene." Then in 1952, Wilson used the term "necrotizing fasciitis" to describe the same infection in other parts of the body.¹ The infection received more attention from the press when Muppets creator Jim Henson died of a necrotizing fasciitis infection in 1990. The British tabloids came out with the term "flesh-eating disease" after a cluster of cases in Gloucestershire in 1994.²

Necrotizing fasciitis is a rapidly progressing bacterial infection of the soft tissue that destroys the subcutaneous fat and fascia. In most cases, the deep fascia and the muscle are spared from destruction by the infection, but myonecrosis can occur due to a compartment syndrome.² Many different bacteria can cause destruction of the soft tissue in a "flesh-eating" manner. In fact, culture specimens taken from wounds of patients with necrotizing fasciitis show that an average of three to four bacteria cause the infection 70% of the time.^2,3

The typical patient who has contracted a type of necrotizing fasciitis usually has an underlying illness that has weakened the immune system and has often incurred a disruption in the skin caused by a cut, ulcer, or even an insect bite. This opening in the skin serves as a portal of entry for the bacteria. Males and the elderly are at a higher risk for contracting the disease.^1,4 Diabetes remains one of the most common illnesses that weakens the immune system. Other predisposing factors include peripheral vascular disease, end-stage kidney disease, chemotherapy for cancer treatment, and immunosuppression due to organ transplant.

In the majority of cases, a common pattern is seen: An immunocompromised, male, elderly patient presents with a disruption in the skin that has allowed the entry of bacteria. However, there is one bacteria that can cause a very rapid necrotizing fasciitis and life-threatening situation all by itself. More alarming, it has caused necrotizing fasciitis in young, healthy individuals, and in many cases, no break in the skin was found to serve as an area of entry. This bacteria is group A streptococcus, or strep A, and when outbreaks are seen, much attention is given to them. Recently, it seems that the strep A bacteria has become even more virulent, and clusters of outbreaks are usually seen in the winter months.^5-7

The strep A bacteria is commonly found in the nose and throat of healthy individuals, and it is responsible for many, less-serious illnesses. These illnesses have been divided into two categories: the less serious, noninvasive infections and the more serious, invasive infections. It is unknown why some people become seriously ill with an invasive strep A infection and others do not, even if both are infected with the strep A bacteria.

The common noninvasive strep A infections include strep throat, rheumatic fever, impetigo, and scarlet fever. Strep throat is a very common illness that is easily treated by using antibiotics. However, if left untreated or partially untreated, it can lead to rheumatic fever that can damage heart valves. Impetigo is a mild skin infection that is characterized by open, draining sores and is easily treated using antibiotics. Scarlet fever is rarer than both impetigo and strep throat and is also easily treated using antibiotics.

Necrotizing fasciitis, which is caused solely by the strep A bacteria, falls under the invasive category. Another invasive strep A infection is streptococcal toxic shock syndrome, which causes the entire organ system to shut down and leads to rapid death.^8,9 Many cases of untreated strep A necrotizing fasciitis will turn into streptococcal toxic shock syndrome.^2,5,10

Invasive strep A infections are rare but do occur in clusters, usually in the cold weather months. The Centers for Disease Control estimates that there are 10,000 to 15,000 cases of invasive strep A each year.¹⁰ Of these, only 500 to 1,500 are cases of strep A necrotizing fasciitis. These numbers can be compared with the several million cases of strep throat and impetigo that occur each year. It is still not understood why some people develop a serious invasive infection and others do not. A review of the literature reveals mortality rates for necrotizing fasciitis that range from 20% to 70%, whereas the Centers for Disease Control estimates the mortality rate at 20% to 30%.^2,7,10

Unfortunately, there are no symptoms specific to the necrotizing fasciitis infection, but in most cases, common flu-like symptoms are present. Symptoms of a necrotizing fasciitis infection include swelling and redness of the infected limb, clear blisters in the rash which then turn a dark purple color, severe pain, and in many cases a minor trauma to the skin near the infected area. If undiagnosed, the symptoms worsen and are also accompanied by fever, chills, and nausea, with the rash-associated pain increasing. A common denominator in most cases appears to be pain that is disproportionate to the size of the rash or trauma on the skin. Uncharacteristic of the "flesh-eating" name, the skin usually remains intact as the infection spreads subcutaneously.^11-13

Many times a necrotizing fasciitis infection is mistaken for the more common condition of cellulitis. One reason for the high mortality rate for necrotizing fasciitis infections is the delay in proper diagnosis.^2,6 Cellulitis is easily mistaken for early-stage necrotizing fasciitis, but one factor that differentiates the two is the fact that cellulitis responds to antibiotics whereas necrotizing fasciitis does not. A necrotizing fasciitis infection is controlled only with massive debridement of necrotic tissue along with antibiotic therapy.

Proper diagnosis is critical in the treatment of necrotizing fasciitis, and in many cases, it is the major factor between life and death. One major clue that a soft-tissue infection is in fact necrotizing fasciitis is the failure of the infection to respond to antibiotic therapy within 24 to 48 hours.^2,4 Plain radiographs showing evidence of gas in the soft tissue is another key indicator, along with elevated muscle compartment pressure. Some argue that a muscle compartment pressure greater than 40 mmHg calls for immediate surgical exploration.⁵ A positive frozen-section biopsy specimen will also aid in proper diagnosis.

Once the diagnosis of necrotizing fasciitis is made, immediate debridement of necrotic tissue is called for. It is very common for a patient to undergo more than one debridement to make sure all of the necrotic tissue has been removed. At the same time, aggressive antibiotic therapy with clindamycin should be started. The wound should be examined daily, and the decision of whether or not to perform further debridement should be made. Dressings should be changed daily, and skin grafts should be performed to cover the wound once it is definite that the infection has been eradicated. Amputation of an entire limb is sometimes performed, but this is only done as a life-saving measure.⁴

Once the infection has been eliminated, the limb can remain compromised because of the debridement process or the myonecrosis and nerve necrosis that may result from a compartment syndrome. It is rare for the actual muscle tissue to undergo necrosis due solely to the infection, but it has been reported in some cases. The debridement process may have called for the removal of muscle tissue, which would leave a compromised limb. Also, a compartment syndrome can cause both muscle necrosis and nerve necrosis, thereby leaving a weakened limb. In any case, a flaccid limb can result from the removal of muscle or from nerve necrosis. On the other hand, contractures can develop during the myonecrosis process, when rigid scar tissue replaces the muscle.

Surgical debridement of the necrotic tissue is an essential part of the treatment of a necrotizing soft-tissue infection. Antibiotic therapy alone is useless unless the necrotic tissue is surgically removed. If muscle is removed in the debridement process, a weakened or entirely flaccid limb will remain. A flaccid limb is also a common result of nerve necrosis directly related to a compartment syndrome. The appropriate orthosis is determined by the extent of the weakness, the magnitude of the infection, and the lack of range of motion because of muscle contractures.

There is also a good possibility that a contracted limb will remain. If muscle necrosis is caused solely by a compartment syndrome, scar tissue replaces the muscle tissue and the result is a rigid, contracted limb. In this situation, the weakness is also accompanied by a severe lack of range of motion due to the contractures caused by the rigid scar tissue.

Necrotizing soft-tissue infections remain quite rare, but there has been a recent resurgence of this infection. This resurgence is not just due to the aging population. There are an increasing number of reports in the literature of necrotizing fasciitis caused solely by strep A.^2,5-7,14 Many times the affected limb can be salvaged, but it is often left compromised either by the massive debridements or a compartment syndrome. Even though necrotizing soft tissue infections are quite rare, the end result of a flaccid or contracted limb is not. The use of an orthosis, if prescribed, is appropriate in many of these situations. The proper orthosis is determined by the severity of the weakness, the extent that the limb is compromised, and the presence of contractures, if any.

It is possible that a practicing orthotist may never treat a patient who has encountered a necrotizing soft-tissue infection. But depending on where the practice is located, it is possible for patients with these types of infections to be seen more frequently. Three main factors indicate that these infections will be more prevalent in the near future. 1) The number of people with diabetes is rapidly increasing. Diabetics are at a higher risk of developing a necrotizing soft-tissue infection. 2) For unknown reasons, increasing numbers of young, healthy people are experiencing necrotizing fasciitis caused by a more virulent streptococcus A bacteria. 3) Because age is a factor in contracting these types of infections, an increase in cases is probable due to the aging population.

Case Study 1

Patient 1 was a 34-year-old immunosuppressed woman who presented with a right plantarflexion contracture of 30° that was due to a compartment syndrome. Three years earlier, the patient had experienced a posterior dislocation of the right knee that damaged the popliteal artery. During this time, she contracted a strep A infection in the affected limb that caused a compartment syndrome in the right lower extremity below the knee.

The infection required extensive debridement of the affected compartments, daily dressing changes, and skin grafts. She presented with zero dorsiflexors, zero evertors, and a grade 2 gastrocnemius. Because of the compartment syndrome, along with the subsequent debridements, she presented with severely limited range of motion in the right ankle and a 30° plantarflexion contracture. It is important to note also that her sensation was affected, although she did have light touch on the plantar surface of the foot.

The orthotic goals at this point included 1) independent gait in an AFO in the position of the ankle contracture to allow ambulation in the orthosis and possible reduction of the contracture with continued physical therapy, stretching, and ambulation and 2) strengthening of the hip and knee muscle groups on the involved side in the event future reconstructive surgery was indicated. Weight control was also attempted, as the patient weighed in excess of 275 pounds.

The orthotic treatment used was a right polypropylene, solid ankle AFO set in 30° of plantarflexion with a clamshell anterior panel. Due to the excessive plantarflexion contracture, a 2-inch heel elevation was added directly to her shoe. Also, in order to achieve an even pelvis with no leg length discrepancy, a heel lift was used on the contralateral side. Interestingly, she had undergone one attempt at soft-tissue release in the right Achilles, but this did not help lessen the degree of contracture.

Although this patient was able to ambulate independently using the AFO, she never mastered the gait because of her equinus deformity. Additionally, she never reduced her contracture, probably because of the scarring secondary to the infection and subsequent compartment syndrome.

After 1 trial year with the clamshell AFO, talectomy and fusion of the tibia on the calcaneus were accomplished. A new solid ankle AFO with a clamshell anterior panel was fabricated in order to attempt to off load the fusion and other foot joints while supporting the foot in the frontal plane. Because of the talectomy, a leg length discrepancy required a build-up to equalize limb lengths.

Case Study 2

Patient 2 was a 69-year-old diabetic woman who entered the emergency room complaining of excessive pain in her left lower extremity. She began noticing pain while leaving an athletic event where she was a spectator. Elevated muscle compartment pressure confirmed the beginning of a compartment syndrome. She was immediately taken to surgery, where she underwent debridement and fasciotomy of the left lower leg. During surgery, the left femoral compartment was explored and found to be infected also. The femoral compartment was subsequently debrided. She underwent daily dressing changes and skin grafts. Her limb was salvaged with full range of motion intact. Upon inspection, no portal of entry was found and tests confirmed the presence of the strep A bacteria.

Because of the more extensive debridement both above and below the knee, this patient, after the skin grafts, was left with a limited range of knee motion of 0° to 20° of knee flexion but no active extension control. A review of ankle motion revealed a solid contracture of 15° equinus, with a slight, fixed varus of the subtalar joint. Hip range of motion and strength were normal, but a slight leg length discrepancy made the involved side longer with the knee extended, due to the equinus deformity.

Because it was assumed that the joints and muscle strengths would probably not improve, a KAFO was custom fabricated with the knee locked in about 20° of flexion. This allowed the patient to progress with ambulation by rolling over the flexed knee while using a solid ankle AFO with rocker sole and an appropriate medial heel wedge to allow the foot to bear weight flat on the floor. Because of the captured knee flexion, a lift on the sound side was not necessary.

The two case studies have definite similarities, but they show two drastically different outcomes. Both patients were immunosuppressed in some fashion and both had compartment syndromes caused by the necrotizing fasciitis infection. The medical and surgical treatment for both patients consisted of debridements, fasciotomies, daily dressing changes, skin grafts, and antibiotics. These two cases are classic examples of the symptoms, treatments, and possible outcomes for people who have contracted necrotizing fasciitis.

Conclusions

As health professionals, it is important to be aware of the many pathologies that can cause weak and compromised extremities. Patients who experience weak and/or contracted limbs can definitely benefit from the use of an orthosis in ambulation. A person who has experienced a necrotizing soft-tissue infection will present with weakness and/or contractures that are comparable to what orthotists see daily. What orthotists might not be familiar with is the pathogenesis of necrotizing fasciitis and the treatment that the patient may endure. Due to the fact that the number of cases is on the rise and most likely will increase in the future, it is important to understand necrotizing fasciitis infection, its sequelae, and the role that the orthotist may play in its treatment.

DAVID SPEERS, CO, is a graduate of Northwestern University's Orthotic and Prosthetic Practitioner programs and is employed by Scheck and Siress in Oak Park, IL.

DONALD SHURR, CPO, PT, is Eastern District Manager for American Prosthetics and Orthotics in Iowa City, IA, and is the author of a textbook and numerous book chapters and publications on prosthetics and orthotics. Correspondence to: David Speers, 1145 Madison Street, Oak Park, IL 60302. Phone: (708) 383-2257; E-mail: D_SPEERS@prodigy.net.

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