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Osteomyelitis – Bad to the Bone

Osteomyelitis is a bone infection produced by bacteria. There are many causes of this infection, which is usually treated with antibiotics and in severe cases it may require surgery. The most common culprit of osteomyelitis is the action of pyogenic bacteria, a specific type of microbe that produces pus. However, it can also be caused by tuberculosis bacillus or even fungi. Bones are normally resistant to infections. However, microorganisms can penetrate the bone through blood or a penetrating wound.

“Signs and symptoms may vary depending on the category of infection, organism, anatomic location, and host. Hematogenous osteomyelitis occurs most often in prepubertal children and usually involves the metaphysis of long bones, particularly the tibia and femur. Patients usually present with signs of acute infection such as fever, chills, pain, and local signs of inflammation. In adults, the most common site is the vertebral bodies, followed by long bones, pelvis, and clavicle. The primary blood supply of the vertebrae is the segmental arteries, which divide to perfuse segments of two adjacent vertebrae. Thus, vertebral osteomyelitis often occurs in two contiguous vertebral bodies and the intervertebral disc.

In osteomyelitis due to a contiguous focus of infection without vascular insufficiency, patients often present with pain, fever, and purulent drainage from a traumatic or surgical wound. Infections involving prosthetic material may present later, and with more subtle findings.

In patients who develop osteomyelitis in the setting of vascular insufficiency, infection occurs most often in the small bones of the feet. These patients may experience minimal pain because of neuropathy. Physical exam frequently reveals evidence of neuropathy and compromised vascular supply (e.g. diminished pulses, poor capillary refill). The contiguous site of infection is typically a neuropathic ulcer, though it can be a paronychia, cellulitis, or puncture wound.”1

“Osteomyelitis consists of a wide range of inflammatory bone disorders caused by microbial infections or auto-inflammatory processes. As osteomyelitis can occur at different ages and at preferred localizations in the human skeleton, the incidence of osteomyelitis is approximately 1–2% in the United States and is more prevalent in developing countries with mortality rate as high as 2%. Bacteria responsible for osteomyelitis usually invade bone-forming osteoblasts, leading to pervasive inflammation, necrosis and bone destruction at the sites of infection. As often refractory to treatment and recurrent, osteomyelitis is considered one of the most challenging medical conditions for Orthopaedic surgeons. Meanwhile, Orthopaedic devices are the most common surgical devices associated with implant-related infections, and Staphylococcus aureus (S. aureus) is the most common causative pathogen in chronic osteomyelitis. Current treatment strategies for osteomyelitis involve surgical debridement and systemic and/or local antimicrobial therapies, the later can provide high concentrations of antibiotics at the infected site. However, effective treatment of chronic osteomyelitis using antimicrobial agents remains a significant clinical challenge. Furthermore, increasing numbers of osteomyelitis cases are caused by multiple infections or multi-drug resistant bacterial strains such as methicillin-resistant Staphylococcus aureus (MRSA), and possess even more formidable clinical challenges. Thus, there is an unmet clinical need to develop novel and effective strategies to combat osteomyelitis.”2

“There are two types of osteomyelitis: acute and chronic. Osteomyelitis is generally categorized as acute or chronic based on histopathologic findings, rather than duration of the infection. Acute osteomyelitis is associated with inflammatory bone changes caused by pathogenic bacteria, and symptoms typically present within two weeks after infection. Necrotic bone is present in chronic osteomyelitis, and symptoms may not occur until six weeks after the onset of infection. Further classification of osteomyelitis is based on the presumed mechanism of infection (e.g., hematogenous or direct inoculation of bacteria into bone from contiguous soft tissue infection or a chronic overlying open wound). The more complex Cierny-Mader classification system was developed to help guide surgical management, but is generally not used in primary care.”3

Acute Osteomyelitis

“Acute osteomyelitis develops within two weeks after disease onset, subacute osteomyelitis within one to several months and chronic osteomyelitis after a few months. Because osteomyelitis is a complex disease state, various classification systems have emerged beyond the general categories of acute, subacute and chronic. The Waldvogel classification system1-3 divides osteomyelitis into the categories of hematogenous, contiguous and chronic (Table 1).1 The more recent CiernyMader staging system is based on the status of the disease process, not etiology, chronicity or other factors (Table 2).4 The terms “acute” and “chronic”are not used in the Cierny-Mader system. The stages in this system are dynamic and may be altered by changes in the medical condition of the patient (host), successful antibiotic therapy and other treatments. Although the classification systems for osteomyelitis help describe the infection and determine the need for surgery, the categories do not apply to special circumstances (i.e., infections involving prosthetic joints, implanted materials or smaller bones of the body) or special types of infection (e.g., vertebral osteomyelitis).”4

It develops in less than two weeks. The main cause of acute osteomyelitis is the spread of an infection via the blood from another organ (or due to surgery) and into the bone marrow. The origin of the initial infection is not always known.

This type of osteomyelitis occurs mainly in people under 15 years of age and/or older than 50 and in patients with chronic diseases such as cirrhosis or diabetes. It can also be associated with the use of injected drugs.

The symptoms of acute osteomyelitis can vary greatly. These depend more on how severe or acute the infection is, the microorganism responsible and the location of the affected bones. It will also depend on the pre-existing diseases that the patient already has. The most common symptoms are: swelling, limitation of movement of the affected area and intense pain. Cellulitis, an inflammation of the subcutaneous cellular tissue and skin, may also be associated with osteomyelitis. Other less common symptoms might also include fever in conjunction with chills, general discomfort and weight loss.

It is very important to diagnose acute osteomyelitis in a timely manner, this because with proper antibiotic treatment bone necrosis can be avoided and the disease can be avoided to becomes chronic. Some of the exams that your physician or specialist may include are:

  • Blood cultures: is a test on the laboratory to check for bacteria or other microorganisms in the blood.
  • Bone biopsy: is an exam in which a piece of bone is removed and studied.
  • Bone scintigraphy: an imaging test used to diagnose bone diseases.
  • X-ray of the bones: it is an image examination on the bones.
  • Complete blood count (CBC): measures the number of red blood cells, white blood cells, the total amount of hemoglobin in the blood and the hematocrit.

Chronic Osteomyelitis

It generally develops in more than four weeks or doesn’t respond to antibiotic treatment, making it a long-term issue. If this is the case, surgery would be the most recommended solution. This type of osteomyelitis is mainly suffered by adults and occurs in tandem with: injuries (especially open fractures), surgical interventions and peripheral vascular pathologies (diabetic foot).

Microorganisms that cause this infection are gram positive bacteria such as streptococcus, Staphylococcus aureus and Clostridium botulinum. Other potential risk factors of osteomyelitis are the presence of joint prostheses, pseudomonas, anaerobic bacteria present in bugs bites, open fractures with dirty wounds and ischemia.

“Chronic osteomyelitis is a condition associated with potentially high morbidity and possibly mortality and has historically been very difficult to cure. Treatment is geared toward resolution of infection while maintaining optimal function in the patient’s extremity. Historically, treatment involved amputation, but with the emergence of antibiotics, patients could be managed with suppression. Patients treated in this manner failed treatment >30% of the time. With the advent of free flap technology and Ilizarov techniques, the failure rate has been reduced to approximately 10% to 15%. However, the key to successful eradication of infection remains thorough debridement of all infected and necrotic tissues. Although a variety of treatment options are available, no set guideline or algorithm is available for treating patients with chronic osteomyelitis.”5

Symptomatically, fever from chronic osteomyelitis may be low or even may not occur. Also, local symptoms such as pain, swelling and redness may be less visible at first. In some instances, fistulas may be formed in places where the purulent discharge is drained. Also, if the affected part is the spinal column, an epidural abscess may occur, resulting in compression of the spinal cord if the abscess grows large enough. In rare and more severe cases, the infection can spread to areas closed by the spine, forming what’s called a paravertebral abscess.

“Several predisposing factors for development of chronic osteomyelitis have been reported. A history of trauma, open fractures and surgery are the most commonly encountered factors. Other factors include diabetes, peripheral vascular disease, malnutrition, hypotension, chronic steroid use, malignancy, alcoholism, smoking, systemic or local immunocompromise, intravenous drug use and development of decubitus ulcers.

Nowadays, the presence of implants is one of the most important predisposing factors. Soon after implantation they become coated with the host’s proteins, an excellent source for attachment of pathogens. The biofilm they produce protects them from the host’s defense mechanisms so that they can re-activate months or years later.”6

“Because of the increasing numbers of implantations, infections associated with prostheses have become more common. More than a million hip replacements are done each year worldwide, and the number of other artificial joints (knees, elbows) inserted is also rising. Several experimental studies and early clinical experience have shown the high susceptibility to infection after insertion of prosthetic devices, even when microorganisms of low pathogenicity, such as Staph epidermidis or Propionibacterium spp, are present.12 There is general agreement that for hip surgery, an infection rate of less than 1% should be achievable; for other joints the rate is higher because of their proximity to the skin surface and the more limited experience in joint design. The risk of infection is highest during the first 2 years after implantation but persists at lower levels as long as the prosthesis remains in place. The economic burden to health-care systems associated with septic prosthetic joints is very high and has been calculated to be 5·3–7·2 times higher than for the primary operations. Prosthesis removal, which is necessary for cure in most cases, produces large skeletal defects, shortening of the limb, and severe functional impairment. Thus, the patient faces protracted stays in hospital, much financial expense, and, most distressingly, renewed disability and even death.”7

The treatment of osteomyelitis consists of halting and killing off the infection as well as reducing possible damage to the bone and adjacent tissues. For this, your physician or specialist may recommend antibiotics to eliminate the bacteria that is causing harm. Keep in mind that you can receive more than one antibiotic at a time. Antibiotics are usually taken for 4 to 6 weeks.

“The first role of antibiotics in the management of chronic osteomyelitis, is adjuvant therapy as part of a curative treatment strategy. The choice of antibiotic, in this setting, remains a very difficult one and there are many problems with the interpretation of ‘cure rate’ data. Firstly there are no standardized definitions for cure or failure of treatment and no universally accepted host stratification system. In addition, many of the historical studies evaluated the efficacy of antibiotics in the absence of surgical debridement or surgical implants. Studies often include a heterogeneous group of patients in terms of their physiological status, the etiological source of the infection and the anatomical/ pathological nature of the disease. Finally, in vivo effect does not always mirror the high degree of efficacy predicted by in vitro investigations. Empirical antibiotics should be selected on the basis of the etiology of the infection as well as local pathogen profiles. β-lactams and vancomycin are the most commonly used antimicrobials in the medical management of osteomyelitis.”8

At first, they are often administered intravenously, followed by being administered orally. This treatment may be sufficient in many cases of acute osteomyelitis but not all of course, it depends on the severity and other factors determined by the physician. However, in the case of chronic osteomyelitis, it may be necessary to opt for surgery since lots of damage may already be done.

 

References:

(1) Fritz, J. M., & McDonald, J. R. (2008). Osteomyelitis: approach to diagnosis and treatment. The Physician and sportsmedicine, 36(1), 50-54. Available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2696389/

(2) Lu, M., Liao, J., Dong, J., Wu, J., Qiu, H., Zhou, X., … & Quan, Z. (2016). An effective treatment of experimental osteomyelitis using the antimicrobial titanium/silver-containing nHP66 (nano-hydroxyapatite/polyamide-66) nanoscaffold biomaterials. Scientific reports, 6, 39174. Available online at https://www.nature.com/articles/srep39174

(3) Hatzenbuehler, J., & Pulling, T. J. (2011). Diagnosis and management of osteomyelitis. American family physician, 84(9), 1027. Available online at http://unmfm.pbworks.com/w/file/fetch/56796592/Osteomyelitis_AAFP.pdf

(4) Carek, P. J., Dickerson, L. M., & Sack, J. L. (2001). Diagnosis and management of osteomyelitis. American family physician, 63(12), 2413-2420. Available online at https://www.aafp.org/afp/2001/0615/p2413.pdf

(5) Parsons, B., & Strauss, E. (2004). Surgical management of chronic osteomyelitis. The American journal of surgery, 188(1), 57-66. Available online at https://www.americanjournalofsurgery.com/article/S0002-9610(03)00292-7/pdf

(6) Panteli, M., & Giannoudis, P. V. (2016). Chronic osteomyelitis: what the surgeon needs to know. EFORT open reviews, 1(5), 128-135. Available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5367612/

(7) Lew, D. P., & Waldvogel, F. A. (2004). Osteomyelitis. The Lancet, 364(9431), 369-379. Available online at http://www.acutemed.co.uk/docs/Osteomyelitis,%20Lancet,%2004.pdf

(8) Marais, L. C., Ferreira, N., Aldous, C., & Le Roux, T. L. B. (2014). The management of chronic osteomyelitis: Part II-Principles of post-infective reconstruction and antibiotic therapy. SA Orthopaedic Journal, 13(3), 32-39. Available online at http://www.scielo.org.za/pdf/saoj/v13n3/05.pdf

 

Robert Velasquez
9 August, 2018

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Hello everyone, my name is Robert Velazquez. I am a content marketer currently focused on the medical supply industry. I studied Medicine for 5 years. I have interacted with many patients and learned a lot...read more:

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