How does Osteomyelitis develop?
Surgical and antibacterial: Two routes for Osteomyelitis treatment
What is the duration of antibiotic therapy?
References
Further reading
Osteomyelitis is an inflammation of bone marrow that begins as a bacterial infection and can cause significant bone damage.
The condition tends to progress to an area surrounding the bone known as the periosteal, a membrane of several thick cell layers covering almost all bone in the body except for the areas covered by cartilage.
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How does Osteomyelitis develop?
There are several subdivisions of Osteomyelitis. However, Osteomyelitis typically occurs via the hematogenous route (blood-borne), contiguous route (spread from adjacent bone), or via the bone, which can become directly inoculated via trauma or surgery.
In hematogenous Osteomyelitis, bacteria seed in the bone at a site distant from the source of infection and spread by the circulatory system from surrounding tissue and joints. Hematogenous Osteomyelitis is more prevalent in children than adults, with long bones typically affected. In adults, the vertebrae are most commonly affected.
Contiguous Osteomyelitis in young adults occurs in the context of any trauma to the bone and related surgery. In contrast, in older adults, infection is typically associated with decubitus ulcers (a pressure ulcer, bedsore, or pressure sore) and infected joint arthroplasties (the articular surface of a musculoskeletal joint is replaced, remodeled, or realigned).
Hematogenous Osteomyelitis is frequently monomicrobial; however, contiguous-spread Osteomyelitis and Osteomyelitis caused by direct inoculation are typically polymicrobial, although they can be monomicrobial. The most commonly observed bacteria species depends on the patient’s age.
In both adults and children, Staphylococcus aureus is the most common cause of acute and chronic forms.
Increasingly, due to microbial resistance, Methicillin-Resistant Staphylococcus Aureus (MRSA) has been observed; some studies have reported over 1/3 of all Staphylococcal isolates are MRSA. Other common pathogens found in the infection include:
- Coagulase-negative staphylococcus
- Beta-hemolytic streptococcus
- Enterococci
- Aerobic gram-negative bacilli (including Pseudomonas species, Enterobacter species, Escherichia coli)
- Anaerobic gram-negative bacilli (such as Peptostreptococcus, Clostridium species, Bacteroides)
Less common pathogens are particularly relevant to patients who are immunocompromised and include mycobacterium tuberculosis, which may spread from the lungs to the spine, non-tuberculosis mycobacteria, Candida species, and fungi such as Blastomyces, Coccidiodes, Cryptococcus, and Aspergillus.
In addition, in immunocompromised patients, there is an association between the species of bacteria and the nature of the immunocompromising disease:
- Salmonella and S. aureus are associated with hematogenous Osteomyelitis in sickle cell disease
- Bartonella henselae may be associated with HIV-related Osteomyelitis a
- Pasteurella multocida or Eikenella corrodens may be observed in bites
Surgical and antibacterial: Two routes for Osteomyelitis treatment
Treatment of Osteomyelitis is not simplistic and may involve interdisciplinary collaboration between surgical and medical specialty teams. The two overarching therapy goals are surgical containment of infection and prolonged treatment with antibiotics.
Surgical intervention is necessary to remove all diseased bone because antibiotics are poorly penetrative – they cannot access sites of infected fluid accumulation, such as abscesses and injured or necrotic bone.
Consequently, when it is visible, necrotic tissue and bone are removed surgically. This type of surgery is called debridement, the removal of damaged, dead, or infected tissue to improve the healing capabilities of the remaining healthy tissue.
To delineate the extent of infection, imaging technologies such as MRI are used preoperatively; moreover, pathology reports are used to determine whether surgical debridement is, in fact, necessary.
In cases where surgical intervention is needed, it is difficult for surgeons to determine whether successful removal of all necrotic bone has occurred during surgery.
In cases where a prosthesis is infected in a stable joint such as the hip and happens to be infected with antibiotic-susceptible organisms such as streptococci, it is sufficient to treat patients with an extended antibiotic course over several months without needing to remove the prosthesis.
When prosthetic removal is necessary, a particular type of arthroplasty called a two-stage exchange arthroplasty is employed, reducing the risk of recurring infection relative to one-stage arthroplasty. This is particularly true when more virulent bacteria, such as Staphylococcus aureus.
In a two-stage exchange, the infection is first cleared, and subsequent reinsertion of a new joint replacement occurs. One-stage exchange arthroplasty is similar to the two-stage procedure, but the interval between removing the prosthesis and reimplanting a new one is only a few minutes.
Suppose surgical debridement is not possible (as is the case with anatomically difficult to operate on sites such as the pelvis). In that case, extended antibiotic therapy over several months may be the treatment choice.
In the case of native vertebral Osteomyelitis, known as hematogenous Osteomyelitis, surgical debridement is rare except if there are neurological complications that require relief of spinal cord compression or in the failure of medical treatment or in cases where abscesses need to be drained.
An important consideration for surgical intervention is the need for revascularization as there is evidence of peripheral vascular disease diabetes underneath to address other factors that can compromise wound healing, such as the use of tobacco, state of immunodeficiency, chronic lymphoedema, malnutrition, and peripheral neuropathy.
Outside of surgical intervention, prolonged antibiotic therapies are considered the gold standard for treating Osteomyelitis.
Results of culture experiments comma guide the type of antibiotic treatment. Still, without knowing, it is reasonable to begin treatment with empiric antimicrobial therapy/ Empiric antimicrobial therapy is given when a proven or suspected infection has been determined. Still, the causal pathogens are unidentified/ to be identified.
The most common type of empiric antibiotic therapy is a broad-spectrum empiric antibiotic regimen that targets gram-positive and gram-negative microorganisms.
One regimen typically used includes vancomycin, a third-generation cephalosporin, or a beta-lactam/ beta-lactamase inhibitor combination.
When the causal pathogens are known, directed therapy is employed; consequently, antibiotic therapy for Osteomyelitis is pathogen-specific, and antibiotic treatment is differential.
HOW TO TREAT OSTEOMYELITIS FAST - OSTEOMYELITIS TREATMENT AND RISK FACTORS
What is the duration of antibiotic therapy?
Treatment for Osteomyelitis in adults typically occurs between four and six weeks of parenteral antibiotic therapy. This results in acceptable rates of cure with a decreased risk of recurrence.
Antibiotic therapy can be shortened when the infected bone is wholly debrided or amputated with clean, disease-free margins. Typically, a two-week course of antibiotics is sufficient post-operation to treat any residual tissue infection and for the wound of the surgical site to heal.
Antibiotic treatment is critically important to prevent subsequent complications, including septic arthritis, squamous cell carcinoma, pathological fractures, Abscess formation, systemic infection, bone deformity, and contiguous soft tissue infection. In rare cases, amyloidosis may occur.
To improve healing, vacuum-assisted wound closure devices may be used in the clinical setting allows for this. This is especially useful where large or deep wounds remain after extensive debridement.
It is critically important to successfully resolve Osteomyelitis, especially for close follow-up with prolonged antibiotics and dedicated wound care. Infectious disease specialists are often involved in patient care and can monitor response to therapy, subsequently adjusting antibiotic regimens if and when necessary.
Parenteral (non-oral means of administration) antibiotics are other preferred modes of treatment, and many patients can continue with this means of administration in the outpatient setting via a peripherally inserted intravenous access.
Some patients may transition to bioavailable oral antibiotic therapy if feasible, depending on microbiological results.
References
- Schmitt SK. (2017) Osteomyelitis. Infect Dis Clin North Am. doi: 10.1016/j.idc.2017.01.010.
- Lew DP, Waldvogel FA. (1997) Osteomyelitis. N Engl J Med. doi: 10.1056/NEJM199704033361406.
- Zimmerli W. (2010) Clinical practice. Vertebral Osteomyelitis. N Engl J Med. doi: 10.1056/NEJMcp0910753.
- Berbari EF, Kanj SS, Kowalski TJ, et al. (2015)Infectious Diseases Society of America. 2015 Infectious Diseases Society of America (IDSA) Clinical Practice Guidelines for the Diagnosis and Treatment of Native Vertebral Osteomyelitis in Adults. Clin Infect Dis. doi: 10.1093/cid/civ482.
- Dutra LMA, Melo MC, Moura MC, et al. (2019) Prognosis of the outcome of severe diabetic foot ulcers with multidisciplinary care. J Multidiscip Healthc. doi: 10.2147/JMDH.S194969.
Further reading