Osteomyelitis

Introduction and Facts

Infection that occurs in the bone is called osteomyelitis. There are various types of osteomyelitis based on the duration, etiology, pathogenesis, degree of bone involvement, and the patient's age and immune system. The pathogenesis and risk factors of this condition have been studied intensively for the last thirty years, including the types of treatment. New surgical methods include muscle flaps, the Ilizarov technique, and antibiotic-filled beads for bone infections. However, the cure rate for osteomyelitis is still unsatisfactory, and it is still challenging to treat.

According to the duration of the disease, osteomyelitis is described as acute or chronic. In addition, according to the source of infection, osteomyelitis is classified as hematogenous if the infection originates from bacteremia and contiguous if it originates from infection of the surrounding tissue.

Pathophysiology/ Pathogenesis

source of infection. As mentioned earlier, hematogenous spread, direct inoculation of microorganisms into bone, and infectious foci of infection are the three main causes of osteomyelitis. Hematogenous osteomyelitis usually involves the metaphysis of long bones in children and other vertebral bodies in adults. The most common causes of direct inoculation osteomyelitis are penetrating injury and surgical contamination. Contiguous focal osteomyelitis usually occurs in patients with severe vascular disease.

The host factor is a defense against infections that occur in the bone. However, under some conditions, host factors may predispose individuals to the development of osteomyelitis. Lack of early infection containment can lead to more severe infections, e.g., three groups of patients with unusual susceptibility to acute bone infection are those with sickle cell anemia, chronic granulomatous disease, and diabetes mellitus.

Acute osteomyelitis. In the early period of acute disease, the vascular supply to the bone is reduced because of the extension of the infection to the soft tissues. Large areas of dead bone can form when the medullary and periosteal blood supply are both compromised. However, this condition of dead bone can be prevented if treated aggressively and appropriately with antibiotics and possibly with surgery. Fibrous tissue and chronic inflammatory cells will cluster around the granulation tissue, and dead bone after the infection has established. If the infection can be controlled, then the vascular supply around the area of ​​the condition will be reduced, resulting in an ineffective inflammatory response. Acute osteomyelitis, if not treated effectively, can lead to chronic disease.

Chronic osteomyelitis. The presence of necrotic bone, new bone formation, and exudation of polymorphonuclear leukocytes associated with other blood components are some of the pathological features of chronic osteomyelitis. The surviving periosteum and endosteum fragments at the site of infection form new bone. This includes the involucrum, the sheath of living bone that surrounds the dead bone beneath the periosteum. The involucrum is often perforated by holes that can drain pus into the surrounding soft tissue and drain onto the skin surface resulting in chronic sinus formation. It can also gradually increase its density and thickness to form some or all of the new diaphysis. Increase in the number and density of bone according to the size of the bone and the duration and extent of infection.

Clinical Features and Complications

Signs of acute infection such as fever, irritability, lethargy, and signs of local inflammation may occur in children. The soft tissue covering infected bone usually does not occur in children with hematogenous osteomyelitis because of the effectiveness of the response to infection. In general, patients may present with pain at the involved site, swelling, erythema, and drainage. Primary or recurrent hematogenous osteomyelitis in adults usually presents with vague complaints of nonspecific pain and low-grade fever, and sometimes acute clinical manifestations as in children.

In infectious osteomyelitis, patients may present with signs of bacteremia such as fever, chills, and night sweats, especially in the acute phase. Localized bone and joint pain and symptoms of inflammation around the infected area may also appear in the acute phase but not in the chronic phase. The chronic phase may develop from hematogenous or infectious osteomyelitis. Local bone loss, sequestrum formation, and bone sclerosis are common in chronic osteomyelitis. Local abscess and/or acute soft tissue infection may present as a sign of sinus tract obstruction.

Diagnosis

Acute general symptoms such as fever, toxemia, dehydration, at the affected bone heat and pain, throbbing due to suppressed pus, and signs of an abscess with swelling.

Laboratory Studies

In chronic inflammation, the erythrocyte sedimentation rate is usually elevated. However, the blood leukocyte count is usually within the normal range. The leukocyte count may be elevated in acute cases of osteomyelitis. The blood sedimentation rate usually returns to normal after full treatment. Therefore, interpreting an erythrocyte sedimentation rate that continues to increase during treatment is usually a good sign. Another indicator of inflammation that is elevated in acute and chronic osteomyelitis is C-reactive protein (CRP). It also decreased faster than the erythrocyte sedimentation rate within three days of antibiotic treatment. The leukocyte count, erythrocyte sedimentation rate, and CRP level should be monitored in patients on admission and during treatment and follow-up about once a week, especially in acute osteomyelitis.

Microbiology

Culture specimens of bone lesions and blood or joint fluid are performed to determine the etiology of osteomyelitis and establish the diagnosis. In stage 1 (hematogenous) osteomyelitis, according to Cierny-Mader, if there is radiographic evidence of osteomyelitis, and the results are positive on blood or joint fluid cultures, the need for a bone biopsy may be eliminated. In other types of osteomyelitis, antibiotic treatment should be based on bone cultures taken during debridement or deep bone biopsy.

Radiographic Findings

Lytic changes on radiographs can only appear when at least 50% to 75% of the bone matrix has been destroyed. This requires careful clinical correlation to achieve clinical relevance. Increased bone marrow density in the early stages of infection can be seen with computed axial tomography. In patients with hematogenous osteomyelitis, intra-medullary gas has been reported. A computed tomography scan can also identify necrotic areas of bone to demonstrate the involvement of soft tissue infection. One of the recognized functional modalities for diagnosing musculoskeletal infection's presence and extent is magnetic resonance imaging.

Management and Treatment

Management of osteomyelitis includes debridement to control infection and culture-directed antibiotic coverage. Underlying diseases such as diabetes should be given more attention as well. Therefore, efforts are made to improve the nutritional, medical, and vascular status of the patient and treat the underlying disease whenever possible. It requires a team approach, including plastic surgeons, infectious disease specialists, and other physicians.

Antibiotic Treatment

The duration of traditional treatment at each stage of osteomyelitis is 4 to 6 weeks, and bone revascularization after debridement is approximately four weeks. Empiric broad-spectrum antibiotics can be started if immediate surgical debridement must be performed before cultures can be obtained.

Although serum bactericide is generally associated with a successful outcome in treating osteomyelitis, it is not necessary to follow serum bactericidal levels because most treatment failures are due to inadequate surgical debridement rather than inadequate antibiotic efficacy.

Operative Treatment

The principles of treatment of any infection are:

• Adequate drainage.
• Extensive debridement of all necrotic tissue.
• Removal of dead space.
• Adequate soft tissue coverage.
• Restoration of an effective blood supply.

A. Reconstruction of Bone Deformities and Management of Dead Space Bone defects may occur after adequate debridement, called dead space. The goal of dead space management is to replace dead bone and scar tissue with durable vascularized tissue.

B. Bone Stabilization. Stabilization using plates, screws, rods, and/or external fixators should be performed if there is bony instability at the site of infection.

C. Software Coverage. Minor soft tissue defects can be covered with split-thickness skin grafts.

Additional Therapy

In animal studies, hyperbaric oxygen has shown effectiveness for treating osteomyelitis, but there are insufficient data.

Reference:

1. Rawung R, Moningkey C. Osteomyelitis: A literature review [Internet]. 2019 [cited 2021 Aug 31]. Available from: https://ejournal.unsrat.ac.id/index.php/biomedik/article/view/23317/23348

2. Osteomyelitis [Internet]. [cited 2021 Aug 29]. Available from: http://repository.unisba.ac.id/bitstream/handle/123456789/4792/06bab2_nadhirah_10100111083_skr_2015.pdf?sequence=6&isAllowed=y

3. Osteomyelitis [Internet]. [cited 2021 Aug 29]. Available from: http://eprints.ums.ac.id/16799/2/BAB_I.pdf