Osteomyelitis

Introduction

Thousands and millions of infectious diseases surround us; some cause harm while others do not. Any organism that gains entry inside our body can end up causing damage to the cells, and such is the case with people who suffer from Osteomyelitis.

Osteomyelitis is one of the rare disorders of the body involving the bones, soft tissues, joints, and muscles. The infection causes inflammation of the bones and the bone marrow that develops osteomyelitis. This organism can either gain access through blood (Hematogenous spread), break in the skin, from an implant of a prosthetic bone, or insufficient vascular supply.

Osteomyelitis is a painful bone infection that damages the affected bone. The damage is to the extent that the whole surrounding tissue undergoes necrosis and has to be debrided, which is a surgical procedure to scrape off the dead tissue. This is performed when the acute stage turns into chronic osteomyelitis.

Osteomyelitis can present very early as an acute or very late as chronic osteomyelitis. Soft tissue infection is usually superseded after the bone infection. The prognosis and recovery from Osteomyelitis depend significantly on the duration of the infection. Most people who get Osteomyelitis have a compromised immune system, such as individuals with HIV and sickle cell disease. It can be present in the body’s long or small bones. Measures can be taken to prevent osteomyelitis, and most involve safe, sanitary practices in routine and by orthopaedic surgeons.  [1]

Pathophysiology

Individuals who develop osteomyelitis are 1-3% in the world. Infection of the bone is not very easily acquired. Organisms cannot quickly gain entry as the bone is highly resistant to such invasions. Therefore, a massive colony of bacteria is required to cause Osteomyelitis which can also be due to any local infection. Bacteria produce proteins on their cell surface that tightly bind to the bone. This attachment is further strengthened by a biofilm produced by the bacteria, which prevents any antimicrobial agent that can kill or sloughing off that bacteria.

Osteomyelitis starts by infecting the medullary cavity and then extends and reaches the cortical bone, eventually invading the periosteum of the bone. That results in oedema in the bone marrow spaces and compression of blood vessels supplying oxygen to the bone.

The compression leads to the cessation of blood flow toward the bone resulting in necrosis (bone death). That results in the formation of a sequestrum. Since it is a non-living dead tissue, it further allows the bacteria to thrive and increase its population.

As the body senses the presence of a foreign organism in the body, it activates the immune response. This immune response releases cytokines which are specialized cells that tend to destroy bacteria by producing toxic oxygen radicals. These radicals end up harming the osteocytes (cells of the bone) even further. [2]

Types of Osteomyelitis

Osteomyelitis is divided into two categories. The prognosis and type depend on the progression and on the duration of Osteomyelitis (acute and chronic Osteomyelitis). These different types are as follows;

Mechanism of infection

Hematogenous Osteomyelitis

This type of bacterial Osteomyelitis occurs mainly due to a blood infection seen mainly in children; long bones are more commonly affected in this type of osteomyelitis. The infection travels from the blood, and bone involvement is seen.

It involves the metaphysis of the bone, the nearest landmark for the bacteria to attack from the blood vessels. It is more likely to occur injury to the bone. Most patients with Osteomyelitis through the hematogenous route have a weakened immune system or suffer from chronic diseases, and osteomyelitis progresses to the tissues outside the bone. Early detection and therapy lead to a better prognosis of osteomyelitis with prompt surgical interventions. The common organism causing this type of Osteomyelitis is Staphylococcus aureus, along with some respiratory infective organisms such as Streptococcus species. [3]

Anaerobic/contiguous Osteomyelitis

This type of Osteomyelitis is due to bone graft, which brings anaerobic bacteria inside the body. Anything that disrupts the normal blood flow to the bones can increase the likelihood of anaerobic Osteomyelitis. Some processes, such as traumatic injury, diabetes mellitus, malignancy or other metabolic disorders, can all result in anaerobic bacteria infection. These bacteria enter through the skin flora or the mucous membranes where these organisms reside. The long-term effects result in chronic bone infections, soft tissue infections, joint infections, permanently damaged bones, and uncomplicated fractures. [4]

Vascular insufficiency osteomyelitis

Patients who suffer from vascular pathologies are prone to getting Osteomyelitis. It usually occurs in the small bones of the feet. Due to their immunocompromised state, these individuals do not experience pain; therefore, it gets masked. These individuals have low capillary refill due to the decreased blood supply presenting with diabetic foot and necrotic bone. [5]

Vertebral Osteomyelitis

It is also known as spinal Osteomyelitis, which is rare to acquire. Individuals who get this bone infection are usually due to a pathogen from the blood travelling towards the vertebral bodies. The staphylococcus species are majorly responsible for this infection. The factors of Osteomyelitis include an immunocompromised state of the body, diabetes mellitus, injury, long-term use of steroids, or any malignancy. Osteomyelitis involving the vertebral column also compromises the function of the spinal cord, causing chronic back pain. This back pain is not relieved by either rest or pain relievers and requires an appropriate dosage of antibiotics to get rid of the organism causing the illness.

It can also occur due to surgeries of the vertebral column, enabling the pathogens to gain entry inside the body and compress the spinal column causing paralysis of muscles. [6]

Duration of infection

Acute Osteomyelitis

Acute Osteomyelitis is a bone infection that presents symptoms within one month of acquiring the infection. The signs include accumulation of fluid (oedema), pus collection, and thrombosis of small vessels, including the vessels in the bones of the arms. The major complaint of most individuals with osteomyelitis diagnosed is bone pain.

Chronic Osteomyelitis

Pyogenic chronic Osteomyelitis is a bone infection caused by the staphylococcus species that recurs as acute cases in a minimum of three months. This state is characterized by large ischaemic areas, bone death and the formation of sequestrums [7]

Risk factors

Individuals developing osteomyelitis can be of any age. The risk factors that predispose to staphylococcus aureus infection are as follows;

1.      Prior Bone surgery– Due to any nicks or incisions made to the skin, it becomes a straightforward route for the pathogens to enter the body and cause joint and bone infections, commonly termed septic arthritis. Therefore, anyone with prior bone surgery or any open wound has a risk factor of acquiring the infection.

2.      Individuals with catheters placed- Someone having a urinary tract infection carries the body’s normal flora to the inside resulting in septic arthritis leading to osteomyelitis.

3.      Vascular disorders- Patients with diabetes, peripheral artery disease or sickle cell disease are at a higher risk of acquiring Osteomyelitis than the ones who do not have these medical conditions. 

4.      Chronic diseases and pressure injuries- Bedbound people get bedsores and are at a higher risk of getting osteomyelitis. Those suffering from other joint disorders, such as rheumatoid arthritis, are also more likely to get osteomyelitis than those who don’t.

Signs and Symptoms of Osteomyelitis

The signs and symptoms of Osteomyelitis are listed as follows;

The signs and symptoms depend on the acute and chronic infection. Acute osteomyelitis infections are associated with the infected area having painful joints that are swollen and red. Moreover, there is sometimes pus, fever, weakness, back pain, nausea, vomiting and loss of appetite.

Diagnosis

The diagnosis of Osteomyelitis is made after taking a detailed history of the individual, which includes any surgery, traumatic injury or metabolic diseases. After that, a physical exam is conducted to check the mobility of the affected joints, which aids in diagnosing osteomyelitis.

To confirm the susceptibility of an osteomyelitis infection, further tests are performed, such as;

·         Blood cultures– These blood tests are sent once systemic manifestations are seen in the patient.

·         Radiographic tests- such as X-Rays, Ultrasound, CT-Scans and MRI (Magnetic Resonance Imaging) should be done on the infected bone.

·         Bone scans– Radioactive material is injected that helps recognize fractures or infections of the bones.

·         Bone Biopsy– The best diagnostic test is the bone biopsy which confirms the possibility of a staphylococcus aureus infection in the bones of the infected tissue. [8]

Treatment

Osteomyelitis treatment requires antibiotic therapy or the use of antifungals that are sensitive to the organism that has caused the bone infection. The selection of antibiotics is based on the blood culture report, which shows the inoculated organism. Most Staphylococcus bacteria are responsible for this condition; antibiotics such as penicillins are the first line of treatment for such cases.

The antibiotic treatment lasts seven days to help the body eliminate the bacterial infection. Moreover, pain relievers are given to help manage the bone pain, and fine needle aspiration is done to help drain the fluid accumulated inside the joint surfaces. The bone scan helps decide the treatment option, which helps indicate whether the person requires surgical interventions or not.

When medical treatment does not work to eliminate the infection, orthopaedic surgeons go for surgical interventions to treat osteomyelitis in the affected area. Long bone infections are, therefore, limited. Bone, spine, and joint surgery are the last interventions to treat osteomyelitis completely. [9]

There are also ways to prevent osteomyelitis, such as cleaning wounds after trauma to the skin surface. Osteomyelitis can permanently damage bones; hence, it is best to prevent it by using safety measures.

References

1.      Birt, M. C., Anderson, D. W., Toby, E. B., & Wang, J. (2017). Osteomyelitis: Recent advances in pathophysiology and therapeutic strategies. Journal of Orthopaedics, 14(1), 45-52. https://doi.org/10.1016/j.jor.2016.10.004

2.      Calhoun, J. H., Manring, M. M., & Shirtliff, M. (2009). Osteomyelitis of the Long Bones. Seminars in Plastic Surgery, 23(2), 59–72. https://doi.org/10.1055/s-0029-1214158

3.      Jaramillo D, Dormans JP, Delgado J, Laor T, St Geme III JW. Hematogenous Osteomyelitis in infants and children: imaging of a changing disease. Radiology. 2017 Jun;283(3):629-43.

4.      Espinosa, C. M., Davis, M. M., & Gilsdorf, J. R. (2011). Anaerobic Osteomyelitis in Children. The Pediatric infectious disease journal, 30(5), 422. https://doi.org/10.1097/INF.0b013e318217ca0e

5.      Osteomyelitis (bone infection): Causes, symptoms & treatment. Cleveland Clinic. (n.d.). Retrieved October 18, 2022, from https://my.clevelandclinic.org/health/diseases/9495-osteomyelitis 

6.      Graeber A, Cecava ND. Vertebral Osteomyelitis.

7.      Panteli, M., & Giannoudis, P. V. (2016). Chronic Osteomyelitis: what the surgeon needs to know. EFORT Open Reviews, 1(5), 128-135. https://doi.org/10.1302/2058-5241.1.000017

8.      Hatzenbuehler J, Pulling TJ. Diagnosis and management of osteomyelitis. American family physician. 2011 Nov 1;84(9):1027-33.

9.      Fritz, J. M., & McDonald, J. R. (2008). Osteomyelitis: Approach to Diagnosis and Treatment. The Physician and sportsmedicine, 36(1), nihpa116823. https://doi.org/10.3810/psm.2008.12.11