Osteomyelitis: definition, causes, symptoms, diagnosis and treatment

By Cristiano Antonino Last updated Jul 27, 2023

Osteomyelitis is an infection of the osteoarticular system which, if not properly treated, can become chronic

Although it can occur in any bone, it mostly affects bones rich in spongy tissue, i.e. those most vascularised.

It is more frequent in children, the elderly, and frail or immunocompromised individuals

The pathogens most commonly responsible are pyogenic (pus-producing) bacteria, more rarely mycobacteria and fungi; they generally reach the site of infection

through the bloodstream
coming from an infected neighbouring tissue;
coming from an open wound, thus including iatrogenic causes such as joint replacement or osteosynthesis of fractures, treatment of tooth roots or exposed bone fractures.

Following infection, white blood cells enter the site of infection in an attempt to eliminate the pathogen and release enzymes that cause damage and necrosis of the bone.

The pus enters the blood vessels of the bone, altering the flow and creating areas known as ‘bone sequestrations’.

In response to this event, the body will try to create new bone around the necrotic area, the so-called ‘bone envelope’.

Osteomyelitis can be acute, subacute, or chronic, the latter in cases where symptoms last for more than 6 weeks.

Chronic forms generally complicate with bone sclerosis and deformities, and are characterised by pathogens that are sometimes resistant to antibiotics and therefore difficult to treat.

Identifying the pathology and defining whether or not it is chronic allows the most appropriate therapy to be devised.

Osteomyelitis: the causes

Osteomyelitis can arise from various causes and with various mechanisms, the main ones being

infection by direct invasion
haematogenous spread from another site of infection
by contiguity (from neighbouring infections)

Infection by direct invasion occurs when the pathogen reaches the bone directly, e.g. during a surgical operation, following an exposed bone fracture or through piercing objects that have direct contact with the bone.

Some cases of osteomyelitis occur after implantation of bone prostheses or metal plates.

In the case of haematogenous spread, blood is the vector of infection and the pathogen most involved is Staphylococcus aureus.

Those most at risk are the elderly (at the level of the spine), children (at the level of the bony extremities of the legs and arms) and immunocompromised individuals such as dialysis patients, drug addicts and patients taking immunosuppressive therapies.

Finally, osteomyelitis can occur by extension from infected soft tissue surrounding the bone as in the case of trauma, surgery, ulcers, tumours or radiotherapy outcomes.

Again, immunocompromised and fragile individuals are most at risk.

Osteomyelitis: Symptoms

The symptoms of osteomyelitis depend on the site, extent and severity of the infection.

The main symptom of acute osteomyelitis is pain, which is throbbing and generally very intense, especially in cases of prosthetic infection.

In the case of vertebral osteomyelitis, the patient complains of back pain exacerbated by movement and unresponsive to analgesics.

The skin region corresponding to the infected bone site may be swollen and warm, and in some cases abscess formation may be observed.

Other typical symptoms of the acute forms are

weight loss
asthenia
pyrexia with chills
headache
fistula formation
fractures

Osteomyelitis, the diagnosis

In the case of suspicious symptoms (pain, pyrexia, chills, weight loss, asthenia) and suggestive signs (swelling, abscesses), it is necessary to promptly contact one’s doctor for further investigations.

Among these, blood tests will be the first step to highlight an infection, investigating ESR and CRP (C-reactive protein) whose levels may be elevated.

Subsequently, diagnostic tests such as X-ray, CT scan, MRI or bone scintigraphy will be prescribed, the last two being particularly indicated for making a diagnosis.

Osteomyelitis, treatments

Early antibiotic therapy or, in cases of fungal infection, antifungal therapy is essential; they can be administered orally or intravenously, and treatment generally lasts several weeks, initially with a broad-spectrum drug, subsequently optimised according to the pathogen identified.

The use of analgesic drugs for pain control combined with rest and, in cases of vertebral osteomyelitis, the use of a corset is also recommended.

In some cases, the specialist may deem surgery necessary to drain the abscesses or stabilise the vertebrae.

If treatment is timely, the prognosis for osteomyelitis is good.

More complex is the treatment of an infection involving the surrounding soft tissue, as the removal of dead tissue and, in some cases, the removal of the bone itself may be necessary.

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