Osteomyelitis

Osteomyelitis is infection of the bone and the bone marrow. Bone looks impregnable, yet germs reach it by three routes: through the bloodstream, from a neighbouring wound or ulcer, and directly through a fracture or an operation. What matters about this illness is not how common it is but how quickly its outcome changes: an infection recognised in the first few days is usually cured outright with antibiotics, while one that is allowed to run turns into a story of years, with operations and discharging sinuses. Severe bone pain with a high temperature is therefore not something to leave until Monday.

How germs reach the bone

The first route is the bloodstream. Bacteria enter the circulation from any focus: a boil, a bad tooth, an infected line, sometimes after an ordinary chest infection or after chickenpox in a child. In children they settle in the growth zones of the long bones — thigh, shin, upper arm. In adults the favourite site is different: the vertebrae. Spinal osteomyelitis creeps up quietly, often without a high temperature, and for months it is taken for ordinary back pain.

The second route is from next door. Infection spreads into bone from a foot ulcer, a pressure sore or deep suppuration in the soft tissues. This is the commonest route in adults.

The third is direct inoculation: an open fracture, a deep puncture wound, surgery, especially where a plate, a nail or a joint replacement has been put in. Metal does not cause infection by itself, but bacteria form a film on its surface that antibiotics struggle to penetrate.

Who is more at risk

Anyone can develop osteomyelitis, but the risk is higher with:

• diabetes, particularly with an ulcer or a wound on the foot that will not close;
• poor circulation in the legs — narrowed arteries, smoking;
• a recent fracture, a deep wound, a bite, surgery on bone;
• an artificial joint, a plate or a nail;
• a weakened immune system: treatment that suppresses it, chemotherapy, HIV, long-term steroids;
• sickle cell disease;
• injecting drug use and long-term vascular lines, including those used for dialysis;
• osteomyelitis in the past — it is capable of returning years later.

Acute and chronic infection

Acute osteomyelitis develops over days. A deep, constant, boring pain appears at one point in the bone; it does not settle with rest and it prevents sleep. Then come:

• swelling, warmth and redness over the area;
• fever, shivering, weakness, loss of appetite;
• inability to put weight on the leg; in a child this often shows simply as a limp or as refusing to use an arm;
• where a vertebra is involved, back or neck pain that is worse at night and tenderness when the spine is tapped.

In small children and in older people the picture can be blurred: the child is simply unsettled, will not eat and will not let the limb be touched, while an older person may have no fever at all.

Chronic osteomyelitis looks different. A dead fragment remains inside the bone, reached by neither blood nor medicine. The pain becomes dull and comes in waves, the temperature is low or absent, and a sinus opens through the skin — a narrow track from which pus drains from time to time. Quietening and flaring, this can go on for years.

When it cannot wait

Get medical help the same day, and call an ambulance if the person is seriously unwell (112 is the single emergency number across much of Europe), if:

• severe pain in a bone or joint comes together with a high temperature and shivering;
• the leg cannot be stood on, or a child is limping or has stopped using an arm;
• a wound, a surgical scar or a foot ulcer becomes painful, red or starts to discharge;
• back or neck pain comes with fever, especially in someone with diabetes or after recent surgery or infection;
• weakness in the legs, numbness around the genitals and back passage, retention of urine or incontinence appear — an abscess pressing on the spinal cord needs help immediately;
• there is confusion, a racing pulse, cold clammy skin or fast breathing, all signs of blood poisoning.

What not to do: apply heat to the area, open or squeeze a collection of pus yourself, or start leftover antibiotics from the cupboard. Taken blindly they blur the picture and stop cultures identifying the germ, while doing nothing to clear infection inside bone.

How it is confirmed and what it can be mistaken for

The doctor examines the area, works out exactly where the bone hurts and arranges blood tests: the inflammatory markers matter, and so does their level, which later shows whether treatment is working. Blood cultures are taken before antibiotics are started, and they often name the organism.

One thing is worth knowing about imaging: a plain X-ray looks normal for the first week and a half to two weeks, because bone changes only become visible once a substantial part of the bone has been lost. A normal X-ray does not rule osteomyelitis out. Where the condition is suspected, an MRI scan is therefore performed, since it shows marrow oedema and soft tissue abscesses from the earliest days. A CT scan is used to see dead fragments of bone before an operation.

The decisive test is a bone biopsy: a piece of bone tissue is taken and sent both for culture and for microscopy. A swab from a sinus or a wound will not do, because it grows the bacteria that live on the skin surface rather than the one sitting inside the bone.

Other conditions can look similar and are treated quite differently: septic arthritis of the neighbouring joint, cellulitis and erysipelas, a stress fracture in a runner, a bone tumour in a child or teenager, a painful crisis in sickle cell disease, and the Charcot foot of diabetes, in which the bones of the foot break down with no infection at all.

Antibiotics: how long and why

Treatment rests on antibiotics chosen according to the cultures. They are usually started into a vein in hospital; once the person improves and the inflammatory markers fall, much of the course can often be continued as tablets at home, which with modern regimens is no worse than a drip.

The course is long: as a rule four to six weeks, and longer where vertebrae are involved or a replacement joint is infected. The reason is that bone has a poor blood supply and the drug needs time to build up in the focus. Stopping as soon as you feel better is not an option: a half-treated infection retreats deeper and comes back as the chronic form.

Besides antibiotics you need pain relief, rest for the affected limb — sometimes in a splint — and, in diabetes, tight control of blood glucose, without which no regimen works. If the infection is caught in the first few days it most often clears completely.

When an operation is needed

Antibiotics alone are not always enough. Surgery is needed if:

• pus has collected in or beside the bone and has to be drained;
• infection has already destroyed part of the bone and left it dead;
• an abscess is pressing on the spinal cord or a nerve;
• the focus involves a plate, a nail or a joint replacement;
• the disease has become chronic, with a sinus and repeated flare-ups.

The core operation is removal of all dead and infected tissue back to healthy, bleeding bone. That leaves a cavity, which is filled: with a bone graft, with material that releases antibiotic, or with a muscle flap that brings its own blood supply. Several operations are sometimes required, and infected metalwork usually has to come out and be replaced once the infection has been beaten.

If you have diabetes: the foot needs particular attention

More than half of adult osteomyelitis begins in a diabetic foot ulcer. Nerve damage leaves the foot without sensation, so a callus, a rub from a shoe or an unnoticed cut does not hurt; the person keeps walking, the wound deepens and reaches bone.

What is worth doing:

• check the feet every day, including between the toes and the sole, using a mirror if necessary;
• never walk barefoot, and feel inside your shoes with a hand before putting them on;
• do not cut away hard skin or use acid corn plasters;
• show a doctor any wound that has not closed in two weeks, and show a deep, foul-smelling one or one with bone visible straight away;
• keep glucose and blood pressure to target and stop smoking: without blood flow a wound will not heal.

One sign worth knowing: if an ulcer is deep and a probe reaches a hard base, osteomyelitis is likely even when the person feels reasonably well.

Online consultation

Osteomyelitis is treated in person, but talking remotely first saves time. From your account the doctor will judge how worrying the picture is, say whether you need to go in today and where, and explain which tests will be informative and which will show nothing at this stage.

What to prepare: when the pain started and how it has changed, whether there has been fever and how high, whether you have diabetes, any previous surgery on bone or joints, any metalwork or joint replacements, and what treatment you have already had. Photographs of the wound or ulcer in good light with a ruler beside it help to track progress.

A long course is convenient to run online too: discussing how well the antibiotics are tolerated, dealing with side effects, checking that inflammatory markers are falling, and noticing early if improvement has stalled. If there are signs of pressure on the spinal cord, of blood poisoning or of rapidly spreading infection, the consultation stops and you are sent to hospital.

This material is for information only and does not replace medical advice.