Infection
of bone and Joint
Osteomyelitis and septic arthritis remain a significant cause of
morbidity in paediatric practice. Prompt and adequate treatment is needed to
reduce the risk of complications. In some parts of the world tuberculosis is
still a serious problem; indeed there are signs it may be on the increase in the
Western hemisphere.
Bone
and joint infection is usually described in terms of acute, subacute or chronic.
No age is exempt from any type. Although there are classical forms of
presentation at different ages, skeletal infection can pose great problems in
terms of differential diagnosis. For example, trauma or sickle cell crisis can
be confused with acute osteomyelitis, benign or malignant bone tumours can mimic
subacute or chronic infection (Fig. 28.15) and other causes of inflammatory
joint disease, such as juvenile arthritis or irritable hip syndrome, have to be
distinguished from septic arthritis (Fig. 28.16).
Thus, bone and joint infection my present in many guises, from an acute
life-threatening condition to a painless deformity manifesting many years after
an unrecognised infection damaged the growth plate.
The treatment of skeletal infection is based on
the following principles:
• rest;
• elevation;
• surgical drainage;
• antibiotics;
• nutrition.
In
every case, all must be considered although not all may need immediate
implementation. For example, an early osteomyelitis may not require surgical
drainage or, in another case, antibiotics should be withheld until adequate
surgical clearance has removed infected, dead tissue and provided specimens for
culture and sensitivity. It is also vital to remember that when surgeons are
considering which antibiotic to give or whether a bone should be explored, the
importance of resting and elevating a limb, along with correction of nutritional
deficiency, including anaemia, must not be forgotten.
The
cause of skeletal infection is usually haematogenous spread from without the
body or from a septic focus within. In acute osteomyelitis the metaphysis is the
common site. Involvement of epiphysis or diaphysis is more often seen in
subacute or chronic infections.
Acute
infections
Septic
arthritis
The hip and knee are the commonest joints affected but the principles of
management apply to any joint.
It
is difficult to distinguish between septic arthritis of the hip and
osteomyelitis of the upper femur. The growth plate and metaphysis are
intracapsular and an early osteomyelitis can rapidly progress across the
metaphysis directly into the joint. In practice, especially in the neonate,
osteomyelitis and septic arthritis of the hip should be considered a single
entity.
The
usual cause of septic arthritis in any joint is haematogenous spread but direct
inoculation can occur, e.g. penetration of the hip during femoral venepuncture.
Neonates, the immunosuppressed and children with sickle cell disease are more
susceptible.
Bones
and joints can be involved as part of septicaemia, e.g. meningococcal. Diagnosis
is often delayed in the seriously ill child where attention is directed
towards the septicaemia.
Clinical
features. The diagnosis is straightforward when there are typical signs such as
tenderness, reluctance to move a limb (pseudoparalysis) and fever. In
superficial joints an effusion can be demonstrated and the joint is warm. In the
hip, ultrasonography is useful to show an effusion. Plain X-rays show this as
widening of the joint space (Fig. 28.17) and in severe cases there may be a
septic dislocation of the hip.
Treatment.
Blood should be taken for blood count, erythrocyte sedimentation rate (ESR)
and C-reactive protein. The joint should be aspirated. If pus is obtained or
there is any doubt, open surgical drainage and decompression of the joint is
indicated. In the hip, this is most easily done through an anterior approach. A
section of capsule is excised to ensure free drainage and the joint copiously
irrigated. Once
The
most common organisms are staphylococci and streptococci. In children under 4, Haemophilus
influenzae may be found.
If
the hip was subluxated or dislocated a hip spica should be applied to keep it
reduced. Otherwise bed rest is appropriate until the signs of infection,
combined with blood tests, are seen to be settling. In this regard it is easier
to monitor and treat a superficial joint, e.g. knee. Pus in a joint is
destructive. If treatment is delayed chondrolysis occurs. In the hip, this is
followed by avascular necrosis of the femoral head and ultimately limb
shortening due to dislocation (Fig. 28.18). A hip thus affected may come to
arthrodesis or trochanteric arthroplasty in which the unaffected greater
trochanter is placed in the acetabulum to stabilise the hip. Minor damage to the
growth plate may not show until late after the infection (Fig.
28.19).
Osteomyelitis
Clinical
features. Classically, the child is ill with signs of septicaemia. There is
local tenderness erythema and increase in local temperature. In severe cases the
whole limb is swollen, tender and hot, making localisation difficult.
Radiological appearances in osteomyelitis are normal in the early stages,
although a bone scan may be helpful.
Treatment.
Once pus is formed it must be surgically released. In the genuinely early case
(history less than 24
hours) treatment with antibiotics can be started after blood cultures
are taken. Provided there is a prompt response (24-48 hours) surgery may be
avoided. This approach may also be justified in early severe cases where
generalised swelling and tenderness of the whole limb makes localisation
difficult. In such cases it is advisable to take blood cultures, commence
resuscitation and' intravenous antibiotics, and wait 24—48 hours when
localising features will develop to direct the surgical approach.
When
surgery is required the periosteum is incised and any subperiosteal abscess
drained. If there is no subperiosteal abscess, the bone should be drilled to
drain any intraosseous pus. Postoperatively the limb should be rested in a cast.
Prolonged antibiotic therapy is necessary (at least 6 weeks) because it can be
very difficult to eradicate the
Apart
from chronicity, other possible late effects of osteomyelitis include overgrowth
of the limb due to stimulation of the growth plate or deformity due to growth
plate damage (Fig. 28.22a and b).
Acute
infection can affect the spine in childhood. It is often not suspected in a
toddler or child who may be generally well; backache, stiffness and a limp are
alerting signs. X-rays show disc space narrowing and an MRI scan will highlight
the inflamed area. A CT-guided biopsy will probably show infected tissue but it
is common that culture is negative or inconclusive. Rather than exploring and
draining the spine it
The epiphysis is a relatively common site. The diaphysis can also be
affected. The clinical features are much less marked than with acute infections
and diagnosis is often delayed. Radiographs may show a sclerotic wall around a
cyst or in many cases sclerosis may be the only feature. A bone scan may be
helpful to distinguish from quiescent harmless bone lesions. In cases where
sampling a lesion may be difficult because of its anatomical location or lack of
clear definition on radiographs a conservative approach with antibiotics may be
indicated. If there is no response, biopsy is indicated to exclude a tumour.
Irritable
hip
This is also known as transient synovitis or observation hip. It is
essentially a diagnosis of exclusion — most importantly from septic arthritis.
It is a common condition in which the child, usually between 4 and 8 years old,
presents with pain in the hip of variable severity, reluctance to weight bear
and a limp. The cause is usually unknown but there may be a history of preceding
trauma or a viral infection. The clinical features vary from a well child with
minor loss of movement to the unwell child with a low-grade fever and marked
stiffness.
Systemic
examination may reveal lymphadenopathy or other evidence of a viral infection,
such as a rash. Radio-graphs are normal or may show slight widening of the joint
space. The blood count is normal and the ESR may be minimally raised. The
presence of fever, effusion and marked stiffness would be an indication to
investigate as a septic arthritis. This would only apply to a minority of cases.
The great majority settles with bed rest followed by mobilisation as the hip
becomes comfortable
Skeletal
tuberculosis
This may present as chronic arthritis (Fig.
28.23) or osteomyelitis.
In
the spine it usually involves the adjacent parts of the bodies of two vertebrae.
The disc is relatively resistant to tuberculosis but eventually undergoes
avascular necrosis although it may sequestrate. Abscesses can spread in various
directions by stripping the vertebral ligaments. In the lumbar region, a
paravertebral abscess may enter the psoas sheath to appear in the femoral
triangle. Clinical features include general malaise, backache and stiffness. The
principal complications of spinal tuberculosis are paraplegia and deformity.
Paraplegia may occur early or late in the disease. Early paraplegia is usually
due to mechanical pressure on the cord from granulation tissue, pus,
sequestrated disc material or oedema; ischaemia can also be a cause. Late
paraplegia is usually associated with stretching of the spinal cord over an
angular deformity, resulting in ischaemia. The usual deformity in spinal
tuberculosis is a kyphosis due to collapse of the vertebral bodies. As with
other forms of skeletal tuberculosis, treatment should be with appropriate
antibiotics. However, it has been shown that, although conservative treatment is
effective, there is a risk of a deterioration in the kyphosis and that this is
most likely to occur in children and when several vertebrae are involved.
Radical anterior débridement and spinal fusion will usually prevent any
progression of the deformity.