Orthopaedic problems in children

This Update discusses the diagnosis of several orthopaedic conditions in children. It is by Professor Dominic Fitzgerald, MBBS, PhD, FRACP.

Professor Dominic Fitzgerald MBBS, PhD, FRACP
Professor Fitzgerald is a paediatric respiratory and sleep physician at the Children’s Hospital at Westmead, NSW.

INTRODUCTION
ORTHOPAEDIC presentations are common in general practice.
Often, the more obvious traumatic injuries do not present a diagnostic problem, yet there are some conditions that may require review and further assessment in order to make the correct diagnosis.

A number of conditions where diagnostic delay can have long-term consequences are discussed in this Update.

INFECTION IN THE BONE OR JOINT
Osteomyelitis
Osteomyelitis is common in children and may present in an insidious fashion. Typically, it is located at the junction of the metaphysis and the epiphysis of the bone, as this is the site of haematogenous spread of pathogens during bacteraemia.

In addition, osteomyelitis may occur from a direct penetrating wound to bone with super infection, or as a result of direct spread from an infective lesion.

Osteomyelitis may present with localised tenderness over the area, usually the metaphyseal region of a bone. There may be pain and refusal to use the limb, or to walk, if the lower limb is affected.

Younger children may simply have fever and irritability without a clear localising focus of infection. Fevers, if present, may often be low-grade rather than high-spiking fevers as might be seen with a large collection of pus in an abscess or empyema.

If located near a joint there may be joint swelling, which makes it difficult at times to differentiate osteomyelitis from septic arthritis.

The more common pathogens are Staphylococcus aureus, Group A streptococci, Streptococcus pneumoniae and gram-negative organisms including salmonella, Escherichia coli and Klebsiella. Salmonella may be seen more commonly in children with sickle cell disease, while coliforms are more common in neonates and young infants.

The typical radiologic picture of osteomyelitis is that of periosteal elevation, but this is not often apparent for 7–10 days. The appearance of bone lytic lesions and demineralisation is a late finding, but, if present, may also raise the possibility of alternative diagnoses, including bony tumours and metastatic bony lesions. Consequently, bone scans are often used to assist in making the diagnosis.

Blood tests are usually collected for a full blood count, which may show an elevated total white cell count and elevated inflammatory markers such as the erythrocyte sedimentation rate and C-reactive protein. Blood cultures may be positive in about 50% of cases, and aspirated pus at the time of surgical intervention should be sent for culture.

Treatment will require admission to hospital, a prolonged course of antibiotics, possible surgical debridement of the wound to remove pus, rest and analgesia. The standard initial antibiotic treatment for suspected cases of sensitive staphylococcal or streptococcal osteomyelitis would involve the use of flucloxacillin, but the increasing prevalence of community-acquired methicillin-resistant S. aureus means that the use of lincomycin has increased.

A late diagnosis of osteomyelitis may result in loss of bony architecture, and if near a growth plate could affect limb length, local spread with septic arthritis, avascular necrosis and systemic sepsis.

Septic arthritis
This is defined as an infected joint or, more particularly, inflammation of the synovium of the joint by bacterial pathogens.

The young child will present with a swollen joint that is painful with both passive and active movement. The child may refuse to use the limb and refuse to walk. The skin over the joint is warm, red, swollen and tender to touch. In the early stages, fever and lethargy may not be evident.

A common cause is localised spread of osteomyelitis into the joint cavity. Less commonly, there may be direct inoculation of the joint from a penetrating wound. The pathogens are the same as for osteomyelitis, but Group B beta-haemolytic streptococcus in neonates should be included.

Another pathogen to consider in sexually active teenagers is Neisseria gonorrhoea. The previously common pathogen, Haemophilus influenzae type B, has all but been eradicated with near universal vaccine cover in Australian children.

Children with suspected septic arthritis need admission to hospital under the care of an orthopaedic surgeon, who will perform either aspiration or surgical drainage under anaesthesia as soon as practicable, preferably before the commencement of intravenous antibiotics (potentially flucloxacillin and cefotaxime).

Systemic antibiotics are continued for 3–6 weeks in most children depending on the pathogen and whether co-existing osteomyelitis is present. Repeated surgical lavage and debridement may be required.

The differential diagnoses include a reactive mono-arthritis after a viral infection or the initial manifestation of an inflammatory condition such as arthritis. Longer-term complications include degenerative joint disease/arthritis, osteomyelitis, avascular necrosis (e.g. of the femoral head) and systemic sepsis.

CONGENITAL CONDITIONS
Developmental dysplasia of the hip
This is a congenital abnormality that should be detected in infancy. The well baby check and the six-week check are the best opportunities to make the diagnosis by detecting a dislocatable or ‘clicky’ hip. It is more common in girls and firstborn children. Babies who are breech, who have a positive family history and some associated orthopaedic conditions including calcaneovalgus, metatarsus adductus and torticollis should have a screening hip ultrasound at six weeks.

The most sensitive clinical test for detecting a dislocatable hip is asymmetry of hip abduction. To perform the manoeuvre to test for hip dislocation, the thighs should be flexed and then abducted fully. Each thigh should abduct to about 90 degrees. The inability to abduct more than 60–70 degrees indicates an abnormality.

Other features such as asymmetrical skin folds and a ‘clicky’ hip are less sensitive indicators of potential problems with the hip.

It is also important to assess the stability of the hip joint to determine whether the femoral head can be displaced from the acetabulum and then relocated. When doing this, the examiner may get the feeling of the head ‘clunking’ out of the joint over its posterior margin.

To undertake the test for stability of the hip, known as the Barlow test, both the femur and tibia are held in the palm of the hand so that any clicking sensations in the knees will not be confused with what is occurring in the hip joint. The middle finger of the examiner is placed over the greater trochanter and the thumb is placed over the medial thigh. The thighs are then held in mid-abduction and the femoral head is pushed out of the acetabulum by lateral pressure of the thumb and by rocking the knee medially with the index finger.

If the femoral head can be dislocated over the posterior rim of the acetabulum, then the procedure is reversed to relocate the head. If the femoral head can move laterally but not dislocate, the hip is classified as subluxatable, whereas if it is displaced out of the joint it is dislocatable.

With the advent of improved technology, the threshold for an ultrasound of the hip joints is extremely low following any question of hip dislocation. The ultrasound grades abnormalities of the depth of the acetabulum and degree of cover of the femoral head by the joint capsule.

Children with degrees of hip dysplasia are referred for assessment by orthopaedic surgeons. Treatment may involve observation with a repeat ultrasound in 2–3 months for a mild abnormality. More severe grades of dysplasia may require the use of a hip harness or surgery and plaster casting to achieve better coverage of the femoral head by the joint capsule.

Parents should be advised not to wrap the lower limbs of their baby to encourage flexion and abduction of the hips – the ‘froggy position’ – but the use of ‘double nappies’ is of unproven benefit in cases of developmental dysplasia of the hip.

FRACTURES
Buckle fracture versus greenstick fracture of the radius
Radial fractures are common in children. Many have radiographically and clinically mild abnormalities with a small ‘buckle’ fracture, or a ‘greenstick’ fracture and minimal lateral angulation. This is in contrast to complete radial fractures, which are less common.

Minimally displaced fractures are treated without manipulation and are immobilised for up to six weeks. The rate of long-term complications in distal radial fractures is low, as the remodelling potential of the distal radius is very good for dorsal angulation of up to 20 degrees. This results in a very good clinical and radiological final result.

Buckle fractures are considered relatively stable with minimal risk of progressive angulation after immobilisation. In contrast, greenstick fractures have more potential to progressively angulate over the first two weeks after the fracture has occurred. Thus, the need for regular review of buckle fractures is minimal, whereas the need for review of greenstick fractures is warranted. This was nicely demonstrated in a review of 311 distal radial fractures by Randsborg and Siversten (2009).

Patterns of fractures in children
Are boys more accident-prone than girls or just more active? This is an unresolved issue when considering risk factors for fractures in children.

Studies have shown that boys of all ages sustain more fractures than girls and that the risk of another fracture increases with age. The discrepancy is greatest in the adolescent age group, where girls are considered less likely to participate in organised sport.

The association between a more sedentary lifestyle, higher consumption of carbonated drinks and a higher BMI has been noted with lower bone mineral density and a higher fracture risk.

It has been estimated that between one-quarter and one-third of children with one fracture will have a further fracture during childhood.

The location of fractures is reasonably predictable. Preschool-aged children spend more time at home and so have a greater likelihood of sustaining a fracture in the home setting.

School-aged children are more likely to suffer fractures at school when active or during non-sporting recreational activities (e.g. skateboarding). Adolescents are more likely to suffer trauma on sporting fields.

Fractures are more likely to occur in the forearm (distal radius and ulna), followed by the shaft of the radius and then the elbow.

In one series, this accounted for about 73% of fractures in a questionnaire sent to the parents of children presenting to a regional Italian hospital orthopaedic clinic over six months. Most of the injuries were suffered as a result of low-energy trauma.

MULTIFACTORIAL CONDITIONS
Slipped femoral capital epiphysis
Although some GPs may see only one or two cases of slipped femoral capital epiphysis during their career, the results of a delayed or missed diagnosis can be devastating for patients, so a diagnosis must be considered for all paediatric patients who present with knee, thigh or hip pain.

The condition is best thought of as a loss of alignment of the femoral epiphysis, whereby the upper femoral epiphysis slips posteromedially off the metaphysis. It is more common in adolescents, in boys, and in patients who are overweight.

It is suggested that the combination of rapid bone growth and activity levels in pre-adolescent children may predispose to the condition. Endocrinopathies can also be a causative factor.

The condition is bilateral in about 25% of patients; this is more common in children who first present with one slip at a younger age.

Children are reported to have fatigue when undertaking strenuous activities, but may develop pain in the hip or the medial aspect of the knee with or without mild exertion.

Abduction of the hip and internal rotation become limited as the condition progresses.

Although some children may develop increasing pain over time, some will have sudden onset of severe pain and an inability to walk.

This is a surgical emergency as it may indicate complete displacement of the femoral epiphysis, which can lead to significant deformity of the hip in the long-term and/or avascular necrosis of the femoral head and its subsequent collapse.

Imaging includes x-rays with an anterior-posterior view of the pelvis and lateral view of the hips taken in the frog-leg position, with the hip flexed 90 degrees and abducted 45 degrees.

There is widening of the proximal femoral physis (growth plate) and displacement of the capital epiphysis posteriorly and inferiorly. More detailed imaging is provided by CT scans and MRI.

Bone scan can be helpful both at confirming a minor slip and in determining the vascularity of the femoral head. The differential diagnosis includes a transient synovitis of the hip joint, septic arthritis, bursitis and degenerative arthritis.

When a slip is confirmed, treatment is operative, using screws to internally fix the epiphysis to prevent further slipping.

If there is high risk of a bilateral slip, for example, in a younger patient or where there is an underlying endocrinopathy, the contralateral side is prophylactically fixed.

Complications include avascular necrosis of the femoral head, further slippage, long-term deformity that can lead to chronic hip impingement requiring corrective femoral osteotomies to restore alignment, and degenerative arthritis of the hip, which can lead to the need for total hip replacement at a younger age than the general population.

Perthes disease
Perthes disease is avascular necrosis of the femoral head not due to injury.

The aetiology of this condition is unclear. The child will present with a limp and a complaint of vague pain in the region of the groin, inner thigh or hip. There will be limited range of motion of the hip, specifically with abduction, and internal rotation on flexion or extension of the hip. The symptoms are exaggerated by periods of excessive exertion or activity.

This usually self-limiting disorder has an insidious onset lasting from months to years. It is 3–5 times more common in boys than girls. It is usually diagnosed in children aged 5–7 years and is unilateral in most cases (80–90%).

Hip radiographs may demonstrate only joint-space widening, which may be missed initially. Further imaging with CT or MRI will demonstrate flattening of the femoral head, which is known as coxa plana. Healing occurs over 2–3 years. While repair occurs, marked distortion of the femoral head and neck can lead to an imperfect joint.

The goal of treatment is to maintain the normal spherical shape of the femoral head during the hip’s natural repair process. It may require a long period of non-weight bearing.

Prognosis is better for patients who present at a younger age (younger than four years). This reflects their improved ability to remodel the femoral head.

Surgical procedures such as osteotomies of the femur and/or pelvis may be needed in more severe cases of femoral head deformity. Longer-term complications include arthritis and limited mobility. The degree of arthritis and associated pain may necessitate hip joint-replacement surgery in adulthood.

Osgood-Schlatter disease
This is a condition of the anterior tibial tubercle, which occurs as a result of micro trauma to the tibial tuberosity apophysis. This occurs with a normal or increased activity level in adolescents. There is usually no history of direct trauma.

Anterior tibial tubercle swelling in Osgood-Schlatter disease.

There is tenderness over the tuberosity and sometimes some localised swelling in this region. Any activity that stresses the quadriceps will increase the pain. The differential diagnosis includes a contusion, local cellulitis or knee trauma.

No blood tests are needed. The goal of management is to rest the knee and so reduce the stress on the tubercle.

Initially, the adolescent is advised to restrict sporting activity involving knee-bending for 4–8 weeks; the use of NSAIDs and the application of topical icepacks after exercise are advised.

The only complications are restricted activity in the short to medium term.

There are no long-term complications, although a small lump may persist at the site of the tibial tubercle.             

KEY POINTS

• Osteomyelitis may present with an essentially normal radiograph in the first week, and so a bone scan is useful in making an early diagnosis.
• Developmental dysplasia of the hips is not uncommonly missed on clinical examination, and so a low threshold for a hip ultrasound should be considered.
• Buckle fractures are unlikely to develop progressive angulation, whereas greenstick fractures are likely to have mild progressive angulation for the fortnight after injury.
• The only symptom of severe hip pathology may be knee pain.