MSK

Question 1

Most common organism causing septic arthritis in neonates?

Answer 1

Staph Aureus

Can also be E Coli, group B strep

Question 2

Most common organism causing septic arthritis in children age 2-5?

Answer 2

S aureus is the most common cause. Hib was the most common before vaccinations. Other etiologies include group A streptococci and Streptococcus pneumoniae. Community-acquired methicillin-resistant S aureus (MRSA-CA) is an increasingly common cause of SA in children.
monoarticular disease. Group A streptococcus is reported in numerous children with active varicella-zoster infection.

Mycobacterium tuberculosis is a rare cause of chronic pyogenic arthritis.

Question 3

What organism would you suspect in adolescents with septic arthritis?

Answer 3

In adolescents, Neisseria gonorrhoeae is the suspected cause for patients with either polyarticular or monoarticular.

Question 4

Which joints are most commonly affected?

Answer 4

The most frequently affected sites of infection were in the large joints at the lower limbs (hips, knees). The hip is a particular area of concern. These infections and the age category of 10-14 years of age were associated with osteomyelitis and bacteremia/septicemia comorbidities.

Question 5

In what age group is septic arthritis more common in?

Answer 5

Under 2s. It is more common in children in general too.

Question 6

What should be considered in septic arthritis?

Answer 6

Underlying and predisposing illnesses such as immunodeficiency and sickle cell disease should be considered.

Question 7

Presentation of septic arthritis?

Answer 7

Patients usually present with fever, joint pain and/or unwillingness to move the affected joint (eg, a limp or refusal to weight bear if the hip joint is affected).

• This is usually with an erythematous, warm, acutely tender joint, with a reduced range of movement, in an acutely unwell, febrile child.
• Infants often hold the limb still (pseudoparesis, pseudoparalysis) and cry if it is moved. it may be held drawn up and outwards to reduce intracapsular pressure. Any leg movement is painful and is resisted.
• A joint effusion may be detectable in peripheral joints. Although a sympathetic joint effusion may be present in osteomyelitis, it is accompanied by marked tenderness over the bone.

However, in up to 15% of cases of osteomyelitis, there is coexistent septic arthritis. The diagnosis of septic arthritis of the hip can be particularly difficult in toddlers, as the joint is well covered by subcutaneous fat. Initial presen- tation may be with a limp or pain referred to the knee.

Question 8

What is the classic position of septic arthritis of the hip in an infant?

Answer 8

Position of flexion, abduction, and external rotation of the hip to maximise capsular volume and reduce pressure.

Question 9

Main differences between septic arthritis and transient synovitis?

Answer 9

• There will be a moderate-high fever in septic arthritis with a none/mild In TS
• In TS the child often looks more well
• In TS, the patient is comfortable at rest, limited internal rotation and pain on movement. In SA, the hip is held flexed; severe pain at rest and worse on any attempt to move joint
• The white cell count MAY be high in SA, with a raised ESR and widened joint space on Xray

Question 10

Course of transient synovitis?

Answer 10

Resolves by self in <1 week, approx. 3% develop Perthes disease

Question 11

Course of septic arthritis?

Answer 11

Progressive and severe joint damage if not treated. Risk of osteomyelitis, haematological spread.

Question 12

Investigations in septic arthritis:

Answer 12

• There is an increased white cell count and acute-phase reactants. Blood cultures must be taken.
• Ultrasound of deep joints, such as the hip, is helpful to identify an effusion. X-rays are used to exclude trauma and other bony lesions. However, in septic arthritis, the X-rays are initially normal, apart from widening of the joint space and soft tissue swelling. Further imaging options include MRI scanning if the site of infection is unclear.
• Aspiration of the joint space under ultrasound guidance for organisms and culture is the definitive investigation. Ideally, this is performed immediately, unless this would cause a significant delay in giving antibiotics.

Question 13

Treatment for septic arthritis:

Answer 13

A prolonged course of antibiotics is required, initially intravenously.

Washing out of the joint or surgical drainage may be required if resolution does not occur rapidly or if the joint is deep-seated, such as the hip.

The joint is initially immobilizsed in a functional position, but subsequently must be mobilized to prevent permanent deformity.

Question 14

What age and gender is usually affected by Perthe’s disease?

Answer 14

Boys 5:1

Age usually 5-10

Usually caucasians

Question 15

What are the 3 characteristics of Perthe’s disease?

Answer 15

• The essential lesion is loss of blood supply (avascular necrosis) of the nucleus of the proximal femoral epiphysis.
• Abnormal growth of the epiphysis results.
• Eventual remodelling of regenerated bone.

This cycle of necrosis- revascularisation- reossification happens over 18 months typically.

Question 16

Presentation of Perthe’s

Answer 16

-It presents with pain in the hip or knee and causes a limp.
There is pain (often in the knee) and an effusion (from synovitis).

-10-15% of cases are bilateral, but will be at different stages and are asymmetrical.

-On examination all movements at the hip are limited:
The early phase has limited abduction of the hip and limited internal rotation in both flexion and extension.

• There is an antalgic gait (due to pain). Trendelenburg gait (hip drop) is seen in the late phase.
• No history of trauma.
• Roll test: with the patient lying in the supine position, the examiner rolls the hip of the affected extremity into external and internal rotation. This test should invoke guarding or spasm, especially with internal rotation.

Question 17

Investigations to do in suspected Perthe’s disease:

Answer 17

• X-rays= most likely a frog leg view to see the femoral heads most clearly. Early X-rays may show widening of the joint space, increased density of the femoral head or may be normal. Later, there is a decrease in the size of the nuclear femoral head with patchy density on X-ray. Later still, there may be collapse and deformity of the femoral head with new bone formation.
• Technetium bone scan or MRI scanning can be used to i-identify pathology (seen as an area of reduced perfusion).
• An arthrogram and/or MRI scan are often needed to assess congruency throughout full range of movement. A flat-topped incongruent head has the worst prognosis.
• Hip aspiration if a septic joint is suspected.

Question 18

Ddx for Perthe’s?

Answer 18

Transient synovitis is the most common differential. Also, septic arthritis, sickle cell and a few more.

Question 19

Management of Perthe’s?

Answer 19

The aim of treatment is to maintain the sphericity of the femoral head and the congruency of the femur-acetabulum relationship/ maintain movement to prevent secondary degenerative arthritis. This encourages return of blood supply.

• Children who have a skeletal age of 6.0 years or less at the onset of the disease do well without treatment (50%): If the hip is in a good position and there is no spasm (muscle tightening) your child will be seen regularly in the outpatient clinic to check their symptoms and range of hip movement. An x-ray will be taken during each hospital visit to monitor the progress of the condition. Your child will continue to be followed-up in the outpatient clinic until the head of the femur has completely healed.
• Operative treatment should be considered in children who are six years old or older and have over 50% femoral head necrosis when the diagnosis is made.
• Children with hip pain and reduced range of movement may be admitted to hospital for bed rest or simple traction (if femur is not well positioned in joint/ there’s a loss of function). Traction helps to reduce pain by resting the hip joint. It is applied using bandages and light weights. Your child will be given regular pain relief when needed. Hydrotherapy (therapy in water) may also be used to encourage easy movement of the hip joint. Once the pain and muscle spasm has settled your child will be able to go home. They may need to use crutches when walking, for comfort. Regular follow-up care will continue in the outpatient clinic.
• Physiotherapy- to increase strength and range of movement

Question 20

Prognosis of Perthe’s?

Answer 20

In most children the prognosis is good, particularly in those below 6 years of age with less than half the epiphysis involved. In older children or with more extensive involvement of the epiphysis, deformity of the femoral head and metaphyseal damage are more likely, with potential for subsequent degenerative arthritis in adult life.

More than 80% of affected hips have good or very good outcomes that persist into the fourth decade of life. However, after this decade half of all needed a hip replacement.