Explain Perthes disease to a family — OSCE

Candidate brief

You have eight minutes to counsel the parents of a six-year-old boy who has been diagnosed with Legg-Calve-Perthes disease. The diagnosis is based on the persistent limp, the stiff hip, and the radiograph showing a dense femoral head. Use a structured, honest, empathic approach that explains the diagnosis in plain language, addresses the parents' fears and the playground-injury theory, outlines the long two-to-three-year course of the disease, and builds a shared plan for monitoring the lateral pillar grade and the containment decision. [4] [1]

Key communication points

Acknowledge and explore the parents' concerns. The parents are anxious because a limp they attributed to a playground fall has turned into a diagnosis that lasts years, and they are trying to reconcile the two. Acknowledge the worry, validate the connection they have drawn, and explain gently that the fall drew attention to a hip that was already affected by an interruption of its blood supply — the fall did not cause the disease. [4]

Explain the diagnosis in plain language. The child has a condition called Legg-Calve-Perthes disease, in which the blood supply to the ball of the hip joint has been interrupted, the ball has lost its strength, and the body is now in the process of breaking down and rebuilding the bone over the next two to three years. The good news is that the disease always heals, and the goal of treatment is to help the ball heal in a good, round shape so that the hip works well through adult life. [4]

Explain the long course and the phases. The disease runs through phases — first the bone loses its blood supply, then it softens and may lose some height, then the body rebuilds the new bone, and finally the hip reshapes over the years. This is why it takes two to three years, and why the family will be seen regularly in the clinic over that time. The activity will be modified to protect the soft hip during the rebuilding phase. [1]

Address the knee pain if asked. The child points to the knee because the hip and the knee share the same nerve supply, so a problem in the hip is often felt in the knee. This is common, and it is why the doctor examined the hip even though the child pointed to the knee. [4]

Build a shared plan. The child will be seen regularly in the orthopaedic clinic, with radiographs to monitor how much of the hip is involved — a measure called the lateral pillar grade — and the doctor will decide whether the hip needs help to heal in a round shape. For a child this age, many hips heal well with observation and activity modification alone, and surgery is considered if the hip is at risk of healing flat. The family will be involved in that decision as the picture becomes clearer. [1] [9]

Examiner's marking key

Strong candidates will:

• Acknowledge the parents' anxiety and the playground-fall theory before gently correcting it [4]
• Explain Legg-Calve-Perthes disease and the interrupted blood supply in plain, non-technical language [4]
• Outline the long two-to-three-year course and the phases of healing without overwhelming the family [1]
• Address the knee-referred pain with the shared nerve supply explanation [4]
• Build a clear shared plan for monitoring the lateral pillar grade and the containment decision [1] [9]

Weak candidates will:

• Use technical jargon about avascular necrosis and lateral pillar grades without translation [4]
• Fail to address the playground-fall theory, leaving the parents confused about the cause [4]
• Promise surgery or promise no surgery without explaining the age-and-grade-guided decision [1]
• Miss the opportunity to reassure the family that the disease always heals and that the goal is a good head shape [9]