A 6-year-old boy is brought to the office for follow-up for a limp. His symptoms began 2 months ago as a dull ache in the left knee with an intermittent limp. The parents brought him to an urgent care center at that time and were reassured that the laboratory evaluation and x-rays of the knees and hips were normal. The pain has not worsened, but the patient now has a persistent limp with no other joint or muscle pain. He has been well except for a brief upper respiratory infection with low-grade fever about 2 weeks ago. He has a history of recurrent ear infections and had tympanostomy tubes placed 2 years ago. The patient takes no daily medications, and immunizations are up to date. Temperature is 37.1 C (98.8 F), blood pressure is 95/65 mm Hg, pulse is 80/min, and respirations are 16/min. BMI is at the 60th percentile. Examination shows a well-appearing and alert child. Range of motion, particularly internal rotation and abduction, of the left hip is markedly limited. The remainder of the examination is normal. Which of the following is the most likely diagnosis in this patient?

Question

A 6-year-old boy is brought to the office for follow-up for a limp.  His symptoms began 2 months ago as a dull ache in the left knee with an intermittent limp.  The parents brought him to an urgent care center at that time and were reassured that the laboratory evaluation and x-rays of the knees and hips were normal.  The pain has not worsened, but the patient now has a persistent limp with no other joint or muscle pain.  He has been well except for a brief upper respiratory infection with low-grade fever about 2 weeks ago.  He has a history of recurrent ear infections and had tympanostomy tubes placed 2 years ago.  The patient takes no daily medications, and immunizations are up to date.  Temperature is 37.1 C (98.8 F), blood pressure is 95/65 mm Hg, pulse is 80/min, and respirations are 16/min.  BMI is at the 60th percentile.  Examination shows a well-appearing and alert child.  Range of motion, particularly internal rotation and abduction, of the left hip is markedly limited.  The remainder of the examination is normal.  Which of the following is the most likely diagnosis in this patient?

Quizplus · Accepted Answer

11ec25c8_d96c_8f81_bc81_cb4c480ab232_MD0003_00 This patient most likely has Legg-Calvé-Perthes disease (LCP), or idiopathic osteonecrosis (avascular necrosis) of the femoral head. LCP classically affects boys age 3-12, with peak incidence at age 6. Patients typically have an antalgic gait (avoids weight bearing on the affected side due to pain) and dull, chronic lower extremity pain of insidious onset. The pain may affect the hip directly or present as referred thigh or knee pain, as in this patient. Diagnosis requires a high index of suspicion as initial x-rays may be normal. Persistent symptoms should prompt repeat imaging, which in later stages typically shows sclerosis of the femoral head with flattening and fragmentation. As the disease progresses, examination may reveal limited internal rotation and abduction of the hip. Proximal thigh atrophy and Trendelenburg sign may also be present. femoral head Trendelenburg sign Treatment is aimed at maintaining the femoral head within the acetabulum by avoiding weight-bearing activities and by splinting or surgery. (Choices A and C) Bacterial arthritis typically presents acutely with fever and inability to bear weight as well as pain, swelling, erythema, and warmth of the joint. Osteomyelitis typically affects the metaphyses of long bones (eg, humerus, femur) and classically presents with fever, point tenderness, and localized edema. This patient is afebrile, appears well, and has chronic pain, making bacterial infection unlikely. (Choice B) Untreated developmental dysplasia can lead to limp and hip pain in childhood or adolescence. Initial radiographs show a dysplastic or dislocated hip. In addition, physical examination typically reveals a leg-length discrepancy (ie, shortening of the affected extremity), which is not seen in this patient. (Choice E) Slipped capital femoral epiphysis also presents with limp and insidious hip pain. Patients are typically adolescent and obese, neither of which is true in this patient. In addition, x-ray shows posterior displacement of the femoral head, unlike the normal x-rays in this patient. Slipped capital femoral epiphysis (Choice F) Transient synovitis also presents with hip or knee pain and limp; however, symptoms typically develop after a viral infection and resolve within 4 weeks. This patient has had symptoms for 2 months and more likely has LCP. Educational objective: Legg-Calvé-Perthes disease, or avascular osteonecrosis of the femoral head, typically presents in boys age 3-12 with insidious-onset hip or (referred) knee pain and an antalgic gait. X-rays may be normal in early disease but demonstrate abnormalities (eg, femoral head flattening, fragmentation, sclerosis) with chronic symptoms. References: Legg-Calvé-Perthes disease. (http://www.ncbi.nlm.nih.gov/pubmed/27064472)

A 6-Year-Old Boy Is Brought to the Office for Follow-Up