Volume 4, Case 19
Collin S. Goto, MD
Children's Medical Center of Dallas
University of Texas Southwestern School of Medicine
This patient is a previously healthy 11 year old female who presents to the emergency department with a 2 week history of gradually worsening bilateral hip pain, left greater than right. She denies involvement of any other joints. There is no history of trauma, fever, weight loss, recent illness, and the patient denies sexual activity. The family history is negative for rheumatologic disease.
Exam: VS T 36.7 (Tympanic), P 72, RR 18, BP 110/68. She is of average body build, with a weight of 38 kg. She is alert and not ill-appearing. Head, neck, lung, heart, abdominal, and neurologic exams are all within normal limits. On examination of the lower extremities, she has pain with both active and passive range of motion in both hips, left greater than right. Pain is elicited with all movements, including flexion, extension, adduction, abduction, and internal/external rotation. Nearly full passive range of motion can be attained, but with difficulty and pain. There is no erythema, swelling, or increased warmth. There is no muscle atrophy distally. She walks with a slow, stiff, antalgic gait (see Case 16 in Volume 4, A Limping 6-Year Old). The remaining joints of the upper and lower extremities are not involved.
Laboratory Results: CBC WBC 8,800, 44% neutrophils, 41% lymphocytes, 5% monocytes, 8% eosinophils, and 2% basophils. The hemoglobin, hematocrit, and platelet count are normal. The erythrocyte sedimentation rate is 9 mm/hr, and the C-reactive protein is < 1mg/dL. Hip radiographs are obtained.
View hip radiographs.
Do you see anything abnormal about these radiographs. Clinically, we would expect to find potential abnormalities in both hips, with the left worse than the right. Thus comparing one side to the other may not be as helpful as in a unilateral problem.
AP and frogleg views of the hips demonstrate bilateral joint space narrowing, left greater than right. In addition, there are early subchondral cysts seen on the left within the femoral head. There is no evidence of fracture, dislocation, or slipped capital femoral epiphysis. This condition is known as idiopathic chondrolysis of the hips.
Teaching points and Discussion:
1. Idiopathic chondrolysis of the hip was first described by Jones in 1971 as a condition characterized by an extensive loss of articular cartilage of the femoral head and acetabulum, in the absence of known etiologies of chondrolysis, such as slipped capital femoral epiphysis (SCFE), prolonged immobilization, infection, rheumatoid arthritits, and trauma.
2. The typical presentation of idiopathic chondrolysis of the hip is that of an afebrile, previously healthy, adolescent female with an insidious onset of hip, thigh, or knee pain, associated with a limp and progressive loss of movement of the affected hip. Patients often have restricted hip movements at the time of presentation, with fixed flexion, abduction, or adduction deformities. Hip radiographs show a characteristically narrowed joint space. The disease process may involve one or both hips. Infectious workup, including white blood cell counts, blood cultures, and ESR are normal. Rheumatologic workup similarly is negative.
3. The differential diagnosis for hip pain in adolescents includes septic arthritis, toxic synovitis, trauma, SCFE, Legg-Calve-Perthes disease (juvenile idiopathic avascular necrosis of the femoral head), monoarticular rheumatoid arthritis, tuberculosis, leukemia, synovioma, and other neoplasms. Narrowing of the hip joint space is an important finding that virtually excludes acute synovitis, bacterial and viral arthritis, trauma, or the early stages of juvenile rheumatoid arthritis (JRA) or spondyloarthritis. In the early stages of these disorders, the hip joint space is normal or widened. In addition, monoarticular JRA is predominantly a disease of the knee, ankle, or wrist. The hip joint is very rarely affected, especially in girls. The radiographic diagnosis of fractures, neoplasms, SCFE, and Legg-Calve-Perthes disease should be readily apparent.
4. Early radiographic findings of idiopathic chondrolysis of the hip include symmetrical joint space narrowing (due to loss of articular cartilage), periarticular osteoporosis, erosions of the articular cartilage of the acetabulum and femoral head, blurring of the subchondral line, subchondral cyst formation, and protrusio acetabuli (as noted by a progressive increase in the center edge of Wiberg). Late changes include marginal osteophyte formation, lateral buttress formation, early closure of capital and trochanteric epiphyseal plates, widening of the femoral head and neck, and ankylosis.
5. The method of measurement of the width of the femoral head and neck is described in Bleck (1983).
View diagram of this method.
The center of the head (O) is located by the method of Wiberg. The femoral neck is bisected through the center (line ab). Line cd runs perpendicular to line ab through the center of the head. The length of line cd to the margins of the head is the width. Line ef is drawn perpendicular to line ab at the junction of the head and neck to measure the width of the femoral neck.
6. The method of measurement of the width of the hip joint space on an anteroposterior radiograph of the hips is also described in Bleck (1983).
View diagram of this method.
The center of the femoral head is located and the line for measurement of the width of the femoral head is marked. The femoral head is bisected by a line perpendicular to the line for measurement of the width. Each half segment (90 degrees) is divided into four quarters of 22.5 degrees. The width of the joint within the first lateral quadrant of the bisected head is measured.
By this method, our patient's hip joint width measured 1 mm on the left and 2-3 mm on the right. Normal hip joint width is reported to be 3-5 mm.
7. Histologic features of idiopathic chondrolysis of the hip include thickening of the capsule with edematous changes in the capsule and synovium. There are articular surface changes with fibrillation, fragmentation, and progressive loss of cartilage. An infiltration of lymphocytes is seen within the synovium, and there may be degeneration of chondrocyte nuclei and loss of cells in the lacunae.
8. Early reports suggested that therapy should consist of physical therapy, non-weightbearing, and non-steroidal anti-inflammatory drugs. Soft tissue releases and traction were occasionally used to treat contractures. However, many cases resulted in a poor outcome with fibrous ankylosis and loss of movement in the hip. More recently, it has been suggested that non-weightbearing does not adequately unload the hip, and the positioning of the hip when crutches are used may actually potentiate the flexion contracture. Casting or any other immobilization is contraindicated as the pathologic process involving the articular cartilage may be compounded. Roy and Crawford reported a small series of patients treated with subtotal circumferential capsulectomy and muscle release, followed by an aggressive rehabilitation program consisting of split Russell's traction, continuous passive motion, and limited weightbearing. This was supplemented by active and passive range of motion exercises, resulting in a resolution of symptoms, improvement in range of motion and widening of the joint space, rather than the usual progressive course.
9. Our patient's presentation was typical of idiopathic chondrolysis of the hip. The history, physical examination, laboratory data, and radiographs all supported this diagnosis. The diagnosis is suggested when an adolescent patient presents with insidious onset of hip pain, radiographs show a narrowed hip joint space, and known causes of chondrolysis, such as SCFE, prolonged immobilization, or trauma are absent. Infection is unlikely if the patient is afebrile, with a normal white blood cell count, ESR, and CRP. In addition, the hip joint space is usually increased with infection, rather than decreased. Monoarticular JRA rarely affects the hip, and in the early stages, typically demonstrates a widened joint space with an effusion, and an increased ESR and CRP. Thus, the radiographic finding of a narrowed hip joint space in patients presenting with hip pain is clearly an important distinction which limits the differential diagnosis significantly. Awareness of the clinical entity of idiopathic chondrolysis of the hip is important because of the loss of function and severe disability often associated with it.
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