Utility of early screening magnetic resonance imaging for extensive hip osteonecrosis in pediatric patients treated with glucocorticoids

Abstract

Purpose: Hip osteonecrosis frequently complicates treatment with glucocorticoids. When extensive (affecting ≥ 30% of the epiphyseal surface), 80% of joints collapse within 2 years, so interventions are needed to prevent this outcome.

Patients and methods: This prospective cohort magnetic resonance imaging (MRI) screening study included all consecutive children treated for acute lymphoblastic leukemia on a single protocol. Hip MRI was performed at 6.5 and 9 months from diagnosis (early screening) and at completion of chemotherapy (final evaluation) to determine whether screening could identify extensive hip osteonecrosis before symptom development.

Results: Of 498 patients, 462 underwent screening MRI. Extensive asymptomatic osteonecrosis was identified by early screening in 26 patients (41 hips); another four patients (seven hips) were detected after the screening period, such that screening sensitivity was 84.1% and specificity was 99.4%. The number of joints screened to detect one lesion was 20.1 joints for all patients, 4.4 joints for patients older than 10 years, and 198 joints for patients ≤ 10 years old (P < .001). Of the 40 extensive lesions in patients older than 10 years, 19 required total hip arthroplasty and none improved. Of eight extensive lesions in younger patients, none required arthroplasty and four improved.

Conclusion: In patients age 10 years old or younger who require prolonged glucocorticoid therapy, screening for extensive hip osteonecrosis is unnecessary because their risk is low and lesions tend to heal. In children older than 10 years, early screening successfully identifies extensive asymptomatic lesions in patients who would be eligible for studies of interventions to prevent or delay joint collapse.

Trial registration: ClinicalTrials.gov NCT00137111.

Fig 1.

(A) CONSORT diagram of patients undergoing hip magnetic resonance imaging (MRI) as part of the osteonecrosis screening portion of the Total Therapy Study XV. Extensive osteonecrosis is defined as that affecting 30% or more of the epiphyseal surface. (B) Protocol schema indicating time points of early screening magnetic resonance imaging and final assessment. DEX, dexamethasone; PRED, prednisone.

Fig 2.

Magnetic resonance images (MRIs) showing a normal hip and hips with clinically significant osteonecrosis in an asymptomatic patient. Arrows indicate the border of the osteonecrotic lesions. Thick arrows mark epiphyseal osteonecrosis, and thin arrows mark metaphyseal lesions. These (A to C) coronal noncontrast T1-weighted and (D) short tau inversion recovery–weighted MRIs show (A) a normal hip, (B) a hip with a small (< 30%) epiphyseal osteonecrotic lesion and involvement of the femoral neck and proximal diaphysis, and (C and D) a more than 30% lesion of the femoral head along with involvement of the femoral neck. Panel D shows how the percentage involvement of the epiphyseal surface is measured. The yellow circumference shows the entire epiphyseal surface, and the red line shows the length of the epiphyseal surface affected by the lesion (delimited by red arrows).

Fig 3.

Cumulative incidence of hip osteonecrosis by femur site in pediatric patients with acute lymphoblastic leukemia. The blue dotted line represents patients with any hip osteonecrosis, including epiphysis (to any extent) or metaphysis. The red dashed line represents patients with osteonecrosis of the epiphysis (regardless of the extent of epiphyseal involvement, but excluding patients whose only sites of hip osteonecrosis were in the metaphysis). The black line shows patients with epiphyseal osteonecrosis affecting ≥ 30% of the articular surface, which represents extensive osteonecrosis with high risk of subsequent joint collapse and need for arthroplasty.

Fig A1.

(A) Cumulative incidence of osteonecrosis in the epiphysis or metaphysis of either hip in pediatric patients with acute lymphoblastic leukemia by age group. (B) Cumulative incidence of osteonecrosis in the epiphysis or metaphysis of either hip in pediatric patients with acute lymphoblastic leukemia by leukemia risk group.

Fig A2.

Cumulative incidence of osteonecrosis of either hip by physeal patency status among patients 11 to 15 years old.