Role of MRI in the Detection and Monitoring of Lower Limb Osteonecrosis after Chemotherapy in Pediatric Patients with Acute Lymphoblastic Leukaemia

Background: Magnetic resonance imaging (MRI) is the technique that demonstrated the highest sensitivity and specificity in the early diagnosis of osteonecrosis. It allows detecting initial typical signal intensity alterations of the bone marrow when other examinations showed nonspecific findings or even no alterations at all. The aim of this study is to assess the role of magnetic resonance imaging in detection and monitoring osteonecrotic lesions in pediatric patient with acute lymphoblastic leukemia after chemotherapy.

Materials and Methods: This prospective study was performed on 30 pediatric patients ranged from 4 to 18 years with acute lymphoblastic leukemia on chemotherapy or after 3months from ending chemotherapy with symptoms suspicious for osteonecrosis (i.e., articular pain). All patients were explained about the procedure to be done. MRI study of whole lower limbs was done for all patients.

Results: In the present study all patients were symptomatic. 24\30 patients (80%) had hip pain, 25\30 patients (83.3%) had knee pain and 8\30 patients (26.7%) had limping. We reported that knee pain was the most common complaint representing 83.3% of patients. 11\30 patients (36.7%) had no MRI findings. 19\30 patients (63.3%) had different positive findings; 4 patients (13.3%) had non -articular osteonecrosis (ON) only with no joint involvement (bone infarction), 2 patients (6.7%) had avascular necrosis of femoral head epiphysis without bone infarction and 13 patients (43.3%) had combined bone infarction and avascular necrosis with Joint involvement. Follow up by MRI was done for all patients (30 patients), 27 patients showed no change in MRI findings, one patient progressed from avascular necrosis of the femoral head epiphysis without deformity to avascular necrosis of the femoral head epiphysis with deformity. The other two patient showed regressive course.

Conclusion: We concluded that MRI study is mandatory for early detection and monitoring of lower limb osteonecrosis in pediatric patients with acute lymphoblastic leukemia under or after chemotherapy. The radiologist and clinician must do MRI lower limbs routinely and follow up MRI after 4-6 months to first MRI due to some patients had regressive or progressive findings.