Intra-articular Osteoid Osteoma Involving the Femoral Neck in Pediatric Population: A Case Report of 2 Cases

INTRODUCTION: An osteoid osteoma is a benign bone tumor. It is quite common and has become a known entity to most orthopedists and radiologists since it was first reported by Jaffe in 1935. Considering its incidence, it is at third position in the list of most common benign tumors, with prevalence up to 11% among the benign tumors and 3% among primary bone tumors. CASE REPORT: Case 1 - A 15-year-old male presented with symptoms of left hip pain for 1 year. Radiographs were repeated by us at 1 year which revealed cortical thickening and sclerosis surrounding the central lucent nidus in the posterolateral aspect of femoral neck. The patient underwent en bloc resection of the lesion. Case 2 - A 13-year-old male presented with symptoms of left hip pain for 1½ years. Radiographs revealed an irregular lucent area surrounded by sclerosis in inferior aspect of femoral neck. By gradual removal of overlying reactive bone, the underlying nidus was exposed. Excision with curettage and burr was applied to the nidus, with bone chips used to fill the cortical defect. RESULTS: Both the patients were followed for a period of 1 year from surgery as chances of recurrence of osteoid osteoma is within that period. In both the cases, Harris hip score improved from poor status pre-operatively to a score between 80 and 89 (good result) at 1 month, and >90 (excellent result) on further follow-ups. By 1 year, the lesion had healed and femoral neck size, neck shaft angle, and joint widening were also reduced to normal. DISCUSSION AND CONCLUSION: Intra-articular osteoid osteomas behave differently than extra-articular tumors. The radiological and clinical features are different from extra-articular lesions. Computed tomography (CT)-guided radiofrequency (RF) ablation is a safe, effective, simple method to treat osteoid osteoma. Open excision can be performed in the absence of CT-guided RF ablation.