Prophylactic Fixation of a Large Distal Tibial Non-ossifying Fibroma in an Adult Guided by a Modified Mirels Score: A Case Report

Non-ossifying Fibromas (NOFs) are benign, self-limiting bone lesions most commonly seen in children and adolescents, and they rarely persist into adulthood. Although typically asymptomatic and incidentally discovered, large lesions in weight-bearing bones such as the tibia may pose a risk of pathological fracture, particularly in adults. We present the case of a 53-year-old female who presented with the chief complaint of pain over the anterior aspect of her left leg for three months. Plain radiographs of the left leg showed a well-defined, dumbbell-shaped lytic lesion in the distal third of the tibial diaphysis, characterised by a narrow zone of transition and sharply demarcated margins. Computed Tomography (CT)-guided biopsy and Magnetic Resonance Imaging (MRI) were indicative of a NOF. Applying a modified Mirels scoring system for risk stratification in benign bone tumours, the patient was deemed at significant risk of fracture. The patient eventually underwent surgical intervention, and the postoperative recovery was uneventful. This case highlights the utility of a modified Mirels score in decision-making for prophylactic fixation of benign yet structurally compromising bone lesions in adults. Early intervention in high-risk cases may prevent complications and optimise outcomes.