Nonossifying Fibroma of the Distal Tibia: Predictors of Fracture and Management Algorithm.

ABSTRACT

BACKGROUND: Nonossifying fibroma (NOF) is a common benign lesion in children and adolescents. This study investigated the risk of pathologic fracture in NOF lesions of the distal tibial based on anatomic location, clinical symptomatology, and imaging features, in order to propose an algorithm for the management of such lesions. METHODS: In an IRB-approved retrospective case-control study, all patients diagnosed with NOF between 2010 and 2017 were extracted from our database. Patients below 18 years of age at the time of diagnosis and with lesions involving the distal tibia were included. Demographic data, the reason for visit, and the mechanism of injury were recorded. Radiographs were reviewed to record the size (absolute and relative to bone width) and location of each lesion. Computed tomography and magnetic resonance imaging examinations were also reviewed when available. Two authors graded all lesions using the Ritschl classification and determined the presence of 2 novel signs the syndesmosis sign and the Pac-Man sign. RESULTS: A total of 84 patients were included in the final analysis, of which 25 were in the fracture group and 59 in the nonfracture group. None of the patients in the fracture group was previously diagnosed with NOF, but nine (36%) patients had symptoms for >6 months preceding the fracture. Ankle sprain was the most common reason for visit in the nonfracture group. The lateral location of the lesion in the distal tibia (P=0.001), size (P<0.001 for both absolute and relative values), Ritschl stage (P=0.003), syndesmosis sign (P=0.005), and the Pac-Man sign (P=0.002) were significant predictors of fracture. All measurements had almost-perfect to perfect inter-rater agreements. CONCLUSIONS: The most significant imaging risk factors for fracture are a larger size, Ritschl stage B, and the presence of cortical thinning on anteroposterior or lateral radiographs. We introduced 2 signs for these distal tibial NOFs, a scoring system, and a management algorithm that is based on radiographs alone but incorporates advanced imaging findings in equivocal cases. LEVEL OF EVIDENCE Therapeutic Level III-case-control study.