Parosteal Osteosarcoma: Radiologic and Prognostic Features

Aim: The aim of this study is to evaluate significance of Magnetic Resonance Imaging (MRI) characteristics and their effects on surgical margins, prognosis, oncological and functional outcomes of parosteal osteosarcoma in our clinic. Patients and method: Fifteen patients (4 male/11 female) who operated with the diagnosis of parosteal osteosarcoma in our clinic were retrospectively reviewed. The epidemiological data, biopsy method and delay in diagnosis are noted. The lesions maximum circumferential extension, intramedullary involvement and neurovascular extension in MRI sections were evaluated. The resection type (segmental articular/hemicortical) and surgical margins were noted. Functional and oncological results at last follow-up were assessed. Results: The mean age was 31.7 (17-71) years; mean follow-up was 50.1 (24-176) months. The most common site was distal femur. The closed biopsies were related with increased number of re-biopsies and misdiagnosis/improper interventions. (p<0.001,p=0.023) Intramedullary involvement percentage was related with maximum circumferential extension percentage (p=0.006) The intramedullary involvement ratio of ≤25% suggested no recurrence or metastasis. The mean MSTS score was 87.8% (range, 60-100%). The neurovascular involvement was related with metastatic disease, deep infections and complication related surgeries. (p=0.017, p=0.002,p=0.005) The most common resection type was segmental articular resection (9 patients). Hemicortical resections with biological reconstructions had the best MSTS scores. (p=0.002) The maximum circumferential extension percentage, intramedullary involvement percentage and neurovascular involvement showed lower MSTS scores. The 5-year overall survival was 92.3%, local recurrence-free survival was 86.2% and metastasis-free survival was 86.2%. Conclusion: The reliability of needle biopsy sampling is controversial in parosteal osteosarcomas. The lesions extent of intramedullary involvement, neurovascular bundle proximity and maximum periosteal circumferential extension on MRI should be considered when planning the surgery. The evaluation of maximum circumferential extension on MRI is crucial for the resection margins.