Accuracy of CT and MRI to assess resection margins in primary malignant bone tumours having histology as the reference standard.

AIM: To evaluate the accuracy of magnetic resonance imaging (MRI) and computed tomography (CT) in assessing the resection margins of primary malignant bone tumours. MATERIALS AND METHODS: Resected primary malignant bone tumour specimens removed from 46 patients (27 male; mean age: 48±22 years) were imaged using MRI (fat-saturated proton density-weighted and three-dimensional fat-suppressed T1-weighted gradient-recalled-echo) and CT immediately after surgery. A radiologist and an orthopaedist evaluated bone and soft-tissue margins of the specimens on both examinations. Histological evaluation was performed by a senior orthopaedic oncology pathologist. Margins were classified as R0 (safe margins), R1 (residuals between 0 and 1 mm), and R2 (macroscopic residuals). Cohen's k, chi-square, and McNemar's statistics were used. RESULTS: Having histology as the reference standard, reproducibility of the radiologist ranged from moderate (k=0.544) to substantial (k=0.741) for bone and soft-tissue margins on CT, respectively, while that of the orthopaedist ranged from fair (k=0.316) to moderate (k=0.548). When comparing R2 and R0+R1 scores, reproducibility of readers' evaluation of bone margins increased ranging from substantial (k=0.655) to perfect (k=1.000). Inter-reader agreement ranged from fair (k=0.308) to substantial (k=0.633). Accuracy of the radiologist and orthopaedist ranged from 76% to 83% and from 68% to 72%, respectively. When comparing R2 and R0+R1 scores, the accuracy of both readers ranged from 83% to 100%. There was no association between local recurrence and margin scores of histology, MRI, and CT (p≥0.058). CONCLUSIONS: MRI and CT may be useful for extemporaneous analysis of resection margins of primary malignant bone tumours, although wide accuracy variability between the different imaging methods was observed.

[Percutaneous radio-frequency ablation of osteoid osteoma: technique and preliminary results]. / Termocoagulazione percutanea degli osteomi osteoidi mediante radiofrequenza: tecnica e risultati preliminari.

PURPOSE: To report our personal experience with the percutaneous technique for in situ destruction of osteoid osteoma using radio-frequency ablation. MATERIAL AND METHODS: From January 2000 to January 2001 we performed 16 radio-frequency ablations in 15 patients. All candidates for treatment had previously undergone clinical and radiologic examinations to confirm features typical of osteoid osteoma. After administration of spinal anesthetic, procedures were performed with CT-guidance, using a Kirschner wire introduced into the localized lesion, and a guiding cannula. A hole was first cut into the bone with a cutter, then a few biopsy specimens were obtained with a Jamshidi needle. Finally, we introduced a small radio-frequency electrode into the bone, through the biopsy track. Sufficient current was used to heat the electrode tip to 85-90 degrees C with consequent thermal necrosis of the tissue. The healing was continued for 6 minutes. RESULTS: All patients well tolerated the percutaneous procedure and only 1 underwent a second, successful radio-frequency ablation. In all cases, pain relief was noted to occur very rapidly and all patients could bear full weight on the treated extremity within 24 hours after the procedure. No late complications attributable to the ablation were noted, except for a small eschar next to the puncture site. DISCUSSION AND CONCLUSIONS: The results of the present study suggest that percutaneous ablation is preferred to operative excision because it generally requires shorter hospital stay and is not associated with complications. Furthermore, in our experience, pain relief was noted to occur very rapidly in 100% of cases. In agreement with the literature data, our results show that CT-guided percutaneous radio-frequency ablation can actually replace operative excision in the treatment of osteoid osteoma as it achieves the same clinical outcomes with significantly lower costs.