A Clinical And Experimental Study On The Value Of MRI In Determining Bone Marrow Extension Of Malignant Bone Tumor

Objective: To investigate the value of MRI in measuring bone marrow extensioninfiltrated by malignant bone tumor and the reliability of preoperative plan ofosteotomy according to the MRI measurement.Methods and material: Establishing the rat animal model bearing a transplantableosteosarcom and clear the local extension of osteosarcoma on MRI imaging. Thelevel of osteotomy determined by MRI was compared with the pathohistologicfindings. In addition, 12 patients with malignant bone tumor were selected in ourclinical study. All patients were examined with both MRI and X-ray before the limbsalvage surgery. The level of osteotomy was determined as the point in which marrowsignal intensity changed from normal to abnormal in T₁WI. Bone marrow samplewere get out in four points and the results were analyzed statistically.Results: The osteosarcoma was formed in 24 rats of 30 and the achievement ratiowas 80%. The mean tumor extension was 0.9cm, ranging from 0.7 to 1.2cm in X-rayfilm. MRI was 2.2cm, ranging from 1.2 to 2.8cm in T₁WI, 1.73cm, ranging from1.0to 2.2cm in T₂WI and 2.5cm, ranging from 1.3 to 3.7cm in STIR respectively. Thetumor extension found by the method of pathohistology was 2.0cm, ranging from 0.9to 2.63cm. In clinical study, The tumor extension in the bone marrow decided byX-ray film, MRI and pathohistology was (14.0±3.8)cm, (17.5±6.3)cm and(17.0±2.5)cm respectively. And there was no significant difference between theextensional scope measured on MR images and the actual scope.Conclusion: The aggressive extension could be measured correctly on MRI,according to which, it is reliable to estimate the surgical margins. Objective: To investigate the value of MRI in measuring bone marrow extensioninfiltrated by malignant bone tumor and the reliability of preoperative plan ofosteotomy according to the MRI measurement.Methods and material: 12 patients were selected in our hospital from 2005 to 2007,of them 5 cases were diagnosed as osteosarcoma, 2 cases were diagnosed as giant celltumor(GCT), 2 cases were diagnosed as malignant fibrous histiocytoma (MFH),plasma cell myeloma, desmoid tumor(DT) and leiomyosarcoma(LMS) 1 case each. 6were located in distal femur, 2 were located in intermediate femur, 2 were located inproximal femur, and proximal tibia and distal radial lcase each. 5 cases were treatedwith tumor resection and massive allograft grafting, of them 4 were in femur and theother one who had an GCT tumor in distal radial was treated with tumor resection andauto-segment fibular transplantation. 5 cases were operated with tumor segmentalresection and custom-made prostheses replacement, of them 2 were knee jointprostheses and 3 were hip joint prostheses. 2 cases were managed with tumor-bearingbone inactivated in situ and reimplant. According to the Enneking surgical stagingsystem, there wereâ…¡A5,â…¡B7.All patients were examined with both MR and X-ray, and CT or ECT was takenin some of the patients. The chemotherapy of CDP+ADM+/—MTX was applied forall patients with osteosarcoma. After the induction period, definitive surgery of theprimary lesion was performed. The extent of the bone tumor involvement wascalculated with coronal and sagittal images of MR to define the edge of the tumor, and the level of osteotomy was determined as the point in which marrow signalintensity changed from normal to abnormal. The tumor extension on X-ray film wasdefined as the max length of coronal and sagittal plane in the A-P position or lateralposition. For MR, the tumor extension was defined as the point with the marrowsignal intensity changed from abnormal low signal to high signal riching with fat inT₁WI. The scope of tumor was measured between the distal point and proximal pointwhen the tumor was located in the diaphysis and did not invade the joint near by, andif the joint was already involved by tumor, the extension was defined from the jointplane to the point with bone marrow changed in MRI. All scans were analysed by thesame radiologist. The tumor samples were splited longitudinally and measured thetumor invasion in marrow macroscopic. Bone marrow sample were get out in fourpoints include the point of osteotomy, 1cm point near tumor, 1cm and 2cm point nearnormal tissue. Every point was examined microscopic to observe if there were tumorcells. All patients were followed up after surgery, and the function of the limb wasevaluated by the Enneking surgical evaluation system for musculoskeletal tumor.Results: The average of follow-up time of the patients was 14.5 months, rangingfrom 3 to 26 months.11 patients were still alive without disease. One case died 1 yearafter surgery of the multiple metastases. The prosthesis dislocated in 1 case and wasreduced by surgery. All patients with complications obtained good results by activetreatment. According to the Enneking surgical evaluation system for musculoskeletaltumor, the average recovery rate of the limb after surgery was 75%. 1 case was foundtumor cells in the osteotomy plane. The tumor extension in the bone marrow decidedby X-ray film, MRI and pathohistology was (14.0±3.8)cm, (17.5±6.3)cm and(17.0±2.5)cm respectively. There was not significant difference between theextensional scope measured on MRI images and the actual scope through statisticalanalysis, and the former was slightly bigger than the later. Conclusion: The aggressive extension could be measured correctly on MRI,according to which, it is reliable to estimate the surgical margins.