The use of high-resolution magnetic resonance imaging for monitoring interbody fusion and bioabsorbable cages: an ex vivo pilot study

Object Interbody fusion is a gradual process of graft resorption and tissue formation, ideally resulting in a bone bridge between two adjacent vertebral bodies. Initially, fibrous tissue and cartilage are formed, which subsequently are replaced by bone through the process of endochondral ossification. When cages and/or their contents are made of resorbable polymers like lactic or glycolic acids, there is a simultaneous process of implant degradation, which is eventually accompanied by reactions in the surrounding tissues. The purpose of this study was to explore the use of high-resolution magnetic resonance (MR) imaging for monitoring tissue differentiation, spinal fusion, cage degradation, and eventually tissue reactions as a function of time. Methods Lumbar vertebral segments obtained in 14 goats with 3, 6, and 12 months of follow up (three, four, and seven animals, respectively) were available from a study of the feasibility of poly(L,D-lactic acid) cages for spinal fusion. Plain x-ray films, MR images, and histological sections were used to evaluate spinal fusion and cage resorption. The first follow-up tests revealed that MR imaging noninvasively provided three-dimensional information on cage placement, cage degradation and bone formation, and that it has potential to differentiate between the various soft tissues. Conclusions Although the magnetic field strength and thus the resolution used were higher than normal in clinical practice, MR imaging appears to be a promising modality for the noninvasive clinical follow up of patients who undergo fusion with resorbable cages. Tissue reactions were not encountered in this study, and thus could not be evaluated

Risk Factors for Blood Loss During Sacral Tumor Resection

Extensive hemorrhage is a serious complication during sacral tumor resection. Identifying the risk factors predicting the possibility of extensive hemorrhage would be important to predict which patients would need large amounts of transfused blood intraoperatively and postoperatively and which patients would need blood control by vascular occlusion. We retrospectively reviewed 173 patients who underwent sacral tumor resection performed at our institute between 2003 and 2007. Patients with an estimated total blood loss greater than 3000 mL were classified as having a large amount of blood loss. Sixty-nine (39.88%) patients had blood loss greater than 3000 mL. Male gender, excessive tumor blood supply, tumors involving the S2 body and cephalad to the S2 body, tumor volume greater than 200 cm3, aorta occlusion, surgical approach, reconstruction, and operative time were associated with a large amount of blood loss. Tumors cephalad to the S2-S3 disc space (odds ratio, 3.840), tumor volume greater than 200 cm3 (odds ratio, 3.381), and excessive blood supply (odds ratio, 2.281) independently predicted a large amount of blood loss. Sacral tumors that invaded cephalad to the S2-S3 disc space with a volume greater than 200 cm3 and an excessive blood supply were likely to have a large amount of blood loss during resection