Uso de la RMN de alta resolución para controlar la fusión intervertebral. (Ing.)

Matthijs R. Krijnen, M.D.; Theo H. Smit, Ph.D.; Gustav J. Strijkers, Ph.D.; Klaas Nicolay, Ph.D.; Petra J. W. Pouwels, Ph.D.; Paul I. J. M. Wuisman, M.D., Ph.D.

Abstract

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.