Value Of Magnetic Resonance Imaging To Evaluate Instrumented Posterior Lumbar Interbody Fusion

Objective To investigate the clinical value of magnetic resonance imaging (MRI) to evaluate instrumented posterior lumbar interbody fusion (PLIF).Method From March2008to March2012, thirty-one patients with degenerative lumbar diseases and undertaking mono-segment transforaminal lumbar interbody were retrospectively analyzed. These patients complained unresolved or recurrent pain. Lumbar anteroposterior and lateral film, CT scans with reconstruction and MRI were used to evaluate the status of interbody fusion3months,6months,1year and2years postoperatively respectively.Results The fusion rates evaluated by lumbar X-ray, CT scans and MRI in3months,6months,1year and2years after surgery were16.1%,6.45%,0%;80.7%,61.3%,58.1%;96.8%,83.8%,87.1%; and100%,96.8%and96.8%respectively. The comparison of fusion rates in3months after operation with those in6month after operation was statistically different for X-ray, CT scans and MRI evaluation. When the fusion rates of6months postoperatively were compared with those of1years postoperatively, they were only different for MRI, but not CT scans and X-ray. And the comparison of fusion rates between1year and2years after operation were comparable for all the three methods, but CT scans and MRI detected newly formed bone around the fusion cage in several cases until the last imaging follow-up. When the results evaluated by different evaluating methods were compared at the four different time point, no statistical differences were found. The results from CT scans and MRI had high consistence (90.3%-100%).Conclusion MRI can accurately determine the fusion status of lumbar interbody fusion by assessing the signal changes of the subchondral bone and the continuity of the signal across the fusion. A follow-up of longer than2years is needed for MRI evaluation.