Study Design. A prospective study investigated the use of magnetic resonance imaging (MRI) scanning in the assessment of posterior lumbar interbody fusion (PLIF) using carbon fiber cages.
Objective. The aim of the study was to determine whether MRI scans in the coronal plane allow proper evaluation of interbody fusion through carbon cages.
Summary of Background Data. Currently, there is no universally accepted radiologic assessment tool for evaluating fusion status after PLIF.
Methods. Forty-nine levels of 47 patients were studied after PLIF using 98 carbon cages with MRI scans 24 months after surgery. These images were evaluated by two independent radiologists for bridging bony trabeculation through and surrounding the cages.
Results. On coronal planes, the presence of bridging bony trabeculation through the cages was noted in 86 of 98 cages evaluated by observer 1 and 82 of 98 by observer 2. The bone bridging surrounding the cages was inhomogeneous. In six of 49 levels, the presence of low signal intensity zones at the cage end plate interface was observed by both radiologists, regarding three of 23 L4-L5 levels and three of 21 L5-S1 levels.
Conclusions. The results of our study demonstrate that the most reliable radiographic indicator of fusion is the presence of bone bridging through the cages shown on coronal planes.