Radiologic evaluation of adjacent superior segment facet joint violation following transpedicular instrumentation of the lumbar spine

Study Design. The location of pedicle screws in relation to adjacent superior segment facet joints in 106 patients after lumber spinal fusion was assessed using computed tomography and plain radiographs. Objectives. To document the incidence of adjacent superior segment facet joint violation following transpedicular instrumentation in the lumber spine. Summary of Background Data. Review of the literature failed to show any documented study examining this incidence. Methods. A total of 106 patients (212 top-level facet screws) undergoing lumber spinal fusion surgery using transpedicular instrumentation between 1996 and 1999 were prospectively evaluated with a computed tomography scan and plain radiographs at 6 months following surgery. These were blindly and independently evaluated by a consultant radiologist and a spinal research fellow to document the incidence of superior segment facet joint violation. Calculation of the kappa coefficient and chi(2) analysis were carried out. Results. The spinal research fellow noted the incidence of facet joint violation on the computed tomography scan to be present in 20% of the screws and 32% of the patients, whereas the consultant radiologist noted this to be the case in 23% and 35% respectively. The kappa coefficient for computed tomography scan as 0.88 whereas for the plain radiographs it was 0.39. The incidence of facet joint violation was noted to be independent of the sex, level and diagnosis. There was also an almost uniform incidence in each of the years from 1996 to 1999. Conclusion. Facet joint violation occurred in just >30% of the patients and 20% of the screws in this study. This, therefore, raises the theoretical possibility of long-term deterioration in the clinical results following the use of transpedicular instrumentation.