Radiological evaluation of lumbosacral spine for post discectomy segmental instability

Aim To establish presence of segmental instability in patients operated with standard discectomy comparing measurement of translation and rotation on postoperative functional radiographs of lumbosacral spine with reference values,and to explore difference between patients operated on one or two levels. Methods The study included 71 patients, who were operated due to herniated lumbar disc. They were divided into two groups operated on one level (group A) or two adjacent levels (group B). All patients had been imaged in a standing position with functional lateral radiography. Radiographic images were digitized and then computerized measurement of translation and rotation was made. Measurement data were compared between the groups and with reference values obtained in healthy adults. Results Standard lumbar discectomy leads to an increase in translation, however, it reached statistical significance only for L4/L5 level and a decrease of rotation, which showed statistical significance for all samples, relative to the reference values. There was no statistically significant difference in the values of translation and rotation between the groups for corresponding levels, except for the value of the rotation for L4/L5 level as adjacent, unoperated level. Comparison of translation and rotation between the operated and adjacent levels did not show a statistically significant difference. When it comes to comparing the measured and predicted translation, there was a statistically significant difference only at the L5/S1 as anunoperated level. Conclusion Standard discectomy does not lead to radiologically significant segmental instability, and two-level surgery has not caused more pronounced signs of instability comparing to onelevel surgery.