What Surgical Treatment Is Best for Isthmic Spondylolisthesis?: Commentary on an article by Peter Endler, MD, et al.
There are methodology-related questions about this study because of the inherent limitations of registry-based investigations. The data for this study were derived from the oldest comprehensive continuous regional (and in this case national) database on spine surgery of its kind, the Swedish Spine Register (Swespine). This prospective data-gathering tool was organized by the Swedish Society of Spinal Surgeons, which has operated the registry since its inception in 19934. The data entry for baseline demographic and patient-reported outcomes measures is performed by surgeons and their staff at the 42 to 45 registered spine surgery departments in the participating 35 to 39 hospitals. The Swespine organization then independently obtains all additional patient-reported outcomes measures as well as reoperation data and attempts to receive follow-up data at set 1, 2, 5, and 10-year intervals and beyond directly from the patients to ensure data integrity. Their published facility compliance and follow-up rates range from approximately 70% to 80%, which is in keeping with more recently introduced registries5-8. To provide the highest possible assurance of data integrity in this study, the authors actually went back to the clinical source records and could validate correct registry information for 97% of the patients. Also, in anticipation of the possibility of reporting bias due to asymmetric patient follow-up, which is a justified concern, the authors performed a formal comparison of patients who did and those who did not respond to follow-up inquiries by the study organization. They found no substantial differences in demographic data or patient-reported outcomes. In contrast to other studies, this study demonstrated no differences in surgical complications between the fusions done without instrumentation and the 2 surgical instrumentation groups.
Radiographic variables that may influence surgical decision-making are outside the scope of this study. The type of isthmic spondylolisthesis, its severity, instability on dynamic studies, disc height, sacral slope, sagittal alignment, bone quality, and the need for lateral neural element decompression all, or individually, may determine the need for a more definitive surgical stabilization procedure with instrumentation.