Long-term Changes in L5-S1 Disks Under the Fusion Region and the Effect of Sagittal Balance on Degeneration

Abstract

Background:The aim of this study was to radiologically assess long-term degeneration in the L5-S1 disks under the fusion region and to research its association with clinical signs in patients with degeneration. Methods:This study evaluated 23 patients who underwent spinal fusion between January 1994 and July 2005. Degeneration in the L5-S1 disks was assessed radiologically over a long-term 10-year follow-up period, and those cases that showed degeneration were further assessed using the Japan Orthopedic Association score and visual analog scale (VAS). Results:Seven of the cases had mild osteophyte development according to radiographic findings. A statistically significant decrease was observed in the front and back disk heights between the preoperative and postoperative measurements (P=0.001 and 0.000). A statistically significant decrease was also observed in the anterior and posterior disk height between the preoperative and postoperative measurements (P=0.007 and 0.007). A significant difference was observed in disk degeneration and facet joint degeneration (P=0.000 and 0.000). On evaluation of radiologic assessments, degeneration was observed in 15 cases (65.3%). Clinical assessment of the cases revealed that 6 patients (26.0%) with radiologic degeneration had lumbar pain of varying degrees, 3 of whom also had pain that spread to the legs; 1 of these caused loss of sensation in the leg. Clinical assessment of pain levels using VAS scoring for all cases revealed an average preoperative score of 8.71, an average early postoperative VAS score of 2.14, and an average long-term follow-up score of 3.35. The recovery rate of the patients was found to be 37.5%, according to Japan Orthopedic Association scoring. The pain level of the patients decreased by almost 4-fold in the postoperative early period and 2.5-fold in the long term. Conclusions:Spinal fusion surgery is an effective treatment method in terms of its clinical results, despite the adjacent segment degeneration that may be identified radiologically in the long term.