Correlation between surgical segment mobility and paravertebral muscle fatty infiltration of upper adjacent segment in single-segment LDD patients: retrospective study at a minimum 2 years’ follow-up

OBJECTIVE: The purpose of this study was to investigate the relationship between surgical segment mobility and fatty infiltration of the adjacent segment paravertebral muscles in patients with single-segment lumbar degenerative disease (LDD) who underwent decompression with fusion or dynamic stabilization. METHODS: Retrospective analysis of patients who underwent lumbar decompression combined with titanium rod fixation intertransverse fusion (PITF group), Isobar TTL dynamic stabilization (TTL group) or Isobar EVO dynamic stabilization (EVO group) for single-segment lumbar degenerative disease, from March 2012 to July 2018. The preoperative and final follow-up clinical indexes C-LDSI and the measured imaging indexes (range of motion of the surgical segment and the upper adjacent segment, and Goutallier grade of the upper adjacent segment) were counted, and the differences between the preoperative and final follow-up indexes were compared. RESULTS: According to the inclusion and exclusion criteria, 68 patients were included in this study, 21 in the PITF group, 24 in the TTL group, and 23 in the EVO group. At the final follow-up, the C-LSDI score had significantly higher in the PITF group than the TTL and EVO groups, and the C-LSDI score was a very strongly negatively correlated with ROM of surgical segment (r=-0.7968, p < 0.001). There was a strong negative correlation between surgical segment and upper adjacent segment mobility (r = -0.6959, p < 0.001). And there was a very strong negative correlation between ROM of surgical segment and upper adjacent segment paravertebral muscle Goutallier classification (r = -0.8092, p < 0.001), whereas the ROM of the upper adjacent segment was strong positive correlated with the Goutallier classification (r = 0.6703, P < 0.001). CONCLUSION: Compared with decompression combined with rigid fusion, decompression combined with dynamic fixation for single-segment lumbar degenerative disease can significantly reduce postoperative low back stiffness. And a certain range of increased mobility of the dynamic stabilization device can effectively reduce the compensatory mobility of the upper adjacent segment and slow down the fatty infiltration of the paravertebral muscle in the adjacent segment.