Comparisons Of Dynesys Stabilization And Posterior Lumbar Interbody Fusion For L4/5 Segment Lumbar Degenerative Disease- MRI Index For The Evaluation Of Early Adjacent Disc Degeneration

Objective:The aim of this prospective randomized study was to compare the radiological and clinical outcome between Dynesys and posterior lumbar interbody fusion(PLIF) in the treatment of L4/5 single –segment lumbar degenerative disease. Evaluate the value of MRI index in the assessment of early adjacent segment degeneration.Methods :A prospective randomized study of methods between January 2013 and April 2014, 50 cases of lumbar degenerative disease were randomly assigned in a 1:1 ratio to Dynesys dynamic fixation group(group A) or PLIF fusion group(group B). The operation time,intraoperative blood loss, length of hospital stay of the two groups were compared. The outcome was evaluated by Oswestry disability index(ODI) and visual analogue scale(VAS), Range of motion(ROM) of lumbar segments, and Pfirrmann,UCLA grade classification, and early adjacent segment degeneration was evaluated by MRI index.Results:1. 50 cases of 45 patients(22 cases of group A, group B 23 patients) were followed up for 12 to 24 months, an average of 14 months. There was no significant difference between the two groups in terms of the demographic characteristics(P>0.05). The average of operative time, intraoperative blood loss, length of hospital stay in the Dynesys groupwas 98 minutes, 190.5ml, 10.7 days,while that in the PLIF group was 130 minutes,242.7ml, 12.9 days. There was difference in the average of operative time between groups(P<0.05),while in terms of intraoperative blood loss,length of hospital stay the difference was not significant(P>0.05).2. The ODI and VAS score significantly improved in both groups at the final follow-up(P<0.01), but the difference between groups was not significant(P>0.05).3. The average ROM of surgical segments in A group was 6.5°,and reduced to 4.6°at the final follow-up(P<0.05). The average ROM of surgical segments in B group was7.5°and reduced to 0°at the final follow-up. The difference between preoperative and last follow-up in the ROM of proximal adjacent segments in A group was not significant(P>0.05). The average ROM of proximal adjacent segments in B group was 7.39°and increased to 9.70°at the final follow-up, the changes were significant different(P<0.01),and the difference between groups was significant(P<0.05). There is no significant difference in the ROM of distal adjacent segments in both groups(P>0.05) at the final follow-up, the difference between groups was not significant(P> 0.05).4. There were no significant changes of Pfirrmann grade between preoperative and last follow-up in both groups(P>0.05). According to University of California at Los Angeles Grading Scale, there were no radiological adjacent degeneration cases in both groups.5. The difference between preoperative and last follow-up in the MRI index of proximal adjacent segments in A group was not significant(P> 0.05). The average MRI index of proximal segments in B groups was 0.685 and induced to 0.549 at the final follow-up, the difference was significant(P<0.05), and the changes were significant between groups(P<0.05). There is no significant difference in the MRI index of distal adjacent segments in both groups(P>0.05) at the final follow-up, the difference between groups was not significant(P> 0.05).6. The difference between preoperative and last follow-up in the Signal intensity and Area of central bright of both proximal and distal adjacent segments in A group was not significant, and the difference between groups was not significant(P>0.05).The Signalintensity of central bright of proximal adjacent segments in B group was 0.31 and induced to 0.27 at the final follow-up, the difference was significant(P<0.05), and the changes were significant between groups(P<0.05), while the Area of which was not significant.The Signal intensity and Area of distal adjacent segments in B group were not significant, and the difference between groups was not significant(P>0.05).Conclusions :1. Both Dynesys stabilization and posterior lumbar interbody fusion for L4/5 single–segment lumbar degenerative disease can achieve a satisfactory clinical outcomes.Dynesys dynamic fixation in patients with the length of hospital stay, operative time and intraoperative blood loss was superior to lumbarf usion surgery, though there is no significant difference in the blood loss and the length of hospital stay(P> 0.05).2. Dynesys system can preserve a greater ROM than PLIF at the operated level,reducing the increase of ROM at adjacent segments. There was greater impact on the ROM proximal adjacent segments after lumbar fusion surgery, the increasing of adjacent segment ROM is an important factor which may accelerate adjacent disk degeneration.3. MRI index is more sensitive to the early disc degenerative changes than Pfirrmann or UCLA grade classification, and it can quantify the degree of disc degeneration. The decrease of the Signal intensity of central bright is the main cause of the decline of MRI index.