| Although traditional lumbar fusion surgery is effective in alleviating symptoms,it may also lead to certain issues,such as stress concentration and increased burden on adjacent segments,which have been associated with an increasing number of reports of adjacent segment degeneration with prolonged follow-up time."Dynamic-static integration " and "paying equal attention to bone and soft tissue " are important theories in traditional Chinese orthopedics.Through further elaboration and expansion of their meanings,we believe that these two theories are reflected in the motion and stability of spinal segments.Fusion surgery disrupts the balance between motion and stability of spinal segments,leading to impacts on the surrounding bone and soft tissue.Non-fusion surgery provides stability to spinal segments while preserving some degree of mobility,which to some extent maintains a balance between motion and stability of spinal segments.Previous research has indicated that the Isobar TTL system is effective in treating mild to moderate lumbar degenerative disease using non-fusion surgery,reducing surgical trauma,intraoperative blood loss,and shortening postoperative recovery time.Additionally,it may potentially delay the onset of adjacent segment degeneration.The Isobar TTL system has been upgraded to the Isobar EVO system,which offers higher mobility in response to concerns raised by some scholars about the ability of the Isobar TTL system to delay adjacent segment degeneration due to its relatively low mobility.However,increased mobility may lead to reduced segment stability,thereby increasing the risk of adjacent segment degeneration.Therefore,the current focus of research in non-fusion surgery is on balancing segment mobility and stability,and determining whether increasing the mobility of the fixed segment will have a positive impact on adjacent segments.Objective1 A systematic review and meta-analysis were conducted to evaluate the clinical efficacy and biomechanical characteristics of the Isobar system in the treatment of lumbar degenerative diseases,in order to identify the current shortcomings in research on the Isobar system.2 Assessing the clinical efficacy and radiological parameters of the Isobar system,with varying degrees of mobility,in treating single-segment mild to moderate lumbar degenerative disease.This evaluation will be based on the principles of "dynamic-static integration"and "equal attention to bone and soft tissue ".Additionally,the study aims to identify any limitations or gaps in existing research on the Isobar system.3 Investigating whether the Isobar system with varying degrees of mobility,as an internal fixation system,will have a different impact on adjacent intervertebral disc MRI images in the treatment of single-segment mild to moderate lumbar degenerative disease.4 Investigating whether the Isobar system with varying degrees of mobility,as an internal fixation system,will have a different impact on adjacent facet joints and paraspinal muscle MRI images in the treatment of single-segment mild to moderate lumbar degenerative disease.5 Investigating whether the Isobar system with varying degrees of mobility,as an internal fixation system,will have a different impact on bone density of both the fixed and adjacent segments in the treatment of single-segment mild to moderate lumbar degenerative disease.6 Exploring the application of the " dynamic-static integration " and " paying equal attention to bone and soft tissue " theories in both holistic and local perspectives during the posterior Hybrid surgery of the lumbar spine.Methods1 A systematic review was conducted by searching all relevant literature on the clinical application and biomechanical research of the Isobar system in PubMed,EMbase,the Cochrane Library,CNKI,Wanfang,VIP,and the China Academic Journals Full-text Database(CAJ)since their inception.A meta-analysis was also performed on randomized controlled clinical studies comparing the use of the Isobar system for non-fusion treatment of lumbar degenerative disease with posterior lumbar fusion surgery for lumbar degenerative disease.2 A retrospective cohort study was conducted to compare the mid-term clinical efficacy and radiological results between patients with mild to moderate lumbar spinal stenosis and lumbar disc herniation who underwent single-segment posterior lumbar interbody fusion(PLIF)combined with either the Isobar TTL or Isobar EVO system for non-fusion fixation.Clinical and imaging data were collected through telephone and outpatient follow-up visits over the past few years.3 The study used a case-control method to retrospectively analyze the medical records and lumbar X-ray and MRI radiological data of patients who underwent single-segment posterior lumbar interbody fusion combined with either the Isobar TTL or Isobar EVO system at the department.The study compared the fixed segment range of motion(ROM),intervertebral disc height of the fixed and adjacent segments,Pfirrmann grade of intervertebral disc signal,and adjacent segment nuclear volume between the two groups before and after surgery.It also analyzed the relationship between activity and intervertebral disc degeneration in the fixed and adjacent segments.4 The study further compared the degree of facet joint degeneration in the fixed and adjacent segments before and after surgery,as well as the difference in paraspinal muscle fat infiltration in the adjacent segments before and after surgery.5 Additionally,the study retrospectively analyzed all medical records and lunbar CT radiological data of patients who underwent L4/5 segment posterior lumbar interbody fusion combined with either the Isobar TTL or Isobar EVO system at the department.The difference in Hounsfield unit(HU)values of the vertebral trabecular bone in the upper instrumented vertebra(UIV),lower instrumented vertebra(LIV),and adjacent vertebra(UIV+1)before and after surgery was compared between the two groups,as was the correlation between activity and vertebral HU value.6 Finally,the mid-term clinical efficacy of patients with double-segment lumbar spinal stenosis who underwent Isobar Hybrid surgery or PLF surgery was retrospectively analyzed using a case-control method to compare the lumbar X-ray and MRI radiological differences in the fixed and adjacent intervertebral discs between the two groups and the difference in intervertebral disc signal of the segments that were not treated in both groups.Results1 The literature search results indicate that a total of 41 studies have extensively discussed the Isobar system from clinical and biomechanical perspectives.Among them,33 clinical studies have investigated the applications of the Isobar system in both fusion and non-fusion surgeries,while 9 studies have conducted detailed tests on the biomechanical characteristics of the Isobar system for external fixation through cadaveric research and finite element analysis.A meta-analysis of 7 RCTs comparing the clinical and radiographic differences between Isobar non-fusion surgery and PLIF surgery showed that Isobar non-fusion internal fixation had advantages over PLIF surgery in terms of surgical time,intraoperative blood loss,preservation of overall and fixed segment ROM of the lumbar spine,and the incidence of adjacent segment disease after surgery.2 At the last follow-up,both the TTL group and the EVO group showed significant improvements in VAS scores for lumbar pain and leg pain,JOA score,and ODI compared to preoperative values,with statistically significant differences(P<0.05).The range of motion of the fixed segments in both groups was significantly lower than preoperative values(P<0.05),while the range of motion of the upper adjacent segments was significantly higher than preoperative values(P<0.05).When comparing between the two groups,the EVO group showed significantly higher range of motion of the fixed segments than the TTL group(P<0.05),and significantly lower range of motion of the upper adjacent segments than the TTL group(P<0.05),except for the VAS scores for lumbar pain and C-LSDI,which were lower in the EVO group than in the TTL group(P<0.05).3 One month after surgery,the DH of the fixed segments in both the TTL group and EVO group significantly increased compared to preoperative values(P<0.05),while the DH of the upper adjacent segments showed no significant changes(P>0.05).One year after surgery,the intervertebral height of the fixed segments in both groups was significantly higher than preoperative values(P<0.05).At the last follow-up,the DH of the fixed segments in both groups remained higher than preoperative values,and the intervertebral height of the upper adjacent segments in the TTL group was significantly lower than preoperative values(P<0.05),with significant differences in the Pfirrmann grade between the upper adjacent segments in both groups(P<0.05).In subgroup analysis of patients who underwent only decompression and fixation without treating the intervertebral discs of the fixed segments,there was no difference in the Pfirrmann grade of the intervertebral discs of the fixed segments between the two groups at the last follow-up.At the last follow-up,the nucleus pulposus volume of the upper adjacent segments in the TTL group significantly decreased compared to preoperative values,while no significant changes were observed in the EVO group(P>0.05).In terms of inter-group comparison,the nucleus pulposus volume of the upper adjacent segments in the EVO group was significantly higher than that in the TTL group(P<0.05).In the correlation analysis,there was a positive correlation between the nucleus pulposus volume of the upper adjacent segments and the range of motion of the fixed segments at the last follow-up in both groups.The correlation was weak in the TTL group(r=0.397,P<0.05)and strong in the EVO group(r=0.765,P<0.05).4 At the final follow-up,the Fujiwara grading of the facet joints on both sides of the fixed segments in both the TTL group and EVO group was significantly increased compared to preoperative values,with no significant differences between the groups(P>0.05).The Fujiwara grading of the facet joints on both sides of the upper adjacent segments in the TTL group was significantly increased compared to preoperative values(P<0.05),while there was no significant difference in the EVO group(P>0.05).At the final follow-up,the Goutallier grading of the paraspinal muscles in the TTL group was significantly increased compared to preoperative values(P<0.05),while there was no significant difference in the EVO group(P>0.05).5 At the last follow-up,there was no significant difference in Hounsfield Units(HU)values between the two groups for the upper and lower instrumented vertebrae(UIV and LIV)compared to preoperative values(P>0.05).However,HU values for the upper adjacent vertebrae were significantly decreased compared to preoperative values in both groups(P<0.05).Between-group comparisons showed no difference in HU values for UIV and LIV at the last follow-up(P>0.05),but the HU values for the upper adjacent vertebrae in the EVO group were significantly higher than those in the TTL group(P<0.05.There was a positive correlation between range of motion(ROM)of the fixed segment(L4/5)and HU values of the upper adjacent vertebrae(r=0.382,P<0.001),as well as between ROM and UIV HU values(r=0.624,P<0.001),but no correlation with LIV HU values.6 The amount of intraoperative bleeding and the operation time were both higher in the PLF group than in the Hybrid group(P<0.05).At the last follow-up,both groups showed significant improvements in VAS scores for low back pain and leg pain,JOA score,ODI,and C-LSDI compared to preoperative scores(P<0.05).In terms of inter-group comparison,the C-LSDI score in the Hybrid group was significantly lower than that in the PLF group at the last follow-up(P<0.05).Regarding imaging results,the fixed segment activity of both groups decreased significantly at the last follow-up compared to preoperative levels(P<0.05),and the fixed segment activity was higher in the Hybrid group than in the PLF group(P<0.05).The ROM of the upper adjacent segment increased in both groups compared to preoperative levels(P<0.05),and the upper adjacent segment activity was significantly higher in the PLF group than in the Hybrid group(P<0.05).The overall lumbar spine activity decreased in both groups compared to preoperative levels,and the decrease in the Hybrid group was significantly greater than that in the PLF group(P<0.05).The height of the intervertebral space in the upper adjacent segment decreased significantly in both groups compared to preoperative levels(P<0.05),and the decrease was greater in the Hybrid group than in the PLF group(P<0.05).The change in Pfirrmann grade in the upper adjacent segment showed that the degeneration rate in the Hybrid group was 16.12%(5/31),which was not statistically different from preoperative levels(P>0.05).The degeneration rate in the PLF group was 34.28%(12/35),which was statistically different from preoperative levels(P<0.05).Conclusion1 Compared with the Isobar TTL system,the Isobar EVO system has less impact on the activity of the adjacent segment and has advantages in delaying the decrease of adjacent segment disc height and improving Pfirrmann grade of adjacent segment disc degeneration.Additionally,the Isobar system can also rehydrate the degenerated intervertebral discs in some fixed segments(only for decompression segments).2 Moderately increasing the activity of the fixed segment using the Isobar system may be more beneficial in delaying facet joint degeneration and paraspinal muscle fat infiltration of the adjacent segment.3 The Isobar system can maintain the bone density of the fixed segment in single-segment non-fusion surgery.In addition,moderately increasing the activity of the fixed segment using the Isobar system may be more beneficial in delaying the decline of adjacent segment vertebral body bone density.4 Guided by the theories of "dynamic and static combination " and " paying equal attention to bone and soft tissue ",the Isobar Hybrid surgery for double-segment lumbar spinal stenosis patients is superior to PLF surgery in improving the C-LSDI.Isobar Hybrid surgery can preserve a certain degree of lumbar and fixed segment activity,reduce compensatory activity of adjacent segments,and may have a role in delaying adjacent segment and non-fusion segment disc degeneration. |
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