腰椎融合_非融合技术治疗L4_5_省略_疾病的疗效及对相邻节段退变的影响_魏富鑫
临床论著
腰椎融合/非融合技术治疗L4/5退变性疾病的
疗效及对相邻节段退变的影响
魏富鑫1,钟锐1,潘希敏2,孙海兴2,王乐1,崔尚斌1,刘少喻1
(1中山大学附属第一医院脊柱外科;2放射科510700广州市)
【摘要】目的:比较后路腰椎椎间融合术(posterior lumbar interbody fusion,PLIF)与棘突间动态固定术(Wallis)治疗腰椎间盘突出症/椎管狭窄症合并椎间失稳的临床效果及对相邻节段退变的影响。方法:回顾性分析2007年6月~2010年7月我科手术治疗L4/5腰椎间盘突出症/椎管狭窄症合并椎间失稳患者61例,其中腰椎间盘突出症患者29例,腰椎管狭窄症患者32例;采用PLIF术式固定融合患者32例,棘突间Wallis动态固定患者29例。术前、术后1个月、1年以及末次随访时,采用JOA评分及腰功能障碍指数(ODI)评估临床疗效;根据UCLA标准对相邻节段L3/4及L5/S1椎间盘进行退变分级;利用T1ρ-MRI技术量化相邻节段椎间盘髓核T1ρ值。结果:随访时间48~77个月,平均61.3个月,其中PLIF组和Wallis组平均随访时间分别为63.4和59.6个月,差异无统计学意义(P>0.05)。术前2组患者年龄、性别、疾病构成比、相邻节段椎间盘退变分级及相邻节段椎间盘T1ρ值均无明显差异(P>0.05)。末次随访时,PLIF组与Wallis组ODI评分改善率分别为76.1%、78.5%,JOA评分改善率分别为69.2%、75.0%,均无统计学差异(P=0.78,0.85)。末次随访时,PLIF组L3/4以及L5/S1节段椎间盘退变分级差异均无统计学意义(P=0.91,0.70)。术前、术后1个月、末次随访时,PLIF和Wallis组L3/4椎间盘T1ρ值分别为115.4±8.9ms、111.6±12.3ms、91.6±11.1ms和112.4±10.0ms、109.9±9.2ms、103.5±10.8ms,L5/S1椎间盘T1ρ值分别为95.4±7.7ms、94.6±9.6ms、88.1±12.6ms和96.3±9.2ms、95.4±8.5ms、91.3±11.4ms,两组术后1个月L3/4、L5/S1椎间盘T1ρ值与术前比较均无统计学差异(PLIF组:P=0.67,0.75;Wallis组:P=0.72,
0.64);末次随访时,PLIF组L3/4椎间盘T1ρ值明显低于Wallis组,差异有统计学意义(P=0.02),而L5/S1椎间
盘T1ρ值差异无统计学意义(P=0.89)。结论:PLIF术式与棘突间动态固定(Wallis)治疗腰椎退变性疾患均可获得满意的中期临床疗效,而后者在减少固定术后上位相邻节段退变方面更具优势。
【关键词】腰椎;内固定;相邻节段;椎间盘退变;磁共振;T1ρ序列
doi:10.3969/j.issn.1004-406X.2014.10.06
中图分类号:R681.5,R687.3文献标识码:A文章编号:1004-406X(2014)-10-0892-08
Clinical outcome of different lumbar instrumentation with or without fusion and its effect on adjacent segment degeneration in lumbar degenerative diseases/WEI Fuxin,ZHONG Rui,PAN Ximin,et al//Chinese Journal of Spine and Spinal Cord,2014,24(10):892-899
【Abstract】Objectives:To compare the clinical effects of posterior lumbar interbody fusion(PLIF)and Wallis interspinous implant in lumbar disc herniation or stenosis complicated with instability,and their effects on ad-jacent segment degeneration.Methods:A retrospective study of61patients undergoing PLIF or interspinous Wallis placement at L4/5segment was carried out.Among these,29patients were diagnosed as lumbar disc herniation and32patients as lumbar stenosis,all of them were complicated with lumbar instability.All pa-tients presented with low back pain.In this study,32cases underwent PLIF,and29underwent interspinous Wallis placement.The clinical results were assessed and compared by JOA score and Oswestry disability in-dex(ODI)preoperatively,1month and1year postoperatively and at the final follow-up.The degenerative grades of adjacent segments of L3/4and L5/S1were recorded by using UCLA(university of California at Los Angeles)grading system.The T1ρvalues of nucleus pulposus in adjacent segments of L3/4and L5/S1were
基金项目:国家自然科学基金-广东联合基金项目(编号:U1032001);国家自然青年科学基金项目(编号:81401839);广东省科技计划项目(编号:2010B031600203);广东省自然科学基金项目(编号:S2013010015775);广州市黄埔区科技支撑计划项目(编号:201329-04)
第一作者简介:男(1981-),医学硕士,主治医师,研究方向:脊柱外科
电话:(020)82379597E-mail:weifuxin@https://www.360docs.net/doc/6d14680968.html,
also measured at the same time points.Results:The average follow-up period was61.3months(range:48-77 months),and the average follow-up period for the PLIF and Wallis group was63.4and59.6months respectively,which showed no significant difference between groups(P>0.05).There were no significant differences with respect to the age,sex ratio,disease ratio,degenerative grading and T1ρvalues of adjacent segment discs preoperatively(P>0.05).The recovery rate of ODI,JOA score for PLIF and Wallis groups was 76.1%,69.2%and78.5%,75.0%respectively,which showed no significant difference between2groups(P= 0.78,0.85).According to the UCLA classification,no significant difference was found in the degenerative grading for adjacent segment of L3/4and L5/S1at the final follow-up(P=0.91,0.70).The T1ρvalue of L3/4 disc in the PLIF group preoperatively,1month postoperatively and at the final follow-up was115.4±8.9ms, 111.6±12.3ms and91.6±11.1ms respectively,and112.4±10.0ms,109.9±9.2ms and103.5±10.8ms in the Wallis group respectively.The T1ρvalue of L5/S1disc in the PLIF group preoperatively,1month postoperatively and at the final follow-up was95.4±7.7ms,94.6±9.6ms and88.1±12.6ms respectively,and96.3±9.2ms,95.4±8.5ms and91.3±11.4ms respectively.There were no significant differences in the T1ρvalue of L3/4and L5/S1disc compared with preoperative ones,at1month after operation in each group(PLIF:P=0.67,0.75; Wallis:P=0.72,0.64).The T1ρvalue of L3/4in PLIF group significantly decreased at the final follow-up, compared with that in the Wallis group(P=0.02).However,there was no significant difference in the T1ρvalue of L5/S1at the final follow-up between2groups(P=0.89).Conclusions:Both of the PLIF and the interspinous placement can achieve satisfactory clinical results for lumbar degenerative disease at the midterm follow-up,however the interspinous placement is superior to the PLIF in delaying the cranial adjacent segment degeneration.
【Key words】Lumbar vertebrae;Internal fixation;Adjacent segment;Intervertebral disc degeneration;Magnetic Resonance;T1ρ
【Author′s address】Department of Spinal Surgery,the First Affiliated Hospital,Sun Yat-Sen University, Guangzhou,510700,China
后路腰椎融合术(posterior lumbar interbody fusion,PLIF)是目前治疗腰椎退变性疾患合并失稳的常用术式之一[1]。由于该术式导致相邻节段退变(adjacent segment pathology,ASP)的报道屡见不鲜[2~5]并引起关注,有学者提出非融合固定技术[6、7](即动态固定),其中棘突间固定系统(如Wallis固定系统)应用较多,其目的是在限制该节段异常活动的同时,保证可控制范围内的脊柱运动,改变运动节段的负荷模式,从而降低固定术后相邻节段退变的发生率[8、9]。然而,关于棘突间动态固定系统是否会阻止或延缓相邻节段椎间盘退变仍存在一定争议[10、11]。针对上述问题,我们回顾性分析2007年6月~2010年7月我院采用PLIF 术式或棘突间Wallis动态固定术治疗的61例L4/5腰椎间盘突出症/椎管狭窄症伴椎间失稳的患者,比较其临床效果,并通过T1ρ-MRI技术定量评价相邻节段椎间盘髓核蛋白多糖(PGs)含量变化,目的在于阐述上述两种腰椎固定术式治疗腰椎退变性疾患的临床效果,并评估其对固定术后相邻节段退变的影响。1资料与方法
1.1一般资料
本组男32例,女29例,年龄40~59岁,平均51.6岁,其中L4/5椎间盘突出症(lumbar disc herniation,LDH)29例,腰椎管狭窄症(lumbar spinal stenosis,LSS)32例,均伴有L4/5椎间失稳(动力位X线片显示椎体之间成角超过11°或滑移>3mm,但滑脱小于Ⅰ度),均存在难以忍受的腰痛症状。症状起始至手术时间为3~25个月,平均16.3个月。所有患者术前腰椎MRI及X线检查均排除相邻节段L3/4及L5/S1节段退变、滑脱、失稳,所有患者术前L3/4、L4/5节段椎间盘按UCLA (University of California at Los Angeles Grad-ing)标准[12]分级(表1),均≤Ⅱ级。其中32例患者接受PLIF术式,29例采用棘突间Wallis动态固定术。
1.2手术方法
麻醉后均取俯卧位,腰稍前凸位,后正中入路,PLIF组选择有下肢神经症状侧,按常规行椎板间开窗减压(双侧者行双侧减压)、神经根松解
并髓核摘除,刮除相邻椎体软骨板后,将自体骨塞入椎间融合器,行椎体间融合并椎弓根螺钉固定术。Wallis 组于症状侧向对侧掀开棘上韧带,咬除棘间韧带后切除黄韧带,对于合并侧隐窝狭窄的患者,行椎板开窗减压,直至神经根彻底松弛;对于椎间盘突出明显的患者,于根性症状侧椎板开窗减压并摘除突出的髓核,然后修整棘突上下缘并打磨椎板,用撑开器撑开试模后放置合适型号的棘间垫,捆绑带穿过需要固定节段的上下棘间韧带时应尽可能靠近棘突的上缘或下缘,随后将锁扣逆时针旋转360°后固定在棘间垫上,听到清脆的“啪”的声音提示锁扣已固定牢靠,顺时针对抗锁紧2条捆绑带后,再次检查锁扣是否牢靠固定在棘间垫上,并将钛合金圆环压实在距离锁扣
1~2mm 的位置,用巾钳在固定节段的上下棘突打
孔,并将剥离的棘上韧带复位后通过棘突与对侧棘上韧带缝合。常规放置引流后关闭切口。
1.3术后处理
术后均常规应用抗生素1d ,术后24~48h 拔
除引流管,12~14d 拆线。术后3~5d 佩戴外固定支具下床活动,并继续戴支具8~12周。3个月内避免弯腰活动,3个月后恢复正常活动。
1.4评价方法
术前、术后1个月、术后1年及末次随访时均
进行影像学检查及临床评估。
1.4.1影像学评价所有患者均行腰椎MRI 及X 线片检查。X 线检查包括腰椎正、侧位片及术后3
个月后的动力位片检查。MRI 检查使用Philips
1.5Tesla MR 仪扫描;采用8通道腰椎线圈。T1WI 和T2WI 采用快速自旋回波(FSE )脉冲序列、T2-mapping 技术处理前的T2WI 图像采集采用多回波SE 序列、T1ρ-mapping 采用快速自旋锁
定脉冲序列。为降低内固定材料对扫描序列的影响,选择短TE ,并增加带宽的方式扫描。具体参数为:T1WI :TE 8ms ,TR 540ms ,视野(FOV )200mm ,层厚2~3mm ;T2WI :TE 100ms ,TR 1900ms ;进行
MRI 检查后,收集各项相关的数据。采用Philips 公司提供的后处理软件对数据进行处理得到T1ρ值图,再用Image J 软件手动绘制髓核感兴趣区、
伪彩化处理、图像融合并测定T1ρ值(ms ),每个椎间盘由3位不同研究人员各测1次,取平均值。感兴趣区的绘制在T2WI 上椎间隙最大的中间层面进行,尽量包括整个髓核区中心,最大限度减少感兴趣区域面积,以减小内固定材料对扫描序列的影响。
1.4.2临床评价采用Oswestry 功能障碍指数(Oswestry dysfunctional index ,ODI )、JOA 评分对
患者进行临床评估。术后改善率采用Hirabayashi 方法计算:改善率=(术后评分-术前评分)/(总分-术前评分)×100%。
1.5统计学分析
应用SPSS 16.0统计软件包进行统计学处
理,计量资料各变量用x ±s 来表示。各组内术前、术后及末次随访数据比较采用方差分析(one-way
ANOVA )及均数间多重比较LSD-t 检验(least significant difference ),两组间随访时间、相同时
间点T1ρ值比较采用t 检验;两组间患者性别比例、疾病构成比以及临床功能改善率比较采用χ2检验,两组间邻近节段椎间盘退变分级比较采用
Wilcoxon 秩和检验。P <0.05为差异有统计学意
义。
2结果
Wallis 组与PLIF 组患者年龄、性别比例、疾
病构成比、术前相邻节段椎间盘退变分级以及椎间盘T1ρ值均无统计学差异(P >0.05,表2、3)。术中PLIF 组发生硬膜撕裂1例,给予修补后未见明显脑脊液漏发生;术后PLIF 组发生泌尿系感染2例,经应用抗生素治愈。Wallis 组术中、术后均无并发症发生。所有患者术后腰痛及神经损害症状均获得明显缓解,随访期间均无内固定失败发生。随访时间为48~77个月,平均为61.3个月,其中
PLIF 组随访48~77个月,平均63.4个月;Wallis 组随访50~74个月,平均59.6个月,差异无统计学意义(P >0.05)
表1
椎间盘退变UCLA 分级标准
Table 1University of California at Los Angeles grading scale for intervertebral space degeneration
Ⅰ---Ⅱ+--Ⅲ±+-Ⅳ±
±
+
注:-,阴性;+,阳性;±,阴性或阳性
Note:-,negative;+,positive;±,negative or positive
分级
Classification
椎间隙狭窄
Disc-space narrowing
骨赘形成
Osteophytes
终板硬化
End plate scleosis
表3两组患者术前、术后和末次随访时L3/4和L5/S1节段T1ρ值测量结果
(x ±s ,ms )
Table 3The radiological results of L3/4and L5/S1segments at different time points
L3/4
L5/S1
术前
Preop
术后1个月
1m postop 术后1年12ms postop
末次随访
Last follow-up
术前
Preop 术后1个月
1m postop 术后1年12ms postop
末次随访
Last follow-up
PLIF 组PLIF group 115.4±8.9111.6±12.3106.3±11.291.6±11.1①②95.4±7.794.6±9.693.0±7.488.1±12.6Wallis 组Wallis group
注:①与同组术前相比,P <0.05;②与Wallis 组末次随访相比P <0.05
Note:①:compared with preoperative data at the same group,P <0.05;②compared with the Wallis group,P <0.05
112.4±10.0
109.9±9.2
107.1±10.4
103.5±10.8
96.3±9.2
95.4±8.5
93.9±9.7
91.3±11.4
表2
两组患者术前基本资料
Table 2Preoperative data of the patients between groups
年龄
Age (x ±s )
性别
Gender UCLA 标准分级UCLA grading
L3/4L5/S1
男
Male
女
Female
ⅠⅡⅠⅡWallis 组(Wallis group )50.3±8.015141712227PLIF 组(PLIF group )
52.6±10.61715
18
14
23
9
P 值
0.96
0.88
0.79
0.82
诊断
Diagnosis 131616
16
0.91
LDH LSS 2.1影像学评价
为明确内置物对T1ρ-MRI 扫描序列是否产
生影响,比较两组患者术前与术后1个月固定相邻节段L3/4、L5/S1椎间盘T1ρ值,均无统计学差异(PLIF 组L3/4:F=4.33,P >0.05;L5/S1:F=4.16,
P >0.05;Wallis 组L3/4:F=1.12,P >0.05;L5/S1:F=3.97,P >0.05,表3)。
两组患者固定节段均无内固定松脱、椎间失稳、假关节形成等并发症发生;两组上位相邻节段
L3/4椎间盘T1ρ值均存在下降趋势,但Wallis 组末次随访与术前差异无统计学意义(P >0.05),而PLIF 组L3/4节段则较术前相比明显下降,差异
有统计学意义(P <0.05);两组下位相邻节段L5/S1椎间盘T1ρ值同样存在下降趋势,但末次随访与术前差异均无统计学意义(P >0.05)。
两组间比较,术后1年L3/4、L5/S1节段椎间盘T1ρ值均无统计学差异(P >0.05);末次随访,
PLIF 组L3/4椎间盘T1ρ值显著低于Wallis 组,差异有统计学意义(P <0.05);PLIF 组L5/S1节段椎间盘T1ρ值同样低于Wallis 组,但差异无统计学意义P >0.05,表3)。
末次随访时,按UCLA 标准分级(图1、2),
PLIF 组L3/4节段退变Ⅰ级、Ⅱ级、Ⅲ级和Ⅳ级分别为6、13、10、3例,Wallis 组分别为4、11、12、2
例,差异无统计学意义(z=1.75,P =0.91)。PLIF 组
L5/S1节段退变Ⅰ级、Ⅱ级和Ⅲ级分别为16、9、4例,Wallis 组分别为18、11、3例,差异亦无统计学意义(z=2.03,P >0.05)。2.2临床评价
术后两组患者均无神经功能障碍加重表现,末次随访,两组患者ODI 及JOA 评分均较术前获得明显改善(表4);PLIF 组与Wallis 组ODI 平均改善率分别为76.1%、78.5%,JOA 评分平均改善率分别为69.2%、75.0%,两组间差异均无统计学意义(ODI :χ2=6.63,P >0.05;JOA :χ2=5.48,P >0.05)。
3讨论
尽管腰椎融合术为很多患者解除了痛苦,但
同时也带来了一些问题,融合术后ASP 便是其中之一[2~5]。当某一节段脊柱被融合后,其上下两端就会产生代偿性应力集中,增加该部分的分离倾向和不稳定,导致这些节段的退变加速。影像学上表现为椎间盘变性或突出、椎间隙狭窄、椎体或小关节骨质增生、节段性失稳或滑脱,严重者可出现椎管狭窄[13]。
随着对ASP 认识的深入,改变腰椎内固定生物力学环境的动态稳定系统的应用近年来逐渐增多。目的均是使椎间盘及椎间关节应力减小,同时
图1患者男,56岁,L4/5单节段椎管狭窄伴椎间失稳a 、b 术前动力位X 线片显示L4/5节段退变性失稳并轻度滑移(<
Ⅰ度),L3/4以及L5/S1节段按UCLA 分级分别为Ⅲ级和Ⅱ级c 、d 术前MRI 检查显示L4/5节段黄韧带肥厚致椎管狭窄e 术前T1ρ序列检测L3/4、L5/S1T1ρ值分别为117.3ms 、99.5ms f 、g 行椎弓根螺钉固定并椎体间融合术后4年,内固定
位置良好,L4/5椎间融合效果满意,但上位相邻L3/4节段出现终板硬化,椎前出现骨赘,按UCLA 分级为Ⅳ级,下位L5/S1节段仍为Ⅱ级h 、i 术后4年复查MRI 显示椎管减压效果满意,邻近L3/4节段椎间盘信号强度降低j 术后4年随访T1ρ序列检测L3/4、L5/S1T1ρ值分别为94.7ms 、90.4ms
Figure 1Male,56years old,L4/5degenerative instability and stenosis a,b Preoperative lateral X-rays showed L4/5
degenerative instability(less than Ⅰ°spondylolisthesis).The segments L3/4and L5/S1was graded Ⅰand Ⅱrespectively according to UCLA grading system c,
d Preoperativ
e MRI showed that lumbar stenosis at L4/5due to hypertrophy of
ligamentumflavum e The T1ρvalues in L3/4and L5/S1discs preoperatively was 117.3ms and 99.5ms,respectively f,g Postoperative lateral X-rays showed good position of internal fixation and complete fusion at L4/5segment 4years after pedicle screw fixation and interbody fusion,however,there were endplate sclerosis and osteophytes at the adjacent L3/4segment,which was classified as grade Ⅳaccording to UCLA grading system,
and the segment L5/S1remained grade
Ⅱh,
i Postoperative MRI showed good decompression effects of spinal canal at L4/54years after operation and the
signal intensity of intervertebral disc at adjacent segment decreased compared with that before operation j The T1ρvalues in L3/4and L5/S1disc 4years after operation was 94.7ms and 90.4ms,respectively
又能限制脊柱部分活动。其中,棘突间撑开装置Wallis 动态固定系统因其操作简单、创伤较小,应
用逐渐增多,并取得满意临床效果[14、15]。但关于棘突间动态固定系统是否会减少相邻节段退变仍存在一定争议。Korovessis 等[14]应用Wallis 固定系统治疗24例腰椎退变性失稳患者,发现其与椎弓根
螺钉固定融合术相比可以显著减少相邻节段退变的发生。Schmoelz 等[16]通过体外实验对棘突间动态固定系统进行研究发现,其在腰椎退变中可以有效维持椎体稳定性,且对相邻节段椎间盘退变的影响较小。Kumar 等[10]分析32例患者2年随访结果,认为经棘突间动态固定后相邻节段椎间盘
1b 1c 1a 1d 1e
1f 1i 1g 1j
1h
图2患者女,50岁,L4/5单节段椎管狭窄伴有椎间失稳a 、b 术前动力位X 线片显示L4/5节段退变性失稳,L3/4以及
L5/S1节段按UCLA 分级均为Ⅰ级c 、d 术前MRI 检查显示L4/5节段黄韧带肥厚致椎管狭窄e 术前T1ρ序列检测L3/4、L5/S1T1ρ值分别为109.8ms 、101.1ms f 、g 棘突间Wallis 内固定术后2年MRI 示椎管减压效果满意,邻近节段椎间
盘信号强度较术前稍改善h 、i 术后4年,内固定位置良好,L4/5节段稳定效果满意,相邻L3/4和L5/S1节段未见明显终板硬化及骨赘形成等退变表现,按UCLA 分级均为Ⅰ级j 术后4年随访T1ρ序列检测L3/4、L5/S1T1ρ值分别为
104.1ms 、94.2ms Figure 2
Female,50years old,L4/5degenerative instability and stenosis a,b Preoperative lateral X-rays showed L4/5
degenerative instability,
and both L/34and L5/S1were graded Ⅰaccording to UCLA grading system c,
d Preoperative
MRI showed that lumbar stenosis at L4/5due to hypertrophy of ligamentumflavume e The T1ρvalues in L3/4and L5/S1discs preoperatively was 109.8ms and 101.1ms,respectively f,g Postoperative MRI showed good decompression effects of spinal canal at L4/5two years after operation,and the signal intensity of adjacent segment disc improved compared with that before operation h,i Postoperative lateral X-rays showed good position of internal fixation and stable effects at L4/5four yearsafter wallis internal fixation.
There were no endplate sclerosis and osteophytes at the adjacent L3/4and L5/S1
segment,which was classified as grade Ⅰaccording to UCLA grading system j The T1ρvalues in L3/4and L5/S1disc 4years after operation was 104.1ms and 94.2ms,respectively
表4两组患者术前、术后及末次随访临床功能评分比较(x ±s )
Table 4The clinical results between groups
ODI 评分(ODI Score)
JOA 评分(JOA Score)术前
Preop
术后1个月
1m postop
术后1年
12ms postop 末次随访
Last follow-up
术前
Preop 术后1个月
1m postop
术后1年
12ms postop 末次随访
Last follow-up
Wallis 组Wallis 36.8±8.111.3±7.6①8.6±6.4①7.9±5.1①12.6±3.314.7±6.6①15.4±5.7①15.9±4.6①PLIF 组PLIF group
35.7±10.1
13.82±8.6①
8.9±5.3①
8.5±6.0①
13.1±3.4
14.4±7.8①
15.1±7.1①
15.8±5.4①
注:①与同组术前相比较,P <0.05
Note:①Compare with preoperative values in the same group,P <0.05
2a 2b 2c 2d 2e
2f 2h 2i 2j
2g
仍继续退变,这种退变可能是疾病本身的发展过程,而不是内固定引起的结果,但以上结果大多停留在影像学宏观改变上,尚无研究从椎间盘髓核蛋白多糖含量变化进行探讨比较。
为进一步明确上述问题,本研究采用体内无创性影像学检测T1ρ-MRI技术探测固定相邻节段椎间盘髓核蛋白多糖含量的变化。研究表明引起椎间盘变性的早期病理因素是髓核蛋白多糖(proteoglycans,PGs)的丧失[17]。PGs是保持椎间盘富有弹性和抗压特性的重要软骨基质,而PGs丢失又是椎间盘退变的最早变化之一。T1ρ-MRI技术可用来量化测定软骨中的PGs,是一种描述水分子在髓核基质大分子中缓慢运动及其交互作用敏感可行的方法[18、19]。Zuo等[20]采用MR波谱成像测量正常与退变椎间盘髓核内水及PGs含量,发现T1ρ值与水/PGs峰值比及PGs含量呈显著相关,其中与椎间盘PGs含量呈高度正相关,决定系数(R2)为0.61。Johannessen等[21]通过测定人类不同程度退变的椎间盘标本T1ρ值发现,随着椎间盘退变评分的增加,T1ρ值显著下降,两者呈高度负相关,相关系数为-0.761,同时发现T1ρ值与蛋白多糖含量湿重呈高度正相关,相关系数为0.70。然而,由于T1ρ是近年来新兴的扫描序列,虽然可以定量测定椎间盘蛋白多糖以及含水量,但至今尚无判断椎间盘退变的绝对标准,因此有关其特异性目前尚无研究报道。本研究结果发现,Wallis组上位相邻节段椎间盘T1ρ值末次随访虽然较术前下降,但并无显著性差异,而PLIF组则呈明显下降趋势(P<0.05)。由此可以推测,与PLIF术式相比,Wallis动态固定可以减缓其上位相邻节段椎间盘的退变进程。研究结果也验证了动态固定系统在限制该段异常活动并保证可控制范围内脊柱运动的情况下,通过改变运动节段负荷模式,从而降低固定术后相邻节段椎间盘退变发生率的假说。
尽管既往研究认为,在常规磁共振成像过程中,金属内固定材料的存在会造成图像质量下降并影响检测结果。由于回波时间(TE)是影响图像质量的关键因素,因此,我们在扫描中选择短TE,同时选择正中矢状位同样面积的髓核中心(0.75cm2)作为感兴趣区,最大限度减少感兴趣区域(ROI)面积,并采用增加带宽的方式扫描,结果显示,两组患者腰椎间盘T1ρ值在术前及术后1个月复查均无显著变化,提示金属内固定对MRI-T1ρ值测量未构成明显影响。因此,我们认为采用T1ρ-MRI技术评价椎体内固定状态下椎间盘退变程度是可行的。
另外,本研究同时通过X线影像学观察发现,两组患者末次随访相邻节段椎间盘退变分级无明显差异。这也一定程度侧面证明椎间盘T1ρ值变化在评价椎间盘退变方面较X线影像学表现变化更加敏感,可以为早期临床干预提供参考依据,更具有临床指导意义。
尽管融合后相邻节段出现退变的发生率较高,但有关其与临床效果之间的相关性仍存在争议[13]。Okuda等[22]对87例后路L4/5椎体间固定融合患者平均随访43个月,发现29%的患者显示上位相邻节段出现影像学退变,但临床功能恢复率与未退变组无明显差异。我们曾通过随访观察49例后路L4/5椎弓根螺钉固定并椎体间融合患者,上位相邻节段影像学退变率为22%,但退变组与非退变组末次随访时ODI与JOA评分改善率均无显著性差异[23]。本研究通过观察比较两组患者末次随访时临床功能评分发现,尽管PLIF组上位相邻节段椎间盘退变较Wallis组明显,但ODI以及JOA评分改善率无明显差异。与之前一些文献[5、23]报道的观点一致。文献报道腰椎固定术后相邻节段退变多发生在上位相邻节段[4]。本研究同时对固定节段上、下位相邻节段椎间盘退变进行观察评估,末次随访,发现两组患者下位相邻节段椎间盘退变分级均≤Ⅲ级(按UCLA标准),而两组上位相邻节段椎间盘分别有3例和2例进展为Ⅳ级,提示腰椎内固定术后对下位相邻节段椎间盘退变影响相对较小,与文献[5、23]报道结果一致。
本研究结果表明,与PLIF相比,Wallis动态固定可相对减缓相邻节段退变进程,但两者临床效果之间并无显著性差异。但由于条件限制,本研究未设立保守治疗组进行对照研究,因此无法得出上位相邻节段退变是由于固定导致还是自然退变结果所致的结论,且本研究随访期限仅为中期随访,结论尚需更远期的临床研究进一步证实。
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(收稿日期:2014-05-16末次修回日期:2014-09-03)
(英文编审蒋欣/贾丹彤)
(本文编辑李伟霞)