KumaFix fixation for thoracolumbar burst fractures: a prospective study on selective consecutive patientsAcknowledgments

Background Short-segment U-shaped pedicle screw fixation has been widely used to treat thoracolumbar burst fracture. Some studies reported the disadvantages of traditional U-shaped pedicle screw, which included a relatively high rate of adjacent segment degeneration and screw failure including screw pullout and breakage. The purpose of this study was to assess efficacy of open reduction and fixation using KumaFix fixation system in treatment of thoracolumbar burst fractures.     

伴有脊髓神经损伤的脊柱胸腰段爆裂骨折的后路经椎弓根内固定术

目的探讨伴有不全性脊髓神经损伤的脊柱胸腰段爆裂骨折的后路经椎弓根短节段固定、融合术的治疗效果。方法对36例伴有不全性脊髓神经损伤的脊柱胸腰段爆裂骨折患者行后路经椎弓根撑开复位、短节段内固定及后路植骨融合术,通过观察术后症状的改善及骨折复位情况来评估其疗效。结果所有患者随访获得10个月~4年(平均3年)的随访,所有患者椎体高度基本恢复正常,生理屈度矫正,脊髓神经损伤的恢复按Frankel评级均有1~3级的提高。结论经后路椎弓根撑开复位、短节段内固定及后路植骨融合术可以有效的治疗大多数伴有不全性脊髓神经损伤的脊柱胸腰段爆裂骨折。     

前路减压、植骨及内固定治疗胸腰椎爆裂骨折

目的探讨胸腰椎爆裂骨折前路减压固定的可能性。方法2001年5月￣2005年1月,收治32例胸腰段骨折合并脊髓损伤患者。其中T1212例,L117例,L23例。按Franke1分级评定:A级6例,B级5例,C级7例,D级14例。手术均行前路减压内固定术。结果32例术后影像学检查胸腰椎生理弧度基本恢复正常。均获随访10～51个月,平均17.9个月。神经功能除2例脊髓完全损伤无恢复外,其余均有不同程度改善。未出现钢板螺钉松动断裂、继发性脊柱后突及节段性不稳等并发症。结论前路减压内固定修复重建严重胸腰椎爆裂骨折,具有减压彻底、植骨充分及内固定牢固等特点,有助于椎体高度恢复和神经功能改善。     

椎弓根钉系统固定结合经椎弓根自体骨移植治疗胸腰椎爆裂性骨折疗效分析

目的椎弓根钉系统固定结合经椎弓根自体骨移植治疗胸腰椎爆裂性骨折的疗效分析。方法选择35例胸腰椎爆裂性骨折病例,采用椎弓根钉系统固定结合经椎弓根自体骨移植治疗,术后卧床2～3周后,在支具保护下可下地活动,3～4个月后去支具活动,骨折愈合后取出内固定,随访30个月。结果术后3d及至随访结束时,伤椎前、后缘与正常的高度比与术前相比,差异有统计学意义(P<0.01),术后3d与随访结束时比较,差异无统计学意义;术后3d及随访结束时Cobb后凸角的矫正效果比较,差异有统计学意义(P<0.01)。结论椎弓根钉系统固定可在骨折早期起支撑及固定作用,脊柱的长期稳定有赖于椎体自身的生物力学稳定的建立;对胸腰椎爆裂性骨折患者进行植骨选择伤椎椎弓根椎体内植骨,可达到恢复正常脊柱序列和重建脊柱稳定性的目的。     

后路短节段椎弓根螺钉固定治疗胸腰椎骨折

目的:探讨椎弓根螺钉短节段固定治疗胸腰椎爆裂型骨折的临床疗效。方法:回顾性分析50例胸腰椎爆裂型骨折患者行后路椎弓根螺钉复位固定的临床资料。结果:所有患者均获随访,随访时间8个月～5年,中位时间2年6个月。本组患者脊柱后凸畸形明显得到纠正,椎体前后缘高度基本恢复正常,术后CT扫描显示减压满意,Frankel分级A、E级病例无神经功能改变,其余病例Frankel分级均有1～2个等级以上改善。结论:椎弓根螺钉短节段固定是治疗胸腰椎爆裂型骨折的有效方法。     

经伤椎椎弓根置钉固定治疗胸腰椎骨折疗效观察

目的探讨经伤椎置钉椎弓根螺钉系统固定治疗胸腰椎骨折的临床疗效。方法对42例胸腰椎骨折患者施行经伤椎置钉椎弓根螺钉系统固定治疗,手术前后行X线片和计算机体层摄影检查,测量伤椎椎体前缘高度和伤椎矢状面指数(SI),评定治疗效果。结果手术时间90～180 min,平均(120.0±9.6)min,出血量200～2 400 mL,平均(600.0±16.5)mL。患者术后1周及3、6、12个月SI显著小于术前(P<0.05),患者术后1周及3、6、12个月时SI比较差异均无统计学意义(P>0.05)。患者术后1周及3、6、12个月椎体前缘高度显著大于术前(P<0.05);患者术后1周及3、6、12个月时椎体前缘高度比较差异均无统计学意义(P>0.05)。所有患者随访6个月时骨折均完全愈合,随访期间未出现内固定松动、拔钉、钉棒折断等。11例术前下肢神经功能Frankel分级为C、D级患者术后康复,随访3个月,Frankel分级达到E级。结论经伤椎置入椎弓根螺钉的6钉固定方法治疗胸腰椎骨折,椎体高度恢复效果良好,术后伤椎高度丢失减少,内固定牢固,有利于伤椎的融合和神经功能的恢复。     

短节段椎弓根螺钉内固定治疗单节段胸腰段爆裂骨折的远期疗效分析

目的:分析短节段跨伤椎椎弓根螺钉内固定治疗单节段脊柱胸腰段爆裂性骨折的远期临床效果。方法:采用短节段(四钉两棒)椎弓根螺钉内固定系统治疗单节段胸腰段爆裂性骨折46例。术后12个月常规拔除内固定,术后随访18~36个月。结果:术后即刻椎体高度较术前显著增长(P<0.01),后凸畸形较术前明显改善(P<0.01),螺钉位置及稳定性良好,未出现脊髓神经症状加重。随访过程中,6例出现内固定断裂,末次随访时椎体高度较术后即刻减少(P<0.01),末次随访时后凸角较术后即刻增大(P<0.01)。Denis疼痛工作评分,P1W1:9例(25%),P2W2:26例,P3W2:7例,P3W3:4例。结论:短节段跨伤椎椎弓根螺钉内固定治疗单节段胸腰椎爆裂性骨折并发症较多,远期效果难以维持,临床应用应谨慎。     

经皮穿刺与传统开放椎弓根螺钉内固定术治疗胸腰椎骨折的 Meta 分析

目的：比较经皮穿刺与传统开放椎弓根螺钉内固定技术治疗胸腰椎骨折的疗效及安全性。方法采用 Cochrane 系统评价方法,计算机检索 PUBMED、OVID 和 Cochrane CENTRAL 外文数据库,符合入选标准的文献由2名评价者独立筛选及评估,采用 RevMan5．2．6软件进行 Meta 分析。结果7篇文献（共353例患者）被纳入分析,结果显示经皮穿刺较传统开放椎弓根螺钉内固定技术治疗胸腰椎骨折术中失血量（RR＝1．89,95％CI ：1．55～2．29）和手术时间（RR＝1．21,95％CI ：1．12～1．30）比较,差异有统计学意义（P ＜0．05）,且经皮穿刺组矫正矢状后凸角、改善椎体前缘高度与传统开放组比较,差异无统计学意义（P ＞0．05）。结论经皮穿刺及传统开放椎弓根螺钉内固定技术都是安全有效的治疗胸腰椎骨折的内固定方法,但是经皮穿刺相对于传统开放椎弓根螺钉内固定技术创伤更小、失血更少、手术时间更短。     

经椎弓根植骨AF内固定治疗胸腰椎爆裂性骨折18例

目的探讨经椎弓根植骨AF内固定治疗胸腰椎爆裂性骨折的方法和效果。方法对18例胸腰椎爆裂性骨折的患者行经椎弓根植骨AF内固定术,术前、术后及随访时测量椎体高度、后凸角,了解神经功能改变及腰背疼痛变化。结果随访6～36个月,无断钉及内固定物松动,椎体高度和后凸角无明显再丢失,神经功能及腰背疼痛明显改善。结论经椎弓根植骨AF内固定治疗胸腰椎爆裂性骨折可重建脊柱前中柱的稳定性,防止后期矫正角度及椎体高度的再丢失。     

短节段非融合椎弓根螺钉固定治疗不稳定性胸腰椎爆裂骨折疗效观察

目的评价短节段非融合椎弓根螺钉固定治疗不稳定性胸腰椎爆裂骨折的临床效果。方法 19例不稳定性胸腰椎爆裂骨折患者均接受短节段非融合椎弓根螺钉固定治疗,分别于术前、术后12个月取出内固定物之前及取出内固定物后6个月对患者进行临床及影像学评估,观察椎管内占位情况、椎体高度、临床效果及并发症等。结果本组病例的平均手术时间为(93.4±18.3)min;平均术中失血量为(92.1±20.2)mL。术前、术后12个月取出内固定物之前及取出内固定物后6个月患者椎管内占位率分别为(55.4±3.8)%、(35.6±4.1)%、(35.4±3.9)%;术后12个月内固定物取出前及内固定物取出后6个月时患者椎管内占位率显著高于术前,差异有统计学意义(P<0.05);但术后12个月内固定物取出前与内固定物取出后6个月时患者椎管内占位率比较,差异无统计学意义(P>0.05)。术前、术后12个月取出内固定物之前及取出内固定物后6个月患者伤椎椎体高度丢失率分别为(45.3±3.4)%、(16.9±2.9)%、(18.1±3.1)%;术后12个月内固定物取出前及内固定物取出后6个月时患者伤椎椎体高度丢失率显著低于术前,差异有统计学意义(P<0.05);但术后12个月内固定物取出前与内固定物取出后6个月时患者伤椎椎体高度丢失率比较,差异无统计学意义(P>0.05)。术前、术后12个月取出内固定物之前及取出内固定物后6个月患者VAS疼痛评分分别为8.2±1.8、2.2±1.3、2.1±1.1;术后12个月内固定物取出前及内固定物取出后6个月时患者视觉模拟量表(VAS)疼痛评分显著低于术前,差异有统计学意义(P<0.05);但术后12个月内固定物取出前与内固定物取出后6个月时患者VAS疼痛评分比较,差异无统计学意义(P>0.05)。按Macnab评价标准,19例患者中,优15例,良3例,可1例,优良率为94.7%。结论短节段非融合椎弓根螺钉固定治疗无神经损伤症状的不稳定性胸腰椎爆裂骨折年轻患者安全、有效,且内固定物取出后伤椎的椎体高度及受累节段的椎体容积改善水平能够继续保持。     

经皮微创和传统开放椎弓根钉棒内固定术治疗胸腰椎骨折疗效比较

目的:探讨经皮微创椎弓根钉棒内固定术治疗胸腰椎骨折的疗效.方法:胸腰椎骨折病人98例,根据手术方法分为观察组与对照组,其中对照组52例,应用传统开放椎弓根钉棒内固定术治疗,观察组46例,应用经皮微创椎弓根钉棒内固定术治疗.对比分析2组病人的术后疗效.结果:观察组手术时间、切口长度、术中出血量、术后引流量及术后1d疼痛视觉模拟评分均明显低于对照组(P<0.01),而2组病人伤椎前缘高度百分比和术前、术后1周及术后1年矢状面后凸Cobb角和Oswestry功能障碍指数差异均无统计学意义(P>0.05).结论:经皮微创椎弓根钉棒内固定术治疗胸腰椎骨折病人术后疗效肯定,具有创伤小、术后恢复快、疼痛轻等优势,值得临床进一步推广应用.     

前路手术治疗胸腰椎爆裂骨折临床分析

目的：探讨前路手术治疗胸腰椎爆裂骨折的临床效果.方法：应用前路减压、植骨、内固定治疗胸腰椎爆裂骨折35例,分析神经功能恢复和并发症.结果：本组病例植骨愈合时间3～4个月,平均3.2个月,神经功能有一定程度的恢复.术后发生气胸1例,经治疗后治愈.结论：胸腰椎爆裂骨折并不全瘫患者行前路手术有很好的治疗效果.     

短节段椎弓根内固定治疗胸腰椎爆裂性骨折51例临床分析

目的：：探讨短节段椎弓根内固定治疗胸腰椎严重爆裂骨折的临床疗效。方法：选择自2008年2月~2013年1月于我院行短节段椎弓根内固定治疗胸腰椎爆裂骨折的患者51例,随访分析其临床疗效。结果：本研究中患者手术均取得成功,术后切口愈合良好,并且患者的神经症状有所缓解。随访后动力位X线片显示固定段无异常活动,椎体高度较术后平均改变0.5%,同时未发现椎弓钉松动、断裂。结论：短节段椎弓根内固定治疗是治疗胸腰椎严重爆裂性骨折的有效方法,是集减压、复位、内固定于一体的手术方式,但手术造成的创伤大,因此应合理把握手术指征。     

后路单节段伤椎固定治疗脊柱胸腰段不完全爆裂骨折的疗效评价

目的：探讨后路单节段伤椎固定治疗脊柱胸腰段不完全爆裂骨折的疗效。方法：选择我院2006年6月～2010年3月收治的脊柱胸腰段不完全爆裂骨折患者40例,其中,给予20例患者单节段固定治疗（观察组）,20例患者采用短节段固定治疗（对照组）。比较两组手术情况及术后视觉模拟评分（vAs）、伤椎后凸角情况。结果：两组术后1周、术后1年伤椎角度、视觉模拟评分均较治疗前明显改善,前后比较,差异有统计学意义（P〈0．05）;丽组手术时间、术中出血量、术后1周及1年伤椎后凸角度及视觉模拟评分比较,差异无统计学意义（P〉0．05）。结论：后路单节段伤椎固定治疗脊柱胸腰段不完全爆裂骨折与短节段固定治疗效果元明显差异,近期疗效较好,值得临床应用。     

后路手术治疗胸腰段椎体骨折49例

目的:总结应用后路钉棒系统内固定治疗胸腰段椎体骨折的临床效果。方法:回顾性分析后路椎弓根钉棒系统治疗胸腰段椎体骨折49例,观察脊柱功能改善,椎体前后缘高度变化,cobb角的矫正程度及并发症发生情况。结果:随访6-34个月,椎体平均高度由术前的前缘37.4%和后缘的81.2%恢复到术后的前缘95.7%和后缘97.2%,cobb角由术前平均28.3°恢复为术后平均4.7°。脊髓神经功能明显改善。按Frankel分级除A级3例无改善外,其余均有1-3级的神经功能恢复。结论:后路钉棒系统具有手术相对简单,操作方便,固定可靠等优点,是胸腰段椎体骨折的有效治疗方法之一。     

强直性脊柱炎伴胸腰段骨折患者应用后路长节段经皮置钉内固定术治疗的临床效果观察

目的 观察强直性脊柱炎(AS)伴胸腰段骨折患者应用后路长节段经皮置钉内固定术治疗的临床效果观察.方法 回顾性分析2017年6月至2018年12月于郑州大学医院接受后路长节段常规切开内固定治疗(对照组,n=65例)及接受后路长节段经皮置钉内固定术治疗(研究组,n=54例)的AS伴胸腰段骨折患者的临床资料.比较两组患者术中...     

Biomechanical effects of pedicle screw adjustments on the thoracolumbar burst fractures

Background Posterior pedicle screw device is widely used in treatment of thoracolumbar burst fractures.As the clinical operation is not based upon quantitative data of adjustments,the results are not o...     

前后入路减压内固定治疗胸腰椎爆裂骨折合并脊髓损伤的疗效比较

目的：比较前、后入路减压内固定治疗胸腰椎爆裂骨折合并脊髓损伤的临床疗效。方法：以我院2012年1月～2014年7月收治的64例胸腰椎爆裂骨折合并脊髓损伤患者为研究对象,根据不同入路方式将其分为前入路组与后入路组,比较两组手术相关指标、手术前后后凸Cobb角、伤椎高度及Frankel分级情况。结果：两组手术时间、术中出血量及住院时间比较差异无统计学意义。前入路组植骨融合时间、随访12个月后凸Cobb角分别为（3.5±1.2）月、（4.7±2.0）°,均明显低于后入路组的（4.9±1.2）月、（7.1±2.3）°。两组随访12个月Frankel分级较术前明显改善,但两组间比较差异无统计学意义。结论：前入路、后入路减压内固定治疗胸腰椎爆裂合并脊髓损伤疗效均较好,前者植骨融合时间明显更短,后凸Cobb角丢失相对少,临床需根据适应证选择合适术式。     

The biomechanical effects of pedicle screw adjustments on the thoracolumbar burst fractures

The biomechanical effects of pedicle screw adjustments on the thoracolumbar burst fractures Shang jian, Ling xiaodong, Han xiguang, et al The First Affiliated Hospital Of Harbin Medical University Background: Posterior pedicle screw device is widely to apply treatment of thoracolumbar burst fractures. As the clinical operation is not based upon quantitative data of adjustments, the results are not optimal. At present, no study has assessed the associations between the device adjustments and the restoration of stiffness. Objectives: To investigate the biomechanical effects that adjustments of a pedicle screw device have on the burst fracture, and explore an optimal adjustment. Methods: Burst fractures were produced at L1 vertebra in twenty-four fresh calf spines (T12-L3). The specimens divided into four groups at random. Pedicle screw devices were attached to T13 and L2. Four device adjustments, consisting of distraction and extension, were applied. Adjustment 1 was pure 6° extension. Adjustment 2 was pure 5mm distraction. Adjustment 3 was 6° extension followed by 5mm distraction. Adjustment 4 was 5mm distraction followed by 6° extension. Analysis and evaluate the effect of each adjustment on the stiffness restoration, anatomical reduction and neural decompression for the burst fractures. Results: Pure extension (group 1) produced the closest segment height and the least restoration of the canal to the intact. Pure distraction (group 2) restored stiffness most, but only with 60% stiffness of the intact value, and lost the segmental angle most to the intact. The combination of extension-distraction (group 3 and group 4) produced the maximum reduction of the anatomy and restoration of the canal in the burst fracture, and the least stiffness restoration. The sequence of extension and distraction did not affect stiffness restoration, anatomical reduction and neural decompression. Conclusions: The device adjustments affected stiffness restoration, anatomical reduction and neural decompression. The combined extension-distraction adjustment may be the most suitable considering the anatomical reduction and neural decompression, but its stiffness decreased the most, if necessary; it should be considered to reconstruct L1 vertebral. Key words: Burst fracture, Pedicle screw, Stiffness, Adjustment 1. Introduction Nearly 90% of all spinal fractures occur in the thoracolumbar region, and burst fractures compose approximately 15% of such injuries. Burst fractures occur predominantly in the younger patients, incurring a high financial and society cost [1]. There have been many reports suggesting appropriate therapies for burst fracture. Surgery is still controversial, but is gradually being accepted. The ideal goal of the surgical treatment of burst fracture is neural decompression and anatomical reduction and ambulation as early as possible. Generally, surgical treatment is generally divided into two types: anterior and posterior. The anterior approach provides good decompression and solid fusion, but the operative risks relatively higher than that associated with the posterior approach. On the other hand, the posterior procedure of the thoracolumbar junction is well established, with advantages such as more safety and less being technically demanding. There are many surgical devices for the posterior approach. Nowadays, use of pedicle screw has become increasingly popular. Theoretically, pedicle screw fixation provides greater forces to be applied to the spine to reduce deformity because of its 3-column fixation characteristics. Short-segment fixation is the most common and most simple treatment of burst fractures. The need to fuse fewer segments is treated with short-segment fixation in comparison with longer-segment fixation [2]. Pedicle devices are used not only to provide temporary fixation, but also to restore the vertebral spinal alignment and to reduce the canal encroachment. The stabilizing potential of the pedicle screw device adjustments has been rarely studied. As the operation procedure is not based upon quantitative data, the results obtained are not optimal. A fracture vertebra does not transfer load as effectively as the intact vertebra [3]. Patients who undergo surgery using short-segment pedicle screw instrumentation for middle-column injury may experience implant failure. The compressive stiffness of the spine reflects the load-sharing between the implant and the injured spinal column. To our knowledge there are no experimental studies that have has assessed the associations between the device adjustments and the restoration of stiffness. We hypothesized that the pedicle screw adjustments affected the restoration of segment stiffness. The purpose of the current study was to investigate the effects that adjustments of a pedicle screw device had on the reduction of the burst fracture, including anatomical reduction, neural decompression, and especially stiffness restorations, then to explore an optimal adjustment. 2. Materials and methods 2.1. Specimen Preparation Twenty four thoracolumbar spinal specimens from twenty-one-day-old fresh calves were retrieved from an abattoir and frozen at −20 °C. There was no trauma history associated with any of these specimens. Of the specimens, ten were female and fourteen were male with an average age of 6.8 days (range, 5-9 days). After defrosting for twenty-four hours, the specimens were cut into five-vertebra segments (T11-L3), excess paravertebral muscle was removed. The ends of the specimen were set in 80-mm-diameter polymethylmethacrylate end plates to produce flat, parallel surfaces. The instrument used spinal internal fixation system (Beijing Orthopedic Innovation, Inc, China), the screw length and diameter were 5.0 mm and 35 mm respectively. 2.2 Experimental Burst Fracture Production Experimental burst fractures were produced at the L1 vertebra using an incremental impact protocol [4]. An impact mass, guided by a vertical tube, was dropped onto an impounder resting on top of the specimen. The average drop height was 1.4 m, resulting in an impact speed of 5.2 m/sec. A wedge of 8 ° wedge angle was placed between the impounder and the specimen top to force the latter into a flexed posture, so that the mechanism of loading was flexion-compression. Each specimen was impacted with an initial mass of 3.3 kg. If no burst fracture occurred, the mass was increased by 2.0 kg for the next impact. The burst fracture occurrence was monitored by measuring the canal encroachment on lateral radiograph taken after each impact. This incremental addition was continued until a burst fracture of requisite severity (10-80% encroachment,) occurred. 2.3 Pedicle Screw Device After burst fracture, two pairs of pedicle screws were inserted into the T12 and L2 pedicle using the standard clinical technique. In T13 the screws were inserted approximately 30-32 mm in depth and in L2 to a 35-mm depth. To avoid loosening of the interface between the specimen and the screw during repeated loads, polyester resin was poured. An internal fixator rod system was attached to left and right pairs of the screws. This pedicle screw system allowed us to independently apply two device adjustments (translation or angulation) in the positive or negative direction, or a combination. 2.4 Device Adjustments The specimens divided into four groups at random. Four device adjustments were chosen with combinations of translation and angulation. The choice was governed by 1) clinical relevance, 2) no injury to the specimen due to the result of any adjustment, 4) the decreased segmental height and angle of the burst fracture, and 3) only a finite number of adjustments could be studied. Burst fractures are caused by flexi- and -axial loading forces and thus seem best treated posteriorly with reduction and fixation by extension and distraction. Clinically, the burst fracture is often put in some extension to restore spinal lordosis and some distraction to restore spinal height, but seldom in flexion or distraction. We chose four device adjustments which were studied. (Table 1) The four device adjustments, from left to right, respectively, consist of 6° pure extension (0/6°E), 5 mm pure distraction (5D/0°), 6° extension was followed by 5 mm distraction (5D/6°E) and 5 mm distraction was followed by 6° extension(5D/6°E). Table 1 Four device adjustments Adjustments After Burst Fracture 1 2 3 4 Distraction（mm） 0 5 5 5 Extension（°） -6 0 -6 -6 Group 1, 2 were single adjustments, whereas group 3, 4 were combinations. 2.5 Biomechanical test and CT scan All specimens were subjected to five cycles of 0-250 N flexion-and axial-compression in a displacement-controlled mode at a rate of 25 mm/min on a testing machine (Instron 5569, China). Two load cycles were used to precondition the specimen. At each step on each load cycle, the specimen was allowed to creep for 30 seconds to reduce variations resulting from viscoelasticity of the spine. Load-displacement curves were automatically recorded. The axial-compression and flexion-compression curves were computed in the three conditions: intact, burst fracture, and burst fracture with each of the four device adjustments. The stiffness (N/mm) was defined as the linear slope of the curve (Fig. 1). Fig. 1 Diagrams of biomechanical setup (a: Axial compression. b: Flexion compression) All specimens in the three conditions, intact, burst fracture, and burst fracture with each of the four device adjustments, was taken for CT scanning and 3D reconstruction. (Fig. 2) Then according to the images, the segment height and angle (Fig 3), as well as the diameter of the L1 canal were measured. We defined this as the intact neutral posture, under no load. Therefore, height, angle and diameter were measured with the intact specimen in neutral posture. Fig.2 CT scanning (A2-C2) and 3D reconstruction (A1-C1) of a specimen in three conditions, intact, fracture, and fracture with the device adjustment Fig. 3 Definition of the segment height and angle (Line a is tangent to the lower endplate of T13. Line b is parallel to line and passes through the posterior-inferior corner of the L2 vertebral body. Line c is tangent to the lower endplate of T13) 2.6 testing protocol Three spinal conditions, intact, burst fracture, and burst fracture with each of the four device adjustments, were studied. A flow chart depicting testing sequence is provided in Fig. 4 Fig. 4 Experimental protocol showing the sequence of events for each specimen (CT & 3D: CT scanning and 3D reconstruction. AFCT: axial and flexion compression testing) 2.7 Statistical analysis Statistical analysis was performed using SPSS 10.0 software (SPSS/PC Ins, Chicago, IL, USA). Mean and standard deviations were computed of the segmental heights and angles, the diameter of the canal and the stiffness under axial- and flexion-compression. The differences among the four device adjustments were analyzed by one-factor analysis of variance. The differences within the same group were evaluated with t-tests. Significance was set at P<0.05. 3. Results Specimens experienced 3.4 times impact on average and the impact energy and speed on average by 94.2 J and 5.24 m/s respectively, then the L1 vertebral body produced burst fractures. The average intact axial-compression and flexion-compression stiffness were 380.7±58.5 N/mm and 339.2±42.1 N/mm respectively. After burst fractures, axial-compression and flexion-compression stiffness were 109.8±33.8 N/mm and 72.9±20.0 N/mm respectively. Both axial- and flexion-compression stiffness decreased significantly after injury as compared with intact spine (axial t=18.8, p<0.01; flexion t=16.6, p<0.01). We found the device adjustment to affect the burst fracture axial- and flexion-compression stiffness, but no adjustment provided stability close to the intact specimen (axial p<0.05; flexion p<0.05). Among the four device adjustments, 5 mm pure distraction (5D/0°) stabilized the most (axial p<0.05; flexion p<0.05), with a 28% and 35% relative decreasing of axial- and flexion-compression stiffness. The combined distraction-extension adjustments (5D/6°) stabilized the least (axial p<0.05; flexion p<0.05), and the sequence of applying distraction and extension did not affect the spinal stability (axial p>0.05; flexion p>0.05). Stiffness under flexion-compression was significantly lower than that under axial-compression in every state (p < 0.05). Table 2 Axial- and flexion-compression stiffness for intact, burst fracture and four device adjustments ( ±S, n=6). Intact Burst Fracture Adjustment After Burst Fracture 1 2 3 4 Axial-compression Stiffness(N/mm) 380.7±58.5 109.8±33.8 213.1±43.6 275.1±37.7 183.8±27.6 179.3±22.1 Flexion-compression Stiffness( (N/mm) 339.2±42.1 72.9±20.0 176.8±34.7 220.3±26.5 140.8±21.0 136.5±19.2 Fig. 5 Axial and flexion compression stiffness of each construct. The burst fracture decreased the segmental height on average by5.3±2.5 mm, and the segmental angle changed to kyphosis by 5.9±4.5°. The adjustments, with respect to the burst fracture, caused varying changes in the spinal posture. The combined distraction-extension adjustments (5D/6°) brought the burst fracture closer to the intact state than other adjustments (p>0.05). The postural changes due to group 3 versus 4 were not significantly different (p>0.05). Thus, the sequence of applying distraction and extension did not affect the spinal postural change. Pure adjustment caused spinal changes in spinal posture. For example, 5 mm pure distraction was accompanied by some kyphosis (height t=3.51, p<0.05; angle t=2.90, p<0.05), and 6° pure extension also produced some distraction (height t=2.97, p<0.05; angle t=3.54, p<0.05). Compared with the intact spine, pure distraction produced the segmental angle that deviated from the intact mostly (p<0.05); while pure extension produced the segmental height deviated from the intact mostly (p<0.05). Table 3 Changes in segmental height and segmental angle, from the burst fracture to the resulting postures due to the device adjustments ( ±S, n=6). Device adjustment 1 2 3 4 Segment height(mm) 1.9±0.8 2.9±1.8 6.0±1.3 5.8±1.4 Segment angle(°) -4.5±1.7 0.5±1.1 -3.8±1.9 -4.0±2.0 Fig. 6 Average changes in the posture from the burst fracture due to the four adjustments. On average, adjustment 2, 3, and 4 restored the canal diameter to approximately 70% of its intact value, but none restored to its intact values (Group 1: t=7.32, p<0.05; Group 2: t=4.92, p<0.05; Group3 t=3.39, p<0.05; Group 4: t=3.29, p<0.05). The combined distraction-extension adjustments (5D/6°) were found to produce the maximum restorations of canal diameter (p<0.05). The restorations due to group 3 versus 4 were not significantly different (p>0.05). Thus, the sequence of applying distraction and extension did not affect to decompress the canal (p<0.05). Table 4 Canal diameters for intact, burst fracture, and four device adjustment ( ±S, n=6). Intact Burst Fracture Adjustment After Burst Fracture 1 2 3 4 Canal diameter(mm) 14.2±1.1 8.3±2.0 9.7±2.1 10.1±2.7 11.1±2.2 11.3±1.9 Fig. 7 Restorations. The parameters indicate the magnitudes of restoration achieved as percentage of the intact values. Restoration (%) = 100 × DAdj/DIntact. DIntact: Intact canal diameter. DAdj: the canal diameter resulting from an adjustment. 4. Discussion Pedicle screw devices are versatile and used not only to provide fixation for an unstable spine, but also to reduce the canal encroachments and to restore the vertebral spinal alignment. These reductions and restorations are accomplished by adjusting the pedicle device, that is, by applying a combination of distraction and/or extension. In previous 3-dimensional testing studies the device adjustments affected the spinal construct stability differently in different directions [5]. But our results differ from the findings of previous studies because of the different load protocol used. We did not use the range of motion parameters in three planes of motion (flexion/extension, left/right lateral bending, and left/right axial rotation) because the compressive stiffness of the tested structure reflects the load-sharing between the implant and the injured spinal columns. Therefore, only the axial-compression and flexion-compression stiffness were calculated in the present study. The present biomechanical analysis showed that pedicle screw device fixation alone did not provide sufficient stability, especially under flexion-compression load. This may explain the fact that short-segment posterior instrumentation alone cannot completely prevent reduction loss and implant failure in treating burst fractures [3, 6]. The results of our study showed that compared with the intact spine, a 39% and 50% relative decrease of axial- and flexion-compression stiffness was noted after the burst fracture. Wang et al [7]. have also showed that despite fixation of the injured spine with pedicle screw instrumentation, the axial-compression and flexion-compression stiffness was still significantly lower than that of the intact spine. This may explain the fact that short-segment posterior instrumentation alone cannot completely prevent reduction loss and implant failure in treating burst fractures. Haher et al. [8] have shown that the anterior and middle column destruction of the spine reduces its load-carrying capacity (LCC) for flexion loads by 70%, while minimal change was observed in the LCC when the axis of loading was posterior to the posterior longitudinal ligament. Our study also demonstrated that the stiffness under flexion-compression was significantly lower than that under axial-compression, indicating mechanical properties in flexion were weaker. Thus patients should possibly be encouraged to rest in bed during the first three postoperative months. In this period, they should wear a brace when ambulating, and avoid activities that require bending forward. Although braces may not reduce loads on internal spinal fixation devices, they may protect the instrumented spine from the reflex overaction of the back muscles caused by sudden events, which substantially increases spine compressive loading [9-10]. In this way, the load on the anterior column may be reduced, and the incidence of early failure of implants may diminish. The adjustment combining 5mm distraction with 6° extension brought the spinal anatomy and the canal diameter closest to the intact state, while that provided axial- and flexion-compression stiffness smallest, compared to all other adjustments. Pure distraction achieved the maximum stability in axial- and flexion-compression stiffness. With this adjustment, posterior fixation could only restore the axial- and flexion-compression stiffness by 72% and 65% respectively. Transpedicular fixation alone cannot provide sufficient stability for thoracolumbar fractures. Posterior instrumentation combined with an anterior graft could offer as a possible solution. Wang et al. have showed that anterior graft with short-segment instrumentation for burst fracture greatly increases the biomechanical stability in the injured spine, thus suggesting that additional reconstruction of the anterior column may be necessary. The adjustments caused varying changes in anatomical reduction, neural decompression, especially stiffness restorations. The results of the study showed that the device adjustments of distraction and extension can be applied in any sequence, with the same results. For the decompression of the neural canal, the sequence of distraction and extension has been deemed important. Harrington et al. [11] suggested applying the distraction first, followed by extension. This was suggested based upon the concept that positioning the vertebra in lordosis without applying distraction significantly slackens the posterior longitudinal ligament. However, this concept was not based upon any quantitative data. Two limitations of the current study should be noted. The one is that the calf spine differs from the human spine anatomically, and mechanically. Despite these differences, the calf spine has been used widely to mode fractures because of its low variability and good bone quality. Another practicality of the calf model lies in structurally more closely replicated human anatomy in surgical techniques [12]. The other is that it was an in vitro study. The properties of the muscles and the muscle tone are absent. Also, the weight bearing and the dynamic muscle forces that will be present once the patient is up and performing daily activities also are absent. In clinical, the severity of the burst fracture can vary greatly. We have presented average results. The individual specimen results will vary from these average values. It is suggested that in future clinical studies the exact adjustments used in the pedicle screw devices be noted at the time of surgery. This will provide important information for subsequent further studies. References 1. Denis F. The three column spine and its significance in the classification of acute thoracolumbar spinal injuries. Spine 1983; 8: 817-31. 2. Dai LY, Jiang SD, Wang XY, et al. A review of the management of thoracolumbar burst fractures. Surg Neurol 2007; 3: 221-31. 3. MeCormack T, Karaikovie E, Gaines RW. The load sharing classification of spine fractures. Spine 1994; 19: 1741-4. 4. Panjabi MM, Hoffman H, Kato Y, et al. Superiority of incremental trauma approach in experimental burst fracture studies. Clin Biomech 2000; 15: 73-8. 5. Oda T, Panjabi MM. Pedicle screw adjustments affect stability of thoracolumbar burst fracture. Spine 2001; 26: 2328-33. 6. Cunningham BW, Sefter JC, Shono Y, et al. Static and cyclical biomechanical analysis of pedicle screw spinal constructs. Spine 1993; 18: 1677-88. 7. Wang XY, Dai LY, Xu HZ, et al. Biomechanical effect of the extent of vertebral body fracture on the thoracolumbar spine with pedicle screw fixation: an in vitro study. J Clin Neurosci 2008; 15: 286-90. 8. Haher TR, Tozzi JM, Lospinuso MF, et al. The contribution of the three columns of the spine to spinal stability: a biomechanical model. Paraplegia 1989; 27: 432-9. 9. Mannion AF, Adams MA, Dolan P. Sudden and unexpected loading generates high forces on the lumbar spine. Spine 2000; 25: 842-52. 10. Chen HH, Wang WK, Li KC, et al. Biomechanical effects of the body augmenter for reconstruction of the vertebral body. Spine 2004; 29: 377-8 11. Harrington RM, Budorick T, Hoyt J, et al. Biomechanics of indirect reduction of bone retropulsed into the spinal canal in vertebral fracture. Spine 1993; 18: 692-9. 12. Wilke HJ, Krischak S, Claes L. Biomechanical comparison of calf and human spines. Orthop Res 1996; 14: 500-3.     

体位复位结合短节段椎弓根螺钉撑开固定治疗胸腰段骨折疗效观察

目的探讨体位复位结合短节段椎弓根螺钉撑开复位治疗胸腰段骨折的临床策略。方法 30例胸腰段骨折患者麻醉后采用牵引手法体位复位,结合短节段椎弓根螺钉撑开固定,计算伤椎前、后缘高度比值,Cobb角改善情况。结果术后椎体高度恢复理想,后凸成角畸形矫正明显。平均随访16个月后,椎前、后缘高度比值,Cobb角明显改善。结论体位复位结合短节段椎弓根螺钉撑开固定治疗胸腰段骨折能有效恢复伤椎高度,减少后凸矫正角度丢失,临床效果满意。