腰椎弹性固定进展研究

对于腰椎退变和不稳的治疗,传统方法是采用后路减压、椎弓根螺钉固定同时行植骨术(僵硬固定)。然而,僵硬固定存在加速周围椎体的退变等缺点。因而,人们逐步把目光投向腰椎弹性固定。最近几年,腰椎弹性固定因具有利于应力分散,防止周围节段退行性变,降低应力遮挡等优点,越来越多地被用于临床。大多数临床资料显示相较于传统坚强固定,弹性固定疗效相当,而固定节段骨萎缩、骨质疏松以及邻近节段退变的发生率显著降低,更利于脊柱生理特性。该文就腰椎弹性固定的发展过程、各种类型弹性固定的工作原理以及临床效果等作一综述。     

经后路伤椎椎弓根钉固定治疗胸腰椎爆裂骨折的疗效观察

目的:探讨经后路伤椎椎弓根钉固定治疗胸腰椎爆裂骨折的临床疗效及安全性。方法:择取2014年1月至2016年12月我院收治的64例胸腰椎爆裂骨折患者,将其均分为研究组(n=32)与对照组(n=32)。研究组采用经后路伤椎椎弓根钉固定治疗,对照组采用经后路非伤椎置钉短节段椎弓根钉固定治疗,治疗后随访6个月。比较两组临床指标、并发症发生情况以及术前、术后1个月、6个月伤椎前缘高度比、Cobb角、疼痛数字评分量表(NRS)评分。结果:两组患者手术切口均实现I期愈合,术后无感染。与对照组相比,研究组手术时间较长(P0.05),术中出血量、住院时间比较无统计学差异(P0.05)。两组术前伤椎前缘高度比、Cobb角、NRS评分比较无统计学意义(P0.05);术后1个月、术后6个月两组伤椎前缘高度比较术前显著升高,Cobb角、NRS评分较术前显著降低,差异有统计学意义(P0.05)。术后6个月研究组Cobb角、NRS评分低于对照组(P0.05),两组伤椎前缘高度比比较无统计学意义(P0.05)。与对照组相比,研究组术后腰背痛、内固定失败发生率均较低(P0.05)。结论:对于胸腰椎爆裂骨折患者,经后路伤椎椎弓根钉固定可以有效改善临床指标,有利于术后身体恢复,减轻疼痛,安全性较高,值得临床推广。     

经骨折椎体椎弓根螺钉短节段固定治疗胸腰段骨折疗效

目的:评估和分析经骨折椎体椎弓根螺钉短节段固定治疗胸腰段单椎体粉碎性骨折的临床疗效。方法:选取胸腰段单椎体粉碎性骨折30例患者,分为两组,甲组20例,采用经骨折椎体椎弓根螺钉短节段固定治疗,均行骨折椎体及骨折椎体上下相邻椎体的椎弓根螺钉+双侧连接杆固定;乙组10例,只行骨折椎体的上下相邻椎体的椎弓根螺钉+连接杆固定术。术后随访。测定两组患者手术前后的椎体后凸畸形角和骨折椎体前方高度,评估其临床疗效。结果:术前平均后凸畸形角纠正:甲组15°,乙组11°,P0.05。术后骨折椎体前方的平均高度(和正常椎体前方高度比):甲组89%,乙组81%,P0.05;术后3个月随访:平均后凸畸形角纠正丢失,甲组2°,乙组6°,P0.05;骨折椎体前方的平均高度(和正常椎体前方高度比):甲组87%,乙组73%,P0.05。结论:经骨折椎体椎弓根螺钉短节段固定治疗胸腰段单椎体粉碎性骨折能提供更好的生物力学稳定性,更有利于骨折的复位和后凸畸形的纠正。     

人工半骨盆假体置换联合腰椎椎弓根螺钉固定术后生物力学的有限元分析

目的:建立人工半骨盆假体置换与联合腰椎椎弓根螺钉固定后的三维有限元模型,评价腰骶段生物力学改变后半骨盆假体力学结构的特点。方法:采用CT薄层扫描采集原始数据,分别建立正常骨盆、半骨盆假体置换术后以及半骨盆假体置换联合腰椎椎弓根螺钉固定术后骨盆的三维有限元模型,分别在第4腰椎上终板平面施以500 N的垂直纵向载荷,分析不同骨盆模型的应力分布特点。结果:与正常骨盆有限元模型相比,半骨盆假体置换术后健侧骨盆应力分布以骶髂关节、髋臼窝及耻骨为主,置换侧半骨盆假体以耻骨连接棒、髋臼杯及髂骨座为主,最大应力出现在耻骨连接棒,应力峰值为65.62 MPa。联合腰椎椎弓根螺钉固定后健侧应力相对减小,置换侧髂骨固定座与骶骨固定处应力相对减小,应力分布以腰椎椎弓根钉棒、耻骨连接棒及髋臼杯为主,最大应力出现在椎弓根螺钉,应力峰值为107 MPa。结论:半骨盆假体置换联合腰椎椎弓根螺钉固定后钉棒分担了半骨盆置换后健侧骨盆及置换侧髂骨固定座与骶骨固定处附近的部分应力,缓解应力集中现象,降低术后骨盆破坏风险,一定程度上增加了半骨盆置换后骨盆的稳定性。     

Trans-Endplate Pedicle Pillar System in Unstable Spinal Burst Fractures: Design,Technique, and Mechanical Evaluation

Background

Short-segment pedicle screw instrumentation (SSPI) is used for unstable burst fractures to correct deformity and stabilize the spine for fusion. However, pedicle screw loosening, pullout, or breakage often occurs due to the large moment applied during spine motion, leading to poor outcomes. The purpose of this study was to test the ability of a newly designed device, the Trans-Endplate Pedicle Pillar System (TEPPS), to enhance SSPI rigidity and decrease the screw bending moment with a simple posterior approach.

Methods

Six human cadaveric spines (T11-L3) were harvested. A burst fracture was created at L1, and the SSPI (Moss Miami System) was used for SSPI fixation. Strain gauge sensors were mounted on upper pedicle screws to measure screw load bearing. Segmental motion (T12-L2) was measured under pure moment of 7.5 Nm. The spine was tested sequentially under 4 conditions: intact; first SSPI alone (SSPI-1); SSPI+TEPPS; and second SSPI alone (SSPI-2).

Results

SSPI+TEPPS increased fixation rigidity by 41% in flexion/extension, 28% in lateral bending, and 37% in axial rotation compared with SSPI-1 (P<0.001), and it performed even better compared to SSPI-2 (P<0.001 for all). Importantly, the bending moment on the pedicle screws for SSPI+TEPPS was significantly decreased 63% during spine flexion and 47% in lateral bending (p<0.001).

Conclusion

TEPPS provided strong anterior support, enhanced SSPI fixation rigidity, and dramatically decreased the load on the pedicle screws. Its biomechanical benefits could potentially improve fusion rates and decrease SSPI instrumentation failure.     

数字化骨科理念辅助椎弓根置钉在寰枢椎不稳中的临床应用

目的:探讨3D打印辅助置钉技术用于寰枢椎不稳椎弓根置钉的安全性及准确性。方法:收集2013年1月到2015年1月西安交通大学第一附属医院收治的寰枢椎不稳病例,术前采用3D打印技术构建个体化3D打印模型,在模型上模拟置钉,获取最佳置钉点、置钉角度等个体化置钉数据,并于术中辅助椎弓根螺钉置入。通过CT扫描评价置钉准确性,测量术前、术后患者寰齿间隙判断寰枢椎复位情况,测量颈延角评价脊髓压迫改善情况,并采用日本骨科学会(JOA)评分判断患者脊髓功能改善情况。术后定期随访观察固定效果、稳定性、神经损伤等手术并发症的发生情况。结果:13例患者均采用3D打印辅助置钉技术进行内固定治疗,手术顺利,术中及术后无血管、神经损伤等并发症,复位及内固定效果满意。共置入椎弓根螺钉31枚,其中29枚完全在椎弓根内,置钉准确率为93.5%。寰枢椎较术前明显复位,术后寰齿间隙、颈延角和JOA评分较术前明显改善,差异具有统计学意义(P0.05)。结论:3D打印技术辅助上颈椎椎弓根置钉的准确性及安全性均较高。     

Treatment Results in the Different Surgery of Intradural Extramedullary Tumor of 122 Cases

Study Design

A retrospective study of intradural extramedullary tumor.

Objective

To compare the treatment results in the different surgeries of spinal intradural extramedullary tumor.

Methods

The study retrospectively reviewed 122 patients. The minimally invasive surgery (MIS) group was divided into Group A (hemilaminectomy + tumor microscopic excision) and Group B (laminectomy + tumor microscopic excision + pedicle screw fixation). Meanwhile, the non-MIS group was divided into Group C (hemilaminectomy + tumor excision), Group D (laminectomy + tumor excision), and Group E (laminectomy + tumor excision + pedicle screw fixation). In order to study postoperative spinal stability, we simultaneously divided all of the subjects into three categories, namely Group HE: hemilaminectomy + tumor excision; Group LE: laminectomy + tumor excision; and Group LEPSF: laminectomy + tumor excision + pedicle screw fixation.

Results

The MIS group exhibited fewer postoperative complications (p<0.05), better short-term clinical efficacy (p<0.05) and less non-surgical cost (p<0.05) than in non-MIS group. The rate of postoperative spinal instability in hemilaminectomy was lower than in laminectomy in a single spinal segment (p<0.05). The rate of postoperative spinal instability in laminectomy + pedicle screw fixation was lower than in hemilaminectomy and laminectomy in two or more spinal segments (p<0.05).

Conclusion

In the case of appropriate surgical indications, minimally invasive surgery for intradural extramedullary tumor is a useful method that can successfully produce good clinical results and reduce non-surgical cost. In addition, pedicle screw fixation helps avoid spinal postoperative instability.     

不同后路术式治疗胸腰椎爆裂骨折的临床效果比较

目的：探讨不同后路术式治疗胸腰椎爆裂骨折的临床效果。方法：将我院骨科收治的96例胸腰椎爆裂骨折患者随机分为两组,分别使用经伤椎椎弓根六钉固定法（六钉组,65例）和跨伤椎短节段四钉固定法（四钉组,31例）进行复位固定,测量并比较术后6个月两组矢状面Cobb角、冠状面Cobb角和伤椎椎体前缘压缩比及术后并发症情况的差异。结果：两组患者术前矢状面和冠状面Cobb角、伤椎椎体前缘压缩比的差异无统计学意义（P〉0．05）。术后6个月,六钉组矢状面Cobb角、伤椎椎体前缘压缩比、术后并发症发生率均显著低于四钉组（P〈0．05）,两组冠状面Cobb角均为0°。四钉组术后并发痘的发生率为22．6％,而六钉组术后并发症的发生率为4．6％,显著低于四钉组（P〈0．05）。结论：经伤椎椎弓根六钉固定法治疗胸腰椎爆裂骨折疗效优于跨伤椎短节段四钉固定法．且不良反应较少．具有较高的临床应用价值。     

Selection of fusion levels using the fulcrum bending radiograph for the management of adolescent idiopathic scoliosis patients with alternate level pedicle screw strategy: clinical decision-making and outcomes

ObjectiveSelecting fusion levels based on the Luk et al criteria for operative management of thoracic adolescent idiopathic scoliosis (AIS) with hook and hybrid systems yields acceptable curve correction and balance parameters; however, it is unknown whether utilizing a purely pedicle screw strategy is effective. Utilizing the fulcrum bending radiographic (FBR) to assess curve flexibility to select fusion levels, the following study assessed the efficacy of pedicle screw fixation with alternate level screw strategy (ALSS) for thoracic AIS.MethodsA retrospective study with prospective radiographic data collection/analyses (preoperative, postoperative 1-week and minimum 2-year follow-up) of 28 operative thoracic AIS patients undergoing ALSS was performed. Standing coronal/sagittal and FBR Cobb angles, FBR flexibility, fulcrum bending correction index (FBCI), trunkal shift, radiographic shoulder height (RSH), and list were assessed on x-rays. Fusion level selection was based on the Luk et al criteria and compared to conventional techniques.ResultsIn the primary curve, the mean preoperative and postoperative 1 week and last follow-up standing coronal Cobb angles were 59.9, 17.2 and 20.0 degrees, respectively. Eighteen patients (64.3%) had distal levels saved (mean: 1.6 levels) in comparison to conventional techniques. Mean immediate and last follow-up FBCIs were 122.6% and 115.0%, respectively. Sagittal alignment did not statistically differ between any assessment intervals (p>0.05). A decrease in trunkal shift was noted from preoperative to last follow-up (p = 0.003). No statistically significant difference from preoperative to last follow-up was noted in RSH and list (p>0.05). No "add-on" of other vertebra or decompensation was noted and all patients achieved fusion.ConclusionsThis is the first report to note that using the FBR for decision-making in selecting fusion levels in thoracic AIS patients undergoing management with pedicle screw constructs (e.g. ALSS) is a cost-effective strategy that can achieve clinically-relevant deformity correction that is maintained and without compromising fusion levels.     

Bony Healing of Unstable Thoracolumbar Burst Fractures in the Elderly Using Percutaneously Applied Titanium Mesh Cages and a Transpedicular Fixation System with Expandable Screws

IntroductionThere is a high incidence of vertebral burst fractures following low velocity trauma in the elderly. Treatment of unstable vertebral burst fractures using the same principles like in stable vertebral burst fractures may show less favourable results in terms of fracture reduction, maintenance of reduction and cement leakage. In order to address these shortcomings this study introduces cementless fixation of unstable vertebral burst fractures using internal fixators and expandable intravertebral titanium mesh cages in a one-stage procedure via minimum-invasive techniques.ResultsStabilization of the collapsed vertebral body was achieved in all 16 cases without any intraoperative complication. Surgical time averaged 102±6.6 minutes (71–194). The postoperative kyphotic angle (KA) and Cobb angle revealed significant improvements (KA 13.7° to 7.4°, p<0.001; Cobb 9.6° to 6.0°, p<0.002) with partial loss of reduction at final follow-up (KA 8.3°, Cobb 8.7°). VAS (Visual Analogue Scale) improved from 7.6 to 2.6 (p<0.001). Adjacent fractures were not observed. One minor (malposition of pedicle screw) complication was encountered.ConclusionCementless fixation of osteoporotic burst fractures revealed substantial pain relief, adequate maintenance of reduction and a low complication rate. Bony healing after unstable osteoporotic burst fractures is possible.

Trial Registration

www.germanctr.de DRKS00005657     

Statistical shape modelling of the thoracic spine for the development of pedicle screw insertion guides

Spinal fixation and fusion are surgical procedures undertaken to restore stability in the spine and restrict painful or degenerative motion. Malpositioning of pedicle screws during these procedures can result in major neurological and vascular damage. Patient-specific surgical guides offer clear benefits, reducing malposition rates by up to 25%. However, they suffer from long lead times and the manufacturing process is dependent on third-party specialists. The development of a standard set of surgical guides may eliminate the issues with the manufacturing process. To evaluate the feasibility of this option, a statistical shape model (SSM) was created and used to analyse the morphological variations of the T4–T6 vertebrae in a population of 90 specimens from the Visible Korean Human dataset (50 females and 40 males). The first three principal components, representing 39.7% of the variance within the population, were analysed. The model showed high variability in the transverse process (~ 4 mm) and spinous process (~ 4 mm) and relatively low variation (< 1 mm) in the vertebral lamina. For a Korean population, a standardised set of surgical guides would likely need to align with the lamina where the variance in the population is lower. It is recommended that this standard set of surgical guides should accommodate pedicle screw diameters of 3.5–6 mm and transverse pedicle screw angles of 3.5°–12.4°.

     

椎弓根螺钉强化技术联合PVP治疗kummell病的疗效及对患者脊柱稳定性和肢体功能的影响

摘要 目的：探究椎弓根螺钉强化技术联合经皮椎体成形术（PVP）治疗kummell病的疗效及对患者脊柱稳定性和肢体功能的影响。方法：选择2017年1月-2020年12月期间新疆医科大学第六附属医院和海军医科大学第二附属医院收治的64例kummell病患者,按照治疗方法分为PVP组（使用PVP治疗,32例）和强化组（使用椎弓根螺钉强化技术联合PVP治疗,32例）,比较两组围术期指标、脊柱稳定性、肢体功能及并发症。结果：强化组手术时长、术后住院时间长于PVP组,伤椎骨水泥注入量、透视次数、术中出血量多于PVP组,差异有统计学意义（P＜0.05）。末次随访时,两组伤椎局部Cobb角较术前降低,强化组低于PVP组,伤椎椎体前缘高度比较术前升高,强化组高于PVP组,差异有统计学意义（P＜0.05）。末次随访时,两组Roland-Morris功能障碍中文调查表（CRMDQ）、改良版Oswestry功能障碍指数量表（ODI）评分较术前降低,强化组低于PVP组,差异有统计学意义（P＜0.05）。两组随访期间腰背部疼痛、骨水泥渗漏、相邻椎体骨折等并发症差异无统计学意义（P＜0.05）。结论：PVP术治疗kummell病具有时间短、出血少、恢复快、透视次数少等明显优势,但椎弓根螺钉强化技术联合PVP治疗kummell病可以更好的保证脊柱稳定性,促进肢体功能恢复,且不增加并发症发生率。     

Real time noninvasive assessment of external trunk geometry during surgical correction of adolescent idiopathic scoliosis

Study design

Retrospective study.

Objective

To evaluate the radiological results of fusion with segmental pedicle screw fixation in juvenile idiopathic scoliosis with a minimum 5-year follow-up.

Summary of background data

Progression of spinal deformity after posterior instrumentation and fusion in immature patients has been reported by several authors. Segmental pedicle screw fixation has been shown to be effective in controlling both coronal and sagittal plane deformities. However, there is no long term study of fusion with segmental pedicle screw fixation in these group of patients.

Methods

Seven patients with juvenile idiopathic scoliosis treated by segmental pedicle screw fixation and fusion were analyzed. The average age of the patients was 7.4 years (range 5–9 years) at the time of the operation. All the patients were followed up 5 years or more (range 5–8 years) and were all Risser V at the most recent follow up. Three dimensional reconstruction of the radiographs was obtained and 3DStudio Max software was used for combining, evaluating and modifying the technical data derived from both 2d and 3d scan data.

Results

The preoperative thoracic curve of 56 ± 15° was corrected to 24 ± 17° (57% correction) at the latest follow-up. The lumbar curve of 43 ± 14° was corrected to 23 ± 6° (46% correction) at the latest follow-up. The preoperative thoracic kyphosis of 37 ± 13° and the lumbar lordosis of 33 ± 13° were changed to 27 ± 13° and 42 ± 21°, respectively at the latest follow-up. None of the patients showed coronal decompensation at the latest follow-up. Four patients had no evidence of crankshaft phenomenon. In two patients slight increase in Cobb angle at the instrumented segments with a significant increase in AVR suggesting crankshaft phenomenon was seen. One patient had a curve increase in both instrumented and non instrumented segments due to incorrect strategy.

Conclusion

In juvenile idiopathic curves of Risser 0 patients with open triradiate cartilages, routine combined anterior fusion to prevent crankshaft may not be warranted by posterior segmental pedicle screw instrumentation.     

Treatment of Upper Cervical Spine Instability with Posterior Fusion Plus Atlantoaxial Pedicle Screw

Clinical results of posterior fusion plus pedicle screw fixation in the treatment of upper cervical spine instability were taken under consideration. 24 patients with atlantoaxial instability were treated with C1-2 pedicle screws and rods fixation under general anesthesia. There were 18 males and 6 females with mean age of 49.8 years (age range 17–69 years). The postoperative radiographs verified good position of all screws, with satisfactory atlantoaxial reduction. Follow-up for 3–45 months (average 23 months) showed no spinal cord and vertebral artery injury or interfixation failure. Atlantoaxial alignment and stability were restored without complication due to instrumentation. In conclusion, posterior atlantoaxial pedicle screw and rod fixation provide immediate three-dimensional rigid fixation of atlantoaxial joint and are more effective techniques compared with previously reported techniques.     

经伤椎椎弓根螺钉固定治疗脊柱骨折的疗效及对患者疼痛、Cobb角的影响

目的:探讨经伤椎椎弓根螺钉固定治疗脊柱骨折的疗效及对患者疼痛、Cobb角的影响。方法:选择2013年2月至2018年2月我院接诊的脊柱骨折患者80例作为研究对象,以随机数表法分为观察组(n=41)和对照组(n=39)。对照组采用跨伤椎固定治疗,观察组采用经伤椎椎弓根螺钉固定治疗。比较两组患者临床手术指标、日本骨科协会评估治疗(JOA)评分、视觉模拟评分(VAS)、椎体压缩率、Cobb角水平及伤椎椎体高度。结果:观察组患者手术时间、术中出血量及住院时间均显著低于对照组(P0.05);治疗后,两组患者JOA评分、VAS评分均明显改善(P0.05),且观察组患者VAS评分显著低于对照组(P0.05);治疗后,两组患者椎体压缩率、Cobb角水平均明显改善(P0.05),且观察组患者椎体压缩率、Cobb角水平显著低于对照组(P0.05);两组患者治疗前椎体前、后缘高度无明显差异;治疗后,两组患者椎体前、后缘高度均明显改善(P0.05),且观察组患者椎体前、后缘高度显著高于对照组(P0.05)。结论:脊柱骨折患者采用经伤椎椎弓根螺钉固定治疗栓效果显著,可改善患者疼痛、Cobb角水平,值得临床推广。     

新型骨水泥椎弓根螺钉在治疗腰椎滑脱合并骨质疏松症的应用研究

目的:探讨评估聚甲基丙烯酸甲酯(polymethvlmethacnrlat, PMMA)增强的具有"渐变孔"结构的侧开孔中空椎弓根螺钉(Fenestrated pedicle screw, FPS)治疗腰椎滑脱症的安全性及疗效。方法:回顾性分析2013年1月～2017年12月收治32例合并有骨质疏松症的腰椎滑脱患者,均应用具有"渐变孔"结构的FPS融合手术治疗,记录手术时长、术中出血量,住院时长;测量椎间隙高度、椎体楔形变指数、滑脱距离、滑脱角、骨盆指数、腰椎前凸角;随访评估Oswestry功能障碍指数问卷表(Oswestry Disability Index Questionnaire, ODI)评分和视觉模拟评分法(Visual Analogue Score, VAS)评分,比较分析术前、术后及末次随访时的差异;结果:术中X线及术后三维CT检查发现3枚渗漏的骨水泥螺钉(2.2%),均为Yeom C型,术后无不适。随访7～61个月(平均34.9个月),滑脱复位良好,后凸畸形和矢状位失衡矫正良好,ODI评分和VAS评分均较术前有显著改善(p0.05)。随访期间,全部病例滑脱无复发,无椎弓根螺钉松动、断裂,无椎间隙塌陷,根据SUK标准融合成功率100%。结论:新型骨水泥螺钉能够提供良好的固定稳定性,并且能够避免骨水泥渗漏发生以及螺钉松动脱出,为骨质疏松脊柱手术提供一种新的选择。     

CT Morphometric Analysis to Determine the Anatomical Basis for the Use of Transpedicular Screws during Reconstruction and Fixations of Anterior Cervical Vertebrae

Background

Accurate placement of pedicle screw during Anterior Transpedicular Screw fixation (ATPS) in cervical spine depends on accurate anatomical knowledge of the vertebrae. However, little is known of the morphometric characteristics of cervical vertebrae in Chinese population.

Methods

Three-dimensional reconstructions of CT images were performed for 80 cases. The anatomic data and screw fixation parameters for ATPS fixation were measured using the Mimics software.

Findings

The overall mean OPW, OPH and PAL ranged from 5.81 to 7.49 mm, 7.77 to 8.69 mm, and 33.40 to 31.13 mm separately, and SPA was 93.54 to 109.36 degrees from C3 to C6, 104.99 degrees at C7, whereas, 49.00 to 32.26 degrees from C4 to C7, 46.79 degrees at C3 (TPA). Dl/rSIP had an increasing trend away from upper endplate with mean value from 1.87 to 5.83 mm. Dl/rTIP was located at the lateral portion of the anterior cortex of vertebrae for C3 to C5 and ipsilateral for C6 to C7 with mean value from −2.70 to −3.00 mm, and 0.17 to 3.18 mm. The entrance points for pedicular screw insertion for C3 to C5 and C6 to C7 were recommended −2∼−3 mm and 0–4 mm from the median sagittal plane, respectively, 1–4 mm and 5–6 mm from the upper endplate, with TPA being 46.79–49.00 degrees and 40.89–32.26 degrees, respectively, and SPA being 93.54–106.69 degrees and 109.36–104.99 degrees, respectively. The pedicle screw insertion diameter was recommended 3.5 mm (C3 and C4), 4.0 mm (C5 to C7), and the pedicle axial length was 21–24 mm for C3 to C7 for both genders. However, the ATPS insertion in C3 should be individualized given its relatively small anatomical dimensions.

Conclusions

The data provided a morphometric basis for the ATPS fixation technique in lower cervical fixation. It will help in preoperative planning and execution of this surgery.     

椎弓根内固定联合椎体间植骨融合术治疗退行性腰椎滑脱症的临床探讨

目的:探讨椎弓根内固定联合椎体间植骨融合术治疗退行性腰椎滑脱症的临床效果。方法:回顾性分析我院2012年3月至2014年3月收治的30例采用椎弓根内固定联合椎体间植骨融合术治疗的退行性腰椎滑脱症患者临床资料,观察患者对手术效果的满意度,并对症状进行JOA评分。比较患者术前术后的腰椎X线的影像学变化,观察术后临近节段的退变发生率与影像的融合率。结果:术后随访1-3年发现患者JOA评分的平均改善率为(73.81±16.12)%,术后滑脱率与椎间高度均有明显改善,与术前比较差异具有统计学意义(P0.05)。术后影像学显示植骨融合A级15例,B级12例,C级3例,融合优良率为90%。结论:椎弓根内固定联合椎体间植骨融合术对退行性腰椎滑脱症具有显著的临床效果,不仅可以缓解疼痛,改善功能评分,而且使患者影像学变化恢复正常生理形态,是理想的手术方法之一。     

Novel Pedicle Screw and Plate System Provides Superior Stability in Unilateral Fixation for Minimally Invasive Transforaminal Lumbar Interbody Fusion: An In Vitro Biomechanical Study

Purpose

This study aims to compare the biomechanical properties of the novel pedicle screw and plate system with the traditional rod system in asymmetrical posterior stabilization for minimally invasive transforaminal lumbar interbody fusion (MI-TLIF). We compared the immediate stabilizing effects of fusion segment and the strain distribution on the vertebral body.

Methods

Seven fresh calf lumbar spines (L3-L6) were tested. Flexion/extension, lateral bending, and axial rotation were induced by pure moments of ± 5.0 Nm and the range of motion (ROM) was recorded. Strain gauges were instrumented at L4 and L5 vertebral body to record the strain distribution under flexion and lateral bending (LB). After intact kinematic analysis, a right sided TLIF was performed at L4-L5. Then each specimen was tested for the following constructs: unilateral pedicle screw and rod (UR); unilateral pedicle screw and plate (UP); UR and transfacet pedicle screw (TFS); UP and TFS; UP and UR.

Results

All instrumented constructs significantly reduced ROM in all motion compared with the intact specimen, except the UR construct in axial rotation. Unilateral fixation (UR or UP) reduced ROM less compared with the bilateral fixation (UP/UR+TFS, UP+UR). The plate system resulted in more reduction in ROM compared with the rod system, especially in axial rotation. UP construct provided more stability in axial rotation compared with UR construct. The strain distribution on the left and right side of L4 vertebral body was significantly different from UR and UR+TFS construct under flexion motion. The strain distribution on L4 vertebral body was significantly influenced by different fixation constructs.

Conclusions

The novel plate could provide sufficient segmental stability in axial rotation. The UR construct exhibits weak stability and asymmetrical strain distribution in fusion segment, while the UP construct is a good alternative choice for unilateral posterior fixation of MI-TLIF.     

Micro-CT and micro-FE analysis of pedicle screw fixation under different loading conditions

Anchorage of pedicle screw instrumentation in the elderly spine with poor bone quality remains challenging. In this study, micro finite element (µFE) models were used to assess the specific influence of screw design and the relative contribution of local bone density to fixation mechanics. These were created from micro computer tomography (µCT) scans of vertebras implanted with two types of pedicle screws, including a full region-or-interest of 10 mm radius around each screw, as well as submodels for the pedicle and inner trabecular bone of the vertebral body. The local bone volume fraction (BV/TV) calculated from the µCT scans around different regions of the screw (pedicle, inner trabecular region of the vertebral body) were then related to the predicted stiffness in simulated pull-out tests as well as to the experimental pull-out and torsional fixation properties mechanically measured on the corresponding specimens. Results show that predicted stiffness correlated excellently with experimental pull-out strength (R² > 0.92, p < .043), better than regional BV/TV alone (R2 = 0.79, p = .003). They also show that correlations between fixation properties and BV/TV were increased when accounting only for the pedicle zone (R² = 0.66–0.94, p ≤ .032), but with weaker correlations for torsional loads (R² < 0.10). Our analyses highlight the role of local density in the pedicle zone on the fixation stiffness and strength of pedicle screws when pull-out loads are involved, but that local apparent bone density alone may not be sufficient to explain resistance in torsion.