Ultrasound melted polymer sleeve for improved primary pedicle screw anchorage: A novel augmentation technique

BackgroundCement augmentation of pedicle screws to prevent screw loosening is associated with significant complications, such as cement leakage or bone necrosis. Therefore, an alternative strategy to improve pedicle screw anchorage has been recently developed: Polymer reinforcement of pedicle screws uses an in situ melted polymer sleeve in order to enhance screw anchorage. This biomechanical study evaluated the effect of polymer-reinforcement by comparing polymer-reinforced pedicle screws to non-augmented as well as cement-augmented screws under cyclic loading.MethodsFor each of the two comparisons (polymer-reinforced vs. non-augmented screws and polymer-reinforced vs. cement-augmented screws), polymer-reinforced screws and control screws were placed into the left and right pedicle of seven vertebrae (mean age: 74.0 (SD 9.3) years) to allow for pairwise left–right comparisons. Each screw was subjected to cyclic cranio-caudal loading with an initial load ranging from −50 N to +50 N and with stepwise increasing compressive loads (5 N every 100 cycles) until screw loosening.FindingsPolymer-reinforced pedicle screws resisted a higher number of load cycles until loosening than the contralateral non-augmented control screws (4300 SD 2018 vs. 2457 SD 1116 load cycles, p = 0.015). Screw anchorage of polymer-reinforced pedicle screws was comparable to that of cement augmented control screws (3857 (SD2085) vs. 4300 (SD1257) load cycles until failure, p = 0.64).InterpretationOur findings indicate that polymer-reinforcement significantly enhances pedicle screw anchorage in low quality bone and that its effect is similar in size than that of cement augmentation.     

骨水泥强化椎弓根螺钉固定对骨质疏松患者有利无弊？

背景：在对伴骨质疏松的腰椎疾病患者进行椎弓根螺钉固定手术时,椎体添加骨水泥可有效增加内固定稳定性,但对相邻节段的影响尚不明确. 目的：观察伴骨质疏松的腰椎疾病患者进行椎体骨水泥强化内固定后,早中期随访中骨水泥强化对相邻节段的影响. 方法：以87例伴骨质疏松的腰椎疾病患者为研究对象,均行椎弓根螺钉系统固定＋后路椎管减压术,并分为3组：常规螺钉组,常规螺钉＋骨水泥组,可灌注骨水泥螺钉＋骨水泥组.样本平均随访6-18个月,平均随访为9个月.测量术前、术后3 d、末次随访的Oswestry功能障碍指数评分、固定节段上位相邻椎间隙高度、固定节段上位相邻椎体变形指数、固定节段椎体上缘终板及相邻上位椎体下缘终板凹陷角度、固定节段Cobb角. 结果与结论：①常规螺钉组、常规螺钉＋骨水泥组、可灌注骨水泥螺钉＋骨水泥组3组内末次随访功能障碍指数评分均较前明显减小（P〈0.05）,组间两两对比无显著差异（P〉0.05）.表明骨质疏松患者脊柱后路固定时,是否添加骨水泥及不同添加方式,对早中期主观疗效影响无显著差异,且均可明显改善患者生活质量.②常规螺钉＋骨水泥组、可灌注骨水泥螺钉＋骨水泥组2组末次随访对术后3 d固定节段Cobb角变化小于常规螺钉组（P 〈0.05）,常规螺钉＋骨水泥组、可灌注骨水泥螺钉＋骨水泥组2组组间差异无统计学意义（P 〉0.05）.表明添加骨水泥辅助的内固定稳定性明显优于未添加骨水泥常规手术.③常规螺钉＋骨水泥组、可灌注骨水泥螺钉＋骨水泥组2组术后3 d出现上终板凹陷角度增大;末次随访观察到相邻上位椎体下终板凹陷角度、椎体矩形指数及相邻椎间隙均减小,且前两项指标的改变程度明显大于常规螺钉组.表明添加骨水泥辅助内固定对相邻椎间盘退变程度无显著影响,但明显改变了相邻椎体终板及椎体的形态,增加了相邻椎体发生骨折的风险.     

Bone cement implantation syndrome during hip replacement in a patient with pemphigus and Parkinson’s disease: A case report

BACKGROUNDBone cement implantation syndrome (BCIS) is characterized by hypotension, arrhythmia, diffuse pulmonary microvascular embolism, shock, cardiac arrest, any combination of these factors, or even death following bone cement implantation.CASE SUMMARYAn 80-year-old patient with pemphigus and Parkinson’s disease underwent total hip replacement under spinal subarachnoid block and developed acute pulmonary embolism after bone cement implantation. The patient received mask mechanical ventilation with a continuous intravenous infusion of adrenaline (2 μg/mL) at a rate of 30 mL/h. Subsequently, the symptoms of BCIS were markedly alleviated, and the infusion rate of adrenaline was gradually reduced until the infusion was completely stopped 45 min later. The patient was then transferred to the Department of Orthopedics, and anticoagulation therapy began at 12 h postoperatively. No other complications were observed.CONCLUSIONThis is a rare case of BCIS in a high-risk patient with pemphigus and Parkinson’s disease.     

椎弓根螺钉置入内固定与单纯椎管减压治疗退行性腰椎滑脱的比较

背景：随着脊柱内固定和脊柱融合技术的发展,脊柱融合已成为腰椎退行性滑脱症毫无争议的＂金标准＂。同时,邻近节段退行性变的问题引起人们越来越多的关注。目的：观察椎弓根螺钉内固定置入植骨融合治疗退行性腰椎滑脱的临床疗效、手术节段稳定性及其对相邻节段的影响,并与单纯椎管加压进行对比。方法：选择天津医科大学总医院骨科收治的退行性腰椎滑脱患者38例,排除失访3例,余35例中采用椎弓根固定后外侧融合21例,单纯椎管减压14例。单纯椎管加压组用咬骨钳咬除黄韧带和椎板解除神经根后方的压迫,用骨凿凿除向前滑脱的椎体后缘与下位相邻椎体后缘形成的相对性突起;椎弓根螺钉固定植骨融合组按Wein-stein法定位椎弓根钉进针,拧入椎弓根螺钉,根据受压情况进行椎板减压。按Oswestry功能障碍指数综合评价临床疗效,观察过伸、过屈位时的水平位移及角移位,采用UCLA系统来评价邻近节段退变情况。结果与结论：35例患者随访时间1年。椎弓根螺钉固定植骨融合组优良率显著高于单纯椎管加压组（P〈0.05）。椎弓根螺钉固定植骨融合对腰椎稳定性影响不大,邻近节段退变置入前和置入后1年无明显变化。单纯椎管加压对腰椎稳定性影响显著,同时治疗前和治疗后1年邻近节段退变无明显变化。提示椎弓根螺钉内固定置入植骨融合治疗退行性腰椎滑脱疗效满意,对腰椎稳定性影响小,并且置入后早期对椎间盘的邻近节段影响不大。     

不同节段椎弓根钉置入脊椎内固定治疗腰椎滑脱

背景：对椎弓峡部裂腰椎滑脱、退行性腰椎滑脱的治疗,到底是采用短节段固定还是长节段固定争论很多。目的：观察短节段或长节段椎弓根钉内固定治疗腰椎滑脱的临床疗效。方法：腰椎滑脱患者146例,男36例,女110例,年龄22～73岁,平均53岁,病程1～18年,平均5年。采用腰椎管扩大开窗减压或全椎板切除减压、短节段或长节段椎弓根螺钉复位内固定、横突间或椎体间植骨融合。结果与结论：146例患者中采用短节段4枚椎弓根螺钉固定72例,长节段6枚椎弓根螺钉固定74例。椎间植骨101例,横突间植骨45例。术后随访134例,随访时间1.5～14年,按Steffee临床疗效分级标准,优74例,良41例,中13例,差6例,优良率85.8%。完全复位77例,其中短节段固定32例,长节段固定45例;部分复位69例,其中短节段固定40例,长节段固定29例。短节段固定者有8例13枚椎弓根螺钉发生断裂,而长节段固定者未发生椎弓根螺钉断裂。分析患者腰椎滑脱的类型、程度、病程长短、是否合并相邻节段椎间盘退变、不稳等情况,是选择用短节段还是用长节段置入固定的依据。     

椎弓根螺钉置入内固定与单纯椎管减压治疗退行性腰椎滑脱的比较

背景:随着脊柱内固定和脊柱融合技术的发展,脊柱融合已成为腰椎退行性滑脱症毫无争议的"金标准"。同时,邻近节段退行性变的问题引起人们越来越多的关注。目的:观察椎弓根螺钉内固定置入植骨融合治疗退行性腰椎滑脱的临床疗效、手术节段稳定性及其对相邻节段的影响,并与单纯椎管加压进行对比。方法:选择天津医科大学总医院骨科收治的退行性腰椎滑脱患者38例,排除失访3例,余35例中采用椎弓根固定后外侧融合21例,单纯椎管减压14例。单纯椎管加压组用咬骨钳咬除黄韧带和椎板解除神经根后方的压迫,用骨凿凿除向前滑脱的椎体后缘与下位相邻椎体后缘形成的相对性突起;椎弓根螺钉固定植骨融合组按Wein-stein法定位椎弓根钉进针,拧入椎弓根螺钉,根据受压情况进行椎板减压。按Oswestry功能障碍指数综合评价临床疗效,观察过伸、过屈位时的水平位移及角移位,采用UCLA系统来评价邻近节段退变情况。结果与结论:35例患者随访时间1年。椎弓根螺钉固定植骨融合组优良率显著高于单纯椎管加压组(P<0.05)。椎弓根螺钉固定植骨融合对腰椎稳定性影响不大,邻近节段退变置入前和置入后1年无明显变化。单纯椎管加压对腰椎稳定性影响显著,同时治疗前和治疗后1年邻近节段退变无明显变化。提示椎弓根螺钉内固定置入植骨融合治疗退行性腰椎滑脱疗效满意,对腰椎稳定性影响小,并且置入后早期对椎间盘的邻近节段影响不大。     

Influence of additional cement augmentation on endplate stability in circumferential stabilisation of osteoporotic spine fractures

BackgroundAnterior stabilisation of osteoporotic spine fractures is uncommon but necessary in the case of complex vertebral body comminution. The purpose of this study was to investigate the effect of additional cement-augmentation on the endplate stability.MethodsTwelve human cadaveric lumbar spines were divided in two groups: (A) posterior cement-augmented pedicle screw/rod-based instrumentation of L3 to L5, posterior decompression of L4/5 and partial corpectomy of L4 and (B) same experimental setup with additional cement-augmentation of the adjacent endplates. A cyclic loading test was performed at a frequency of 3 Hz, starting with a peak of 500 N for the first 2.000 cycles, up to 950 N for 100.000 cycles under a general preload with 50 N. All specimens were evaluated with regard to a potential collapse of the adjacent endplates. Subsequently, the maximum zero-time failure load of all specimens was determined using a universal testing machine.FindingsThe median T-score of bone density was −4.32 (range −2.97 to −5.59), distributed equally in the two groups (average age 83 years). The specimen of the endplate-augmented group showed a significant higher failure load compared to non-endplate-augmented cadavers (group A: 2038 N, group B: 2990 N, p = 0.03). All specimens passed the full cyclic loading protocol with 100.000 cycles. No significant difference was observable regarding the adjacent endplate subsidence.InterpretationAdditional cement augmentation in circumferential stabilisation resulted in a significant enhancement of the endplate stability regarding the maximum axial load, while the cyclic loading did not significantly enhance the fatigue endurance of the vertebral endplates over the 100,000 cycles tested.     

腰椎内固定中两种椎弓根钉加强技术与骨水泥的应用

背景：骨质疏松伴腰椎退行性病变行椎弓根钉固定骨质疏松的椎体后可能会出现螺钉的松动、脱落,使用固化材料强化椎弓根钉能提高治疗效果。目的：比较骨质疏松患者腰椎内固定中使用聚甲基丙烯酸甲酯骨水泥和可注射硫酸钙骨水泥加强椎弓根钉两种技巧的临床效果。方法：腰椎滑脱、腰椎失稳、严重腰椎管狭窄合并骨质疏松的患者共61例,根据治疗方式分为2组：传统聚甲基丙烯酸甲酯强化椎弓根钉组和可注射硫酸钙骨水泥强化椎弓根钉组。结果与结论：两组患者治疗操作时间、出血量、治疗前后目测类比评分、日本骨科协会评估治疗分数评分及改善率比较差异均无显著性意义（P〉0.05）。聚甲基丙烯酸甲酯组中2例患者出现了注入的骨水泥渗漏,随访未造成新的神经损伤。聚甲基丙烯酸甲酯组患者治疗后骨密度随着随访时间的延长未出现逐渐的增强趋势;硫酸钙骨水泥组患者治疗后骨密度出现渐进性的改善,与患者治疗后日本骨科协会评估治疗分数改善率呈线性相关。两组患者未出现螺钉松动、拔出及神经功能的异常。表明与聚甲基丙烯酸甲酯相似,硫酸钙骨水泥能增加椎弓根螺钉的稳定性。     

原位及复位融合腰椎滑脱的三维有限元分析

背景：由于脊柱结构复杂,对复位或原位融合后融合的腰椎节段应力分布变化特点的精确生物力学分析一直是个难点。目的：通过建立b5节段退变性滑脱原位椎间融合椎弓根钉内固定和复位椎间融合椎弓根钉内固定的三维有限元模型来比较腰椎滑脱原位融合和复位融合两种手术方式在各种载荷下的生物力学变化及其对腰椎稳定的影响。方法：根据健康成年男性的下腰椎CT数据,利用mimics,Catia和Patran,Marc等软件建立起b5节段的三维有限元模型,利用此模型模拟退变性腰椎滑脱,在此基础上建立L4／5节段原位椎间融合椎弓根钉内固定和复位椎间融合内固定模型,分析两模型在各种载荷下的应力分布特点,并比较异同。结果与结论：L舶节段退变性滑脱原位椎间融合椎弓根钉内固定和复位椎间融合椎弓根钉内固定三维有限元模型在前屈后伸侧屈旋转负荷下,该节段各部结构,包括椎体,椎弓根钉内固定器和椎问融合器上的应力变化没有显著差异。两模型都显示椎间融合器和椎弓根螺钉内固定器上分布的应力最大。结果表明退变性腰椎滑脱,行原位椎间融合内固定和复位椎间融合内固定后,复位与否对该节段生物力学没有显著影响。     

双侧钉棒及同侧单钉棒置入内固定的生物力学比较

背景：腰椎失稳、腰椎滑脱等腰椎退行性疾病常常需要实施腰椎融合,其目标是稳定脊柱,但究竟采取何种内固定方式仍存在争论。目的：比较单侧与双侧经椎间孔减压椎体间融合治疗腰椎退行性病变的生物力学差异。方法：人新鲜尸体腰椎标本6具,L4～5模拟微创经椎间孔减压椎体间融合,根据不同的内固定组合方式分为2组,即双侧钉棒组及同侧单钉棒组。在生物力学试验机上测量各种固定方式不同工况下的运动范围（ROM值）,并进行比较。结果与结论：以完整的腰椎运动单元为参照,两固定组的ROM值均低于对照组（P〈0.05）。其中双侧钉棒组在各工况下ROM值均显著低于同侧单钉棒组（P〈0.05）。提示在生物力学实验中,单侧椎弓根螺钉固定椎间融合生物力学性能优良,刚度适中,腰椎可获得可靠的稳定性。但与双侧钉棒固定比较,单钉棒方式仍然存在差距。     

应用Moss Miami椎弓根钉系统治疗胸腰椎爆裂骨折改善脊柱活动度及神经功能的评估

背景胸腰椎爆裂骨折的治疗,尤其是关于实施前、后路手术及减压范围,内固定装置的选择仍存在较大的争议.目的探讨Moss Miami系统治疗胸腰椎爆裂骨折,改善患者脊髓功能、脊柱活动度及下肢疼痛的效果.设计前后对照分析.对象选择广州市第一人民医院骨科脊柱外科2001-01/2003-06收治的胸腰椎爆裂骨折行Moss Miami椎弓根钉系统固定患者27例.患者均签署知情同意书.男17例,女10例;年龄19～65岁,平均32.8岁.损伤部位L114例,T12 6例,T12,L14例,L1,L2 2例,L1,L2,L3 1例;其中有脊髓损伤11例,Frankel分级为A级1例,B级2例,C级8例.术前CT显示椎管狭窄率(43±13.5)%.干预19例进行MossMiami椎弓根钉内固定加椎板间植骨融合术,8例经后外侧减压、半椎板切除,Moss Miami椎弓根钉内固定加后外侧横突间植骨融合术.脊髓功能恢复按Frankel分级评定(分为5级,A级为严重障碍,E级为正常);术后疗效评价根据神经功能、脊柱活动、腰背痛及下肢疼痛恢复情况评估(分为改善、无变化、加重).主要观察指标①患者应用Moss Miami椎弓根钉内固定术后疗效评价.②手术前后和随访时患者伤椎椎体前后高度及椎管狭窄率.③手术前后患者脊髓功能恢复情况.结果随访时间6个月,27例患者均进入结果分析.①Moss Miami椎弓根钉内固定术后疗效评价结果神经功能改善10例,无变化1例;脊柱活动改善26例,无变化1例;下肢疼痛改善10例,无变化17例;腰背痛改善23例,无变化3例,加重1例.②手术前后和随访时患者伤椎椎体前后高度及椎管狭窄率结果随访时伤椎前后高度及椎管狭窄率均较手术前有显著改善[伤椎前高度93.5%比44.2%;伤椎后高度90.7%比79.3%;椎管狭窄率(8.2±6.6)%比(43.0±13.5)%,P＜0.01].手术后和随访时比较无明显差异(P＞0.05).③术后脊髓功能Frankel分级评定结果11例脊髓损伤患者中,10例分别提高1～3级,1例A级无变化.结论Moss Miami系统治疗胸腰椎爆裂骨折,能明显改善患者脊髓功能,恢复椎体高度,操作简单,复位固定效果满意.     

椎弓根钉固定结合伤椎体植骨成形治疗胸腰段椎体骨折的护理体会

目的总结后路椎弓根钉固定结合伤椎体植骨成形治疗胸腰椎骨折患者的围术期护理体会。方法对16例胸腰椎骨折患者在行后路椎弓根钉固定结合伤椎体植骨成形术手术前后实施系统的康复指导。结果所有病例未发生压疮、肺部感染、泌尿系感染、下肢静脉血栓,无肺栓塞、无内固定松动及断裂等并发症。术后12个月行X片示脊柱Cobb′s角为（6.23±3.60）°,伤椎前缘高度丢失4%-7%,平均5.3%。Frankel功能分级：1例A级恢复为C级,2例B级恢复为D级,5例C级及8例D级均恢复为E级。结论正确的围术期护理及术后康复指导能有效提高手术成功率,促进患者功能恢复,减少并发症发生。     

胸腰椎B型骨折经伤椎单节段与跨伤椎短节段固定的对比研究

背景：后路经伤椎单节段固定与跨伤椎短节段固定是治疗胸腰椎B型骨折常用的方法,但两种术式的近远期疗效及各自优缺点尚未明确。 目的：探讨后路经伤椎置钉单椎间椎弓根螺钉复位固定与传统跨伤椎短节段固定治疗创伤性B型胸腰椎骨折,治疗后脊柱稳定性及对固定相邻节段椎间盘退变的影响。 方法：回顾性分析完成随访的AO分型B型胸腰椎骨折患者80例,按照不同的内固定方式分为经伤椎单节段固定组（n=40）和跨伤椎短节段固定组（n=45）。分别对两组患者的疼痛目测类比评分疼痛分级、ASIA脊髓功能分级、椎体前缘压缩率、椎管受堵指数、后凸Cobb角、UCLA相邻节段退变分级进行测量。 结果与结论：两组在ASIA脊髓功能分级、椎管受堵指数、后凸Cobb角的疗效相当。而在手术时间、手术出血量、疼痛目测类比评分疼痛分级、椎体前缘压缩率、UCLA相邻节段退变分级,单节段组要优于短节段组。后路经伤椎单节段固定及传统的短节段固定在治疗胸腰椎B型骨折上都有显著的疗效,而单节段固定组在椎体前缘压缩率的改善及疼痛目测类比评分评分的改善情况要明显优于短节段组。此种手术方式还具有手术时间短、创伤小、减少固定节段以节省脊柱的活动节段,减少固定节段的相邻节段椎间盘退变的优点。     

后路椎弓根钉固定联合椎间植骨融合治疗腰椎滑脱症

目的 评价后路椎弓根钉固定联合椎间植骨融合治疗腰椎滑脱症的临床治疗效果.方法 回顾性分析2006年10月至2009年10月收治的40例经后路椎弓根钉固定联合椎间植骨融合治疗腰椎滑脱症患者的临床资料.其中男22例,女18例;年龄38 ～ 75岁.滑脱部位:L4-5 28例,L5～S112例.根据Meyerding滑脱程度分级标准,Ⅰ度滑脱20例,Ⅱ度滑脱18例,Ⅲ度滑脱2例;峡部裂型滑脱15例,退行性滑脱25例.所有患者均采用后路减压、椎弓根螺钉系统固定联合椎间植骨融合术.结果 所有患者均得到随访,随访6～18个月,平均10.7个月.患者术后4～10个月植骨均融合,平均6.5个月.无1例发生内固定器械松动、断裂.末次随访时根据日本骨科学会(JOA)评分标准:治疗后12例评分改善率为93.8％,15例为87.5％,8例为81.3％,5例为75.0％,平均改善率为86.6％,均达显效.结论 后路椎弓根钉固定联合椎间植骨融合是治疗腰椎滑脱症的理想、有效的方法.     

Biomechanical testing of different posterior fusion devices on lumbar spinal range of motion

BackgroundRecent minimal-invasive posterior fusion devices are supposed to provide stability and obtain fusion in combination with interbody cages in the instrumented segment. The aim of the present study is to evaluate the primary stability of two minimal-invasive posterior prototypes compared to an established spinous process plate and standard pedicle screw instrumentation.MethodsSeven fresh frozen human cadaver lumbar spines (L2–L5) were tested in a spinal testing device with a moment of 7.5 Nm. Spinal stability was determined as mean range of motion (RoM) in the segment L3/L4 during extension-flexion, lateral bending and axial rotation. The RoM was measured during five conditions: 1. intact; 2. working prototype composed of an interspinous device and process plates; 3. an established spinous process fixation device 4. working prototype of facet fixation and 5. pedicle screw fixation.FindingsAll devices caused a significant reduction of RoM during extension-flexion. The RoM during lateral bending was significantly reduced to 37% (of intact) by pedicle screws and 68% by facet fixation prototype. During axial rotation the RoM was significantly reduced to 52% by pedicle screws and to 86% by facet fixation prototype. The other devices had no significant influence on RoM during lateral bending and axial rotation.InterpretationThe facet fixation prototype provided less primary stability compared to pedicle screws, but had significant advantages over spinous process fixation techniques. The results encourage further testing of this implant as a minimal-invasive approach for posterior fixation.     

后路椎弓根钉棒系统内固定椎间植骨术治疗腰椎滑脱伴椎管狭窄症

【目的】分析经后路椎弓根钉棒系统内固定椎间植骨（PLIF）治疗腰椎滑脱症的临床疗效【方法】采用后路椎弓根钉棒系统复位内固定,椎间及横突间植骨治疗28例腰椎滑脱症患者,从滑脱复位结果,融合成功率,术前术后疼痛改善情况,腰部功能改善以及并发症等方面进行评价。【结果】28例患者平均随访13个月,滑脱完全复位25例,占89．3％,不完全复位3例,占10．7％。全部患者都获得植骨融合,融合率100％。27例术后腰腿痛即消失。1例术后疼痛改善,1个月后疼痛消失。所有患者3个月后腰部活动良好。伸0°～20°,屈0°～40°,左侧弯0°～25°,右侧弯0°～25°。本组患者无钉棒松动或断裂,无神经损伤等并发症。【结论】采用后路椎板减压椎弓根钉棒系统内固定椎间植骨融合治疗腰椎滑脱,具有复位良好,融合可靠,疗效确切的特点,且减少了腰椎术后并发征的发生率。     

Biomechanical analysis of sagittal correction parameters for surgical instrumentation with pedicle subtraction osteotomy in adult spinal deformity

BackgroundHigh complication rate has been documented in spinal instrumentation with pedicle subtraction osteotomy. The objective was to analyze the biomechanics of spinal instrumentation with pedicle subtraction osteotomy as functions of three instrumentation parameters.MethodsPatient-specific biomechanical computer models of 3 adult patients who were instrumented with pedicle subtraction osteotomy were used to simulate the actual instrumentations and alternative instrumentations derived by varying instrumentation parameters: pedicle subtraction osteotomy wedge angle and rod contouring angle, location of the osteotomy, and number of rods (2 vs. 4).FindingsA change of the sagittal correction by +7.5° (−7.5°) resulted in a change in the screw axial forces and rods bending loads around the osteotomy by +38% (−19%) and +28% (−11%), respectively. The bending moments in the rods were 31% lower at the osteotomy site when it was located at one level above, and 20% higher when it was located at a level below. Additional rods allowed the rod bending and screw axial loads to be reduced by 24% and 22%, respectively.InterpretationThe amount of sagittal correction was positively correlated with loads sustained by the screws and rods. Rods were subjected to higher bending loads at the pedicle subtraction osteotomy site when it was done at a lower level. A 4-rod construct is an effective way to reduce the risk of rod breakage by reducing the loads sustained by the rods.     

椎弓根螺钉内固定及椎间植骨融合治疗退行性腰椎滑脱疗效

目的探讨经后路减压、椎间植骨融合加椎弓根螺钉内固定治疗老年性退行性腰椎滑脱症的临床疗效。方法本组28例经保守治疗无效的腰椎滑脱患者,采用椎板开窗减压＋椎间、椎旁植骨＋椎弓根螺钉内固定手术治疗。结果 28例术后随访6～24个月,内固定位置均良好,临床疗效优15例,良7例,一般5例,差1例,有效率78.6%。术后滑脱不同程度改善。结论后路减压、椎间植骨加椎弓根螺钉内固定是治疗退行性腰椎滑脱的一种安全有效的方法,临床疗效满意。     

Superior cortical screw in osteoporotic lumbar vertebrae: A biomechanics and microstructure-based study

BackgroundOsteoporosis reduces the bone-screw purchase, potentially reducing pullout strength and other biomechanical properties. However, the existing pedicle screw approach may not compensate for the detrimental effects of decreased vertebral bone mineral density.MethodsTwo methods of screw insertion were performed in thirteen cadaveric osteoporotic lumbar vertebrae: Magerl's method in the left pedicle, and superior cortical screw method in the right (its entry point located vertically 3 mm above Magerl's point). Before screw fixations, the pedicle and its corresponding vertebral body were divided into six equal layers from cranial to caudal by performing micro-CT and tested for microstructure properties, such as bone mineral density, trabecular bone volume fraction, trabecular thickness, trabecular separation and trabecular number. Further, pedicle was horizontally divided into three regions and tested. After screw fixations, microstructure properties of the bone surrounding the screws were analyzed. Finally, the screw pullout strength was tested biomechanically.FindingsThe bone structure is denser in the upper third of the pedicle and its corresponding vertebral body. A similar microstructure is seen within the pedicle. This study reveals that the pullout strength is significantly correlated to the bone mineral density, trabecular bone volume fraction and trabecular thickness. Biomechanical test showed pullout strength in the superior cortical screw group with mean 613.3 N (SD 200.4) was 22.4% higher than that in the Magerl group with mean 501.2 N (SD 256.6).InterpretationThe superior cortical screw method can be a reliable alternative, to provide better pullout strength for posterior lumbar instrumentation, especially in osteoporotic patients.     

腰椎椎弓根螺钉置入内固定前三维测量的临床应用

背景：椎弓根是连接椎体与椎板之间最坚强的骨性结构,通过椎弓根进行螺钉固定为重建脊柱稳定提供了可靠的力学基础。 目的：对腰椎椎弓根的三维模拟进钉的测量参数进行分析,提高椎弓根螺钉内固定临床应用的准确性和稳定性。 方法：分析椎弓根螺钉治疗脊柱（L1-L5）相关疾病患者的原始CT资料,利用Mimics软件建立三维多平面重建成像模型,通过Mimics软件对腰椎行三维重建并预测钉长、直径、水平面角及矢状面角度,并与临床置钉内固定后实际数据进行统计学比较。 结果与结论：病例分析可见内固定后置钉位置及长度均良好,未出现螺钉偏移、断裂等。内固定前模拟预测的椎弓根螺钉长、直径及水平面角与螺钉内固定后实际数据的差异无显著性意义（P〉0.05）,只有部分节段矢状面角度模拟值小于实际测量值（P〈0.05）。说明通过Mimics软件对腰椎进行三维重建模拟置钉并制定置钉参数,能比较精确的指导内固定中实际置钉,提高椎弓根螺钉的置钉安全。