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。     

geneX®骨水泥强化椎弓根螺钉体内的实验研究

目的　通过动物实验,评估新型带负电荷硫酸钙/β-磷酸三钙复合骨水泥（geneX®）用于强化体内椎弓根螺钉的生物力学性质变化及可行性。 方法　选取 6只健康山羊腰椎L1～5双侧共 30个椎弓根随机分为 3组: geneX® 组, 聚甲基丙烯酸甲酯骨水泥（Polymethylmethacrylate,PMMA）组, 空白对照组, 每组 10个椎弓根。术后3个月处死动物取材行Mirco-CT检查、组织学检查及生物力学实验。 结果　轴向拔出力实验：geneX® 组 ( 803±155) N, PMMA组为( 994 ±122 ) N, 两者差异无统计学意义 (P >0.05)。两组均明显高于对照组的 ( 524±118) N,差异具有统计学意义 (P<0.05)。组织学观察及Mirco-CT显示geneX® 组中螺钉周围骨水泥已经完全降解、吸收, 骨小梁排列致密, 成熟骨小梁附近可见大量新生骨组织, 明显优于对照组及PMMA组。 结论　geneX® 骨水泥可有效强化椎弓根螺钉内固定的强度,其强化作用随时间推移而增强,对防止骨质疏松症患者内固定的拔出发生率有重要意义。     

骨水泥强化动力髋固定效果的生物力学研究

目的：研究A2型股骨转子间骨折动力髋螺钉（DHS）固定加骨水泥强化对内固定生物力学影响。方法：24对成年男性防腐股骨上段标本，制造A2型股骨转子间骨折，采用4孔DHS固定。每对股骨以左侧为非强化组，右侧为强化组，股骨头髓腔钉道填塞骨水泥。标本进行弯曲强度，扭转强度及破坏试验。测量骨折位移，转角及最大加载力。结果：强化组和非强化组在弯曲强度，扭转强度及最大加载力有显著差异（P〈0．05），有统计学意义。相对于非强化组，骨水泥强化后弯曲强度提高148％，扭转强度提高96％，最大加载力提高67％。结论：骨水泥强化有效地增加DHS固定强度，整体提高骨折稳定性，减少内固定失败的可能性。     

两种椎弓根螺钉钉道强化技术在骨质疏松绵羊椎体的应用

目的应用绵羊骨质疏松椎体标本比较两种骨水泥强化技术对椎弓根螺钉固定强度的影响。方法经体外脱钙建立绵羊骨质疏松椎体标本40节,完全随机分为A组(单纯螺钉组);B组(低剂量整体强化组);C1组(低剂量局部强化组);C2组(高剂量局部强化组)。骨密度(bone mineral density,BMD)检测;螺旋CT及MicroCT的影像学观察;测试最大轴向拔出力(Fmax)及能量吸收值(E)。结果各组BMD下降约25%～30%(P>0.05),成功建立骨质疏松椎体模型。影像学观察:B组螺钉完全被骨水泥包裹,形成"骨-骨水泥-螺钉"界面;C2组螺钉周围骨水泥呈局部对称分布,形成"骨-螺钉"和"骨-骨水泥-螺钉"的共存界面。B,C1,2组椎体的Fmax及E均显著高于A组(P<0.05);B,C2组椎体的Fmax及E均明显高于C1组(P<0.05);B,C2组椎体间Fmax及E无显著性差异(P>0.05)。结论钉道整体强化及局部强化技术均能显著提高骨质疏松情况下椎弓根螺钉的固定强度;钉道局部强化技术通过提高注射剂量,可以达到与整体强化技术相近的强化效果。     

含锶羟基磷灰石骨水泥强化动力髋螺钉的极限载荷性能测试

目的测试采用含锶羟基磷灰石骨水泥(Sr-HAC)强化动力髋螺钉(DHS)固定股骨粗隆间骨折后的极限载荷性能。方法 18具老年人骨质疏松股骨标本,随机分成三组,每组6例,对照组(正常标本),其中二组制成EvansⅢ型骨折模型,一组应用DHS固定,另一组应用Sr-HAC强化DHS固定,测量各组的最大载荷。结果正常标本组的极限载荷最大,Sr-HAC强化DHS内固定股骨粗隆间骨折的极限载荷次之,单纯DHS内固定组的极限载荷最小,其中Sr-HAC强化DHS组与单纯DHS内固定组相比差异有统计学意义(<0.05)。结论采用Sr-HAC DHS内固定,能提高DHS的极限载荷,可能减少内固定的失败。     

A parametric study of cylindrical pedicle screw design implications on the pullout performance using an experimentally validated finite-element model

The present study aims to the design of a finite-element model simulating accurately the pullout behaviour of cylindrical pedicle screws and predicting their pullout force. Three commercial pedicle screws, subjected to pure pullout from synthetic bone, were studied experimentally. The results were used for the design, calibration and validation of a finite-element model. Special attention was paid to the accurate simulation of the failure inside the host material under shear. For this purpose, a bilinear cohesive zone material model was adopted, controlling the mode-II debonding of neighbouring elements in the vicinity of the screw. Comparison between experimental and numerical results proved that the implementation of this approach can significantly enhance the accuracy of the numerical simulation of a screw's mechanical behaviour under pure pullout loads. The numerical model was used for the parametric study of various factors affecting the pullout performance of a cylindrical pedicle screw. It was concluded that the major parameter influencing the pullout force is the outer radius (increasing its value by 36% increases the pullout force by 34%). The influence of the purchase length of the screw is of similar quantitative nature. The respective dependence on the thread inclination, depth and pitch was significantly weaker.     

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。中国组织工程研究杂志出版内容重点：人工关节;骨植入物;脊柱;骨折;内固定;数字化骨科;组织工程全文链接：     

Biomechanical analysis of different types of pedicle screw augmentation: A cadaveric and synthetic bone sample study of instrumented vertebral specimens

This study aims to determine the pull-out strength, stiffness and failure pull-out energy of cement-augmented, cannulated-fenestrated pedicle screws in an osteoporotic cadaveric thoracolumbar model, and to determine, using synthetic bone samples, the extraction torques of screws pre-filled with cement and those with cement injected through perforations. Radiographs and bone mineral density measurements from 32 fresh thoracolumbar vertebrae were used to define specimen quality. Axial pull-out strength of screws was determined through mechanical testing. Mechanical pull-out strength, stiffness and energy-to-failure ratio were recorded for cement-augmented and non-cement-augmented screws. Synthetic bone simulating a human spinal bone with severe osteoporosis was used to measure the maximum extraction torque. The pull-out strength and stiffness-to-failure ratio of cement pre-filled and cement-injected screws were significantly higher than the non-cement-augmented control group. However, the cement pre-filled and cement-injected groups did not differ significantly across these values (p = 0.07). The cement pre-filled group had the highest failure pull-out energy, approximately 2.8 times greater than that of the cement-injected (p < 0.001), and approximately 11.5 times greater than that of the control groups (p < 0.001). In the axial pull-out test, the cement-injected group had a greater maximum extraction torque than the cement pre-filled group, but was statistically insignificant (p = 0.17). The initial fixation strength of cannulated screws pre-filled with cement is similar to that of cannulated screws injected with cement through perforations. This comparable strength, along with the heightened pull-out energy and reduced extraction torque, indicates that pedicle screws pre-filled with cement are superior for bone fixation over pedicle screws injected with cement.     

比较不同方式置入椎弓根钉内固定修复胸腰椎爆裂骨折的生物相容性

BACKGROUND: During the repair of thoracolumbar fracture, pedicle screw fixation is a commonly used treatment method. In the process of fixation, the different approaches can be used.  OBJECTIVE: To compare effect and biocompatibility of pedicle screw by percutaneous approach, posterior median approach, and intervertebral space approach for thoracolumbar fracture.  METHODS: 118 cases of thoracolumbar fracture were included after pedicle screw fixation. All patients were divided into three groups according to the approach: posterior median approach group (38 cases), intervertebral space approach group (40 cases) and percutaneous approach group (40 cases). After 12 months of follow-up, perioperative conditions, pain score, vertebral height of anterior border, kyphosis correction effect, adverse events and biological compatibility were compared among three groups. RESULTS AND CONCLUSION: (1) Operation time, intraoperative bleeding and time in bed after surgery were shorter or less in the percutaneous approach and intervertebral space approach groups than in the posterior median approach group. Postoperative drainage was better in percutaneous approach and intervertebral space approach groups than in the posterior median approach group (all P < 0.05). Except drainage in the percutaneous approach and intervertebral space approach groups, no significant difference in other indicators was found. (2) Patients received imaging examination at different time points. The percentage of anterior vertebral height and kyphosis were significantly improved immediately after treatment and in final follow-up (all P < 0.05). No significant difference was detected before treatment, immediately after treatment and in final follow-up. (3) Visual Analogue score was identical before treatment. Visual analogue score was lower in the percutaneous approach and intervertebral space approach groups than in the posterior median approach group at 24 hours and 3 days after treatment and in final follow-up (all P < 0.05). No significant difference was detectable at 24 hours and 3 days after treatment and in final follow-up between the percutaneous approach and intervertebral space approach groups. (4) No rejection or wound non-healing was seen at 12 months after treatment. Some patients suffered from mild low back pain, which was improved by active symptomatic treatment. (5) These findings suggest that intervertebral space approach percutaneous approach obtained satisfactory outcomes compared with posterior median approach for treatment of thoracolumbar spine fractures, and good biocompatibility was found.        

椎弓根钉内固定结合两种不同椎间植骨融合术治疗腰椎不稳的临床疗效

目的探讨两种不同椎间植骨融合术治疗腰椎不稳的临床疗效及各自优缺点。方法随访自2012年6月~2013年6月在我院分别采用两种不同的植骨方法对32例腰椎不稳患者进行手术,按照患者意愿随机分为打压植骨组和椎间融合器植骨组,观察并比较两组手术术后椎间隙高度变化,JOA评分,临床疗效优良率及植骨融合率等指标。结果术后患者均获随访,随访时间16~28月,平均23个月。两组术后及末次随访时椎间隙高度与术前相比均有显著提高,差异有统计学意义(0.05);与术后即刻比较,椎间融合器植骨组显著小于打压植骨组,差异有统计学意义(0.05)。术前两组均行JOA评分比较,差异均无统计学意义(0.05);末次随访时,各组JOA评分均较术前显著降低。术后1年复查X线片显示:椎间融合器植骨组植骨融合率均显著高于打压植骨组。结论椎弓根钉内固定结合椎间打压植骨融合与椎间融合器植骨融合治疗腰椎不稳,两种术式比较无明显临床疗效差异,可根据患者的具体情况选择相应术式。     

椎弓根钉内固定联合硫酸钙骨水泥椎体成形术治疗胸腰椎骨折32例临床分析

目的探讨椎弓根钉内固定联合硫酸钙骨水泥椎体成形术治疗胸腰椎骨折的优势、临床疗效及经验。方法选取我院2009年2月~2013年2月胸腰椎骨折患者32例,采用后路椎弓根钉内固定联合硫酸钙骨水泥椎体成形术治疗。术前术后及末次随访在侧位X线平片上测量Cobb角,伤椎前、后缘椎体高度,伤椎上、下相邻椎体的前、后缘高度并计算椎体前缘高度压缩率及椎体后缘高度压缩率。术前术后及末次随访分别评估神经功能损伤Frankel分级。结果 32例患者得到随访;术后及末次随访Cobb角、椎体前缘高度压缩率及椎体后缘高度压缩率与术前比较有显著差异(0.05);神经功能损伤按Frankel分级术后及末次随访与术前比较有显著差异(0.05)。结论椎弓根钉内固定联合硫酸钙骨水泥椎体成形术是一种治疗胸腰椎骨折切实有效的治疗手段。     

Time dependent mechanical properties of bone cement. An in vitro study over one year

Changes in mechanical properties of bone cements over time are of clinical importance, but not well documented. Specifications for testing do not address the time factor. This study recorded changes in compressive properties and microstructure of one bone cement stored under simulated physiological conditions (water at 37 degrees C) from 20 min up to 1 year and in dry air at 37 degrees C for comparison. Compressive strength increased within the first week (p < 0.001), decreased at 1 month (p < 0.001), and remained at that level at 1 year. Elastic modulus showed a similar development. Maximum strain values, indicating plastic deformability, increased continuously over 1 year. Microscopy revealed microcracks between the pre-polymer beads and the matrix in specimens tested after 20 min, whereas there were less cracks in 1 year specimens. Increase in strength during the first week is due to polymerization and formation of interpenetrating molecular networks. The subsequent decrease could be due to the plasticizing effect of water uptake, as supported by higher values for dry specimens. It can be speculated that microcracks which could be initiated while reducing an arthroplasty at 15 min, acting as initiators for fatigue fractures in the cement mantle, contribute to cement failure. It is recommended that testing of bone cements should be performed after extended ageing at simulated physiological conditions, for the present cement at least 5 weeks. Results obtained at less than one week could be influenced by ongoing polymerization, as well as microcracks and lower coherence between the prepolymer beads and the matrix.     

Vertebroplasty and kyphoplasty--a systematic review of cement augmentation techniques for osteoporotic vertebral compression fractures compared to standard medical therapy

After more than two decades the treatment effect of cement augmentation of osteoporotic vertebral compression fractures (VCF) has now been questioned by two blinded randomised placebo-controlled trials. Thus many practitioners are uncertain on the recommendation for cement augmentation techniques in elderly patients with osteoporotic VCF. This systematic review analyses randomised controlled trials on vertebroplasty and kyphoplasty to provide an overview on the current evidence. From an electronic database research 8 studies could be identified meeting our inclusion criteria of osteoporotic VCF in elderly (age>60 years), treatment with vertebroplasty or kyphoplasty, controlled with placebo or standard medical therapy, quality of life, function, or pain as primary parameter, and randomisation. Only two studies were properly blinded using a sham-operation as control. The other studies were using a non-surgical treatment control group. Further possible bias may be caused by manufacturer involvement in financing of three published RCT. There is level Ib evidence that vertebroplasty is no better than placebo, which is conflicting with the available level IIb evidence that there is a positive short-term effect of cement augmentation compared to standard medical therapy with regard to QoL, function and pain. Kyphoplasty is not superior to vertebroplasty with regard to pain, but with regard to VCF reduction (evidence level IIb). Kyphoplasty is probably not cost-effective (evidence level IIb), and vertebroplasty has not more than short-term cost-effectiveness (evidence level IV). Vertebroplasty and kyphoplasty cannot be recommended as standard treatment for osteoporotic VCF. Ongoing sham-controlled trials may provide further evidence in this regard.     

A comparative study of different electrophoretic techniques for classification of hereditary hyperlipoproteinaemias

The results of a comparative study of different electrophoretic techniques for phenotyping of human serum lipoproteins are reported. Electrophoresis in agarose gel was found to be preferable to electrophoresis on paper or cellulose acetate membranes.
Conditions giving reproducible results, also upon quantification of the lipoprotein zones by scanning of the electrophoretograms, were defined from methodological studies.     

Bone-bonding ability of bioactive bone cement under mechanical stress.

Bioactive bone cement (BABC) is able to bond to bone through a Ca-P rich layer. It was evaluated so far in a rat tibial model, where no mechanical stresses are supposed to take place. The objective is to investigate the behavior of BABC in the environment of posterolateral spinal fixation model, in which the bone cement interface is exposed to continuous mechanical stress. Japanese white rabbits were used. Fixation of L5-L6 segment was done by wiring the spinous and transverse processes of L5 and L6 vertebrae. Then BABC was applied over the transverse processes and the intertransverse process membrane on both sides. Polymethylmethacrylate (PMMA) bone cement was used similarly in the control group. Animals were sacrificed after 1 day, 4, 8, and 16 weeks postoperatively. Bone cement interface was examined using Giemsa surface staining and SEM, and affinity index was measured. Biomechanical testing was done nondestructively in right and left torsion. BABC bonded to bone directly with no intervening soft tissue at 4, 8, and 16 weeks, while soft tissue was consistently seen between PMMA bone cement and bone. BABC-spine constructs were stiffer than PMMA-spine constructs at all time intervals. BABC bonded directly to bone under mechanical stress and afforded stiffer fixation than PMMA bone cement.     

松质骨骨折不同位置螺钉固定效果的生物力学研究

目的：分析松质骨骨折不同位置的固定效果。方法：成人防腐固定的股骨、胫骨标本各１５侧,测股骨髁部、胫骨踝部密度。摹拟股骨外侧髁和胫骨内踝骨折,于骨折面中心Ｏ点、Ｏ点正上方Ａ点下方Ｂ点旋入金属拉力螺钉,应用生物力学方法,测试螺钉最大轴向拔出力。结果：股骨髁部骨密度平均为０．３０ｇ／ｃｍ＾２;踝部骨密度为０．４７ｇ／ｃｍ＾２。股骨外侧踝骨折面Ａ、Ｏ、Ｂ点螺钉的最大轴向拔出力分别为４０４．９Ｎ、２３３．８     

A new bioactive bone cement: effect of glass bead filler content on mechanical and biological properties.

A new bioactive bone cement (designated GBC), consisting of bioactive glass beads as an inorganic filler and polymethylmethacrylate (PMMA) as an organic matrix, has been developed. The purpose of the present study was to examine the effect of the amount of glass bead filler added to GBC on its mechanical and biological properties, and to decide the most suitable content of filler. Serial changes in GBC with time were also examined. The newly designed bioactive beads, consisting of MgO-CaO-SiO2-P2O5-CaF2 glass, were added to the cement in the proportions 30, 40, 50, 60, and 70 wt %. These cements were designated GBC30, GBC40, GBC50, GBC60, and GBC70, respectively. The compressive strength and the elastic modulus of bending of GBC increased as the glass bead content increased. The various types of GBC were packed into the intramedullar canals of rat tibiae to evaluate osteoconductivity, as determined by an affinity index calculated as the length of bone in direct contact with the cement expressed as a percentage of the total length of the cement surface. Rats were killed at 4 and 8 weeks after the operation and the affinity index was calculated for each type of GBC. Histologically, new bone had formed along the surface of all types of GBC within 4 weeks, even in GBC30 containing only 30 wt % of glass beads. At each time interval studied, there was a trend for the affinity index of GBC to increase as the glass bead filler content increased. There was no significant increase of affinity index between GBC60 and GBC70. The affinity indices for all types of GBC increased significantly with time up to 8 weeks. The handling properties of GBC were comparable to those of conventional PMMA bone cement. We conclude that when mechanical properties and osteoconductivity are both taken into consideration, GBC60 is the most suitable formulation; it shows excellent osteoconductivity and sufficient mechanical strength for clinical use.     

Quantitative analysis of the resorption and osteoconduction process of a calcium phosphate cement and its mechanical effect for screw fixation

The clinical application of calcium phosphate cements (CPCs) composed of tetracalcium phosphate and dicalcium phosphate anhydrous has been limited because of its longer setting time, so that we developed the CPC in which the setting time was shortened to approximately 10 min. Aiming at clinical application, we evaluated the histological response in the bone quantitatively and the biomechanical effectiveness of this substance. The CPC was implanted in the rabbit femoral condyle up to 52 weeks for histological evaluation. In mechanical testing, small cancellous screws were inserted into the condyle, both with and without augmentation with the CPC, and the pull-out strength was measured. The micro-computed tomography finding demonstrated that the cross-sectional area of the implanted CPC at 24 weeks was approximately two-thirds of the initial area. The amount of newly calcified bone around the CPC was significantly greater than that of the sintered hydroxyapatite. Histologically, the new bone was formed on the surface of the implanted CPC 1 week after the implantation and resorption of the CPC was evident at 3 weeks. The pull-out strength was enhanced significantly by augmentation with the CPC and the initial strength was maintained for a 6 week period. This CPC showed good osteoconductivity and was resorbed without adverse inflammation. Using the CPC as augmentation may be capable of useful treatment options in fractures with poor bone quality.     

Effect of vertebral cement augmentation with polymethylmethacrylate on intervertebral disc and bone tissue

Vertebral cement augmentation is reported to be a safe and effective technique for providing stabilization and pain relief. However, adjacent intervertebral discs may be at risk of accelerated degeneration as a result of aggravated nutritional constraints. Therefore, we investigated the effects of injecting polymethylmethacrylate (PMMA) into three adjacent lumbar vertebrae on intervertebral disc and vertebral bone tissue in 12 skeletally mature sheep. After 6 and 12 months of augmentation, the sheep were euthanized and their spines were processes for histological evaluation. Semiquantitative histomorphological analysis of discs and endplates was conducted using published criteria. Histomorphological changes in the augmented bone were assessed qualitatively. Approximately 80% of the length of the endplates was in contact with PMMA. However, there was no significant difference between the histopathological score of the discs adjacent to augmented vertebrae and the score of the control discs. Bone tissue reaction to PMMA was characterized by a thin fibrous tissue layer and occasional foreign-body reactions. New bone formation was present in all augmented vertebrae. Concerns about aggravation of disc degeneration as a result of vertebral cement augmentation seem to be unsubstantiated. Furthermore, adverse effects of PMMA cement on bone biology do not seem to be a relevant issue.