Biomechanical evaluation of kyphoplasty with calcium sulfate cement in a cadaveric osteoporotic vertebral compression fracture model.

BACKGROUND CONTEXT: Vertebral compression fractures can cause deformity, pain, and disability. Kyphoplasty involves percutaneous insertion of an inflatable balloon tamp into a fractured vertebra followed by injection of polymethylmethacrylate (PMMA) bone cement. PMMA has several disadvantages such as potential thermal necrosis and monomer toxicity. Calcium sulfate cement (CSC) is nontoxic, osteoconductive, and bioabsorbable. PURPOSE: To evaluate the biomechanical performance of CSC for kyphoplasty in cadaveric osteoporotic vertebral bodies. STUDY DESIGN: Destructive biomechanical tests using fresh cadaveric thoracolumbar vertebral bodies. METHODS: Thirty-three vertebral bodies (T9 to L4) from osteoporotic cadaveric spines were disarticulated, stripped of soft tissue, and measured for height and volume. Each vertebral body was compressed at 0.5 mm/s using a hinged plating system on a materials testing machine to create an anterior wedge fracture and reduce the anterior height by 25%. Pretreatment strength and stiffness were measured. Two KyphX inflatable balloon tamps were used to reexpand each vertebral body. After randomization, three groups were created: Group A-no cement; Group B-PMMA; Group C-calcium sulfate cement. Groups B and C were filled with the corresponding cement to 25% of the vertebral body volume. All vertebral bodies were then recompressed by 25% of the post-kyphoplasty anterior height to obtain posttreatment strength and stiffness. RESULTS: Treatment with PMMA restored vertebral strength to 127% of the intact level (4168.2 N+/-2288.7) and stiffness to 70% of the intact level (810.0 N/mm+/-380.6). Treatment with CSC restored strength to 108% of the intact level (3429.6 N+/-2440.7) and stiffness to 46% of the intact level (597.7 N/mm+/-317.5). CSC and PMMA were not significantly different for strength restoration (p=.4). Significantly greater strength restoration was obtained with either PMMA or CSC, compared with the control group (p=.003 and .03, respectively). Stiffness restoration tended to be greater with PMMA than for CSC, but this difference was not statistically significant (p=.1). Both cements had significantly greater stiffness when compared with the control group (p=.001 and p=.04, respectively). CONCLUSIONS: Use of CSC for kyphoplasty yields similar vertebral body strength and stiffness as compared with PMMA. It may be a useful alternative bone cement for kyphoplasty. Further studies are required to assess the bioabsorption of CSCs after kyphoplasty in vivo.     

Biomechanical evaluation of kyphoplasty and vertebroplasty with calcium phosphate cement in a simulated osteoporotic compression fracture

 Kyphoplasty and vertebroplasty with polymethylmethacrylate (PMMA) have been used for the treatment of osteoporotic vertebral compression fractures. We performed kyphoplasty and vertebroplasty with α-tricalcium phosphate cement (CPC) and PMMA to compare the biomechanical properties. Thirty osteoporotic vertebrae were harvested from nine embalmed cadavers. We randomized the vertebrae into four treatment groups: (1) kyphoplasty with CPC; (2) kyphoplasty with PMMA; (3) vertebroplasty with CPC; and (4) vertebroplasty with PMMA. Prior to injecting the cement, all vertebrae were compressed to determine their initial strength and stiffness. They were then recompressed to determine their augmented strength and stiffness. Although the augmented strength was greater than the initial strength in all groups, there was no significant difference between the two bone cements for either kyphoplasty or vertebroplasty. The augmented stiffness was significantly less than the initial stiffness in the kyphoplasty groups, but the difference between the two cements did not reach significance. In the vertebroplasty groups, the augmented stiffness was not significantly different from the initial stiffness. There was no significant difference between the two bone cements for either procedure when cement volume and restoration of anterior height were assessed. We concluded that kyphoplasty and vertebroplasty with CPC were viable treatment alternatives to PMMA for osteoporotic vertebral compression fractures. Received: July 18, 2002 / Accepted: November 6, 2002 Offprint requests to: S. Tomita     

胸腰椎骨质疏松性骨折自固化磷酸钙骨水泥椎体成形的实验研究

目的探讨自固化磷酸钙骨水泥(calciumphosphatecement,CPC)注射椎体成形术后对胸腰椎骨质疏松性骨折椎体的力学影响。方法自愿捐赠的4具甲醛固定的老年尸体,取胸腰椎骨质疏松标本,平均年龄69岁,男、女各2具。每具标本随机取6个椎体,制备24个单椎体标本,建立前屈方向加载单椎体骨折模型。将CPC粉末与固化液以2.5g∶1ml调和制备CPC骨水泥,对骨折标本行CPC成形强化,每个椎体注射CPC约4ml。分别进行骨折前、成形后屈曲压缩力学检测。结果骨质疏松椎体标本骨折前最大载荷为1954±46N,位移长度为5.60±0.70mm,刚度为349±18N/mm;骨折间隙CPC填塞成形后最大载荷为2285±34N,位移为5.35±0.60mm,刚度为427±10N/mm,各指标骨折前和成形后比较差异均有统计学意义(P<0.05)。CPC加强成形后单椎体的承载能力强度较骨折前提高16.92%,刚度较骨折前提高22.31%。结论椎体内注射CPC能明显恢复骨质疏松骨折椎体的力学性能。     

复合重组人类骨形态发生蛋白-2的磷酸钙骨水泥应用于椎体成形术的体外生物力学评价

目的 通过将复合重组人类骨形态发生蛋白-2的注射型磷酸钙人工骨(rhBMP-2/CPC)应用于体外经皮椎体成形术(PVP),评价其生物力学性能.方法 5具完整老年脊柱标本(T10～L2),游离成30个椎体,随机分为3组:I组为空白对照组(n=10);Ⅱ组为PMMA组(n=10);Ⅲ组为rhBMP-2/CPC组(n=10).G形臂监视下,Ⅱ、Ⅲ组经双侧椎弓根分别充填PMMA及BMP-2/CPC 5 ml,注射后摄轴位X线片了解骨水泥分布情况,测试3组椎体静态压缩下的最大抗压强度及刚度.结果 平均最大载荷和刚度分别为:I组:(1595.6±165.0)N和(934.8±120.2)N/mm;Ⅱ组:(3025.4±210.2)N和(1570.7±190.0)N/mm;Ⅲ组:(2778.8±156.5)N和(1361.9±230.5)N/mm;最大载荷:I～Ⅲ组之间均差异有统计学意义(P＜0.05).刚度:I～Ⅲ组之间差异有统计学意义(P＜0.05).结论 rhBMP-2/CPC可以恢复骨质疏松椎体的力学性能.     

Mechanical efficacy of vertebroplasty: influence of cement type, BMD, fracture severity, and disc degeneration

INTRODUCTION: Osteoporotic vertebral fractures can be treated by injecting bone cement into the damaged vertebral body. "Vertebroplasty" is becoming popular but the procedure has yet to be optimised. This study compared the ability of two different types of cement to restore the spine's mechanical properties following fracture, and it examined how the mechanical efficacy of vertebroplasty depends on bone mineral density (BMD), fracture severity, and disc degeneration. METHODS: A pair of thoracolumbar "motion-segments" (two adjacent vertebrae with intervening soft tissue) was obtained from each of 15 cadavers, aged 51-91 years. Specimens were loaded to induce vertebral fracture; then one of each pair underwent vertebroplasty with polymethylmethacrylate (PMMA) cement, the other with another composite material (Cortoss). Specimens were creep loaded for 2 h to allow consolidation. At each stage of the experiment, motion segment stiffness in bending and compression was measured, and the distribution of compressive loading on the vertebrae was investigated by pulling a miniature pressure transducer through the intervertebral disc. Pressure measurements, repeated in flexed and extended postures, indicated the intradiscal pressure (IDP) and neural arch compressive load-bearing (F(N)). BMD was measured using DXA. Fracture severity was quantified from height loss. RESULTS: Vertebral fracture reduced motion segment stiffness in bending and compression, by 31% and 43% respectively (p<0.001). IDP fell by 43-62%, depending on posture (p<0.001), whereas F(N) increased from 14% to 37% of the applied load in flexion, and from 39% to 61% in extension (p<0.001). Vertebroplasty partially reversed all these effects, and the restoration of load-sharing was usually sustained after creep-consolidation. No differences were observed between PMMA and Cortoss. Pooled results from 30 specimens showed that low BMD was associated with increased fracture severity (in terms of height loss) and with greater changes in stiffness and load-sharing following fracture. Specimens with low BMD and more severe fractures also showed the greatest mechanical changes following vertebroplasty. CONCLUSIONS: Low vertebral BMD leads to greater changes in stiffness and spinal load-sharing following fracture. Restoration of mechanical function following vertebroplasty is little influenced by cement type but may be greater in people with low BMD who suffer more severe fractures.     

The biomechanics of vertebroplasty. The effect of cement volume on mechanical behavior.

STUDY DESIGN: Ex vivo biomechanical study using osteoporotic cadaveric vertebral bodies. OBJECTIVE: To determine the association between the volume of cement injected during percutaneous vertebroplasty and the restoration of strength and stiffness in osteoporotic vertebral bodies, two investigational cements were studied: Orthocomp (Orthovita, Malvern, PA) and Simplex 20 (Simplex P with 20% by weight barium sulfate content; Stryker-Howmedica-Osteonics, Rutherford, NJ). SUMMARY OF BACKGROUND DATA: Previous biomechanical studies have shown that injections of 8-10 mL of cement during vertebroplasty restore or increase vertebral body strength and stiffness; however, the dose-response association between cement volume and restoration of strength and stiffness is unknown. METHODS: Compression fractures were experimentally created in 144 vertebral bodies (T6-L5) obtained from 12 osteoporotic spines harvested from female cadavers. After initial strength and stiffness were determined, the vertebral bodies were stabilized using bipedicular injections of cement totaling 2, 4, 6, or 8 mL and recompressed, after which post-treatment strength and stiffness were measured. Strength and stiffness were considered restored when post-treatment values were not significantly different from initial values. RESULTS: Strength was restored for all regions when 2 mL of either cement was injected. To restore stiffness with Orthocomp, the thoracic and thoracolumbar regions required 4 mL, but the lumbar region required 6 mL. To restore stiffness with Simplex 20, the thoracic and lumbar regions required 4 mL, but the thoracolumbar region required 8 mL. CONCLUSION: These data provide guidance on the cement volumes needed to restore biomechanical integrity to compressed osteoporotic vertebral bodies.     

Vertebroplasty comparing injectable calcium phosphate cement compared with polymethylmethacrylate in a unique canine vertebral body large defect model.

BACKGROUND CONTEXT: Vertebroplasty was developed to mechanically reinforce weakened vertebral bodies. Polymethylmethacrylate (PMMA) bone cement has been most commonly used but carries risks of thermal injury and respiratory and cardiovascular complications. Calcium phosphate (CaP) offers the potential for biological resorption and replacement with new bone, restoring vertebral body mass and height. PURPOSE: To compare compressive strength, elastic modulus of the adjacent motion segments, and histologic response of vertebral bodies injected with either CaP or PMMA in a canine vertebroplasty model. STUDY DESIGN: By using a canine vertebroplasty model, two level vertebroplasties were performed at L1 and L3 and studied for 1 month (n=10) and 6 months (n=10). In each canine, one vertebral defect was randomly injected with either CaP cement (BoneSource; Stryker, Freiberg, Germany) or PMMA. METHODS: Twenty dogs had an iatrogenically created cavitary lesion at two nonadjacent levels injected with either CaP or PMMA. Canines from each group were tested mechanically (n=5) and histologically (n=5). Histology consisted of axial sections of the L1 and L3 vertebral bodies and high-resolution contact radiographs. Sections from each specimen were embedded in plastic without decalcification to study the bone-cement interface. Bone-cement interfaces were compared for evidence of necrosis, fibrosis, foreign body response, cement resorption, and new bone formation between the PMMA and CaP treatments groups. Mechanical compression testing was performed on specimens from the 1-month (n=5) and 6-month (n=5) time periods. The T13 vertebral body was used as an intact control for the destructive compression testing of L1 and L3. Each vertebral body was compressed to 50% of its original height under displacement control at 15 mm/min to simulate a nontraumatic loading situation. Force and displacement data were recorded in real time. RESULTS: Vertebral sites containing PMMA were characterized by a thin fibrous membrane. PMMA was detected within the trabeculae, vascular channels, and the spinal canal. Unlike PMMA, CaP underwent resorption and remodeling with vascular invasion and bone ingrowth. Woven and lamellar bone was found on the CaP cement surface, within the remodeled material, and on the surrounding trabeculae. Vertebral body compression strength testing revealed no significant difference in vertebral body height and compressive strength between PMMA and CaP. There was a trend for CaP-treated vertebrae to increase in compressive strength from 1 month to 6 months, whereas PMMA decreased compressive strength when compared with adjacent nontreated vertebrae. CONCLUSION: For both short and intermediate time periods, the injection of CaP cement can be an effective method to treat large vertebral defects. Early results indicate that CaP remodeling might result in the resorption of the majority of the cement with replacement by lamellar bone.     

不同充填材料应用于山羊经皮椎体成形术的组织学研究

目的:研究聚甲基丙烯酸甲酯(PMMA)、磷酸钙人工骨(CPC)和复合重组人骨形态发生蛋白-2的磷酸钙人工骨(rhBMP-2/CPC)在山羊骨质疏松症模型上行经皮椎体成形术(PVP)后的组织学表现。方法:6～8岁雌性山羊8只,均行双侧卵巢切除术,术后4个月建立骨质疏松症模型。在C形臂X线机监视下,随机选取8只山羊的L2-L6的两节椎体行PVP,分别充填PMMA、CPC和rhBMP-2/CPC,保证每只山羊的两节穿刺椎体的充填材料各不相同,术后4个月处死所有动物,取出椎体,组织学观察。结果:8只山羊16个椎体的PVP均成功,共出现4个椎体的渗漏。肉眼观察:PMMA与松质骨界限清晰,一个椎体取材时交界面出现破碎和脱落现象;而CPC和rhBMP-2/CPC与椎体内松质骨界限不清,互相融合生长。HE染色光镜观察:PMMA与骨小梁松散结合,界限明显,未见PMMA吸收和新生骨形成;CPC均匀分布于骨小梁和骨髓组织内,有CPC吸收现象,同时可见有新生软骨样团块形成,并有新生骨组织形成向其中心长入;rhBMP-2/CPC除了CPC的表现外,可见成骨活动活跃。结论:在组织学上,rhBMP-2/CPC和CPC均具有降解活性和骨传导活性,优于PMMA。rhBMP-2/CPC还具有诱导成骨活性,可能成为PVP中强化骨质疏松性椎体的首选充填材料。     

The use of an injectable, biodegradable calcium phosphate bone substitute for the prophylactic augmentation of osteoporotic vertebrae and the management of vertebral compression fractures.

STUDY DESIGN: A biomechanical study comparing two materials for augmentation of osteoporotic vertebral bodies and vertebral bodies after compression fracture. OBJECTIVES: To compare an injected, biodegradable calcium phosphate bone substitute with injected polymethylmethacrylate bone cement for strengthening osteoporotic vertebral bodies and improving the integrity of vertebral compression fractures. SUMMARY OF BACKGROUND DATA: Injection of polymethylmethacrylate bone cement into fractured vertebral bodies has been used clinically. However, there is concern about thermal damage to the neural elements during polymerization of the polymethylmethacrylate bone cement as well as its negative effects on bone remodeling. Biodegradable calcium phosphate bone substitutes have been studied for enhancement of fixation in fractured vertebrae. METHODS: Forty fresh osteoporotic thoracolumbar vertebrae were used for two separate parts of this study: 1) injection into osteoporotic vertebrae: intact control (n = 8), calcium phosphate (n = 8), and polymethylmethacrylate bone cement (n = 8) groups. Each specimen then was loaded in anterior compression until failure; 2) injection into postfractured vertebrae: calcium phosphate (n = 8) and polymethylmethacrylate bone cement (n = 8) groups. Before and after injection, the specimens were radiographed in the lateral projection to determine changes in vertebral body height and then loaded to failure in anterior bending. RESULTS: For intact osteoporotic vertebrae, the average fracture strength was 527 +/- 43 N (stiffness, 84 +/- 11 N/mm), 1063 +/- 127 N (stiffness, 157 +/- 21 N/mm) for the group injected with calcium phosphate, and 1036 +/- 100 N (stiffness, 156 +/- 8 N/mm) for the group injected with polymethylmethacrylate bone cement. The fracture strength and stiffness in the calcium phosphate bone substitute group and those in the polymethylmethacrylate bone cement group were similar and significantly stronger than those in intact control group (P < 0.05). For the compression fracture study, anterior vertebral height was increased 58.5 +/- 4.6% in the group injected with calcium phosphate and 58.0 +/- 6.5% in the group injected with polymethylmethacrylate bone cement as compared with preinjection fracture heights. No significant difference between the two groups was found in anterior vertebral height, fracture strength, or stiffness. CONCLUSION: This study demonstrated that the injection of a biodegradable calcium phosphate bone substitute to strengthen osteoporotic vertebral bodies or improve vertebral compression fractures might provide an alternative to the use of polymethylmethacrylate bone cement.     

Adjacent vertebral failure after vertebroplasty: a biomechanical study of low-modulus PMMA cement

PMMA is the most common bone substitute used for vertebroplasty. An increased fracture rate of the adjacent vertebrae has been observed after vertebroplasty. Decreased failure strength has been noted in a laboratory study of augmented functional spine units (FSUs), where the adjacent, non-augmented vertebral body always failed. This may provide evidence that rigid cement augmentation may facilitate the subsequent collapse of the adjacent vertebrae. The purpose of this study was to evaluate whether the decrease in failure strength of augmented FSUs can be avoided using low-modulus PMMA bone cement. In cadaveric FSUs, overall stiffness, failure strength and stiffness of the two vertebral bodies were determined under compression for both the treated and untreated specimens. Augmentation was performed on the caudal vertebrae with either regular or low-modulus PMMA. Endplate and wedge-shaped fractures occurred in the cranial and caudal vertebrae in the ratios endplate:wedge (cranial:caudal): 3:8 (5:6), 4:7 (7:4) and 10:1 (10:1) for control, low-modulus and regular cement group, respectively. The mean failure strength was 3.3 ± 1 MPa with low-modulus cement, 2.9 ± 1.2 MPa with regular cement and 3.6 ± 1.3 MPa for the control group. Differences between the groups were not significant (p = 0.754 and p = 0.375, respectively, for low-modulus cement vs. control and regular cement vs. control). Overall FSU stiffness was not significantly affected by augmentation. Significant differences were observed for the stiffness differences of the cranial to the caudal vertebral body for the regular PMMA group to the other groups (p < 0.003). The individual vertebral stiffness values clearly showed the stiffening effect of the regular cement and the lesser alteration of the stiffness of the augmented vertebrae using the low-modulus PMMA compared to the control group (p = 0.999). In vitro biomechanical study and biomechanical evaluation of the hypothesis state that the failure strength of augmented functional spine units could be better preserved using low-modulus PMMA in comparison to regular PMMA cement.     

Augmentation of anterior vertebral body screw fixation by an injectable, biodegradable calcium phosphate bone substitute.

STUDY DESIGN: A biomechanical study to evaluate the effects of a biodegradable calcium phosphate (Ca-P) bone substitute on the fixation strength and bending rigidity of vertebral body screws. OBJECTIVES: To determine if an injectable, biodegradable Ca-P bone substitute provides significant augmentation of anterior vertebral screw fixation in the osteoporotic spine. SUMMARY OF BACKGROUND DATA: Polymethylmethacrylate (PMMA) augmented screws have been used clinically; however, there is concern about thermal damage to the neural elements during polymerization of the PMMA as well as its negative effects on bone remodeling. Injectable, biodegradable Ca-P bone substitutes have shown enhanced fixation of pedicle screws. METHODS: Sixteen fresh cadaveric thoracolumbar vertebrae were randomly divided into two groups: control (no augmentation) (n = 8) and Ca-P bone substitute augmentation (n = 8) groups. Bone-screw fixation rigidity in bending was determined initially and after 10(5) cycles, followed by pullout testing of the screw to failure to determine pullout strength and stiffness. RESULTS: The bone-screw bending rigidity for the Ca-P bone substitute group was significantly greater than the control group, initially (58%) and after cyclic loading (125%). The pullout strength for Ca-P bone substitute group (1848 +/- 166 N) was significantly greater than the control group (665 +/- 92 N) (P < 0.01). Stiffness in pullout for the Ca-P bone substitute groups (399 +/- 69 N/mm) was significantly higher than the control group (210 +/- 51 N/mm) (P < 0.01). CONCLUSION: This study demonstrated that augmentation of anterior vertebral body screw fixation with a biodegradable Ca-P bone substitute is a potential alternative to the use of PMMA cement.     

椎体成形术或后凸成形术生物活性充填材料的体内降解

目的 观察磷酸钙骨水泥(CPC)和硫酸钙骨水泥(CSC)在椎体内的演变过程,为椎体成形术或后凸成形术中寻找更为合适的充填材料.方法 对24只成年雌性绵羊的L2～L5椎体制作骨缺损,随机注入CPC、CSC和聚甲基丙烯酸甲酯(PMMA),其中剩余的椎体作为空白对照,并以L6椎体作正常对照.术后2周、12周和24周分别随机处死其中8只绵羊,进行大体观察、生物力学测试、不脱钙组织学分析.结果 CSC组和CPC组椎体被填充材料明显增强,但CSC组椎体力学性能自2～12周呈现下降趋势,而到24周时又出现回升.CPC组椎体力学性能自2～24周呈上升趋势.12周时3组新骨形成量差异不明显,CSC已被大部分吸收;植入24周时新骨形成量CSC组＞空白组＞CPC组,CPC出现了明显的吸收,而CSC仅有少量残留.结论 CSC与CPC初期均能明显增强椎体;随着时间的推移,CSC在体内降解迅速,而CPC在体内降解缓慢.     

磷酸钙骨水泥在椎体成形术中的实验研究

目的 :模仿椎体成形术观察磷酸钙骨水泥 /聚甲基丙烯酸甲酯植入椎体后与椎体界面间的组织学差异。方法 :将PMMA和CPC植入到犬椎体 ,通过X线、CT、光镜、扫描电镜观察 2种材料与椎体界面间的微观结构变化。结果 :PMMA与椎体之间的结合是单纯的机械连接未能达到生物机械固定 ,CPC与骨界面间无排异反应的表现 ,是直接的骨小梁与生物材料之间的生物连接。结论 :磷酸钙骨水泥是椎体成形术中的一种比较理想的替代材料     

注射型磷酸钙骨水泥在椎体成形术中的组织学研究

目的 模仿椎体成形术观察注射型磷酸钙骨水泥(CPC)／聚甲基丙烯酸甲（polymethylmethacrylate，PMMA)植入椎体后的微观结构变化。方法 将PMMA和CPC植入到犬椎体，通过X线、CT、光镜、扫描电镜观察二种材料与椎体界面间的微观结构变化。结果 PMMA与椎体之间的结合是单纯的机械连接未能达到生物机械固定，CPC与骨界面间无排异反应的表现，是直接的骨小梁与生物材料之间的生物连接，CPC与椎体之间的结合是生物连接可达到生物机械固定的目的。结论 磷酸钙骨水泥是椎体成形术中治疗胸腰椎爆裂骨折一种比较理想的材料。     

胸腰椎骨质疏松骨折行CPC灌注成形的力学实验

目的探讨磷酸钙骨水泥(calcium phosphate cement,CPC)注射椎体成形术后对胸腰椎骨质疏松骨折椎体的力学影响。方法建立前屈方向加载单椎体骨折模型,对胸腰椎骨质疏松骨折标本行CPC成形强化,骨折前、成形后分别行屈曲压缩力学实验。结果椎体内注射CPC能明显恢复骨质疏松骨折椎体的力学性质。骨质疏松性胸腰椎标本行CPC灌注成形可以恢复椎体的强度和刚度,分别增加16.92%(P<0.05)和22.31%(P<0.05)。结论椎体内注射CPC能明显恢复骨质疏松骨折椎体的力学性质。     

椎体成形术治疗胸腰椎内固定术后置钉椎压缩性骨折疗效观察

目的 探讨椎体成形术在治疗胸腰椎内固定术后置钉椎压缩性骨折的临床疗效。方法 2016 年 6月至2019年6月期间,共有12例胸腰椎内固定术后置钉椎压缩性骨折患者于广州市增城区人民医院采用椎体成形术治疗。术后观察有无骨水泥渗漏、再次骨折及内固定松动断裂;收集手术前、术后3天、术后1月、术后3月、术后6月、术后12月患者疼痛视觉模拟评分（VAS）、椎体压缩率及Cobb 角。结果 所有患者随访12个月。仅1例发生骨水泥渗漏,无椎体再次骨折,无内固定松动断裂。术后腰背部VAS评分、椎体压缩率及Cobb 角相比术前具有统计学差异（P<0.05）。术后1月和术后3月、术后6月、术后12月对比,腰背部VAS评分、椎体压缩率及Cobb 角相比无统计学差异（P>0.05）。结论 椎体成形术用于治疗胸腰椎内固定术后置钉椎压缩性骨折可明显缓解腰背部疼痛,预防再次骨折、内固定松动断裂,是一种有效的治疗方法。     

Biomechanical evaluation of a new bone cement for use in vertebroplasty

STUDY DESIGN: Comparative ex vivobiomechanical study. OBJECTIVES: To determine the strength and stiffness of osteoporotic vertebral bodies subjected to compression fractures and subsequently stabilized via bipedicular injection of one of two bone cements: one is a commercially available polymethylmethacrylate (Simplex P) and one is a proprietary glass-ceramic-reinforced BisGMA/BisEMA/TEGDMA matrix composite that is being developed for use in vertebroplasty (Orthocomp). SUMMARY OF BACKGROUND DATA: Osteoporotic compression fractures present diagnostic and therapeutic challenges for the clinician. Vertebroplasty, a new technique for treating such fractures, stabilizes vertebral bodies by injection of cement. Little is known, however, about the biomechanics of this treatment. METHODS: Five vertebral bodies (L1-L5) from each of four fresh spines were harvested from female cadavers (age, 80 +/- 5 years), screened for bone density using DEXA (t = -3.4 to -6.4), disarticulated, and compressed in a materials testing machine to determine initial strength and stiffness. The fractures then were repaired using a transpedicular injection of either Orthocomp or Simplex P and recrushed. RESULTS: For both cement treatments, vertebral body strength after injection of cement was significantly greater than initial strength values. Vertebral bodies augmented with Orthocomp recovered their initial stiffness; however, vertebral bodies augmented with Simplex P were significantly less stiff than they were in their initial condition. CONCLUSIONS: Augmentation with Orthocomp results in similar or greater mechanical properties compared with Simplex P, but these biomechanical results have yet to be substantiated in clinical studies.     

Effects of bone cement volume and distribution on vertebral stiffness after vertebroplasty.

STUDY DESIGN: The biomechanical behavior of a single lumbar vertebral body after various surgical treatments with acrylic vertebroplasty was parametrically studied using finite-element analysis. OBJECTIVES: To provide a theoretical framework for understanding and optimizing the biomechanics of vertebroplasty. Specifically, to investigate the effects of volume and distribution of bone cement on stiffness recovery of the vertebral body. SUMMARY OF BACKGROUND DATA: Vertebroplasty is a treatment that stabilizes a fractured vertebra by addition of bone cement. However, there is currently no information available on the optimal volume and distribution of the filler material in terms of stiffness recovery of the damaged vertebral body. METHODS: An experimentally calibrated, anatomically accurate finite-element model of an elderly L1 vertebral body was developed. Damage was simulated in each element based on empirical measurements in response to a uniform compressive load. After virtual vertebroplasty (bone cement filling range of 1-7 cm3) on the damaged model, the resulting compressive stiffness of the vertebral body was computed for various spatial distributions of the filling material and different loading conditions. RESULTS: Vertebral stiffness recovery after vertebroplasty was strongly influenced by the volume fraction of the implanted cement. Only a small amount of bone cement (14% fill or 3.5 cm3) was necessary to restore stiffness of the damaged vertebral body to the predamaged value. Use of a 30% fill increased stiffness by more than 50% compared with the predamaged value. Whereas the unipedicular distributions exhibited a comparative stiffness to the bipedicular or posterolateral cases, it showed a medial-lateral bending motion ("toggle") toward the untreated side when a uniform compressive pressure load was applied. CONCLUSION: Only a small amount of bone cement ( approximately 15% volume fraction) is needed to restore stiffness to predamage levels, and greater filling can result in substantial increase in stiffness well beyond the intact level. Such overfilling also renders the system more sensitive to the placement of the cement because asymmetric distributions with large fills can promote single-sided load transfer and thus toggle. These results suggest that large fill volumes may not be the most biomechanically optimal configuration, and an improvement might be achieved by use of lower cement volume with symmetric placement.     

CPC/PMMA复合骨水泥在老年椎体后凸成形术中的初步应用研究

目的:从临床应用角度分析磷酸钙骨水泥(calcium phosphate bone cement,CPC)/聚甲基丙烯酸甲酯(polymethyl methacrylate,PMMA)骨水泥在老年骨质疏松性胸腰椎骨折患者椎体后凸成形术(percutanous kyphoplasty,PKP)治疗中的有效性及可靠性。方法:对2016年2月至2016年12月收治的单椎体胸腰段骨质疏松性压缩骨折接受PKP手术且骨密度≤-3.0 SD的62例患者进行回顾性分析,其中CPC/PMMA复合骨水泥组23例,年龄为(77.6±2.2)岁,PMMA骨水泥组39例,年龄为(77.1±1.1)岁。比较两组患者手术前后疼痛、椎体前缘高度比、局部Cobb角变化、术中骨水泥渗漏及术后邻椎骨折发生情况。结果:两组患者性别、年龄、随访时间以及术前疼痛、椎体前缘高度比、局部Cobb角等基本情况差异无统计学意义(P0.05)。术后1 d两组患者的疼痛、椎体前缘高度比、局部Cobb角均有所改善(P0.05),术后1 d及末次随访疼痛、椎体前缘高度比、局部Cobb角组间比较差异无统计学意义(P0.05),同时新发邻椎骨折、骨水泥渗漏情况组间比较差异也无统计学意义(P0.05)。两组患者术后随访疼痛均有持续改善(P0.05),局部Cobb角略有增加(P0.05);椎体前缘高度比略有下降(P0.05)。随访X线片或CT影像资料无法证实CPC降解及新骨形成长入。结论:CPC/PMMA复合骨水泥用于PKP治疗老年骨质疏松性胸腰椎压缩骨折安全可靠,可以有效缓解疼痛,维持椎体稳定,和PMMA骨水泥疗效相当。但目前尚无直接临床证据支持CPC/PMMA复合骨水泥可降低邻椎骨折发生率以及CPC降解、新骨长入骨水泥中,需要进一步研究。     

不同充填材料强化椎体在骨质疏松性椎体压缩骨折中的应用

目的分别以聚甲基丙烯酸甲酯骨水泥(PMMA)和注射型自固化磷酸钙人工骨(CPC)作为强化椎体的充填材料,采用椎体成形术和膨胀式椎体成形器(Sky)后凸成形术治疗骨质疏松性椎体压缩骨折,观察其临床疗效。方法对45例骨质疏松性椎体压缩骨折患者采用以下4种方法治疗:椎体成形术 PMMA(15例17个椎体),椎体成形术 CPC(13例16个椎体),Sky后凸成形术 PMMA(8例8个椎体),Sky后凸成形术 CPC(9例10个椎体)。根据患者术前和术后侧位X线片计算椎体高度压缩率和恢复率、椎体后凸角度和恢复率,并采用VAS(vasual analogscale)进行术前和术后疼痛评分。结果所有患者均未出现并发症。Sky后凸成形术椎体高度恢复率和后凸角度恢复率优于椎体成形术。椎体增强材料充填剂量各组间无显著性差异。椎体成形术与Sky后凸成形术手术时无显著性差异。VAS评分术前各组无显著性差异,术后充填PMMA者优于充填CPC者,术后6周两者间无显著性差异。结论用PMMA和CPC强化椎体是一种微创、安全、有效治疗骨质疏松性椎体压缩骨折的方法,应根据患者的具体情况选择治疗方法和椎体充填材料。