聚甲基丙烯酸甲酯强化对骨质疏松椎弓根螺钉固定的生物力学作用

目的探讨聚甲基丙烯酸甲酯 (polymethylmethacrylate,PMMA)骨水泥强化椎弓根螺钉的方法和评价 PMMA强化骨质疏松椎弓根螺钉后的生物力学性质。方法 6具新鲜老年女性胸腰段骨质疏松脊柱标本 (T10～ L5),使用双能 X线骨密度吸收仪测试每个椎体的骨密度,随机取 16个椎体 (32侧椎弓根 ),一侧椎弓根拧入 CCD螺钉,测量最大旋入力偶矩后拔出螺钉作为正常对照组,用 PMMA骨水泥强化椎弓根螺钉作为修复固定组,行螺钉拔出试验;另一侧经导孔直接强化椎弓根螺钉后拔出作为强化固定组,记录三组螺钉的最大轴向拔出力。结果椎体平均骨密度为 (0.445± 0.019)g/cm2;螺钉最大旋入力偶矩为（ 0.525± 0.104） Nm;正常对照组螺钉最大轴向拔出力为 (271.5± 57.3)N;修复固定组为 (765.9± 130.7)N;强化固定组为 (845.7± 105.0)N。 PMMA骨水泥强化或修复骨质疏松椎弓根螺钉后最大抗压力明显高于强化前,差异有非常显著性意义 (P< 0.01)。结论 PMMA骨水泥强化骨质疏松椎弓根螺钉能显著增加螺钉在椎体内的稳固性。     

磷酸钙骨水泥加强骨质疏松性肱骨近端骨折内固定的生物力学研究

目的 通过比较注射型磷酸钙骨水泥(CPC)和聚甲基丙烯酸甲酯(PMMA)骨水泥在加强骨质疏松性肱骨近端骨折内固定中的生物力学表现,探讨注射型CPC替代PMMA骨水泥作为肱骨近端骨缺损填充材料的可行性. 方法选择42个甲醛浸泡的老年女性尸体肱骨标本,制作成肱骨近端三部分骨折合并骨缺损模型.模型随机分三组:CPC填充组、PMMA骨水泥填充组和空白对照组,分别对三组标本进行压缩、拉伸及松质骨螺钉轴向拔出试验,测量极限压缩载荷、极限拉伸载荷及松质骨螺钉初始松动加载力等相关数据. 结果 CPC组和PMMA组的最大压缩载荷、拉伸载荷和螺钉松动强度均显著高于空白对照组,差异有统计学意义(P<0.05);而CPC组和PMMA组之间差异无统计学意义(P>0.05). 结论注射型CPC能够获得与PMMA骨水泥近似的力学强度,可以认为是能够较好替代PMMA骨水泥的生物材料.     

磷酸钙骨水泥强化椎弓根螺钉对骨质疏松性椎体骨折的临床意义

目的 :评价磷酸钙骨水泥 (calciumphosphatecement ,CPC)强化和修复椎弓根螺钉的生物力学效果。方法 :6具新鲜老人骨质疏松的脊柱标本 ,从T11～L4 共 36个椎体 ,随机选取其中 32个 ,分为 4组 ,每组 8个。A组 :随机选择一侧椎弓根放置直径为 6 .5mm的椎弓根螺钉 ,另一侧以直径为 3.5mm的钻头导孔。向两侧椎弓根孔道注入配制好的磷酸钙骨水泥 (CPC) 3～ 5ml ,体温下 ( 37℃ )放置 2 4h后 ,再行前述拔出实验。B组 :应用PMMA进行修复和强化 ,作为对照 ,操作方法同A组。C组 :植入椎弓根螺钉 ,添加或不添加CPC ,进行周期抗屈实验。D组 :相同方法 ,应用PMMA作为对照。结果 :CPC骨水泥强化组和修复组拔出力明显高于对照组 ,差异有显著性意义 (P <0 .0 5)。结论 :在植入椎弓根螺钉时添加具有生物活性的磷酸钙 (CPC)骨水泥可显著提高其初始稳定性     

碳酸化羟基磷灰石水泥复合活性多肽修复骨缺损的研究

目的 通过动物实验观察碳酸化羟基磷灰石水泥复合活性多肽P19修复骨缺损的效果。方法 在10只杂种犬肱骨近端制作骨缺损动物模型，采用碳酸化羟基磷灰石水泥复合活性多肽P19修复骨缺损，并以单纯碳酸化羟基磷灰石水泥作为对照，在修复骨缺损后5d，4、8、12、16周处死动物，通过X线和组织学观察其修复效果。结果 实验组和对照组修复材料均能完全充填骨缺损，界面与骨组织结合紧密，生物相容性良好，随着植入时间的延长，实验组修复材料可逐渐降解并被新生骨爬行替代，而对照组降解和新生骨替代速度相对较慢。结论 碳酸化羟基磷灰石水泥是一种新型的骨缺损修复材料，活性多肽P19后可以促进碳酸化羟基磷灰石成骨和降解性能。     

磷酸钙骨水泥强化螺钉固定的研究进展

老年性或继发性骨质疏松患者骨折采用螺钉固定，容易松动、拔出。临床上应用聚甲基丙烯酸甲酯强化螺钉固定取得了一定的效果，但PMMA术中和术后伴有聚合热效应、毒性反应及PMMA不可吸收等缺点，其临床应用受到了限制。磷酸钙骨水泥则因其克服了PMMA以上的缺点而倍受关注。本文介绍了磷酸钙骨水泥强化螺钉固定的研究近况。     

CPC提高椎体钉固定强度的体外实验研究

目的探讨磷酸钙骨水泥(calcium phosphate cement,CPC)强化骨质疏松椎体钉后穿透单侧椎体皮质固定的可行性。方法选用新鲜成人尸体胸腰段骨质疏松标本24个,实验组为骨水泥(PMMA)和磷酸钙骨水泥灌注后椎体钉穿透单侧椎体皮质固定;对照组为无骨水泥强化,螺钉穿透双侧椎体皮质固定。应用螺钉拔出实验,记录螺钉最大拔出力并观察椎体破坏形态。结果三组拉出力值PMMA组(811.19±188.58N)、CPC组(541.89±101.44N)、对照组(374.21±77.66N)差异有显著性,P<0.01。分别增加122%±56%和50%±37%。对照组(8例)螺钉拔出破坏时均为螺钉抽出,在8例PMMA强化椎体中所有椎体均有不同程度骨折。而在8例CPC强化椎体中仅1例发生椎体骨折。结论应用CPC强化骨质疏松椎体钉简化手术步骤、增加手术安全性是可行的。     

直入式注入PMMA骨水泥强化椎弓根钉内固定生物力学研究

【摘要】 目的 分析直入式骨水泥注入椎体强化方法在体外提高螺钉稳定性的效果。方法采用新鲜尸体脊柱标本共24个椎体,一侧椎弓根采用直入式注入PMMA骨水泥强化椎弓根钉固定作(试验组),另一侧椎弓根采用常规椎弓根螺钉固定(对照组),两侧进行最大轴向拔出力试验、最大旋出力矩试验、周期抗屈试验生物力学测试,比较两组测试结果。结果〓骨水泥强化组中螺钉的稳定性均显著强于单纯常规椎弓根螺钉组(P < 0.05)。结论〓应用PMMA行椎体强化椎弓根钉固定有利于增强对椎弓根钉的把持力,可有效防止椎弓根钉的松动及脱落,具有良好的临床效果。     

注射型磷酸钙骨水泥和PMMA在椎体成形术中的生物力学研究

目的:模仿椎体成形术观察注射型磷酸钙骨水泥(calcium phosphate cement CPC)/聚甲基丙烯酸甲酯(polymethylmethacrylate,PMMA)植入椎体后的生物力学改变.方法:将PMMA和CPC通过手术植入到犬椎体,经过8周和16周后分别取材,行X线、CT检查,并测定不同时间椎体的轴向抗压强度和抗扭转强度.结果:(1)植入早期,PMMA的抗压强度明显高于正常椎体和CPC(P＜0.01),CPC的抗压强度明显低于正常椎体和PMMA(P＜0.01).术后8周显示,PMMA的抗压强度有所下降(P＜0.01=0.009),CPC的抗压强度有所上升(P＜0.05=0.034),但与正常椎体相比仍差别显著.术后16周显示PMMA抗压强度继续下降(P＞0.05=0.710),CPC的抗压强度继续上升(P＞0.05=0.648),与正常椎体相比无显著性差异.(2)植入早期,PMMA的抗扭转强度明显高于正常椎体和CPC(P＜0.05=0.03),CPC的抗扭强度明显低于正常椎体和PMMA(P＜0.05=0.02).术后8周显示,PMMA的抗扭强度有所下降,但与正常椎体相比仍差别显著(P＜0.05=0.045),CPC的抗压强度有所上升与正常椎体相比差异不显著(P＞0.05=0.078).术后16周显示PMMA抗压强度继续下降(P＞0.05=0.137),CPC的抗压强度继续上升,与正常椎体相比无显著性差异(P＞0.05=0.847).结论:磷酸钙骨水泥是椎体成形术中治疗椎体压缩性骨折和胸腰椎爆裂骨折一种比较理想的材料,注入到椎体后,其生物力学强度有逐渐增强的趋势,而PMMA是机械固定,其生物力学强度有逐渐减弱的趋势.     

前交叉韧带重建术后腱-骨和骨-骨界面愈合的比较研究

目的 探讨并比较两种移植物重建前交叉韧带(anterior cruciate ligament,ACL)后早期移植物隧道界面愈合的生物学机制. 方法 55只成年新西兰大白兔,体重2.0～2.8 kg.左膝关节切取带胫骨.骨块的髌韧带作为供区,右膝关节作为自体移植重建ACL受区.移植物骨块端为骨.骨界面愈合模型,韧带端为腱.骨界面愈合模型.术后观察实验动物一般情况,术后第2、4和8周取材(n=5)行大体及组织学观察,并于第4、8周取材(n=20)进行生物力学检测. 结果 术后动物肢体活动情况良好,实验过程中ACL连续性完整,张力适中.组织学观察:术后2周骨.骨界面大部分区域为纤维组织连接,腱一骨界面主要为肉芽组织填充;术后4周骨.骨界面大部分区域骨性愈合,腱.骨界面可见成骨反应及大量成纤维细胞;术后8周骨.骨界面已完全骨性愈合,腱.骨界面部分区域可见Sharpey纤维,形成间接止点.生物力学观察:术后4周腱-骨界面拔出率为85%,骨.骨界面为15%;术后8周腱.骨界面拔出率为95%,骨.骨界面为5%;各时间点骨.骨界面拔出率与腱一骨界面拔出率比较差异均有统计学意义(P<0.001). 结论 ACL重建术后早期骨一骨界面较腱.骨界面在愈合强度和速度上具有优势.     

注射型磷酸钙骨水泥和PMMA在椎体成形术中的生物力学研究

目的模仿椎体成形术观察注射型磷酸钙骨水泥(calcium phosphate cement CPC)/聚甲基丙烯酸甲酯(polymethylmethacrylate,PMMA)植入椎体后的生物力学改变.方法将PMMA和CPC通过手术植入到犬椎体,经过8周和16周后分别取材,行X线、CT检查,并测定不同时间椎体的轴向抗压强度和抗扭转强度.结果(1)植入早期,PMMA的抗压强度明显高于正常椎体和CPC(P＜0.01),CPC的抗压强度明显低于正常椎体和PMMA(P＜0.01).术后8周显示,PMMA的抗压强度有所下降(P＜0.01=0.009),CPC的抗压强度有所上升(P＜0.05=0.034),但与正常椎体相比仍差别显著.术后16周显示PMMA抗压强度继续下降(P＞0.05=0.710),CPC的抗压强度继续上升(P＞0.05=0.648),与正常椎体相比无显著性差异.(2)植入早期,PMMA的抗扭转强度明显高于正常椎体和CPC(P＜0.05=0.03),CPC的抗扭强度明显低于正常椎体和PMMA(P＜0.05=0.02).术后8周显示,PMMA的抗扭强度有所下降,但与正常椎体相比仍差别显著(P＜0.05=0.045),CPC的抗压强度有所上升与正常椎体相比差异不显著(P＞0.05=0.078).术后16周显示PMMA抗压强度继续下降(P＞0.05=0.137),CPC的抗压强度继续上升,与正常椎体相比无显著性差异(P＞0.05=0.847).结论磷酸钙骨水泥是椎体成形术中治疗椎体压缩性骨折和胸腰椎爆裂骨折一种比较理想的材料,注入到椎体后,其生物力学强度有逐渐增强的趋势,而PMMA是机械固定,其生物力学强度有逐渐减弱的趋势.     

In vivo response of bone defects filled with PMMA in an ovine model

The use of PMMA cement is common in arthroplasty for cemented fixation and defect filling. Concerns remain regarding effects of cement curing temperature on the viability of cancellous bone. In this study we filled surgically-created defects (mean volume 0.585±0.251 mL) in the cancellous bone of the distal femur and proximal tibia of 6 sheep with PMMA and measured temperature changes in surrounding bone whilst the cement cured, using 3 thermocouples per defect. Animals were euthanised at 3 (n=3) and 12 (n=3) weeks postoperatively and the bone-cement interface assessed histologically. Despite mean maximum temperatures of 49.3±10.2 °C (range: 40.9 °C - 82.2 °C) thermonecrosis was not a common histological feature at either timepoint. The exposure of bone to high cement temperatures in this study has not led to bone necrosis and/or tissue damage.     

Optimization of screw fixation in rat bone with extracorporeal shock waves

Screw fixation in osteoporotic patients is becoming an increasing problem in orthopaedic surgery as deterioration of cortical and cancellous bone hamper biomechanical stability and screw fixation. This might result in delayed weight‐bearing or failure of instrumentation. We hypothesized that local peri‐operative shock wave treatment can optimize osseointegration and subsequent screw fixation. In eight female Wistar rats, two cancellous and two cortical bone screws were implanted in both femora and tibiae. Immediately after implantation, 3.000 unfocused extracorporeal shock waves (energy flux density 0.3 mJ/mm²) were applied to one side. The other side served as non‐treated internal control. Evaluation of osseointegration was performed after 4 weeks with the use of microCT scanning, histology with fluorochrome labeling, and pull‐out tests of the screws. Four weeks after extracorporeal shock wave treatment, treated legs exhibited increased bone formation and screw fixation around cortical screws as compared to the control legs. This was corroborated by an increased pull‐out of the shock wave treated cortical screws. The cancellous bone screws appeared not to be sensitive for shock wave treatment. Formation of neocortices after shock wave therapy was observed in three of eight animals. Furthermore, de novo bone formation in the bone marrow was observed in some animals. The current study showed bone formation and improved screw fixation as a result of shock wave therapy. New bone was also formed at locations remote from the screws, hence, not contributing to screw fixation. Further, research is warranted to make shock wave therapy tailor‐made for fracture fixation. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:76–84, 2018.

     

Long-term follow-up study of bioactive bone cement for repairing a segmental defect in a canine femur

We report on a 7-year long-term follow-up study of a bioactive bone cement (BA cement) that was used to repair a segmental defect in a canine femur. Bilateral femoral segmental defects were repaired with metallic implants that were fixed to the femur using two kinds of bone cement. The BA cement used in this study consists of an apatite- and wollastonite-containing glass ceramic (AW-GC) with a bis-phenol-alpha-glycidyl methacrylate (bis-GMA)-based resin. The bone-cement interface was examined histologically. Previous short-term studies have shown that using BA cement for segmental replacement of the canine femur produced excellent biomechanical and histological results. The BA cement maintained the fixation of a metallic implant to the femur very well. In contrast, the PMMA cement did not maintain alignment under long-term weight-bearing conditions. The results of histological examinations showed direct bonding between the BA cement and bone, while an intervening soft tissue layer was observed at the bone-cement interface with the PMMA cement. The BA cement bonded to the bone through a Ca-P-rich reactive layer, which was twice as thick after 7 years than it was at 26 weeks. No adverse effects of BA cement were observed during the 7-year observation period.     

Holding power and reinforcement of cancellous screws in human bone.

The authors report an in vitro biomechanical evaluation of a biodegradable material that might be used for the reinforcement of surgical screws in fractures involving severely osteoporotic bone. The material is a particulate composite with a matrix phase consisting of a hydrolyzable prepolymer, polypropylene fumarate (PPF), crosslinked with methacrylate monomer, and a particulate phase consisting of tricalcium phosphate and calcium carbonate. Pullout force and stripping load of cancellous screws were determined along with screw pullout force before and after reinforcement with either polymethylmethacrylate (PMMA) or PPF composite. Pullout force was moderately correlated (R2 = 0.59) with apparent density by a power law relationship of the form 0.065p1.37-1.77. Stripping load was strongly correlated (R2 = 0.91) with apparent density by a power law of the form 0.13p1.35-93.8. Mean pullout force before and after reinforcement with PMMA was 382 +/- 100 N (mean +/- standard deviation) and 879 +/- 315 N, respectively. Mean pullout force before and after reinforcement with PPF composite was 571 +/- 294 N and 829 +/- 354 N, respectively. Although the increase in pullout force with cement reinforcement was highly significant in both cases, the magnitude of the increase did not depend on the type of cement. Thus PPF seems to provide reinforcement that is equivalent to that provided by PMMA.     

Mechanical evaluation of fracture fixation augmented with tricalcium phosphate bone cement in a porous osteoporotic cancellous bone model

OBJECTIVE: The purpose of this study was to examine the effects of resorbable bone cement on screw and plate-screw fracture fixation in a porous osteoporotic bone model. METHODS: Experiment 1: Screw pullout strength was assessed for 4 sets of 4.5-mm cortical screws inserted into a synthetic osteoporotic cancellous bone model, including screws inserted without cement augmentation (control), screws augmented with tricalcium phosphate (TCP) bone cement (Norian SRS; Synthes USA, Paoli, PA), and screws augmented with polymethylmethacrylate. Experiment 2: The effects of cement augmentation on plate-screw fixation strength were examined by performing cantilever bending tests on 4 sets of 8 plate-screw constructions, including nonaugmented and TCP-augmented standard and locked screw-plate constructions in a similar bone model. RESULTS: Experiment 1: Cement augmentation with both TCP and polymethylmethacrylate increased screw pullout strength from a porous osteoporotic cancellous bone model by about 4-fold (P < 0.05), and there was no significant difference between the 2 cements (P > 0.1). Experiment 2: Fixation strength was 1.5 times higher for locked plates compared with standard plates when neither was augmented with cement (P = 0.07). Cement augmentation with TCP improved fixation strength by 3.6 times for a standard plate-screw construction (P < 0.05) and 3.3 times for a locked plate-screw construction (P < 0.05). The most stable construction was the TCP-augmented locked plate, in which a 5-fold increase was observed compared with that of standard plates without TCP (P < 0.05). CONCLUSIONS: This study indicates augmenting screws with TCP cement during osteosynthesis improves fixation strength in an osteoporotic cancellous bone model. CLINICAL RELEVANCE:: In fracture situations in which osteoporotic bone makes screw and screw-plate fixation tenuous, screw augmentation with TCP cement should be considered as adjunct treatment.     

Bioactive ceramic coating of cancellous screws improves the osseointegration in the cancellous bone

Background  

A number of methods for coating implants with bioactive ceramics have been reported to improve osseointegration in bone, but the effects of bioactive ceramic coatings on the osseointegration of cancellous screws are not known. Accordingly, biomechanical and histomorphometric analyses of the bone-screw interface of uncoated cancellous screws and cancellous screws coated with four different bioactive ceramics were performed.     

Biomechanical comparison of augmented versus non‐augmented sacroiliac screws in a novel hemi‐pelvis test model

Operative treatment of sacral insufficiency fractures is frequently being complicated by osteopenic bone properties. Cement augmentation of implanted sacroiliac screws may lead to superior construct stability and prevent mechanical complications. A novel hemi‐pelvis test model with dissected symphysis was developed. Five fresh‐frozen cadaveric pelvises were vertically osteotomized at the sacrum on both sides and fixed with sacroiliac screws in both corridors of the first sacral vertebral body. One side was randomly augmented with bone cement. Cyclic testing consisting of torsional loading (±2.5 Nm) combined with progressively increasing axial loading (+50 N compression, −10 N traction, ±0,01 N/cycle) was performed until failure; simulated physiological loads derived from inverse dynamic calculations. The fixation was analyzed fluoroscopically quantifying screw migrations and assessing failure mechanisms. Failure modes were cut‐out, pull‐out, screw‐out, and washer penetration. Motion at fracture site was analyzed via optical motion tracking. Unscrewing was provoked four times with non‐augmented and twice with augmented screws. When focusing on the sacral region only, cement augmentation significantly improved screw fixation in terms of increased number of cycles to failure (p = 0.043). However, when considering overall construct stability, there was no significant difference between augmented and non‐augmented state due to washer penetration at the iliac bone. The generated hemi‐pelvis model was found to be valid due to the reproduction of the clinically observed failure mode (unscrewing). Unscrewing was not fully prevented by cement augmentation. Augmentation effects stability at the screw tip, but particularly in porotic bone, failure may shift to the next weak point. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1485–1493, 2017.

     

比格犬体内涂层螺钉-骨组织界面的组织学观察

目的了解钛涂层、羟基磷灰石(hydroxyapatite,HA)涂层及钛+HA复合涂层螺钉置入体内后,螺钉-骨界面在术后早期的骨整合情况。方法选取成年比格犬16只平均分为普通螺钉组、HA涂层螺钉组、钛涂层螺钉组及钛+HA复合涂层螺钉组(每组4只,雌雄各2只)。螺钉置入比格犬颈椎椎体3个月,之后取出椎体,进行脱水、包埋处理,进行硬组织切片染色,观察涂层-骨界面的骨整合情况。结果 HA涂层螺钉和钛+HA复合涂层螺钉与周围骨组织结合紧密,骨组织的接触率明显高于普通螺钉和钛涂层螺钉,其中HA涂层螺钉与周围骨组织的接触率最高。结论HA涂层螺钉与周围骨组织的接触率最高,这可以作为生物力学测试中HA涂层螺钉具有较高生物力学稳定性的界面组织学基础。