Comparison of bone screw holding strength in healthy bovine and osteoporotic human cancellous bone

Pushout tests were carried out on two different diameter, self-tapping, cancellous bone screws (4 mm and 6.4 mm) inserted in bovine cancellous bone sections taken perpendicular and at 45 degrees to the long axis of the bone. Comparison was made with the same type of screws inserted into sections taken from osteoporotic and/or osteoarthritic human femoral heads. The results showed no significant difference in the holding strength of different diameter screws in bovine bone sections of given orientation but significant differences when the trabecular orientation of the section was changed. By comparison, the holding strengths of the same screws in diseased femoral heads were found to be both significantly different from each other and significantly lower than for the same screws inserted in healthy bovine bone. The screw diameter, trabecular orientation, mineral content and the health of the bone all need to be considered in order to optimise the holding strength of the screws in cancellous bone.     

钛质松质骨螺钉内固定置入治疗Hoffa骨折16例

2001-01/2005-06河南省洛阳正骨医院采用膝关节前正中切口髌旁入路松质骨螺钉固定治疗16例Hoffa骨折,术中直视下复位骨折,根据骨块大小及骨折线的走行方向,应用三四枚钛合金与骨折面垂直前后位固定.要求钉尾尽量位于股骨髁前侧关节面近端,如必须经过关节面,钉尾应沉于软骨下.螺纹应过骨折线,位于后髁骨块内.钉尖不能穿过后髁关节面.16例患者均获随访,随访时间6个月～3年,骨折均愈合,平均愈合时间3.7个月,无骨坏死发生.按Hohl膝关节功能评分标准评定疗效,优13例,良3例.结果提示Hoffa骨折只要得到及时的诊断,采用适宜的手术入路及良好的骨折复位、固定技术,完全可以避免或减少骨坏死、创伤性关节炎的发生,获得膝关节功能的良好恢复.     

Variations in non-locking screw insertion conditions generate unpredictable changes to achieved fixation tightness and stripping rates

BackgroundScrews are the most commonly inserted orthopaedic implants. However, several variables related to screw insertion and tightening have not been evaluated. This study aimed firstly to assess the effect of insertion variables on screw tightness, secondly to improve methodologies used by researchers when testing screw insertion techniques and thirdly to assess for any learning or fatigue effects when inserting screws.MethodsTwo surgeons tightened a total of 2280 non-locking, 3.5 mm cortical screws, with 120 screws inserted to what they felt to be optimum tightness whilst varying each of the following factors: different screwdrivers for measuring torque, screwdriver orientation, gloves usage, dominant/non-dominant hand usage, awareness to the applied torque (blinded, unblinded and re-blinded), four bone densities and seven cortical thicknesses. Screws were tightened to failure to determine stripping torque, which was used to calculate screw tightness – ratio between stopping and stripping torque.FindingsScrew tightness increased with glove usage, being blinded to the applied torque and with denser artificial bone and with thinner cortices. Considering all the insertions performed, the two surgeons stopped tightening screws at difference values of tightness ((77% versus 66% (p < 0.001)). A learning effect was observed with some parameters including sterile gloves usage and non-dominant hand application.InterpretationDifferent insertion conditions frequently changed screw tightness for both surgeons. Given the influence of screw tightness on fixation stability, the variables investigated within this study should be carefully reported and controlled when performing biomechanical testing alongside practicing screw insertion under different conditions during surgical training.     

Non-setting,injectable biomaterials containing particulate hydroxyapatite can increase primary stability of bone screws in cancellous bone

BackgroundFracture fixation in weak bone is still a clinical challenge. Screw augmentation was shown to successfully increase their primary stability. The currently used calcium phosphate or polymeric bone cements, however, present important drawbacks such as induced toxicity and/or impaired bone neo-formation. A new approach to enhance bone screw primary stability without affecting bone formation is the use of non-setting, calcium phosphate loaded soft materials as the augmentation material.MethodsTwo types of biomaterials (non-crosslinked hyaluronic acid as viscous fluid and agar as hydrogel) were loaded with 40 wt/vol% of hydroxyapatite particles and characterized. The screw augmentation effect of all materials was evaluated through pull-out tests in bovine cancellous bone and compared to the non-augmented situation (control). The bone mineral density of each test sample was measured with μCT scans and was used to normalize the pull-out strength.FindingsBoth materials loaded with hydroxyapatite increased the normalized pull-out strength of the screws compared to control samples and particle-free materials. This counter-intuitive augmentation effect increased with decreasing bone mineral density and was independent from the type of the soft materials used.InterpretationWe were able to demonstrate that non-setting, injectable biomaterials loaded with ceramic particles can significantly enhance the primary stability of bone screws. This material combination opens the unique possibility to achieve a screw augmentation effect without impairing or even potentially favoring the bone formation in proximity to the screw. This effect would be particularly advantageous for the treatment of osteoporotic bone fractures requiring a stabilization with bone screws.     

Bone marrow influences quantitative ultrasound measurements in human cancellous bone

Quantitative ultrasound (QUS) transmission and backscatter measurements were made in 46 human cancellous bone specimens from the calcaneus. All QUS measurements were made at 35 degrees C, initially with marrow filling the pores and then repeated after substituting water for marrow. Bone mineral density (BMD) was determined using x-ray absorptiometry. Marrow significantly decreased ultrasound (US) velocity, but increased attenuation, attenuation slope and backscatter (p < 0.001 for all) compared to the water-saturated state. The impact of marrow on QUS measurements was greater at lower BMD values (p < 0.05), and was greater in women than in men (p < 0.05). QUS measurements in marrow-saturated specimens correlated less strongly with BMD than did corresponding measurements in water-saturated specimens (p < 0.05), consistent with interspecimen marrow heterogeneity. These data indicate that the potential impact of marrow should be considered when interpreting clinical QUS measurements. Understanding and exploiting these effects could lead to novel approaches for ultrasonic characterisation of both bone and marrow.     

Influence of pilot hole diameter in cancellous screw fixation in a reduced density animal bone model

BackgroundScrew fixation in osteoporotic bone is clinically challenging. Screw failure rates are growing due to an increasing prevalence of osteoporosis. To address this, biomechanical models are needed to recreate the bone clinically encountered alongside the development of new operative techniques. The first aim of this study was to test whether the use of a smaller than recommended pilot-hole diameter improved pull-out strength for cancellous screws, with the second aim to create a model of low-density porcine bone for biomechanical testing.MethodsThirty porcine tibiae were cut into transverse metaphyseal sections of 20 mm thickness. Bone density was altered using 0.15 M Hydrochloric acid, and measured and pre- and post-demineralisation using HRμCT. Seventy-two screw areas were randomised to either 2.5 mm or 1.5 mm pilot holes and to either be normal or reduced density. Maximum axial pull-out strength was measured.FindingsDemineralisation reduced bone density by 12% (p < 0.0001) and 11% (p < 0.0001) for 2.5 mm and 1.5 mm pilot hole diameters respectively. Pull-out strength reduced by 50% (p = 0.0001) and 44% (p < 0.0001) following demineralisation for both 2.5 mm and 1.5 mm pilot hole diameters. Pull-out strength increased by 51% (p = 0.0008) when inserting screws into 1.5 mm pilot holes in low density bone, and by 28% (p = 0.027) in normal bone.InterpretationPorcine bone can be demineralised to model low density cancellous bone. This novel model showed that pullout force is significantly reduced in lower density screw holes, but that this reduction can be mitigated by reducing pilot hole diameter for cancellous screws.     

超声实时监视在宫腔疑难手术中的应用

目的探讨超声在宫腔疑难取环术及宫腔残留组织清除术中的作用.方法超声监视引导下行26例疑难取环术及71例宫腔残留物钳刮手术.结果26例疑难取环术及70例宫腔残留组织清除术均一次性完成手术,采用本法仅1例宫腔憩室手术失败.结论超声可清晰显示宫内环或宫内残留组织确切位置,在宫腔疑难取环术及宫腔残留组织清除术中实时动态观察和指导手术全过程,有效减少和避免并发症的发生,在计划生育手术中具有重要的实用价值.     

Determination of the role of the cancellous bone in generation of screw holding power at metaphysis.

OBJECTIVE: To determine whether cancellous bone at metaphysis plays a significant role in generation of holding power of the cancellous screw. DESIGN: Maximal holding power of the cancellous screw at distal metaphysis of the femur with and without cancellous bone inside was determined by applying a load to push out the screw. BACKGROUND: Generation of screw holding power from the cancellous bone can arise by a mechanism of compression of cancellous bone between screw threads when a screw is inserted by non-tapping technique. Metaphysis has intermediate amount of cancellous and cortical bone when compared with diaphysis and intercondyle of a long bone. METHODS: Eight pairs of fresh cadaveric femurs were used. One femur of a pair was removed of cancellous bone at the distal metaphysis; cancellous bone of the other was preserved. A full thread cancellous screw was inserted into the distal femoral metaphysis. An axial load was applied at the screw tip to push out the screw by using a universal testing machine. RESULT: Mean push-out force of the screw at distal femoral metaphysis without cancellous bone inside was 1824.76 N and stiffness was 746.76 N/mm. Mean push-out force of the screw at distal femoral metaphysis with preservation of cancellous bone was 2015.86 N and stiffiness was 853. 09 N/mm. The statistical analysis of both groups showed no significant differences. CONCLUSIONS: This study confirmed that cancellous bone at metaphysis plays no significant role in generation of holding power of the cancellous screw. RELEVANCE: Because metaphyseal cancellous bone plays no role in generation of screw holding power, only a well-inserted cancellous screw into bone cortices can achieve good screw holding power at metaphysis of a long bone.     

Bone healing using a bi-phasic ceramic bone substitute demonstrated in human vertebroplasty and with histology in a rabbit cancellous bone defect model

A non-exothermic material that demonstrates clinical pain relief comparable to polymethylacrylate (PMMA) for vertebroplasty and promotes bone healing is desirable. The purpose of this investigation is to demonstrate clinical pain score improvement and bone healing following vertebroplasty with a novel bi-phasic ceramic cement. Twenty patients were prospectively treated for compression fractures in a single center in the USA with the injectable bi-phasic ceramic bone substitute. Statistical comparison of pain scores was made during a 12 month follow-up retrospectively against a matched cohort of patients treated with PMMA vertebroplasty by the same neuroradiologist (HPH) in the same setting. The bone remodeling material was also evaluated with histology in a New Zealand white rabbit model. The bi-phasic material demonstrated a pre-operative mean VAS score of 8.5 (± 1.6) with a significant post-operative pain relief mean VAS score of 1.8 (± 2.5) after one week, which was maintained throughout the 12 month follow-up period. These data are in line with the pain scores for the PMMA treated cohort. CT scans six and 12 months after surgery with the bi-phasic cement showed healing of the osteoporotic fractures. In the rabbit model, histology with the study material showed evidence of incorporation, new bone growth and bone healing in a cancellous bone defect. Both the clinical results and the histologic evidence of bone healing and new bone growth support the application of this new bioinjectable material as an alternative to the use of PMMA for vertebroplasty.     

Prediction of frequency-dependent ultrasonic backscatter in cancellous bone using statistical weak scattering model

The goal of this study was to propose a model for the ultrasonic frequency-dependent backscatter coefficient in cancellous bone. This model allows us to address the inverse problem and to predict the mean trabecular thickness. A weak scattering model is used and the backscatter coefficient is expressed in terms of an autocorrelation function of the medium. Different autocorrelation functions (Gaussian, exponential and densely populated media) were used to compute the backscatter coefficient and comparison is made with experimental data for 19 specimens and for frequency ranging from 0.4 to 1.2 MHz. For each specimen, a nonlinear regression was performed and the mean trabecular thickness is estimated. Experimental data and theoretical predictions were averaged over the 19 specimens. A good agreement between experimental data and predictions was found for both the magnitude and the frequency-dependence of the backscatter coefficient. We also found a good agreement between the experimental mean trabecular thickness (Tb. Th = 130 +/- 6.5 micro m) derived from the analysis of bone 3-D microarchitecture using high-resolution microtomography and theoretical predictions (d(Gauss) = 140 +/- 10 micro m, d(exponential) = 153 +/- 12.5 micro m and d(dense) = 138 +/- 6.5 micro m). These results open interesting prospects for the estimation of the mean trabecular thickness from in vivo measurements.     

实时超声引导鼻骨骨折闭合复位

目的 探讨实时超声引导鼻骨骨折闭合复位的临床价值。方法 将60例临床确诊的鼻骨骨折患者随机分为试验组和对照组,每组30例。对2组患者均在全麻下行鼻骨骨折闭合复位治疗,其中试验组为实时超声引导下行骨折闭合复位,对照组为传统视诊、触诊下骨折闭合复位。复位后,基于鼻部CT平扫图像采用3分法评价复位效果。对比分析2组间骨折二次复位率、患者住院时间及术后CT评分的差异。结果 试验组骨折二次复位率为0,对照组为13.33%（4/30）,2组间差异有统计学意义（χ²=4.286,P=0.038）。试验组患者中位住院时间为4天,对照组为5天,试验组较对照组明显缩短（Z=-5.024,P<0.001）。试验组术后CT评分为3分、2分及1分者分别为19例、11例和0,对照组分别为11例、16例和3例,试验组较对照组复位效果更优（χ²=6.059,P=0.048）。结论 实时超声引导鼻骨骨折闭合复位精准、可靠,可减少骨折二次复位风险并避免X线辐射,且可有效缩短患者住院时间,提高医患双方满意度。     

空心拉力螺钉加镍钛聚髌器置入内固定重建骨折髌骨的生物力学条件

背景：目前临床治疗髌骨骨折的内固定方法众多,但各有优缺点。内固定方法的选择是否合适,将直接影响髌骨骨折愈合时间及膝关节功能恢复。目的：评估空心拉力螺钉加镍钛聚髌器置入内固定治疗髌骨骨折后的生物力学重建效果。方法：回顾性分析2011年1月至2012年1月复旦大学附属金山医院骨科收治的新鲜髌骨骨折患者27例,横形骨折13例,粉碎骨折11例,上或下极骨折3例。采用空心拉力螺钉加镍钛聚髌器置入内固定,不需石膏外固定,内固定后自第2天开始行股四头肌主动收缩训练,内固定后1周开始床上屈伸膝关节锻炼。采用BSstman髌骨骨折疗效评定标准进行膝关节功能评价。结果与结论：27例患者均获随访,随访时间4—14个月。切口均获I期愈合,无内固定断裂或脱落、切口感染、皮肤坏死等并发症。骨折平均愈合时间为8．5周,无延迟愈合发生。根据BOstman评分标准,平均分为27．9分,其中优22例（81％）、良4例（15％）、差1例（4％）,优良率为96％。结果显示,在空心拉力螺钉的基础上辅以镍钛聚髌器固定兼具传统各种内固定方法之优点,同时避免了其不足之处。     

Demineralized bone matrix and human cancellous bone enhance fixation of porous‐coated titanium implants in sheep

Allogenic bone graft has been considered the gold standard in connection with bone graft material in revision joint arthroplasty. However, the lack of osteogenic potential and the risk of disease transmission are clinical challenges. The use of osteoinductive materials, such as demineralized bone matrix (DBM), alone or in combination with allograft or commercially available human cancellous bone (CB), may replace allografts, as they have the capability of inducing new bone and improving implant fixation through enhancing bone ongrowth. The purpose of this study was to investigate the effect of DBM alone, DBM with CB, or allograft on the fixation of porous‐coated titanium implants. DBM100 and CB produced from human tissue were included. Both materials are commercially available. DBM granules are placed in pure DBM and do not contain any other carrier. Titanium alloy implants, 10 mm long × 10 mm diameter, were inserted bilaterally into the femoral condyles of eight skeletally mature sheep. Thus, four implants with a concentric gap of 2 mm were implanted in each sheep. The gap was filled with: (a) DBM; (b) DBM:CB at a ratio of 1:3; (c) DBM:allograft at a ratio of 1:3; or (d) allograft (gold standard), respectively. A standardized surgical procedure was used. At sacrifice 6 weeks after implantation, both distal femurs were harvested. The implant fixation was evaluated by mechanical push‐out testing to test shear mechanical properties between implant and the host bone and by histomorphometry. Non‐parametric tests were applied; p < 0.05 was considered significant. Mechanical fixation showed that the strengths among the DBM/CB, DBM/allograft and allograft groups were not statistically different. The strength of the DBM group was 0.01 MPa, which was statistical significantly lower than the other three groups (p < 0.05). Histomorphometry results showed that the bone ongrowth in the DBM group was statistically significantly lower than the other three groups, while the volume fraction of new bone showed no significant difference among all the groups. Our data revealed that adding DBM to CB or to allograft resulted in comparable mechanical properties relative to the gold standard, allograft. We found inferior early effects of DBM alone on the fixation of porous‐coated titanium implant in this animal model, while the long‐term effects have to be investigated. The combination of DBM with CB, which can be used off the shelf, may represent an alternative to allograft. A cost–benefit analysis is necessary before application in clinical trial. Copyright © 2013 John Wiley & Sons, Ltd.     

松质骨中超声背散射信号的分析

在理论和实验上,分析了松质骨中超声背散射系数与频率的关系.牛胫骨和人尸体跟骨松质骨的背散射实验及理论分析结果表明,背散射系数随入射频率的增加而非线性的增加.一般,整个背散射系数曲线可以分成三段不同斜率的曲线.在用超声评价松质骨状况时,背散射信号具有重要作用,其背散射系数(BSC)可用于评价松质骨状况.     

Biomechanical effects of insertion location and bone cement augmentation on the anchoring strength of iliac screw

Background

Iliac screw loosening has been a clinical problem in the lumbo-pelvic reconstruction. Although iliac screws are commonly inserted into either upper or lower iliac column, the biomechanical effects of the two fixations and their revision techniques with bone cement remain undetermined. The purpose of this study was to compare the anchoring strengths of the upper and lower iliac screws with and without cement augmentation.

Methods

5 pairs of formalin fixed cadaveric ilia with the bone mineral density values ranged from 0.82 to 0.97 g/cm² were adopted in this study. Using screws with 70-mm length and 7.5-mm diameter, 2 conventional iliac screw fixations and their revision techniques with cement augmentation were sequentially established and tested on the same ilium as follows: upper screw, upper cement screw, lower screw, and lower cement screw. Following 2000 cyclic compressive loading of − 300 N to −100 N to the screw on a material testing machine, the maximum pull-out strengths were measured and analyzed.

Findings

The average pull-out strengths of upper, upper cement, lower, and lower cement screws were 964 N, 1462 N, 1537 N, and 1964 N, respectively. The lower screw showed significantly higher pull-out strength than the upper one (P = 0.008). The cement augmentation notably increased the pull-out strengths of both upper and lower screws. The positive correlation between pull-out strength and bone mineral density value was obtained for the 4 fixations.

Interpretation

The lower iliac screw technique should be the preferred choice in lumbo-pelvic stabilization surgery; cement augmentation may serve as a useful salvage technique for iliac screw loosening; preoperative evaluation of bone quality is crucial for predicting fixation strength of iliac screw.     

仿松质骨的胶原/纳米羟基磷灰石人工骨治疗免股骨头坏死的动物实验

背景:自体松质骨因具有促进骨再生的3大要素:良好的骨引导性、骨诱导件和骨细胞,目前仍然足骨缺损修复的最佳移植材料.目的:观察自主研发的仿松质骨纳米人工骨修复股骨头坏死的效果.设计、时间及地点:随机对照动物实验,于2007-05/08在广东省医学实验动物中心完成.材料:新西兰大白兔10只,体质量1.5～2.0 kg,用注入液氮的方法制备股骨头坏死模型.方法:10只大白兔随机分为2组,每组5只.实验组:骨坏死处植入HA/CO纳米人工骨,对照组:坏死处不加任何植入物.主要观察指标:在植入材料即刻及之后的7,14 d摄X射线观察、大体积及组织学观察评判骨坏死的发展及治愈情况.结果:实验组骨坏死破抑制并被修复,所钻骨孔因松质骨和皮质骨的再生而完全愈合,纳米人工骨被逐渐降解吸收;而空白对照组骨坏死逐渐恶化,所钻骨孔处无任何骨组织再生.结论:该纳米人工骨不仅能替代自体骨作为移植物,而且还具有抑制骨坏死发展的功能,可望成为临床治疗Ⅱ期及较早期股骨头坏死的替代疗法.     

Real time monitoring of lipoplex molar mass, size and density.

Time-resolved multiangle laser light scattering (TR-MALLS) is used to monitor the temporal variation of DNA/cationic liposome lipoplex molar masses and geometric sizes throughout the complexation process. The measured molar masses and geometric sizes are in turn used to estimate lipoplex density. The DNA/cationic lipid charge ratio is found to be the primary factor governing lipoplex formation kinetics and the final lipoplex molar mass, geometric size and density. Charge ratios near unity lead to a growing kinetic regime in which initially formed primary lipoplexes undergo further aggregation eventually forming large molar mass lipoplexes of high density, while charge ratios very far from unity yield low molar mass lipoplexes of lower density. It is also noted that solvent composition can play a significant role in the lipoplex formation process with lipoplexes formed in ion-containing media being larger and denser than those formed in dextrose solution.     

去抗原异种松质骨作为骨组织工程载体的可行性

目的：对自行研制的去抗原异种松质骨材料与骨髓基质细胞复合培养进行生物相容性进行评价，为骨组织工程中生物材料的选择提供实验依据。 方法：实验于2004—05／2005—05在教育部省部共建新疆民族与地方高发病重点实验室完成。①取新生小牛股骨下端松质骨，锯成15mm&;#215;5mm&;#215;5mm大小骨块，经1：1氯仿，HCl，H2O2和PBS＋NaOH＋NaM混合液等物理化学处理．制成去抗原异种松质骨载体。①选用清洁级健康3月龄新西兰大白兔2只，抽取骨髓．通过密度梯度离心和贴壁筛选法分离纯化骨髓基质细胞，将传代至第3代细胞接种于24孔培养板内，实验分为2组：实验组每孔加入5mm&;#215;5mm&;#215;3mm去抗原异种松质骨材料一块。对照组单纯接种细胞，每组4孔。于4，8d后进行处理．用于观察及检测。③通过扫描电镜、MTT测试法、考马斯亮蓝和碱性磷酸酶活性检测法，观察去抗原异种松质骨材料对细胞生长、增殖及功能表达的影响。 结果：①骨髓基质细胞生长情况：倒置相差显微镜观察，骨髓基质细胞能在去抗原异种松质骨材料上黏附、增殖，细胞形态良好。②骨髓基质细胞在去抗原异种松质骨材料生长结果：扫描电镜观察，骨髓基质细胞在去抗原异种松质骨材料生长良好。③实验组于接种后4和8d骨髓基质细胞增殖、蛋白质含量和碱性磷酸酶活性（A值）分别为0．50&;#177;0．03．0．78&;#177;0．10．0．44&;#177;0．02和0．73&;#177;0．14，1．21&;#177;0．07，0．59&;#177;0．03，与对照组（0．51&;#177;0．02．0．80&;#177;0．15，0．45&;#177;0．01；0．70&;#177;0．11．1．20&;#177;0．04，0．60&;#177;0．02）比较，差异不明显（P〉0．05）。 结论：去抗原异种松质骨对骨髓基质细胞体外增殖和蛋白质合成无不良影响，对骨髓基质细胞的生长增殖无明显的干扰作用，对骨髓基质细胞向成骨细胞转化无影响，即去抗原异种松质骨材料无细胞毒性；同时具有良好的细胞相容性，可用作骨组织工程的支架材料。