The effect of centrifugation on the fatigue life of bone cement in the presence of surface irregularities

Reduction of the porosity of bone cement by centrifugation significantly improves the fatigue life of the cement when smooth, waisted specimens are tested. However, bone cement in vivo has surface irregularities at the interdigitation of the cement with the trabecular bone. The effect of centrifugation on the fatigue life of Simplex P in specimens containing surface irregularities was investigated by examining both composite specimens of trabecular bone and bone cement and specimens containing a sharp, circumferential notch. For the specimens with the sharp notch, the bone cement that had been centrifuged lasted significantly longer in fatigue (47,039 +/- 40,277 cycles) than the uncentrifuged specimens (3103 +/- 1950 cycles). Eleven of 15 uncentrifuged specimens broke at the location of a void, rather than the notch. In contrast, when the porosity was reduced by centrifugation, 13 of the 15 specimens broke at the notch. For the specimens that were a composite of bone cement and trabecular bone, the centrifuged specimens had a significant increase in fatigue life compared to the uncentrifuged specimens when tested at both 7 MPA (641,056 +/- 444,131 cycles vs. 237,969 +/- 124,153 cycles) and 15 MPA (8800 +/- 4673 cycles vs. 1534 +/- 719 cycles). Reduction of porosity in bone cement by centrifugation significantly extends its fatigue life even in the presence of trabecular bone or sharp surface notches as used in total joint replacements. These data support the concept that reduction of porosity of bone cement by centrifugation may extend the duration of fixation of the components in cemented total joint arthroplasties.     

椎体成形术中椎体骨密度对骨水泥弥散体积的影响

目的:探讨椎体成形术中椎体骨密度对骨水泥弥散体积的影响。方法:18例胸腰椎压缩骨折患者,术前均行骨折椎体双能X线骨密度仪测定,根据WHO骨质疏松症诊断标准分为骨密度正常组(A组)、骨密度减低组(B组)及骨质疏松组(C组),每组6例,采用经伤椎单侧椎弓根行椎体成形术,术中注入相同状态和批次骨水泥2.5ml,术后采用64排CT扫描椎体,计算骨水泥注射体积及弥散体积。结果:所有患者均顺利完成手术并均成功注2.5ml骨水泥,CT计算骨水泥注射体积:A组2.460±0.116cm3,B组2.450±0.038cm3,C组2.457±0.037cm3;骨水泥在椎体中弥散体积:A组为6.717±1.127cm3,B组为5.650±0.669cm3,C组为4.617±0.542cm3。三组骨水泥弥散体积均大于同组注射体积(P<0.01);三组间骨水泥注射提及比较均无统计学差异(P>0.05)。弥散体积比较均有统计学差异(P<0.05),A组弥散体积最大。结论:椎体成形术中骨水泥弥散体积大于骨水泥注射体积;椎体骨密度与椎体内骨水泥弥散体积密切相关,骨密度越高,弥散体积越大。     

Comparison and optimization of three centrifugation systems for reducing porosity of Simplex P bone cement

Simplex P bone cement was spun for 30, 60, and 120 seconds in three different centrifugation systems (I.E.C. HN-S II, I.E.C. clinical, and Johnson & Johnson) to determine whether differences among the three systems also produce differences in the improvement of the fatigue strength of the cement. The fatigue properties of the cement after centrifugation were also assessed when it was mixed with monomer that had been chilled to 0 degrees C. There were important and statistically significant differences in the fatigue life of Simplex P spun for the same duration in the different centrifuges. Simplex P prepared as recommended by the manufacturer had an average fatigue life of 15,143 cycles in the test system used. Optimum centrifugation among the techniques studied increased the fatigue life nearly fivefold, to the range of 71,000 cycles. Taking into account both the fatigue strength and the viscosity of the cement, the optimum centrifugation system for improving the fatigue life of Simplex P bone cement is the Miller cartridge containing two packs of cement spun in the IEC-HN-S II centrifuge. The authors recommend 30 seconds of centrifugation if the monomer is not chilled prior to mixing and 60 seconds if the monomer is chilled.     

Influence of bone density on the cement fixation of femoral hip resurfacing components

In clinical outcome studies, small component sizes, female gender, femoral shape, focal bone defects, bad bone quality, and biomechanics have been associated with failures of resurfacing arthroplasties. We used a well‐established experimental setup and human bone specimens to analyze the effects of bone density on cement fixation of femoral hip resurfacing components. Thirty‐one fresh frozen femora were prepared for resurfacing using the original instruments. ASR? resurfacing prostheses were implanted after dual‐energy X‐ray densitometer scans. Real‐time measurements of pressure and temperature during implantation, analyses of cement penetration, and measurements of micro motions under torque application were performed. The associations of bone density and measurement data were examined calculating regression lines and multiple correlation coefficients; acceptability was tested with ANOVA. We found significant relations between bone density and micro motion, cement penetration, cement mantle thickness, cement pressure, and interface temperature. Mean bone density of the femora was 0.82 ± 0.13 g/cm², t‐score was ?0.7 ± 1.0, and mean micro motion between bone and femoral resurfacing component was 17.5 ± 9.1 µm/Nm. The regression line between bone density and micro motion was equal to ?56.7 × bone density + 63.8, R = 0.815 (p < 0.001). Bone density scans are most helpful for patient selection in hip resurfacing, and a better bone quality leads to higher initial component stability. A sophisticated cementing technique is recommended to avoid vigorous impaction and incomplete seating, since increasing bone density also results in higher cement pressures, lower cement penetration, lower interface temperatures, and thicker cement mantles. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:986–991, 2010     

新型椎弓根钉骨水泥强化系统的生物力学与骨水泥剂量关系

目的建立骨质疏松模型,研究骨质疏松情况下新型经皮长U形空心椎弓根钉骨水泥强化系统(PMI-NPPS)的生物力学与骨水泥剂量之间的关系。方法取年龄在2.5~3.0岁绵羊腰椎,根据羊腰椎大小定做特定尺寸的羊PMI-NPPS。将40个椎体分成A、B组,B组脱钙4 h,分别进行骨密度测量,统计学分析确认骨质疏松模型建立。制备50个骨质疏松椎体随机分成5组,置入羊PMI-NPPS及骨水泥,按剂量分为0 ml组、0.5 ml组、1.0 ml组、1.5 ml组、2.0 ml组,进行生物力学测试,然后得出骨水泥剂量与Fmax(最大拔出力)的关系。结果 A组骨密度值为(0.875±0.003)g/cm~3、B组骨密度值为(0.631±0.003)g/cm~3,B组骨密度值低于A组,差异有统计学意义(P0.05)。脱钙后椎体骨密度较脱钙前降低27.9%。0 ml组、0.5 ml组、1.0 ml组、1.5 ml组、2.0 ml组的Fmax分别为(372.34±47.96)N、(613.85±30.37)N、(760.64±51.18)N、(896.59±47.97)N、(1 011.59±47.97)N。Pearson相关分析结果提示骨水泥剂量与Fmax呈直线相关,线性回归方程为y=312.5x+418.75(R~2=0.977),且1.5 ml为最理想的骨水泥剂量。结论当骨水泥剂量为0~2 ml时,随着骨水泥剂量的增加,羊PMI-NPPS的Fmax越高,且呈线性相关;当骨水泥剂量为1.5 ml时,羊PMI-NPPS的Fmax可达到正常骨密度时内固定的强度。     

Histological findings of the femoral bone after cement removal in hip revision

Cement removal in hip revision arthroplasty is often a time-consuming procedure, lengthy and tedious. Intraoperative bone damage is one of the more common complications. In the present study, the conventional cement removal method is compared with a new method by means of a histological study concerning potential negative effects to cortical or spongious bone. Histological studies on human cadaver femurs demonstrate no deleterious effects on the endosteal bone when cement was removed with this new device. The ballistically driven chiselling system (OrthoClast) is safe to the bone stock and shows no increased risk of bone damage over the conventional technique with mallet and chisel.     

Profiles of sperm morphology and motility after discontinuous multiple-step Percoll density gradient centrifugation

Summary. Morphology and motility are important parameters for assessing the fertilizing capacity of spermatozoa. This investigation reports a systematic study on the profiles of these parameters after Percoll gradient centrifugation. Spermatozoa from normal human semen were fractionated by discontinuous Percoll gradients (30%, 45%, 75%, 90%). Spermatozoa washed with Earle's balanced salt solution were used as a control. After centrifugation, sperm morphology was evaluated according to strict criteria; motility was assessed by a computer-assisted semen analysis system. The results showed that the percentage of spermatozoa with normal morphology increased, while those with severe morphological defects decreased, as the density of Percoll increased. The percentages of motile spermatozoa and hyperactivated spermatozoa, and the velocity and amplitude of lateral head displacement of the spermatozoa were significantly higher in the 75% and 90% Percoll fractions than that in the 30% and 45% ones, and in the control. These results demonstrated that Percoll density gradient centrifugation enriched spermatozoa in terms of morphology and motility.     

Changes in scaphoid bone density after acute fracture

The radiographic density of the proximal fragments of 16 scaphoid fractures was assessed on scaphoid series radiographs taken at 6 to 12 weeks. In addition, dual energy X-ray absorptiometry measurements of bone mineral density in the distal radius and proximal and distal fracture fragments were performed at 1 to 2 weeks and 6 to 12 weeks. Median reductions of 9% and 10% were observed in bone mineral density in the proximal fracture fragment and the distal radius respectively, but these did not correlate with the radiographic density of the proximal fragment. A greater median reduction in bone mineral density (27%) was observed in the distal fracture fragment and more bone loss occurred at this site when there was an apparent increase in the radiographic density of the proximal fragment (median fall of 0.23 g/cm2 versus 0.14 g/cm2). Thus, apparent increased radiographic density of the proximal fragment may be due to increased bone loss from the distal fragment.     

经皮椎体成形术后患者骨水泥渗漏的影响因素

目的探讨经皮椎体成形术(PVP)术后患者发生骨水泥渗漏的影响因素。方法回顾性分析189例行PVP治疗骨质疏松性椎体压缩性骨折患者的临床资料,根据术后是否出现骨水泥渗漏分为渗漏组(n=89)和非渗漏组(n=100),分析骨质疏松性椎体压缩性骨折患者PVP术后发生骨水泥渗漏的相关因素。结果89例骨水泥渗漏患者中A型渗漏38例(42.70%),B型渗漏26例(29.21%),C型渗漏15例(16.85%),D型渗漏10例(11.24%)。单因素分析结果显示,两组患者性别、年龄、一次性治疗椎体个数和骨折至手术时间比较差异无统计学意义(P>0.05),术前伤椎高度、骨水泥注入量、术前Cobb角、穿刺路径和椎体周壁破坏因素比较差异有统计学意义(P<0.05)。多因素logistic线性回归分析结果显示,术前伤椎高度、骨水泥注入量、术前Cobb角、穿刺路径和椎体周壁破坏等因素是导致PVP术后骨水泥渗漏的独立危险因素。结论术前伤椎高度、骨水泥注入量、术前Cobb角、穿刺路径和椎体周壁破坏等是PVP术后骨水泥渗漏的影响因素。     

Femoral nerve compression after migration of bone cement to the groin after hip arthroplasty

Although often a benign complication of total hip arthroplasty, cement extrusion can cause nerve, vessel, and organ compression. We report the case of a 70-year-old male patient in whom an extruded cement mass migrated anteriorly and compressed the femoral nerve and impinged on the femoral artery producing acute, severe groin pain with neuralgia 9 years postoperatively. Paresthesia of the anterior and medial thigh was found on examination. Radiographic, ultrasound, and computed tomographic studies confirmed a 6 × 1.5-cm mass of bone cement in the right groin compressing the femoral nerve that was removed successfully at surgery. Six months postoperatively, the patient's pain had resolved, but hyperesthesia of the medial thigh remained.     

胸腰椎骨折椎体强化术中骨水泥渗漏率分析

目的分析胸腰椎骨折行经皮椎体成形术(PVP)或经皮椎体后凸成形术(PKP)骨水泥渗漏率。方法对550例骨质疏松性胸腰椎体压缩性骨折(650椎)、爆裂性骨折(61椎)患者施行PVP(201椎)或PKP(510椎)。术后对责任椎常规复查X线片。结果骨水泥渗漏共135椎(18.99%),其中PVP 72椎(10.12%),PKP 63椎(8.86%)。患者均获得随访,时间3~24个月。渗漏类型:椎体周缘型75椎(10.55%),椎间隙型25椎(3.52%),椎管型16椎(2.25%),针道型10椎(1.41%),椎间静脉型9椎(1.26%),无椎间孔渗漏。以L145椎为最多(33.33%)。有3例患者出现胸闷,吸氧后缓解;其余患者均无明显临床症状。所有患者术后疼痛明显减轻。结论虽然椎体强化术术中骨水泥渗漏率较高,但椎管内及椎间孔渗漏率较低,因此渗漏产生明显临床症状者较少。     

Bone marrow repopulation capacity after transplantation of lymphocyte-depleted allogeneic bone marrow using counterflow centrifugation

Bone marrow from six allogeneic HLA-matched and MCL nonreactive siblings was fractionated by means of isopycnic flotation centrifugation and subsequent counterflow centrifugation. The low density fraction (d less than or equal to 1.070 g/ml) obtained by IFC contained 20% of the nucleated cells and more than 90% of the myeloid and erythroid progenitors. The putative stem cell fraction obtained by CC showed a satisfactory recovery (88%) of the CFU-GM and BFU-E and only 3.5% of the original number of T lymphocytes. Bone marrow repopulation capacity was not impaired in comparison with a comparable group of patients. Despite the average high age of this group (29.6 years), only one of the four evaluable patients developed graft-versus-host disease.     

Efficacy of the density gradient centrifugation method in eliminating sperm with aneuploidy

The aim of this study was to evaluate the efficacy of the PureSperm density gradient centrifugation on the selecting sperm with less chromosomal aneuploidy. Semen samples were obtained from 30 infertile men with teratozoospermia and 15 fertile men with normal semen parameters. The frequencies of numerical chromosomes aberrations were simultaneously identified in neat semen and in the different fractions of the density gradient centrifugation from the same samples. Using a triple colour FISH, we show that patients with severe teratozoospermia have a significantly increased frequency of chromosomal abnormalities in their neat semen compared with normozoospermic men (P < 0.001). The mean sperm motility and sperm morphology were improved significantly after semen processing with three layers PureSperm gradient compared with whole semen (P < 0.001). In addition, aneuploidy frequencies were lower in specimens enriched by the gradient centrifugation compared with unprocessed semen. Significant differences were observed in the disomy rates for the autosome and for either sex chromosome between the neat semen and the different PureSperm fractions (P < 0.001). In conclusion, our study shows that semen processing by density gradient centrifugation is very efficient in reducing sperm with aneuploidy and diploidy.     

股骨假体周围骨密度定量测定

目的 通过双能X线骨密度仪测定不同情况下股骨假体周围的骨密度变化情况,了解骨丢失与股骨假体松动的关系。方法 分为骨水泥固定的股骨假体组、非骨水泥固定的股骨假体组、股骨假体松动组共3个组,采用LUNAR DPXL-L型双能X线骨密度仅(Lunar Corp Wisconsin,USA)及Orthopaedies软件,分析时用Gruen’s 7区法。结果 骨水泥固定的股骨假体组骨丢失为15．1%～29．3%,非骨水泥固定的股骨假体组骨丢失为13．2％～27．9%,股骨假体松动组骨丢失为25．4％～43．4%,3组均是股骨近端骨丢失明显．骨丢失主要发生在术后8年以内。结论 骨水泥固定的股骨假体和非骨水泥固定的股骨假体周周骨密度降低一样,假体松动者假体周围骨丢失明显增加。股骨近端2个以上区域骨丢失大于35％或术后8年以后突然出现明显的骨丢失,考虑有股骨假体松动存在的可能性。     

Sustained bone mineral density changes after burn injury

BACKGROUND: Body-composition changes have been observed after burn injury. In particular, several studies have shown that bone mineral density (BMD) in burn patients is decreased when compared to the normal population. Little is known about the frequency, severity, or duration of these changes. The purpose of this study was to describe body-composition changes over time after burn injury. MATERIALS AND METHODS: Twenty-nine burn patients participated in this study. Portable dual-energy X-ray absorptiometry (pDEXA) measuring forearm BMD, fat, and lean mass was obtained as soon as possible after admission and repeated bi-weekly until discharge and, when possible, for 2 years post-injury. The scan showing the greatest change in BMD, fat, or lean mass was compared to the baseline scan for each individual. RESULTS: Although lean and fat mass did not change significantly after injury, BMD decreased significantly. The greatest change in BMD did not occur during the acute burn hospitalization, but rather 131 days after burn injury. Changes in post-burn BMD inversely correlated with % total body surface area (TBSA) and % 3rd-degree TBSA. The magnitude of change was similar between adults and children. CONCLUSIONS: These results confirm earlier studies, suggesting that BMD can be negatively altered post-injury, with the greatest changes occurring after patients are discharged from the hospital. Although the clinical significance of these changes is not known, this study supports the need for long-term musculoskeletal assessments in burn patients and for further research to elucidate the mechanisms of burn-induced body-composition changes.     

Factors influencing vertebral bone density after renal transplantation

To improve our understanding of the mechanisms underlying osteoporosis following renal transplantation, we compared bone mineral density (BMD) in 158 transplant recipients and in 293 patients undergoing maintenance hemodialysis with age- and sex- matched normal controls. Observations in graft recipients were made up to several years following transplantation. Dual-energy X-ray absorptiometry was used to measure BMD. Correlations with clinical variables including serum concentration of parathyroid hormone (PTH) and steroid therapy were evaluated. Lumbar BMD was lower in transplant patients than in dialysis patients at all ages, and continued to decrease with increasing interval posttransplant until the second year after transplantation. Persistent hyperparathyroidism and daily prednisolone dosage were both associated with decreased BMD. Age and creatinine clearance were independent long-term predictors of BMD by multiple regression analysis. Treatment of renal graft recipients with calcium and vitamin D supplements or calcitonin may be indicated in the early months after transplantation.     

Contrast bone cement

The effects of adding 1.0 cc of aqueous methylene blue dye as a visual contrast agent to a standard 40 g pack of acrylic bone cement are determined. These cements are evaluated: Simplex P (Radiopaque), Zimmer Bone Cement, and Zimmer LVC Bone Cement. Seven tests were performed. Leach out is less than 2.0% and was undetectable after day 8. Biocompatibility using a rabbit model shows contrast and white cement to be equivalent. Tension, compression, and 3- and 4-point bending strengths are not significantly altered except for a slight increase in 4-point bending strength for contrast Zimmer (regular) bone cement. Dough, set, and working times are decreased by 30–150 s. The ASTM F451 intrusion standards are met for all three contrast cements. Viscosity increases more rapidly for contrast cement, but remains sufficiently low (less than 100 N-s/m²) early after mixing to allow good penetration into bone. Ease of removal and visualization of contrast cement are shown by revision of cemented femoral total hip components in synthetic and cadaver femurs and by debriding cement particles from a soft tissue background coated with blood. The use of contrast bone cement appears to be both safe and efficacious for use in initial and revision total joint replacements. Because of the decreased working times, its use is recommended only by experienced surgeons.     

Variations in bone mass and bone activity within the mandible

A study of the intermandibular variations in bone mass between the buccal and lingual cortices in the incisive-, premolar-, and molar-region, and between buccal and lingual cortices of the same region of mandibular bodies has been carried out, as well as an estimation of possible differences in the intermandibular variations in bone mass between groups of mandibles with different dentition (dentate, partially dentate, edentulous). The material consisted of 24 autopsy specimens of half mandibles and iliac crests from normal subjects, suddenly dead without previous illness. Microradiograms of ground sections of 100 μm were used. Quantitation of bone mass in per cent within the cortices was done by an electronic point-counting system (Leitz Classimat^(R)). The analysis showed that: 1) the density of lingual cortices seems to be independent of the region, 2) except for old subjects, the density of buccal cortices generally lies on the same level in the incisive- and the premolar-region, while the density in the molar-region is higher and on the same level as lingually, 3) the density of the buccal cortex in the incisive- and premolar-region is lower than the density of the corresponding lingual cortex, and 4) the variations in bone mass within the cortices of mandibular bodies seem to be independent of the state of dention. This does not exclude that extractions of teeth cause changes in bone density.     

椎体强化术后骨水泥弥散分布评价的研究进展

椎体强化术治疗骨质疏松性椎体压缩骨折已在临床上广泛开展,评价手术是否成功,除了与临床疗效有关外,两项重要评价指标是伤椎椎体高度恢复和脊椎后凸Cobb角的矫正程度。但是,近年来研究发现骨水泥在伤椎的弥散分布会影响术后患者疼痛的缓解和脊柱功能的恢复,更有报道与术椎再骨折塌陷和临椎骨折相关,被认为是另外一项不可忽略的重要评价指标。然而由于现研究对骨水泥弥散分布的评价方法不一,尚未形成统一的评价标准。本研究从形态特征、弥散等级、位置分布及是否越过骨折线区域等不同角度,对现有有关椎体强化术后骨水泥弥散分布评价的研究进行系统性综述。综合分析后认为,骨水泥理想的弥散分布是呈现弥散型或混合型形态特征,广泛填充并充分覆盖骨折线区域,双侧均匀连续分布于椎体前柱,并同时接触上下椎板的中间部分。