A study of some properties of a sample of bovine cortical bone using ultrasound

Summary Both collagen fibers and long bone exhibit similar anisotropy in several respects, strongly supporting the concept that the anisotropy of bone has its source in the contained collagen fibers which are parallel to the bone axis in mature adult mammalian bone. Experimental information was obtained for a sample of adult bovine tibia from the midregion of the bone prepared as 22 specimens, 2 mm thick, in three orientations—axial, tangential, and radial—with respect to the measurement of sonic velocity. Thickness, sonic transit time, and weight were obtained for the original wet specimens in 0.15M saline, after dehydration at room temperature, after rehydration, and after demineralization in 0.5M EDTA solution. The average density and volume fractions of water, mineral, and organic components closely matched those reported by Biltz and Pellegrino for bovine bone. The distribution of orientation-dependent properties (velocity, change in velocity, and change in thickness) kept the same pattern in every state, although the intensity of the anisotropy varied. The fractional dimensional changes when samples were dehydrated were greatest in the radial direction and least in the axial, just as for collagen fibers. An almost identical decrease in thickness was observed in magnitude and distribution when the specimens were demineralized. Estimates of the sonic velocity for bone collagen were obtained with the aid of the Lees-Davidson hypothesis. These values often matched the published values for collagen fibers, summarized as follows: -1107-1     

Comparison of the trabecular and cortical tissue moduli from human iliac crests

The purpose of this study was to design a method to produce and test mechanically microspecimens of trabecular and cortical tissue from human iliac crests, and compare their measured moduli. Rectangular beam specimens were prepared on a low-speed diamond blade saw and a miniature milling machine. The final specimen dimensions ranged from approximately 50-200 microns for base and height. The modulus of each specimen was measured using three-point bending tests across a span length of 1.04 mm and performed at a constant rate of displacement. A subset of specimens was recovered for a radiographic estimation of degree of mineralization. The results showed the mean trabecular tissue modulus of all iliac crest specimens to be 3.81 GPa, whereas cortical tissue specimens averaged 4.89 GPa. This was a significant difference according to a two-way analysis of variance that controlled for differences between donors. No strong correlations were found between modulus and mineral density. Future investigations that consider other microstructural characteristics and their contributions to modulus, and specimen size effects, are indicated.     

Heterogeneity of blood flow in tibial cortical bone: an experimental investigation using microspheres

The distribution of tibial blood flow was measured by injecting approximately (600-1000) x 10(3) 15 mu microspheres, labelled with either tin-113 (113Sn) or cobalt-57 (57Co) into femoral arteries of five mature greyhounds. The diaphyseal cortex, stripped of periosteum and devoid of marrow, was sawn into 40 pieces (10 transverse sections x 4 anatomical quarters/section). Relative deposition densities of the 113Sn microspheres in 40 pieces of cortex were found. These values, together with their associated masses, proved, from a statistical point of view, that flow rate heterogeneity was substantial in the diaphysis. In particular, for the diaphyseal cortex, distribution of relative deposition densities (flow rates) in six bones was found to be positively-skewed with a relative dispersion ((SD/mean) x 100) of approximately 40%.     

Pyridoxine deficiency affects biomechanical properties of chick tibial bone

The mechanical integrity of bone is dependent on the bone matrix, which is believed to account for the plastic deformation of the tissue, and the mineral, which is believed to account for the elastic deformation. The validity of this model is shown in this study based on analysis of the bones of vitamin B₆-deficient and vitamin B₆-replete chick bones. In this model, when B₆-deficient and control animals are compared, vitamin B₆ deficiency has no effect on the mineral content or composition of cortical bone as measured by ash weight (63 ± 6 vs. 58 ± 3); mineral to matrix ratio of the FTIR spectra (4.2 ± 0.6 vs. 4.5 ± 0.2), line-broadening analyses of the X-ray diffraction 002 peak (β₀₀₂ = 0.50 ± 0.1 vs. 0.49 ± 0.01), or other features of the infrared spectra. In contrast, collagen was significantly more extractable from vitamin B₆ deficient chick bones (20 ± 2 % of total hydroxyproline extracted vs. 10 ± 3% p ≤ 0.001). The B₆-deficient bones also contained an increased amount of the reducible cross-links DHLNL, dehydro-dihydroxylysinonorleucine, (1.03 ± 0.07 vs. 0.84 ± 0.13 p < 0.001); and a nonsignificant increase in HLNL, dehydrohydroxylysinonorleucine, (0.51 ± 0.03 vs. 0.43 ± 0.03, p ≤ 0.10). There were no significant changes in bone length, bone diameter, or area moment of inertia. In four-point bending, no significant changes in elastic modulus, stiffness, offset yield deflection, or fracture deflection were detected. However, fracture load in the B₆-deficient animals was decreased from 203 ± 35 MPa to 151 ± 23 MPa, p ≤ 0.01, and offset yield load was decreased from 165 ± 9 MPa to 125 ± 14 MPa, p ≤ 0.05. Since earlier histomorphometric studies had demonstrated that the B₆-deficient bones were osteopenic, these data suggest that although proper cortical bone mineralization occurred, the alterations of the collagen resulted in changes to bone mechanical performance.     

骨搬移治疗胫骨骨缺损相关并发症的防治

目的 :探讨骨搬移治疗胫骨骨缺损相关并发症的预防与治疗方法。方法 :2012年1月至2015年6月应用骨搬移技术治疗38例胫骨骨缺损患者,男26例,女12例;年龄36~66岁,平均49.0岁;均为开放性胫骨骨折。38例患者骨缺损长度为4~9.6 cm,平均5.2 cm,术后及时调整力线及搬移速度,患者坚持负重。结果 :38例患者术后均获随访,时间17~36个月,平均24.0个月。19例患者对合端自然愈合,其余18例分别经手风琴技术(10例)、植骨辅助内固定(8例)相应处理后愈合。1例患者因神志不清、肺炎、膝关节脱位、糖尿病、脑瘫后遗症等难以护理,患者家属强烈要求手术截肢,故予以截肢处理。骨搬移时间为4~10个月,平均7.1个月。搬移长度为5~11.6 cm,平均8.0 cm。根据Johner-Wruhs胫骨干骨折疗效评价标准:优11例,良18例,中6例,差3例。除1例截肢外,其余病例均治愈,无感染复发、再骨折等。结论:骨搬移法是治疗胫骨骨缺损的有效方法,但其存在许多并发症是限制其临床应用的主要因素,包括搬移距离过长时长骨力线的偏移(骨外露)、钉道感染、钢针松动、软组织下陷、膝踝关节功能丧失、牵张骨痂不长、对合端接触后骨不愈合等。     

纳米压痕技术观察骨微观力学特性变化的实验研究

目的 探讨骨质疏松皮质骨和松质骨微观力学特性的动态变化.方法 20只10月龄雌性SD大鼠随机分为5组:假手术对照组,去势3月组,去势6月组,去势9月组,去势12月组,每组4只.分别于去势不同时间点,取双侧股骨和腰3、4椎体标本,测量骨密度值.采用纳米压痕技术分别测量各组皮质骨和松质骨的微观硬度和弹性模量.结果 随去势时间的增加,皮质骨和松质骨的硬度和弹性模量均呈递减趋势(P＜0.05).各去势组皮质骨内骨板的弹性模量和硬度均比同组的外骨板高,而皮质骨硬度均高于松质骨,假手术对照组和去势3月组皮质骨的弹性模量高于松质骨,去势6月、9月、12月组松质骨的弹性模量高于皮质骨.结论 骨质疏松症皮质骨和松质骨的微观硬度、弹性模量同步降低,这是导致骨骼力学强度下降的重要因素.     

Quantitative computed tomography estimates of the mechanical properties of human vertebral trabecular bone.

The objective of this study was to report our quantitative computed tomography (QCT) density-mechanical property regressions for trabecular bone for use in biomechanical modelling of the human spine. Cylindrical specimens of human vertebral trabecular bone (from T10 to L4) were cored from 32 cadavers (mean +/- SD age = 70.1 +/- 16.8; 13 females, 19 males) and scanned using QCT. Mechanical tests were conducted using a protocol that minimized end-artifacts over the apparent density range tested (0.09-0.38 g/cm3). To account for the presence of multiple specimens per donor in this data set, donor was treated as a random effect in the regression model. Mean modulus (319 +/- 189 MPa) was higher and mean yield strain (0.78 +/- 0.06%) was lower than typical values reported previously due to minimization of the end-artifact errors. QCT density showed a strong positive correlation with modulus (n = 76) and yield stress (r2 = 0.90-0.95, n = 53, p < 0.001). There was a weak positive linear correlation with yield strain (r2 = 0.58, n = 53, p = 0.07). Prediction errors, incurred when estimating modulus or strength for specimens from a new donor, were 30-36% of the mean values of these properties. Direct QCT density-mechanical property regressions gave more precise predictions of mechanical properties than if physically measured wet apparent density was used as an intermediate variable to predict mechanical properties from QCT density. Use of these QCT density-mechanical property regressions should improve the fidelity of QCT-based biomechanical models of the human spine for whole bone and bone-implant analyses.     

Interfragmentary surface area as an index of comminution severity in cortical bone impact.

A monotonic relationship is expected between energy absorption and fracture surface area generation for brittle solids, based on fracture mechanics principles. It was hypothesized that this relationship is demonstrable in bone, to the point that on a continuous scale, comminuted fractures created with specific levels of energy delivery could be discriminated from one another. Using bovine cortical bone segments in conjunction with digital image analysis of CT fracture data, the surface area freed by controlled impact fracture events was measured. The results demonstrated a statistically significant (p < 0.0001) difference in measured de novo surface area between three specimen groups, over a range of input energies from 0.423 to 0.702 J/g. Local material properties were also incorporated into these measurements via CT Hounsfield intensities. This study confirms that comminution severity of bone fractures can indeed be measured on a continuous scale, based on energy absorption. This lays a foundation for similar assessments in human injuries.     

重组人生长激素对摘除卵巢大鼠皮质骨的影响

目的 探讨重组人生长激素对摘除卵巢大鼠股骨和椎体皮质骨的影响。方法 ６个月龄ＳＤ大鼠４０只,摘除卵巢后３个月开始皮下注射高、低２种剂量生长激素。注射８周后处死,取出双侧股骨和Ｌ２椎体,测定股骨中段骨密度值,观测股骨中段和椎体皮质骨厚度的改变,测定股骨生物力学强度,并与雌激素注射组比较。结果 生长激素显著增加摘除卵巢大鼠股骨中段和腰椎体皮质骨尤其是外层皮质的厚度,股骨中段骨密度值和生物力学强度出显著     

Statistical evidence for the relation between citrate and carbonate in human cortical bone

Summary Bone specimens from the anterior iliac crest were collected post-mortem from 128 subjects whose death had been primarily caused by acute coronary disease or accidents. The cortical bone was separated and used for the following determinations: citrate by an enzymatic method, carbon dioxide by microdiffusion, chloride and phosphorus by spectrophotometry, fluoride by the ion-selective electrode technique, and Ca, Mg, Zn by atomic absorption spectrophotometry. The citrate concentration (±SD) was 10.9±3.1 mg/g (dry weight) and was not age-dependent. A statistically significant negative correlation was obtained between citrate and carbon dioxide, however, which was confirmed by regression analysis. The only statistically significant differences in carbon dioxide and fluoride concentrations between three citrate groups were obtained between the lowest group (3.2–8.7 mg/g) and the highest (13.1–16.8 mg/g). In conclusion an inverse relationship may suggest either an effect of citrate on the binding of carbonate to apatite structures, or that the carbonate concentration is dependent to a slight degree on citrate metabolism.     

异种脱蛋白松质骨作为骨组织工程载体性能研究

目的: 研究探讨异种脱蛋白松质骨作为骨组织工程载体性能。方法: 作者将取材于成年猪和山羊股骨松质骨通过理化方法制作成脱蛋白松质骨载体, 并对载体形态结构、组成成分、载体与种子细胞粘附及生长增殖情况以及生物力学特性进行检测分析。同时将载体材料复合自体骨髓间充质干细胞和骨形态生长因子植入成年山羊横突间进行组织工程化成骨融合, 观察成骨情况, 并通过免疫酶组织染色方法检测异种脱蛋白松质骨的免疫原性。结果: 脱蛋白松质骨具有天然网状孔隙结构, 其无机成分为羟基磷灰石, 有机成分为Ⅰ型胶原。力学性能保存良好,有良好的组织和细胞相容性, 免疫原性检测阴性。异种与同种异体脱蛋白松质骨复合rhBMP 2和MSCs成骨过程的组织形态计量学结果基本相同, 移植材料植入体内后多点成骨, 效果满意。结论: 异种脱蛋白松质骨是一种良好的载体材料。     

The effects of long-term immobilization on the histomorphology of human cortical bone

Summary The cortical bone histomorphometrics, total visible osteon density, and mean osteonal cross-sectional area were determined for the major long bones and sixth ribs of two individuals with neurological deficit. One was a multiple sclerosis patient who had been in a wheelchair for 15 years. The other was a quadriplegic as a result of poliomyelitis. Statistically significant differences in osteon densities occurred only in the case of the quadriplegic. Nevertheless, in that subject, the total visible osteon densities for bones of the right arm were not statistically different from those of their age-matched (control) radii. Medical history records revealed that there had been partial use of this limb. These results support the belief that mechanical stress is an important factor in the maintenance of normal cortical bone remodeling. In addition, since there were subnormal osteon densities and normal mean osteonal cross-sectional areas, immobilization appears to be characterized by reduced activation frequency with a normal amount of bone turnover per BMU.     

Comparison of surface density and volume of human iliac trabecular bone measured directly and by applied stereology

Summary Twenty iliac crest cadaver specimens were obtained from 7 females and 13 males, ages 57–85 years, to empirically test the mathematically derived conversions of linear perimeter to three-dimensional area-volume ratios and to test the Delesse principle for volume. The scaling factor for linear perimeters was measured by coating the specimens with fast green stain. A weight per area coating constant was calculated and directly applied to the weight of coating on bone. External volume was measured by calipers and trabecular volume was measured by displacement. All data were repeated on the same specimens and correlated with standard histomorphometric technique. Our direct and histomorphometric measurements of volume on the same specimens showed almost identical means and were highly correlated (r=0.992,P<0.001). The direct and histomorphometric measures of surface density were also highly correlated (r=0.980,P<0.001). A comparison of values derived from 20 and 60 fields was run on the histomorphometric determinations of volume and surface density. The extremely high correlations for volume (r=0.995,P<0.001) and surface density (r=0.998,P<0.001) suggest that 20 fields are sufficient for these two measurements. The conclusions were that (a) Delesse' principle can be accurately applied to trabecular bone; (b) stereologic measures of bone volume are highly accurate; (c) inter- and intrapatient variation is due largely to sample site variation; (d) the direct measurement of trabecular surface was no different than the histomorphometric one; and (e) the conventional scaling factor of 4/π (1.273) is correct and is nearly identical to the empirically derived factor of 1.199.     

胫骨平台骨折术后感染性骨缺损的分型和治疗策略

目的 探讨胫骨平台骨折术后不同程度感染性骨缺损治疗策略的选择.方法 回顾性分析2014年7月至2018年2月我院收治的45例胫骨平台骨折术后感染性骨缺损病人的临床资料,其中男32例,女13例,年龄为(39.42±12.09)岁(20～66岁).腔洞性骨缺损16例,节段性骨缺损16例,波及关节面的缺损13例.Ⅰ型为胫骨平...     

Some properties of the organic matrix of a bovine cortical bone sample in various media

Summary Dimensional stability of a demineralized bovine cortical bone sample was found in all media whether EDTA, saline or ethanol and water solutions or even 100% ethanol. A 6% volume shrinkage was observed, in strong contrast to the reported swelling for tail tendon fiber collagen. Sonic velocity was strongly dependent on the state and the medium, varying by a factor greater than 2. The medium appears to contribute strongly to the observed velocity suggesting that the Reuss formalism is applicable with the solid collagen skeleton as one component and the liquid in the pores as the second. Sonic anisotropy was noted although the intensity varied. The radial to axial velocity was greatest (0.93) in saline and least in 100% ethanol (0.80) indicating that the rigidity of the tissue influenced the character of sonic propagation. Two sets of intermolecular linkages are inferred. One set, in common with tendon collagen, controls the elastic properties. A second set in bone collagen maintains dimensional stability.     

Treatment of tibial defect and bone nonunion with limb shortening with external fixator and reconstituted bone xenograft

Objective: To explore the effect of external fixator and reconstituted bone xenograft (RBX) in the treatment of tibial bone defect, tibial bone nonunion and congenital pseudarthrosis of the tibia with limb shortening. Methods : Twenty patients ( 13 males and 7 females)with tibial bone defect, tibial bone nonunion or congenital pseudarthrosis of the tibia with limb shortening were treated with external fixation, Two kinds of external fixators were used: a half ring sulcated external fixator used in 13 patients and a combined external fixator in 7 patients.Foot-drop was corrected at the same time with external fixation in 4 patients. The shortened length of the tibia was in the range of 2-9 cm, with an average of 4.8 cm. For bone grafting, RBX was used in 12 patients, autogenous ilium was used in 3 patients and autogenous fibula was implanted as a bone plug into the medullary canal in 1 case,and no bone graft was used in 4 patients. Results: All the 20 patients were followed-up for 8 months to 7 years, averaging 51 months. Satisfactory function of the affected extremities was obtained. All the shortened extremities were lengthened to the expected length. For all the lengthening area and the fracture sites,bone union was obtained at the last. The average healing time of 12 patients treated with RBX was 4.8 months. Conclusions: Both the half ring sulcated external fixator and the combined external fixator have the advantages of small trauma, simple operation, elastic fixation without stress shielding and non-limitation from local soft tissue conditions, and there is satisfactory functional recovery of affected extremities in the treatment of tibial bone defects, tibial bone nonunion and congenital pseudarthrosis of the tibia combined with limb shortening.RBX has good biocompatibility and does not cause immunological rejections. It can also be safely used in treatment of bone nonunion and has reliable effect to promote bone healing.     

Reduction in normalized bone elasticity following long-term bisphosphonate treatment as measured by ultrasound critical angle reflectometry

Using an improved version of ultrasound critical angle reflectometry, the bone quality of cortical and trabecular bone was assessed in vivo by measuring elastic moduli (normalized for bone density) at both principal axes, referred to as the minimum and maximum normalized elasticities. The measurements were made in 30 normal premenopausal women, 30 normal postmenopausal women, 22 untreated postmenopausal women with osteoporosis, 74 postmenopausal women with osteoporosis or osteopenia on bisphosphonate treatment, and 32 patients with renal transplantation (16 women and 16 men) taking steroids. Cortical elasticity was higher than trabecular elasticity; both declined slightly and non-significantly with age in normal women. Among untreated postmenopausal women with osteoporosis, cortical maximum normalized elasticity (E_cmax) remained within 95% prediction intervals of normal women. Among patients on bisphosphonate, E_cmax was low in the majority of patients. E_cmax was significantly more depressed among those taking the drug 3 years than <3 years (22.1% below normal premenopausal women versus 17.2%, P =0.001), and among those with incident non-spinal fractures than without (75.9 vs. 81.5%, P =0.008). E_cmax was independent of bone mineral density at the calcaneus. Most patients with renal transplantation had low E_cmax, with a mean 20.8% below the normal premenopausal mean. Qualitatively similar findings were found with cortical minimum elasticity and with trabecular minimum and maximum elasticities. Thus, the material bone quality of cortical and trabecular bone may be impaired following bisphosphonate treatment, as in renal transplantation on steroids.     

Age-related changes in the density and tensile strength of human femoral cortical bone

Summary In order to ascertain whether the intrinsic strength of human bone changes with age or not, we have determined the ultimate tensile strength and density of strips of femoral cortical bone. These femora were collected from cadavers varying in age from 13 to 97 years. The results show that both density and intrinsic strength of bone increase up to about the fourth decade of life and then decrease with age. However, the rate of decrease of strength is greater than that of density. This indicates that the density of bone is not the sole determining factor of its strength, and that some other factors play an important part.     

Heterogeneity of bone lamellar-level elastic moduli

Advances in our ability to assess fracture risk, predict implant success, and evaluate new therapies for bone metabolic and remodeling disorders depend on our understanding of anatomically specific measures of local tissue mechanical properties near and surrounding bone cells. Using nanoindentation, we have quantified elastic modulus and hardness of human lamellar bone tissue as a function of tissue microstructures and anatomic location. Cortical and trabecular bone specimens were obtained from the femoral neck and diaphysis, distal radius, and fifth lumbar vertebra of ten male subjects (aged 40–85 years). Tissue was tested under moist conditions at room temperature to a maximum depth of 500 nm with a loading rate of 10 nm/sec. Diaphyseal tissue was found to have greater elastic modulus and hardness than metaphyseal tissues for all microstructures, whereas interstitial elastic modulus and hardness did not differ significantly between metaphyses. Trabecular bone varied across locations, with the femoral neck having greater lamellar-level elastic modulus and hardness than the distal radius, which had greater properties than the fifth lumbar vertebra. Osteonal, interstitial, and primary lamellar tissues of compact bone had greater elastic moduli and hardnesses than trabecular bone when comparing within an anatomic location. Only femoral neck interstitial tissue had a greater elastic modulus than its osteonal counterpart, which suggests that microstructural distinctions can vary with anatomical location and may reflect differences in the average tissue age of cortical bone or mineral and collagen organization.     

Vertebral bone mineral density measured laterally by dual-energy X-ray absorptiometry

The bone mineral density (BMD) of lumbar vertebrae in the anteroposterior (AP) view may be overestimated in osteoarthritis or with aortic calcification, which are common in elderly. Furthermore, the risk of spinal crush fracture should be more closely related inversely to the BMD of the vertebral body than to that of the posterior arch. Therefore, we measured BMD of lumbar vertebrae in lateral (LAT) view (L2–L3), using a standard dual-energy X-ray absorptiometer (DEXA), thus eliminating most of the posterior spinal elements. The precision of BMD LAT measurement was determined both in vitro and in healthy volunteers. Then, we compared the capability of BMD LAT and BMD AP scans for monitoring bone loss related to age and for discriminating the BMD of postmenopausal women with nontraumatic vertebral fractures from that of young subjects. In vitro, when a spine phantom was placed in lateral position in the middle of 26 cm of water in order to simulate both soft-tissue thickness and X-ray source remoteness, the coefficient of variation (CV) of six repeated determinations of BMD was 1.0%. In vivo, the CV of paired BMD LAT measurements obtained in 20 healthy volunteers after repositioning was 2.8%. The age-related difference between a peak bone mass group estimated in a group of 27 healthy women aged 20 to 35 years and a group of 50 women aged 60 to 75 years, in whom neither vertebral fracture nor osteoporosis risk factors could be detected, were 21.7% and 37.6% in AP and LAT view, respectively. An arbitrary BMD fracture threshold was defined in AP and LAT views as the 90th percentile of the BMD value of a group of 22 osteoporotic women with vertebral fractures. The distribution of BMD AP and LAT above and below this threshold in 169 consecutively screened women without vertebral fracture was then analysed. In both AP and LAT views, 39.1% and 31.3% had BMD values above and below this threshold, respectively. Of the remaining, 16.0% had a BMD below this threshold only in AP and 13.6% only in LAT view. Thus, if BMD LAT was a better reflection of vertebral body bone mass than BMD AP, and thereby a better predictor of the resistance to crush fracture, our results would suggest that only the use of the standard AP view could under- or overestimate spinal fracture risk in about 30% of women screened for osteoporosis. In conclusion, our results indicate that BMD measurement in lateral view is feasible with a standard DEXA instrument. This mode of scanning, besides overcoming artefacts due to osteoarthritis of the posterior arch and aortic calcifications, appears to provide a greater sensitivity for assessing bone mass loss of the vertebral body than the standard anteroposterior scan.