Tibial implants: biomechanical and histomorphometric studies of hydroxyapatite-coated and uncoated stainless steel and titanium screws in long-term ovariectomized sheep.

This study was designed to evaluate osteointegration of HA-coated and uncoated titanium and stainless steel screws in the cortical bone of long-term (24 months) ovariectomized sheep (OVX group), in comparison with Sham-aged sheep (control group). The screws were tested biomechanically (extraction torque) and histomorphometrically (affinity index: Al) 12 weeks after their implantation in tibial diaphyses. Tibial cortical bone parameters showed significant differences between the groups, showing a reduction of the selected parameters in the OVX group. ANOVA showed significant effects for both material and ovariectomy factors on obtained extraction torque (material: F=159.26, p < 0.0005; ovariectomy: F=20.04, p < 0.0005) and Al data (material: F=8.04, p < 0.001; ovariectomy: F=7, 17, p < 0.05). In both groups the extraction torque for coated screws of both materials was significantly higher than for uncoated screws, and uncoated titanium had a better extraction torque than uncoated stainless steel. In the OVX group, the HA-coated stainless steel and titanium Al data were significantly higher than uncoated Al data. In conclusion, the biomechanical and histomorphological results obtained suggest employing HA-coated screws in the presence of osteopenic cortical bone.     

Biomaterials in spinal fixation. An experimental animal study to improve the performance

Different pedicle screws were biomechanically and morphologically studied and compared through the use of an animal model to determine their efficacy and resistance in spinal fixation. The principal objective was to compare biomechanical and histomorphological aspects of HA-coated screws to uncoated ones. Fourty-eight cylindrical transpedicular self-tapping screws divided into three groups of sixteen each were employed; Group A: stainless steel screws; Group B: titanium screws; Group C: HA-coated titanium screws. The screws were implanted bilaterally and randomly into the L3, L4, and L5 pedicles of eight adult mongrel sheep. The final insertion torque was measured in all the implants. After one and four months, upon euthanization, four samples per group were extracted from the surrounding bone and the screw extraction torque was measured. The remaining samples were examined and processed for histological and histomorphological evaluations. No differences were observed at one month among the extraction torque of the three groups. After four months the only significance between insertion and extraction values was for the HA group, i.e. p=0.001. Comparing the extraction torque values of the three groups after four months of healing, the HA-coated group showed a greater than twofold increase (p<0.0005). No differences were observed at one month among the percentages of bone-implant contact in the three groups. After four months the percentage was significant only for the C group (p<0.0005). At four months a correlation was found between the morphological and the biomechanical data of group C (p<0.0005). The use of hydroxyapatite-coated screws could act as an effective method to improve the bone-implant interface, thus obtaining a strong fixation of the implant independently of the arthrodesis achieved with bone graft.     

Comparative in vivo evaluation of porous and dense duplex titanium and hydroxyapatite coating with high roughnesses in different implantation environments

Ti (PG60) and Ti plus HA (HPG60) dense coatings with ultrahigh roughness (Ra: 74 +/- 8 microm and 53 +/- 18 microm, respectively) were compared to high Ti (Ti60) and Ti plus HA (HT60) high roughened porous coatings (Ra: 40 +/- 7 microm and 36 +/- 3 microm, respectively). Surfaces were implanted in cortical and trabecular bone of young adult (YOUNG), aged (AGED) and estrogen-deficient sheep (OVX) and analyzed by means of histology, histomorphometry and push-out tests 3 months after implantation. A significantly lower value in affinity index (AI) of PG60 when compared to TI60 (p < 0.01) was observed in cortical bone. In trabecular bone, lower values in AI were found in TI60 and PG60 when compared to their HA-coated surfaces (p < 0.0005). Bone ingrowth (BI) of TI60 and PG60 was significantly lower than that of the HA-coated surfaces in trabecular bone (p < 0.05). Significantly lower values in BI in OVX sheep in comparison to YOUNG sheep in both cortical and trabecular bone were observed (p < 0.05). Data showed that high roughness and Ti and HA-coated surfaces are suitable for aged and osteoporotic patients. HA coatings represent the most successful strategy in trabecular bone.     

Biomechanical and histomorphometric investigations on two morphologically differing titanium surfaces with and without fluorohydroxyapatite coating: an experimental study in sheep tibiae

The influence of fluorohydroxyapatite (FHA) coating and surface roughness of Ti6Al4V implants on bone response was investigated. Uncoated and FHA-coated screws with lower (LR and LR+FHA; Ra: 5.7+/-0.2 microm) and higher (HR and HR+FHA; Ra: 21.8+/-0.9 microm) surface roughness, were inserted into the diaphyses of 8 sheep tibiae. Twelve weeks after implantation, extraction torque and bone-to-implant contact were evaluated. The smoothest surfaces showed an improved extraction torque and significant differences were observed between LR and HR (-24.6%, p<0.0005), LR and HR+FHA (-30.7%, p<0.0005), LR+FHA and HR (-17.4%, p<0.005), and LR+FHA and HR+FHA (-24.0%, p<0.005). The bone-to-implant contact data paralleled the biomechanical data: the smoother the surface, the greater the bone-to-implant contact. Significant (p<0.0005) decreases in bone-to-implant contact were observed between LR+FHA and HR (-24.2%), and between LR+FHA and HR+FHA (-29.2%). The current findings suggest that LR surfaces significantly improve the osteointegration rate of implanted cortical screws independently of the FHA coating.     

The ovariectomised sheep as a model for testing biomaterials and prosthetic devices in osteopenic bone: a preliminary study on iliac crest biopsies

A histomorphometric and ultrastructural evaluation on sheep iliac bone was performed. Six sheep were ovariectomised (OVX Group) and 6 were left intact (Sham-aged, Control Group). An iliac crest biopsy was performed randomly in 6 animals at the beginning of the study, then, in all the animals, after 12 and 24 months. A significant decrease in trabecular bone volume, trabecular thickness (p<0.0005) and cell volume (p<0.005) was observed in OVX animals. A modest decrease in trabecular number and osteoid thickness together with an increase in trabecular separation were observed in OVX animals at 12 and 24 months. The osteoid volume showed a significant difference (p<0.05) between the groups. In OVX animals, at 12 months, Scanning Electron Microscopy revealed an enlargement of the trabecular space and a progressive replacement of bone matrix with adipose tissue. These signs were accentuated at 24 months. In conclusion, OVX sheep showed a loss of trabecular bone starting at 12 months after ovariectomy. The developed osteopenic state may be considered as a useful tool when doing research on biomaterial osteointegration.     

Effects of glucocorticoid on BMD, micro-architecture and biomechanics of cancellous and cortical bone mass in OVX rabbits

The incidence of osteoporosis continues to increase with progressively aging populations. The purpose of this study was to detect the effects of glucocorticoid (GC) treatment on bone mineral density (BMD), biomechanical strength and micro-architecture in cancellous and cortical bone in ovariectomized (OVX) rabbits. Twenty adult female New Zealand white rabbits were randomly divided into three groups. The OVX-GC group (n=8) received a bilateral ovariectomy first and then daily GC treatment (methylprednisolone sodium succinate, 1mg/kg/day) for 4 weeks beginning 2 weeks after ovariectomy treatment. The OVX group (n=4) received a bilateral ovariectomy without GC treatment. The sham group (n=8) only received the sham operation. BMD was determined prior to and 6 weeks after the operation in the spine. Six weeks after the operation, the animals were sacrificed, and cancellous bone specimens were harvested from the femoral condyle and lumbar vertebrae. Cortical bone specimens were obtained from the femoral midshaft. The femoral specimens were scanned for apparent BMD. All specimens were tested mechanically and analyzed by microcompute tomography (micro-CT). In cancellous bone, GC treatment resulted in significant decreases in BMD, bone biomechanical strength and micro-architecture parameters in lumbar vertebrae. Similar trends in BMD and micro-architectural changes were also observed in the femoral condyle in the OVX-GC group compared with the sham group. However, there was no significant decline in any parameter in either lumbar vertebrae or femoral condyle in the OVX group. Similarly, no significant difference was found in any parameter in cortical bone among the three groups. Thus, the 4-week GC treatment in OVX rabbits could result in a significant bone loss in cancellous bone but not in cortical bone. This model is comparable to the osteoporosis-related changes in humans. OVX alone was not sufficient to induce osteoporosis.     

Biological assessment of the bone-screw interface after insertion of uncoated and hydroxyapatite-coated pedicular screws in the osteopenic sheep

The sheep seems to be a promising model of osteoporosis and biomaterial osteointegration in osteopenic bone. The long-term ovariectomized sheep model was used for the biological investigation of bone healing around uncoated and hydroxyapatite (HA)-coated pedicle screws in osteopenic bone. Four sheep were ovariectomized and four sheep were sham-operated. Twenty-four months after surgery, the animals were implanted with uncoated and HA-coated stainless steel screws in the lumbar vertebral pedicles. Four months later, bone-to-implant contact, bone ingrowth, and bone hardness were measured around screws. Uncoated stainless steel presented significantly (p < 0.0005) lower bone-to-implant contact in healthy and osteopenic bone compared with HA-coated stainless steel. HA significantly improved bone ingrowth in healthy bone (p < 0.05) compared with uncoated stainless steel. Osteopenia significantly (p < 0.05) reduced the area of bone ingrowth around the screw threads for both types of implants. In the inner thread area, bone microhardness significantly increased (p < 0.05) in HA-coated surface versus uncoated for healthy and osteopenic bone. HA coating significantly enhances bone-to-implant contact also in osteopenic bone in comparison with uncoated stainless steel surfaces. Bone ingrowth and mineralization are ameliorated by the osteoconductive HA coating. However, osteopenia seems to greatly influence bone ingrowth processes around the implanted screws regardless of the characteristics of the material surface.     

多尺度分析骨质疏松大鼠骨微结构变化

目的 多尺度分析骨质疏松大鼠的骨微结构变化。 方法 20只5月龄雌性SD大鼠随机选取12只实施双侧去卵巢(ovariectomy, OVX)手术,术后 8 周形成骨质疏松大鼠模型,另外 8 只作为假手术( SHAM) 对照组。 利用Micro-CT 和 SR-Nano-CT 定量分析骨质疏松大鼠在组织尺度下皮质骨和松质骨以及细胞尺度下骨细胞、骨陷窝小管和细胞外基质的微结构变化。 结果 组织尺度下,OVX 组皮质骨的截面积较 SHAM 组显著增大(P<0. 05),皮质骨骨密度和厚度较 SHAM 组虽有变化,但不显著;OVX 组骨小梁的骨密度、体积分数、厚度和骨小梁数量较 SHAM组显著降低(P<0. 01),骨小梁分离度显著增加(P<0. 01)。 细胞尺度下,OVX 组骨陷窝半轴长较 SHAM 组没有显 著差异,但 OVX 组骨陷窝厚度和骨小管直径较 SHAM 组显著增大(P<0. 05);同时,细胞尺度下 OVX 组皮质骨孔隙率较 SHAM 组显著增大(P<0. 05)。 结论 OVX 大鼠骨在组织和细胞尺度出现不同程度的微结构变化。 其中,组织尺度主要是松质骨丢失,皮质骨变化不大;细胞尺度骨陷窝小管网络孔隙显著增大,将直接影响皮质骨骨密度和强度。 多尺度分析骨质疏松大鼠骨微结构变化对于骨质疏松症的临床诊断及病理分析有潜在的应用价值。     

生长激素对卵巢摘除后大鼠胫骨上段力学性能的保护作用

本实验采用胫骨垂直压缩试验，观察不同剂量重组人生长激素对卵巢摘除后3个月已出现显著骨丢失大鼠（OVX大鼠）胫骨上段力学性能的影响，并和传统的雌激素治疗做对比。结果显示：1．卵巢摘除组大鼠胫骨上段力学性能显著低于假手术对照组。2．中剂量和高剂量生长激素治疗可以显著提高OVX大鼠胫骨的力学性能。3．雌激素和低剂量生长激素治疗对OVX大鼠胫骨上段的力学性能无明显保护作用。生长激素对大鼠胫骨力学性能的保护作用可能和胫骨上段松质骨和皮质骨骨量增加有关。     

The effect of ovariectomy combined with hindlimb unloading and reloading on the long bones of mature Sprague-Dawley rats

OBJECTIVE: To determine the effect of loss of ovarian function and mechanical loading (ie, inactivity) alone or in combination on bone mass and strength. DESIGN: Mature (aged 6 mo) rats were ovariectomized to induce loss of ovarian function and bone. Hindlimb unloading (HLU) was used to determine the effect of mechanical unloading and reloading on bone mass and strength. Bone mass of the femur and tibia was determined using dual-energy x-ray absorptiometry. Femoral and tibial bone strength was determined by a three-point bending test and by a torsion test. RESULTS: Ovariectomy (OVX) alone decreased total bone mineral density (BMD) in the femur (-5.5%, P=0.03) and tibia (-7.3%, P=0.01) compared with that for sham-operated animals. HLU alone for 4 weeks had no significant effect on bone. Together OVX/HLU accentuated BMD loss in the femur (-10.5%, P<0.01) compared with that for sham-operated animals. The femur was more sensitive than the tibia to the combination of OVX/HLU, indicated by the reduction (-5.3%, P<0.05) of total BMD below that achieved by OVX alone. Torsion tests showed that OVX/HLU but not OVX or HLU alone reduced bone strength. There was a correlation between lower femoral total BMD (r2=0.65, P<0.001) and reduced torque strength. Bone loss did not continue during the 2 weeks of reloading. CONCLUSIONS: OVX accompanied by mechanical unloading results in more rapid and severe bone loss than either OVX or unloading alone and therefore is associated with a greater likelihood of osteoporosis.     

降钙素促进骨质疏松骨床中植入体的骨整合

背景：降钙素具有提高骨量、骨质量,降低骨折发生的效果。 目的：评价鲑鱼降钙素对羟基磷灰石植入体骨整合的影响,及其在治疗骨质疏松症同时促进植入体生物学固定的能力。 方法：将SD大鼠随机分为假手术+羟基磷灰石棒组、卵巢切除+羟基磷灰石棒组、卵巢切除+降钙素+羟基磷灰石棒组,后2组建立绝经后骨质疏松动物模型。建模后分别在3组大鼠的胫骨平台处开孔植入多孔羟基磷灰石假体,卵巢切除+降钙素+羟基磷灰石棒组大鼠皮下注射鲑鱼降钙素12周。 结果与结论：卵巢切除后,大鼠的腰椎骨密度降低,而持续皮下注射鲑鱼降钙素后,大鼠的腰椎骨密度逐渐改善。应用降钙素处理后的大鼠,其骨结合率较卵巢切除+羟基磷灰石棒组提高了22.0%(P < 0.05)。结果证实,全身给予鲑鱼降钙素能提高骨质疏松大鼠骨床和植入体周围骨量、促进主体骨-植入体的骨整合。     

Subchondral trabecular structural changes in the proximal tibia in an ovine model of increased bone turnover

Ovariectomized (OVX) sheep are now considered to be useful models for a variety of metabolic bone disorders. The specific aim of this study was to determine the effects of ovariectomy on the structural parameters and material density of the subchondral bone of the ovine tibial plateau as measured by microcomputed tomography (MicroCT). Twenty-three sheep were examined in this study; 10 of the sheep underwent ovariectomy (OVX), and the remainder (n=13) were kept as controls (CON). These animals were then sacrificed at 12 months post-operatively. Three-dimensional analyses were performed of osteochondral samples (15 mm deep) which were obtained from the medial tibial plateau using MicroCT. Bone volume fraction of the subchondral trabecular bone was reduced in the ovariectomized sheep as compared to control animals (0.439 vs. 0.483, P=0.038). Trabeculae were also significantly thinner in the OVX group (0.220 vs. 0.252 mm, P=0.010), with reduced connectivity density (7.947 vs. 11.524 mm(-3) , P=0.014). There was a trend towards lower numbers of individual trabeculae present in the OVX group as compared to controls, but this did not reach significance (2.817 vs. 3.288 mm(-1) , P=0.1). There was also increased trabecular separation in the OVX group, which again fell short of significance (0.426 vs. 0.387 mm, P=0.251). There was no difference in hydroxyapatite concentration (HA) between the two groups (929 vs. 932 mgHA cm(-3) , P=0.687). In conclusion, significant alterations of the trabecular architecture under the tibial plateau were observed following 12 months of oestrogen-deficiency in this ovine model. Despite these marked morphological and structural density differences, the material densities were equal in the two groups.     

Bone anabolic effects of separate and combined therapy with growth hormone and parathyroid hormone on femoral neck in aged ovariectomized osteopenic rats

Previous studies have demonstrated that growth hormone (GH) has a marked anabolic effect on cortical bone and parathyroid hormone (PTH) has been shown to increase cancellous bone and cortical bone markedly in ovariectomized (OVX) rats. Most previous combination therapies used the bone anabolic agent (PTH) and the anti-resorptive agents. In this study, two bone anabolic hormones, GH and PTH, were used in rebuilding bone following loss due to ovariectomy in the femoral neck, which contains both cortical and cancellous bones. Twelve-month-old female F344 rats were divided into five groups: Sham+solvent vehicle, OVX+solvent vehicle, OVX+GH (2.5 mg/kg/day), OVX+PTH (80 microg/kg/day), and OVX+GH (2.5 mg/kg/day)+PTH (80 microg/kg/day). Following surgery, the animals were left for 4 months to become osteopenic before the beginning of hormone therapies. Hormone administrations were given 5 days per week for 2 months and the animals sacrificed. The right femurs were removed and the femoral necks were examined by pQCT densitometry and by histomorphometry. There was a 12.3% decrease in total bone mineral content (BMC) (P<0.01), a 6.2% decrease in total bone mineral density (BMD) (P<0.01), a 12.8% decrease in cortical BMC (P<0.05), a 25.9% decrease in cancellous BMC (P<0.0001), a 20.4% decrease in cancellous BMD (P<0.01), and a 34.2% decrease in cancellous bone volume (BV/TV) (P<0.0001) in vehicle-treated OVX rats. Growth hormone, PTH and GH+PTH treatment increased total BMC of the OVX rats by 14.4% (P<0.01), 23.5% (P<0.0001) and 30.6% (P<0.0001), respectively; increased total BMD by 7.0% (P<0.01), 9% (P<0.001) and 14.8% (P<0.0001), respectively; increased cortical BMC by 15.9% (P<0.05), 25.5% (P<0.001) and 29% (P<0.001), respectively; increased cancellous BMC by 40.9% (P<0.0001), 61.9% (P<0.0001) and 86.8% (P<0.0001), respectively; increased cancellous BMD by 31% (P<0.001), 41.8% (P<0.0001) and 61.8% (P<0.0001), respectively; increased cancellous BV/TV by 30.6% (P<0.05), 76.3% (P<0.0001) and 94.9% (P<0.0001), respectively; and increased trabecular thickness by 26.4% (P<0.05), 41.5% (P<0.001) and 43.2% (P<0.001), respectively, compared to the age-matched vehicle-treated OVX controls. In conclusion, both GH and PTH increased cortical and cancellous bone mass at the osteopenic femoral neck. Using two techniques, it was observed that the effects of PTH were mostly more marked than those of GH. Combined therapy with GH+PTH was more effective in rebuilding cortical bone and cancellous bone than either therapy alone in the aged ovariectomized osteopenic rats, which is in line with our hypothesis.     

The ovariectomized ewe model in the evaluation of biomaterials for prosthetic devices in spinal fixation.

The effect of surgical ovariectomy on cancellous bone was investigated by comparing mechanical properties and microarchitectural characteristics of the lumbar vertebrae in ovariectomized and sham-operated ewes. Eighteen mongrel ewes, 4+/-1 years old, were randomly divided into three groups: 6 animals served as a control group (Baseline), 6 were bilaterally ovariectomized (OVX), and the others were used as a sham-operated group (SHAM). OVX and SHAM ewes were euthanized 24 months after surgery; the L5 vertebrae were processed for mechanical and histomorphometric analyses. Maximum load, maximum strength (p<0.0005) and elastic modulus (p <0.005) decreased by about 28% in the OVX group in comparison with the other groups. In the OVX group, vertebral cancellous bone volume, trabecular thickness and trabecular number decreased by about 32% (p<0.0005), 15% (p=0.001) and 20% (p=0.019), respectively. An overall decrease in the bone turnover rate of the OVX group was registered in terms of bone formation rate (p=0.007) and activation frequency (p<0.0005). The variations observed in cancellous bone mechanics and histomorphometry would suggest the development of an osteopenic state in ewe vertebrae at 24 months. Such findings may be useful for future experimental investigations on biomaterials and prosthetic devices to be implanted in the osteopenic spine.     

Effect of ovariectomy on BMD, micro-architecture and biomechanics of cortical and cancellous bones in a sheep model

Osteoporotic/osteopenia fractures occur most frequently in trabeculae-rich skeletal sites. The purpose of this study was to use a high-resolution micro-computed tomography (micro-CT) and dual energy X-ray absorptionmeter (DEXA) to investigate the changes in micro-architecture and bone mineral density (BMD) in a sheep model resulted from ovariectomy (OVX). Biomechanical tests were performed to evaluate the strength of the trabecular bone. Twenty adult sheeps were randomly divided into three groups: sham group (n=8), group 1 (n=4) and group 2 (n=8). In groups 1 and 2, all sheep were ovariectomized (OVX); in the sham group, the ovaries were located and the oviducts were ligated. In all animals, BMD for lumbar spine was obtained during the surgical procedure. BMD at the spine, femoral neck and femoral condyle was determined 6 months (group 1) and 12 months (group 2) post-OVX. Lumbar spines and femora were obtained and underwent BMD scan, micro-CT analysis. Compressive mechanical properties were determined from biopsies of vertebral bodies and femoral condyles. BMD, micro-architectural parameters and mechanical properties of cancellous bone did not decrease significantly at 6 months post-OVX. Twelve months after OVX, BMD, micro-architectural parameters and mechanical properties decreased significantly. The results of linear regression analyses showed that trabecular thickness (Tb.Th) (r=0.945, R2=0.886) and bone volume fraction (BV/TV) (r=0.783, R2=0.586) had strong (R2>0.5) correlation to compression stress. In OVX sheep, changes in the structural parameters of trabecular bone are comparable to the human situation during osteoporosis was induced. The sheep model presented seems to meet the criteria for an osteopenia model for fracture treatment with respect to morphometric and mechanical properties. But the duration of OVX must be longer than 12 months to ensure the animal model can be established successfully.     

The Effects of Antihypertensive Drugs on Bone Mineral Density in Ovariectomized Mice

The effects of several antihypertensive drugs on bone mineral density (BMD) and micro-architectural changes in ovariectomized (OVX) mice were investigated. Eight-week-old female C57/BL6 mice were used for this study. Three days after ovariectomy, mice were treated intraperitoneally with nifedipine (15 mg/kg), telmisartan (5 mg/kg), enalapril (20 mg/kg), propranolol (1 mg/kg) or hydrochlorothiazide (12.5 mg/kg) for 35 consecutive days. Uterine atrophy of all mice was confirmed to evaluate estrogen deficiency state. BMD and micro-architectural analyses were performed on tibial proximal ends by micro-computed tomography (micro-CT). When OVX mice with uterine atrophy were compared with mice without atrophy, BMD decreased (P < 0.001). There were significant differences in BMD loss between different antihypertensive drugs (P = 0.005). Enalapril and propranolol increased BMD loss in mice with atrophied uteri compared with control mice. By contrast, thiazide increased BMD in mice with uterine atrophy compared with vehicle-treated mice (P = 0.048). Thiazide (P = 0.032) and telmisartan (P = 0.051) reduced bone loss and bone fraction in mice with uterine atrophy compared with the control. Thiazide affects BMD in OVX mice positively. The reduction in bone loss by thiazide and telmisartan suggest that these drugs may benefit menopausal women with hypertension and osteoporosis.     

运动联合福善美对去卵巢大鼠骨密度和神经传导的影响

目的: 观察运动是否可增强福善美对卵巢切除大鼠骨质疏松的治疗作用。方法: 将90只6月龄雌性SD大鼠随机分为假手术组(sham,18只)和卵巢切除模型组(OVX,72只)。大鼠卵巢切除8周后,测定大鼠第4腰椎骨密度(BMD)和血清雌二醇含量。随后,存活的OVX大鼠分为模型组(OVX)、福善美治疗组(OVX+FOX)、运动治疗组(OVX+EX)和福善美与运动联合治疗组(OVX+FOX+EX),分别给予1 mg·kg^-1·d^-1福善美灌胃和(或)跑台运动干预治疗12周后,双能X线骨密度仪测定各组大鼠第4腰椎BMD;肌电图机检测大鼠左侧股神经传导速度(MCV)、运动末端潜伏期(ML)和复合肌肉动作电位(CMAP);ELISA法测定大鼠血清Ⅰ型前胶原羧基端前肽(PICP)及Ⅰ型胶原羧基端交联端肽(ICTP)含量。结果: 卵巢切除大鼠福善美和(或)运动干预治疗12周后,OVX组与sham组相比,BMD显著降低(P<0.05),血清PICP和ICTP明显增高(P<0.05),左侧股神经ML未见明显改变。福善美和运动均可显著提高骨质疏松大鼠BMD,降低ICTP;福善美可显著降低骨质疏松大鼠ICTP,而运动对ICTP无明显影响。运动可明显缩短模型组左侧ML(P<0.05),福善美对ML无显著改善作用。运动与福善美联合对BMD、PICP、ICTP及ML的改善作用较两者单用效果显著(P<0.05);福善美与运动两治疗组间未见明显差异。各组大鼠左侧股神经MCV和CMAP未见明显差异。2×2析因设计的方差分析显示,福善美与运动2种处理方式之间不存在交互作用(P>0.05)。结论: 福善美和运动可能通过抑制破骨细胞的骨吸收而抑制大鼠卵巢切除对骨密度的影响。     

Subchondral osteopenia and accelerated bone remodelling post‐ovariectomy – a possible mechanism for subchondral microfractures in the aetiology of spontaneous osteonecrosis of the knee?

Osteopenia and subchondral microfractures are implicated in the aetiology of spontaneous osteonecrosis of the knee (SPONK). The ovine tibia shows significant alterations of the trabecular architecture within the subchondral bone of the medial tibial plateau post‐ovariectomy (OVX), including reduced trabecular bone volume fraction. We hypothesise that accelerated subchondral bone resorption may also play a role in increasing microfracture risk at this site. Twenty‐two sheep were examined in this study; 10 of the sheep underwent OVX, while the remainder (n = 13) were kept as controls (CON). Five fluorochrome dyes were administered intravenously at 12‐week intervals via the jugular vein to both groups, to label sites of bone turnover. These animals were then killed at 12 months post‐operatively. Bone turnover was significantly increased in the OVX group in both trabecular bone (2.024 vs. 1.047 no. mm^?2; P = 0.05) and within the subchondral bone plate (4.68 vs. 0.69 no. mm^?2; P < 0.001). In addition to the classically described turnover visible along trabecular surfaces, we also found visual evidence of intra‐trabecular osteonal remodelling. In conclusion, this study shows significant alterations in bone turnover in both trabecular bone and within the subchondral bone plate at 1 year post‐OVX. Remodelling of trabecular bone was due to both classically described hemi‐osteonal and intra‐trabecular osteonal remodelling. The presence of both localised osteopenia and accelerated bone remodelling within the medial tibial plateau provide a possible mechanism for subchondral microfractures in the aetiology of SPONK. Further utilisation of the OVX ewe may be useful for further study in this field.     

An investigation of the effects of hydroxyapatite coatings on the fixation strength of cortical screws

Hydroxyapatite (HA) are commonly applied to orthopaedic implants for acceleration of osteointegration and so overcoming the loosening problems such as in cortical screws. Electrophoretic deposition (EPD) of hydroxyapatite was applied for coating of cortical screws in this work. The effects of hydroxyapatite-coated and uncoated cortical screws on insertion and extraction torque were investigated through in vivo experiments. Three groups of screws were undertaken: first group with no coating, second group coated with HA and the third group coated with HA+interlayer, a synthetic calcium silicate compound. Five sheep were operated, and 60 cortical (20 x 3) screws from those of groups were implanted in cortical femurs to observe the effect of HA and interlayer on screws. Results show that as an alternative to plasma spray coating method, the EPD process enables to produce a quick, easy, cheap and uniform adjustable coating layer. Also from biomechanical and SEM examinations, HA coating by EPD method of cortical screws resulted in extremely improved fixation with reduced risk of loosening problem.     

A comparison of estrogen and two different doses of calcitonin in ovariectomized rats

The purpose of this study was to investigate the treatment efficacies of salmon calcitonin (SC) and estrogen in a type-I osteoporotic rat model. Sixty, 3-month-old, female Wistar rats were divided into six groups. The first group was used as the control, and the second a sham, the other four were surgically ovariectomized. 24 hours after the ovariectomy, they were either left untreated (OVX), or treated with an injection of either 17-beta estradiol (E2) 30 mcg/kg/24 hours, low-dose calcitonin (LDC) 10 IU/ kg/48 hours or high-dose calcitonin (HDC) 20 IU/kg/48 hours. 6 weeks later, the bone densities were measured by DEXA, the animals sacrificed and the femurs harvested for histomorphometric evaluation. The bone mineral densities (BMD) of the spine and proximal femur were lower in the OVX group, but only the values of the spine BMD were statistically significant. The BMD of the spine seemed to be preserved with all the treatments. The histomorphometric evaluation revealed that after the OVX the decrease in the trabecular volume was prevented by all the treatments. However, significant changes in the indices of bone formation were not shown. In conclusion, all the treatments prevented bone lost in the ovariectomized rats. Histopathological measurements of bone formation are unlikely to provide any evidence for the effects of these agents on the osteoblastic function. In the animal model of estrogen depletion, our results suggest that the calcitonin provides an important alternative therapy for postmenopausal osteoporosis.