Low‐magnitude whole‐body vibration does not enhance the anabolic skeletal effects of intermittent PTH in adult mice

Whole‐body vibration (WBV) is a low‐magnitude mechanical stimulus that may be anabolic for bone, yet we recently found that WBV did not improve bone properties in adult mice. Because intermittent parathyroid hormone (PTH) enhances the anabolic effects of high‐magnitude skeletal loading, we sought to determine the skeletal effects of WBV in combination with PTH. Seven‐month‐old male BALB/c mice were assigned to six groups (n = 13–14/group) based on magnitude of applied acceleration (0 or 0.3 G) and PTH dose (0, 10, or 40 µg/kg/day). Mice were exposed to WBV (0.3 G, 90 Hz, sine wave) or sham loading (0 G) for 15 min/day, 5 days/week for 8 weeks. Vehicle or hPTH (1–34) was administered prior to each WBV session. Whole‐body bone mineral content increased by ～5% from 0 to 8 weeks in the 40 µg/kg PTH group only, independent of WBV loading. Similarly, PTH treatment increased tibial cortical bone volume by ～5% from 0 to 8 weeks, independent of WBV loading. Neither PTH nor WBV stimulated trabecular bone formation. Consistent with the cortical bone effect, tibias from the 40 µg/kg PTH group had significantly greater ultimate force and energy to failure than tibias in the 0 and 10 µg/kg PTH groups, independent of WBV treatment. In summary, 8 weeks of intermittent PTH treatment increased cortical bone volume and strength in adult male BALB/c mice. Daily exposure to low‐magnitude WBV by itself did not improve skeletal properties and did not enhance the PTH effect. No WBV‐PTH synergy was found in this preclinical study. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:465–472, 2011     

Distinct frequency dependent effects of whole‐body vibration on non‐fractured bone and fracture healing in mice

Low‐magnitude high‐frequency vibration (LMHFV) provokes anabolic effects in non‐fractured bone; however, in fracture healing, inconsistent results were reported and optimum vibration conditions remain unidentified. Here, we investigated frequency dependent effects of LMHFV on fracture healing. Twelve‐week‐old, female C57BL/6 mice received a femur osteotomy stabilized using an external fixator. The mice received whole‐body vibrations (20 min/day) with 0.3g peak‐to‐peak acceleration and a frequency of either 35 or 45 Hz. After 10 and 21 days, the osteotomized femurs and intact bones (contra‐lateral femurs, lumbar spine) were evaluated using bending‐testing, µ‐computed tomography, and histomorphometry. In non‐fractured trabecular bone, vibration with 35 Hz significantly increased the relative amount of bone (+28%) and the trabecular number (+29%), whereas cortical bone was not influenced. LMHFV with 45 Hz failed to provoke anabolic effects in trabecular or cortical bone. Fracture healing was not significantly influenced by whole‐body vibration with 35 Hz, whereas 45 Hz significantly reduced bone formation (?64%) and flexural rigidity (?34%) of the callus. Although the exact mechanisms remain open, our results suggest that small vibration setting changes could considerably influence LMHFV effects on bone formation in remodeling and repair, and even disrupt fracture healing, implicating caution when treating patients with impaired fracture healing. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:1006–1013, 2014.

     

全身振动训练联合正弦交变电磁场对去卵巢骨质疏松大鼠骨密度、骨代谢指标的影响研究

目的探讨全身振动训练联合正弦交变电磁场对去卵巢骨质疏松大鼠骨密度、骨代谢、骨生物力学性能的影响。方法将100只大鼠随机分为切除卵巢组和对照组,分别进行卵巢切除术和假手术,大鼠进行6周恢复,恢复后将造模成功的切除卵巢大鼠随机分为模型组(MO组)、全身振动训练组(W组)、正弦交变电磁场组(S组)、全身振动训练+正弦交变电磁场组(WS组),对照组列为假手术组(SO组),进行为期16周干预,干预结束后对大鼠进行骨密度、骨代谢、骨生物力学性质的检测。结果16周干预完成后,MO组、S组大鼠体质量显著高于SO组、W组、WS组大鼠(P0. 05); W组、WS组、SO组大鼠骨密度指标、血清雌二醇浓度指标明显高于大鼠MO组(P0. 05); SO组大鼠血清雌二醇浓度指标明显高于S组、W组、WS组(P0. 05); M组大鼠血清OC、ALP浓度明显高于SO组、W组、S组、WS组大鼠(P0. 05);尿液DPD/Cre、Ca/Cre、P/Cre浓度方面,M组大鼠明显高于SO组、W组、S组、WS组大鼠(P0. 05)。SO组、W组、S组、WS组大鼠股骨最大载荷和弹性模型明显高于MO组大鼠(P0. 05)。SO组、W组、S组、WS组大鼠股骨断裂载荷组间无明显差异(P0. 05); SO组、W组、S组、WS组大鼠股骨弹性模量明显高于MO组大鼠(P0. 05)。SO组大鼠股骨弹性模量明显高于S组大鼠(P0. 05),但与W组、WS组大鼠没有明显差异(P0. 05)。L4椎体压缩试验,SO组、W组、S组、WS组大鼠股骨最大载荷和弹性模型明显高于MO组大鼠(P0. 05)。SO组大鼠高于S组、W组,差异有统计学意义(P0. 05),但与WS组大鼠没有明显差异(P0. 05)。结论全身振动训练、正弦交变电磁场、全身振动训练联合正弦交变电磁场3种干预方式施用于去卵巢骨质疏松大鼠均能提升骨密度、抑制骨吸收、平衡骨代谢、改善骨骼结构力学和材料力学性能。而全身振动训练联合正弦交变电磁场能的治疗效果优于单纯使用全身振动训练或正弦交变电磁场,在临床应用中有一定推广价值。     

全身振动训练结合雷火灸治疗原发性骨质疏松症腰背痛的临床观察

目的探讨雷火灸干预原发性骨质疏松症腰背痛患者的临床疗效。方法纳入符合诊断标准的原发性骨质疏松症腰背痛患者60例,采用信封法随机分为全身振动训练结合雷火灸组(A组)和全身振动训练组(B组),每组30例。运用视觉模拟评分法(VAS)、Oswestry功能障碍指数问卷表(ODI)、Berg平衡量表(BBS)分别在治疗前、治疗4周结束时及治疗结束后1个月随访时进行评估。结果组间比较,治疗结束时及1个月随访时,VAS及ODI评分有差异(P0.05);BBS评分无差异(P0.05);组内比较:治疗结束时及1个月随访时与治疗前比较,VAS、ODI、BBS等评分均有差异(P0.05);1个月随访与治疗结束时比较VAS、ODI、BBS等评分均无差异(P0.05)。结论全身振动训练结合雷火灸在改善原发性骨质疏松症腰背痛患者VAS和ODI评分方面优于全身振动训练组,但在平衡能力改善方面两组无显著差异。     

Whole body vibration and cerebral palsy: a systematic review

Purpose:The goal of this review is to evaluate the effects of whole body vibration on outcomes in patients with cerebral palsy. The findings in this review may help clinicians make evidence informed decisions on the use of whole body vibration for cerebral palsy.Methods:A systematic search was conducted on April 29, 2014.The following search terms were used to search of several databases: (whole body vibration OR whole-body vibration OR whole body-vibration OR WBV) AND (cerebral palsy). Articles that met the inclusion criteria were assessed using the Scottish intercollegiate guidelines network (SIGN) rating system to assess the methodology and bias of the articles for randomized control trials.Results:The search produced 25 articles, of which 12 duplicates were identified and removed. Another seven articles were not considered since they did not fit the inclusion criteria, leaving a total of five studies for review. Four of the articles analyzed the effects of WBV in children while the other study focused on adults with cerebral palsy. There was one low quality article, four acceptable quality articles and one high quality article when assessed using the SIGN criteria.Conclusions:It appears that whole body vibration has the potential to provide symptomatic relief for patients with cerebral palsy. Whole body vibration may improve spasticity, muscle strength and coordination. There is a lack of research to conclusively determine whether it does alter bone mineral density.     

Whole body vibration induces forepaw and hind paw behavioral sensitivity in the rat

Whole body vibration (WBV) has been linked to neck and back pain, but the biomechanical and physiological mechanisms responsible for its development and maintenance are unknown. A rodent model of WBV was developed in which rats were exposed to different WBV paradigms, either daily for 7 consecutive days (repeated WBV) or two single exposures at Day 0 and 7 (intermittent WBV). Each WBV session lasted for 30 min and was imposed at a frequency of 15 Hz and RMS platform acceleration of 0.56 ± 0.07 g. Changes in the withdrawal response of the forepaw and hind paw were measured, and were used to characterize the onset and maintenance of behavioral sensitivity. Accelerations and displacements of the rat and deformations in the cervical and lumbar spines were measured during WBV to provide mechanical context for the exposures. A decrease in withdrawal threshold was induced at 1 day after the first exposure in both the hind paw and forepaw. Repeated WBV exhibited a sustained reduction in withdrawal threshold in both paws and intermittent WBV induced a sustained response only in the forepaw. Cervical deformations were significantly elevated which may explain the more robust forepaw response. Findings suggest that a WBV exposure leads to behavioral sensitivity. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:1739–1744, 2013     

Aged mice have enhanced endocortical response and normal periosteal response compared with young‐adult mice following 1 week of axial tibial compression

With aging, the skeleton may lose its ability to respond to positive mechanical stimuli. We hypothesized that aged mice are less responsive to loading than young‐adult mice. We subjected aged (22 months) and young‐adult (7 months) BALB/c male mice to daily bouts of axial tibial compression for 1 week and evaluated cortical and trabecular responses using micro–computed tomography (µCT) and dynamic histomorphometry. The right legs of 95 mice were loaded for 60 rest‐inserted cycles per day to 8, 10, or 12 N peak force (generating mid‐diaphyseal strains of 900 to 1900 µε endocortically and 1400 to 3100 µε periosteally). At the mid‐diaphysis, mice from both age groups showed a strong anabolic response on the endocortex (Ec) and periosteum (Ps) [Ec.MS/BS and Ps.MS/BS: loaded (right) versus control (left), p < .05]. Generally, bone formation increased with increasing peak force. At the endocortical surface, contrary to our hypothesis, aged mice had a significantly greater response to loading than young‐adult mice (Ec.MS/BS and Ec.BFR/BS: 22 months versus 7 months, p < .001). Responses at the periosteal surface did not differ between age groups (p > .05). The loading‐induced increase in bone formation resulted in increased cortical area in both age groups (loaded versus control, p < .05). In contrast to the strong cortical response, loading only weakly stimulated trabecular bone formation. Serial (in vivo) µCT examinations at the proximal metaphysis revealed that loading caused a loss of trabecular bone in 7‐month‐old mice, whereas it appeared to prevent bone loss in 22‐month‐old mice. In summary, 1 week of daily tibial compression stimulated a robust endocortical and periosteal bone‐formation response at the mid‐diaphysis in both young‐adult and aged male BALB/c mice. We conclude that aging does not limit the short‐term anabolic response of cortical bone to mechanical stimulation in our animal model. © 2010 American Society for Bone and Mineral Research     

绝经后女性体质量指数、体成分与骨密度的变化特征及关系

目的 探讨绝经后女性年龄、体质量指数（body mass index, BMI）及体成分的变化特征及与骨质疏松症之间的关系。方法 选取广州中医药大学第三附属医院2019年12月–2021年1月门诊收集的98名绝经后女性的体成分及骨密度资料,根据受试者的年龄和BMI分组,比较各年龄组及各BMI组的体成分差别,通过Spearman分析年龄、BMI及体成分对骨质疏松情况的影响,利用多元线性回归研究整体骨密度和整体骨矿含量的影响因素。结果 各个年龄组的整体骨密度（P＜0.001）及整体骨矿含量（P＜0.05）随年龄增加而下降,而各个BMI组的整体骨矿含量（P＜0.05）、整体肌肉质量（P＜0.001）、整体脂肪质量（P＜0.001）随BMI增加而增加。Spearman相关分析显示,随着年龄增加（P=0.005,r=0.281）,骨质疏松程度越严重;而随着BMI（P=0.019,r= – 0.237）、整体骨矿含量（P＜0.001,r= – 0.719）、肌肉质量（P=0.014,r= – 0.249）和脂肪质量（P=0.013,r= – 0.249）的增加,患骨质疏松的程度越轻。多元线性回归分析结果显示,年龄与绝经后女性整体骨密度（P=0.002,B= – 0.004）及整体骨矿含量呈负相关（P=0.000,B= – 0.013）;而整体肌肉质量（P=0.018,B=0.022）和整体脂肪质量（P=0.037,B=0.027）则与绝经后女性整体骨矿含量呈正相关。结论 年龄是绝经后女性患骨质疏松症的危险因素,而BMI、肌肉质量和脂肪质量是保护因素,有助于提高整体骨密度和整体骨矿含量。     

体重对成年女性骨矿含量及其标化的影响研究

目的分析不同体重组人群[小体重组(<45 kg)、标准体重组(45~60 kg)、大体重组(>60 kg)]的骨矿含量结果,探索体重对骨矿含量及其标化的影响。方法纳入290例50~80岁绝经后女性,按体重大小分为大体重组、标准体重组、小体重组。通对不同体重组人群的腰椎L_1~4、股骨的骨矿含量及骨密度进行测量,并对测量结果进行比较分析。同时将年龄、体重作为应变量,腰椎或股骨颈骨矿含量作为自变量,进行多重线性回归分析。结果低体重组的腰椎或股骨颈骨密度T值、骨矿含量均明显低于标准体重组和高体重组人群。随着年龄增长,L_1~4及股骨颈骨矿含量均下降,年龄每升高1岁,L_1~4骨矿含量下降0.364 g、股骨颈骨矿含量下降0.031 g;随着体重增长,L_1~4及股骨颈骨矿含量均升高,体重每增长1 kg,L_1~4骨矿含量升高0.548 g、股骨颈骨矿含量升高0.025 g。结论成年女性的体重与骨矿含量显著正相关,因此,体重是骨矿含量标化的重要指标之一,可以避免骨质疏松的漏误诊。     

Osteoblast‐Targeted Expression of Sfrp4 in Mice Results in Low Bone Mass

Transgenic mice overexpressing Sfrp4 in osteoblasts were established. These mice exhibited low bone mass caused by a decrease in bone formation. Introduction: We recently reported that single nucleotide polymorphisms in the secreted frizzled‐related protein 4 (Sfrp4) gene are responsible for low peak BMD in senescence‐accelerated mouse (SAM) P6. In vitro studies revealed inhibition of osteoblast proliferation by Sfrp4, which is supposed to be mediated by canonical Wnt signaling. Materials and Methods: We examined the expression of Sfrp4 in neonate long bones by in situ hybridization and generated transgenic mice in which Sfrp4 was specifically overexpressed in osteoblasts under the control of a 2.3‐kb Col1a1 osteoblast‐specific promoter. Next, we compared the phenotype of Sfrp4 transgenic (Sfrp4 TG) mice with that of mice in which one allele of β‐catenin was conditionally disrupted in osteoblasts (βChet), and administered lithium chloride (LiCl) to Sfrp4 TG mice. Results: Hemizygous Sfrp4 TG mice exhibited a 30% reduction of trabecular bone mass compared with that in wildtype littermates at 8 wk of age, and histomorphometrical analysis showed decreases in both osteoblast numbers and bone formation rate. βChet mice exhibited a 17% reduction of trabecular bone mass in distal femora caused by an increase in the osteoclast number and a decrease in bone formation rate. Furthermore, LiCl administration rescued the bone phenotype of Sfrp4 TG mice. Conclusions: Expression of Sfrp4 in periosteum and bone tissues suggested the role of Sfrp4 in osteoblasts, and we identified that overexpression of Sfrp4 in osteoblasts suppressed osteoblast proliferation, resulting in a decrease in bone formation in vivo. Partial suppression of β‐catenin/canonical Wnt signaling also impaired bone formation, and activation of the signaling restored low bone mass of Sfrp4 TG mice. Thus, these results indicate that Sfrp4 decreases bone formation at least in part by attenuating canonical Wnt signaling in vivo.     

定量CT研究成年女性腰椎骨密度与椎旁体质成分的相关性

目的探讨不同年龄段成年女性腰椎骨密度(bone mineral density,BMD)与腰3椎体(L3)层面体质成分的相关性。方法将496名成年女性按年龄分为青年组(≤44岁)、中年组(45～59岁)、老年组(≥60岁),计算体质量指数(body mass index,BMI),采用定量CT(quantitative computed tomography,QCT)测量L1～3椎体BMD及L3椎体中心层面周围各体质成分含量,包括BMI、椎体周围脂肪含量(FM)、瘦组织含量(LM)、脂肪与瘦组织比值(F/L)、骨量与瘦组织比值(B/L)、腹部总脂肪(TAT)、内脏脂肪(VAT)、皮下脂肪(SAT)。依据BMD分为骨量正常组(≥120 mg/cm~3)、骨量减少组(80～120 mg/cm~3)和骨质疏松(≤80 mg/cm~3,OP)组。通过单因素方差分析不同年龄组BMI、BMD及各体质成分的组间差异。利用线性相关分析BMD与各体质成分的相关性。结果研究对象平均年龄(50.9±12.5)岁(25～82岁)。BMI、BMD、LM、SAT值在老年组低于中、青年组,组间差异有统计学意义(P0.01),FM在老年组高于中、青年组(P0.01)。VAT随年龄增加逐渐减低,组间差异无统计学意义(P=0.955)。BMD与年龄、FM呈负相关,与BMI、LM、SAT呈正相关,与VAT呈较弱正相关。在不同BMD组中,BMI、LM、SAT在骨质疏松组中最低,组间差异有统计学意义(P0.01),FM在骨质疏松组中最高(P0.01),而VAT在不同BMD组间差异无统计学意义(P=0.701)。结论女性腰椎周围肌肉含量、脂肪浸润程度、腹部皮下及内脏脂肪与腰椎BMD存在相关性,其中BMI、LM、SAT与BMD呈正相关,而FM与BMD呈负相关。     

Regional osteoporosis due to osteoclast activation as a trigger for the pain‐like behaviors in tail‐suspended mice

Pathological conditions with refractory skeletal pain are often characterized by regional osteoporotic changes such as transient osteoporosis of the hip, regional migratory osteoporosis, or complex regional pain syndrome (CRPS). Our previous study demonstrated that the acidic microenvironment created by osteoclast activation under high bone turnover conditions induced pain‐like behaviors in ovariectomized mice through the stimulation of acid‐sensing nociceptors. The aim of the present study was to examine whether regional transient osteoporotic changes are related to pain‐like behaviors in the hind limb using tail‐suspended model mice. The hind limbs of tail‐suspended mice were unloaded for 2 weeks, during which time the mice revealed significant regional osteoporotic changes in their hind limbs accompanied by osteoclast activation. In addition, these changes were significantly recovered by the resumption of weight bearing on the hind limbs for 4 weeks. Consistent with the pathological changes in the hind limbs, pain‐like behaviors in the mice were induced by tail suspension and recovered by the resumption of weight bearing. Moreover, treatment with bisphosphonate significantly prevented the triggering of the regional osteoporosis and pain‐like behaviors, and antagonists of the acid‐sensing nociceptors, such as transient receptor potential channel vanilloid subfamily member 1 and acid‐sensing ion channels, significantly improved the pain‐like behaviors in the tail‐suspended mice. We, therefore, believe that regional transient osteoporosis due to osteoclast activation might be a trigger for the pain‐like behaviors in tail‐suspended model mice. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1226–1236, 2017.

     

External and internal bone micro‐architecture in normal and Kienböck's lunates: A whole‐bone micro‐computed tomography study

Kienböck's disease is idiopathic osteonecrosis of the lunate, leading to its fracture and collapse. This study compares internal and external bone micro‐architecture of normal and fractured lunates (Kienböck's), by using high‐resolution three‐dimensional (3D) micro‐computed tomography (micro‐CT) on the whole bone of the two lunate types, and histology. Fractured Kienböck‐diseased lunates were obtained from patients undergoing proximal‐row‐carpectomy, while normal cadaveric lunates served as controls. 3D‐micro‐CT‐imaging of control lunates revealed an encircling cortex surrounding trabecular bone. Trabeculae were arranged in a radial pattern, spanning from the distal to the proximal subchondral plate. Kienböck's lunates exhibited clear fracture lines, with fragmented bone, both proximally and distally, in areas the radially‐patterned trabeculae and enveloping cortex were absent, producing height loss. In trabecular bone, Kienböck's lunates revealed increased bone volume fraction, trabecular thickness and number, and decreased trabecular separation and structure model index. Histologically, Kienböck's lunates revealed osteonecrosis, as well as remodeling fronts with osteoblasts and osteoid surrounding bone marrow. Whole‐bone high‐resolution 3D examination of normal and Kienböck's diseased lunates contributes to a better understanding of micro‐architectural changes occurring in the pathology. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:826–833, 2014.     

Age‐related spontaneous lumbar intervertebral disc degeneration in a mouse model

The pathogenesis of intervertebral disc degeneration is unclear, but it is a major cause of several spinal diseases. Animal models have historically provided an appropriate benchmark for understanding the human spine. However, there is little information about when intervertebral disc degeneration begins in the mouse or regarding the relationship between magnetic resonance imaging and histological findings. The aim for this study was to obtain information about age‐related spontaneous intervertebral disc degeneration in the mouse lumbar spine using magnetic resonance imaging and a histological score regarding when the intervertebral disc degeneration started and how rapidly it progressed, as well as how our histological score detected the degeneration. The magnetic resonance imaging index yielded a moderate correlation with our Age‐related model score. The Pfirrmann grade and magnetic resonance imaging index had moderate correlations with age. However, our Age‐related model score had a high correlation with age. Intervertebral disc level was not a significant variable for the severity of disc degeneration. Both Pfirrmann grade and the Age‐related model score were higher in the ≥14‐month‐old group than in the 6‐month‐old group. The present results indicated that mild but significant intervertebral disc degeneration occurred in 14‐month‐old mice, and the degree of degeneration progressed slowly, reaching a moderate to severe condition for 22‐month‐old mice. At least a 14‐month follow‐up is mandatory for evaluating spontaneous age‐related mouse intervertebral disc degeneration. The histological classification score can precisely detect the gradual progression of age‐related spontaneous intervertebral disc degeneration in the mouse lumbar spine, and is appropriate for evaluating it. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:224–232, 2018.     

身体成分对绝经后女性骨密度和骨骼肌量的影响

目的 基于双能X线骨密度仪测量的身体成分分析,探讨影响绝经后女性骨密度和骨骼肌量的共同因素,为绝经后骨质疏松和肌少症的协同防治提供思路。方法 纳入2015年1月至2020年10月在中山大学附属第一医院进行身体成分分析的171例绝经后女性,根据全身骨密度和相对骨骼肌肉指数(relative skeletal muscle index,RSMI)分为正常组(T值≥-1且RSMI＞5.45 kg/m2)、肌少组(T值≥-1且RSMI≤5.45 kg/m2)、骨量异常组(T值＜-1且RSMI＞5.45 kg/m2)和肌少/骨量异常组(T值＜-1且RSMI≤5.45 kg/m2)。采用单因素方差分析比较4组一般资料和身体成分差异,Pearson相关分析研究身体成分与骨密度和RSMI的相关性,多元线性回归分析探索影响骨密度和RSMI的共同因素。结果 4组在体脂率(percent body fat,PBF)、脂肪量(fat mass,FM)、脂肪指数(fat mass index,FMI)、瘦组织(lean mass,LM)、瘦组织指数(lean mass index,LMI)、骨矿盐含量(bone mineral content,BMC)、Android/Gynoid区域脂肪比率和休止代谢率(resting metabolic rate,RMR)的整体比较中差异均有统计学意义(P＜0.05)。调整混杂因素后,PBF、FM、FMI与骨密度和RSMI呈不同程度负相关,LM、LMI、BMC、RMR与骨密度和RSMI呈正相关。多元线性回归显示高PBF、低LM和低BMC是骨密度和RSMI的共同危险因素。结论 绝经后女性骨密度与骨骼肌量变化密切相关,针对影响二者的共同危险因素采取干预措施可能有利于绝经后骨质疏松和肌少症的协同防治。     

Consistency of low bone density across bone sites in SAMP6 laboratory mice

The development of bone densitometry has made it clear that there are discrepancies in bone density at various measurement sites in a given individual. This study examined the consistency of bone density measurements across various sites in a strain of laboratory mouse (senescence-accelerated mouse; SAM). A systemic evaluation of the bone density was performed by dual-energy X-ray absorptiometry (DXA) on SAMP6 (P6) mice, a strain with low peak bone density, as measured by microphotodensitometry of the femoral bones, whereas the SAMP2 (P2) and SAMR1 (R1) strains have high peak bone density. We modified Jilkas method to more comprehensively measure the whole body and additional regions of interest (ROIs; head, right foreleg, left foreleg, right hindleg, left hindleg, spine, and tail). The age-related changes in the total (whole-body) BMD showed a common pattern among the strains studied, and the peak value was seen at 4 months old. P6 showed the lowest peak BMD. A detailed comparison of the bone density between P6 and P2 at the age of 4 months revealed significantly lower regional BMD values for P6 in all seven ROIs. The strain difference in BMD could not be attributed to a difference in size. In conclusion, P6 mice showed low bone density not only in their femurs but also in the subregions and over their entire body. This strain can be potentially useful in the investigation of the genetic basis of senile osteoporosis.     

Low-magnitude high-frequency loading via whole body vibration enhances bone-implant osseointegration in ovariectomized rats

Osseointegration is vital to avoid long‐time implants loosening after implantation surgery. This study investigated the effect of low‐magnitude high‐frequency (LMHF) loading via whole body vibration on bone‐implant osseointegration in osteoporotic rats, and a comparison was made between LMHF vibration and alendronate on their effects. Thirty rats were ovariectomized to induce osteoporosis, and then treated with LMHF vibration (VIB) or alendronate (ALN) or a control treatment (OVX). Another 10 rats underwent sham operation to establish Sham control group. Prior to treatment, hydroxyapatite (HA)‐coated titanium implants were inserted into proximal tibiae bilaterally. Both LMHF vibration and alendronate treatment lasted for 8 weeks. Histomorphometrical assess showed that both group VIB, ALN and Sham significantly increased bone‐to‐implant contact and peri‐implant bone fraction (p < 0.05) when compared with group OVX. Nevertheless the bone‐to‐implant contact and peri‐implant bone fraction of group VIB were inferior to group ALN and Sham (p < 0.05). Biomechanical tests also revealed similar results in maximum push out force and interfacial shear strength. Accordingly, it is concluded that LMHF loading via whole body vibration enhances bone‐to‐implant osseointegration in ovariectomized rats, but its effectiveness is weaker than alendronate. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 30:733–739, 2012