羟基磷灰石材料结合牵拉成骨技术修复骨缺损的实验研究

 目的 探讨羟基磷灰石（hydroxyapatite/tri-calcium phosphase,HA/TCP）材料结合牵拉成骨技术是否能减少治疗骨缺损所需的时间并促进骨的矿化过程。方法 将36只健康雄性新西兰大白兔（20~24周,体重2.2~2.8 kg）随机分为3组,每组12只。于左胫腓关节下方做1 cm的胫骨缺损。A组：将骨缺损两端靠拢,外固定架加压固定。B组：将1 cm长的HA/TCP材料填入1 cm的骨缺损中,外固定架加压固定。C组：将骨缺损两端拉近至间距0.5 cm,将0.5 cm长的HA/TCP材料填入剩余的0.5 cm骨缺损中,外固定架加压固定。除B组外,A、C组均于术后7 d开始延长胫骨,A组延长10 d,C组延长5 d。在术后即刻、12、17、27、37 d用“C”型臂X线机观察各组新生骨的矿化过程。所有动物于术后37 d处死,取新生骨样本测量骨矿物质含量（BMC）和组织矿物质含量（TMC）,行胫骨扭转实验及组织病理学分析。结果 C组BMC为（454.44±89.98） mg和TMC为（454.40±89.97） mg显著高于A、B两组。C组新生骨的最大扭矩、新生骨的成熟度均明显高于A、B两组,骨的矿化和重塑也较快。C组在观察期总共37 d内骨愈合良好,但A、B两组在37 d内并未达到骨愈合。结论 在兔胫骨缺损延长模型中,与单一疗法相比,联合应用羟基磷灰石材料和牵拉成骨技术可减少治疗时间并促进骨的矿化。     

Tricalcium-phosphate and hydroxyapatite bone-graft extender for use in impaction grafting revision surgery. An in vitro study on human femora

Impacted morsellised allografts have been used successfully to address the problem of poor bone stock in revision surgery. However, there are concerns about the transmission of pathogens, the high cost and the shortage of supply of donor bone. Bone-graft extenders, such as tricalcium phosphate (TCP) and hydroxyapatite (HA), have been developed to minimise the use of donor bone. In a human cadaver model we have evaluated the surgical and mechanical feasibility of a TCP/HA bone-graft extender during impaction grafting revision surgery. A TCP/HA allograft mix increased the risk of producing a fissure in the femur during the impaction procedure, but provided a higher initial mechanical stability when compared with bone graft alone. The implications of the use of this type of graft extender in impaction grafting revision surgery are discussed.     

Current management

Background and purpose Allografts are often used during revision hip replacement surgery for stabilization of the implant. Resorption of the allograft may exceed new bone formation, and instability of the prosthesis can develop. We investigated whether strontium could regulate the imbalance of fast resorption of allograft and slower formation of new bone, because it is both an anabolic and an anticatabolic agent.

Method Strontium was added to the implant interface environment by doping a hydroxyapatite bone graft extender. 10 dogs each received 2 experimental titanium implants. The implants were inserted within a 2.7-mm concentric gap in cancellous bone. The gap was filled with 50% (v/v) allograft mixed with 50% bone graft extender. The extender either had 5% strontium doping (SrHA) or was undoped (HA). After 4 weeks, osseointegration and mechanical fixation were evaluated by histomorphometry and by push-out test.

Results SrHA bone graft extender induced a 1.2-fold increase in volume of new bone, a 1.2-fold increase in allograft remaining in the gap, and a 1.4-fold increase in surface area of the bone graft extender material in contact with new bone compared to HA bone graft extender. All these increases were statistically significant.

SrHA bone graft extender did not significantly improve ongrowth of bone onto the implants or improve any of the mechanical push-out parameters compared to HA bone graft extender.

Interpretation Doping of the HA bone graft extender with 5% strontium increased gap healing, preserved more of the allograft in the gap, and increased the ongrowth of bone onto the bone graft extender material, but did not improve mechanical fixation.     

Site Specificity of Bone Architecture Between the Distal Radius and Distal Tibia in Children and Adolescents: An HR-pQCT Study

High-resolution quantitative computerized tomography permits evaluation of site specific differences in bone architecture. The purpose of this study was to compare bone architecture between distal radius and distal tibia. We present bone architecture at the distal radius and distal tibia in 151 male and 172 female participants, as follows: total bone area (mm²), total bone density (mg HA/cm³), trabecular bone density (mg HA/cm³), cortical bone density (mg HA/cm³), cortical thickness (μm), trabecular number (1/mm), trabecular thickness (μm), and trabecular separation (μm). We evaluated differences in and correlations between bone variables (absolute values) across sites. We calculated individual z scores and used regression to assess discordance between sites. In pubertal and postpubertal male and female participants, absolute values of total bone area, cortical bone density, cortical thickness, and trabecular thickness were significantly lower at the radius compared with the tibia (P < 0.01). Absolute values for trabecular bone density were significantly lower at the radius compared with the tibia in postpubertal male and female participants (P < 0.01). Absolute values for trabecular separation was significantly lower at the radius compared with the tibia in pubertal female participants (P < 0.01). Bone architecture was moderately to highly correlated between sites (r = 0.34–0.85). There was discordance between z scores at the radius and tibia within male participants (pubertal R ² between 36 and 64%; postpubertal R ² between 22 and 77%) and female participants (pubertal R ² between 10 and 44%; postpubertal R ² between 25 and 62%). In conclusion, it is vital to evaluate bone architecture at the specific skeletal site of interest.     

骨髓基质成骨细胞复合支架材料构建组织工程性肌骨瓣的实验研究

目的探索用羟基磷灰石/磷酸三钙(HA/TCP)的支架材料与成骨细胞复合构成组织工程性肌骨瓣修复骨缺损的能力。方法自2004年12月至2005年5月,于新西兰大耳白兔髂后上棘抽取骨髓基质干细胞并诱导分化为成骨细胞,然后与HA/TCP结合,共培养2周,通过相差显微镜、扫描电镜观察体外细胞生长情况,最后将复合物埋入兔的背阔肌下构成组织工程性肌骨瓣。术后6周进行大体解剖观察,HE染色,研究组织工程性肌骨瓣的生长情况。结果扫描电镜显示支架材料表面和孔隙内均有成骨细胞生长,有良好的增殖活动性和稳定细胞表型,材料中心区未见细胞生长,植入体内6周后取材见内植物有新骨形成,多位于内植物表面,可见成骨细胞、骨细胞、髓腔样结构、板层样骨基质等正常骨组织结构。结论骨髓来源的成骨细胞可用作骨组织工程的种子细胞,此种组织工程性肌骨瓣生长良好,可成功构建组织工程化骨。     

The initial stability of cemented acetabular cups can be augmented by mixing morsellized bone grafts with tricalciumphosphate/hydroxyapatite particles in bone impaction grafting

Tricalciumphosphate (TCP) and hydroxyapatite (HA) have been suggested as bone graft substitutes in a wide range of applications. In this study, the initial stability of cemented acetabular cups was determined after reconstructing a combined cavitary and segmental defect in a realistic acetabular revision surgery model. The defects were reconstructed with mixes of TCP/HA particles and human bone grafts using the bone impaction grafting technique. In comparison with defect reconstruction with human bone grafts only, cup translation and tilt decreased by 27% when mixes of bone grafts and porous TCP/HA particles were used and by 55% when mixing the bone grafts with solid TCP/HA particles. Increasing the TCP/HA ratio within the mix significantly decreased cup translation. From a biomechanical perspective, mixes of TCP/HA particles and bone grafts are an attractive alternative for morsellized bone grafts when using the bone impaction grafting technique in the reconstruction of large defects of the acetabulum.     

Impaction bone grafting with hydroxyapatite: increased femoral component stability in experiments using Sawbones

Background Substantial bone loss and bone defects increase the amount of allografting required in hip revision surgery. Thus, the use of a synthetic material to limit the amount of allograft tissue required for impaction grafting is desirable. We evaluated the potential of hydroxyapatite (HA) mixtures to provide initial mechanical stability to a polished tapered femoral stem.

Material and methods We determined the initial stability of a polished tapered femoral stem after reconstructing a cavitary femoral bone defect by impaction bone grafting with cement in Sawbones composite femurs. Three types of graft material were tested for their ability to improve initial rotational stability. The graft materials investigated were pure allograft, a mixture of 50% allograft and 50% hydroxyapatite (HA), and pure HA.

Results We found a statistically significant difference between the three groups as regards torsional micromotion and failure load.

Interpretation Our findings suggest that reconstruction of femoral bone defects with pure HA or a mixture of allograft and HA provides adequate initial stability for femoral revision arthroplasty using impaction grafting.     

The influence of hydroxyapatite granules on the healing of a segmental defect filled with autologous bone marrow.

Hydroxyapatite(HA) ceramics are frequently used as a bone graft substitutes for the filling of bony defects. The addition of autologous bone marrow to HA ceramics does improve defect healing. There is conflicting evidence in the literature whether autologous bone marrow transplantation alone is as effective as the combination of HA ceramics and bone marrow combined. It was the purpose of this study to identify the role of additional HA ceramic granules on the healing of a sheep tibia segmental defect filled with autologous bone marrow. After permission of the local animal rights committee was obtained, a 3 cm segmental defect in the midshaft of 31 adult sheep was stabilized with an unreamed tibia nail. The animals were divided into 4 groups according to the mode of defect filling: HA plus autologous bone marrow (HA + MAR) (n = 8), autologous bone marrow (MAR) (n = 9), empty defect (DEF) (n = 6), cancellous bone graft (CAN) (n = 8). After three months follow up animals were sacrificed and analysed for the key parameters of union and maximum torque at failure. One nonunion was present in each of the HA + MAR, MAR, and CAN groups. Four of the six animals in the DEF group developed a nonunion. Maximum torque at failure was reported as percentage of the intact contralateral tibia: HA + MAR 39% +/- 24%, MAR 26% +/- 17%, DEF 22% +/- 13%, CAN 41% +/- 20%. The difference between the groups was statistically significant, but appeared to be relevant. We conclude from our data, that HA ceramics do improve healing of a segmental defect in the sheep tibia filled with autologous bone marrow. The results of this combination are comparable to cancellous autograft.     

Biomechanical analysis of tibial strength after harvest of unicortical tibial grafts from two different sites

BACKGROUND: Use of tibial strut grafts has several potential advantages over other donor sites and would be ideal as a harvest site for bone grafts if there are minimal or no resulting risks to tibial stability. METHODS: Ten matched-pair cadaver tibiae were randomized to have a 1.5 x 4.0 cm cortical graft harvested from the tibial crest or 1 cm posterior to the tibial crest. Both locations were 6 cm distal to the tibial plateau. The grafts were removed using a high-speed oscillating saw, and each end of the tibia was mounted for testing and loaded onto a servohydraulic test frame. The samples were axially loaded with 720 N (162 lbs) of force, and an external rotational torque was applied at 5 degrees per second to failure. Failure torque for each tibia was recorded. A paired Student's t-test was used to determine whether any observed differences in failure torques were significant. RESULTS: The torque to failure range for on-crest grafts was 11.65 to 81.76 Nm (average, 44.53 Nm; SD, 22.82 Nm). The torque to failure range for the tibiae with the graft 1 cm off-crest was 13.30 to 70.45 Nm (average, 41.64 Nm; SD, 17.83 Nm). All fractures were spiral, included the distalmost anterior corner of the donor site, and extended distally. There was no significant difference in torque to failure between the two donor sites (p = 0.22). The grafts varied consistently in quality. CONCLUSION: Considering that there was no statistically significant difference in torque to failure between the two groups of tibiae, the site for tibial bone graft can be selected based on the shape of the cortical graft necessary for each specific surgery.     

Allograft in the treatment of benign cystic lesions of bone

Summary Seventeen patients with benign cystic osseous lesions were treated by curettage and grafting using allogenic decalcified bone. Human bones were partially decalcified using 0.6N HCl and preserved in 90% ethanol in a deep freezer at -16°C. The cystic lesions were: 5 cases of fibrous dysplasia, 4 aneurysmal bone cysts, 3 simple bone cysts, 2 giant-cell tumours, 1 chondromyxoid fibroma, 1 non-ossifying fibroma and 1 fibrous cortical defect. The bones involved were: femur, tibia, humerus, fibula and calcaneum. Infection was a complication in three patients. In two of these it did not interfere with healing, but in one it persisted for more than 1 year with partial resorption of the graft. The time to adequate incorporation of the graft varied from 6 to 9 months in children and 9 to 15 months in adults. The overall response compares favourably with that to allograft from more sophisticated bone banks.     

Impaction bone grafting with hydroxyapatite

Background Substantial bone loss and bone defects increase the amount of allografting required in hip revision surgery. Thus, the use of a synthetic material to limit the amount of allograft tissue required for impaction grafting is desirable. We evaluated the potential of hydroxyapatite (HA) mixtures to provide initial mechanical stability to a polished tapered femoral stem.

Material and methods We determined the initial stability of a polished tapered femoral stem after reconstructing a cavitary femoral bone defect by impaction bone grafting with cement in Sawbones composite femurs. Three types of graft material were tested for their ability to improve initial rotational stability. The graft materials investigated were pure allograft, a mixture of 50% allograft and 50% hydroxyapatite (HA), and pure HA.

Results We found a statistically significant difference between the three groups as regards torsional micromotion and failure load.

Interpretation Our findings suggest that reconstruction of femoral bone defects with pure HA or a mixture of allograft and HA provides adequate initial stability for femoral revision arthroplasty using impaction grafting.     

骨膜瓣复合开窗异体骨移植修复大段骨缺损

目的探讨带血管薄层皮质骨-骨膜瓣嵌入开窗的异体骨修复大段骨缺损的效果。方法将兔胫骨去抗原后制备异体骨标本,制作大段骨缺损动物模型,以带血管薄层皮质骨-骨膜瓣复合开窗的异体骨进行修复。术后观察骨缺损的X线影像,对移植物及其周围软组织行组织学和免疫组织化学观察。结果实验组骨缺损骨痂形成和改造塑形,新生血管长入骨缺损处,新骨形成和骨单位成熟较对照组早。结论以带血管薄层皮质骨-骨膜瓣嵌入开窗的异体骨修复大段骨缺损的手术方法优于以骨膜瓣直接包裹异体骨,缩短骨缺损修复的时间。     

A preclinical study of stem subsidence and graft incorporation after femoral impaction grafting using porous hydroxyapatite as a bone graft extender

This preclinical in vivo screening study compared bone graft incorporation and stem subsidence in cemented hemiarthroplasty after femoral impaction bone grafting with either morselized allograft bone (n = 5, control group) or a 1:1 mix of allograft and porous hydroxyapatite ceramics (HA) granules (n = 5, HA group). At 14 weeks, there was excellent bone graft incorporation by bone, and the stems were well fixed in both groups. The median subsidence at the cement-bone interface, measured using radiostereometric analysis, was 0.14 and 0.93 mm in the control and HA groups, respectively. The comparable histologic results between groups and good stem fixation in this study support the conduct of a larger scale investigation of the use of porous HA in femoral impaction bone grafting at revision hip arthroplasty.     

The effect of different mineral frames on ectopic bone formation in mouse hind leg muscles induced by native reindeer bone morphogenetic protein

Introduction Bone morphogenetic proteins (BMPs) require carrier material for slow release and framing material for osteoconduction.Materials and methods The effect of a frame on early bone formation induced by partially purified native reindeer BMP in composite implants containing 3 mg of BMP, type IV collagen and tricalcium phosphate (TCP/Col/BMP) or hydroxyapatite (HA/Col/BMP) or biphasic tricalcium phosphate-hydroxyapatite (TCP/HA/Col/BMP) or biocoral (NC/Col/BMP) was evaluated using a mouse hind leg muscle pouch model. Collagen with native reindeer BMP (Col/BMP) and corresponding implants without native reindeer BMP served as controls. Evaluation was done by incorporation of ⁴⁵Ca, radiographically and histologically 3 weeks after the implantation.Results None of the implants without native reindeer BMP were able to induce new bone visible on radiographs. The area of new bone formation in the Col/BMP (p=0.026) and TCP/HA/Col/BMP (p=0.012) groups was significantly greater than in the TCP/Col/BMP group. The optical density of the new bone area was significantly greater in the TCP/HA/Col/BMP group than in the TCP/Col/BMP (p=0.036) or Col/BMP (p=0.02) groups. ⁴⁵Ca incorporation was many times greater in all the groups containing native reindeer BMP than in the corresponding groups without BMP. In the Col/BMP (p=0.046) and TCP/HA/Col/BMP (p=0.046) groups, ⁴⁵Ca incorporation was significantly greater than in the TCP/Col/BMP group. No significant differences were found in any parameters between HA/Col/BMP and NC/Col/BMP groups and the other BMP-containing groups.Conclusions Hydroxyapatite, biocoral and biphasic tricalciumphosphate-hydroxyapatite are equally good as framing material for native reindeer BMP, while tricalciumphosphate is somewhat worse. Osteoinduction of native reindeer BMP works well with collagen alone.     

Perforations of cortical bone allografts improve their incorporation

The incorporation of perforated cortical bone allografts was compared with non-perforated allografts. A 5-cm circumferential defect in the middiaphysis at the tibia was created in adult sheep. A frozen tibial allograft was implanted and fixed with a locked nail for 6 months. There was no postoperative immobilization. Group I consisted of eight sheep with non-perforated allografts, whereas Group II was comprised of 10 sheep with perforated allografts. Union was evaluated radiographically, whereas the central part of the allograft had a densitometric evaluation. Creeping substitution was assessed on microradiographs from cross-sections of the central 3 cm of graft by measurement of porosity and percentage of new and old bone area within the confines of the graft. The width of periosteal and endosteal callus also was determined. There was no statistical difference between both groups for the union score and bone density. However, the cortical bone graft porosity and the amount of new bone within the cortical bone differed significantly between the perforated allografts and the non-perforated ones. Periosteal callus was similar in both groups, whereas endosteal callus was significantly more wide and extended in the perforated allografts. Perforation of a cortical bone substantially improved the amount of newly formed bone by the host when compared with a non-perforated bone. The creation of channels seemed to increase the interface between living soft tissues of the host and the allografted bone with a resulting enhanced incorporation.     

关节置换术后感染非组配式广泛涂层股骨柄二期翻修术的中期疗效

 目的 探讨应用非组配式广泛涂层股骨柄行关节置换术后感染二期翻修术的中期疗效。方法 回顾性分析2005年3月至2006年12月接受全髋关节置换术后感染二期翻修的33例（33髋）患者的病例资料,男20例,女13例;年龄52~80岁,平均（66.1±7.2）岁。二期翻修方案包括一期取出关节假体,彻底清创,置入自制抗生素骨水泥间隔体,抗感染治疗后行二期关节翻修术。抗感染治疗包括静脉抗感染治疗4周、口服抗生素6周。采用美国骨科医师学会（American Academy of Orthopaedic Surgeons,AAOS）分类法评估髋臼骨缺损,Paprosky分类法评估股骨骨缺损。采用Harris髋关节评分评估髋关节功能,术后定期复查X线片评估假体稳定性、移位、松动情况。根据DeLee和Charnley分区法记录髋臼假体周围透光线,根据Gruen分区法记录股骨柄周围透光线。采用Engh等标准评价股骨假体固定情况。再感染的标准与诊断关节感染的标准相同。结果 全部病例随访5~9年,平均（6.1±1.7）年。二期翻修术后无一例出现感染或假体松动。二期翻修术中所取标本微生物培养或病理学检查均为阴性。Harris髋关节评分由术前（42.3±6.5）分提高到末次随访的（89.1±8.5）分。股骨柄骨长入固定30例,纤维稳定固定3例。11例髋臼侧打压植骨和所有股骨髓腔内打压植骨均与宿主骨融合。股骨侧异体皮质骨板移植者10例,9例于二期翻修术后1年与宿主骨融合、1例于术后2年融合。结论 采用非组配式广泛涂层股骨假体行感染二期翻修结合髓腔内颗粒骨打压植骨能取得较好的假体中期生存率和感染清除率。     

Renal fibrosis in cyclosporin A-treated renal allograft recipients: morphological findings in relation to renal hemodynamics

Nineteen nondiabetic kidney graft patients treated with cyclosporin A for 2 years underwent percutaneous renal allograft biopsy as well as renal hemodynamic examination. Renal allograft fibrosis was quantitatively evaluated as the relative volume of the renal cortical interstitium (V_v%) and as the intersttium/tubuli ratio (I/T ratio). The histological changes were then classified into four groups, depending on the degree of interstitial fibrosis. The glomerular filtration rate (GFR), renal plasma flow (RPF), renal blood flow (RBF), filtration fraction (FF), and fractional clearance of sodium, potassium, phosphate, chloride, osmoles, and free water clearance were determined in all patients and in 13 healthy controls. Kidney graft recipients had significantly lower GFR, lower RPF, and lower RBF than the healthy controls (P<0.001 for all comparisons) while FF was similar in patients and controls. Transplant recipients had a significantly higher fractional excretion of sodium, potassium, chloride, and phosphate than controls. All except one patients had clearly increased V_v values, indicating increased interstitial fibrosis. The mean V_v in renal allograft patients was 35%±10% (normal <16%±5%) and the I/T ratio was 1.07±0.60 (normal <0.24±0.08). No correlation was found between the quantitative or semiquantitative biopsy analysis and any renal hemodynamic parameter measured. We conclude that renal function is significantly decreased in kidney graft recipients, but that adaptive tubular changes occur in the graft. Interstitial renal fibrosis was common but did not correlate to any renal functional parameter.     

Blood Vessel Wall–Derived Endothelial Colony-Forming Cells Enhance Fracture Repair and Bone Regeneration

Endochondral bone formation requires new blood vessel formation, and endothelial progenitor cells (EPCs) may play a role in this process. Endothelial colony-forming cells (ECFCs), one subtype of EPCs, isolated from the microvasculature of rat lungs, exhibited cell surface antigen markers and gene products characteristic of endothelial cells and displayed high proliferative potential and an ability to form vessel-like network structures in vitro. The aim of this study was to evaluate whether ECFCs facilitate bone healing during fracture repair and stimulate bone regeneration. When type I collagen sponge containing ECFCs were surgically wrapped around the fractured femurs of rats, newly formed bone mineral at the site of fracture was 13% greater (P = 0.01) and energy to failure was 46% greater (P = 0.01) compared to sponge-wrapped fractures without ECFCs. When ECFCs in type I collagen sponge were surgically implanted into the bone defective area, more new vessels formed locally in comparison with sponge-alone controls and new bone tissues were seen. Further, co-implantation of ECFCs and hydroxyapatite/tricalcium phosphate (HA/TCP) scaffolds at the bone defective sites stimulated more new bone tissues than HA/TCP scaffold alone. These results show that cell therapy with vessel wall–derived ECFCs can induce new vessel formation, stimulate new bone formation, and facilitate bone repair and could be a useful approach to treat non-union fractures and bone defects.     

Biomechanical analysis of allograft bone treated with a novel tissue sterilization process.

BACKGROUND CONTEXT: Several methods to sterilize allograft bone exist, including gamma irradiation and freeze-drying, which can alter the mechanical properties of the graft. Efforts are under way to develop a method for processing osseous allograft that maintains structural integrity. Herein is presented one such method. PURPOSE: To analyze the mechanical properties, compared with nontreated controls, of a novel sterilization process for allograft cortical bone. STUDY DESIGN/SETTING: A controlled biomechanical evaluation of allograft bone under various types of loading after a novel sterilization treatment. PATIENT SAMPLE: Not applicable; basic science. OUTCOME MEASURES: The load to failure was recorded for both the study and control groups, and statistical analysis of these results was performed. Significance level (alpha) and power (beta) were set to 0.05 and 0.90, respectively. Single-factor analysis of variance (ANOVA) was used to detect significant differences between the treated and untreated groups. A post-experimental power analysis was performed for each of the response variables. METHODS: Cortical tibia and femur samples from seven cadaveric donors (mean age 68.7 years) were treated with Biocleanse and compared with untreated samples with regard to density and strength. All samples were loaded to failure under diametral and biaxial compression, shear, and three-point bending. RESULTS: Statistical analysis was done on the density and failure stress for all modes of loading. ANOVA did not indicate a significant (p>.05) effect of treatment on the density except for the axial and biaxial specimens (p<.05). ANOVA analysis of failure stress demonstrated no significant differences (p>.05) between cortical bone treated with Biocleanse and untreated specimens under all four types of mechanical loading. Post-experimental power analysis revealed power to be greater than 0.9 for each test. CONCLUSIONS: Sterilization of allograft bone with Biocleanse does not significantly alter the mechanical properties when compared with untreated samples. The effect of this sterilization process on the osteoconductive and osteoinductive properties of allograft bone must be determined.     

Period of adolescence during which exercise maximizes bone mass in young women

The aim of this cross-sectional study was to investigate the age at which exercise exerted a favorable effect on peak bone mass in young women. The subjects were 24 college athletes (CA), 19 sedentary college students (CN), and 29 high school athletes (HA). Athletes participated in at least 9 h of exercise per week. Lumbar bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA). The history of exercise in puberty and adolescence was estimated by a questionnaire as to weekly participation in exercise, for example, field hockey, basketball, tennis, or soccer. The CA group showed significantly higher lumbar BMD than the CN or HA group (1.230 ± 0.112g/cm₂ vs 1.164 ± 0.120g/cm² orvs 1.164 ± 0.088g/cm₂;P < 0.05). In both the CA and CN groups, those who had a history of exercise during junior high school showed a significantly higher BMD regardless of the history of high school exercise. In the HA group, those who had exercised during junior high school also showed a significantly higher lumbar BMD than those who had not. These data suggested that exercise during junior high school has a favorable effect on peak bone mass, regardless of the history of high school exercise.