Bone Hardness Research Articles

Human iliac crest cancellous bone elastic modulus and hardness differ with bone formation rate per bone surface but not by existence of prevalent vertebral fracture

The goals of this study were to measure tissue-level elastic moduli and hardness of human cancellous bone using nanoindentation, and determine the relationship between nanoindentation results and previously measured bone histomorphometric variables and bone mineralization. Forty iliac crest biopsies were used in this study, which were collected from Caucasian females with vertebral fracture or from a normal healthy female Caucasian population. They were also categorized into two groups according to high or low bone formation rate per bone surface (BFR/BS). Thirty-two sites were randomly selected on each specimen for nanoindentation with a Berkovich diamond indenter. Two sets of elastic moduli and hardness were calculated using the continuous stiffness measurement method and the Oliver-Pharr method, respectively. Relationships between nanoindentation results and donor age, bone mineralization, and histomorphometric variables were examined. No difference in elastic moduli or hardness was observed between the normal and fracture groups. Significantly lower elastic moduli were observed in the high BFR/BS group. The elastic moduli and hardness measurements were not significantly correlated with the bone mineralization measured independently in a previous study. Linear correlation between elastic modulus and hardness calculated using the Oliver-Pharr method was not different between the normal and fracture groups or between the high and low BFR/BS groups. Nanoindentation hardness was a very good predictor of bone tissue elastic modulus for both normal and osteoporotic bone tissues. Osteoporosis may not change the relationship between bone tissue elastic modulus, bone hardness, and bone mineralization.

Conservative management of bilateral femoral neck fractures in a child with autosomal dominant osteopetrosis

Management of minimally displaced femoral neck fractures in paediatric patients with autosomal dominant osteopetrosis (ADO) remains unclear as only small numbers have been reported. There are no detailed reports on successful conservative treatment. Common causes of failure in this particular area include non-union and development of coxa vara. Although there are no quantitative studies, case reports have influenced most authors to recommend operative treatment. It is well recognised that operative treatment of osteopetrotic bone is challenging. Problems arise intraoperatively due to the bone hardness, and postoperatively due to altered biomechanics and defective remodelling. This case of a child with ADO who suffered two asynchronous compression-side stress fractures in the femoral neck demonstrates that non-operative management can be satisfactory. After 8 weeks with partial weight-bearing the fractures were stable. At the latest follow-up 2.5 and 4 years after the fractures the patient presented with an excellent clinical and radiological outcome. There was no development of coxa vara.

Mechanical properties of femoral cortical bone following cemented hip replacement

Femoral bone remodeling following total hip replacement is a big concern and has never been examined mechanically. In this study, six goats underwent unilateral cemented hip hemiarthroplasty with polymethyl methacrylate (PMMA) bone cement. Nine months later animals were sacrificed, and the femoral cortical bone slices at different levels were analysed using microhardness testing and microcomputed tomography (micro-CT) scanning. Implanted femurs were compared to contralateral nonimplanted femurs. Extensive bone remodeling was demonstrated at both the proximal and middle levels, but not at the distal level. Compared with the nonimplanted side, significant decreases were found in the implanted femur in cortical bone area, bone mineral density, and cortical bone hardness at the proximal level, as well as in bone mineral density and bone hardness at the middle level. However, no significant difference was observed in either variable for the distal level. In addition, similar proximal-to-distal gradient changes were revealed both in cortical bone microhardness and bone mineral density. From the mechanical point of view, the results of the present study suggested that stress shielding is an important mechanical factor associated with bone adaptation following total hip replacement.

Examination of local variations in viscous, elastic, and plastic indentation responses in healing bone

A viscous-elastic-plastic indentation model was used to assess the local variability of properties in healing porcine bone. Constant loading- and unloading-rate depth-sensing indentation tests were performed and properties were computed from nonlinear curve-fits of the unloading displacement-time data. Three properties were obtained from the fit: modulus (the coefficient of an elastic reversible process), hardness (the coefficient of a nonreversible, time-independent process) and viscosity (the coefficient of a nonreversible, time-dependent process). The region adjacent to the dental implant interface demonstrated a slightly depressed elastic modulus along with an increase in local time-dependence (smaller viscosity); there was no clear trend in bone hardness with respect to the implant interface. Values of the elastic modulus and calculated contact hardness were comparable to those obtained in studies utilizing traditional elastic-plastic analysis techniques. The current approach to indentation data analysis shows promise for materials with time-dependent indentation responses.

The effect of tissue condition and applied load on Vickers hardness of human trabecular bone

Hardness of trabecular human bone, evaluated by microindentation testing, has generally been measured on embedded tissues. It was known that this was not ideal but it had been preferred to other conditions (e.g. wet or dehydrated) as the trabeculae could withstand the applied load and the measurements were reliable. The aim of this study was to investigate if the tissue condition of the specimen and the applied load would alter the hardness values measured by Vickers microindentation. Vickers hardness values of human trabecular bone from the femoral head, prepared in three different ways (wet, dry and embedded) and tested with two different loads (50 and 25 gf), were measured. No significant difference was found between the two different loads. However, in several cases the 50 gf indentations had to be redone because they were too large or the trabecula broke locally. Even if the outlines of the indentations on wet bone were slightly less marked than the ones done on dehydrated or embedded bone, it was possible to measure the hardness. Significant differences of Vickers hardness values were found between the three preparations: the hardness increased passing from wet to dried (10%) and from wet to embedded (35%). Whereas the variation coefficient of the three tissue conditions were comparable. In conclusion, it is recommended to test human trabecular bone in a wet condition as it better represents the in vivo condition. Furthermore the use of a 25 gf load is suggested, allowing hardness measurements on almost all trabeculae without breaking them.

Osteoporoza - multidisciplinarna i radioloska tema

Osteoporosis in one of the most common diseases among the elderly individuals. Bone hardness is reduced to the critically low level. Even the smallest trauma makes previously healthy individual severely ill patient. In the USA, 1.6 million people sustain fractures due to osteoporosis each year, while approximately 14 billion dollars is spent on their treatment. The costs of osteoporosis treatment exceed the costs of prevention. The studies on the incidence, prevalence and socioeconomic aspects of osteoporosis, its prevention and treatment are expected to be carried out in our country in the future. Prevention of osteoporosis is not an individual problem, but it has wide social implications. Osteoporosis may be prevented and further loss of bone substance may be discontinued.

Harder and Stiffer Bone Osseointegrated to Roughened Titanium

Mechanisms underlying the beneficial anchorage of roughened titanium implants have not been identified. We hypothesized that the implant surface roughness alters intrinsic biomechanical properties of bone integrated to titanium. Nano-indentation performed on two- and four-week post-implantation bone specimens of rats revealed that bone integrated to acid-etched titanium was approximately 3 times harder than that integrated to the machined titanium, both at the osseointegration interface and at the inner area of the peri-implant bone. The hardness of the acid-etched surface-associated bone was equivalent to that of untreated cortical bone at week 4, while the bone hardness around the machined surface was equivalent to that of the untreated trabecular bone. The elastic modulus of the integrated bone was 1.5 to 2.5 times greater around the acid-etched surface than around the machined surface. Analysis of the data suggests that the implant surface roughness affects the biomechanical quality of osseo-integrated bone, and that the bone integrated to the acid-etched surface is harder and stiffer than the bone integrated to the machined surface.

Elastic modulus and hardness of cortical and trabecular bovine bone measured by nanoindentation

The elastic modulus and hardness of several microstructure components of dry bovine vertebrae and tibia have been investigated in the longitude and transverse directions using nanoindentation. The elastic modulus for the osteons and the interstitial lamellae in the longitude direction were found to be (24.7±2.5) GPa and (30.1±2.4) GPa. As it's difficult to distinguish osteons from interstitial lamellae in the transverse direction, the average elastic modulus for cortical bovine bone in the transverse direction was (19.8±1.6) GPa. The elastic modulus for trabecular bone in the longitude and transverse direction were (20±2) GPa and (14.7±1.9) GPa respectively. The hardness also varied among the microstructure components in the range of 0.41–0.89 GPa. Analyses of variance show that the values are significantly different.

Low intensity pulsed ultrasound increases the matrix hardness of the healing tissues at bone–tendon insertion—a partial patellectomy model in rabbits

This study evaluated the low intensity pulsed ultrasound enhancement on matrix hardness of the healing tissues at the bone-tendon junction. Sixteen 18 week-old mature female rabbits were used. An established transverse partial patellectomy was performed at the distal one-third of the patella. Animals were then divided according to their body weight into ultrasound group (n = 8) with daily treatment of low intensity pulsed ultrasound and control group (n = 8) without ultrasound treatment. Animals were euthanized at week 8 and 16 postoperatively to evaluate the radiographic new bone formation and the Vickers hardness of the matrix of the healing tissues at the bone-tendon junction. (1) Comparing with the control group, the anterior-posterior area of the new bone in the ultrasound treated group was found on average to be 3.0 and 3.1 times greater at week 8 and 16, respectively (P < 0.01). (2) The Vickers hardness of the new bone in ultrasound group was 11.3% (P < 0.05) significantly lower at week 8 but 20.0% (P < 0.05) significantly higher at week 16 as compared with that of the control group. (3) The Vickers hardness of the newly regenerated fibrocartilage zone, healing tendon, and cartilaginous metaplasia in ultrasound group was found higher than the control group at both week 8 and 16, but the difference was significant at week 16 only, being 44.1% (P < 0.05), 20.1% (P < 0.01), and 46.4% (P < 0.01) higher, respectively. The preliminary findings suggested for the first time that low intensity pulsed ultrasound treatment resulted in the enhancement of the matrix hardness in new bone, fibrocartilage, cartilaginous metaplasia, and healing tendon at the healing bone-tendon junction. These findings can be extrapolated into clinical practice, i.e. the more rapid healing induced by low intensity pulsed ultrasound, the earlier mobilization of the affected joint. The beneficial effects on prevention of the musculoskeletal deterioration resulting from the prolonged immobilization would be therefore expected.

Bone Intrinsic Material Properties in Three Inbred Mouse Strains

This study assessed genetically based differences in intrinsic material properties of both cortical and cancellous bone in adult females of three inbred mouse strains [C57BL/6J (B6), DBA/2J (D2), C3H/HeJ (C3)]. These mouse strains have previously been shown to differ in bone mineral content (BMC) and density (BMD). Distal femoral cancellous bone and midshaft cortical bone in femurs and tibias were assessed for intrinsic material properties using nanoindentation technique. The intrinsic material properties tested were modulus (E(b)) and hardness (H) of the midshaft femoral and tibial cortical bone cross sections and of cancellous bone in the distal femur. Both femoral and tibial cortical bone intrinsic material properties were different among the three inbred mouse strains. Femoral modulus and tibial hardness in cortical bone and hardness in cancellous bone were either greatest or showed greater trends in C3 mice as compared to both D2 and B6. Cancellous bone modulus was similar among the three mouse strains. With the exception of the D2 mice, the femoral and tibial cortical modulus were similar within each mouse strain. The tibial cortical modulus was smaller than the femoral cortical modulus for D2 mouse strain. The cortical hardness was greater in tibiae compared with that in femora within each mouse strain. The nanoindentation data suggest that cortical and cancellous intrinsic material properties are influenced by the genetic background of the inbred mouse strains. The inbred mouse strain-related intrinsic material property phenotype can be used to locate responsible quantitative trait loci (QTLs) in future studies of recombinant inbred mouse strains.

大腿骨断面の材料力学的特性評価(S02-2 生体組織のマルチスコープメカニクス(2).微細構造とメカニクス,S02 生体組織のマルチスコープメカニクス)

In this paper, the nanoindentation technique is applied to mechanical property estimation of bone with osteon and microstructures at the micron scale. The specimens were prepared from fresh pig femurs. The elastic modulus and hardness are directly calculated from the characteristic curve for the indentation load-displacement. The nanoindentation test applied to this study shows that the hardness and elastic properties of femoral cortical bone in the longitudinal direction are significantly dependent upon the osteon location in the cortical specimens.

生体骨の超音波による密度及び硬度測定(OS3-1 医療・福祉・生物関連の総合バイオエンジニアリング)

生体骨の超音波による密度及び硬度測定(OS3-1 医療・福祉・生物関連の総合バイオエンジニアリング)

Histomorphometric and microhardness assessments of sheep cortical bone surrounding titanium implants with different surface treatments.

Several factors influence the healing process and the long-term mechanical stability of cementless fixed implants, such as bone remodeling and mineralization processes. Histomorphometric and bone hardness measurements were taken in implants inserted in sheep femoral cortical bone at different times to compare the in vivo osseointegration of titanium screws (diam.; 3.5 x 7 mm length) with the following surface treatments: machined (Ti-MA); acid-etched (Ti-HF); HA vacuum plasma spray (Ti-HA); and Ca-P anodization followed by a hydrothermal treatment (Ti-AM/HA). Ti-MA and Ti-AM/HA implants presented the lowest (Ra = 0.20 +/- 0.01 microm) and highest (Ra = 1.97 +/- 0.64 microm) significant (p < 0.0005) roughness value, respectively. Bone-to-implant contact of Ti-HF was lower than that of the other surface treatments at both experimental times (8 weeks: -20%, ns; 12 weeks: -30%, p < 0.01). Significant differences in MAR (mineral apposition rate) were also found between the different experimental times for Ti-MA (115%, p < 0.01) and Ti-HF (57%, p < 0.01), demonstrating that bone growth had slowed inside the screw threads of Ti-HA and Ti-AM/HA after 12 weeks. No bone microhardness changes in preexisting host bone were found, while Ti-MA showed the lowest value for the inner thread area at 8 weeks (HV(200 microm)= 49.8 +/- 3.8 HV). These findings confirm that osseointegration may be accelerated by adequate surface roughness and bioactive ceramic coating such as Ca-P anodization followed by a hydrothermal treatment, which enhance bone interlocking and mineralization.

Material properties of subchondral bone from patients with osteoporosis or osteoarthritis by microindentation testing and electron probe microanalysis.

Cancellous bone from patients with osteoarthritis (OA) has a reduced material density and appears to be undermineralized. It is hypothesized that this will result in a reduction in the mechanical stiffness and strength of the bone matrix. In this study, bone was obtained from superior and inferior sites, subjected to relatively high and low loads, respectively, from human femoral heads retrieved after surgery for osteoporotic hip fracture (OP), or for hip arthroplasty due to OA. Microindentation testing was used to measure the hardness of cancellous bone at various depths from the subchondral bone plate. The elemental composition from immediately adjacent microscopic sites was determined using electron probe microanalysis (EPMA). Overall, OA bone was found to have hardness values that were 7% lower than those from OP bone. Bone from the inferior site was harder than that from the superior in both diseases except in female OP patients. There was no variation with depth below the subchondral plate and no difference between sexes. No difference was found in the composition of the bone from the different disease groups and no correlation was found between hardness and any of the composition measurements. Though only an indirect measurement of stiffness, the reduction in hardness values supports the hypothesis that OA bone has a reduced elastic modulus.

Mechanical and histomorphometric evaluations of titanium implants with different surface treatments inserted in sheep cortical bone

Improvement of the implant–bone interface is still an open problem and the interest in chemical modification of implant surfaces for cementless fixation has grown steadily over the past decade. Mechanical and histomorphometric investigations were performed at different times on implants inserted into sheep femoral cortical bone to compare the in vivo osseointegration of titanium screws (∅ 3.5×7 mm length) with different surface treatments. After 8 weeks of implantation, the push-out force of anodized and hydrothermally treated implants (ANODIC) was significantly higher than that of machined implants (MACH) (36%, p<0.0005), whereas a decrease of 39% was observed for acid-etched implants (HF) when compared to other surface treatments. After 12 weeks of implantation, the push-out force values of HF implants were still significantly lower than those observed for MACH (−19%, p<0.01) and hydroxyapatite vacuum plasma-sprayed implants (HAVPS, −25%, p<0.0005), and the highest push-out force was found in HAVPS ( p<0.001) implants. After 8 and 12 weeks of implantation, the AI of HF implants was significantly ( p<0.05) lower (∼−25%) than that of MACH, HAVPS and ANODIC implants. In conclusion, results appear to confirm that there are no specific differences between ANODIC and HAVPS implants in terms of behavior. Moreover, although MACH implants show some surface contaminating agents, they appear to ensure good osseointegration within 12 weeks both mechanically and histomorphometrically, as do ANODIC and HAVPS implants. However, further studies are required to investigate bone hardness and mineralization around implants.

916 超音波による骨の密度及び硬度測定法に関する研究

916 超音波による骨の密度及び硬度測定法に関する研究

Osseointegration of sandblasted or anodised hydrothermally-treated titanium implants: mechanical, histomorphometric and bone hardness measurements.

The improvement of the implant-bone interface is still an open problem in the long-term mechanical stability of cementless fixed implants. Mechanical, histomorphometric and bone hardness measurements were performed in sheep femoral cortical bone implants at 8 and 12 weeks from surgery to compare in vivo the osseointegration of titanium screws (psi 3.5 mm x 7 mm length) with two different surface treatments: sandblasting with 70-100 microm HA followed by acid etching with HNO3 (Group A) and Ca-P anodization followed by a hydrothermal treatment (Group B). No significant differences were found for maximum push-out force and interfacial strength between groups at both experimental times. No significant difference was observed for Bone Ingrowth between groups at both experimental times, while the Affinity Index of Group B was significantly higher (7.5%, p<0.05) and lower (10.2%, p<0.05) than that of Group A at 8 and 12 weeks, respectively. Finally, a significant increase in bone microhardness measured within 200 microm from the interface and inside the thread depth of Group A was observed between the two experimental times (p<0.05). In conclusion, present findings show that osseointegration may be accelerated by adequate surface roughness and bioactive ceramic coating such as current tested treatments which enhance bone interlocking and mineralization.

Microstructural elasticity and regional heterogeneity in human femoral bone of various ages examined by nano-indentation

The elastic modulus and hardness of secondary osteonal and interstitial bone was examined through the thickness of the cortex of human femora of various ages by nano-indentation. There was a clear difference between the stiffness and hardness of secondary osteonal and interstitial bone, the latter being stiffer ( F 1,48=56.0, P<0.001). There were some differences between the bones of different subjects; however, there were no differences that could be reliably associated with the chronological age of the subject, or with differences in location through the thickness of the cortex ( F 2,48=0.21, P=0.810). Previous studies have been equivocal in relating changes in the macroscopic ‘composite’ material stiffness of bone to the age of the individual. By combining the results of the nano-tests with histological measures, we were able to produce a good relationship of the microstructural properties at the matrix level with the bending modulus of whole bone ( R 2=0.88, P<0.001) and this improved further by taking into account the age of the individual ( R 2=0.94, P<0.001). Our results suggest that using differences in the volumetric proportions of secondary osteons versus interstitial bone, and the properties of these elements/structures in isolation may be a more accurate method of determining differences in elastic modulus of whole bone between individuals of various ages.

Age, gender, and bone lamellae elastic moduli.

To enhance preventative and therapeutic strategies for metabolic bone diseases and bone fragility disorders, we began to explore the physical properties of bone tissue at the cellular level. Proximal femurs were harvested from 27 cadavera (16 male and 11 female) for in vitro measurement of the mechanical properties. We measured the variations in lamellar-level elastic modulus and hardness in human bone as a function of age and gender to identify microstructural properties responsible for age and gender-related reductions in the mechanical integrity. The lateral femoral necks were examined, and age, gender, height, body mass, and body mass index were not found to correlate with lamellar-level elastic modulus or hardness. This result was consistent for osteonal, interstitial, and trabecular tissue. These data suggest that increased bone mass maintenance, known to occur in heavier individuals, is not accompanied by increases in the lamellar-level elastic modulus or hardness. The independence of elastic modulus and hardness from age and gender suggests that age and gender-related decreases in mechanical integrity do not involve alterations in elastic modulus or hardness of the extracellular matrix. Lamellar-level ultimate, fatigue, and fracture toughness properties should also be investigated. Other factors, such as tissue mass and organization, may also contribute to age and gender-related decreases in the mechanical integrity.

97-06-06 一般女子学生とスポーツ選手の骨振動解析法による骨硬度の比較に関する研究(平成9年度プロジェクト研究報告(保健学部・保健学研究科),研究助成金による成果紹介)

97-06-06 一般女子学生とスポーツ選手の骨振動解析法による骨硬度の比較に関する研究(平成9年度プロジェクト研究報告(保健学部・保健学研究科),研究助成金による成果紹介)