Impact Microindentation Research Articles

Feasibility and tolerability of bone impact microindentation testing: a cross-sectional, population-based study in Australia

ObjectivesThe OsteoProbe measures Bone Material Strength Index (BMSi) of cortical bone in living humans using impact microindentation (IMI). Research using this minimally invasive technique is expanding yet, to-date, there have...

Bone Material Strength Index as Measured by Impact Microindentation in Postmenopausal Women With Distal Radius and Hip Fractures.

We tested whether cortical bone tissue properties assessed by in vivo impact microindentation would distinguish postmenopausal women with recent distal radius (DRF) or hip fracture (HF) from nonfracture controls (CONT). We enrolled postmenopausal women with recent DRF (n = 57), HF (n = 41), or CONT (n = 93), and used impact microindentation to assess bone material strength index (BMSi) at the anterior surface of the mid-tibia diaphysis. Areal bone mineral density (aBMD) (g/cm2 ) of the femoral neck (FN), total hip (TH), and lumbar spine (LS) were measured by dual-energy X-ray absorptiometry (DXA). HF and DRF subjects had significantly lower BMD than CONT at all sites (-5.6% to -8.2%, p < 0.001 for all). BMSi was 4% lower in DRF compared to CONT (74.36 ± 8.77 versus 77.41 ± 8.79, p = 0.04). BMSi was similarly lower in HF versus CONT, but the difference did not reach statistical significance (74.62 ± 8.47 versus 77.41 ± 8.79, p = 0.09). Lower BMSi was associated with increased risk of DRF (unadjusted OR, 1.43; 95% CI, 1.02 to 2.00, per SD decrease, p = 0.04), and remained statistically significant after adjustment for age, age and BMI, and age, BMI, and FN BMD (OR = 1.48 to 1.55). Lower BMSi tended to be associated with HF, but only reached borderline significance (unadjusted OR = 1.39; 95% CI, 0.96 to 2.01, p = 0.08). These results provide strong rationale for future investigations aimed at assessing whether BMSi can predict fracture in prospective studies and improve identification of women at risk for fragility fractures. © 2017 American Society for Bone and Mineral Research.

Impact Microindentation: Consistency of Serial Measurements and Alterations in Patients With Paget's Disease of the Tibia.

Impact microindentation (IMI) is a new technique for the in vivo measurement of tissue-level properties of cortical bone in humans. To address issues related to the proper application of IMI in clinical practice and to directly examine cortical bone properties in patients with tibia pathology, we studied 11 subjects without tibia pathology and nine patients with Paget's disease of the tibia in biochemical remission after bisphosphonate treatment. Serial indentations in the tibias of both legs were performed in all subjects by a single operator until 10 adequate measurements were obtained in each tibia. In patients without Paget's disease (7 men and 4 women; mean age, 61.9 years; range, 51 to 72 years), there was no difference in mean bone material strength index (BMSi) between the dominant and nondominant leg (82.1 ± 1.3 and 81.4 ± 1.3, respectively; p = 0.606). In each individual subject studied, sequential indentations in both legs showed no trends for higher or lower values with time. The standard deviation of unnormalized bone material strength (BMSu) was also comparable between the dominant and nondominant tibia (5.3 and 4.5, respectively; p = 0.657). In patients with Paget's disease (4 men and 5 women; mean age, 69.5 years; range, 55 to 87 years), mean BMSi of the Pagetic tibia was lower, albeit nonsignificantly, than that of the contralateral nonaffected tibia (74.7 ± 1.7 and 78.7 ± 1.3, respectively; p = 0.120). In contrast to subjects without Paget's disease, the SD of adequate BMSu values was significantly larger in the Pagetic tibia compared to that of the non-Pagetic tibia (7.6 versus 5.0, respectively, p = 0.008). These results highlight the consistency of serial IMI measurements as performed by a single operator in the presence as well as absence of tibia pathology and illustrate that the method is able to capture alterations of tissue-level cortical bone properties in patients with Paget's disease of the tibia. © 2017 The Authors.Journal of Bone and Mineral Research Published by Wiley Periodicals Inc.

Skeletal fragility in diabetes.

Fracture risk is heightened in patients with both type 1 diabetes (T1D) and type 2 diabetes (T2D). Although bone mineral density by dual-energy X-ray absorptiometry is decreased in T1D, it is paradoxically increased with T2D. To predict fracture risk, the Fracture Risk Assessment Tool (FRAX) can be used in diabetes patients, albeit with refinement. Skeletal abnormalities in diabetes include alterations in microarchitecture in T1D and T2D as well as compromised impact microindentation in T2D. Changes in bone microvasculature, advanced glycation end product accumulation, and bone formation may underlie these findings. When fractures occur in T1D and T2D, consequences are worse than in nondiabetic patients with regard to both morbidity and mortality. With regard to treatment, antiresorptive osteoporosis therapies appear to be effective in the setting of diabetes.

Fracture during oral bisphosphonate therapy is associated with deteriorated bone material strength index

BackgroundSome patients experience fractures while receiving oral bisphosphonates (BPs) treatment. Clinical risk factors, advanced bone density loss, and microarchitecture deterioration have been associated with such fractures but bone tissue properties other than bone mineral density (BMD) have not been assessed. MethodsIn a cross-sectional study of postmenopausal women on bisphosphonates for at least 4years with good adherence to treatment, 21 patients with incident fractures were compared with 18 treated patients without new fractures. Demographic and clinical variables, BMD, laboratory tests, and bone material strength index (BMSi) assessed by impact microindentation at the tibial diaphysis were recorded for all participants. ResultsClinical and laboratory results did not differ between patients taking BPs with incident fractures and those without new fractures. However, BMSi was significantly lower (mean±SD) in those who fractured (73.76±6.49) than in no-fracture patients (81.64±6.26; p=0.001). Lumbar spine (LS) BMD was also lower in fractured patients (p=0.03). Adjusted models including age, body mass index, years on BP treatment, and LS-BMD confirmed an increase in fracture risk per BMSi standard deviation decrease: adjusted OR 23.5 [95% CI 2.16 to 255.66], p=0.01. ROC analyses showed an area under the curve of 0.82 (95% CI 0.68 to 0.95) for BMSi, higher than that for BMD at any location, which ranged from 0.64 (95% CI 0.47 to 0.82) for femoral neck (FN) BMD to 0.71 (95% CI 0.55 to 0.87) for LS-BMD. ConclusionsPatients who fracture while receiving BPs treatment have worse BMSi scores than BP-treated patients without fractures. The potential for BMSi to provide an additional osteoporosis treatment target should be explored.

Bone density, microarchitecture, and material strength in chronic kidney disease patients at the time of kidney transplantation.

BMD measured by dual-energy X-ray absorptiometry (DXA) is used to assess bone health in end-stage renal disease (ESRD) patients. Recently, trabecular bone score (TBS) and microindentation that can measure microarchitectural and mechanical properties of bone have demonstrated better correlation with fractures than DXA in different populations. We aimed to characterize bone health (BMD, TBS, and strength) and calcium/phosphate metabolism in a cohort of 53 ESRD patients undergoing kidney transplantation (KT) and 94 controls with normal renal function. Laboratory workout, lumbar spine/hip BMD measurements (using DXA), lumbar spine TBS, and bone strength were carried out. The latter was assessed with an impact microindentation device, standardized as percentage of a reference value, and expressed as bone material strength index (BMSi) units. Multivariable linear regression was used to study differences between cases and controls adjusted by age, gender, and body mass index. Among cases, serum calcium was 9.6±0.7mg/dl, phosphorus 4.4±1.2mg/dl, and intact parathyroid hormone 214pg/ml [102-390]. Fourteen patients (26.4%) had prevalent asymptomatic fractures in spinal X-ray. BMD was significantly lower among ESRD patients compared to controls: lumbar 0.966±0.15 vs 0.982±0.15 (adjusted p=0.037), total hip 0.852±0.15 vs 0.902±0.13 (adjusted p<0.001), and femoral neck 0.733±0.15 vs 0.775±0.12 (adjusted p<0.001), as were TBS (1.20 [1.11-1.30] vs 1.31 [1.19-1.43] (adjusted p<0.001)) and BMSi (79 [71.8-84.2] vs 82. [77.5-88.9] (adjusted p=0.005)). ESRD patients undergoing transplant surgery have damaged bone health parameters (density, microarchitecture, and mechanical properties) despite acceptably controlled hyperparathyroidism. Detecting these abnormalities may assist in identifying patients at high risk of post-transplantation fractures.

Bone material strength index as measured by impact microindentation is low in patients with fractures irrespective of fracture site

SummaryWe evaluated the relationship between bone material strength index (BMSi) and fragility fractures, including vertebral fractures. Our data showed that BMSi is low in all fracture patients with low bone mass, independently of whether patients sustained a vertebral or a non-vertebral fracture.IntroductionImpact microindentation (IMI) is a new technique for the measurement of tissue level properties of cortical bone in vivo. Previous studies showed an association between BMSi and non-vertebral fractures, but an association with vertebral fractures is still being debated. The objective of this paper was to evaluate the relationship between BMSi and different types of fragility fractures, including vertebral fractures.MethodsIn this cross-sectional study, we measured BMSi in patients of both sexes with different types of fragility fractures and low bone mass with the IMI method using the Osteoprobe®. Vertebral fractures were diagnosed and graded on lateral spine radiographs.ResultsA total of 132 patients were included in the study, of whom 101 patients (65 women) had sustained a low energy fracture and 31 (mean age 57.7 ± 9.9 years) had no history or radiological evidence for a fracture. Of the fracture patients, 53 (mean age 62.8 ± 8.3 years) had only non-vertebral fractures (VF−/Fx+), 34 (mean age 62.8 ± 9.9 years) had vertebral and non-vertebral fractures (VF+/Fx+), and 14 (mean age 64.7 ± 9.3 years) had only vertebral fractures (VF+/Fx−). BMSi values, adjusted for age and BMD, were similar for all three groups of fracture patients (78.9 ± 0.7, 78.3 ± 0.9, and 78.4 ± 1.4, respectively; p = 0.866). BMSi values were not associated with number or severity of vertebral fractures.ConclusionOur data demonstrate that BMSi is low in fracture patients with low bone mass, irrespective of whether they sustained a vertebral fracture or a non-vertebral fracture.

Reduced Bone Material Strength is Associated with Increased Risk and Severity of Osteoporotic Fractures. An Impact Microindentation Study

The aim of the study was to test, whether bone material strength differs between different subtypes of osteoporotic fracture and assess whether it relates to vertebral fracture severity. Cortical bone material strength index (BMSi) was measured by impact microindentation in 66 women with osteoporotic fracture and 66 age- and sex-matched controls without fracture. Bone mineral density (BMD) and bone turnover markers were also assessed. Vertebral fracture severity was graded by semiquantitative (SQ) grading. Receiver operator characteristic (ROC) curves were used to examine the ability of BMSi to discriminate fractures. Subjects with osteoporotic fractures exhibited lower BMSi than controls (71.5 ± 7.3 vs. 76.4 ± 6.2, p < 0.001). After adjusting for age and hip BMD, a significant negative correlation was seen between BMSi and vertebral fracture severity (r 2 = 0.19, p = 0.007). A decrease of one standard deviation (SD) in BMSi was associated with increased risk of fracture (OR 2.62; 95% CI 1.35, 5.10, p = 0.004). ROC curve areas under the curve (AUC) for BMSi in subjects with vertebral fracture (VF), hip fracture (HF), and non-vertebral non-hip fracture (NVNHFx), (mean; 95% CI) were 0.711 (0.608; 0.813), 0.712 (0.576; 0.843), 0.689 (0.576; 0.775), respectively. Combining BMSi and BMD provided further improvement in the discrimination of fractures with AUC values of 0.777 (0.695; 0.858), 0.789 (0.697; 0.882), and 0.821 (0.727; 0.914) for VFx, HFx, and NVNHFx, respectively. Low BMSi of the tibial cortex is associated with increased risk of all osteoporotic fractures and severity of vertebral fractures.

Bone material strength index as measured by impact microindentation is altered in patients with acromegaly.

Acromegaly is a rare disease caused by excess growth hormone (GH) production by the pituitary adenoma. The skeletal complications of GH and IGF-1 excess include increased bone turnover, increased cortical bone mass and deteriorated microarchitecture of trabecular bone, associated with a high risk of vertebral fractures in the presence of relatively normal bone mineral density (BMD). We aimed to evaluate tissue-level properties of bone using impact microindentation (IMI) in well-controlled patients with acromegaly aged ≥18 years compared to 44 controls from the outpatient clinic of the Centre for Bone Quality. In this cross-sectional study, bone material strength index (BMSi) was measured in 48 acromegaly patients and 44 controls with impact microindentation using the osteoprobe. Mean age of acromegaly patients (54% male) was 60.2 years (range 37.9-76.5), and 60.5 years (range 39.8-78.6) in controls (50% male). Patients with acromegaly and control patients had comparable BMI (28.2 kg/m2 ± 4.7 vs 26.6 kg/m2 ± 4.3, P = 0.087) and comparable BMD at the lumbar spine (1.04 g/cm2 ± 0.21 vs 1.03 g/cm2 ± 0.13, P = 0.850) and at the femoral neck (0.84 g/cm2 ± 0.16 vs 0.80 g/cm2 ± 0.09, P = 0.246). BMSi was significantly lower in acromegaly patients than that in controls (79.4 ± 0.7 vs 83.2 ± 0.7; P < 0.001). Our data indicates that tissue-level properties of cortical bone are significantly altered in patients with controlled acromegaly after reversal of long-term exposure to pathologically high GH and IGF-1 levels. Our findings also suggest that methods other than DXA should be considered to evaluate bone fragility in patients with acromegaly.

Technical note: Recommendations for a standard procedure to assess cortical bone at the tissue-level in vivo using impact microindentation

Impact microindentation is a novel method for measuring the resistance of cortical bone to indentation in patients. Clinical use of a handheld impact microindentation technique is expanding, highlighting the need to standardize the measurement technique. Here, we describe a detailed standard operation procedure to improve the consistency and comparability of the measurements across centers.

Impaired bone material properties increase the risk of all fractures and severity of vertebral fractures in osteoporosis: an impact microindentation study

Impaired bone material properties increase the risk of all fractures and severity of vertebral fractures in osteoporosis: an impact microindentation study

Determination of the relaxation function for viscoelastic materials at low velocity impact

The work discusses impact microindentation and its possible application for determination and control of physico-mechanical characteristics of viscoelastic materials. Technique and algorithm for determination of the relaxation function at the dynamic intrusion of the indenter into the viscoelastic half-space are proposed. Experimental dependencies for intrusion of spherical and conical indenter into rubber in the range of initial velocities 0.3–3 m/s were established. It was shown that obtained results do not depend on the shape of the indenter tip and its velocity. The analysis of the results was carried out from the point of view of time and temperature dependencies that are typical for elastomers. Obtained results can be used for analysis and prediction of elastomeric material's response to the applied load with consideration of the loading history.

Spherical indentation of elastic–plastic solids

The finite–element method is used to perform an accurate numerical study of the normal indentation of an elastic–plastic half–space by a rigid sphere. The effects of elasticity and strain–hardening rate of the half–space are explored, and the role of friction is assessed by analysing the limiting cases of frictionless contact and sticking friction. Indentation maps are constructed with axes of contact radius a (normalized by the indenter radius R and the yield strain of the half–space. Competing regimes of deformation mode are determined and are plotted on the indentation map: (i) elastic Hertzian contact; (ii) elastic–plastic deformation; (iii) plastic similarity regime; (iv) finite–deformation elastic contact; and (v) finite–deformation plastic contact. The locations of the boundaries between deformation regimes change only slightly with the degree of strain–hardening rate and of interfacial friction. It is found that the domain of validity of the rigid–strain–hardening similarity solution is rather restricted: it is relevant only for solids with a yield strain of less than 2 x 10 −4 and a / R