Bone material properties as measured by Reference Point Indentation are low in subjects with acromegaly

Abstract Context: Skeletal deterioration, leading to an increased risk of fracture, is a known complication of type 2 diabetes mellitus (T2D). Yet plausible mechanisms to account for skeletal fragility in T2D have not been clearly established. Objective: The objective of the study was to determine whether bone material properties, as measured by reference point indentation, and advanced glycation endproducts (AGEs), as determined by skin autofluorescence (SAF), are related in patients with T2D. Design: This was a cross-sectional study. Setting: The study was conducted at a tertiary medical center. Patients: Sixteen postmenopausal women with T2D and 19 matched controls participated in the study. Main Outcome Measures: Bone material strength index (BMSi) by in vivo reference point indentation, AGE accumulation by SAF, and circulating bone turnover markers were measured. Results: BMSi was reduced by 9.2% in T2D (P = .02) and was inversely associated with the duration of T2D (r = −0.68, P = .004). Increased SAF was associated with reduced BMSi (r = −0.65, P = .006) and lower bone formation marker procollagen type 1 amino-terminal propeptide (r = −0.63, P = .01) in T2D, whereas no associations were seen in controls. SAF accounted for 26% of the age-adjusted variance in BMSi in T2D (P = .03). Conclusions: Bone material properties are impaired in postmenopausal women with T2D as determined by reference point indentation. The results suggest a role for the accumulation of AGEs to account for inferior BMSi in T2D.

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Developments in Modelling Bone Screwing

Current Directions in Biomedical Engineering ◽

10.1515/cdbme-2020-3029 ◽

2020 ◽

Vol 6 (3) ◽

pp. 111-114

Author(s):

Jack Wilkie ◽

Paul D. Docherty ◽

Knut Möller

Keyword(s):

Material Properties ◽

Frictional Coefficient ◽

Viscous Friction ◽

Model Parameters ◽

General Shape ◽

Bone Material ◽

Bone Material Properties ◽

Modelling Methodology ◽

Recorded Data ◽

Friction Models

AbstractINTRODUCTION: A torque-rotation model of the bone-screwing process has been proposed. Identification of model parameters using recorded data could potentially be used to determine the material properties of bone. These properties can then be used to recommend tightening torques to avoid over or under-tightening of bone screws. This paper improves an existing model to formulate it in terms of material properties and remove some assumptions. METHOD: The modelling methodology considers a critical torque, which is required to overcome friction and advance the screw into the bone. Below this torque the screw may rotate with elastic deformation of the bone tissue, and above this the screw moves relative to the bone, and the speed is governed by a speed-torque model of the operator’s hand. The model is formulated in terms of elastic modulus, ultimite tensile strength, and frictional coefficient of the bone and the geometry of the screw and hole. RESULTS: The model output shows the speed decreasing and torque increasing as the screw advances into the bone, due to increasing resistance. The general shape of the torque and speed follow the input effort. Compared with the existing model, this model removes the assumption of viscous friction, models the increase in friction as the screw advances into the bone, and is directly in terms of the bone material properties. CONCLUSION: The model presented makes significant improvements on the existing model. However it is intended for use in parameter identification, which was not evaluated here. Further simulation and experimental validation is required to establish the accuracy and fitness of this model for identifying bone material properties.

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