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Bai W, Shu L, Sun R, Xu J, Silberschmidt VV, Sugita N. Improvements of material removal in cortical bone via impact cutting method. J Mech Behav Biomed Mater 2020; 108:103791. [PMID: 32469716 DOI: 10.1016/j.jmbbm.2020.103791] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 04/08/2020] [Accepted: 04/12/2020] [Indexed: 11/18/2022]
Abstract
Bone cutting with high efficiency as well as low levels of forces and damage has a great significance for orthopaedic surgeries. Due to the brittleness and anisotropy of cortical bone, a conventional cutting process can cause irregular crack propagation and fractured bone chip, affecting the tissue removal process and postoperative recovery. In this paper, a high-frequency impact cutting method is investigated, and its effect on fracture propagation, chip formation and cutting forces is studied for orthogonal cutting. Experimental results show that cracks are deflected by cement lines in conventional cutting, forming fractured blocks or split chips. In impact cutting, the cutting-induced fractures expand along a main shear direction, generating small pieces of triangular segmented chips. Cutting forces are significantly reduced with vibration-induced impacts; especially, the main cutting force is nearly 70% lower than that in the conventional cutting. The main reason for this is much higher strain rates in high-frequency impact cutting than in a conventional process, and direct penetration of fractures across the osteonal matrix without deflections along the cement lines. This results in a straighter path along the main shear plane and totally different chip morphology; so, a lower consumption of cutting energy in the main shear direction reduces the macroscopic cutting force. The results of this study have an important theoretical and practical value for revealing the mechanism of impact cutting, improving the efficiency of osteotomy and supporting the innovation in bone surgical instruments.
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Affiliation(s)
- Wei Bai
- State Key Lab of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan, 430074, China; Department of Mechanical Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 1138656, Japan.
| | - Liming Shu
- Department of Mechanical Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 1138656, Japan
| | - Ronglei Sun
- State Key Lab of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan, 430074, China
| | - Jianfeng Xu
- State Key Lab of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan, 430074, China.
| | - Vadim V Silberschmidt
- Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Leicestershire, LE11 3TU, UK
| | - Naohiko Sugita
- Department of Mechanical Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 1138656, Japan.
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Hunckler MD, Chu ED, Baumann AP, Curtis TE, Ravosa MJ, Allen MR, Roeder RK. The fracture toughness of small animal cortical bone measured using arc-shaped tension specimens: Effects of bisphosphonate and deproteinization treatments. Bone 2017; 105:67-74. [PMID: 28826844 DOI: 10.1016/j.bone.2017.08.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 08/17/2017] [Accepted: 08/17/2017] [Indexed: 01/22/2023]
Abstract
Small animal models, and especially transgenic models, have become widespread in the study of bone mechanobiology and metabolic bone disease, but test methods for measuring fracture toughness on multiple replicates or at multiple locations within a single small animal bone are lacking. Therefore, the objective of this study was to develop a method to measure cortical bone fracture toughness in multiple specimens and locations along the diaphysis of small animal bones. Arc-shaped tension specimens were prepared from the mid-diaphysis of rabbit ulnae and loaded to failure to measure the radial fracture toughness in multiple replicates per bone. The test specimen dimensions, crack length, and maximum load met requirements for measuring the plane strain fracture toughness. Experimental groups included a control group, bisphosphonate treatment group, and an ex vivo deproteinization treatment following bisphosphonate treatment (5 rabbits/group and 15 specimens/group). The fracture toughness of ulnar cortical bone from rabbits treated with zoledronic acid for six months exhibited no difference compared with the control group. Partially deproteinized specimens exhibited significantly lower fracture toughness compared with both the control and bisphosphonate treatment groups. The deproteinization treatment increased tissue mineral density (TMD) and resulted in a negative linear correlation between the measured fracture toughness and TMD. Fracture toughness measurements were repeatable with a coefficient of variation of 12-16% within experimental groups. Retrospective power analysis of the control and deproteinization treatment groups indicated a minimum detectable difference of 0.1MPa·m1/2. Therefore, the overall results of this study suggest that arc-shaped tension specimens offer an advantageous new method for measuring the fracture toughness in small animal bones.
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Affiliation(s)
- Michael D Hunckler
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Ethan D Chu
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Andrew P Baumann
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Tyler E Curtis
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Matthew J Ravosa
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN 46556, USA; Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Matthew R Allen
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Ryan K Roeder
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN 46556, USA.
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Granke M, Makowski AJ, Uppuganti S, Does MD, Nyman JS. Identifying Novel Clinical Surrogates to Assess Human Bone Fracture Toughness. J Bone Miner Res 2015; 30:1290-300. [PMID: 25639628 PMCID: PMC4478129 DOI: 10.1002/jbmr.2452] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Revised: 11/06/2014] [Accepted: 01/08/2015] [Indexed: 12/13/2022]
Abstract
Fracture risk does not solely depend on strength but also on fracture toughness; ie, the ability of bone material to resist crack initiation and propagation. Because resistance to crack growth largely depends on bone properties at the tissue level, including collagen characteristics, current X-ray based assessment tools may not be suitable to identify age-related, disease-related, or treatment-related changes in fracture toughness. To identify useful clinical surrogates that could improve the assessment of fracture resistance, we investigated the potential of (1)H nuclear magnetic resonance spectroscopy (NMR) and reference point indentation (RPI) to explain age-related variance in fracture toughness. Harvested from cadaveric femurs (62 human donors), single-edge notched beam (SENB) specimens of cortical bone underwent fracture toughness testing (R-curve method). NMR-derived bound water showed the strongest correlation with fracture toughness properties (r = 0.63 for crack initiation, r = 0.35 for crack growth, and r = 0.45 for overall fracture toughness; p < 0.01). Multivariate analyses indicated that the age-related decrease in different fracture toughness properties were best explained by a combination of NMR properties including pore water and RPI-derived tissue stiffness with age as a significant covariate (adjusted R(2) = 53.3%, 23.9%, and 35.2% for crack initiation, crack growth, and overall toughness, respectively; p < 0.001). These findings reflect the existence of many contributors to fracture toughness and emphasize the utility of a multimodal assessment of fracture resistance. Exploring the mechanistic origin of fracture toughness, glycation-mediated nonenzymatic collagen crosslinks and intracortical porosity are possible determinants of bone fracture toughness and could explain the sensitivity of NMR to changes in fracture toughness. Assuming fracture toughness is clinically important to the ability of bone to resist fracture, our results suggest that improvements in fracture risk assessment could potentially be achieved by accounting for water distribution (quantitative ultrashort echo time magnetic resonance imaging) and by a local measure of tissue resistance to indentation, RPI.
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Affiliation(s)
- Mathilde Granke
- Department of Orthopaedic Surgery and Rehabilitation, Vanderbilt University Medical Center, Nashville, TN, USA
- Center for Bone Biology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Alexander J Makowski
- Department of Orthopaedic Surgery and Rehabilitation, Vanderbilt University Medical Center, Nashville, TN, USA
- Center for Bone Biology, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Veterans Affairs, Tennessee Valley Healthcare System, Nashville, TN, USA
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA
| | - Sasidhar Uppuganti
- Department of Orthopaedic Surgery and Rehabilitation, Vanderbilt University Medical Center, Nashville, TN, USA
- Center for Bone Biology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Mark D Does
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA
- Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA
- Department of Electrical Engineering, Vanderbilt University, Nashville, TN, USA
| | - Jeffry S Nyman
- Department of Orthopaedic Surgery and Rehabilitation, Vanderbilt University Medical Center, Nashville, TN, USA
- Center for Bone Biology, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Veterans Affairs, Tennessee Valley Healthcare System, Nashville, TN, USA
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA
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Microstructure and compressive mechanical properties of cortical bone in children with osteogenesis imperfecta treated with bisphosphonates compared with healthy children. J Mech Behav Biomed Mater 2015; 46:261-70. [PMID: 25828157 DOI: 10.1016/j.jmbbm.2014.12.020] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Revised: 12/12/2014] [Accepted: 12/18/2014] [Indexed: 01/17/2023]
Abstract
Osteogenesis imperfecta (OI) is a genetic disorder characterized by a change in bone tissue quality, but little data are available to describe the factors involved at the macroscopic scale. To better understand the effect of microstructure alterations on the mechanical properties at the sample scale, we studied the structural and mechanical properties of six cortical bone samples from children with OI treated with bisphosphonates and compared them to the properties of three controls. Scanning electron microscopy, high resolution computed tomography and compression testing were used to assess these properties. More resorption cavities and a higher osteocyte lacunar density were observed in OI bone compared with controls. Moreover, a higher porosity was measured for OI bones along with lower macroscopic Young's modulus, yield stress and ultimate stress. The microstructure was impaired in OI bones; the higher porosity and osteocyte lacunar density negatively impacted the mechanical properties and made the bone more prone to fracture.
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Turnbull TL, Baumann AP, Roeder RK. Fatigue microcracks that initiate fracture are located near elevated intracortical porosity but not elevated mineralization. J Biomech 2014; 47:3135-42. [PMID: 25065731 DOI: 10.1016/j.jbiomech.2014.06.022] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Revised: 05/07/2014] [Accepted: 06/18/2014] [Indexed: 12/01/2022]
Abstract
In vivo microcracks in cortical bone are typically observed within more highly mineralized interstitial tissue, but postmortem investigations are inherently limited to cracks that did not lead to fracture which may be misleading with respect to understanding fracture mechanisms. We hypothesized that the one fatigue microcrack which initiates fracture is located spatially adjacent to elevated intracortical porosity but not elevated mineralization. Therefore, the spatial correlation between intracortical porosity, elevated mineralization, and fatigue microdamage was investigated by combining, for the first time, sequential, nondestructive, three-dimensional micro-computed tomography (micro-CT) measurements of each in cortical bone specimens subjected to compressive fatigue loading followed by a tensile overload to fracture. Fatigue loading resulted in significant microdamage accumulation and compromised mechanical properties upon tensile overload compared to control specimens. The microdamage that initiated fracture upon tensile overload was able to be identified in all fatigue-loaded specimens using contrast-enhanced micro-CT and registered images. Two-point (or pair) correlation functions revealed a spatial correlation between microdamage at the fracture initiation site and intracortical porosity, but not highly mineralized tissue, confirming the hypothesis. This difference was unique to the fracture initiation site. Intracortical porosity and highly mineralized tissue exhibited a significantly lower and higher probability, respectively, of being located spatially adjacent to all sites of microdamage compared to the fracture initiation site. Therefore, the results of this study suggest that human cortical bone is tolerant of most microcracks, which are generally compartmentalized within the more highly mineralized interstitial tissue, but a single microcrack of sufficient size located in spatial proximity to intracortical porosity can compromise fracture resistance.
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Affiliation(s)
- Travis L Turnbull
- Department of Aerospace and Mechanical Engineering, Bioengineering Graduate Program, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Andrew P Baumann
- Department of Aerospace and Mechanical Engineering, Bioengineering Graduate Program, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Ryan K Roeder
- Department of Aerospace and Mechanical Engineering, Bioengineering Graduate Program, University of Notre Dame, Notre Dame, IN 46556, USA.
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Zimmermann EA, Gludovatz B, Schaible E, Busse B, Ritchie RO. Fracture resistance of human cortical bone across multiple length-scales at physiological strain rates. Biomaterials 2014; 35:5472-81. [PMID: 24731707 DOI: 10.1016/j.biomaterials.2014.03.066] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Accepted: 03/22/2014] [Indexed: 12/27/2022]
Abstract
While most fracture-mechanics investigations on bone have been performed at low strain rates, physiological fractures invariably occur at higher loading rates. Here, at strain rates from 10(-5) to 10(-1) s(-1), we investigate deformation and fracture in bone at small length-scales using in situ small-angle x-ray scattering (SAXS) to study deformation in the mineralized collagen fibrils and at the microstructural level via fracture-mechanics experiments to study toughening mechanisms generating toughness through crack-tip shielding. Our results show diminished bone toughness at increasing strain rates as cracks penetrate through the osteons at higher strain rates instead of deflecting at the cement lines, which is a prime toughening mechanism in bone at low strain rates. The absence of crack deflection mechanisms at higher strain rates is consistent with lower intrinsic bone matrix toughness. In the SAXS experiments, higher fibrillar strains at higher strain rates suggest less inelastic deformation and thus support a lower intrinsic toughness. The increased incidence of fracture induced by high strain rates can be associated with a loss in toughness in the matrix caused by a strain rate induced stiffening of the fibril ductility, i.e., a "locking-up" of the viscous sliding and sacrificial bonding mechanisms, which are the origin of inelastic deformation (and toughness) in bone at small length-scales.
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Affiliation(s)
| | - Bernd Gludovatz
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Eric Schaible
- Experimental Systems Group, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Björn Busse
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA; Department of Osteology and Biomechanics, University Medical Center, Hamburg, Germany
| | - Robert O Ritchie
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA; Department of Materials Science and Engineering, University of California, Berkeley, CA, USA.
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