Publications by authors named "Heidi-Lynn Ploeg"
Article Synopsis
- Micro-Finite Element analysis (μFEA) is commonly used in biomechanical research to predict bone properties but is resource-intensive and time-consuming.
- A new alternative method called Firm and Floppy Boundary LEM (FFB-LEM) is introduced, using LAMMPS software to estimate trabecular bone mechanical properties quickly and accurately.
- FFB-LEM calculations take about 15 minutes compared to 30-50 minutes for traditional FEA methods, with no significant differences in results between the two approaches for both bovine and human bone samples.
Article Synopsis
- - The study examines how dental implant diameter and taper design influence the mechanical engagement (anchorage) of implants when inserted into bone, focusing on stress distribution during insertion.
- - Two types of implants (parallel-walled and tapered) with different diameters were tested in rigid polyurethane foam using specific drilling methods to analyze their effects on insertion torque (IT) and stress distribution.
- - Results showed that for tapered implants, the diameter significantly impacted IT and stress distribution, indicating that taper design helps distribute stress away from the threads during insertion, unlike parallel-walled implants.
Mechanical loading of ex vivo bovine trabecular bone in 3D printed bioreactor chambers.
J Mech Behav Biomed Mater
May 2024
Article Synopsis
- Previous methods for culturing bone used polycarbonate bioreactors, which were hard to make and limited in size, prompting the development of a new 3D printed MED610 bioreactor.
- This study involved culturing trabecular bone cores from bovine sternum in the MED610 bioreactors, comparing groups subjected to mechanical loading versus control.
- Results showed the Load group's apparent elastic modulus increased significantly more than the control group over 21 days, indicating the new bioreactor effectively supports bone adaptation, but larger studies are needed for more robust conclusions.
Aseptic loosening due to mechanical failure of bone cement is considered to be a leading cause of revision of joint replacement systems. Detailed quantified information on the number, size and distribution pattern of pores can help to obtain a deeper understanding of the bone cement's fatigue behavior. The objective of this study was to provide statistical descriptions for the pore distribution characteristics of laboratory bone cement specimens with different amounts of antibiotic contents.
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- The study aimed to explore the distribution of mineral density in dog dentin using advanced imaging techniques (µ-CT) and to analyze how mineral density affects the elastic properties of dentin. * Ten mature dogs' maxillary canine teeth were analyzed, revealing that mineral density and elastic modulus increased from the inner dentin to the outer enamel and from the base to the tip of the tooth. * The findings indicated a moderate correlation between mineral density and elastic modulus, suggesting that while mineral density plays a role in the mechanical properties of dentin, other factors like collagen content also influence its behavior.
Canine tooth shape is known to vary with diet and killing behavior in wild animals and the relationship between form and function is driven in part by selective pressure. However, comparative investigation of the domestic dog (Canis lupus familiaris) is of interest. How do they compare to their wild counterparts? This study sought to quantify and characterize the morphology of the canine tooth in the domestic dog, and to provide a preliminary investigation into the variance in canine tooth morphology across individual dogs of varying breeds.
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- The study examines how architectural design parameters of 3D-printed polymer scaffolds—specifically porosity, height-to-diameter (H/D) ratio, and pore size—affect their mechanical properties, particularly compressive strength.
- Controlled experiments were conducted by varying these parameters, revealing that both porosity and H/D ratio significantly influence the apparent elastic modulus and bulk yield stress of the materials.
- While pore size did not greatly affect mechanical properties, understanding these parameters can aid in optimizing bone scaffold development for better biomechanical performance.
Investigations into teeth mechanical properties provide insight into physiological functions and pathological changes. This study sought to 1) quantify the spatial distribution of elastic modulus, hardness and the microstructural features of dog dentin and to 2) investigate quantitative relationships between the mechanical properties and the complex microstructure of dog dentin. Maxillary canine teeth of 10 mature dogs were sectioned in the transverse and vertical planes, then tested using nanoindentation and scanning electron microscopy (SEM).
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- The study focuses on maximum insertion torque (IT) for dental implants, a key factor in evaluating implant stability and clinical success.
- An analytical model was developed to separately assess contributions from the implant thread and taper, while also evaluating factors like bone density, drill technique, and surface finish.
- The model successfully distinguished between implant types and showed that higher bone density and specific drilling methods improved insertion torque, highlighting the importance of different design elements on implant effectiveness.
Article Synopsis
- Reverse shoulder arthroplasty (RSA) can fail due to glenoid component loosening, prompting the need for revision surgery; this study explored factors affecting micromotion of glenoid baseplates in RSA.
- An experiment evaluated four factors: type of central fixation (peg vs. screw), length of cortical engagement, type of peripheral screw (locking vs. nonlocking), and density of bone surrogate used; central peg fixation showed the most micromotion.
- Results indicated that using a central screw with longer engagement reduced micromotion significantly, suggesting these choices can help decrease the risk of glenoid loosening and the need for further surgery.
Aseptic loosening is the most common reason for the long-term revision of cemented arthroplasties with fracture of the cement being a postulated cause or contributing factor. In our previous studies we showed that adding an antibiotic to a polymethylmethacrylate (PMMA) bone cement led to detrimental effects on various mechanical properties of the cement such as bending strength, compressive strength and fracture toughness (KIC). This finding implied that the mechanical failure of antibiotic-loaded PMMA bone cement was influenced by its pore volume fraction.
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- One fifth of idiopathic clubfoot cases do not fully resolve with Serial Ponseti casting, and recurrence occurs in 20%-30% of patients.
- To avoid x-ray exposure, MRI is used to assess joints with mostly unossified bones, but traditional geometric measurements from MRI are less accurate than those from 3D models.
- This study develops a method for statistical shape modeling (SSM) of the talus, revealing significant differences in bone shape between normal and clubfoot specimens, which could enhance diagnosis.
Article Synopsis
- Different methods to evaluate bone stiffness can vary a lot based on the background of the researchers and the complexity of bone itself.
- The study focused on quantifying errors in predicting long-bone bending stiffness (flexural rigidity) using a bi-material bone surrogate tested under specific conditions.
- Results showed that CAD-based finite element analysis (FEA) was the most accurate for determining bone stiffness, while mechanical testing was the least reliable, often underestimating flexural rigidity.
Effect of insertion factors on dental implant insertion torque/energy-experimental results.
J Mech Behav Biomed Mater
December 2020
Article Synopsis
- Anchorage of dental implants is measured using maximum insertion torque (MIT) and insertion energy (IE), which are important for ensuring positive clinical outcomes.
- * A study examined how factors like bone density, drill protocol, surface finish, and cutting flute affect MIT and IE using a controlled experiment with polyurethane foam blocks.
- * Results showed that MIT and IE respond differently to the insertion factors; the first insertion emphasized thread forming for IE, while subsequent insertions highlighted thread tightening for MIT, indicating that both metrics are essential for understanding dental implant anchorage.
Prosthetic joint infection (PJI) is one of the most devastating failures in total joint replacement (TJR). Infections are becoming difficult to treat due to the emergence of multi-drug resistant bacteria. These bacteria produce biofilm on the implant surface, rendering many antibiotics ineffective by compromising drug diffusion and penetration into the infected area.
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- The literature review focuses on wearable sensor systems designed to monitor motor symptoms in individuals with Parkinson's disease during their daily activities.
- It evaluates progress in tracking various symptoms like tremor, freezing of gait, dyskinesia, and bradykinesia using devices such as accelerometers and gyroscopes, with 27 studies meeting the criteria for home-like settings.
- While current technology effectively detects symptoms, most systems require multiple sensors on different body parts, complicating remote monitoring; thus, simpler and less intrusive designs are essential for effective use by individuals with Parkinson's disease.
Design of a surrogate for evaluation of methods to predict bone bending stiffness.
J Mech Behav Biomed Mater
December 2018
Article Synopsis
- The rising rates of osteoporosis and fractures highlight the need for effective methods to assess changes in bone mechanical properties like stiffness and strength.
- Common techniques used for this purpose include mechanical testing, various imaging methods, and advanced analytical calculations, but validating these methods is challenging due to the complexity of bone structures.
- The study introduces a new bone-surrogate designed for computed tomography compatibility, aiming to provide reliable mechanical properties for testing and improving methods that predict bone bending stiffness.
Article Synopsis
- The article examines how varying amounts of vancomycin (from 0.0 to 2.0 g) affect the antibiotic release and mechanical properties of Palacos bone cement.
- Mechanical tests conducted include four-point bending, compression, and fracture toughness to assess the cement's strength.
- The study also tracks the vancomycin's release over 60 days and its effectiveness in eliminating common bacteria associated with orthopedic implants.
Vancomycin elution, activity and impact on mechanical properties when added to orthopedic bone cement.
J Mech Behav Biomed Mater
November 2018
Article Synopsis
- * Adding antibiotics like vancomycin to bone cement during surgery can help prevent infections, but their effectiveness depends on how well they can leach out and remain active against pathogens.
- * Higher amounts of vancomycin in the cement negatively impacted its mechanical strength, and while the antibiotic was released effectively for up to 60 days, concentrations over 0.25 g per packet successfully eradicated certain harmful bacteria like S. aureus.
Article Synopsis
- Residual equinus deformity affects up to 20% of clubfeet treated with the Ponseti method, often requiring surgical intervention to improve dorsiflexion.
- A study using MRI and 3D modeling compared the ankle morphology of 10 toddlers with persistent equinus after Ponseti treatment against 16 age-matched controls to identify key differences.
- Results showed that clubfeet had significantly shallower talar neck depth and an obtuse neck angle compared to controls, which may lead to anterior ankle impingement and restricted movement.
Biomechanical studies of the elongated canine tooth of animals are few, and thus our understanding of mechanical and physical properties of animal teeth is limited. The objective of the present study was to evaluate the influence of force direction on fracture resistance and fracture pattern of canine teeth in an ex vivo dog cadaver model. Forty-five extracted canine teeth from laboratory beagle dogs were standardized by hard tissue volume and randomly distributed among 3 force direction groups.
View Article and Find Full Text PDFCharacterization of the quasi-static and viscoelastic properties of orthopaedic bone cement at the macro and nanoscale.
J Biomed Mater Res B Appl Biomater
August 2017
Article Synopsis
- Acrylic bone cement is used in total joint replacements to secure implants to bone and has special properties like creep and stress relaxation, which are important for its performance.
- This study aimed to compare mechanical properties of two types of bone cement (Palacos and Simplex) using both traditional methods (like three-point bending) and a newer method called nanoindentation, which is more sensitive and requires smaller samples.
- The findings showed that results from nanoindentation often indicated higher mechanical properties compared to traditional methods, suggesting that nanoindentation could be a valuable tool for analyzing limited samples from failed implants.
Article Synopsis
- Increased bone formation is linked to mechanical loading and the signaling molecule endothelin-1, which influences osteogenesis in metastatic conditions.
- A study tested the effects of mechanical loading and big endothelin-1 on bovine trabecular bone, assessing outcomes through various measurements like elastic modulus and bone formation rates.
- Results showed significant increases in bone formation rates and mineralization in the group exposed to both mechanical loading and big endothelin-1, while no significant differences were found when comparing individual treatments to the control group.