Bone Strain Research Articles

Experimental and finite element analyses of bone strains in the growing rat tibia induced by in vivo axial compression

Experimental and finite element analyses of bone strains in the growing rat tibia induced by in vivo axial compression

Voxel-based micro-finite element analysis of dental implants in a human cadaveric mandible: Tissue modulus assignment and sensitivity analyses

The success of dental implant treatment is related to the complex 3-dimensional (3D) biomechanics of the implant-bone interaction. In this work, 3D numerical models are built based on micro X-ray computed tomography (micro-CT) images of a cadaveric mandible specimen with implants placed in it. The simulation results show that the computed strain values in bone are sensitive to the uncertainties in trabecular tissue modulus and fairly insensitive to the modulus of implants and teeth and the detailed geometry of the fixed boundary condition. A bone-volume-fraction (BV/TV) based method is proposed to assign the tissue moduli of bone elements based on their BV/TV to increase the connectivity of the mesh and to improve the accuracy of the models. These models are potentially powerful for calculating the 3D full-field bone strain under implant loading, enabling in silico testing of different implant designs, but demand validation of the models. The computed results reveal high strain concentration at bone-implant contact areas and, more importantly, in the buccal (lip-side) bone that is not making contact with the implant. The computed strain concentration patterns are found to be in good agreement with the observations from our prior experiments using 3D full-field mechanical testing coupled with micro-CT and digital volume correlation. The buccal bone is thinner and less stiff than other areas of bone and is also the commonly observed area of bone resorption after dental implant treatment.

A novel training-free method for real-time prediction of femoral strain

Surrogate methods for rapid calculation of femoral strain are limited by the scope of the training data. We compared a newly developed training-free method based on the superposition principle (Superposition Principle Method, SPM) and popular surrogate methods for calculating femoral strain during activity. Finite-element calculations of femoral strain, muscle, and joint forces for five different activity types were obtained previously. Multi-linear regression, multivariate adaptive regression splines, and Gaussian process were trained for 50, 100, 200, and 300 random samples generated using Latin Hypercube (LH) and Design of Experiment (DOE) sampling. The SPM method used weighted linear combinations of 173 activity-independent finite-element analyses accounting for each muscle and hip contact force. Across the surrogate methods, we found that 200 DOE samples consistently provided low error (RMSE < 100 µε), with model construction time ranging from 3.8 to 63.3 h and prediction time ranging from 6 to 1236 s per activity. The SPM method provided the lowest error (RMSE = 40 µε), the fastest model construction time (3.2 h) and the second fastest prediction time per activity (36 s) after Multi-linear Regression (6 s). The SPM method will enable large numerical studies of femoral strain and will narrow the gap between bone strain prediction and real-time clinical applications.

Comparison of the periimplant bone stress distribution on three fixed partial supported prosthesis designs under different loading. A 3D finite element analysis

ABSTRACTDespite high success and survival rates of implant-supported prosthesis therapy, biomechanical complications such as periimplant bone resorption continue to exist due to occlusal overloading. The purpose of this article is to analyse and compare the influence of bone density, direction and distribution of the occlusal load and the design of three-unit implant-supported prostheses. Three-dimensional finite element analysis study was developed to evaluate the influence on the periimplant bone stress distribution of three different designs of a 3-unit bridge supported by two implants (intermediate pontic, tilted implant, cantilever pontic), two different bone qualities (D3 and D4), and different loading directions (axial and non-axial) and distributions (uniform and non-uniform). Bridge configuration with intermediate pontic and parallel implants presents the lowest periimplant stress, whereas the highest stress was found on the tilted implant bridge. Bone D3 is biomechanically more favourable than D4. Non-axial and uniform loading conditions produce more periimplant stress. Distal cantilever and 45° convergent distal tilted implant are the second and third treatment options on a posterior three-unit rehabilitation. Lightening occlusal contacts on the pontic and avoiding non-axial loading, reduce periimplant bone stress. Bone D4 increases periimplant bone strain.

Predictions of Birmingham hip resurfacing implant offset - In vitro and numerical models

The number of hip resurfacing arthroplasty procedures has declined dramatically in recent years, for reasons related to the survival rate. Some studies suggest that metal particles are the main critical problem, but do not specify the effect of femoral position on the failure rate. The present study aims to analyze whether the positioning of the resurfacing head implant is important in the distribution of bone strains and in the risk of fracture of the femur.Three in vitro experimental models received the Birmingham hip resurfacing implant to replicate the total hip joint. The resurfacing head of the implanted models was placed in three different offset positions: in a positive offset, with the same femoral head center and in a negative offset.The numerical models were validated by correlating numerical and experimental results. Comparing experimental results from the implanted and intact femurs highlights a strain increase of up to 48% in the proximal medial femur region for positive offset and up to 18% in the neutral position. A reduction of 72% for negative offset (valgus position) was also measured experimentally.A significant change in strain distributions was observed with a resurfacing hip system and increased risk of neck fracture was found using the resurfacing head in positive offset. The iliac bone presents a high decrease in strains that will induce bone loss in the long term. Among the offset positions tested, results suggest that the negative offset (valgus position) and the natural position are the best equilibrated for better long-term results.

The effect of malalignment on proximal tibial strain in fixed-bearing unicompartmental knee arthroplasty: A comparison between metal-backed and all-polyethylene components using a validated finite element model.

ObjectivesElevated proximal tibial bone strain may cause unexplained pain, an important cause of unicompartmental knee arthroplasty (UKA) revision. This study investigates the effect of tibial component alignment in metal-backed (MB) and all-polyethylene (AP) fixed-bearing medial UKAs on bone strain, using an experimentally validated finite element model (FEM).MethodsA previously experimentally validated FEM of a composite tibia implanted with a cemented fixed-bearing UKA (MB and AP) was used. Standard alignment (medial proximal tibial angle 90°, 6° posterior slope), coronal malalignment (3°, 5°, 10° varus; 3°, 5° valgus), and sagittal malalignment (0°, 3°, 6°, 9°, 12°) were analyzed. The primary outcome measure was the volume of compressively overstrained cancellous bone (VOCB) < -3000 µε. The secondary outcome measure was maximum von Mises stress in cortical bone (MSCB) over a medial region of interest.ResultsVarus malalignment decreased VOCB but increased MSCB in both implants, more so in the AP implant. Varus malalignment of 10° reduced the VOCB by 10% and 3% in AP and MB implants but increased the MSCB by 14% and 13%, respectively. Valgus malalignment of 5° increased the VOCB by 8% and 4% in AP and MB implants, with reductions in MSCB of 7% and 10%, respectively. Sagittal malalignment displayed negligible effects. Well-aligned AP implants displayed greater VOCB than malaligned MB implants.ConclusionAll-polyethylene implants are more sensitive to coronal plane malalignments than MB implants are; varus malalignment reduced cancellous bone strain but increased anteromedial cortical bone stress. Sagittal plane malalignment has a negligible effect on bone strain.Cite this article: I. Danese, P. Pankaj, C. E. H. Scott. The effect of malalignment on proximal tibial strain in fixed-bearing unicompartmental knee arthroplasty: A comparison between metal-backed and all-polyethylene components using a validated finite element model. Bone Joint Res 2019;8:55–64. DOI: 10.1302/2046-3758.82.BJR-2018-0186.R2.

A novel nonosteocytic regulatory mechanism of bone modeling.

Osteocytes, cells forming an elaborate network within the bones of most vertebrate taxa, are thought to be the master regulators of bone modeling, a process of coordinated, local bone-tissue deposition and removal that keeps bone strains at safe levels throughout life. Neoteleost fish, however, lack osteocytes and yet are known to be capable of bone modeling, although no osteocyte-independent modeling regulatory mechanism has so far been described. Here, we characterize a novel, to our knowledge, bone-modeling regulatory mechanism in a fish species (medaka), showing that although lacking osteocytes (i.e., internal mechanosensors), when loaded, medaka bones model in mechanically directed ways, successfully reducing high tissue strains. We establish that as in mammals, modeling in medaka is regulated by the SOST gene, demonstrating a mechanistic link between skeletal loading, SOST down-regulation, and intense bone deposition. However, whereas mammalian SOST is expressed almost exclusively by osteocytes, in both medaka and zebrafish (a species with osteocytic bones), SOST is expressed by a variety of nonosteocytic cells, none of which reside within the bone bulk. These findings argue that in fishes (and perhaps other vertebrates), nonosteocytic skeletal cells are both sensors and responders, shouldering duties believed exclusive to osteocytes. This previously unrecognized, SOST-dependent, osteocyte-independent mechanism challenges current paradigms of osteocyte exclusivity in bone-modeling regulation, suggesting the existence of multivariate feedback networks in bone modeling—perhaps also in mammalian bones—and thus arguing for the possibility of untapped potential for cell targets in bone therapeutics.

Uncertainties of synchrotron microCT-based digital volume correlation bone strain measurements under simulated deformation

Digital Volume Correlation (DVC) is used to measure internal displacements and strains in bone. Recent studies have shown that Synchrotron radiation micro-computed tomography (SR-microCT) can improve the accuracy and precision of DVC. However, only zero-strain or virtually-moved test have been used to quantify the DVC uncertainties, leading to potential underestimation of the measurement errors.In this study, for the first time, the uncertainties of a global DVC approach have been evaluated on repeated SR-microCT scans of bovine cortical bone (voxel size: 1.6 μm), which were virtually deformed for different magnitudes and along different directions.The results showed that systematic and random errors of the normal strain components along the deformation direction were higher than the errors along unstrained directions. The systematic percentage errors were smaller for larger virtual deformations. The random percentage error was in the order of 10% of the virtual deformation. However, higher errors were localized at the boundary of the volumes of interest, perpendicular to the deformation direction. When only the central region of the samples was considered (100 µm layers removed from the borders where the deformation was applied), the errors in the direction of virtual deformation were comparable to the errors in the unstrained directions.In conclusion, the method presented to estimate the uncertainties of DVC is suitable for testing anisotropic specimens as cortical bone. The good agreement between the uncertainties in measurements of strain components obtained with this approach and with the simpler zero-strain-test suggests that the latter is adequate in the tested deformation scenarios.

Anatomic grooved stem mitigates strain shielding compared to established total hip arthroplasty stem designs in finite-element models

Aseptic loosening remains a major problem for uncemented femoral components in primary total hip arthroplasty (THA). Ideally, bone adaptation after THA manifests minimally and local bone density reduction is widely avoided. Different design features may help to approximate initial, post-THA bone strain to levels pre-THA. Strain-shielding effects of different SP-CL stem design features are systematically analyzed and compared to CLS Spotorno and CORAIL using finite element models and physiological musculoskeletal loading conditions. All designs show substantial proximal strain-shielding: 50% reduced medial surface strain, 40–50% reduction at lateral surface, >120 µm/m root mean square error (RMSE) compared to intact bone in Gruen zone 1 and >60 µm/m RMSE in Gruen zones 2, 6, and 7. Geometrical changes (ribs, grooves, cross sections, stem length, anatomic curvature) have a considerable effect on strain-shielding; up to 20%. Combinations of reduced stem stiffness with larger proximal contact area (anatomically curved, grooves) lead to less strain-shielding compared to clinically established implant designs. We found that only the combination of a structurally flexible stem with anatomical curvature and grooves improves strain-shielding compared to other designs. The clinical implications in vivo of this initial strain-shielding difference are currently under evaluation in an ongoing clinical analysis.

The Effect of Formalin Preservation Time and Temperature on the Material Properties of Bovine Femoral Cortical Bone Tissue.

Literature has reported controversial findings on whether formalin affected bone properties, or not, especially when different preservation time durations and temperatures were involved. Hence, accurately and systematically quantifying the effect of formalin on the mechanical properties of bone using a large dataset is crucial for assessing biomechanical responses based on fixed specimens. A total of 154 longitudinal and 149 transverse cuboid-shaped (12mm × 2mm × 0.5mm) specimens from themidsection of 12 bovine femora from six bovines were prepared and assigned to ten groups, including fresh-frozen, formalin-preserved at 25°C for 4weeks and 8weeks, and formalin-preserved at 4°C for 4weeks and 8weeks. All specimens underwent quasi-static three-point bending tests with a loading rate of 0.02mm/s. The Young's modulus, yield stress, yield strain, tangent modulus, effective plastic strain, ultimate stress, and toughness were calculated by optimizing the material parameters to make the force-displacement curve of the finite element prediction consistent with the experimental curve, combined with specimen-specific finite element models. Preservation time and temperature both had significant effects on the Young's modulus, yield stress, effective plastic strain, yield strain and ultimate stress of cortical bone (p < 0.05). The Young's modulus, yield stress, and ultimate stress of longitudinal specimens decreased significantly with the increase of preservation time, and the yield strain increased significantly. As the preservation temperature increases, the Young's modulus of the transverse sample decreased significantly, and the yield strain increased significantly. The preservation time mainly affects the longitudinal specimens, while the preservation temperature mainly affects the transverse specimens. Formalin preservation of bovine femoral cortical bones at alower temperature and less than 4weeks is recommended for biomechanical testing.

Effects of implant orientation and implant material on tibia bone strain, implant-bone micromotion, contact pressure, and wear depth due to total ankle replacement.

The aim of this study is to investigate the effects of implant orientation and implant material on tibia bone strain, implant-bone micromotion, maximum contact pressure, and wear depth at the articulating surface due to total ankle replacement. Three-dimensional finite element models of intact and implanted ankle were developed from computed tomography scan data. Four implanted models were developed having varus and valgus orientations of 5° and 10°, respectively. In order to determine the effect of implant material combination on tibia bone strain, micromotion, contact pressure, and wear depth, three other finite element models were developed having a different material combination of the implant. Dorsiflexion, neutral, and plantarflexion positions were considered as applied loading condition, along with muscle force and ligaments. Implant orientation alters the strain distribution in tibia bone. Strain shielding was found to be less in the case of the optimally positioned implant. Apart from the strain, implant orientation also affects implant-bone micromotion, contact pressure, and wear depth. Implant materials have less influence on tibia bone strain and micromotion. However, wear depth was reduced when ceramic and carbon fibre-reinforced polyetheretherketone material combination was used. Proper orientation of the implant is important to reduce the strain shielding. The present result suggested that ceramic can be used as an alternative to metal and carbon fibre-reinforced polyetheretherketone as an alternative to ultra-high molecular weight polyethylene to reduce wear, which would be beneficial for long-term success and fixation of the implant.

Anisotropy of elastic modulus and hydroxyapatite crystal strain in diaphyseal cortical bone

Anisotropy of elastic modulus and hydroxyapatite crystal strain in diaphyseal cortical bone

Comparative evaluation of implant designs: Influence of diameter, length, and taper on stress and strain in the mandibular segment—A three-dimensional finite element analysis

Introduction:Success or failure of dental implants depends on the amount of stress transferred to the surrounding bone. Increased amount of loading to the bone through implant cause failure, whereas decrease in the amount of loading to the bone causes improved success rate of implants. Biomechanical interaction between implant and bone decides the long-term function or prognosis of dental implant system.Aim and Objectives:The aims of this study were to evaluate the influence of implant length and diameter on stress distribution, to understand the stress distribution around bone–implant interface, and to understand the response of bone under axial and non-axial loading conditions.Materials and Methods:Finite element three-dimensional mandibular model was made using cone beam computed tomography of patient with completely edentulous mandible, and in that model five posterior bone segments were selected. NobelReplace Select Tapered implants with diameters and lengths 3.5 × 10 mm, 4.3 × 10 mm, 3.5 × 11.5 mm, and 4.3 × 11.5 mm, respectively were selected and three dimensionally modeled using Creo 2.0 Parametric Pro/E software. Bone and implant models were assembled as 20 models and finite element analysis was performed using ANSYS Workbench v17.0 under axial and non-axial loads.Result:Under axial and non-axial loads, 3.5 × 10 mm implant showed maximum von Mises stress and strain in both cortical and cancellous bone whereas implant with diameter and length 4.3 × 11.5 mm showed minimum von Mises stress and strain in both cortical and cancellous bone.Conclusion:In axial and non-axial loads, amount of stress distribution around implant–bone interface is influenced by diameter and length of implant in cortical and cancellous bone, respectively. Increased diameter of the implant produces the minimum stress in cortical bone. Increased length of the implant produces the minimum stress in cancellous bone.

Stress and Strain Distribution Patterns in Bone around Tissue- and Bone-Level Implant-Supported Mandibular Overdentures Using Three-Dimensional Finite-Element Analysis.

Our aim is to investigate the effect of implant placement in two positions (bone level and tissue level) on stress and strain distribution around mandibular implant overdentures. We use two models of mandibular overdentures. Taper implants are inserted and collimated between the lateral and canine teeth. All structures are scanned, digitized, and three-dimensioned (3D) model designed. We apply a vertical load of 100 N simultaneously on the central fossa of the mandibular first molar of the two models (bone- and tissue-level implant). Stress and strain values are obtained using 3D finite-element analysis (FEA). In comparison to the tissue-level model, bone-level implants can reduce overdenture movement and tension by 0.8 μm. The results of this study show that using bone-level implants can reduce tension on the prosthesis part of the overdenture and the bone around the implants as well as on the movement of the distal end of the mandibular overdenture. We found that bone strain occurred around implants within physiological limits in model 1 (bone level) compared to model 2 (tissue level). This shows that the distribution of physical forces in bone-level implants generally produces better results than those of issue-level implants. However, more research on the subject is needed.

Morse taper performance: A finite element analysis study

OBJECTIVES:To evaluate and compare the magnitude and distribution of stresses generated on implants, abutments and first molar metal-ceramic crowns using finite element analysis.METHODS:Preliminary three-dimensional models were created using the computer-aided design software SolidWorks. Stress and strain values were observed for two distinct virtual models: model 1 - Morse taper and solid abutment; model 2 - Morse taper and abutment with screw. A load (250 N) was applied to a single point of the occlusal surface at 15° to the implant long axis. Von Mises stresses were recorded for both groups at four main points: 1) abutment-retaining screws; 2) abutment neck; 3) cervical bone area; 4) implant neck.RESULTS AND CONCLUSION:Model 1 showed a higher stress value (1477.5 MPa) at the abutment-retaining screw area than the stresses found in model 2 (1091.1 MPa for the same area). The cervical bone strain values did not exceed 105 µm for either model.

Biomechanical analysis of 4 types of short dental implants in a resorbed mandible

Statement of problemShort implants have been increasingly used in the aging society. However, studies which explain the difference of stress distribution according to different connections in short implant treatment are scarce. PurposeThe purpose of this finite element (FE) analysis was to evaluate the stress and strain distribution of short implants and surrounding bone under static and cyclic loading conditions with 4 different connections. Material and methodsThree-dimensional models of 4 types of implant systems were considered: internal tissue level, internal tissue level wide, internal bone level (IB), and external bone level. Each system had different types of abutment, implant, and screw with the resorbed mandibular segment of the bone block. Static FE analysis was performed under external loads of 200 N (vertical or 30-degree oblique) to each cusp tip. The strain distributions of the peri-implant bone and von Mises stress fields in the abutment, implant, and screw were evaluated. Based on the static FE results, a computational fatigue analysis was performed to predict the risk of fracture caused by fatigue accumulation of repetitive mastication. ResultsBone tissues in fatigue failure level (greater than 4000 με) were observed in the alveolar ridge and the plateaus close to the implant apex in all situations. Under the oblique loading condition, the total volume of the bone tissue in hypertrophy and fatigue failure levels (greater than 2500 με) was the largest at IB and the smallest at external bone level. Among the 4 situations, the highest stress occurred in the abutment (506.9 MPa) and implant (311 MPa) of IB. In fatigue analysis, fracture was only predicted in the IB abutment model (588 301 cycles), and cracking occurred in the lingual direction, where stress concentration occurred when the oblique load was applied. ConclusionsThe abutment of IB showed the highest stress of the implant component, and internal tissue level model showed the highest strain of bone. In all groups, the bone strain values mostly appeared within physiologic capacity (under 4000 με). Various mechanical situations should be considered when using internal bone-level connections in short implants for replacing posterior teeth.

Computational investigation of ultrastructural behavior of bone using a cohesive finite element approach.

Bone ultrastructure at sub-lamellar length scale is a key structural unit in bone that bridges nano- and microscale hierarchies of the tissue. Despite its influence on bulk response of bone, the mechanical behavior of bone at ultrastructural level remains poorly understood. To fill this gap, in this study, a two-dimensional cohesive finite element model of bone at sub-lamellar level was proposed and analyzed under tensile and compressive loading conditions. In the model, ultrastructural bone was considered as a composite of mineralized collagen fibrils (MCFs) embedded in an extrafibrillar matrix (EFM) that is comprised of hydroxyapatite (HA) polycrystals bounded via thin organic interfaces of non-collagenous proteins (NCPs). The simulation results indicated that in compression, EFM dictated the pre-yield deformation of the model, then damage was initiated via relative sliding of HA polycrystals along the organic interfaces, and finally shear bands were formed followed by delamination between MCF and EFM and local buckling of MCF. In tension, EFM carried the most of load in pre-yield deformation, and then an array of opening-mode nano-cracks began to form within EFM after yielding, thus gradually transferring the load to MCF until failure, which acted as crack bridging filament. The failure modes, stress-strain curves, and in situ mineral strain of ultrastructural bone predicted by the model were in good agreement with the experimental observations reported in the literature, thus suggesting that this model can provide new insights into sub-microscale mechanical behavior of bone.

Effect of implant number and height on the biomechanics of full arch prosthesis

Aim: Aim: The goal of this study was to clarify the stress distribution in a full arch prosthesis according to the implant number and height in order to guide the clinical choice during planning. Methods: A computational analysis was performed to analyze the stress distribution in implants and bone tissue according to implant number (3, 4 or 5) and height (5, 8, 11 mm). A model of a jaw with polyurethane properties to simulate bone tissue was created through the Rhinoceros software (version 5.0 SR8, McNeel North America, Seattle, WA, USA). The titanium bar was fixed to the implant through a retention screw. The final geometry was exported in STEP format to ANSYS (ANSYS 15.0, ANSYS Inc., Houston, USA) and all materials were considered homogeneous, isotropic and linearly elastic. To assess distribution of stress forces, an axial load (200 N) was applied on the cantilever. Results in Von-Mises stress and strain criteria’s were obtained for implants and bone, respectively. Qualitative and quantitative evaluations were performed. Results: The implant number and height influenced the prosthesis biomechanics, with more von-Mises stress and bone strain concentration for combination of 3 implants with 5 mm. Conclusion: It was concluded that higer length and more quantity of implant supporting a full arch prosthesis promoted less stress concentration during the simulated load. Decreasing the number of implants in rehabilitation is more harmful than decreasing their length for the stress and strain distribution.

Finite element analysis of different configurations of fully threaded cannulated screw in the treatment of unstable femoral neck fractures

BackgroundIn the present study, we evaluated the mechanical outcome of different configurations formed by fully threaded screws and partially threaded screws in the treatment of unstable femoral neck fracture.MethodsThe Pauwels type III unstable femoral fracture and the models of the fully threaded screw and partially threaded screw were constructed in 3-matic software and UG-NX software respectively. We then assembled the different screw configurations to the fracture model separately to form the fixation models. After meshing the models’ elements, we used Abaqus software to perform the finite element analysis. Parameters of von Mises stress distribution on the screws, peak stress, displacement between fracture fragments, and model principal strains in cancellous bone were reported.ResultsOur results indicated that the peak von Mises stresses of screws was concentrated in the middle surface of the screw near the fracture line in each group. Peak stress value of the implants was highest in the model of triangle with posterior single screw. And the lowest stress values were observed in the triangular model. Fully threaded screw in each group underwent the most stress while partially threaded screw underwent a little bit of stress. Lowest displacement was observed in the triangular model. The volume of bone susceptible to yielding in the femoral neck region was the lowest for triangular configuration.ConclusionsFor unstable femoral neck fractures, superior results were obtained by stabilizing the fracture with triangular configuration formed by one superior partially threaded screw and two inferior fully threaded screws. This study will require clinical confirmation as to its practicality in the management of unstable femoral fractures.

Design factors of lumbar pedicle screws under bending load: A finite element analysis

Loosening and breakage of lumbar pedicle screw are the most common complications affecting the spinal stability. The design factors of the pedicle screw that may affect the fixation strength under bending load are pitch length, major diameter, thread profiles and geometry.In this study, 84 finite element (FE) models of the pedicle screw were generated having 7 pitch lengths, 3 major diameters, 2 thread profiles and 2 geometries. The assembly of pedicle screw and CT scan based half section FE model of 4th lumbar vertebra was loaded with a 200N force on the screw head which is equivalent to a bending moment of 11Nm.With triangular thread profile and cylindrical geometry, for 300% increase in pitch length (1–4mm), von Mises stress in screw and von Mises strain in bone increased by 65% and 117% respectively, for a 26% decrease in major diameter (7.6mm to 5.6mm) and correlations were proposed among screw stress (r2=0.992) or bone strain (r2=0.986), pitch length and major diameter. Similar correlations were also proposed for trapezoidal thread profile and tapered geometry (r2=0.994 for screw stress and r2=0.986 for bone strain).Hence, a combination of tapered pedicle screw with lower pitch length, higher diameter and trapezoidal thread profile may serve better under bending load for lumbar vertebral implant.