Does screw–bone interface modelling matter in finite element analyses?

MacLeod, Alisdair; Pankaj, Pankaj; Simpson, A. H. R. W.

doi:10.1016/j.jbiomech.2012.04.008

Cited by 93 publications

(76 citation statements)

References 37 publications

(38 reference statements)

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“…The screws had an external diameter of 4.5 mm and core diameters of 3.84 and 3.5 mm for locking and compression screws, respectively. Threads, with a spacing of 1.4 mm, were modelled as idealised rings rather than helical, an approach that has been previously used (Donaldson et al 2012a;MacLeod et al 2012). This assumption eased meshing and was thought to be unlikely to affect the results.…”

Section: Methodsmentioning

confidence: 99%

“…The screw -bone interaction at the entrant cortex was modelled as frictional using a standard Coulomb friction coefficient of 0.3 based on some of the recent studies (Eser et al 2010;Pessoa et al 2010;MacLeod et al 2012). As previously found with unilateral fixators (Donaldson et al 2012a), the peak strains were found to be concentrated around the screw holes on the entrant cortex; to simplify simulation the screw -bone interaction at the exit cortex was modelled as tied.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Reasons why dynamic compression plates are inferior to locking plates in osteoporotic bone: a finite element explanation

MacLeod

Simpson

Pankaj

2014

Computer Methods in Biomechanics and Biomedical Engineering

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While locking plate fixation is becoming increasingly popular for complex and osteoporotic fractures, for many indications compression plating remains the standard choice. This study compares the mechanical behaviour of the more recent locking compression plate (LCP) device, with the traditional dynamic compression plates (DCPs) in bone of varying quality using finite element modelling. The bone properties considered include orthotropy, inhomogeneity, cortical thinning and periosteal apposition associated with osteoporosis. The effect of preloads induced by compression plating was included in the models. Two different fracture scenarios were modelled: one with complete reduction and one with a fracture gap. The results show that the preload arising in DCPs results in large principal strains in the bone all around the perimeter of the screw hole, whereas for LCPs large principal strains occur primarily on the side of the screw proximal to the load. The strains within the bone produced by the two screw types are similar in healthy bone with a reduced fracture gap; however, the DCP produces much larger strains in osteoporotic bone. In the presence of a fracture gap, the DCP results in a considerably larger region with high tensile strains and a slightly smaller region with high compressive strains. These findings provide a biomechanical basis for the reported improved performance of locking plates in poorer bone quality.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Reasons why dynamic compression plates are inferior to locking plates in osteoporotic bone: a finite element explanation

MacLeod

Simpson

Pankaj

2014

Computer Methods in Biomechanics and Biomedical Engineering

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“…To further improve the model, the implant-bone interfaces (currently modeled as rigid connections), might need to be revisited. While the assump tion of a rigid connection was shown to be sufficient to model bone-screw interfaces when load-deformation responses are needed (as required in our study) [29], including friction might improve estimates of bone damage or stress shielding [29]. Simi larly, the interface between the plate and the bone did not allow for micromotion due to the rigid connection.…”

Section: Discussionmentioning

confidence: 76%

Assessing the Local Mechanical Environment in Medial Opening Wedge High Tibial Osteotomy Using Finite Element Analysis

Pauchard

Ivanov

McErlain

et al. 2015

Journal of Biomechanical Engineering

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High-tibial osteotomy (HTO) is a surgical technique aimed at shifting load away from one tibiofemoral compartment, in order the reduce pain and progression of osteoarthritis (OA). Various implants have been designed to stabilize the osteotomy and previous studies have been focused on determining primary stability (a global measure) that these designs provide. It has been shown that the local mechanical environment, characterized by bone strains and segment micromotion, is important in understanding healing and these data are not currently available. Finite element (FE) modeling was utilized to assess the local mechanical environment provided by three different fixation plate designs: short plate with spacer, long plate with spacer and long plate without spacer. Image-based FE models of the knee were constructed from healthy individuals (N = 5) with normal knee alignment. An HTO gap was virtually added without changing the knee alignment and HTO implants were inserted. Subsequently, the local mechanical environment, defined by bone compressive strain and wedge micromotion, was assessed. Furthermore, implant stresses were calculated. Values were computed under vertical compression in zero-degree knee extension with loads set at 1 and 2 times the subject-specific body weight (1 BW, 2 BW). All studied HTO implant designs provide an environment for successful healing at 1 BW and 2 BW loading. Implant von Mises stresses (99th percentile) were below 60 MPa in all experiments, below the material yield strength and significantly lower in long spacer plates. Volume fraction of high compressive strain ( > 3000 microstrain) was below 5% in all experiments and no significant difference between implants was detected. Maximum vertical micromotion between bone segments was below 200 μm in all experiments and significantly larger in the implant without a tooth. Differences between plate designs generally became apparent only at 2 BW loading. Results suggest that with compressive loading of 2 BW, long spacer plates experience the lowest implant stresses, and spacer plates (long or short) result in smaller wedge micromotion, potentially beneficial for healing. Values are sensitive to subject bone geometry, highlighting the need for subject-specific modeling. This study demonstrates the benefits of using image-based FE modeling and bone theory to fine-tune HTO implant design.

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“…However, because the same simplification conditions were assumed for all numerical models, this study can be considered as a comparative study. Moreover, MacLeod and co-workers [37] showed that the global load-deformation response is not influenced by the interface modelling approach employed; the deformation varied by less than 1% between different interaction models. However, interface modelling is found to have a considerable impact on the local stress-strain environment within the bone in the vicinity of the screws.…”

Section: Discussionmentioning

confidence: 99%

External fixator configurations in tibia fractures: 1D optimization and 3D analysis comparison

Roseiro¹,

Neto

Amaro

et al. 2014

Computer Methods and Programs in Biomedicine

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Does screw–bone interface modelling matter in finite element analyses?

Cited by 93 publications

References 37 publications

Reasons why dynamic compression plates are inferior to locking plates in osteoporotic bone: a finite element explanation

Reasons why dynamic compression plates are inferior to locking plates in osteoporotic bone: a finite element explanation

Assessing the Local Mechanical Environment in Medial Opening Wedge High Tibial Osteotomy Using Finite Element Analysis

External fixator configurations in tibia fractures: 1D optimization and 3D analysis comparison

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