The elastic properties of morsellised cortico-cancellous bone graft are dependent on its prior loading

Phillips, A.T.M.; Pankaj, Pankaj; Brown, Dennis T.; Oram, T.Z.; Howie, C. R.; Usmani, Asif

doi:10.1016/j.jbiomech.2005.03.032

Cited by 12 publications

(14 citation statements)

References 24 publications

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“…13,19 Our stiffness measurements during the twentieth impaction, E imp , 66-97 MPa, were within the range reported by others. 19 Dynamic stiffness measurements, however, are influenced by the fluid phase, rendering the measurements sensitive to the loading rate and that of fluid dissipation, which is affected by the geometry and permeability of the graft and its environment. By characterizing MCB stiffness in creep, we were able to account for fluid effects and, therefore, to measure the response of the graft particles to the applied load.…”

Section: Discussionsupporting

confidence: 86%

“…A wide range of stiffness values have been reported for fresh frozen, impacted MCB: 3-135 MPa. [11][12][13][14][15][16][17][18][19][20]23 This large range of results is likely due to variation in the test methods among the studies. Our postimpaction MCB stiffness Figure 7.…”

Section: Discussionmentioning

confidence: 99%

“…12,17,18 Studies that measured stiffness immediately after impaction, without allowing the graft to recoil, consistently reported higher stiffness: 10-70 MPa. 19,20 Similarly, stiffness measured during a loading ramp ranged 40-70 MPa 15,16 and during impaction or cyclic loading, 15-135 MPa. 13,19 Our stiffness measurements during the twentieth impaction, E imp , 66-97 MPa, were within the range reported by others.…”

Section: Discussionmentioning

confidence: 99%

“…The mechanisms through which this migration occurs are not yet fully understood, but the MCB region might be critical because its stiffness is lower than that of the other materials in the reconstruction. Compressive stiffness between 3 and 135 MPa has been reported for impacted MCB [11][12][13][14][15][16][17][18][19][20] compared with 2, 17, and 220 GPa for the cement, cortical bone, and stem, respectively. 21 The role of the graft in the migration process was examined in a clinical study that reported an apparent relationship between migration and the density of the graft bed.…”

Section: Introductionmentioning

confidence: 99%

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Impaction allografting—The effect of impaction force and alternative compaction methods on the mechanical characteristics of the graft

et al. 2008

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Revision total hip replacement with impaction allografting has an attractive potential for restoring bone stock, however, fractures and implant migration remain problematic. Postoperative graft deformation is believed to contribute to migration. Under compressive loading, the fluid in the graft takes up the load initially through fluid pressure that dissipates over time. Given the short duration of an impaction, we proposed two novel graft compaction techniques that allow more time for fluid flow: holding a compression force constant for 90 s (creep technique), and cycles of compressing the graft to a given force and then holding the displacement constant (cyclic relaxation technique). This study examined the effect of the impaction force on the density and mechanical characteristics of the graft, and explored the potential benefit of the proposed alternative compaction techniques. Increasing the impaction force from "low" to "high" increased graft density by 41%, and this translated to stiffness and shear strength increases of 93 and 164%, respectively. The creep technique improved the stiffness and shear strength by 14 and 16%, respectively, when compared with impaction, while the cyclic relaxation technique did not improve the mechanical properties. Although the creep technique could potentially provide a lower risk of intraoperative fracture over the use of larger impaction forces, any clinical benefit of the creep technique warrants further investigation. Our results point to the importance of maximizing impaction forces in impaction allografting surgery.

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Section: Discussionsupporting

confidence: 86%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Impaction allografting—The effect of impaction force and alternative compaction methods on the mechanical characteristics of the graft

et al. 2008

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“…The authors believe that mechanical preparation of the bone layer affects the possibility of loading without the risk of loosening the artificial acetabulum. Many authors point out that the elastic properties of bone grafts are determined by their primary impacting [8].…”

Section: Resultsmentioning

confidence: 99%

Stability Studies of Acetabular Cup in Artificial Hip Joint Models

Płomiński¹,

Watral²

2017

J Bone Res

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Purpose:The article presents the results of stress testing of an artificial cup fixed in a model containing a fragment of an animal hip. The main objective of the study was to determine the effect of the angle of cup fixing on its stability. Methods:In the model investigated, a polyethylene acetabulum was cemented on a base made of impacted frozen bone grafts by experienced orthopedists. In this way, the test conditions were similar to those in clinical trials. The model prepared in this manner was subject to cyclic loading followed by a trial to tear off the cup, performed on an INSTRON machine. Results:As a result, a set of characteristics was obtained which illustrate the dependency of acetabular cup displacement as a function of the shearing force for different inclination angles of cup fixing and varying thickness of graft layers. Conclusion:One conclusion was that the fixing angle of 60 degrees in relation to the vertical axis Z m of the global coordinate system provided significantly better stability that the angle of 30 degrees. It was also noted that the layer thickness of frozen grafts was another factor influencing the value of the shearing force applied to the cup.

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Patient‐specific modelling of bone and bone‐implant systems: the challenges

Pankaj

2012

Numer Methods Biomed Eng

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In the past three decades, finite element (FE) modelling has provided considerable understanding to the area of musculoskeletal biomechanics. However, most of this understanding has been generated using generic, standardised or idealised models. Patient-specific modelling (PSM) is almost never used for making clinical decisions. Imaging technologies have made it possible to create patient-specific geometries and FE meshes for modelling. While these have brought us closer to PSM, several challenges associated with the definition of material properties, loads, boundary conditions and interaction between components still need to be overcome. This study reviews the current status of PSM with respect to defining material behaviour and prescribing boundary conditions and interactions. With regard to the constitutive modelling of bone, it is seen that imaging is being increasingly used to define elastic properties (isotropic as well as anisotropic). However, the post-elastic and time-dependent behaviour, important for several modelling situations, is mostly obtained from in vitro experiments. Strain-based plasticity, not commonly available in FE codes, appears to have the potential of reducing an element of patient-specificity in modelling the yielding behaviour of bone. PSM of real boundary conditions that include muscles and ligaments continues to remain a challenge; many clinically relevant questions can be, however, answered without their inclusion. Simulation techniques to undertake PSM of interactions between bone and uncemented implants are available. Interference fit employed in both joint replacement fracture treatments induces considerable preload whose inclusion in models is important for the prediction of interface behaviour.

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The elastic properties of morsellised cortico-cancellous bone graft are dependent on its prior loading

Cited by 12 publications

References 24 publications

Impaction allografting—The effect of impaction force and alternative compaction methods on the mechanical characteristics of the graft

Impaction allografting—The effect of impaction force and alternative compaction methods on the mechanical characteristics of the graft

Stability Studies of Acetabular Cup in Artificial Hip Joint Models

Patient‐specific modelling of bone and bone‐implant systems: the challenges

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