Biomechanical analysis of a synthetic femur spiral fracture model: Influence of different materials on the stiffness in flexible intramedullary nailing

Kaiser, M. M.; Wessel, Lucas; Zachert, Gregor; Stratmann, Christine; Eggert, Rebecca; Gros, Nina; Schulz, Arndt P.; Kienast, B.; Rapp, Marion

doi:10.1016/j.clinbiomech.2011.01.012

Cited by 29 publications

(37 citation statements)

References 43 publications

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“…Instead of real bone, a composite bone specimen has been used that possibly cannot reproduce all in-vivo conditions, precisely. However, composite bone has been successfully used in several biomechanical studies, since inter-specimen variability is small and therefore provides more consistency among specimens than cadaveric bone [29][30][31][32][33][34][35][36][37]47]. The support structure is still not entirely representative of the in-vivo situation, where there are no rigid constraints.…”

Section: Discussionmentioning

confidence: 99%

Experimental validation of numerically predicted strain and micromotion in intact and implanted composite hemi-pelvises

Ghosh

Gupta

Dickinson

et al. 2012

Proc Inst Mech Eng H

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The failure mechanisms of acetabular prostheses may be investigated by understanding the changes in load transfer due to implantation, and analysis of the implant-bone micromotion. Computational finite element (FE) models allow detailed mechanical analysis of the implant-bone structure, but their validity must be assessed as part of a verification process before they can be employed in pre-clinical investigations. To this end, in the present study, FE models of composite hemi-pelvises, intact and implanted with an acetabular cup, were experimentally verified. Strains and implant-bone micromotions in the hemi-pelvises were compared with those predicted by the equivalent FE models. Regression analysis indicated close agreement between the measured and FE strains, with a high correlation coefficient (0.95-0.98), a low standard error of the estimate (36-53µε) and a low error in regression slope (7-11%). Measured micromotions along three orthogonal directions were small, less than 30µm, whereas the FE predicted values were found to be less than 85µm. Although the trends were similar, the observed deviations may be due to estimation of the interfacial press-fit used in the FE model, and additional artefacts in experimental micromotion measurement which are avoided in the FE model. This supports the FE model as a valid predictor of the experimentally measured strain in the composite pelvis models, confirming its suitability for further computational investigations on acetabular prostheses. 4 IntroductionLoosening of the acetabular prosthesis is responsible for the majority of failures in total hip replacement [1][2][3][4]. However, biomechanical investigations into phenomena such as the load transfer mechanism across the pelvis and the acetabular reconstruction remain relatively under-investigated as compared to the femoral component. Measurement of such phenomena across the intact and implanted bones would be a useful step forward in the analysis of acetabular failure, and to date this has commonly been evaluated using finite element (FE) analysis [5][6][7][8][9][10][11]. The validity of the FE model generation process should be assessed using quantitative comparisons between computational predictions and experimental results [Anderson et al., 2007].Researchers have investigated the strain/stress distributions in the intact pelvis by comparing experimentally measured strains with those predicted by the equivalent FE model [5,7,10]. However, all these studies featured large areas of rigid fixation, which may not be fully representative of in-vivo bone support. Moreover, there is a scarcity of experimental data on strain measurement in intact and implanted pelvises which could be used to identify potential links between changes in strain distribution due to implantation and clinical failure mechanisms [12][13][14].The initial fixation of an uncemented implant is dependent on the primary stability, which is usually indicated by the amount of micromotion at the implant-bone interface, prior to bone-ingrowth, induc...

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Section: Discussionmentioning

confidence: 99%

Experimental validation of numerically predicted strain and micromotion in intact and implanted composite hemi-pelvises

Ghosh

Gupta

Dickinson

et al. 2012

Proc Inst Mech Eng H

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“…The first is the use of a synthetic bone model that cannot precisely reproduce conditions in vivo, particularly given the lack of surrounding support tissues such as periosteum and muscle. However, this model has been used successfully in previous biomechanical studies 17,18 and provides more consistency among specimens than do cadaveric bones. 31,32 As reduction of paediatric femoral fractures is usually performed in a closed manner, we have little information about the state of the periosteum at the site of the fracture.…”

Section: Discussionmentioning

confidence: 99%

“…Steel nails were used throughout because of their superior biomechanical properties. 12,17 The distal femoral entry portals were created by a 5-mm drill 2 cm proximal to the level of the simulated physis. 21 The tips of the nails ended at the proximal end of the canal, just inferior to the greater trochanter.…”

Section: Methodsmentioning

confidence: 99%

“…Some authors have therefore recommended additional stabilisation with screws or external fixation when dealing with long spiral or other complex fractures. 6,15,16 We have previously investigated ways of modifying the materials and technique of ESIN in an attempt to improve stability: using in vitro biomechanical studies we have been able to demonstrate that stainless steel nails provide greater stability than titanium nails, 17 but we were unable to show increased stability with the use of end-caps. 18 The aim of this study was to determine the effects on stability of pre-bending the nails.…”

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confidence: 94%

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Increasing stability by pre-bending the nails in elastic stable intramedullary nailing

Kaiser¹,

Zachert²,

Wendlandt³

et al. 2012

The Journal of Bone and Joint Surgery. British volume

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Elastic stable intramedullary nailing (ESIN) is generally acknowledged to be the treatment of choice for displaced diaphyseal femoral fractures in children over the age of three years, although complication rates of up to 50% are described. Pre-bending the nails is recommended, but there are no published data to support this. Using synthetic bones and a standardised simulated fracture, we performed biomechanical testing to determine the influence on the stability of the fracture of pre-bending the nails before implantation. Standard ESIN was performed on 24 synthetic femoral models with a spiral fracture. In eight cases the nails were inserted without any pre-bending, in a further eight cases they were pre-bent to 30° and in the last group of eight cases they were pre-bent to 60°. Mechanical testing revealed that pre-bending to 60° produced a significant increase in the stiffness or stability of the fracture. Pre-bending to 60° showed a significant positive influence on the stiffness compared with unbent nails. Pre-bending to 30° improved stiffness only slightly.These findings validate the recommendations for pre-bending, but the degree of pre-bend should exceed 30°. Adopting higher degrees of pre-bending should improve stability in spiral fractures and reduce the complications of varus deformity and shortening.

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“…As stan dard rigid intramedullary in ter lock ing nails can not be ap plied in skel e tally im ma ture pa tients sev eral al ter natives to ESIN has been pro posed for treat ment of ad o les -cent fem o ral shaft frac tures. End caps and ad di tion of third nail 5 has been used to in crease sta bil ity of fix a tion of ad o les cent fe mur frac tures. An other method to treat ad o les cent fem o ral shaft frac tures is plate osteosinthesis ei ther as open plat ing or submuscular bridg ing plat ing (SMB) 6,7 .…”

Section: Introductionmentioning

confidence: 99%

Internal fixator "Mitkovic" in the treatment of fractures of femoral shaft: A possible solution for fractures in heavier children and adolescents

et al. 2015

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Back ground: Man age ment of fem o ral shaft fractures in older and heavier chil dren and ad o lescents is still chal leng ing and con tro ver sial and includes sev eral mo dal i ties of fix a tion. Aim of this study was to an a lyze sin gle cen ter ex pe ri ence in ap pli ca tion of selfdynamisable in ter nal fixator Mitkovic (SIF) for the treat ment of frac tures of fem o ral shaft in chil dren and ad o les cents. Methods: Ret ro spec tive anal y sis of data of pe di at ric and ad o les cent pa tients treated for diaphyseal frac ture in sin gle cen ter has been con ducted. Re sults: Eleven patients, with 12 fem o ral shaft frac tures were treated in ten-year-pe riod with in ter nal fixator "Mitkovic". Time to frac ture heal ing ranged from 4-12 weeks (aver age 8.9 weeks). All frac tures healed with out com plica tions. No ro ta tional or an gu lar mall-align ment was no ticed. No ex ter nal cast im mo bi li za tion was ap plied in any pa tient. Con clu sion: Selfdynamisable in ter nal fixator Mitkovic may be con sid ered as vi a ble op tion for treat ment of fem o ral frac tures in older/heavier chil dren and ad o les cents par tic u larly with un sta ble frac ture pat terns.

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Biomechanical analysis of a synthetic femur spiral fracture model: Influence of different materials on the stiffness in flexible intramedullary nailing

Cited by 29 publications

References 43 publications

Experimental validation of numerically predicted strain and micromotion in intact and implanted composite hemi-pelvises

Experimental validation of numerically predicted strain and micromotion in intact and implanted composite hemi-pelvises

Increasing stability by pre-bending the nails in elastic stable intramedullary nailing

Internal fixator "Mitkovic" in the treatment of fractures of femoral shaft: A possible solution for fractures in heavier children and adolescents

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