How do implant type, head size and AVN lesion size affect the likelihood of femoral head collapse following hip fixation?

Alisdair MacLeod, Michael Whitehouse, Harinderjit Gill, Elise Pegg

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Femoral head collapse due to avascular necrosis (AVN) is a relatively rare occurrence following intertrochanteric fractures; however, with over thirty-thousand intertrochanteric fractures per year in England and Wales alone, and an incidence of up to 1.16%, it is still significant. Often patients are treated with a hip fixation device, such as a sliding hip screw or X-Bolt. This study aimed to investigate the influence of three factors on the likelihood of head collapse: (1) implant type; (2) the size of the femoral head; and (3) the size of the AVN lesion.Finite element (FE) models of an intact femur, and femurs implanted with two common hip fixation designs, the Compression Hip Screw (Smith & Nephew) and the X-Bolt (X-Bolt Orthopaedics), were developed. Experimental validation of the FE models on 4th generation Sawbones composite femurs (n=5) found the peak failure loads predicted by the implanted model was accurate to within 14%. Following validation on Sawbones, the material modulus (E) was updated to represent cancellous (E=500MPa) and cortical (E=1GPa) bone, and the influence of implant design, head size, and AVN was examined. Four head sizes were compared: mean male (48.4 mm) and female (42.2 mm) head sizes ± two standard deviations. A conical representation of an AVN lesion with a lower modulus (1MPa) was created, and four different radii were studied. The risk of head collapse was assessed from (1) the critical buckling pressure and (2) the peak failure stress.The likelihood of head collapse was reduced by implantation of either fixation device. Smaller head sizes and greater AVN lesion size increased the risk of femoral head collapse. These results indicate the treatment of intertrochanteric fractures with a hip fixation device does not increase the risk of head collapse; however, patient factors such as small head size and AVN severity significantly increase the risk.
Original languageEnglish
Title of host publicationBone and Joint Journal Orthopaedic Proceedings
Pages38-38
Volume98 (Supp 16)
DOIs
Publication statusPublished - 21 Feb 2018
EventThe British Orthopaedic Research Society Annual Conference - Glasgow, UK United Kingdom
Duration: 5 Sep 20166 Sep 2016
http://www.borsoc.org.uk/docs/BORS%20programme%20Glasgow%202016.pdf

Conference

ConferenceThe British Orthopaedic Research Society Annual Conference
Abbreviated titleBORS
CountryUK United Kingdom
CityGlasgow
Period5/09/166/09/16
Internet address

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Thigh
Hip
Necrosis
Head
Hip Fractures
Femur
Equipment and Supplies
Wales
England
Orthopedics
Pressure
Bone and Bones
Incidence

Cite this

How do implant type, head size and AVN lesion size affect the likelihood of femoral head collapse following hip fixation? / MacLeod, Alisdair; Whitehouse, Michael; Gill, Harinderjit; Pegg, Elise.

Bone and Joint Journal Orthopaedic Proceedings. Vol. 98 (Supp 16) 2018. p. 38-38.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

MacLeod, A, Whitehouse, M, Gill, H & Pegg, E 2018, How do implant type, head size and AVN lesion size affect the likelihood of femoral head collapse following hip fixation? in Bone and Joint Journal Orthopaedic Proceedings. vol. 98 (Supp 16), pp. 38-38, The British Orthopaedic Research Society Annual Conference, Glasgow, UK United Kingdom, 5/09/16. https://doi.org/10.1302/1358-992X.98BSUPP_16.BORS2016-038
MacLeod, Alisdair ; Whitehouse, Michael ; Gill, Harinderjit ; Pegg, Elise. / How do implant type, head size and AVN lesion size affect the likelihood of femoral head collapse following hip fixation?. Bone and Joint Journal Orthopaedic Proceedings. Vol. 98 (Supp 16) 2018. pp. 38-38
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title = "How do implant type, head size and AVN lesion size affect the likelihood of femoral head collapse following hip fixation?",
abstract = "Femoral head collapse due to avascular necrosis (AVN) is a relatively rare occurrence following intertrochanteric fractures; however, with over thirty-thousand intertrochanteric fractures per year in England and Wales alone, and an incidence of up to 1.16{\%}, it is still significant. Often patients are treated with a hip fixation device, such as a sliding hip screw or X-Bolt. This study aimed to investigate the influence of three factors on the likelihood of head collapse: (1) implant type; (2) the size of the femoral head; and (3) the size of the AVN lesion.Finite element (FE) models of an intact femur, and femurs implanted with two common hip fixation designs, the Compression Hip Screw (Smith & Nephew) and the X-Bolt (X-Bolt Orthopaedics), were developed. Experimental validation of the FE models on 4th generation Sawbones composite femurs (n=5) found the peak failure loads predicted by the implanted model was accurate to within 14{\%}. Following validation on Sawbones, the material modulus (E) was updated to represent cancellous (E=500MPa) and cortical (E=1GPa) bone, and the influence of implant design, head size, and AVN was examined. Four head sizes were compared: mean male (48.4 mm) and female (42.2 mm) head sizes ± two standard deviations. A conical representation of an AVN lesion with a lower modulus (1MPa) was created, and four different radii were studied. The risk of head collapse was assessed from (1) the critical buckling pressure and (2) the peak failure stress.The likelihood of head collapse was reduced by implantation of either fixation device. Smaller head sizes and greater AVN lesion size increased the risk of femoral head collapse. These results indicate the treatment of intertrochanteric fractures with a hip fixation device does not increase the risk of head collapse; however, patient factors such as small head size and AVN severity significantly increase the risk.",
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AU - Whitehouse, Michael

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AU - Pegg, Elise

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N2 - Femoral head collapse due to avascular necrosis (AVN) is a relatively rare occurrence following intertrochanteric fractures; however, with over thirty-thousand intertrochanteric fractures per year in England and Wales alone, and an incidence of up to 1.16%, it is still significant. Often patients are treated with a hip fixation device, such as a sliding hip screw or X-Bolt. This study aimed to investigate the influence of three factors on the likelihood of head collapse: (1) implant type; (2) the size of the femoral head; and (3) the size of the AVN lesion.Finite element (FE) models of an intact femur, and femurs implanted with two common hip fixation designs, the Compression Hip Screw (Smith & Nephew) and the X-Bolt (X-Bolt Orthopaedics), were developed. Experimental validation of the FE models on 4th generation Sawbones composite femurs (n=5) found the peak failure loads predicted by the implanted model was accurate to within 14%. Following validation on Sawbones, the material modulus (E) was updated to represent cancellous (E=500MPa) and cortical (E=1GPa) bone, and the influence of implant design, head size, and AVN was examined. Four head sizes were compared: mean male (48.4 mm) and female (42.2 mm) head sizes ± two standard deviations. A conical representation of an AVN lesion with a lower modulus (1MPa) was created, and four different radii were studied. The risk of head collapse was assessed from (1) the critical buckling pressure and (2) the peak failure stress.The likelihood of head collapse was reduced by implantation of either fixation device. Smaller head sizes and greater AVN lesion size increased the risk of femoral head collapse. These results indicate the treatment of intertrochanteric fractures with a hip fixation device does not increase the risk of head collapse; however, patient factors such as small head size and AVN severity significantly increase the risk.

AB - Femoral head collapse due to avascular necrosis (AVN) is a relatively rare occurrence following intertrochanteric fractures; however, with over thirty-thousand intertrochanteric fractures per year in England and Wales alone, and an incidence of up to 1.16%, it is still significant. Often patients are treated with a hip fixation device, such as a sliding hip screw or X-Bolt. This study aimed to investigate the influence of three factors on the likelihood of head collapse: (1) implant type; (2) the size of the femoral head; and (3) the size of the AVN lesion.Finite element (FE) models of an intact femur, and femurs implanted with two common hip fixation designs, the Compression Hip Screw (Smith & Nephew) and the X-Bolt (X-Bolt Orthopaedics), were developed. Experimental validation of the FE models on 4th generation Sawbones composite femurs (n=5) found the peak failure loads predicted by the implanted model was accurate to within 14%. Following validation on Sawbones, the material modulus (E) was updated to represent cancellous (E=500MPa) and cortical (E=1GPa) bone, and the influence of implant design, head size, and AVN was examined. Four head sizes were compared: mean male (48.4 mm) and female (42.2 mm) head sizes ± two standard deviations. A conical representation of an AVN lesion with a lower modulus (1MPa) was created, and four different radii were studied. The risk of head collapse was assessed from (1) the critical buckling pressure and (2) the peak failure stress.The likelihood of head collapse was reduced by implantation of either fixation device. Smaller head sizes and greater AVN lesion size increased the risk of femoral head collapse. These results indicate the treatment of intertrochanteric fractures with a hip fixation device does not increase the risk of head collapse; however, patient factors such as small head size and AVN severity significantly increase the risk.

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DO - 10.1302/1358-992X.98BSUPP_16.BORS2016-038

M3 - Conference contribution

VL - 98 (Supp 16)

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EP - 38

BT - Bone and Joint Journal Orthopaedic Proceedings

ER -