The Effects of Body Mass Index and Gender on Pelvic Stiffness and Peak Impact Force During Lateral Falls

Fall-related hip fractures are a substantial public health issue. Unfortunately, little is known about whether the effective stiffness of the pelvis, a critical component governing impact force during lateral falls, differs substantially across different segments of the population. The objective of this thesis was to enhance the knowledge base surrounding pelvis impact dynamics by assessing the influence of gender and body mass index (BMI) on the effective stiffness of the pelvis, and on resulting peak loads applied to the hip, during sideways falls. Towards this end I conducted pelvis release trials (in which the pelvis was suspended and suddenly released onto a force plate) with males and females with low (<22) and high (>28) BMIs.

One resonance-based (k_vibe), and three force-deflection based (k_1st, k_{combo 300}, and k_{combo opt}) methods of effective pelvic stiffness estimation were examined. The resulting stiffness estimates, and peak forces sustained during the pelvis release experiments, were compared between each BMI and sex group.

The optimized force-deflection stiffness estimation method, k_{combo opt} provided the strongest fit to the experimental data. Strong main effects of BMI (f (1,13) = 10.87, p = 0.003) and sex (f (1,13) = 5.97, p = 0.022) were found for this stiffness estimation method. Additionally, a significant BMI-sex interaction was observed (f (3,6) = 5.31, p = 0.030), with low BMI males having much higher stiffness estimates than any other group. Normalized peak forces were higher in low BMI participants than in high BMI participants (f(1,13)=24.9, p<0.001). Linear regression demonstrated that peak impact force was positively associated with effective pelvic stiffness (β = 0.550, t(25) = 3.110, p=0.005), height (β = 0.326, t(25) = 2.119, p=0.045) and soft tissue thickness (β = 0.785, t(25) = 4.573, p<0.001).

This thesis has demonstrated that body habitus and sex have significant effects on the stiffness of the pelvis during lateral falls. These differences are likely related to a combination of soft tissue and pelvic anatomical differences between BMI and sex groups. Pelvic stiffness, along with other easily collected variables, may be helpful in predicting peak forces resulting from lateral falls in the elderly. Differences in pelvic stiffness estimates between BMI and sex groups, and estimation method, necessitate careful consideration. These data will aid in selecting the most appropriate pelvic stiffness parameters when modeling impact dynamics for higher energy falls.

Year	Entry
1993	Lauritzen JB, Petersen MM, Lund B. Effect of external hip protectors on hip fractures. Lancet. January 2, 1993;341(8836):11-13.
2002	Lochmüller E-M, Groll O, Kuhn V, Eckstein F. Mechanical strength of the proximal femur as predicted from geometric and densitometric bone properties at the lower limb versus the distal radius. Bone. January 2002;30(1):207-216.
1992	Cooper C, Atkinson EJ, O'Fallon WM, Melton JL III. Incidence of clinically diagnosed vertebral fractures: a population‐based study in Rochester, Minnesota, 1985‐1989. J Bone Miner Res. February 1992;7(2):221-227.
1996	van den Kroonenberg AJ, Hayes WC, McMahon TA. Hip impact velocities and body configurations for voluntary falls from standing height. J Biomech. June 1996;29(6):807-811.
1995	Bouxsein ML, Courtney AC, Hayes WC. Ultrasound and densitometry of the calcaneus correlate with the failure loads of cadaveric femurs. Calcif Tiss Int. February 1995;56(2):99-103.
2002	Cummings SR, Melton LJ III. Epidemiology and outcomes of osteoporotic fractures. Lancet. May 18, 2002;359(9319):1761-1767.
1993	Nevitt MC, Cummings SR; Study of Osteoporofic Fractures Research Group. Type of fall and risk of hip and wrist fractures: the study of osteoporotic fractures. J Am Geriatr Soc. November 1993;41(11):1226-1234.
1994	Courtney AC, Wachtel EF, Myers ER, Hayes WC. Effects of loading rate on strength of the proximal femur. Calcif Tiss Int. 1994;55(1):53-58.
1996	Hayes WC, Myers ER, Robinovitch SN, Van Den Kroonenberg A, Courtney AC, McMahon TA. Etiology and prevention of age-related hip fractures. Bone. January 1996;18(1)(suppl):77S-86S.
2003	Beason DP, Dakin GJ, Lopez RR, Alonso JE, Bandak FA, Eberhardt AW. Bone mineral density correlates with fracture load in experimental side impacts of the pelvis. J Biomech. 2003;36(2):219-227.
1991	Hayes WC, Piazza SJ, Zysset PK. Biomechanics of fracture risk prediction of the hip and spine by quantitative computed tomography. Radiol Clin North Am. 1991;29(1):1-18.
1991	Grisso JA, Kelsey JL, Strom BL, Chiu GY, Maislin G, O'Brien LA, Hoffman S, Kaplan F; Northeast Hip Fracture Study Group. Risk factors for falls as a cause of hip fracture in women. NEJM. May 9, 1991;324(19):1326-1331.
2001	Wiktorowicz ME, Goeree R, Papaioannou A, Adachi JD, Papadimitropoulos E. Economic implications of hip fracture: health service use, institutional care and cost in Canada. Osteoporos Int. May 2001;12(4):271-278.
2006	Chandrashekar N, Mansouri H, Slauterbeck J, Hashemi J. Sex-based differences in the tensile properties of the human anterior cruciate ligament. J Biomech. 2006;39(16):2943-2950.
2008	Laing AC, Robinovitch SN. The force attenuation provided by hip protectors depends on impact velocity, pelvic size, and soft tissue stiffness. J Biomech Eng. December 2008;130(6):061005.
2007	Feldman F, Robinovitch SN. Reducing hip fracture risk during sideways falls: evidence in young adults of the protective effects of impact to the hands and stepping. J Biomech. 2007;40(12):2612-2618.
1995	Robinovitch SN, McMahon TA, Hayes WC. Force attenuation in trochanteric soft tissues during impact from a fall. J Orthop Res. November 1995;13(6):956-962.
1998	Cheng XG, Lowet G, Boonen S, Nicholson PHF, Van Der Perre G, Dequeker J. Prediction of vertebral and femoral strength in vitro by bone mineral density measured at different skeletal sites. J Bone Miner Res. September 1998;13(9):1439-1443.
1994	Best TM, McElhaney J, Garrett WE, Myers BS. Characterization of the passive responses of live skeletal muscle using the quasi-linear theory of viscoelasticity. J Biomech. April 1994;27(4):413-419.
1982	Kempson GE. Relationship between the tensile properties of articular cartilage from the human knee and age. Ann Rheum Dis. October 1982;41(5):508-511.
1997	Robinovitch SN, Hayes WC, McMahon TA. Distribution of contact force during impact to the hip. Ann Biomed Eng. May 1997;25(3):499-508.
2007	Bouxsein ML, Szulc P, Munoz F, Thrall E, Sornay‐Rendu E, Delmas PD. Contribution of trochanteric soft tissues to fall force estimates, the factor of risk, and prediction of hip fracture risk. J Bone Miner Res*. June 2007;22(6):825-831.
1996	Marshall D, Johnell O, Wedel H. Meta-analysis of how well measures of bone mineral density predict occurrence of osteoporotic fractures. BMJ. May 18, 1996;312(7041):1254-1259.
1991	Robinovitch SN, Hayes WC, McMahon TA. Prediction of femoral impact forces in falls on the hip. J Biomech Eng. November 1991;113(4):366-374.

Year

Entry

1993

Lauritzen JB, Petersen MM, Lund B. Effect of external hip protectors on hip fractures. Lancet. January 2, 1993;341(8836):11-13.

2002

Lochmüller E-M, Groll O, Kuhn V, Eckstein F. Mechanical strength of the proximal femur as predicted from geometric and densitometric bone properties at the lower limb versus the distal radius. Bone. January 2002;30(1):207-216.

1992

Cooper C, Atkinson EJ, O'Fallon WM, Melton JL III. Incidence of clinically diagnosed vertebral fractures: a population‐based study in Rochester, Minnesota, 1985‐1989. J Bone Miner Res. February 1992;7(2):221-227.

1996

van den Kroonenberg AJ, Hayes WC, McMahon TA. Hip impact velocities and body configurations for voluntary falls from standing height. J Biomech. June 1996;29(6):807-811.

1995

Bouxsein ML, Courtney AC, Hayes WC. Ultrasound and densitometry of the calcaneus correlate with the failure loads of cadaveric femurs. Calcif Tiss Int. February 1995;56(2):99-103.

2002

Cummings SR, Melton LJ III. Epidemiology and outcomes of osteoporotic fractures. Lancet. May 18, 2002;359(9319):1761-1767.

1993

Nevitt MC, Cummings SR; Study of Osteoporofic Fractures Research Group. Type of fall and risk of hip and wrist fractures: the study of osteoporotic fractures. J Am Geriatr Soc. November 1993;41(11):1226-1234.

1994

Courtney AC, Wachtel EF, Myers ER, Hayes WC. Effects of loading rate on strength of the proximal femur. Calcif Tiss Int. 1994;55(1):53-58.

1996

Hayes WC, Myers ER, Robinovitch SN, Van Den Kroonenberg A, Courtney AC, McMahon TA. Etiology and prevention of age-related hip fractures. Bone. January 1996;18(1)(suppl):77S-86S.

2003

Beason DP, Dakin GJ, Lopez RR, Alonso JE, Bandak FA, Eberhardt AW. Bone mineral density correlates with fracture load in experimental side impacts of the pelvis. J Biomech. 2003;36(2):219-227.

1991

Hayes WC, Piazza SJ, Zysset PK. Biomechanics of fracture risk prediction of the hip and spine by quantitative computed tomography. Radiol Clin North Am. 1991;29(1):1-18.

1991

Grisso JA, Kelsey JL, Strom BL, Chiu GY, Maislin G, O'Brien LA, Hoffman S, Kaplan F; Northeast Hip Fracture Study Group. Risk factors for falls as a cause of hip fracture in women. NEJM. May 9, 1991;324(19):1326-1331.

2001

Wiktorowicz ME, Goeree R, Papaioannou A, Adachi JD, Papadimitropoulos E. Economic implications of hip fracture: health service use, institutional care and cost in Canada. Osteoporos Int. May 2001;12(4):271-278.

2006

Chandrashekar N, Mansouri H, Slauterbeck J, Hashemi J. Sex-based differences in the tensile properties of the human anterior cruciate ligament. J Biomech. 2006;39(16):2943-2950.

2008

Laing AC, Robinovitch SN. The force attenuation provided by hip protectors depends on impact velocity, pelvic size, and soft tissue stiffness. J Biomech Eng. December 2008;130(6):061005.

2007

Feldman F, Robinovitch SN. Reducing hip fracture risk during sideways falls: evidence in young adults of the protective effects of impact to the hands and stepping. J Biomech. 2007;40(12):2612-2618.

1995

Robinovitch SN, McMahon TA, Hayes WC. Force attenuation in trochanteric soft tissues during impact from a fall. J Orthop Res. November 1995;13(6):956-962.

1998

Cheng XG, Lowet G, Boonen S, Nicholson PHF, Van Der Perre G, Dequeker J. Prediction of vertebral and femoral strength in vitro by bone mineral density measured at different skeletal sites. J Bone Miner Res. September 1998;13(9):1439-1443.

1994

Best TM, McElhaney J, Garrett WE, Myers BS. Characterization of the passive responses of live skeletal muscle using the quasi-linear theory of viscoelasticity. J Biomech. April 1994;27(4):413-419.

1982

Kempson GE. Relationship between the tensile properties of articular cartilage from the human knee and age. Ann Rheum Dis. October 1982;41(5):508-511.

1997

Robinovitch SN, Hayes WC, McMahon TA. Distribution of contact force during impact to the hip. Ann Biomed Eng. May 1997;25(3):499-508.

2007

Bouxsein ML, Szulc P, Munoz F, Thrall E, Sornay‐Rendu E, Delmas PD. Contribution of trochanteric soft tissues to fall force estimates, the factor of risk, and prediction of hip fracture risk*. J Bone Miner Res. June 2007;22(6):825-831.

1996

Marshall D, Johnell O, Wedel H. Meta-analysis of how well measures of bone mineral density predict occurrence of osteoporotic fractures. BMJ. May 18, 1996;312(7041):1254-1259.

1991

Robinovitch SN, Hayes WC, McMahon TA. Prediction of femoral impact forces in falls on the hip. J Biomech Eng. November 1991;113(4):366-374.

Year	Entry
2019	Fleps I. Assessing the Risk of Hip Fracture: Subject-Specific Dynamic Models for the Simulation of Sideways Fall Impact [PhD thesis]. Swiss Federal Institute of Technology Zürich; 2019.
2017	Levine IC. The Effects of Body Composition and Body Configuration on Impact Dynamics During Lateral Falls: Insights from in-Vivo, in-Vitro, and in-Silico Approaches [PhD thesis]. University of Waterloo; 2017.

Year

Entry

2019

Fleps I. Assessing the Risk of Hip Fracture: Subject-Specific Dynamic Models for the Simulation of Sideways Fall Impact [PhD thesis]. Swiss Federal Institute of Technology Zürich; 2019.

2017

Levine IC. The Effects of Body Composition and Body Configuration on Impact Dynamics During Lateral Falls: Insights from in-Vivo, in-Vitro, and in-Silico Approaches [PhD thesis]. University of Waterloo; 2017.