Abstract
For older population, a better understanding of the hip joint loading environment is needed for the prevention of hip pain, and the reduction of the stress fractures and fall risks. Using the motion analysis and inverse dynamics methods, combined with musculoskeletal modelling, static optimization, and finite element (FE) femur model, the difference of femoral neck strains between stair ascent vs. descent, young vs. older populations was compared. A two-way repeated-measures MANOVA was applied to test the effect of age and stair direction on the femoral neck strains. The strains at the femoral neck cross-section were greater for stair descent than ascent for both age groups (mostly P = 0.001 to 0006) but there was no difference between age groups. In this study, femoral neck strains represented bone loading environment in more direct ways than joint reaction forces/moments or joint contact forces, the risk of hip pain, falls and stress fractures might be greater during stair descent than ascent. Possible preventative methods to reduce these risks should be developed in the future studies.
Highlights
For older population, a better understanding of the hip joint loading environment is needed for the prevention of hip pain, and the reduction of the stress fractures and fall risks
Investigating the load environment for the femoral neck could be a useful way to investigate the risk factors of the stress fractures, femur pain and its related fall risks for some certain daily activities, which could be helpful to minimize further damage/pain at the hip joint or develop preventative measures to reduce the load on the femoral neck[15,16]
Musculoskeletal modelling and muscle force estimation could be utilized with the 2-demensional simplified model to estimate femoral neck stresses for stair ascent and d escent[24], but the strain estimation could not be performed with the 2-D model
Summary
A better understanding of the hip joint loading environment is needed for the prevention of hip pain, and the reduction of the stress fractures and fall risks. Using the motion analysis and inverse dynamics methods, combined with musculoskeletal modelling, static optimization, and finite element (FE) femur model, the difference of femoral neck strains between stair ascent vs descent, young vs older populations was compared. Femoral neck strains represented bone loading environment in more direct ways than joint reaction forces/moments or joint contact forces, the risk of hip pain, falls and stress fractures might be greater during stair descent than ascent. Utilization of inverse dynamics and rigid body models allows the estimation of net joint moments and reaction forces during stair ascent and descent[22,23], which found the greater hip moments for stair descent than ascent These methods neglected the effect of co-contracting muscles and fail to consider the size and material properties of the bone. Finite element model with simplified muscle models could lead to significantly inaccurate estimation[28,29], so the more complex and realistic load conditions (with full muscle models) should be needed to reflect the accuracy of the stress/strain e stimation[30,31]
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