Age-related changes in dynamic compressive properties of trochanteric soft tissues over the hip

• Published in: Journal of biomechanics Vol. 48; no. 4; pp. 695 - 700
• Main Authors: Choi, W.J., Russell, C.M., Tsai, C.M., Arzanpour, S., Robinovitch, S.N.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 26.02.2015; Elsevier Limited
• Subjects: Accidental Falls; Adipose Tissue - diagnostic imaging; Adipose Tissue - physiology; Adult; Age; Aged; Aged, 80 and over; Aging; Aging - physiology; Biomechanical Phenomena - physiology; Body mass index; Bone density; Compressive Strength - physiology; Damping; Dynamic mechanical properties; Dynamics; Elasticity - physiology; Experiments; Falls; Female; Femur - physiology; Fracture mechanics; Fractures; Hip fracture; Hip Fractures - epidemiology; Hip joint; Humans; Injury prevention; Mathematical models; Mechanical properties; Medical research; Muscle, Skeletal - diagnostic imaging; Muscle, Skeletal - physiology; Older people; Physical Medicine and Rehabilitation; Reduction; Risk Factors; Skin; Skin - diagnostic imaging; Skin Physiological Phenomena; Soft tissue; Soft tissues; Stiffness; Studies; Ultrasonic imaging; Ultrasonography; Ultrasound; Vibration analysis; Falls; Damping; Hip fracture; Injury prevention; Aging; Mechanical properties; Soft tissue; Stiffness; Ultrasound; Vibration analysis
• DOI: 10.1016/j.jbiomech.2014.12.026
• ISSN: 0021-9290; 1873-2380

Hip fracture risk increases dramatically with age, and 90% of fractures are due to falls. During a fall on the hip, the soft tissues overlying the hip region (skin, fat, and muscle) act as shock absorbers to absorb energy and reduce the peak force applied to the underlying bone. We conducted dynamic indentation experiments with young women (aged 19–30; n=17) and older women (aged 65–81; n=17) to test the hypothesis that changes occur with age in the stiffness and damping properties of these tissues. Tissue stiffness and damping were derived from experiments where subjects lay sideways on a bed with the greater trochanter contacting a 3.8cm diameter indenter, which applied sinusoidal compression between 5 to 30Hz with a peak-to-peak amplitude of 1mm. Soft tissue thickness was measured using ultrasound. On average, stiffness was 2.9-fold smaller in older than young women (5.7 versus 16.8kN/m, p=0.0005) and damping was 3.5-fold smaller in older than young women (81 versus 282Ns/m, p=0.001). Neither parameter associated with soft tissue thickness. Our results indicate substantial age-related reductions in the stiffness and damping of soft tissues over the hip region, which likely reduce their capacity to absorb and dissipate energy (before “bottoming out”) during a fall. Strategies such as wearable hip protectors or compliant flooringmay compensate for age-related reductions in the shock-absorbing properties of soft tissues and decrease the injury potential of falls.