Mechanical evaluation of hip pads to protect against fracture of elderly femurs in falls.

Hip fracture in the aged easily occurs by falls and may cause these persons to become bedridden. Hip pads are effective in protecting hip fracture as they directly deflect and absorb the impact forces by falls. It is necessary for the material and the structure of hip pads to be designed to realize both high impact absorption and compliance (comfort during wearing). In this report, an impact testing system was developed to test the impact absorbing performance of hip pad with air cushions designed by the research group. The impact absorbing performance was evaluated by the impact load, collision time, and maximum load. To confirm the effectiveness in protecting against hip fracture, an impact force was applied to the greater trochanter of the human femur and the degree of fracture was measured by X-ray examination. As a result, the hip pad with air cushions had a high impact absorbing performance and was sufficiently effective to protect against hip fracture.

Long-term stress distribution patterns across the elbow joint in baseball players assessed by computed tomography osteoabsorptiometry.

BACKGROUND: The distribution pattern of subchondral bone density is considered to highly reflect the stress distribution across a joint under long-term physiologic loading conditions. Therefore, the biomechanical characteristics over the elbow joint surface under long-term loading conditions of baseball pitching can be determined by a measurement of the distribution pattern. HYPOTHESIS: Stress distribution over the elbow joint surface alters with long-term pitching activities. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Computed tomography (CT) imaging data from the dominant elbow of 10 nonthrowing athletes, 10 college baseball fielders, and 10 college baseball pitchers were collected for the current analysis. The distribution of subchondral bone density through the distal articular surface of the humerus was measured using a CT osteoabsorptiometry method. The quantitative analysis of the obtained data focused on location and size of the maximum density area at the articular surface. RESULTS: The maximum density area of subchondral bone across the articular surface of the distal humerus was located in the posterior part of the trochlea in all subjects. This maximum density area was significantly increased in the pitcher group, compared with that in other groups. Additionally, the pitcher group demonstrated a significant distribution of the maximum density area in the anterior part of the capitellum. CONCLUSION: The results indicate that actual stress across the elbow is concentrated in the posterior part of the trochlea in humans. Baseball pitching may produce excessive or repetitive stress against not only this part, but also the anterior part of the capitellum. The majority of osteochondritis dissecans lesions affecting the elbow are found in the anterior part of the capitellum in throwing athletes. The results may support an important role of mechanical conditions in the cause of elbow osteochondritis dissecans.