ABSTRACT
Objective: In this study, thermoelastic stress analysis was conducted to clarify the surface stress distribution of a femur in which a BiCONTACT E stem was inserted. The contact sites between the stem and femur were examined to investigate the association with the range of stress distribution.Materials and Methods: BiCONTACT E was set up using two synthetic femurs that mimic the morphology and mechanical properties of living bone. Preoperative planning was performed using three-dimensional imaging software. The synthetic bone was placed in a sample holder. After the stem was implanted into the synthetic bone, computed tomography imaging was performed. The contact sites between the stem and the cortical part of the synthetic bone were examined using the imaging software. Subsequently, thermoelastic stress measurements were performed on the sample.Results: The results of thermoelastic stress analysis indicated a minimum change in the sum of principal stresses [Δ (σ1+σ2)] on the medial side and a maximum change in the sum of principal stresses on the lateral side. Thus, no minimum change was observed in the sum of the principal stresses at the maximum proximal part. It is reasonable to assume that the use of a cementless stem can inevitably lead to bone atrophy in the proximal part of the femur. The contact sites between the stem and femur were also investigated, and the results of the study clearly and quantitatively demonstrated the correlation of the contact sites with a range of stress distributions.Conclusion: The surface stress distribution of a femur, in which a BiCONTACT E stem was inserted, was clarified. The contact sites between the stem and femur were also investigated. Furthermore, the correlation between these results and clinical bone response was investigated in this study.
ABSTRACT
<b>Objective:</b> The incidence of pulmonary embolism (PE) and leg deep vein thrombosis (DVT) has increased in recent years in association with aging and an increase in the number of bedridden individuals. We developed an active in-bed leg exercise apparatus labeled the Leg Exercise Apparatus (LEX) for DVT prevention. We compared the effect of leg exercises performed using the LEX to conventional active ankle exercises on increased blood flow.<br><b>Materials & Methods:</b> The subjects were eight healthy adult volunteers [five men and three women, aged 20–34 (mean 27.0) years]. Subjects performed two types of exercise; exercise 1 consisted of leg exercises using the LEX, while exercise 2 consisted of in-bed active plantar flexion/dorsiflexion exercises without the device. Measurements were taken 1, 5, 10, 20, and 30 minutes after exercise including common femoral vein blood flow, mean blood flow velocity, maximum blood flow velocity, and vessel diameter using Doppler ultrasound. Statistical procedures included timed measurement data analysis using a linear mixed model. A Bonferroni correction was used for multiple comparisons.<br><b>Results:</b> Compared to resting levels, blood flow reached a maximum value 1 minute after exercise for both exercise types, with a significantly greater increase after exercise 1 (1.76-fold increase) compared to exercise 2 (1.44-fold increase) (<i>p</i> = 0.005). There was a significant difference (<i>p</i> = 0.03) between the two exercises for all values from 1 minute to 30 minutes following exercise. There was no significant difference between exercises for peak or mean blood flow velocity. Compared to resting levels, blood vessel diameter reached a maximum value of 1.47-fold greater at 5 minutes post-exercise for exercise 1 and a maximum value of 1.21-fold greater at 1 minute post-exercise for exercise 2.<br><b>Conclusions:</b> Exercise using the LEX increased lower leg venous blood flow and vessel diameter. We propose that the LEX may serve as a new DVT prevention tool.
ABSTRACT
STUDY DESIGN: Prospective experimental study on humans. PURPOSE: To determine whether postural differences during a low-speed impact are observed in the sagittal and axial views, particularly in a relaxed state. OVERVIEW OF LITERATURE:: Three-dimensional motion capture systems have been used to analyze posture and head-neck-torso kinematics in humans during a simulated low-speed impact, yet little research has focused on the axial view. Since a seatbelt asymmetrically stabilizes a drivers right shoulder and left lower waist into the seat, it potentially creates movement in the axial view. METHODS: Three healthy adult men participated in the experimental series, which used a low-speed sled system. The acceleration pulse created a full sine shape with a maximum acceleration of 8.0 m/s2 at 500 ms, during which the kinematics were evaluated in relaxed and tensed states. The three-dimensional motion capture system used eight markers to record and analyze body movement and head-neck-torso kinematics in the sagittal and axial views during the low-speed impact. Head and trunk rotation angles were also calculated. RESULTS: Larger movements were observed in the relaxed than in the tensed state in the sagittal view. The cervical and thoracic spine flexed and extended, respectively, in the relaxed state. In the axial view, larger movements were also observed in the relaxed state than in the tensed state, and the left shoulder rotated. CONCLUSIONS: During simulated frontal impact, the rotation angle between the head and trunk was significantly larger in the relaxed state. Therefore, we recommend also observing movement in the axial view during impact tests.