No abstract

The oscillation angle (OsA), which is the sum of the impingement angles on the two sides when the prosthetic neck sways from the neutral axis of the acetabular cup to the liner rim, is one of the most important factors that can affect the range of motion of an artificial hip joint. The aim of this study was to determine the influence of total hip component design on the impingement angle. Our findings show that an increase in cup depth of the liner restricts the motion of the neck and results in a reduced impingement angle, while an increase in chamfer angle increases the impingement angle until it reaches a critical value when a further increase no longer results in an increase in impingement angle. The impingement angle is not only dependent on the head/neck ratio, but also on the head size itself. For most arbitrarily chosen cup depths and chamfer angles, the neck only impacts at one point on the liner. This study proposes a suitable combination of cup depth and chamfer angle and a preferred impact mode, which, if impingement does occur, enables the neck to impinge on the liner rim over a large area. Cup-neck combinations that have an adequate OsA with maximum femoral head coverage are presented.

Dislocation is a serious potential complication of total hip replacement. Previous studies have proposed a newly developed total hip structure that meets the required oscillation angle of 120°, for which the chamfer on the acetabular liner rim was designed to enable the neck to impinge on the chamfer over a large area after impingement occurs. This study adopted the finite element method to further analyse the torque limits leading to dislocation and the contact stresses at the impingement and egress sites of the liner during subluxation. The compressive stress-strain curve for ultra-high molecular weight polyethylene is nonlinear. The results reveal that an adequate chamfer angle of the acetabular cup liner can significantly increase dislocation torque and decrease contact stress on the liner rim. By means of the new design, when the head-neck ratio (HNR) is 2.5 or 3.0, the maximum torque value that a 36-mm head can withstand is 1.38 (8.7 Nm/6.3 Nm) or 1.47 (8.4 Nm/5.7 Nm) times that of a 22-mm head, while the maximum stress of a 36-mm head is 0.41 (14.58 MPa/35.73 MPa) or 0.70 (33.71 MPa/47.90 MPa) times that of a 22-mm head. When the head diameters are identical, the dislocation torque of the HNR = 2.5 structure is slightly greater than that of the HNR = 3.0 structure (3.3-10.5%); thus, the newly developed structure can disperse contact stress, and the structure of a large head with a low HNR exhibits a higher dislocation torque value and lower stress.

Fall prevention is critical for aged adults as falling down has been cited as the number one cause of accidental death in aged adults. Static balance training is an effective method of increasing the balancing capacity in aged adults and reducing their fall risk. This article discusses a method that combines virtual reality (VR) technology with motion‐capture devices for aged adults to practice static balance training in a fun and accurate environment. The aged adults wore motion‐capture devices to interactively manipulate a three‐dimensional (3D) human model (HM) in a virtual environment to follow a 3D posture model (PM). The proposed method was implemented using commercial, off‐the‐shelf 3D tools. A preliminary usability study was conducted, and the results show that the parameters of PM design will affect the aged adult's posture control performance. Our method has several advantages over the currently existing approaches. First, by adjusting the PM parameters, different posture control programs could be designed to support customized static balance training. Second, collision detections between the HM and PM could be used to accurately monitor the posture control process and to interactively provide feedback to the trainee. Third, posture control quality could be quantitatively evaluated by analyzing the collision data between the HM and PM. The proposed method could be used to develop a fun, accurate, and customized static balancing capacity training environment for aged adults. © 2012 Wiley Periodicals, Inc.

In this study, a loader drive axle digital model was built using 3D commercial software. On the basis of this model, the transmission efficiency of the main reducing gear, the differential planetary mechanism, and the wheel planetary reducing gear of the loader drive axle were studied. The functional relationship of the transmission efficiency of the loader drive axle was obtained, including multiple factors: the mesh friction coefficient, the mesh power loss coefficient, the normal pressure angle, the helix angle, the offset amount, the speed ratio, the gear ratio, and the characteristic parameters. This revealed the influence law of the loader drive axle by the mesh friction coefficient, mesh power loss coefficient, and speed ratio. The research results showed that the transmission efficiency of the loader drive axle increased with the speed ratio, decreased when the mesh friction coefficient and the mesh power loss coefficient increased, and that there was a greater influence difference on the transmission efficiency of the loader drive axle.