Using a numerical method to precisely evaluate the alpha angle in a hip image.

The alpha angle is a parameter extensively used to assess for cam-type femoroacetabular impingement (FAI) in a 2D image of the hip. As this angle requires estimation of the axis of the femoral neck, the drawing of this axis often results in measurement errors due to subjective judgment, influencing inter-rater and intra-rater agreements. In the present study, sampling points were captured from the edges of a femoral neck and head in the 2D image, and the best curves of the two were fitted respectively by using the curve fitting method.

Using nonlinear finite element models to analyse stress distribution during subluxation and torque required for dislocation of newly developed total hip structure after prosthetic impingement.

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.

Effects of design parameters of total hip components on the impingement angle and determination of the preferred liner skirt shape with an adequate oscillation angle.

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.

Wear analysis of chamfered elongated acetabular cup liners.

This study investigated the wear phenomena of chamfered acetabular cup liners. The liners have three parameters at the lengthened rim: the length of the elongation, the depth of the cup and the chamfer angle. Using published wear volume equations for cylindrically elongated liners, this study analysed the volume of the chamfer to obtain the exact theoretical wear volume of the chamfered liner.