gms | German Medical Science

Objectives: The aim of the study was to investigate the deformational relief of the stem taper during repeated ball impactions.

Methods: We performed bench tests consisting of threefold impaction of the ball on the stem followed by microscopic analysis of the taper surface. The intact components were: taper of the Corail stem (DePuy) and a Co-Cr ball (DePuy). Microscopic analysis of taper deformation relief was performed using a MIRA 2 LMU auto-emission scanning electron microscope. Measurement areas: area of the narrow part of the taper (1 zone), area of the middle part of the taper (2 zone), area of the wide part of the taper (3 zone). Measurement levels - 200x, 500x, 2000x.

Results and conclusion: On the surface of intact taper, there is a symmetrically applied contrapuntal notch with a depth of 1.32 micrometers. During single impaction of the ball, the depth of the contralateral notch was 1.38 micrometers. There were 2 “removal defects” of 416 micrometers with a depth of 1.16 micrometers and a width of 70 micrometers, 35 micrometers, and 30 micrometers according to the study areas. After the second test cycle, the depth of the counter notch was 1.12 micrometers with a width of "removal defects" of 80 micrometers, 35 micrometers and 40 micrometers, respectively. Additionally, surface linear striation was recorded across the entire surface of the specimen. During triple impaction of the ball, the depth of the notch was registered at the same level and was 1.22 micrometers. The width of the defect increased to 120 micrometers in the area of the narrow part of the taper. The width of the defects were at the same level in zones 2, 3. The number of “removal defects” did not depend on the ball impaction amount. Conclusion. Repeated impactions of the ball do not lead to significant changes in the morphology of the taper surface and do not prevent subsequent jamming of the ball.