Deformation of an acetabular cup implant during cementless implantation is indicative of the radial compressive forces, and such of the initial implant fixation strength. Stress relaxation in the surrounding bone tissue following implantation could reduce the deformation of the cup and thus primary implant fixation. The aim of this study was therefore to determine the early shape change of the implanted cup immediately after implantation with different press-fit levels and whether recording the force during cup impaction can be used to estimate initial cup fixation. Cup implantations into porcine acetabulae (n=10) were performed using a drop tower. The force induced by the drop weight and cup seating after each impact was recorded. Deformation of the implanted cup was determined with strain gauges over a period of 10min. Lever-out torques were measured to assess the initial fixation strength. Stress relaxation in the bone caused a reduction in cup deformation of 13.52±4.06% after 1min and 29.34±5.11% after 10min. The fixation strength increased with a higher force magnitude during impaction (R_s²=0.810, p=0.037). Reduction of the radial compressive forces due to stress relaxation of the surrounding bone should be considered during press-fit cup implantation in order to compensate for the reduced fixation strength over time. In addition, recording the implantation force could help to estimate initial fixation strength.

在非骨水泥植入过程中髋臼杯植入物的变形指示径向压缩力，并且指示初始植入物固定强度。植入后周围骨组织中的应力松弛可减少杯的变形，从而减少植入物的一次固定。因此，本研究的目的是确定在植入后以不同的压配合水平立即进行的杯子的早期形状变化，以及是否可以使用记录杯子撞击时的力来估计杯子的初始固定。使用滴管塔将杯植入猪髋臼（n = 10）。记录每次撞击后下落重量和杯座所产生的力。用应变计在10分钟内确定植入杯的变形。测量杠杆扭矩以评估初始固定强度。骨骼中的应力松弛导致杯形变形在1分钟后减少13.52±4.06％，在10分钟后减少29.34±5.11％。在撞击过程中，固定强度随着力的增加而增加（R_s ²＝ 0.810，p ＝ 0.037）。在压配合杯植入过程中，应考虑由于周围骨骼应力松弛而引起的径向压缩力的降低，以补偿随时间推移而降低的固定强度。另外，记录植入力可以帮助估计初始固定强度。