Fritsche Andreas, Bialek Kristin, Mittelmeier Wolfram, Simnacher Martin, Fethke Klaus, Wree Andreas, Bader Rainer
Department of Orthopaedics, Orthopaedische Klinik und Poliklinik, Universitaet Rostock, Forschungslabor fuer Biomechanik und Implantattechnologie, Doberaner Strasse 142, Rostock, Germany.
J Orthop Sci. 2008 May;13(3):240-7. doi: 10.1007/s00776-008-1212-z. Epub 2008 Jun 6.
The deformation behavior of threaded and press-fit acetabular cups in correlation with the applied torques and forces to insert the cups has not been widely investigated. The aim of this experimental study was to analyze the deformation behavior of threaded (BICON-PLUS) and press-fit (EP FIT PLUS and Metal shell) acetabular cup designs during insertion and extraction with regard to the possibility of cup failure.
The experiments were carried out using artificial bone and human acetabular bone. The torque needed to insert the threaded cups and the force applied to the press-fit cups was measured. The force and torque were applied manually by a surgeon using common surgical instruments. The strain of the cups was assessed by tangentially and radially applied strain gauges during the insertion process, the implanted state, and extraction. These measurements were used to calculate the change in diameter of the acetabular cups and the strains at the notches of the threaded acetabular cup.
The results showed that maximum strains and applied torques and force occurred during cup insertion. In the case of the threaded cup, an average maximum insertion torque of 114 Nm was measured using bone substitute, whereas only 47 Nm was assessed using human acetabulum. A maximum change in diameter of 8 microm was calculated during the implanted state for the threaded cup. The impact forces for both press-fit cups ranged from approximately 1.0 to 8.9 kN. The change in diameter was 8 microm for the Metal shell and 4 microm for the EP FIT PLUS. In all cases, no permanent cup deformation was detected.
The observed deformations suggest that implant failure of the analyzed acetabular cups is unlikely during insertion, the implanted state, or extraction under normal conditions.
螺纹式和压配式髋臼杯的变形行为与安装杯体时施加的扭矩和力之间的关系尚未得到广泛研究。本实验研究的目的是分析螺纹式（BICON-PLUS）和压配式（EP FIT PLUS和金属杯）髋臼杯设计在插入和取出过程中关于杯体失效可能性的变形行为。
实验使用人工骨和人髋臼骨进行。测量了插入螺纹杯所需的扭矩以及施加在压配杯上的力。外科医生使用普通手术器械手动施加力和扭矩。在插入过程、植入状态和取出过程中，通过切向和径向施加的应变片评估杯体的应变。这些测量用于计算髋臼杯直径的变化以及螺纹髋臼杯缺口处的应变。
结果表明，杯体插入过程中出现最大应变、施加的扭矩和力。对于螺纹杯，使用骨替代物时测得的平均最大插入扭矩为114 Nm，而使用人髋臼时仅为47 Nm。螺纹杯在植入状态下计算出的最大直径变化为8微米。两种压配杯的冲击力范围约为1.0至8.9 kN。金属杯的直径变化为8微米，EP FIT PLUS为4微米。在所有情况下，均未检测到杯体的永久变形。
观察到的变形表明，在正常条件下，所分析的髋臼杯在插入、植入状态或取出过程中不太可能发生植入失败。
