Krull A, Morlock M M, Bishop N E
Institute of Biomechanics, TUHH - Hamburg University of Technology, Denickestrasse 15, 21073 Hamburg, Germany.
Faculty of Life Sciences, HAW Hamburg University of Applied Sciences, Ulmenliet 20, 21033 Hamburg, Germany.
Bone Joint Res. 2018 Apr 12;7(2):196-204. doi: 10.1302/2046-3758.72.BJR-2017-0078.R2. eCollection 2018 Feb.
Taper junctions between modular hip arthroplasty femoral heads and stems fail by wear or corrosion which can be caused by relative motion at their interface. Increasing the assembly force can reduce relative motion and corrosion but may also damage surrounding tissues. The purpose of this study was to determine the effects of increasing the impaction energy and the stiffness of the impactor tool on the stability of the taper junction and on the forces transmitted through the patient's surrounding tissues.
A commercially available impaction tool was modified to assemble components in the laboratory using impactor tips with varying stiffness at different applied energy levels. Springs were mounted below the modular components to represent the patient. The pull-off force of the head from the stem was measured to assess stability, and the displacement of the springs was measured to assess the force transmitted to the patient's tissues.
The pull-off force of the head increased as the stiffness of the impactor tip increased but without increasing the force transmitted through the springs (patient). Increasing the impaction energy increased the pull-off force but also increased the force transmitted through the springs.
To limit wear and corrosion, manufacturers should maximize the stiffness of the impactor tool but without damaging the surface of the head. This strategy will maximize the stability of the head on the stem for a given applied energy, without influencing the force transmitted through the patient's tissues. Current impactor designs already appear to approach this limit. Increasing the applied energy (which is dependent on the mass of the hammer and square of the contact speed) increases the stability of the modular connection but proportionally increases the force transmitted through the patient's tissues, as well as to the surface of the head, and should be restricted to safe levels.: A. Krull, M. M. Morlock, N. E. Bishop. Maximizing the fixation strength of modular components by impaction without tissue damage. 2018;7:196-204. DOI: 10.1302/2046-3758.72.BJR-2017-0078.R2.
模块化髋关节置换术的股骨头与股骨柄之间的锥形连接会因磨损或腐蚀而失效，这可能是由它们界面处的相对运动引起的。增加装配力可以减少相对运动和腐蚀，但也可能损伤周围组织。本研究的目的是确定增加撞击能量和撞击工具的刚度对锥形连接稳定性以及通过患者周围组织传递的力的影响。
对一种市售的撞击工具进行改装，以便在实验室中使用不同刚度的撞击头在不同的施加能量水平下组装部件。在模块化部件下方安装弹簧以代表患者。测量股骨头从股骨柄上的拔出力以评估稳定性，并测量弹簧的位移以评估传递到患者组织的力。
随着撞击头刚度的增加，股骨头的拔出力增加，但通过弹簧（患者）传递的力没有增加。增加撞击能量会增加拔出力，但也会增加通过弹簧传递的力。
为了限制磨损和腐蚀，制造商应使撞击工具的刚度最大化，但不损伤股骨头表面。这种策略将在给定的施加能量下使股骨头在股骨柄上的稳定性最大化，而不会影响通过患者组织传递的力。目前撞击工具的设计似乎已经接近这一极限。增加施加的能量（这取决于锤子的质量和接触速度的平方）会增加模块化连接的稳定性，但会成比例地增加通过患者组织以及传递到股骨头表面的力，因此应限制在安全水平。：A. 克鲁尔，M.M. 莫洛克，N.E. 毕晓普。通过撞击最大化模块化部件的固定强度而不损伤组织。2018年；7：196 - 204。DOI：10.1302/2046 - 3758.72.BJR - 2017 - 0078.R2 。
