van Duren Bernard H, Taufiqurrakhman Mohamad, Jones Alison, Higgins Mark, Manktelow Andrew R, Bloch Benjamin V, Pandit Hemant
Nottingham Elective Orthopaedic Services, Nottingham University Hospitals NHS Trust, Nottingham, UK.
Leeds Institute of Rheumatic and Musculoskeletal Medicine, University of Leeds, Leeds, UK.
Bone Joint Res. 2025 Jul 16;14(7):642-655. doi: 10.1302/2046-3758.147.BJR-2024-0408.R1.
Cemented polished taper fit (PTF) stems are the femoral implant of choice for total hip arthroplasty (THA) in many locations worldwide. There is increasing evidence that periprosthetic fracture may be the single major contributor to reoperation with these stems. The aim of this study was to demonstrate how mismatches at the implant-cement interface may occur and the subsequent effect of these incongruities on the contacting area and the forces transmitted to the cement mantle.
A parametric equation-based model was developed to determine the contact mismatch relative to axial stem rotations. This model was also used to calculate the restoration of contact surface area with stem subsidence for both a dual-taper and triple-taper geometry. A finite element analysis (FEA) was used to compare the effects of reduced contact area due to the incongruent hip implant-cement interface.
The contact model showed a large decrease in surface contact area with even only a small rotation going from 100% at 0° to 50.00% at 2.5° for the dual-taper geometry, and from 100% at 0° to 50.20% at 2.5° for the triple-taper geometry. There was a gradual but small ongoing decrease in contact surface with increasing rotation for both the dual-taper and triple-taper geometries. For both taper designs, there was an increase in contact surface area with an increase in subsidence resulting in contact for up to a 5° mismatch being restored with 2 mm subsidence. FEA showed that with increasing mismatches and consequent contact area reduction, there was an increase in von Mises stress in the implant-cement interface of up to 235%.
With increasing mismatch, there was an increase in maximum stresses, total strain, and subsidence in the cement mantle, highlighting the importance of achieving an optimal implant-cement interface at the time of implantation of cemented PTF femoral stems.
骨水泥抛光锥形贴合（PTF）柄是全球许多地方全髋关节置换术（THA）中首选的股骨植入物。越来越多的证据表明，假体周围骨折可能是这些柄再次手术的单一主要原因。本研究的目的是证明植入物 - 骨水泥界面处的不匹配是如何发生的，以及这些不一致对接触面积和传递到骨水泥壳的力的后续影响。
开发了一个基于参数方程的模型，以确定相对于柄轴向旋转的接触不匹配。该模型还用于计算双锥形和三锥形几何形状下柄下沉时接触表面积的恢复情况。使用有限元分析（FEA）来比较由于髋关节植入物 - 骨水泥界面不一致导致的接触面积减小的影响。
接触模型显示，对于双锥形几何形状，即使仅从0°时的100% 有小角度旋转到2.5°时的50.00%，表面接触面积也会大幅下降；对于三锥形几何形状，从0°时的100% 旋转到2.5°时为50.20%。对于双锥形和三锥形几何形状，随着旋转增加，接触表面逐渐但小幅持续下降。对于两种锥形设计，随着下沉增加，接触表面积增加，导致高达5°不匹配的接触通过2 mm下沉得以恢复。有限元分析表明，随着不匹配增加以及随之而来的接触面积减小，植入物 - 骨水泥界面处的冯·米塞斯应力增加高达235%。
随着不匹配增加，骨水泥壳中的最大应力、总应变和下沉增加，突出了在植入骨水泥PTF股柄时实现最佳植入物 - 骨水泥界面的重要性。
