Femoral Stems With Porous Lattice Structures: A Review.

Bolun Liu,Huizhi Wang,Min Zhang,Ningze Zhang,Cheng-Kung Cheng

doi:10.3389/fbioe.2021.772539

Bolun Liu, Huizhi Wang + Show 3 more

Open Access

https://doi.org/10.3389/fbioe.2021.772539

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Abstract

Cementless femoral stems are prone to stress shielding of the femoral bone, which is caused by a mismatch in stiffness between the femoral stem and femur. This can cause bone resorption and resultant loosening of the implant. It is possible to reduce the stress shielding by using a femoral stem with porous structures and lower stiffness. A porous structure also provides a secondary function of allowing bone ingrowth, thus improving the long-term stability of the prosthesis. Furthermore, due to the advent of additive manufacturing (AM) technology, it is possible to fabricate femoral stems with internal porous lattices. Several review articles have discussed porous structures, mainly focusing on the geometric design, mechanical properties and influence on bone ingrowth. However, the safety and effectiveness of porous femoral stems depend not only on the characteristic of porous structure but also on the macro design of the femoral stem; for example, the distribution of the porous structure, the stem geometric shape, the material, and the manufacturing process. This review focuses on porous femoral stems, including the porous structure, macro geometric design of the stem, performance evaluation, research methods used for designing and evaluating the femoral stems, materials and manufacturing techniques. In addition, this review will evaluate whether porous femoral stems can reduce stress shielding and increase bone ingrowth, in addition to analyzing their shortcomings and related risks and providing ideas for potential design improvements.

Highlights

Total hip arthroplasty (THA) is a surgical procedure that replaces the diseased joint with an artificial femoral stem and acetabular cup
This paper reviewed previous research into porous femoral stems, including the structural/morphological characteristics of the porous structure, the mechanical and biological performance of the femoral stem, factors affecting performance, and material and manufacturing techniques
1) As for the porous structure applied to the femoral stem, most previous studies used regular porous structure types

Summary

INTRODUCTION

Total hip arthroplasty (THA) is a surgical procedure that replaces the diseased joint with an artificial femoral stem and acetabular cup. This osseointegration provides biological fixation and secondary stability for the femoral stem, enhancing load transfer from the stem to the bone and decreasing stress shielding (Bobyn et al, 1987) Surface coatings, such as sintered beads, hydroxyapatite coating, grit-blasted surfaces, and titanium plasma spray have been used in orthopedic implants over the past 40 years to promote osseointegration. Porous metal has a lower stiffness than a solid implant (Cheng et al, 2012), and varying the quantity, size and location of the pores can be used to tailor the stiffness of the femoral stem and reduce stress shielding around the proximal femur (Arabnejad et al, 2017; Wang et al, 2018; Mehboob et al, 2020a). The intent is to provide an informative reference for the development of porous femoral stems

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