Abstract
The use of interbody implants for spinal fusion has been steadily increasing to avoid the risks of complications and donor site morbidity when using autologous bone. Understanding the pros and cons of various implant designs can assist the surgeon in choosing the ideal interbody for each individual patient. The goal of these interbody cages is to promote a surface area for bony ingrowth while having the biomechanical properties to support the axial skeleton. Currently, the majority of interbody implants consists of metal or polyether ether ketone (PEEK) cages with bone graft incorporated inside. Titanium alloy implants have been commonly used, however, the large difference in modulus of elasticity from bone has inherent issues. PEEK implants have a desirable surface area with the benefit of a modulus of elasticity closer to that of bone. Unfortunately, clinically, these devices have had increased risk of subsidence. More recently, 3D printed implants have come into the market, providing mechanical stability with increased surface design for bony ingrowth. While clinical outcomes studies are limited, early results have demonstrated more reliable and quicker fusion rates using 3D custom interbody devices. In this review, we discuss the biology of osseointegration, the use of surface coated implants, as well as the potential benefits of using 3D printed interbodies.
Highlights
Musculoskeletal conditions are among the most disabling and costly conditions experienced by Americans [1]
While autologous bone grafts are generally regarded as the standard augment for spinal fusion surgeries due to their osteogenic capabilities, complications and morbidity to the donor site have given rise to the use of substitutes and spinal implants [5,6]
Interbody cages are often made of polyether ether ketone (Figure 3), which is an inert semicrystalline polyaromatic linear polymer
Summary
Musculoskeletal conditions are among the most disabling and costly conditions experienced by Americans [1]. Osseointegration refers to the direct integration of bone to metal resulting in structural and functional integration between the living bone and implant surface [8]. There have been reported cases in which significant osteolysis developed, despite indetectable traces of wear debris [21–23]. These issues have been minimized by controlling specific implant properties like surface roughness and nanostructures to promote bone apposition directly onto implant surfaces [24–29]. The purpose of this review is to (1) evaluate the key biological processes that occur around implants, (2) discuss the role that surface structure plays on osseointegration, and (3) discuss current literature on custom 3D printed cages and their impact on fusion rates
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