Since its first reported by Cloward in 1981[1], Posterior Lumbar Interbody Fusion (PLIF) surgery has been widely used in the treatment of degenerative lumbar diseases due to its features of adequate decompression and reconstruction of spinal stability. Interbody fusion cages play a crucial role in PLIF surgery, as they can expand the intervertebral space, better restore the physiological curvature of the lumbar spine, and provide greater space for interbody bone grafting. For unstable vertebral bodies, interbody fusion cages can enhance the stability of the anterior and middle columns, reducing the occurrence of loosening and fracture of pedicle screw-rod systems[2].
In the 1950s, Cloward attempted to achieve intervertebral fusion by using vertebral body grafting, but it had a low fusion rate[3]. In response, Bagby designed a cage-like interbody fusion device made of stainless steel, which laid the groundwork for the modern cage[4]. With continuous advancements in materials and manufacturing techniques, cages made of various materials have emerged. Currently, polyetheretherketone (PEEK) interbody fusion devices are the most widely used due to their excellent elastic modulus and tissue compatibility, which help maintain intervertebral height and prevent cage subsidence caused by stress shielding[5]. However, PEEK materials have poor surface bone integration capability, resulting in a lower interbody fusion rate. Among metal fusion devices, titanium alloys exhibit corrosion resistance, good tissue compatibility, and strong bone integration capabilities. Cuzzocrea et al. found that titanium alloys have a better interbody fusion rate compared to PEEK materials. However, due to the significant difference in elastic modulus between titanium alloys and vertebral bodies, subsidence of the fusion device may occur due to stress shielding[6].
3D printing, an important technology that emerged in the 1980s, has rapidly developed over the past 30 years. Unlike traditional subtractive manufacturing and casting techniques, 3D printing not only alters the physical structure of products but also allows for customization according to individual needs. This capability enables a complete match between materials and affected areas, making it particularly promising for medical applications. Customized implantable 3D-printed prosthetics can achieve both structural integrity and functional reconstruction for complex anatomical defects. They have been utilized in maxillofacial reconstruction, neurosurgical cranial reconstruction, vertebral body reconstruction following spinal tumor resection, and other procedures[7–9]. Currently, domestically certified 3D-printed titanium alloy cages, such as those produced by Aike Medical in China, have superior individualized designs compared to PEEK material cages. They offer a larger contact area, resulting in tighter adhesion to adjacent vertebrae and reducing the probability of settling due to cutting forces. With a porous design resembling trabecular bone structure, these cages have an elastic modulus similar to cancellous bone, facilitating bone ingrowth and promoting fusion.
From November 2018 to April 2023, our hospital conducted a randomized controlled study comparing the use of 3D-printed titanium alloy cages for intervertebral fusion in posterior lumbar fusion surgery with the application of PEEK material cages. The study aimed to evaluate the effectiveness, safety, and usability of 3D-printed cages in posterior lumbar fusion surgery and assess their long-term fusion outcomes through radiographic evaluation.