Jiantao Liu

Large bone defects remain a major clinical challenge and often require load-bearing implants for reconstruction. Titanium alloys are widely used for bone defect repair because of their favorable mechanical properties and biocompatibility; however, their high elastic modulus and limited bioactivity can cause stress shielding and insufficient osseointegration. Porous architectures have therefore been introduced to tailor the elastic modulus and promote bone ingrowth. This review summarizes current clinical applications and unresolved challenges of porous titanium implants, and integrates recent preclinical evidence on manufacturing routes and key design parameters. We analyze how pore topology (periodic versus stochastic architectures), pore size, porosity, strut diameter, and multiscale designs affect osseointegration. Overall, the review provides design-oriented insights and highlights prospects and challenges for future preclinical and clinical research to improve the osseointegration of porous titanium implants.

Using selective laser melting, a metal three-dimensional (3D) printing technique, we developed bionic trabecular titanium alloy scaffolds with a micro–nano composite porous structure to address the limitations of traditional titanium implants. By integrating bionic design principles with advanced metal 3D printing strategies, these scaffolds mimic the trabecular network of cancellous bone, reducing elastic modulus (to ~4 GPa) and mitigating stress shielding. The bioprinted scaffolds exhibited enhanced surface properties that promoted Schwann cell (SC) adhesion, elongation, and spindle-like morphology, forming cellular networks along the microporous architecture. In contrast, SCs on solid titanium scaffolds displayed a flattened morphology with limited functionality. Transcriptomic analysis revealed that the scaffold’s micro–nano structure regulated SC behavior via the focal adhesion kinase-mitogen-activated protein kinase mechanotransduction pathway, enhancing the secretion of pro-osteogenic (e.g., platelet-derived growth factor with two A subunits) and pro-angiogenic (e.g., vascular endothelial growth factor) factors. Trabecular-like scaffold-conditioned medium significantly accelerated bone marrow mesenchymal stem cell proliferation, osteogenic differentiation, and endothelial cell angiogenesis, achieving a 36% higher healing rate compared to controls. While in vivo validation remains essential, our in vitro model isolates SC-driven mechanisms, avoiding systemic confounders. This study highlights the potential of 3D bioprinted scaffolds for personalized bone defect repair, offering a biomechanically and biologically optimized solution to enhance osseointegration.

There are various internal fixation methods in treating lumbosacral spinal tuberculosis. The study compared the stability and stress distribution in surrounding tissues/implants, such as discs, endplates and screw-rod internal fixation system, etc. when applying three different lumbar internal fixation methods to treat lumbosacral spinal tuberculosis. A finite element model was constructed and validated. The spinal stability was restored using three methods: a titanium cage with lateral double screw-rod fixation (group 1), autologous bone with posterior double screw-rod fixation (group 2), and a titanium cage with posterior double screw-rod fixation (group 3). For comparison, group 4 represented the intact L3-S1 spine. Finally, a load was applied, and the ranges of motion and Von Mises stresses in the cortical endplates, screw-rod internal fixation system and cortical bone around the screws in the different groups were recorded and analyzed. All six ranges of motion (flexion, extension, left/right lateral bending, left/right rotation) of the surgical segment were substantially lower in groups 1 (0.53° ~ 1.41°), 2 (0.68° ~ 1.54°) and 3 (0.55° ~ 0.64°) than in group 4 (4.48° ~ 10.12°). The maximum stress in the screw-rod internal fixation system was clearly higher in group 2 than in groups 1 and 3 under flexion, left/right lateral bending, and left/right rotation. However, in extension, group 1 had the highest maximum stress in the screw-rod internal fixation system. Group 2 had the lowest peak stresses in the cortical endplates in all directions. The peak stresses in the cortical bone around the screws were higher in group 1 and group 2 than in group 3 in all directions. Thus, titanium cage with posterior double screw-rod fixation has more advantages in immediate reconstruction of lumbosacral spinal stability and prevention of screw loosening.

Introduction: Ti6Al4V titanium alloy is widely used in producing orthopedic and maxillofacial implants, but drawbacks include high elastic modulus, poor osseointegration performance, and toxic elements. A new medical titanium alloy material with better comprehensive performance is urgently needed in the clinic.Methods: Ti10Mo6Zr4Sn3Nb titanium alloy (referred to as Ti-B12) is a unique medical ß titanium alloy material developed by us. The mechanical properties of Ti-B12 depict that it has advantages, such as high strength, low elastic modulus, and fatigue resistance. In our study, the biocompatibility and osseointegration properties of Ti-B12 titanium alloy are further studied to provide theoretical guidance for its clinical transformation.Results and Discussion: The titanium alloy Ti-B12 displays no significant effect on MC3T3-E1 cell morphology, proliferation, or apoptosis in vitro. Neither Ti-B12 titanium alloy nor Ti6Al4V titanium alloy depicts a significant difference (p > 0.05); Ti-B12 material extract injected into the abdominal cavity of mice does not cause acute systemic toxicity. The skin irritation test and intradermal irritation test reveal that Ti-B12 does not cause skin allergic reactions in rabbits. Compared to Ti6Al4V, Ti-B12 titanium alloy material has more advantages in promoting osteoblast adhesion and ALP secretion (p < 0.05). Although there is no significant difference in OCN and Runx2 gene expression between the three groups on the 7th and 14th days of differentiation induction (p > 0.05), the expression of Ti-B12 group is higher than that of Ti6Al4V group and blank control group. Furthermore, the rabbit in vivo test present that 3 months after the material is implanted in the lateral epicondyle of the rabbit femur, the Ti-B12 material fuses with the surrounding bone without connective tissue wrapping. This study confirms that the new β-titanium alloy Ti-B12 not only has low toxicity and does not cause rejection reaction but also has better osseointegration performance than the traditional titanium alloy Ti6Al4V. Therefore, Ti-B12 material is expected to be further promoted in clinical practice.

Nanodynamic therapy (NDT) based on reactive oxygen species (ROS) production has been envisioned as an effective cancer treatment. However, the efficacy is limited by the hypoxia, insufficient hydrogen peroxide conversion, and high glutathione (GSH) levels in the tumor microenvironment (TME). To solve these issues, we proposed and designed a biocompatible, oxygen resistant Cu‐modified Ti ₃ C ₂ nanocomposite (Ti ₃ C ₂ ‐Cu‐PEG), which can efficiently deplete the endogenous GSH in tumor cells, smartly respond to NIR‐II light irradiation with in‐depth tissue penetration to achieve photothermally enhanced tumor photodynamic therapy (PDT) and catalytic therapy. Specifically, Ti ₃ C ₂ ‐Cu‐PEG reacted with oxygen to produce singlet oxygen ( ¹ O ₂ ) under NIR‐II irradiation, and catalyzed the highly expressed H ₂ O ₂ in the tumor microenvironment to generate ·OH. In addition, Ti ₃ C ₂ ‐Cu‐PEG significantly decreased intracellular GSH, reduced the chances of reaction between ROS and GSH, and thus promoting ROS effect. Moreover, the intrinsically high photothermal conversion efficiency of Ti ₃ C ₂ ‐Cu‐PEG further promotes the NDT process. In vitro and in vivo experiments, the Ti ₃ C ₂ ‐Cu‐PEG nanosystem showed excellent antitumor effect in 4T1 tumor‐bearing mice by amplifying oxidative stress under NIR‐II stimulation. This work highlights an easily synergistic nanosystem with remodeling TME and combined photothermal therapy to enhance the therapeutic effect of NDT in tumor therapy.

The aim of the study was to evaluate the biomechanical properties of a novel nonfused artificial vertebral body in treating lumbar diseases and to compare with those of the fusion artificial vertebral body. An intact finite element model of the L1–L5 lumbar spine was constructed and validated. Then, the finite element models of the fusion group and nonfusion group were constructed by replacing the L3 vertebral body and adjacent intervertebral discs with prostheses. For all finite element models, an axial preload of 500 N and another 10 N m imposed on the superior surface of L1. The range of motion and stress peaks in the adjacent discs, endplates, and facet joints were compared among the three groups. The ranges of motion of the L1–2 and L4–5 discs in flexion, extension, left lateral bending, right lateral bending, left rotation and right rotation were greater in the fusion group than those in the intact group and nonfusion group. The fusion group induced the greatest stress peaks in the adjacent discs and adjacent facet joints compared to the intact group and nonfusion group. The nonfused artificial vertebral body could better retain mobility of the surgical site after implantation (3.6°–8.7°), avoid increased mobility and stress of the adjacent discs and facet joints.

Objective. To compare the biomechanical properties of a new memory compression alloy plate and traditional titanium plate after anterior cervical discectomy and fusion (ACDF). Methods. A finite element model of the C3‐7 segments was developed and validated. The C5‐6 disc was removed, and an intervertebral cage made of peek material was implanted. Then, a new memory compression alloy plate composed of Ti‐Ni memory alloy and a traditional titanium plate were integrated at the C5‐6 segment. All models were subjected to a load of 73.6 N to simulate the head weight and 1 Nm of flexion‐extension, lateral bending, and axial rotation. The range of segmental motion (ROM) and stress on the prostheses, adjacent discs, and endplates were analyzed. Results. Compared with intact status, ACDF with the new prothesis and traditional titanium plate reduced the ROM of C5‐6 in six directions by 95.2%‐100% and increased that of adjacent discs (C4‐5 and C6‐7) by 4.8%‐112.5%. Adjacent disc stress peaks were higher for the traditional titanium plate (0.7‐4.2 MPa) than for the new prosthesis (0.6‐4.1 MPa). Endplate stress peaks were the highest in ACDF with the new prosthesis (15.6‐53.3 MPa), followed by ACDF with traditional titanium plate (5.0‐29.4 MPa). Stress peaks were significantly lower for the new prothesis (12.8‐52.3 MPa) than for the traditional titanium plate (397.0‐666.1 MPa). Conclusions. The new prosthesis improved the immediate stability of the surgical site and had an elastic modulus that was smaller than that of traditional titanium plate, making it conducive to reducing stress shielding and the impact on the adjacent intervertebral disc.

Although various surgical methods are used to treat lumbosacral tuberculosis, no unified surgical approach exists. Thus, exploring an optimal operation method has substantial clinical importance. Evaluate the initial stability of a new surgical method, a one-stage anterior debridement and cage implantation combined with anterior-lateral fixation by a dual screw-rod construct, in the treatment of lumbosacral tuberculosis and provide biomechanical support for its further promotion in clinical applications. Fifteen fresh human lumbosacral spine specimens without fractures, deformities or osteoporosis were randomly divided into intact (I), anterior fixation (AF) and posterior fixation (PF) groups. All AF and PF group specimens had subtotal resections of the L5 vertebra and adjacent discs, while the I group specimens were kept intact. Then, titanium cages were implanted in the surgical site and a dual screw-rod construct was fixed anterior-laterally in the AF group, while the PF group specimens were fixed posteriorly with only the dual screw-rod construct. Mechanical tests were conducted for initial stability evaluations. The load at the maximum displacement (5 mm) or rotation angle (5 °) was less for the I group specimens than for the AF and PF group specimens in all directions (P < 0.05). The load at the maximum displacement (5 mm) was greater for the AF group specimens than for the PF group specimens in flexion, lateral bending and axial compression (P < 0.05) and lower than in the PF group specimens in extension (P < 0.05). In torsion, there was no difference between the loads in the AF and PF groups at the maximum rotation angle (5 °) (P > 0.05). Conclusions: The proposed surgical approach can provide better immediate stability than anterior debridement with posterior dual screw-rod fixation in the treatment of lumbosacral tuberculosis in flexion, lateral bending and axial compression.