A 3D Printed Porous Titanium Alloy Rod with Diamond Crystal Lattice for Treatment of the Early-Stage Femoral Head Osteonecrosis in Sheep

Stability, biomechanics and biocompatibility analysis following different preparation strategies of hierarchical zeolite coatings on titanium alloy surfaces

Traditional titanium alloy implant surfaces are inherently smooth and often lack effective osteoinductive properties. To overcome these limitations, coating technologies are frequently employed to enhance the efficiency of bone integration at the implant-host bone interface. Hierarchical zeolites, characterized by their chemical stability, can be applied to 3D-printed porous titanium alloy (pTi) surfaces as coating. The resulting novel implants with a "microporous-mesoporous-macroporous" spatial gradient structure can influence the behavior of adjacent cells; thereby, promoting the integration of bone at the implant interface. Consequently, a thorough exploration of various preparation methods is warranted for hierarchical zeolite coatings with respect to biocompatibility, coating stability, and osteogenesis. In this study, we employed three methods: in situ crystal growth, secondary growth, and layer-by-layer assembly, to construct hierarchical zeolite coatings on pTi, resulting in the development of a gradient structure. The findings of this investigation unequivocally demonstrated that the LBL-coating method consistently produced coatings characterized by superior uniformity, heightened surface roughness, and increased hydrophilicity, as well as increased biomechanical properties. These advantages considerably amplified cell adhesion, spreading, osteogenic differentiation, and mineralization of MC3T3-E1 cells, presenting superior biological functionality when compared to alternative coating methods. The outcomes of this research provide a solid theoretical basis for the clinical translation of hierarchical zeolite coatings in surface modifications for orthopedic implants.

Bone tissue engineering for treating osteonecrosis of the femoral head

Osteonecrosis of the femoral head (ONFH) is a devastating and complicated disease with an unclear etiology. Femoral head-preserving surgeries have been devoted to delaying and hindering the collapse of the femoral head since their introduction in the last century. However, the isolated femoral head-preserving surgeries cannot prevent the natural progression of ONFH, and the combination of autogenous or allogeneic bone grafting often leads to many undesired complications. To tackle this dilemma, bone tissue engineering has been widely developed to compensate for the deficiencies of these surgeries. During the last decades, great progress has been made in ingenious bone tissue engineering for ONFH treatment. Herein, we comprehensively summarize the state-of-the-art progress made in bone tissue engineering for ONFH treatment. The definition, classification, etiology, diagnosis, and current treatments of ONFH are first described. Then, the recent progress in the development of various bone-repairing biomaterials, including bioceramics, natural polymers, synthetic polymers, and metals, for treating ONFH is presented. Thereafter, regenerative therapies for ONFH treatment are also discussed. Finally, we give some personal insights on the current challenges of these therapeutic strategies in the clinic and the future development of bone tissue engineering for ONFH treatment.

Comparison of bone ingrowth between two porous titanium alloy rods with biogenic lamellar structures and diamond crystal lattice on femoral condyles in rabbits

PURPOSE

The comparison of bone ingrowth between two types of porous titanium alloy rods with different micro-architectures including diamond crystal lattice (Re-rod) and biogenic lamellar configurations (Bi-rod) on femoral condyles was investigated in this study.

METHODS

Twelve rabbits were used. Re-rod (Re-rod group) and Bi-rod (Bi-rod group) were implanted randomly in femoral condyles of each rabbits respectively. Bone ingrowth of these two rods were investigated and compared. 4 and 12 weeks after the operation, X-ray, micro-CT and histological examinations were performed.

RESULTS

No femoral condyle fracture and rod defluxion in the two groups was noted in the X-ray images during the observation period. Micro-CT images showed that all metal trabeculae in the Bi-rod group were covered by new bone at 4 and 12 weeks, whereas partial metal trabeculae in the Re-rod group were still uncovered at 12 weeks. Histological images showed that there was new bone growth in the centre and periphery of Bi-rods at 4 and 12 weeks, and there were several areas without new bone ingrowth at 4 and 12 weeks in the centre of Re-rods. In micro-CT analysis, the bone volume to total volume (BV/TV) of the volume of interest (VOI) of the Bi-rod group was higher than in the Re-rod group [(0.0794 ± 0.0021) % Vs (0.0521 ± 0.0032) % and (0.0875 ± 0.0039) % Vs (0.0702 ± 0.0028) % respectively, P < 0.05] at 4 weeks and 12 weeks. Whereas, the mean trabecular thickness (Tb.Th) values of VOI between the two groups were not significantly statistically different at 4 and 12 weeks. In histological analysis, the BV/TV of the VOI of the Bi-rod group was higher than in the Re-rod group [(0.0624 ± 0.0021) % Vs (0.0435 ± 0.0028) % and (0.0675 ± 0.0024) % Vs (0.0476 ± 0.0031) % respectively, P < 0.05] at 4 weeks and 12 weeks.

CONCLUSION

These results showed that Bi-rods got better bone ingrowth in femoral condyles of rabbits compared with Re-rods.

Three-dimensional-printed porous prosthesis for the joint-sparing reconstruction of the proximal humeral tumorous defect

Background: Tumorous bone defect reconstructions of the proximal humerus with joint sparing is a challenge. Numerous reconstruction methods have been proposed but the proximal residual humerus is commonly sacrificed because of its extremely short length. To preserve the proximal humerus and improve clinical outcomes, we designed a three-dimensional (3D) printed uncemented prosthesis with a porous structure to treat tumorous bone defects of the proximal humerus. Methods: Our analysis included seven patients treated between March 2018 and July 2019. A 3D model was established, and related data were obtained, including the diameter of the humeral head, the resection length, and the residual length. A prosthesis was designed and fabricated based on these data. Functional and oncologic outcomes were recorded, and complications and osseointegration were evaluated. Results: The mean age of the patients was 20.3 years, and the median follow-up period was 26 months. The lengths of the residual proximal humerus were 17.9 mm on average. All the patients had preserved humeral heads and most of the rotator cuff was intact. The average postoperative range of motion (ROM) of the affected shoulder was 83.8°; flexion was 82.5°, extension was 43.8°, and adduction was 16.3°. The average Musculoskeletal Tumor Society score (MSTS) was 94.3%. Good osseointegration was observed on the interface between the bone and prosthesis. Conclusion: A 3D printed porous prosthesis with cone-like structures successfully achieved joint-sparing reconstruction of proximal humeral tumorous defects with satisfying functional outcomes. The preservation of the rotator cuff and humeral head plays an essential role in the function of the shoulder joint.

Additive Manufacturing in Orthopedics: A Review

Additive manufacturing is an advanced manufacturing manner that seems like the industrial revolution. It has the inborn benefit of producing complex formations, which are distinct from traditional machining technology. Its manufacturing strategy is flexible, including a wide range of materials, and its manufacturing cycle is short. Additive manufacturing techniques are progressively used in bone research and orthopedic operation as more innovative materials are developed. This Review lists the recent research results, analyzes the strengths and weaknesses of diverse three-dimensional printing strategies in orthopedics, and sums up the use of varying 3D printing strategies in surgical guides, surgical implants, surgical predictive models, and bone tissue engineering. Moreover, various postprocessing methods for additive manufacturing for orthopedics are described.

Tissue Engineering Strategies for Treating Avascular Necrosis of the Femoral Head

Avascular necrosis (AVN) of the femoral head commonly leads to symptomatic osteoarthritis of the hip. In older patients, hip replacement is a viable option that restores the hip biomechanics and improves pain but in pediatric, adolescent, and young adult patients hip replacements impose significant activity limitations and the need for multiple revision surgeries with increasing risk of complication. Early detection of AVN requires a high level of suspicion as diagnostic techniques such as X-rays are not sensitive in the early stages of the disease. There are multiple etiologies that can lead to this disease. In the pediatric and adolescent population, trauma is a commonly recognized cause of AVN. The understanding of the pathophysiology of the disease is limited, adding to the challenge of devising a clinically effective treatment strategy. Surgical techniques to prevent progression of the disease and avoid total hip replacement include core decompression, vascular grafts, and use of bone-marrow derived stem cells with or without adjuncts, such as bisphosphonates and bone morphogenetic protein (BMP), all of which are partially effective only in the very early stages of the disease. Further, these strategies often only improve pain and range of motion in the short-term in some patients and do not predictably prevent progression of the disease. Tissue engineering strategies with the combined use of biomaterials, stem cells and growth factors offer a potential strategy to avoid metallic implants and surgery. Structural, bioactive biomaterial platforms could help in stabilizing the femoral head while inducing osteogenic differentiation to regenerate bone and provide angiogenic cues to concomitantly recover vasculature in the femoral head. Moreover, injectable systems that can be delivered using a minimal invasive procedure and provide mechanical support the collapsing femoral head could potentially alleviate the need for surgical interventions in the future. The present review describes the limitations of existing surgical methods and the recent advances in tissue engineering that are leading in the direction of a clinically effective, translational solution for AVN in future.

Additively manufactured biodegradable porous magnesium implants for elimination of implant-related infections: An in vitro and in vivo study

Magnesium (Mg) alloys that have both antibacterial and osteogenic properties are suitable candidates for orthopedic implants. However, the fabrication of ideal Mg implants suitable for bone repair remains challenging because it requires implants with interconnected pore structures and personalized geometric shapes. In this study, we fabricated a porous 3D-printed Mg-Nd-Zn-Zr (denoted as JDBM) implant with suitable mechanical properties using selective laser melting technology. The 3D-printed JDBM implant exhibited cytocompatibility in MC3T3-E1 and RAW267.4 cells and excellent osteoinductivity in vitro. Furthermore, the implant demonstrated excellent antibacterial ratios of 90.0% and 92.1% for methicillin-resistant S. aureus (MRSA) and Escherichia coli, respectively. The 3D-printed JDBM implant prevented MRSA-induced implant-related infection in a rabbit model and showed good in vivo biocompatibility based on the results of histological evaluation, blood tests, and Mg²⁺ deposition detection. In addition, enhanced inflammatory response and TNF-α secretion were observed at the bone-implant interface of the 3D-printed JDBM implants during the early implantation stage. The high Mg²⁺ environment produced by the degradation of 3D-printed JDBM implants could promote M1 phenotype of macrophages (Tnf, iNOS, Ccl3, Ccl4, Ccl5, Cxcl10, and Cxcl2), and enhance the phagocytic ability of macrophages. The enhanced immunoregulatory effect generated by relatively fast Mg²⁺ release and implant degradation during the early implantation stage is a potential antibacterial mechanism of Mg-based implant. Our findings indicate that 3D-printed porous JDBM implants, having both antibacterial property and osteoinductivity, hold potential for future orthopedic applications.

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Porous JDBM implants promising mechanical properties was fabricated by selective laser melting.

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3D-printed JDBM implant exhibited excellent antibacterial property, osteoinductivity, and biocompatibility.

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Temporally enhanced immunoregulatory effect in early stage was a potential antibacterial mechanism of Mg-based implant.

Three-dimensional-printed customized prosthesis for pubic defect: clinical outcomes in 5 cases at a mean follow-up of 24 months

Background

Pubic defects resulting from type III hemipelvectomy are commonly not reconstructed due to the need to preserve the weight-bearing axis. However, the opening of the anterior pelvic ring will inevitably lead to increased pelvic instability. To improve long-term pelvic stability, three-dimensional (3D)-printed customized prostheses were designed to reconstruct pubic defects. This study presents and evaluates the short-term clinical outcomes and complications from the use of this construct.

Methods

Five patients who underwent type III hemipelvectomy and 3D-printed customized prosthesis reconstruction at our institution between 2017 and 2019 were retrospectively analysed. Operation time and blood loss during the operation were recorded. Local and functional recovery was assessed. Prosthetic position and osseointegration were evaluated. Oncology results and complications were recorded.

Results

The prostheses consisted of three with stems and two without. The mean follow-up time was 23.6 months. At the last follow-up, all five patients were alive with no evidence of disease. No deep infections or local recurrence had occurred. The mean blood loss and mean intraoperative time were 1680 ml and 294 min, respectively. The mean functional MSTS score at the final follow-up was 29.8. Fretting wear around the prosthetic stem was found in 3 patients, while bone wear on the normal-side pubis was found in 2 patients. Osseointegration was observed in all patients.

Conclusions

3D-printed customized prostheses for reconstructing pubic bone defects after type III hemipelvectomy showed acceptable early outcomes. The good outcomes were inseparable from the precision prosthesis design, strict surgical procedures, and sensible postoperative management.

3D X-ray micro-computed tomography imaging for the microarchitecture evaluation of porous metallic implants and scaffolds

As an advanced microscopy technology with strong sample adaptability and non-destructive three-dimensional (3D) characteristics, X-ray micro-computed tomography (Micro-CT) can establish the overall connection between various microarchitecture parameters and accelerate the research process of porous metallic implants and scaffolds. In this review, the Micro-CT based quantitative evaluation methods of microarchitecture and bone formation are investigated. To ensure reliability of the results, the Micro-CT setup is discussed briefly and the essential image processing algorithms are introduced in detail. The significance and limitations of Micro-CT are analyzed in the context of research on porous metallic implants. We also discuss the future development of Micro-CT technology in the field of biological tissue engineering.

An animal model of early-stage femoral head osteonecrosis induced by cryo-insult in small tailed Han sheep

Purpose

This study investigated the ability of liquid nitrogen cryo-insults to induce early-stage osteonecrosis of the femoral head (ONFH) in small tail Han sheep.

Methods

16 animals were subjected to unilateral cryo-insult using cryogen equipment with a cryo-insult probe, followed 1, 3, and 6 months later by X-ray, CT scanning, micro-CT scanning, and histological evaluation.

Results

X-ray evaluation of operative femoral heads (Op-FHs) at each time point showed low density areas under the cartilage surface that paralleled sclerosis belts, and CT scans showed sclerosis and cyst areas in Op-FHs. Micro-CT analysis showed that the ratio of bone to total volume and mean trabecular thickness of regions of interest (ROIs) were lower in Op-FHs than in normal femoral heads (No-FHs) at each time point (n = 4, p < 0.05). Histological evaluation at 1 month showed that necrotic changes were dominant as evidenced by moderate empty lacunae, decreases in the number of hematopoietic cells, and moderate increases in the number of fibroblasts. At 3 and 6 months, fractured trabeculae, fibroblasts, and new blood capillaries were increased, indicating an absorption and repair process. Bone volume fraction of ROIs of Op-FHs was lower than in No-FHs at each time point (n = 4, p < 0.05) in histological evaluation. At 6 months, the maximum load of No-FHs was higher than Op-FHs (n = 4, p < 0.05).

Conclusion

These findings indicate that early-stage ONFH can be induced in small tail Han sheep using cryogenic equipment.

The translational potential of this article

This animal model may be helpful in developing new treatment modalities for human ONFH.

Promotion of osteointegration by silk fibroin coating under diabetic conditions on 3D printed porous titanium implants via ROS-mediated NF-κB pathway

The clinical evidence indicates the compromised application of titanium implants (TI) in diabetics, associated with reactive oxygen species (ROS) overproduction at the bone-implant interface. Silk fibroin has exerted impressive biocompatibility in application of biomedical material and optimal anti-diabetic effect as oriental medicine. We proposed that SF coated titanium implant (STI) could alleviate diabetes-induced compromised osteointegration, which had been rarely reported before. To confirm the hypothesis and explore the underlying mechanisms, rat osteoblasts cultured on 3-dimensional (3D) printed TI and STI were subjected to normal serum (NS), diabetic serum (DS), DS with NAC (a ROS inhibitor) or SN50 (a NF-κB inhibitor). In vivo study was performed on diabetic sheep implanted with TI or STI into the bone defect on crista iliaca. Results demonstrated that ROS overproduction induced by diabetes lead to osteoblast dysfunctions and cellular apoptosis on TI substrate, associated with activation of NF-κB signaling pathway in osteoblasts. Importantly, STI substrate significantly attenuated ROS production and NF-κBp65 phosphorylation, through which the osteoblast biological dysfunctions were ameliorated. These results were further confirmed in vivo by the improved osteointegration of STI evidenced by Micro-CT and histological examinations compared with TI. These results demonstrated that ROS-mediated NF-κB signaling pathway played a crucial role in diabetes-induced implant destabilization. Importantly, SF coating as a promising material for biomaterial-engineering markedly improved clinical treatment effect of TI under diabetic conditions, possibly associated with the suppression of NF-κB pathway.

Fabrication of piezoelectric porous BaTiO3 scaffold to repair large segmental bone defect in sheep

Porous titanium scaffolds can provide sufficient mechanical support and bone growth space for large segmental bone defect repair. However, they fail to restore the physiological environment of bone tissue. Barium titanate (BaTiO3) is considered a smart material that can produce an electric field in response to dynamic force. Low-intensity pulsed ultrasound stimulation (LIPUS), as a kind of micromechanical wave, can not only promote bone repair but also induce BaTiO3 to generate an electric field. In our studies, BaTiO3 was coated on porous Ti6Al4V and LIPUS was externally applied to observe the influence of the piezoelectric effect on the repair of large bone defects in vitro and in vivo. The results show that the piezoelectric effect can effectively promote the osteogenic differentiation of bone marrow stromal cells (BMSCs) in vitro as well as bone formation and growth into implants in vivo. This study provides an optional alternative to the conventional porous Ti6Al4V scaffold with enhanced osteogenesis and osseointegration for the repair of large bone defects.

Three-dimensional-printed customized prosthesis for pubic defect: prosthesis design and surgical techniques

Background

This study is to describe the detailed design and surgical techniques of three-dimensional (3D)-printed customized prosthesis for pubic bone defect.

Patients and methods

Five patients under type III resections were included in this study. Based on radiography data, 3D pelvic model was established and virtual surgery was simulated. Detailed anatomy data were measured including the size and arc of normal pubis, the size of residual bone in acetabular side. Different fixation ways were considered according to shape of defect. After features modification and porous structure design, prostheses were fabricated. The osteotomy guides and plastic models were used during surgery.

Result

Of 5 cases, the prostheses consist of the type with stem (3, 60%) and the type without stem (2, 40%). Mean follow-up period was 13.6 months (range, 8-24 months). For partial pubis removed cases, the mean length and width of narrowest part of normal superior pubis were 13.19 mm (range, 12.51-14.12 mm) and 7.80 mm (range, 7.18-8.26 mm) respectively. Mean arc of normal pubis was 2.71 rad (range, 2.66-2.73 rad). For the entire pubis resection cases, the mean diameter of narrowest parts and length of normal superior pubis were 11.52 mm (range, 11.13-11.91 mm) and 64.78 mm (range, 63.46-66.09 mm), while the diameter of narrowest part and length of normal inferior pubis were 7.37 mm (range, 7.20-7.54 mm) and 86.43 mm (range, 84.28-88.57 mm). Mean length and arc of intramedullary stem was 20 mm (range, 18-21 mm) and 2.7 rad. Mean screw holes number was 6.3 (range, 6-7) while ultimate screws number in surgeries was 4.3 (range, 4-5). Porous structure with 600-μm-pore size and 70% porosity was applied in parts of contact with residual bone.

Conclusion

3D-printed customized prostheses could be a feasible option to reconstruct bone defect after type III resection. The design of 3D-printed customized prostheses is a multi-step process which is based on strict anatomic measurement.

A 3D printed porous titanium alloy rod with biogenic lamellar configuration for treatment of the early-stage femoral head osteonecrosis in sheep

There is no ideal implant for mechanical strut on early-stage osteonecrosis of the femoral head (ONFH) after core decompression. In this study, a biogenic trabecular porous titanium rod with lamellar configuration was designed and fabricated using selective laser melting technique. Early-stage ONFH of sheep induced by cryo-insult were dealt with core decompression combined with rod insertion (Rod group) and core decompression alone (CD group) after X-ray evaluation was used to assess the necrotic region one months after cryo-intervention. Bone integration and ingrowth of the two groups were investigated and compared. Early-stage ONFH intervened with the rod gained better bone ingrowth than CD 3 and 6 months after the intervention, as evidenced by radiographic, micro-CT and histological evaluation. X-ray images showed compact integration between rods and peripheral bone, evidenced by no radiolucent lines encircling the rods at 3 and 6 months. Micro-CT and histological images showed that the new bone had grown into the centre of rods along the metal at 3 months, whereas the new bone grew mainly at the periphery of the decompressive channel. Micro-CT analysis show that the ratios of bone volume to total volume (BV/TV) of volume of interest (VOI) in Rod group was 890.0% and 438.1% higher than CD group at 3 (0.198 ± 0.0094 VS 0.020 ± 0.0058, p < 0.05, n = 3) and 6 (0.226 ± 0.0166 VS 0.042 ± 0.0061, p < 0.05, n = 3) months respectively. Histological analysis showed that the BV/TV of VOI in Rod group was 881.0% and 413.3% higher than CD group at 3 (0.206 ± 0.0102 VS 0.021 ± 0.0061, p < 0.05, n = 3) and 6 (0.231 ± 0.0156 VS 0.045 ± 0.0059, p < 0.05, n = 3) months respectively. The mechanical tests revealed that the maximum load of Rod group was 57.6% larger than CD group at 6 months (4505.25 ± 443.86 N VS 2858.25 ± 512.91 N, p < 0.05, n = 3). These favourable short-term results can provide insight on treatment of early-stage ONFH.