Experimental and clinical performance of porous tantalum in orthopedic surgery

Comparing Trabecular Metal Versus Fiber Mesh Cementless Acetabular Components: A Single-Center Study of 6,563 Hips

BACKGROUND

Trabecular metal is being increasingly used in primary total hip arthroplasty (THA). This study compared medium-term (< 15 years) outcomes of fiber mesh titanium and trabecular metal acetabular components.

METHODS

This study included 6,563 patients who underwent primary THA with either fiber mesh titanium or trabecular metal-backed acetabular components. Data were sourced from a prospectively maintained local arthroplasty database and linked with the National Joint Registry.

RESULTS

The 10-year survivorship was 97.3% for fiber mesh and 98.9% for porous tantalum groups (P = 0.009). Multivariate analysis showed no significant variable associated with reduced revision rates.

CONCLUSIONS

Both fiber mesh titanium and trabecular metal acetabular components demonstrated high survivorship in THA, with trabecular metal showing statistically significant though marginally better survival. Despite the increased cost associated with trabecular metal, its use may be justified in complex primary and revision cases where increased primary stability may be required. Future research should focus on cost analysis and include patient-reported outcomes to guide implant selection further.

Living joint prosthesis with in-situ tissue engineering for real-time and long-term osteoarticular reconstruction

The reconstruction of large osteoarticular defects caused by tumor resection or severe trauma remains a clinical challenge. Current metal prostheses exhibit a lack of osteo-chondrogenic functionality and demonstrate poor integration with host tissues. This often results in complications such as abnormal bone absorption and prosthetic loosening, which may necessitate secondary revisions. Here, we propose a paradigm-shifting "living prosthesis" strategy that combines a customized 3D-printed hollow titanium humeral prosthesis with engineered bone marrow condensations presenting bone morphogenetic protein-2 (BMP-2) and transforming growth factor-β3 (TGF-β3) from encapsulated silk fibroin hydrogels. This innovative approach promotes in situ endochondral defect regeneration of the entire humeral head while simultaneously providing immediate mechanical support. In a rabbit model of total humerus resection, the designed "living prosthesis" achieved weight, macroscopic and microscopic morphologies that were comparable to those of undamaged native joints at 2 months post-implantation, with organized osteochondral tissues were regenerated both around and within the prosthesis. Notably, the "living prosthesis" displayed significantly higher osteo-integration than the blank metal prosthesis did, as evidenced by a 3-fold increase in bone ingrowth and a 2-fold increase in mechanical pull-out strength. Furthermore, the "living prosthesis" restored joint cartilage function, with rabbits exhibiting normal gait and weight-bearing capacity. The successful regeneration of fully functional humeral head tissue from a single implanted prosthesis represents technical advance in designing bioactive bone prosthesis, with promising implications for treating extreme-large osteochondral defects.

Prediction of bone ingrowth into the porous swelling bone anchors using an osteoconnectivity-based adaptive finite element algorithm

In this study, a bone ingrowth framework was developed, which was integrated with a hygro-elastic swelling simulation, to evaluate the ingrowth of bone into porous co-polymeric swelling bone anchors. The aim was to investigate the impact of swelling-induced radial stress on bone ingrowth and the improvement in the mechanical properties and fixation strength of the anchors. Using the finite element method coupled with the osteoconnectivity matrix, the model successfully predicted the sequential bone formation within the porous bone anchor. The bone ingrowth framework was validated based on available experimental data, closely aligning with empirical observations. The results show that owing to radial stresses generated in the bone-anchor interface by swelling, considerable bone ingrowth could be stimulated. Moreover, among the three finite element models incorporating porosity within the recommended pore size range (300-600 μ m ), smaller pore sizes seem to promote faster and more extensive bone ingrowth, while larger pores exhibit slower ingrowth rates. Regardless of the pore sizes, the mechanical integrity and fixation strength of the anchors significantly improved. These findings strengthen the hypotheses that swelling of such anchors can stimulate bone ingrowth, and highlight the importance of pore geometry, size and interconnectivity in optimizing bone ingrowth and improving their performance.

Stacked Cones for Treatment of Massive Bone Loss in Revision Total Knee Arthroplasty: 50% Reoperation Rate at Five Years

BACKGROUND

Metaphyseal cones can be utilized to address bone loss and/or obtain reliable biologic fixation in revision total knee arthroplasties (TKA)s. Sometimes, larger bone defects mandate utilizing more than one cone on either the femoral or tibial side. This study aimed to evaluate implant survivorship, radiographic results, and clinical outcomes of revision TKAs with multiple stacked cones.

METHODS

We identified 50 revision TKAs utilizing stacked cones performed at a single academic institution from 2011 to 2021. Stacked cones were used in the tibia in 26 patients (52%), femur in 22 patients (44%), and both in two patients (4%). The mean age was 69 years, the mean BMI was 33, and 74% were men. Kaplan-Meier survivorship curves were calculated, radiographs were reviewed, and clinical outcomes were evaluated with Knee Society function scores (KSFS). The mean follow-up was five years (range, 17 days to 10 years).

RESULTS

The 5-year survivorship free of re-revision for aseptic loosening of the stacked cone constructs was 93%, and free of any stacked cone re-revision was 75%. There were nine stacked cone constructs (six femoral, three tibial) re-revised, with PJI (n = 7; three with prior PJI) and aseptic loosening (n = 2) being the indications for re-revision. The 5-year survivorship free of any re-revision and any reoperation was 58 and 50%, respectively. There were 17 re-revisions, with aseptic loosening (n = 8) and PJI (n = 8) being the most common reasons. There were two non-re-revised stacked cone constructs that had signs of radiographic loosening. The mean KSS was 54.

CONCLUSIONS

Stacked cones demonstrated modest survivorship at a mean five-year follow-up with a low rate of aseptic loosening. However, 50% of these cases required a reoperation, highlighting this complex cohort and selection bias to those receiving stacked cones.

Critical Design Parameters of Tantalum-Based Comb Structures to Manipulate Mammalian Cell Morphology

Mammalian tissues and cells often orient naturally in specific patterns to function effectively. This cellular alignment is influenced by the chemical nature and topographic features of the extracellular matrix. In implants, a range of different materials have been used in vivo. Of those, tantalum and its alloys are promising materials, especially in orthopedic implant applications. Previous studies have demonstrated that nano- and micro-scale surface features, such as symmetric comb structures, can significantly affect cell behavior and alignment. However, patterning need not be restricted to symmetric geometries, and there remains a gap in knowledge regarding how cells respond to asymmetric comb structures, where the widths of the trenches and lines in the comb differ. This study aims to address this gap by examining how Vero cells (cells derived from an African green monkey) respond when applied to tantalum and tantalum/silicon oxide asymmetric comb structures having fixed trench widths of 1 μm and line widths ranging from 3 μm to 50 μm. We also look at the cell responses on inverted patterns, where the line widths were fixed at 1 μm while trench widths varied. The orientation and morphology of the adherent cells were analyzed using fluorescence confocal microscopy and scanning electron microscopy. Our results indicate that the widths of the trenches and lines are important design parameters influencing cell behavior on asymmetric comb structures. Furthermore, the ability to manipulate cell morphology using these structures decreased when parts of the tantalum lines were replaced with silicon oxide.

On design, fabrication, and pre-clinical validation of customized 3D-printed dental implant assembly

In the past few decades, 3D-printed dental implants have been manufactured, and significant studies have demonstrated the pre-clinical validation of such systems. However, studies have yet to tackle the ever-present issue of preventing the jumping gap to enhance overall outcomes. The present study details the utilization of patient computed tomography (CT) data to design and subsequently fabricate a multi-component customized dental implant assembly and customized instruments using direct metal laser sintering (DMLS) technology. The workflow was validated for two patient data sets (cases 1 and 2), which were used to render and print custom implant assemblies; the simulation data for these were compared with a commercially available solution. The present study incorporated a prototype stage as well as subjecting the customized implant assemblies to both static (Case 1: 38.89-77.81 MPa vs 75.47-158.09 MPa; Case 2: 83.95-106.65 MPa vs 55.23-126.57 MPa) and dynamic finite element analysis (Case 1: 41.08-84.09 MPa vs 75.45-187.91 MPa; Case 2: 106.81-108.70 MPa vs 79.18-135.48 MPa) along with resonance frequency analysis (Case 1: 7763.2 Hz vs 7003.6 Hz; Case 2: 7910.1 Hz vs 7102.1 Hz) as well as residual stress analysis. The assembly's stress patterns and resonance frequencies were evaluated against a commercially available implant system. It was observed that the customized implant assemblies tended to outperform the commercially available solution in most simulated scenarios.

Advances in 3D-printed scaffold technologies for bone defect repair: materials, biomechanics, and clinical prospects

The treatment of large bone defects remains a significant clinical challenge due to the limitations of current grafting techniques, including donor site morbidity, restricted availability, and suboptimal integration. Recent advances in 3D bioprinting technology have enabled the fabrication of structurally and functionally optimized scaffolds that closely mimic native bone tissue architecture. This review comprehensively examines the latest developments in 3D-printed scaffolds for bone regeneration, focusing on three critical aspects: (1) material selection and composite design encompassing metallic; (2) structural optimization with hierarchical porosity (macro/micro/nano-scale) and biomechanical properties tailored; (3) biological functionalization through growth factor delivery, cell seeding strategies and surface modifications. We critically analyze scaffold performance metrics from different research applications, while discussing current translational barriers, including vascular network establishment, mechanical stability under load-bearing conditions, and manufacturing scalability. The review concludes with a forward-looking perspective on innovative approaches such as 4D dynamic scaffolds, smart biomaterials with stimuli-responsive properties, and the integration of artificial intelligence for patient-specific design optimization. These technological advancements collectively offer unprecedented opportunities to address unmet clinical needs in complex bone reconstruction.

Progress of porous tantalum surface-modified biomaterial coatings in bone tissue engineering

Tantalum (Ta) metal has emerged as a prominent material within the realm of bone tissue engineering, owing to its favorable biocompatibility, commendable mechanical attributes, and notable biological properties such as osteoconductivity, osteoinductivity, and angiogenic potential. However, as clinical applications have expanded, Ta implants have unveiled a spectrum of limitations. Consequently, porous tantalum (PTa) has garnered escalating interest, attributable to its unique microstructural attributes, tunable mechanical characteristics, and inherent biocompatibility. Various methodologies have been proposed to modify the surface of PTa, with the aim of accelerating and enhancing osseous integration while fostering more robust osseointegration. Strategic surface modifications have the potential to augment the inherent advantages of PTa, thereby offering diverse avenues for exploration within the realm of surface effects on PTa. This review elucidates the ongoing research endeavors concerning diverse biomaterial coatings applied to PTa surfaces in the context of bone tissue engineering.

Acetabular Augments Used in Revision Hip Arthroplasty: Minimum 10-year Follow-Up of Implant Survivorships, Functional Scores, and Radiographic Outcomes

BACKGROUND

Acetabular bone loss is a major challenge in the setting of revision total hip arthroplasty (THA). Porous tantalum augments have emerged as a viable solution to acetabular bone loss in revision THA. The purpose of this study was to evaluate the survivorship, clinical, and radiological outcomes of these implants.

METHODS

We identified 104 augment implants from our retrospective chart review of revision THA from June 2003 to July 2013. Of these patients, 75 (72.1%) were women, the mean age at surgery was 66 years (range, 27 to 87), and the mean follow-up was 13.2 years (range, 0.25 to 18.2). Kaplan-Meier survival analysis was performed, with failure defined as revision for aseptic loosening of the acetabular reconstruction.

RESULTS

There was significant improvement in the Harris Hip Score from 40.0 to 77.3 (P < 0.001) and the Oxford Hip Score from 14.9 to 36.3 (P < 0.001). Survivorship for failure due to aseptic loosening was 98.8% (95% CI [confidence interval] 96.4 to 100) at 24 months with 60 hips at risk, and 90.4% (95% CI 83.0 to 97.8) at 60 and 120 months with 38 and 18 hips at risk, respectively. The overall number of complications was 34 (32.7%). Of these complications, 21 (20.2%) required repeat revision surgery. The revision rate due to aseptic loosening of the augment, infection, dislocation, aseptic loosening of the femoral component, reconstruction failure, and heterotopic ossification was seven (6.7%), five (4.8%), four (3.8%), two (1.9%), two (1.9%), and one (0.96%), respectively.

CONCLUSIONS

Treatment of acetabular defects during revision THA using porous tantalum augments provides acceptable implant survivorship and favorable clinical outcomes at mid-term (5 to 10 years) and long-term (> 10 years) follow-up.

Early radiographic evaluation of an anatomic porous tantalum tibia: A prospective, multi-center, non-randomized clinical study

BACKGROUND

Excellent survival rates have been reported for total knee arthroplasty (TKA) performed with cementless porous metal tibial components. More data, however, is necessary to assess the survival and radiographic results of modular implants with anatomic designs. The purpose of this study was to investigate the early radiographic, survival, and clinical outcomes of a cementless tantalum metal tibial implant with a modular anatomic component.

METHODS

An early follow-up of a prospective, multi-center, non-randomized outcomes study of patients who received cementless tibial implants in primary TKA between 2018 and 2020 was performed. A total of 148 implants were available for review. Radiographs, the Forgotten Joint Score (FJS-12), Oxford Knee Score (OKS), patient satisfaction, and adverse events were collected for at least two-years post-operative. A minimum of two-years follow-up was available for 119 patients and evaluated for progressive radiolucent lines (RLLs).

RESULTS

The mean follow-up was 2.2 ± 0.6 years, and the two-year implant survival rate was 98.59% (95% C.I.: 94.46, 99.64) with no aseptic revisions during the follow-up period. Progressive tibial RLLs were present in 3.4% of patients at two-years follow-up, but were all less than 2 mm with all combined RLLs less than 4 mm. The FJS-12 and OKS all significantly (p < 0.0001) increased and exceeded their respective minimal clinical important differences, and 93% of patients were satisfied at two-years follow-up.

CONCLUSION

This study supports excellent survivorship, clinical and patient reported outcomes using cementless, fixed bearing TKA with minimal complications at early follow-up. Further follow-up is necessary to confirm the sustainability of the clinical outcomes and to evaluate mid- to long-term survivorship.

Evolution of Metals and Alloys in Orthopedics with Their Relevance in Osteoporosis

Background

The evolution of metals and alloys in orthopedics has significantly improved the management of bone-related disorders, particularly osteoporosis, where decreased bone density and fragility complicate implant stability and healing. Traditional materials such as stainless steel and cobalt-chromium alloys provided strength and wear resistance but were associated with challenges like stress shielding and implant loosening.

Materials and Methods

To address these limitations, titanium alloys emerged as a superior alternative due to their biocompatibility, lightweight nature, and bone-like elasticity, making them suitable for osteoporotic patients. Recent advancements have led to the development of magnesium-based biodegradable implants and nitinol (shape-memory alloy), which enable minimally invasive procedures and provide dynamic support. Additionally, porous and bioactive coatings, such as hydroxyapatite (HA), have been introduced to enhance osseointegration and implant fixation in compromised bone.

Results

The integration of pharmacological strategies, such as bisphosphonates and sclerostin antibodies, with advanced implant surfaces has further enhanced bone regeneration. Emerging innovations, including 3D-printed personalized implants and smart alloys capable of adapting to physiological changes, show promise for improved long-term stability and faster recovery in osteoporotic patients.

Conclusion

The continuous development of orthopedic materials has paved the way for more effective treatments for osteoporosis, addressing key challenges such as implant stability, stress shielding, and bone regeneration. Innovations in bioactive coatings, biodegradable metals, and personalized implants represent the future of orthopedic care, offering improved outcomes for patients with compromised bone health. However, continuous research is essential to optimize these technologies for broader clinical applications.

Elevated Blood Tantalum Concentrations in Patients Following Reconstruction of Severe Acetabular Defects in Total Hip Arthroplasty Using Modular Tantalum Augments in Combination With Uncemented Tantalum Cups

BACKGROUND

The reconstruction of acetabular defects in total hip arthroplasty (THA) can be challenging. An option to treat uncontained acetabular defects is to use modular tantalum augments in combination with cementless press-fit cups. However, modularity is associated with an increased risk of debonding and mechanical failure. In addition, metal wear particles can be released due to micromotions at the implant interface. Clinical data on the long-term results of this treatment strategy is limited. The purposes of this study were: (1) to evaluate the clinical and radiological outcome of complex THA using modular trabecular metal augments and uncemented revision cups; (2) to investigate the blood tantalum concentrations in these patients at mid-term (mean 4.5 year) follow-up; and (3) to report complications and mechanisms of failure related to this procedure.

METHODS

In this single-center study, we retrospectively reviewed data from a consecutive cohort of 27 patients who underwent complex acetabular defect reconstruction using a modular tantalum acetabular augment in combination with an uncemented tantalum cup. We evaluated the implant survival, and the radiological and clinical outcomes after a mean follow-up of 4.5 years (standard deviation 2.1; range 2.5 to 10.6 years) using patient-reported outcome scores. Blood samples were analyzed regarding tantalum concentration and compared with a control group.

RESULTS

The cumulative survival rate at 4.5 years with the end point "revision of the acetabular component for aseptic loosening" was 94.4% (95% confidence interval [CI] 71.6 to 99.2) and 82.9% (95% CI 60.5 to 93.3) for the end point "revision for any reason." The patient-reported outcome scores improved significantly up to the latest follow-up, and radiographic data showed no signs of loosening or implant migration. Median blood tantalum concentrations were significantly higher in the study group (0.15 μg/L) compared to the control group (0.002 μg/L) (P < .001).

CONCLUSIONS

This study demonstrated acceptable clinical and radiological results of cementless revision THA using modular trabecular metal implants for the reconstruction of large acetabular defects. Tantalum concentrations were significantly higher in patients who had tantalum implants compared to the control group; however, the systemic and local effects of an increased tantalum exposure are not yet fully understood and have to be further investigated.

Precision pore structure optimization of additive manufacturing porous tantalum scaffolds for bone regeneration: A proof-of-concept study

Currently, the treatment of bone defects in arthroplasty is a challenge in clinical practice. Nonetheless, commercially available orthopaedic scaffolds have shown limited therapeutic effects for large bone defects, especially for massiveand irregular defects. Additively manufactured porous tantalum, in particular, has emerged as a promising material for such scaffolds and is widely used in orthopaedics for its exceptional biocompatibility, osteoinduction, and mechanical properties. Porous tantalum has also exhibited unique advantages in personalised rapid manufacturing, which allows for the creation of customised scaffolds with complex geometric shapes for clinical applications at a low cost and high efficiency. However, studies on the effect of the pore structure of additively manufactured porous tantalum on bone regeneration have been rare. In this study, our group designed and fabricated a batch of precision porous tantalum scaffolds via laser powder bed fusion (LPBF) with pore sizes of 250 μm (Ta 250), 450 μm (Ta 450), 650 μm (Ta 650), and 850 μm (Ta 850). We then performed a series of in vitro experiments and observed that all four groups showed good biocompatibility. In particular, Ta 450 demonstrated the best osteogenic performance. Afterwards, our team used a rat bone defect model to determine the in vivo osteogenic effects. Based on micro-computed tomography and histology, we identified that Ta 450 exhibited the best bone ingrowth performance. Subsequently, sheep femur and hip defect models were used to further confirm the osteogenic effects of Ta 450 scaffolds. Finally, we verified the aforementioned in vitro and in vivo results via clinical application (seven patients waiting for revision total hip arthroplasty) of the Ta 450 scaffold. The clinical results confirmed that Ta 450 had satisfactory clinical outcomes up to the 12-month follow-up. In summary, our findings indicate that 450 μm is the suitable pore size for porous tantalum scaffolds. This study may provide a new therapeutic strategy for the treatment of massive, irreparable, and protracted bone defects in arthroplasty.

Cementless fixation in total joint arthroplasty: Factors impacting osseointegration

•The success of cementless fixation in TJA depends on a multitude of factors including biological, mechanical, implant, surgical, and material properties.•Biologic fixation has become the primary mode of fixation for the majority of primary total hip arthroplasty (THA) surgeries done today in the United States (US) due to its low complication rate and superior longevity compared to cemented fixation.•Cementless fixation has yet to gain wider acceptance in total knee arthroplasty (TKA) and hip hemiarthroplasty due to several factors including host bone quality, implant design, and surgical technique.•Understanding a) the properties of the different biomaterials, b) the bone-implant interface characteristics of the different ingrowth and ongrowth surfaces, and c) the various factors that affect osseointegration can lead to:i)appropriate choice of implants for individual patients with consequent increase in revision-free survival, andii)the development of new techniques that can reduce the risk of aseptic loosening.

Trabecular metal collars in endoprosthetic replacements: do they osseointegrate?

Aims

Limb salvage surgery (LSS) is the primary treatment option for primary bone malignancy. It involves the removal of bone and tissue, followed by reconstruction with endoprosthetic replacements (EPRs) to prevent amputation. Trabecular metal (TM) collars have been developed to encourage bone ingrowth (osseointegration (OI)) into EPRs. The primary aim of this study was to assess whether OI occurs when TM collars are used in EPRs for tumour.

Methods

A total of 124 patients from July 2010 to August 2021 who underwent an EPR for tumour under the West of Scotland orthopaedic oncology team were identified. Overall, 81 patients (65%) met the inclusion criteria, and two consultants independently analyzed radiographs at three and 12 months, as well as the last radiograph, using a modified version of the Stanford Radiological Assessment System.

Results

OI of the TM collar occurred in approximately 65% of patients at last radiograph. The percentage of patients with OI at three months (65.4%) reflected the 12-month (65%) and long-term (64.4%) follow-up. The median amount of OI across all radiographs was one at all three timepoints, with only five cases (11.1%) showing OI in all four zones at last radiograph. Radiolucency at the bone:collar junction was present in 23 cases (28.4%) at three months, but only four (6.7%) showed progression of this at 12 months. The interobserver reliability was found to be highly reliable in all parameters (p < 0.001).

Conclusion

OI occurs in approximately 65% of TM collars, and is similar at three months, 12 months, and last radiograph. The extent of OI at the bone:collar junction was found to have decreased at longer-term follow-up. Furthermore, radiolucency at the bone-collar impact junction does occur in some patients but only a low number will show radiolucency progression at longer-term follow-up.

Reconstruction of severe acetabular defects (Paprosky type III A) in total hip arthroplasty using modular tantalum augments in combination with a cemented cup

PURPOSE

Acetabular defect reconstruction can be a complex and challenging surgical procedure, with stable long-term fixation of the implants remaining the ultimate goal. The purpose of this study was (1) to evaluate the radiological and clinical outcome of complex acetabular reconstruction surgery with the use of modular tantalum TM augments in combination with cemented revision cups; (2) to investigate blood tantalum concentrations in these patients; and (3) to report complications and mechanisms of failure related to this procedure at mid-term follow-up (mean 4.5 years).

METHODS

We retrospectively reviewed 29 patients (29 hips) with severe acetabular bone loss (Paprosky type III A) reconstructed using a modular tantalum TM augment in combination with a cemented cup. We evaluated the implant survival and the radiological and clinical outcomes after a mean follow-up of 4.5 years (SD 2.2; range 8.4 - 2.1 years) using patient reported outcome scores (PROMs). Blood samples were analysed regarding tantalum concentration and compared with a control group.

RESULTS

The cumulative survival rate at 4.5 years with the endpoint "revision of the acetabular component for any reason" was 96.2% (95% Confidence Interval 75.7-99.5). The PROMs improved significantly up to the latest follow-up, and radiographic data showed only one patient with signs of initial implant migration with a broken screw and a change of the position of the augment and the cup. Mean blood tantalum concentrations were significantly higher in the study group (0.16 µg/L) compared to the control group (0.002 µg/L) (P < 0.001).

CONCLUSIONS

This study has demonstrated good mid-term (mean 4.5 years) clinical and radiological outcomes of modular tantalum TM augments in combination with a cemented cup for the reconstruction of major acetabular defects. Mean blood tantalum concentrations were increased in patients with stable tantalum implants compared to healthy controls.

Prospective randomized study on the effect of concurrent bone filling of tibial peg holes in cementless total knee arthroplasty

BACKGROUND

In total knee arthroplasty (TKA), cementless fixation is initially weaker than cement fixation. This study aimed to examine whether filling the tibial peg holes with bone improves initial fixation strength in cementless TKA.

METHODS

This prospective, comparative study examined 88 joints in 66 patients randomized to the bone filling (48 joints) or conventional group (no bone filling; 40 joints). All patients underwent TKA with the NexGen® trabecular metal modular tibial component. In the bone filling group, resected cancellous bone was filled into the peg holes before insertion of the tibial component. We performed clinical and plain radiographic evaluations after the operation and measured bone mineral density (BMD) at five sites below the component at 1, 3, 6, and 12 months postoperatively.

RESULTS

Operative time and clinical evaluations were not significantly different. Plain radiography showed significant longitudinal thickening of the trabecula below the peg (P<0.05) and decreased occurrence of reactive lines (P=0.07) in the bone filling group compared with the conventional group. BMD was significantly higher in the bone filling group in the medial region below the peg at 1, 3, and 6 months and in the central region at 1 and 3 months (all P<0.05).

CONCLUSIONS

When using the NexGen trabecular metal modular tibial component, concurrent peg hole bone filling increases the initial component fixation strength. Possible effects on long-term stabilization warrant further study.

Trabecular Bone Remodeling After Posterior Lumbar Interbody Fusion: Comparison of Three-Dimensional Porous Tantalum and Titanium-Coated Polyetheretherketone Interbody Cages

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

The criteria for determining completion of intervertebral stability after posterior lumbar interbody fusion (PLIF) remain controversial. Several new radiological indicators of bone growth and osteointegration have been established. We compared computed tomography (CT) findings related to osteointegration after PLIF with interbody cages of two different materials and designs.

METHODS

We retrospectively analyzed data from 103 patients who underwent PLIF with three-dimensional porous tantalum (Tn) cages or titanium-coated polyetheretherketone (TiP) cages. CT images obtained 3 months and 1 year after surgery were examined for trabecular bone remodeling (TBR), cancellous condensation (CC), and vertebral endplate cyst (VEC) formation. The incidences of each finding were compared by cage type, and rates of instrument failure and pseudarthrosis were determined.

RESULTS

Three months postoperatively, 87% of the levels with Tn cages exhibited TBR, whereas 96% of those with TiP cages did not (P < .001). Most levels with Tn cages levels exhibited TBR and no CC 3 months (81%) and 1 year (94%) after surgery. Although 78% of levels with TiP cages exhibited CC and no TBR 3 months after surgery, 59% exhibited both CC and TBR 1 year after surgery. Significantly fewer VECs formed around the Tn cages than around the TiP cages both 3 months (P = .002) and 1 year (P < .001) after surgery. Implant-related problems occurred at levels that exhibited neither TBR nor CC.

CONCLUSIONS

The porous tantalum cage may enable intervertebral stability that is comparable to bony fusion soon after surgery.

Acetabular Distraction: Promising 5-Year Outcomes for the Treatment of Chronic Pelvic Discontinuity

BACKGROUND

Severe acetabular bone loss encountered during revision total hip arthroplasty (THA) poses a clinical challenge. In cases involving pelvic discontinuity, where the ilium is separated superiorly from the inferior ischiopubic segment through the acetabulum, acetabular distraction may be used to restore the biomechanics of the hemipelvis. This technique allows for correct sizing of the acetabulum, and the subsequent peripheral distraction and medial compression at the discontinuity provide initial mechanical stability and biological fixation as bone in growth occurs. Accordingly, this study aimed to assess long-term 5-year outcomes following acetabular distraction across 2 institutions.

METHODS

We retrospectively identified all patients who underwent revision THA in which the acetabular distraction technique was performed for the treatment of chronic pelvic discontinuity between 2002 and 2018. Demographic, operative, and clinical postoperative data were collected. Clinical endpoints included postoperative radiographic outcomes, complications requiring additional surgery, and reoperation for all causes. Only patients who had a minimum 5-year follow-up were included in this study.

RESULTS

A total of 15 patients (Paprosky IIC: one patient, 6.7%; Paprosky IIIA: 5 patients, 33.3%; Paprosky IIIB: 9 patients, 60%) who had a mean follow-up time of 9 years (range, 5.1 to 13.5) were analyzed. Porous tantalum augments were used in 11 (73.3%) cases to primarily address posteriorsuperior defects (100%). There were 4 (26.7%) patients that required reoperation, only 2 of which were for indications related to the acetabular construct, leading to an overall survivorship of 86.7%. Both patients had a prior revision THA before the implementation of the distraction technique. Evidence of bridging callus formation was reported radiographically for 14 (93.3%) patients at the time of the last clinical follow-up.

CONCLUSIONS

For patients who have chronic pelvic discontinuity, acetabular distraction shows promising long-term outcomes. Even so, larger multi-center studies are needed to better support the efficacy of this technique.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Total hip arthroplasty with porous tantalum trabecular metal pads in patients with Crowe IV developmental dysplasia of the hip: a midterm followup study

PURPOSE

Crowe IV developmental dysplasia of the hip (DDH) is a catastrophic hip disease. Moreover, obtaining ideal clinical efficacy in conventional total hip arthroplasty (THA) is often difficult. In this study, we aimed to assess the mid-term clinical results of THA with porous tantalum trabecular metal (TM) pads for acetabular reconstruction in the treatment of Crowe IV DDH.

METHODS

A cohort of 28 patients (32 hips) diagnosed with Crowe type IV DDH who underwent acetabular reconstruction during THA using TM pads with scheduled follow-up between 2011 and 2018, were included in this study. Eight cases were men and 24 were women, with a mean age of 48.4 years (range, 36-72 years) and a mean follow-up was 74.3 months (range, 42-132 months). All patients underwent acetabular reconstruction using TM pads and total hip replacement with subtrochanteric osteotomy.

RESULTS

At the final follow-up, 28 hips (87.5%) demonstrated mild or no postoperative limping. The Harris Hip Score improved from 58.4 ± 10.6 preoperatively to 85.6 ± 8.9. The mean pain, stiffness, and function scores on the Western Ontario and McMaster University Osteoarthritis index were 86.5 ± 10.2, 87.3 ± 12.4 and 85.4 ± 11.6 respectively. The mean score of patient satisfaction was 90.4 ± 7.6. Additionally, the SF-12 physical summary score was 41.8 ± 5.6 and the SF-12 mental summary score was 51.6 ± 5.4. TM construct survivorship due to all-cause failure was 90.6% at 5 years with 3 hips at risk, 87.5% at 10 years with 4 hips at risk. The survivorship due to failure from aseptic loosening was 96.9% at 5 years with 1hips at risk and 93.75% at 10 years with 2 hips at risk.

CONCLUSION

This study demonstrated satisfactory mid-term clinical and radiological results with the application of TM pads for acetabular reconstruction combined with THA in patients with Crowe IV DDH.

TRIAL REGISTRATION NUMBER

ChiCTR1800014526, Date: 18/01/2018.

Effect of M2-macrophage treated lymphatic endothelial cells on angiogenesis that promoted osteointegration

Early vascularization plays an essential role during the whole process in bone regeneration because of the function of secreting cytokines, transporting nutrients and metabolic wastes. As the preliminary basis of bone repair, angiogenesis is regulated by immune cells represented by macrophages to a great extent. However, with the discovery of the endolymphatic circulation system inside bone tissue, the role of vascularization became complicated and confusing. Herein, we developed a macrophage/lymphatic endothelial cells (LECs)/human umbilical vein endothelial cells (HUVECs) co-culture system to evaluate the effect of macrophage treated lymphatic endothelial cells on angiogenesis in vitro and in vivo. In this study, we collected the medium from macrophage (CM) for LECs culture. We found that CM2 could promote the expression of LECs markers and migration ability, which indicated the enhanced lymphogenesis. In addition, the medium from LECs was collected for culturing HUVECs. The CM2-treated LECs showed superior angiogenesis property including the migration capacity and expression of angiogenetic markers, which suggested the superior vascularization. Rat femoral condyle defect model was applied to confirm the hypothesis in vivo. Generally, M2-macrophage treated LECs showed prominent angiogenetic potential coupling with osteogenesis.

Survivorship and complications of cementless compared to cemented posterior-stabilized total knee arthroplasties: A systematic review and meta-analysis

PURPOSE

Controversy exists on the best fixation for total knee arthroplasty (TKA). Non-cemented fixation has been theorized to improve patient outcomes and longevity of implantation but no study has focused on comparison between cemented or cementless posterior-stabilized implants despite being the most commonly or second most frequently utilized implant in most total knee replacement registries.

METHODS

Inclusion criteria with observational and interventional papers, and review articles that focused on patients with cementless and cemented PS TKAs were used to analyze outcomes such as implant survivorship, complication, or revision rates. Using a combination of keywords, a systematic search was performed on Medline (PubMed), Embase, and Cochrane Library for Meta-Analysis.

RESULTS

When using the specified criteria, only 8 studies were selected for full-text analysis and meta-analysis after eliminating screening duplicates, titles, and abstracts without full-text access. These eight studies contain 1652 patients, 693 in the non-cemented Group, and 959 in the cemented total knee prosthesis Group. The meta-analysis revealed the advantage of cementless fixation over cemented fixation in implant survivorship, with 0.6% and 2.6% of aseptic loosening in each Group. The cumulative survival at 12 years was 97.4% for the cementless Group and 89.2% for the cemented Group. The subgroup with a stem showed a positive outcome for cementless fixation over cemented fixation regarding implant survivorship. No differences between the cemented and cementless TKAs were observed in patient-reported outcomes, revision rates, or radiolucent line development.

CONCLUSION

We observed comparable rates for cemented and cementless posterior-stabilized TKAs over a medium-term follow-up period.

Green Synthesis and Biosafety Assessment of MXene

The rise of MXene-based materials with fascinating physical and chemical properties has attracted wide attention in the field of biomedicine, because it can be exploited to regulate a variety of biological processes. The biomedical applications of MXene are still in its infancy, nevertheless, the comprehensive evaluation of MXene's biosafety is desperately needed. In this review, the composition and the synthetic methods of MXene materials are first introduced from the view of biosafety. The evaluation of the interaction between MXene and cells, as well as the safety of different forms of MXene applied in vivo are then discussed. This review provides a basic understanding of MXene biosafety and may bring new inspirations to the future applications of MXene-based materials in biomedicine.

Selective Laser Melting of the Porous Ta Scaffold with Mg-Doped Calcium Phosphate Coating for Orthopedic Applications

Addressing the repair of large-scale bone defects has become a hot research topic within the field of orthopedics. This study assessed the feasibility and effectiveness of using porous tantalum scaffolds to treat such defects. These scaffolds, manufactured using the selective laser melting (SLM) technology, possessed biomechanical properties compatible with natural bone tissue. To enhance the osteogenesis bioactivity of these porous Ta scaffolds, we applied calcium phosphate (CaP) and magnesium-doped calcium phosphate (Mg-CaP) coatings to the surface of SLM Ta scaffolds through a hydrothermal method. These degradable coatings released calcium and magnesium ions, demonstrating osteogenic bioactivity. Experimental results indicated that the Mg-CaP group exhibited biocompatibility comparable to that of the Ta group in vivo and in vitro. In terms of osteogenesis, both the CaP group and the Mg-CaP group showed improved outcomes compared to the control group, with the Mg-CaP group demonstrating superior performance. Therefore, both CaP and magnesium-CaP coatings can significantly enhance the osseointegration of three-dimensional-printed porous Ta, thereby increasing the surface bioactivity. Overall, the present study introduces an innovative approach for the biofunctionalization of SLM porous Ta, aiming to enhance its suitability as a bone implant material.

Additively manufactured Ti-Ta-Cu alloys for the next-generation load-bearing implants

Bacterial colonization of orthopedic implants is one of the leading causes of failure and clinical complexities for load-bearing metallic implants. Topical or systemic administration of antibiotics may not offer the most efficient defense against colonization, especially in the case of secondary infection, leading to surgical removal of implants and in some cases even limbs. In this study, laser powder bed fusion was implemented to fabricate Ti3Al2V alloy by a 1:1 weight mixture of CpTi and Ti6Al4V powders. Ti-Tantalum (Ta)-Copper (Cu) alloys were further analyzed by the addition of Ta and Cu into the Ti3Al2V custom alloy. The biological, mechanical, and tribo-biocorrosion properties of Ti3Al2V alloy were evaluated. A 10 wt.% Ta (10Ta) and 3 wt.% Cu (3Cu) were added to the Ti3Al2V alloy to enhance biocompatibility and impart inherent bacterial resistance. Additively manufactured implants were investigated for resistance against Pseudomonas aeruginosa and Staphylococcus aureus strains of bacteria for up to 48 h. A 3 wt.% Cu addition to Ti3Al2V displayed improved antibacterial efficacy, i.e. 78%-86% with respect to CpTi. Mechanical properties for Ti3Al2V-10Ta-3Cu alloy were evaluated, demonstrating excellent fatigue resistance, exceptional shear strength, and improved tribological and tribo-biocorrosion characteristics when compared to Ti6Al4V. In vivo studies using a rat distal femur model revealed improved early-stage osseointegration for alloys with 10 wt.% Ta addition compared to CpTi and Ti6Al4V. The 3 wt.% Cu-added compositions displayed biocompatibility and no adverse inflammatory response in vivo. Our results establish the Ti3Al2V-10Ta-3Cu alloy's synergistic effect on improving both in vivo biocompatibility and microbial resistance for the next generation of load-bearing metallic implants.

The Effect of Doping on the Electrical and Dielectric Properties of Hydroxyapatite for Medical Applications: From Powders to Thin Films

Recently, the favorable electrical properties of biomaterials have been acknowledged as crucial for various medical applications, including both bone healing and growth processes. This review will specifically concentrate on calcium phosphate (CaP)-based bioceramics, with a notable emphasis on hydroxyapatite (HA), among the diverse range of synthetic biomaterials. HA is currently the subject of extensive research in the medical field, particularly in dentistry and orthopedics. The existing literature encompasses numerous studies exploring the physical-chemical, mechanical, and biological properties of HA-based materials produced in various forms (i.e., powders, pellets, and/or thin films) using various physical and chemical vapor deposition techniques. In comparison, there is a relative scarcity of research on the electrical and dielectric properties of HA, which have been demonstrated to be essential for understanding dipole polarization and surface charge. It is noteworthy that these electrical and dielectric properties also offer valuable insights into the structure and functioning of biological tissues and cells. In this respect, electrical impedance studies on living tissues have been performed to assess the condition of cell membranes and estimate cell shape and size. The need to fill the gap and correlate the physical-chemical, mechanical, and biological characteristics with the electrical and dielectric properties could represent a step forward in providing new avenues for the development of the next-generation of high-performance HA-doped biomaterials for future top medical applications. Therefore, this review focuses on the electrical and dielectric properties of HA-based biomaterials, covering a range from powders and pellets to thin films, with a particular emphasis on the impact of the various dopants used. Therefore, it will be revealed that each dopant possesses unique properties capable of enhancing the overall characteristics of the produced structures. Considering that the electrical and dielectric properties of HA-based biomaterials have not been extensively explored thus far, the aim of this review is to compile and thoroughly discuss the latest research findings in the field, with special attention given to biomedical applications.

The effect of porous compliance bushings in a dental implant on the distribution of occlusal loads

Porous dental implants are clinically used, but the mechanism of load distribution for stepped implant shaft surrounded by compliance bushings is still not known, especially for different bone conditions. The aim of the study was to assess the impact of the design of a dental implant with compliance bushings (CBs) on the occlusal load distribution during primary and secondary stability using finite element simulation (FEA), with a distinction between low and high quality cervical support under primary stability. The FEA of the oblique occlusal load transfer (250 N; 45°) was carried out for implants under variable bone conditions. The stepped shaft in the intermediate part of the dental implant was surrounded by CBs with an increasing modulus of elasticity of 2, 10 and 50 GPa. With a smaller Young's modulus of the bushings the increase of stress in the trabecular bone indicated that more bone tissue can be protected against disuse. The beneficial effect for the trabecular bone derived from the reduction of the stiffness of the bushings in relation to the loss of the implant's load bearing ability can be assessed using the FEM method.

Research progress and perspective of metallic implant biomaterials for craniomaxillofacial surgeries

Craniomaxillofacial bone serves a variety of functions. However, the increasing number of cases of craniomaxillofacial bone injury and the use of selective rare implants make the treatment difficult, and the cure rate is low. If such a bone injury is not properly treated, it can lead to a slew of complications that can seriously disrupt a patient's daily life. For example, premature closure of cranial sutures or skull fractures can lead to increased intracranial pressure, which can lead to headaches, vomiting, and even brain hernia. At present, implant placement is one of the most common approaches to repair craniomaxillofacial bone injury or abnormal closure, especially with biomedical metallic implants. This review analyzes the research progress in the design and development of degradable and non-degradable metallic implants in craniomaxillofacial surgery. The mechanical properties, corrosion behaviours, as well as in vitro and in vivo performances of these materials are summarized. The challenges and future research directions of metallic biomaterials used in craniomaxillofacial surgery are also identified.

Metallic Materials for Bone Repair

Repair of large bone defects caused by trauma or disease poses significant clinical challenges. Extensive research has focused on metallic materials for bone repair because of their favorable mechanical properties, biocompatibility, and manufacturing processes. Traditional metallic materials, such as stainless steel and titanium alloys, are widely used in clinics. Biodegradable metallic materials, such as iron, magnesium, and zinc alloys, are promising candidates for bone repair because of their ability to degrade over time. Emerging metallic materials, such as porous tantalum and bismuth alloys, have gained attention as bone implants owing to their bone affinity and multifunctionality. However, these metallic materials encounter many practical difficulties that require urgent improvement. This article systematically reviews and analyzes the metallic materials used for bone repair, providing a comprehensive overview of their morphology, mechanical properties, biocompatibility, and in vivo implantation. Furthermore, the strategies and efforts made to address the short-comings of metallic materials are summarized. Finally, the perspectives for the development of metallic materials to guide future research and advancements in clinical practice are identified.

Uncemented trabecular metal high-flex posterior-stabilized monoblock total knee arthroplasty in patients aged 60 years or younger

BACKGROUND

Uncemented trabecular metal (TM) monoblock tibial components in total knee arthroplasty (TKA) have shown excellent clinical results for up to 10 years. However, these studies were performed in highly specialized units, with few surgeons and often excluding knees with secondary osteoarthritis (OA), severe malalignments and previous surgery. The purpose of this study was to investigate implant survivorship and clinical and radiological outcome of the uncemented TM high-flex posterior stabilized (PS) monoblock tibial component in routine clinical practice.

METHODS

A retrospective study of 339 knees (282 patients) operated with the implant in routine clinical practice at two hospitals on patients aged 60 years or younger between 2007 and 2015. The operations were performed by 12 surgeons and there were no specific contraindications for use of the implant. Follow up ended in 2020. The status of the implant of deceased patients at death and those not attending follow up was checked with the Swedish Knee Arthroplasty Register. Clinical follow up consisted of clinical investigation, PROMs, and knee X-ray.

RESULTS

Follow up was mean (range) 8.5 (5-13.8) years, and the 8-year survival rate was 0.98 (standard error 0.007). Five patients five knees) were deceased, five knees were revised (none due to aseptic loosening), and 16 patients did not attend the clinical follow up. Forty-four percent of the knees had secondary OA and 45% had had previous operations. 93% were satisfied or very satisfied with the operation and forgotten joint score (FJS) was median (interquartile range) 81 (44-94). Radiographic analysis revealed bone in close contact with the tibial tray and pegs in most cases, and in only 2% of the knees were potential radiolucent lines found.

CONCLUSION

The results indicate that this uncemented implant performs excellently in routine clinical practice and also in younger patients with secondary OA or previous knee operations.

Trabecular Bone Remodeling as a New Indicator of Osteointegration After Posterior Lumbar Interbody Fusion

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

We newly found that trabecular bone remodeling (TBR) often appeared in the fixed adjacent vertebrae during bony fusion. Thus, TBR might indicate osteointegration. Hence, we aimed to investigate whether TBR in the early postoperative period could predict future bony fusion after posterior lumbar interbody fusion (PLIF).

METHODS

We retrospectively analyzed 78 patients who underwent one-level PLIF. Demographic data were reviewed. Using computed tomography (CT) images taken at 3 months and 1 year postoperatively, we investigated the vertebral endplate cyst (VEC) formation, TBR in the vertebral body, cage subsidence, and clear zone around pedicle screw (CZPS).

RESULTS

TBR had high interobserver reliability regardless of cage materials. VECs, TBR, and both were found in 30, 53, and 16 patients at 3 months postoperatively and in 30, 65, and 22 patients at 1 year postoperatively, respectively. The incidence of VEC, which indicates poor fixation, was lower in early (3 months postoperatively) TBR-positive patients, with a significant difference at 1 year postoperatively (3 months, P = .074; 1 year, P = .003). Furthermore, 3 (5.7%) of the 53 early TBR-positive patients had CZPS without instability at 1 year postoperatively. In 25 TBR-negative patients, 1 (4.0%) had pedicle screw cutout requiring reoperation, 1 (4.0%) had pseudarthrosis, and 4 (16%) had CZPS.

CONCLUSIONS

Patients with early TBR (3 months) did not experience pedicle screw cutout nor pseudarthrosis and had significantly fewer VECs than those without early TBR. Thus, TBR may be a new radiological marker of initial fixation after PLIF.

How Can Imbalance in Oral Microbiota and Immune Response Lead to Dental Implant Problems?

Dental implantology is one of the most dynamically developing fields of dentistry, which, despite developing clinical knowledge and new technologies, is still associated with many complications that may lead to the loss of the implant or the development of the disease, including peri-implantitis. One of the reasons for this condition may be the fact that dental implants cannot yield a proper osseointegration process due to the development of oral microbiota dysbiosis and the accompanying inflammation caused by immunological imbalance. This study aims to present current knowledge as to the impact of oral microflora dysbiosis and deregulation of the immune system on the course of failures observed in dental implantology. Evidence points to a strong correlation between these biological disturbances and implant complications, often stemming from improper osseointegration, pathogenic biofilms on implants, as well as an exacerbated inflammatory response. Technological enhancements in implant design may mitigate pathogen colonization and inflammation, underscoring implant success rates.

Transforaminal lumbar interbody fusion with a tantalum cage: lumbar lordosis redistribution and sacral slope restoration with a modified posterior technique

BACKGROUND

Transforaminal lumbar interbody fusion (TLIF), a commonly used procedure in spine surgery, has the advantage of a lower incidence of nerve lesions compared to the posterior lumbar interbody fusion (PLIF) technique. The intersomatic arthrodesis has always been carried out with a single tantalum cage normally used for PLIF. Tantalum is a metal that is particularly used in orthopedic surgery. It has a modulus of elasticity similar to marrow and leads to high primary stability of the implant.

MATERIALS AND METHODS

Our study was a retrospective monocentric observational study evaluating clinical and radiological outcomes of tantalum cages in a modified TLIF technique with posterior instrumentation and autologous and/or homologous posterolateral bone grafting. The aim of the study was to evaluate clinical outcomes and the increase in or redistribution of lumbar lordosis. The intersomatic arthrodesis was always carried out with a single tantalum cage normally used for PLIF to reduce the neurological risk. We retrospectively studied 105 patients who were treated with a modified unilateral TLIF approach by two surgeons between 2013 and 2018. We evaluated the Oswestry Disability Index (ODI), Visual Analogue Scale (VAS) for back pain, global lumbar lordosis, lordosis of L4-sacrum, segmental lordosis of functional motion units that underwent arthrodesis, pelvic tilt, pelvic incidence, and the sacral slope in 77 patients. All patients were suffering from grade III or IV Pfirrmann, instability, or foraminal post-laminectomy stenosis and/or grade I-II degenerative spondylolisthesis or low-grade isthmic spondylolisthesis. They had no significant sagittal imbalance, with a sagittal vertical axis (SVA) of < 5 mm. The average follow-up duration was 30 months.

RESULTS

We achieved excellent clinical results, with only four cases of failure (5.2%). Moreover, we noticed a statistically significant redistribution of lumbar lordosis, with an average percentage increase in L4-S1 lordosis equal to 19.9% (P < 0.001), an average increase in the L4-S1/Lumbar lordosis (LL) ratio from 0.53 to 0.63 (P < 0.001), and a mean percentage increase in sacral slope equal to 7.6% (P < 0.001).

CONCLUSION

Thanks to the properties of tantalum, our modified single-portal TLIF technique is a valid surgical solution to obtain a solid arthrodesis and restore the correct lumbar lordosis distribution while reducing neurological complications and the number of failures.

LEVEL OF EVIDENCE

4 Trial registration statement: retrospective observational study, no trial registration.

Microstructure Optimization for Design of Porous Tantalum Scaffolds Based on Mechanical Properties and Permeability

Porous tantalum (Ta) implants have important clinical application prospects due to their appropriate elastic modulus, and their excellent bone growth and bone conduction ability. However, porous Ta microstructure designs generally mimic titanium (Ti) implants commonly used in the clinic, and there is a lack of research on the influence of the microstructure on the mechanical properties and penetration characteristics, which will greatly affect bone integration performance. This study explored the effects of different microstructure parameters, including the fillet radius of the middle plane and top planes, on the mechanics and permeability properties of porous Ta diamond cells through simulation, and put forward an optimization design with a 0.5 mm midplane fillet radius and 0.3 mm top-plane fillet radius in order to significantly decrease the stress concentration effect and improve permeability. On this basis, the porous Ta structures were prepared by Laser Powder Bed Fusion (LPBF) technology and evaluated before and after microstructural optimization. The elastic modulus and the yield strength were increased by 2.31% and 10.39%, respectively. At the same time, the permeability of the optimized structure was also increased by 8.25%. The optimized microstructure design of porous Ta has important medical application value.

Carpal bone replacement using personalized 3D printed tantalum prosthesis

Objective: Scaphoid and lunate fractures have a relatively high incidence rate. Traditional carpectomy and carpal arthrodesis in the treatment of carpal osteonecrosis will lead to many complications. Three-dimensional (3D) printed tantalum has good biocompatibility and can be designed to match the patient's personalized anatomical carpal structure. This study aims to investigate carpal function and prosthesis-related conditions after carpal bone replacement using 3D printed tantalum prostheses. Methods: From July 2020 to January 2022 at our center, seven patients with osteonecrosis of the carpus received carpal bone replacement using 3D printed tantalum prosthesis. The Disability of the Arm, Shoulder and Hand (DASH) score and patient satisfaction, as well as the Mayo Wrist Scores (Cooney method, modified Green, and O'Brien wrist score), were used to evaluate the preoperative and postoperative wrist function of patients. The Visual Analog Scale (VAS) pain scores were also recorded before and after surgery. The angles of flexion, dorsiflexion, ulnar deviation, and radial deviation were measured using an arthrometer. The grip strength and pinch strength of the operated hand after carpal bone replacement and the contralateral healthy carpus were measured using a dynamometer. Radiographs were taken to confirm the condition and complications of the tantalum prosthesis. Results: All seven patients were followed for 19.6 ± 2.7 months. At the last follow-up, the grip strength of the operated wrist joint after carpal bone replacement was 33.4 ± 2.3 kg, the pinch strength was 8.9 ± 0.7 kg, the flexion was 54.6° ± 0.8°, the dorsiflexion was 54.7° ± 1.7°, the ulnar deviation was 34.6° ± 1.9°, and the radial deviation was 25.9° ± 0.8°, all of which showed no statistically significant difference with the contralateral healthy carpus (p > 0.05). There were significant differences in the VAS, DASH, and MAYO scores between the preoperative and the last follow-up (p < 0.01). Patients had reduced postoperative pain and improved wrist function and range of motion (ROM), and the tantalum prostheses were stable. Conclusion: The 3D printed tantalum brings us new hope, not only for hip or knee replacement, but also for joint replacement of other complex anatomical structures, and patients with other irregular bone defects such as bone tumors and deformity, which could realize personalized treatment and precise medicine.

Static Compressive Behavior and Failure Mechanism of Tantalum Scaffolds with Optimized Periodic Lattice Fabricated by Laser-Based Additive Manufacturing

Porous tantalum (Ta) scaffolds have been extensively used in the clinic for reconstructing bone tissues owing to their outstanding corrosion resistance, biocompatibility, osteointegration, osteoconductivity, and mechanical properties. Additive manufacturing (AM) has an advantage in fabricating patient-specific and anatomical-shape-matching bone implants with controllable and well-designed porous architectures through tissue engineering. The sharp angles of strut joints in porous structures can cause stress concentration, reducing mechanical properties of the structures. In this study, porous Ta scaffolds comprising rhombic dodecahedron lattice unit cells with optimized node radius and porosities of 65%, 75%, and 85% were designed and fabricated by AM. The porous architecture and microstructure were characterized. The compressive behavior and failure mechanism of the material were explored through experimental compression tests and finite element analysis (FEA). Morphological evaluations revealed that the Ta scaffolds are fully interconnected, and the struts are dense. No processing defects and fractures were observed on the surface of struts. The scaffolds exhibited compressive yield strength of 5.8-32.3 MPa and elastic modulus of 0.6-4.5 GPa, comparable to those of human cancellous and trabecular bone. The compressive stress-strain curves of all samples show ductile deformation behavior accompanied by a smooth plateau region. The AM-fabricated rhombic dodecahedron lattice Ta scaffolds exhibited excellent ductility and mechanical reliability and plastic failure due to bending deformation under compressive loading. Deformation and factures primarily occurred at the junctions of the rhombus-arranged struts in the longitudinal section. Moreover, the struts in the middle of the scaffolds underwent a larger deformation than those close to the loading ends. FEA revealed a smooth stress distribution on the rhombic dodecahedron lattice structure with optimized node radius and stress concentration at the junctions of rhombus-arranged struts in the longitudinal section, which is in good agreement with the experimental results. Thus, the AM-fabricated Ta scaffolds with optimized node radius are promising alternatives for bone repair and regeneration.

Understanding the influence of alloying elements on the print quality of powder bed fusion-based metal additive manufacturing: Ta and Cu addition to Ti alloy

Alloy design coupled with metal additive manufacturing (AM) opens many opportunities for materials innovation. Investigating the effect of printing parameters for alloy design is essential to achieve good part quality. Among different factors, laser absorptivity, heat diffusivity, and in situ intermetallic phase formations are critical. In this study, the first step employed was a reduction in Al and V contents in Ti6Al4V to design Ti3Al2V alloy, and further 10 wt.% tantalum (Ta) and 3 wt.% copper (Cu) were added to Ti3Al2V. A synergistic effect of Ta and Cu addition in Ti3Al2V negated their effect with higher porosities in Ti3Al2V-Ta-Cu. Ti3Al2V-Ta composition was more sensitive to the laser power, whereas Ti3Al2V-Ta-Cu to the overall energy density. Understanding the effect of energy density on these alloys' microstructural evolution and mechanical properties highlights the need for process-property optimization during alloy design using AM.

Osseointegration of Tantalum Trabecular Metal in Titanium Dental Implants: Histological and Micro-CT Study

This study aimed to investigate the impact of the Tantalum Trabecular Metal dental implant design on implant stability and the process of osseointegration following its placement in the rabbit femoral condyle. The subjects for the experiment consisted of 10 New Zealand white rabbits. Twenty implants, comprising 10 Trabecular Metal (TM) and 10 Traditional Screw Vent (TSV) implants, were placed into the femoral condyles of these rabbits. The implant type was alternated based on a random sequence. Following a healing period of 8 weeks, the implants were retrieved for further analysis using micro-computed tomography (micro-CT), histological studies, and histomorphometry evaluations. The Bone-to-Implant Contact (BIC) ratio and the Bone Volume (BV) percentage in the region of interest were subsequently assessed. The BIC and BV values between TM and TSV implants were compared using the Student t-test. The TM implants exhibited significantly greater BIC and BV scores. In particular, the BIC percentage was recorded as 57.9 ± 6.5 for the TM implants, as opposed to 47.6 ± 8 for the TSV implants. Correspondingly, the BV percentage was 57 ± 7.3 for the TM implants and 46.4 ± 7.4 for the TSV implants. The bone volume percentage measured using micro-CT evaluation was 89.1 ± 8.7 for the TM implants and 79.1 ± 8.6 for the TSV implants. Given the observed results, it is plausible to suggest that the bone growth surrounding the tantalum mesh could have improved the integration of the bone and facilitated its ingrowth into the TM implant.

Regulating Oxygen Ion Transport at the Nanoscale to Enable Highly Cyclable Magneto-Ionic Control of Magnetism

Magneto-ionics refers to the control of magnetic properties of materials through voltage-driven ion motion. To generate effective electric fields, either solid or liquid electrolytes are utilized, which also serve as ion reservoirs. Thin solid electrolytes have difficulties in (i) withstanding high electric fields without electric pinholes and (ii) maintaining stable ion transport during long-term actuation. In turn, the use of liquid electrolytes can result in poor cyclability, thus limiting their applicability. Here we propose a nanoscale-engineered magneto-ionic architecture (comprising a thin solid electrolyte in contact with a liquid electrolyte) that drastically enhances cyclability while preserving sufficiently high electric fields to trigger ion motion. Specifically, we show that the insertion of a highly nanostructured (amorphous-like) Ta layer (with suitable thickness and electric resistivity) between a magneto-ionic target material (i.e., Co₃O₄) and the liquid electrolyte increases magneto-ionic cyclability from <30 cycles (when no Ta is inserted) to more than 800 cycles. Transmission electron microscopy together with variable energy positron annihilation spectroscopy reveals the crucial role of the generated TaO_x interlayer as a solid electrolyte (i.e., ionic conductor) that improves magneto-ionic endurance by proper tuning of the types of voltage-driven structural defects. The Ta layer is very effective in trapping oxygen and hindering O^2- ions from moving into the liquid electrolyte, thus keeping O^2- motion mainly restricted between Co₃O₄ and Ta when voltage of alternating polarity is applied. We demonstrate that this approach provides a suitable strategy to boost magneto-ionics by combining the benefits of solid and liquid electrolytes in a synergetic manner.

Preparation, modification, and clinical application of porous tantalum scaffolds

Porous tantalum (Ta) implants have been developed and clinically applied as high-quality implant biomaterials in the orthopedics field because of their excellent corrosion resistance, biocompatibility, osteointegration, and bone conductivity. Porous Ta allows fine bone ingrowth and new bone formation through the inner space because of its high porosity and interconnected pore structure. It contributes to rapid bone integration and long-term stability of osseointegrated implants. Porous Ta has excellent wetting properties and high surface energy, which facilitate the adhesion, proliferation, and mineralization of osteoblasts. Moreover, porous Ta is superior to classical metallic materials in avoiding the stress shielding effect, minimizing the loss of marginal bone, and improving primary stability because of its low elastic modulus and high friction coefficient. Accordingly, the excellent biological and mechanical properties of porous Ta are primarily responsible for its rising clinical translation trend. Over the past 2 decades, advanced fabrication strategies such as emerging manufacturing technologies, surface modification techniques, and patient-oriented designs have remarkably influenced the microstructural characteristic, bioactive performance, and clinical indications of porous Ta scaffolds. The present review offers an overview of the fabrication methods, modification techniques, and orthopedic applications of porous Ta implants.

Fabrication of Porous Tantalum with Low Elastic Modulus and Tunable Pore Size for Bone Repair

Porous tantalum (Ta) is a potential bone substitute due to its excellent biocompatibility and desirable mechanical properties. In this work, a series of porous Ta materials with interconnected micropores and varying pore sizes from 23 to 210 μm were fabricated using spark plasma sintering. The porous structure was formed by thermal decomposition of ammonium bicarbonate powder premixed in the Ta powder. The pore size and porosity were controlled by the categorized particle size of ammonium bicarbonate. The porous Ta has elastic moduli in the range of 2.1-3.2 GPa and compressive yield strength in the range of 23-34 MPa, which are close to those of human bone. In vitro, as-fabricated porous Ta demonstrates excellent biocompatibility by supporting adhesion and proliferation of preosteoblasts. In vivo studies also validate its bone repair capability after implantation in a rat femur defect model. The study demonstrates a facile strategy to fabricate porous Ta with controllable pore size for bone repair.

[Physiological reactions in the interface between cementless implants and bone]

BACKGROUND

Surgical treatment of patients with osteoarthritis of the hip and persisting symptoms under conservative therapy has become increasingly important against the background of an aging population.

OBJECTIVES

What are the physiological reactions in the interface between cementless implants and bone?

METHODS

The literature is reviewed, expert opinions and animal models are analyzed and discussed.

RESULTS

Surface coating of implants with hydroxyapatite or titanium can have positive effects on osteointegration. Additional local application of mediators might be beneficial for osteointegration in the future.

CONCLUSION

Early peri-implant bone healing directly after implantation and late remodeling of the bone-implant interface are essential for secondary implant stability.

Influence of porosity on osteogenesis, bone growth and osteointegration in trabecular tantalum scaffolds fabricated by additive manufacturing

Porous tantalum implants are a class of materials commonly used in clinical practice to repair bone defects. However, the cumbersome and problematic preparation procedure have limited their widespread application. Additive manufacturing has revolutionized the design and process of orthopedic implants, but the pore architecture feature of porous tantalum scaffolds prepared from additive materials for optimal osseointegration are unclear, particularly the influence of porosity. We prepared trabecular bone-mimicking tantalum scaffolds with three different porosities (60%, 70% and 80%) using the laser powder bed fusing technique to examine and compare the effects of adhesion, proliferation and osteogenic differentiation capacity of rat mesenchymal stem cells on the scaffolds in vitro. The in vivo bone ingrowth and osseointegration effects of each scaffold were analyzed in a rat femoral bone defect model. Three porous tantalum scaffolds were successfully prepared and characterized. In vitro studies showed that scaffolds with 70% and 80% porosity had a better ability to osteogenic proliferation and differentiation than scaffolds with 60% porosity. In vivo studies further confirmed that tantalum scaffolds with the 70% and 80% porosity had a better ability for bone ingrowh than the scaffold with 60% porosity. As for osseointegration, more bone was bound to the material in the scaffold with 70% porosity, suggesting that the 3D printed trabecular tantalum scaffold with 70% porosity could be the optimal choice for subsequent implant design, which we will further confirm in a large animal preclinical model for better clinical use.

Tantalum as Trabecular Metal for Endosseous Implantable Applications

During the last 20 years, tantalum has known ever wider applications for the production of endosseous implantable devices in the orthopedic and dental fields. Its excellent performances are due to its capacity to stimulate new bone formation, thus improving implant integration and stable fixation. Tantalum's mechanical features can be mainly adjusted by controlling its porosity thanks to a number of versatile fabrication techniques, which allow obtaining an elastic modulus similar to that of bone tissue, thus limiting the stress-shielding effect. The present paper aims at reviewing the characteristics of tantalum as a solid and porous (trabecular) metal, with specific regard to biocompatibility and bioactivity. Principal fabrication methods and major applications are described. Moreover, the osteogenic features of porous tantalum are presented to testify its regenerative potential. It can be concluded that tantalum, especially as a porous metal, clearly possesses many advantageous characteristics for endosseous applications but it presently lacks the consolidated clinical experience of other metals such as titanium.

Sustained intra-articular reactive oxygen species scavenging and alleviation of osteoarthritis by biocompatible amino-modified tantalum nanoparticles

Recent studies highlight the vital role of oxidative stress and reactive oxygen species (ROS) during progression of osteoarthritis (OA). Attenuating oxidative stress and reducing reactive oxygen species generation in joints represent reasonable strategies for the treatment of osteoarthritis. To address the potential question for clinical translation, and improve the biocompatibility and long-term performance of current antioxidants, the present study provided high biocompatible small positively charged tantalum nanoparticles (Ta-NH₂ NPs) with sustained intra-articular catalase activity and first applied to osteoarthritis intervention. Our in vitro results showed that Ta-NH₂ NPs were stable with good biocompatibility, and protected viability and hyaline-like phenotype in H₂O₂-challenged chondrocytes. In addition, the in vivo biodistribution data demonstrated a sustained retention of Ta-NH₂ NPs in the joint cavity, particularly in articular cartilage without organ toxicity and abnormality in hemogram or blood biochemistry indexes. Finally, compared with catalase (CAT), Ta-NH₂ NPs exhibited long-term therapeutic effect in monosodium iodoacetate (MIA) induced osteoarthritis model. This study preliminarily explored the potential of simply modified metal nanoparticles as effective reactive oxygen species scavenging agent for osteoarthritis intervention, and offered a novel strategy to achieve sustained reactive oxygen species suppression using biocompatible Ta-based nano-medicine in oxidative stress related diseases.

Current Advances and Applications of Tantalum Element in Infected Bone Defects

Infected bone defects (IBDs) cause significant economic and psychological burdens, posing a huge challenge to clinical orthopedic surgeons. Traditional approaches for managing IBDs possess inevitable shortcomings; therefore, it is necessary to develop new functionalized scaffolds. Tantalum (Ta) has been widely used in load-bearing orthopedic implants due to its good biocompatibility and corrosion resistance. However, undecorated Ta could only structurally repair common bone defects, which failed to meet the clinical needs of bacteriostasis for IBDs. Researchers have made great efforts to functionalize Ta scaffolds to enhance their antibacterial activity through various methods, including surface coating, alloying, and micro- and nanostructure modifications. Additionally, several studies have successfully utilized Ta to modify orthopedic scaffolds for enhanced antibacterial function. These studies remarkably extended the application range of Ta. Therefore, this review systematically outlines the advances in the fundamental and clinical application of Ta in the treatment of IBDs, focusing on the antibacterial properties of Ta, its functionalization for bacteriostasis, and its applications in the modification of orthopedic scaffolds. This study provides researchers with an overview of the application of Ta in the treatment of IBDs.

Fabrication, bacteriostasis and osteointegration properties researches of the additively-manufactured porous tantalum scaffolds loading vancomycin

Infected bone defects (IBDs) remains a challenging problem for orthopedists. Clinically, routine management for IBDs has two stages: debridement and systematic antibiotics administration to control infection, and secondary grafting to repair bone defects. Whereas the efficacy is not satisfactory, because the overuse of antibiotics may lead to systemic toxicity, and the emergence of drug-resistant bacteria, as well as the secondary surgery would cause additional trauma and economic burden to the patients. Therefore, it is imperative to develop a novel scaffold for one-stage repair of IBDs. In this study, vancomycin (Van) was encapsulated into poly(lactic co-glycolic acid) (PLGA) microspheres through the double emulsion method, which were then loaded into the additively-manufactured porous tantalum (AM-Ta) through gelatin methacryloyl (GelMA) hydrogel to produce the composite Ta/GelMA hydrogel (Gel)/PLGA/vancomycin(Van) scaffolds for repairing IBDs. Physiochemical characterization of the newly-developed scaffold indicated that the releasing duration of Van was over 2 weeks. Biological experiments indicated good biocompatibility of the composite scaffold, as well as bacteriostasis and osteointegration properties, which showed great potential for clinical application. The construction of this novel scaffold would provide new sight into the development of orthopaedic implants, shedding a novel light on the treatment of IBDs.

Advances in Multifunctional Bioactive Coatings for Metallic Bone Implants

To fix the bone in orthopedics, it is almost always necessary to use implants. Metals provide the needed physical and mechanical properties for load-bearing applications. Although widely used as biomedical materials for the replacement of hard tissue, metallic implants still confront challenges, among which the foremost is their low biocompatibility. Some of them also suffer from excessive wear, low corrosion resistance, infections and shielding stress. To address these issues, various coatings have been applied to enhance their in vitro and in vivo performance. When merged with the beneficial properties of various bio-ceramic or polymer coatings remarkable bioactive, osteogenic, antibacterial, or biodegradable composite implants can be created. In this review, bioactive and high-performance coatings for metallic bone implants are systematically reviewed and their biocompatibility is discussed. Updates in coating materials and formulations for metallic implants, as well as their production routes, have been provided. The ways of improving the bioactive coating performance by incorporating bioactive moieties such as growth factors, osteogenic factors, immunomodulatory factors, antibiotics, or other drugs that are locally released in a controlled manner have also been addressed.

Strategies to improve bioactive and antibacterial properties of polyetheretherketone (PEEK) for use as orthopedic implants

Polyetheretherketone (PEEK) has gradually become the mainstream material for preparing orthopedic implants due to its similar elastic modulus to human bone, high strength, excellent wear resistance, radiolucency, and biocompatibility. Since the 1990s, PEEK has increasingly been used in orthopedics. Yet, the widespread application of PEEK is limited by its bio-inertness, hydrophobicity, and susceptibility to microbial infections. Further enhancing the osteogenic properties of PEEK-based implants remains a difficult task. This article reviews some modification methods of PEEK in the last five years, including surface modification of PEEK or incorporating materials into the PEEK matrix. For surface modification, PEEK can be modified by chemical treatment, physical treatment, or surface coating with bioactive substances. For PEEK composite material, adding bioactive filler into PEEK through the melting blending method or 3D printing technology can increase the biological activity of PEEK. In addition, some modification methods such as sulfonation treatment of PEEK or grafting antibacterial substances on PEEK can enhance the antibacterial performance of PEEK. These strategies aim to improve the bioactive and antibacterial properties of the modified PEEK. The researchers believe that these modifications could provide valuable guidance on the future design of PEEK orthopedic implants.

Tantalum and magnesium nanoparticles enhance the biomimetic properties and osteo-angiogenic effects of PCL membranes

Segmental bone defects, accompanied by periosteum stripping or injury, usually lead to delayed bone union or nonunion, which have challenged orthopedic surgeons. The periosteum, which provides essential blood supply and initial stem cells for bone tissue, plays an important role in the repair of bone defects. The reconstruction of the destroyed periosteum has attracted the attention of researchers exploring more satisfactory therapies to repair bone defects. However, periosteum-like biomaterials have yet to meet the clinical requirements and resolve this challenging problem. In this study, we manufactured a nanofiber periosteum replacement based on poly-ε-caprolactone (PCL), in which tantalum nanoparticles (TaNPs) and nanoscale magnesium oxide (MgO) were introduced to enhance its osteogenic and angiogenic ability. The results of in vitro experiments indicated that the PCL/Ta/MgO periosteum replacement, with excellent cytocompatibility, promoted the proliferation of both bone marrow mesenchymal stem cells (BMSCs) and endothelial progenitor cells (EPCs). Furthermore, the incorporation of TaNPs and nano-MgO synergistically enhanced the osteogenic differentiation of BMSCs and the angiogenic properties of EPCs. Similarly, the results of in vivo experiments from subcutaneous implantation and critical-sized calvarial defect models showed that the PCL/Ta/MgO periosteum replacement combined the osteogenesis and angiogenesis abilities, promoting vascularized bone formation to repair critical-sized calvarial defects. The results of our study suggest that the strategy of stimulating repairing bone defects can be achieved with the periosteum repaired in situ and that the proposed periosteum replacement can act as a bioactive medium to accelerate bone healing.