Aseptic loosening, not only a question of wear: a review of different theories

Feasibility of the Non-Window-Type 3D-Printed Porous Titanium Cage in Posterior Lumbar Interbody Fusion: A Randomized Controlled Multicenter Trial

BACKGROUND

Three-dimensionally printed titanium (3D-Ti) cages can be divided into 2 types: window-type cages, which have a void for bone graft, and non-window-type cages without a void. Few studies have investigated the necessity of a void for bone graft in fusion surgery. Therefore, the present study assessed the clinical and radiographic outcomes of window and non-window-type 3D-Ti cages in single-level posterior lumbar interbody fusion.

METHODS

A total of 70 patients were randomly assigned to receive either a window or non-window cage; 61 patients (87%) completed final follow-up (32 from the window cage group, 29 from the non-window cage group). Radiographic outcomes, including fusion rates, subsidence, and intra-cage osseointegration patterns, were assessed. Intra-cage osseointegration was measured using the intra-cage bridging bone score for the window cage group and the surface osseointegration ratio score for the non-window cage group. Additionally, we looked for the presence of the trabecular bone remodeling (TBR) sign on computed tomography (CT) images.

RESULTS

Of the 61 patients, 58 achieved interbody fusion, resulting in a 95.1% fusion rate. The fusion rate in the non-window cage group was comparable to, and not significantly different from, that in the window cage group (96.6% and 93.8%, p > 0.99). The subsidence rate showed no significant difference between the window and non-window cage groups (15.6% and 3.4%, respectively; p = 0.262). The intra-cage osseointegration scores showed a significant difference between the groups (p = 0.007), with the non-window cage group having a higher proportion of cases with a score of 4 compared with the window cage group. The TBR sign was observed in 87.9% of patients who achieved interbody fusion, with a higher rate in the non-window cage group across the entire cohort although the difference was not significant (89.7% versus 78.1%, p = 0.385).

CONCLUSIONS

Non-window-type 3D-Ti cages showed equivalent clinical outcomes compared with window-type cages and comparable interbody fusion rates. These results suggest that the potential advantages of 3D-Ti cages could be optimized in the absence of a void for bone graft by providing a larger contact surface for osseointegration.

LEVEL OF EVIDENCE

Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

MRI and SPECT/CT demonstrate, with low certainty of evidence, the highest diagnostic accuracy for aseptic knee arthroplasty loosening: A systematic comparative diagnostic test review and meta-analysis

PURPOSE

The purpose of this study was to evaluate and compare the diagnostic accuracy of modalities used to aid the diagnosis of aseptic knee arthroplasty loosening.

METHODS

A comparative diagnostic test accuracy systematic review and meta-analysis was conducted following the Cochrane and PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. PubMed, EMBASE and Cochrane databases were searched for original articles evaluating diagnostic modalities up to March 2024. Included studies compared the modality (index test) to the intraoperative finding as reference test. The QUADAS-C (Quality Assessment of Diagnostic Accuracy Studies-Comparative) tool was used to assess the quality of the included studies. The GRADE (Grading of Recommendations, Assessment, Development and Evaluation) approach was used to evaluate the certainty of evidence. Level of evidence was evaluated using the Oxford Levels of Evidence tool. The primary outcome was the summary of diagnostic accuracy metrics for each modality as demonstrated by a summary receiver-operating characteristic (SROC) curve.

RESULTS

The search yielded 467 articles. Of these, 14 articles were included. These 14 articles evaluated a total of five different diagnostic modalities: bone scintigraphy (three studies, 146 cases), 18-fluorodeoxyglucose positron emission tomography (two studies, 50 cases), single-photon emission computed tomography combined with computed tomography (SPECT/CT) (seven studies, 371 cases), radionuclide arthrogram (three studies, 196 cases) and magnetic resonance imaging (MRI) (one study, 116 cases). Nine studies exhibited a high risk of bias in patient selection, and all studies showed a high risk of bias related to the reference test. The majority of the included studies were classified as Level III evidence, leading to an overall low level of certainty in the evidence. The most accurate tests, as demonstrated by the SROC analysis, were MRI and SPECT/CT, with sensitivities ranging from 0.00 to 1.00 and 0.33 to 1.00 and specificities between 0.31-1.00 and 0.00-1.00, respectively.

CONCLUSIONS

This review and meta-analysis evaluated available diagnostic modalities to aid the diagnosis of knee arthroplasty loosening and based on a low certainty of evidence suggests that MRI and SPECT/CT are currently the most accurate modalities available to aid the diagnosis of aseptic loosening of knee arthroplasty components.

LEVEL OF EVIDENCE

Level III.

Surface bioactivation of Polyetheretherketone (PEEK) by magnesium chondroitin sulfate (MgCS) as orthopedic implants for reconstruction of skeletal defects

Polyether-ether-ketone (PEEK) is clinically used as a bio-implant for the healing of skeletal defects. However, the osseointegration of clinical-sized bone grafts remains limited. In this study, surface-porous PEEK was created by using a sulfonation method and a metal-polysaccharide complex MgCS was introduced on the surface of sulfonated PEEK to form MgCS@SPEEK. The as-prepared MgCS@SPEEK was found to have a porous surface with good hydrophilicity and bioactivity. This was followed by an investigation into whether MgCS loaded onto sulfonated PEEK surfaces could promote osseointegration and angiogenesis. The in vitro results showed that MgCS@SPEEK had a positive effect on reducing the expression levels of inflammatory genes and promoting osteogenesis and angiogenesis-related genes expression levels. Furthermore, porous MgCS@SPEEK was implanted in critical-sized rat tibial defects for in vivo evaluation of osseointegration. The micro-computed tomography evaluation results revealed substantial bone formation at 4 and 8 weeks. Collectively, these findings indicate that MgCS@SPEEK could provide improved osseointegration and an attractive strategy for orthopaedic applications.

Effect of cortical bone thickness on shear stress and force in orthodontic miniscrew-bone interface - A finite element analysis

Miniscrews are widely used in orthodontics as an anchorage device while aligning teeth. Shear stress in the miniscrew-bone interface is an important factor when the miniscrew makes contact with the bone. The objective of this study was to analyze the shear stress and force in the screw-bone interface for varying Cortical Bone Thickness (CBT) using Finite Element Analysis (FEA). Varying CBT of 1.09 mm (1.09CBT) and 2.66 mm (2.66CBT) with miniscrews of Ø1.2 mm, 10 mm length (T1), Ø1.2 mm, 6 mm length (T2) and Ø1.6 mm, 8 mm length (T3) were analyzed. Six Finite Element (FE) models were developed with cortical, cancellous bone, miniscrews and gingiva as a prism. A deflection of 0.1 mm was applied on the neck of the miniscrews at 0°, +30° and -30° angles. The shear stress and force in the screw-bone interface were assessed. The results showed that the CBT affects the shear stress and force in the screw-bone interface region in addition to the screw dimensions and deflection angulations. T1 screw generated lesser shear stress in 1.09CBTand 2.66CBTcompared to T2 and T3 screws. Higher CBT is preferred for better primary stability in shear aspect. Clinically applied forces of 200 gms to 300 gms to an anchorage device induces shear stress in the miniscrew-bone interface region might cause stress shielding. Thus, clinicians need to consider the effect of varying CBT and the size of the miniscrews for the stability, reduced stress shielding and better anchorage during orthodontic treatment.

Enhancement of Local Osseointegration and Implant Stability of Titanium Implant in Osteoporotic Rats by Biomimetic Multilayered Structures Containing Catalpol

This study examined the surface modification of titanium (Ti) implants to enhance early-stage osseointegration, which reduced the failure rate of internal fixation in osteoporotic fractures that inherently decrease in bone mass and strength. We employed a layer-by-layer electroassembly technique to deposit catalpol-containing hyaluronic acid/chitosan multilayers onto the surface of Ti implants. To evaluate the in vitro osteoinductive effects of catalpol-coated Ti implants, the robust osteoblast differentiation capacity of the murine preosteoblast cell line, MC3T3-E1, was employed. Furthermore, the performance of these implants was evaluated in vivo through femoral intramedullary implantation in Sprague-Dawley rats. The engineered implant effectively regulated catalpol release, promoting increased bone formation during the initial stages of implantation. The in vitro findings demonstrated that catalpol-coated Ti surfaces boosted ALP activity, cell proliferation as measured by CCK-8, and osteogenic protein expression via WB analysis, surpassing the uncoated Ti group (P < 0.05). In vivo micro-computed tomography (CT) and histological analyses revealed that catalpol-coated Ti significantly facilitated the formation and remodeling of new bone in osteoporotic rats at 14 days post-implantation. This study outlines a comprehensive and straightforward methodology for the fabrication of biofunctional Ti implants to address osteoporosis.

Printable functionally graded tibial implant for TAR: FE study comparing implant materials, FGM properties, and implant designs

Tibial implants with functionally graded material (FGM) for total ankle replacement (TAR) can provide stiffness similar to the host tibia bone. The FGM implants with low stiffness reduce stress shielding but may increase implant-bone micromotion. A trade-off between stress shielding and implant-bone micromotion is required if FGMs are to substitute traditionally used Ti and CoCr metal implants. The FGM properties such as material gradation law and volume fraction index may influence the performance of FGM implants. Along with the FGM properties, the design of FGM implants may also have a role to play. The objective of this study was to examine FGM tibial implants for TAR, by comparing implant materials, FGM properties, and implant designs. For this purpose, finite element analysis (FEA) was conducted on 3D FE models of the intact and the implanted tibia bone. The tibial implants were composed of CoCr and Ti, besides them, the FGM of Ti and HA was developed. The FGM implants were modelled using exponential, power, and sigmoid laws. Additionally, for power and sigmoid laws, different volume fraction indices were taken. The effect of implant design was observed by using keel type and stem type TAR fixation designs. The results indicated that FGM implants are better than traditional metal implants. The power law is most suitable for developing FGM implants because it reduces stress shielding. For both power law and sigmoid law, low values of the volume fraction index are preferrable. Therefore, FGM implant developed using power law with 0.1 vol fraction index is ideal with the lowest stress shielding and marginally increased implant-bone micromotion. FGM implants are more useful for keel type fixation design than stem type design. To conclude, with FGMs the major complication of stress shielding can be solved and the longevity and durability of TAR implants can be enhanced.

Chronic exposure to TiO2 micro- and nano particles: A biochemical and histopathological experimental study

The aim of this work was to analyze the effects of long-term exposure to titanium dioxide (TiO2) micro- (MPs) and nanoparticles (NPs) (six and 12 months) on the biochemical and histopathological response of target organs using a murine model. Male Wistar rats were intraperitoneally injected with a suspension of TiO2 NPs (5 nm; TiO2-NP5 group) or MPs (45 μm; TiO2-NP5 group); the control group was injected with saline solution. Six and 12 months post-injection, titanium (Ti) concentration in plasma and target organs was determined spectrometrically (ICP-MS). Blood smears and organ tissue samples were evaluated by light microscopy. Liver and kidney function was evaluated using serum biochemical parameters. Oxidative metabolism was assessed 6 months post-injection (determination of superoxide anion by nitroblue tetrazolium (NBT) test, superoxide dismutase (SOD) and catalase (CAT), lipid peroxidation, and paraoxonase 1). Titanium (Ti) concentration in target organs and plasma was significantly higher in the TiO2-exposed groups than in the control group. Histological evaluation showed the presence of titanium-based particles in the target organs, which displayed no structural alterations, and in blood monocytes. Oxidative metabolism analysis showed that TiO2 NPs were more reactive over time than MPs (p < .05) and mobilization of antioxidant enzymes and membrane damage varied among the studied organs. Clearance of TiO2 micro and nanoparticles differed among the target organs, and lung clearance was more rapid than clearance from the lungs and kidneys (p < .05). Conversely, Ti concentration in plasma increased with time (p < .05). In conclusion, neither serum biochemical parameters nor oxidative metabolism markers appear to be useful as biomarkers of tissue damage in response to TiO2 micro- and nanoparticle deposits at chronic time points.

Clinical, Radiographic, and Patient-Perceived Outcome After Radial Hemi-Wrist Arthroplasty With a New Implant: 20 Cases With 5-Year Follow-up

BACKGROUND

Distal component loosening is a common mode of failure in total wrist arthroplasty (TWA). A radial hemi-wrist arthroplasty (RHWA) has the potential to avoid problems related to the distal component in TWA. The aim of this study is to investigate clinical outcomes following surgical treatment with a new RHWA design.

METHODS

In this pilot study of 20 consecutive RHWAs, patients were assessed preoperatively and postoperatively for range of motion, grip strength, Visual Analog Scale (VAS) pain scores, and functional scoring using Patient-Rated Wrist Evaluation (PRWE), Disabilities of the Arm, Shoulder, and Hand (DASH), and Canadian Occupational Performance Measure. Radiographs were analyzed at 12 months and 5 years (mean, 5.1 years) postoperatively.

RESULTS

A total of 46 secondary surgeries were undertaken in 16 wrists, including 7 revisions. Another 6 patients are waiting for revision to radiocarpal arthrodesis. In non-revised patients, the DASH and PRWE scores improved, and wrist range of motion remained largely unchanged except for wrist flexion, which decreased. The VAS pain score during activity was reduced, and hand grip strength remained largely unchanged.

CONCLUSIONS

The new implant resulted in improved functional scoring and improved VAS pain scores in non-revised patients, but many cases needed secondary surgery due to persistent pain. The high revision rate is a major concern, and further use of the implant in its current form cannot be recommended.

Tantalum Particles Promote M2 Macrophage Polarization and Regulate Local Bone Metabolism via Macrophage-Derived Exosomes Influencing the Fates of BMSCs

In this study, the regulatory role and mechanisms of tantalum (Ta) particles in the bone tissue microenvironment are explored. Ta particle deposition occurs in both clinical samples and animal tissues following porous Ta implantation. Unlike titanium (Ti) particles promoting M1 macrophage (Mϕ) polarization, Ta particles regulating calcium signaling pathways and promoting M2 Mϕ polarization. Ta-induced M2 Mϕ enhances bone marrow-derived mesenchymal stem cells (BMSCs) proliferation, migration, and osteogenic differentiation through exosomes (Exo) by upregulating miR-378a-3p/miR-221-5p and downregulating miR-155-5p/miR-212-5p. Ta particles suppress the pro-inflammatory and bone resorption effects of Ti particles in vivo and in vitro. In a rat femoral condyle bone defect model, artificial bone loaded with Ta particles promotes endogenous Mϕ polarization toward M2 differentiation at the defect site, accelerating bone repair. In conclusion, Ta particles modulate Mϕ polarization toward M2 and influence BMSCs osteogenic capacity through Exo secreted by M2 Mϕ, providing insights for potential bone repair applications.

Bone Regeneration and Polyetheretherketone Implants in Maxillo-Facial Surgery and Neurosurgery: A Multidisciplinary Study

Polyetheretherketone (PEEK) in the last few years has emerged as an exceedingly promising material for craniofacial defects due to its biocompatibility and mechanical properties. However, its utilization remains controversial due to its inertness and low osteoinductivity. This study aimed to investigate the postoperative outcomes of patients undergoing maxillo-facial and neurosurgical procedures with PEEK implants. The focus is on evaluating bone regrowth on the surface and edges of the implant, periosteal reactions, and implant positioning. A retrospective analysis of 12 maxillo-facial surgery patients and 10 neurosurgery patients who received PEEK implants was conducted. CT scans performed at least one year post operation were examined for bone regrowth, periosteal reactions, and implant positioning. In maxillo-facial cases, the analysis included mandibular angle and fronto-orbital reconstruction, while neurosurgical cases involved cranioplasty. In maxillofacial surgery, 11 out of 12 patients showed radiological evidence of bone regrowth around PEEK implants, with favorable outcomes observed in craniofacial reconstruction. In neurosurgery, 9 out of 10 patients exhibited minimal or none bone regrowth, while one case demonstrated notable bone regeneration beneath the PEEK implant interface. The study highlights the importance of implant design and patient-specific factors in achieving successful outcomes, providing valuable insights for future implant-based procedures.

Kaempferol attenuates particle-induced osteogenic impairment by regulating ER stress via the IRE1α-XBP1s pathway

Periprosthetic osteolysis and subsequent aseptic loosening are the primary causes of failure following total joint arthroplasty. Wear particle-induced osteogenic impairment is recognized as an important contributing factor in the development of osteolysis, with endoplasmic reticulum (ER) stress emerging as a pivotal underlying mechanism. Hence, searching for potential therapeutic targets and agents capable of modulating ER stress in osteoblasts is crucial for preventing aseptic loosening. Kaempferol (KAE), a natural flavonol compound, has shown promising osteoprotective effects and anti-ER stress properties in diverse diseases. However, the influence of KAE on ER stress-mediated osteogenic impairment induced by wear particles remains unclear. In this study, we observed that KAE effectively relieved TiAl6V4 particles-induced osteolysis by improving osteogenesis in a mouse calvarial model. Furthermore, we demonstrated that KAE could attenuate ER stress-mediated apoptosis in osteoblasts exposed to TiAl6V4 particles, both in vitro and in vivo. Mechanistically, our results revealed that KAE mitigated ER stress-mediated apoptosis by upregulating the IRE1α-XBP1s pathway while concurrently partially inhibiting the IRE1α-regulated RIDD and JNK activation. Collectively, our findings suggest that KAE is a prospective therapeutic agent for treating wear particle-induced osteolysis and highlight the IRE1α-XBP1s pathway as a potential therapeutic target for preventing aseptic loosening.

The effect of a collar on primary stability of standard and undersized cementless hip stems: a biomechanical study

INTRODUCTION

Aseptic loosening and periprosthetic fractures are main reasons for revision after THA. Quite different from most other stem systems, Corail cementless hip stems show better survival rates than their cemented counterpart, which can possibly be explained by the use of a collar. The study aimed to investigate primary stability with standard and undersized hip stems both collared and collarless.

MATERIALS AND METHODS

Primary stability of cementless, collared and collarless, femoral stems was measured in artificial bones using both undersized and standard size. After preconditioning, 3D micromotion was measured under cyclic loading at the bone-implant interface.

RESULTS

The use of a collar resulted in higher micromotion within the same stem size but showed no statistically significant difference for both standard and undersized hip stems. The collared and collarless undersized stems showed no significant differences in 3D micromotion at the upper measuring positions compared to the standard stem size. Micromotion was significantly higher in the distal measuring positions, with and without collar, for the undersized stems (vs. standard collarless stem size).

CONCLUSION

The key finding is that the collarless and collared Corail hip stems, within one stem size, showed no significant differences in primary stability. Undersized stems showed significantly higher micromotion in the distal area both with and without collar.

Does the use of tibial stem extensions reduce the risk of aseptic loosening in obese patients undergoing primary total knee arthroplasty: A systematic review and meta-analysis

BACKGROUND

This study aimed to compare the risk of revision for aseptic loosening in obese (body mass index >30 kg/m2) patients with stemmed (ST) versus non-stemmed (NST) tibial implants in primary total knee arthroplasty (TKA).

METHODS

A systematic review and meta-analysis were conducted following PRISMA and MOOSE guidelines. Studies reporting a direct comparison between ST and NST tibial implants in obese patients were included. The primary outcome of interest was revision for aseptic loosening. Outcomes were analysed using meta-analysis of relative risk. Risk of bias assessment was performed using the Newcastle-Ottawa Scale for observational studies and the RoB-2 Cochrane tool for randomised studies.

RESULTS

Seven studies met the selection criteria, consisting of four cohort studies and three randomised controlled trials. Mean follow up time for the eligible cohort was 62.6 months. Meta-analysis demonstrated a statistically significant reduction in the risk of aseptic revision in the ST group compared with the NST group (risk ratio 0.25, 95% confidence interval 0.07 to 0.92). After removal of all zero-event studies, the results remained in favour of the ST group (risk ratio 0.15, 95% confidence interval 0.03 to 0.64).

CONCLUSIONS

This study found that obese patients undergoing TKA with stemmed tibial implants may have a lower risk of aseptic revision compared with those with non-stemmed tibial implants. However, due to the lack of high-quality literature available, our study is unable to draw a definitive conclusion on this matter. We suggest that this topic should be re-evaluated using higher-quality study methods, particularly national joint registries studies and randomised controlled trials.

3D-printed porous tantalum artificial bone scaffolds: fabrication, properties, and applications

Porous tantalum scaffolds offer a high degree of biocompatibility and have a low friction coefficient. In addition, their biomimetic porous structure and mechanical properties, which closely resemble human bone tissue, make them a popular area of research in the field of bone defect repair. With the rapid advancement of additive manufacturing, 3D-printed porous tantalum scaffolds have increasingly emerged in recent years, offering exceptional design flexibility, as well as facilitating the fabrication of intricate geometries and complex pore structures that similar to human anatomy. This review provides a comprehensive description of the techniques, procedures, and specific parameters involved in the 3D printing of porous tantalum scaffolds. Concurrently, the review provides a summary of the mechanical properties, osteogenesis and antibacterial properties of porous tantalum scaffolds. The use of surface modification techniques and the drug carriers can enhance the characteristics of porous tantalum scaffolds. Accordingly, the review discusses the application of these porous tantalum materials in clinical settings. Multiple studies have demonstrated that 3D-printed porous tantalum scaffolds exhibit exceptional corrosion resistance, biocompatibility, and osteogenic properties. As a result, they are considered highly suitable biomaterials for repairing bone defects. Despite the rapid development of 3D-printed porous tantalum scaffolds, they still encounter challenges and issues when used as bone defect implants in clinical applications. Ultimately, a concise overview of the primary challenges faced by 3D-printed porous tantalum scaffolds is offered, and corresponding insights to promote further exploration and advancement in this domain are presented.

A numerical investigation for the development of functionally graded Ti/HA tibial implant for total ankle replacement: Influence of material gradation law and volume fraction index

Stress shielding is one of the major concerns for total ankle replacement implants nowadays, because it is responsible for implant-induced bone resorption. The bone resorption contributes to the aseptic loosening and failure of ankle implants in later stages. To reduce the stress shielding, improvements can be made in the implant material by decreasing the elastic mismatch between the implant and the tibia bone. This study proposes a new functionally graded material (FGM) based tibial implant for minimizing the problem of stress shielding. Three-dimensional finite element (FE) models of the intact tibia and the implanted tibiae were created to study the influence of material gradation law and volume fraction index on stress shielding and implant-bone micromotion. Different implant materials were considered that is, cobalt-chromium, titanium (Ti), and FGM with Ti at the bottom and hydroxyapatite (HA) at the top. The FE models of FGM implants were generated by using different volume fractions and the rule of mixtures. The rule of mixtures was used to calculate the FGM properties based on the local volume fraction. The volume fraction was defined by using exponential, power, and sigmoid laws. For the power and sigmoid law varying volume fraction indices (0.1, 0.2, 0.5, 1, 2, and 5) were considered. The geometry resembling STAR® ankle system tibial implant was considered for the present study. The results indicate that FGMs lower stress shielding but also marginally increase implant-bone micromotion; however, the values were within the acceptable limit for bone ingrowth. It is observed that the material gradation law and volume fraction index influence the performance of FGM tibial implants. The tibial implant composed of FGM using power law with a volume fraction index of 0.1 was the preferred option because it showed the least stress shielding.

Artemisinic acid attenuates osteoclast formation and titanium particle-induced osteolysis via inhibition of RANKL-induced ROS accumulation and MAPK and NF-κB signaling pathways

Periprosthetic osteolysis (PPO) is the most common cause of joint arthroplasty failure. Its progression involves both biological and mechanical factors. Osteoclastogenesis induced by wear from debris-cell interactions, ultimately leading to excessive bone erosion, is considered the primary cause of PPO; therefore, targeting osteoclasts is a promising treatment approach. Currently available drugs have various side effects and limitations. Artemisinic acid (ArA) is a sesquiterpene isolated from the traditional herb Artemisia annua L. that has various pharmacological effects, such as antimalarial, anti-inflammatory, and antioxidant activities. Therefore, this study was aimed at investigating the effect of ArA on osteoclast formation and bone resorption function in vitro, as well as wear particle-induced osteolysis in vivo, and to explore its molecular mechanism of action. Here, we report that ArA inhibits RANKL-stimulated osteoclast formation and function. Mechanistically, ArA suppresses intracellular reactive oxygen species levels by activating the antioxidant response via nuclear factor erythroid-2-related factor 2 (Nrf2) pathway upregulation. It also inhibits the mitogen-activated kinases (MAPK) and nuclear factor-κB (NF-κB) pathways, as well as the transcription and expression of NFATc1 and c-Fos. In vivo experiments demonstrated that ArA reduces osteoclast formation and alleviates titanium particle-induced calvarial osteolysis. Collectively, our study highlights that ArA, with its osteoprotective and antioxidant effects, is a promising therapeutic agent for preventing and treating PPO and other osteoclast-mediated osteolytic diseases.

Dynamics of manual impaction instruments during total hip arthroplasty

Aims

Manual impaction, with a mallet and introducer, remains the standard method of installing cementless acetabular cups during total hip arthroplasty (THA). This study aims to quantify the accuracy and precision of manual impaction strikes during the seating of an acetabular component. This understanding aims to help improve impaction surgical techniques and inform the development of future technologies.

Methods

Posterior approach THAs were carried out on three cadavers by an expert orthopaedic surgeon. An instrumented mallet and introducer were used to insert cementless acetabular cups. The motion of the mallet, relative to the introducer, was analyzed for a total of 110 strikes split into low-, medium-, and high-effort strikes. Three parameters were extracted from these data: strike vector, strike offset, and mallet face alignment.

Results

The force vector of the mallet strike, relative to the introducer axis, was misaligned by an average of 18.1°, resulting in an average wasted strike energy of 6.1%. Furthermore, the mean strike offset was 19.8 mm from the centre of the introducer axis and the mallet face, relative to the introducer strike face, was misaligned by a mean angle of 15.2° from the introducer strike face.

Conclusion

The direction of the impact vector in manual impaction lacks both accuracy and precision. There is an opportunity to improve this through more advanced impaction instruments or surgical training.

Conformationally regulated "nanozyme-like" cerium oxide with multiple free radical scavenging activities for osteoimmunology modulation and vascularized osseointegration

Given post-operative aseptic loosening in orthopedic disease treatment, osteointegration occurs at the bone-implant interface as a holistic process, including immunoregulation (e.g., macrophage polarization), angiogenesis and osteogenesis in sequence. In order to achieve early rapid and satisfactory osseointegration, different nano-shaped (nanocone, nanopolyhedron and nanoflower abbr. NC, NP & NF) cerium oxide (CeO2-x) coatings, endowed with "nanozyme-like" activities for multiple free radical elimination and osteoimmunology regulation, were hydrothermally synthesized on titanium alloy (TC4). In vitro cell experiments showed that nano-CeO2-x coated TC4 not only induced polarization of RAW264.7 cells toward M2 phenotype, but also promoted angiogenesis and vascularization of endothelial cells along with differentiation and mineralization of osteogenic precursor cells. Improvements in M2-polarized macrophage, angiogenesis, and bone regeneration were further confirmed in a rat femoral condyle model. Among the above three nano-morphologies, NF exhibited the best osseoinetegration. RNA sequencing and mechanism exploration suggested that the inhibition of PI3K-AKT signaling pathway was essential for immunomodulatory capacity of NF. In conclusion, it provided promising insights into the immunomodulatory exploitation of orthopedic implants.

Personalized lattice-structured prosthesis as a graftless solution for mandible reconstruction and prosthetic restoration: A finite element analysis

Oral cavity tumors are a prevalent cause of mandible reconstruction surgeries. The mandible is vital for functions like oralization, respiration, mastication, and deglutition. Current mandible reconstruction methods have low success rates due to complications like plate fracture or exposure, infections, and screw loosening. Autogenous bone grafts are commonly used but carry the risk of donor region morbidity. Despite technological advances, an ideal solution for mandible reconstruction remains elusive. Additive manufacturing in medicine offers personalized prosthetics from patient-specific medical images, allowing for the creation of porous structures with tailored mechanical properties that mimic bone properties. This study compared a commercial reconstruction plate with a lattice-structured personalized prosthesis under different biting and osseointegration conditions using Finite Element Analysis. Patient-specific images were obtained from an individual who underwent mandible reconstruction with a commercial plate and suffered from plate fracture by fatigue after 26 months. Compared to the commercial plate, the maximum von Mises equivalent stress was significantly lowered for the personalized prosthesis, hindering a possible fatigue fracture. The equivalent von Mises strains found in bone were within bone maintenance and remodeling intervals. This work introduces a design that doesn't require grafts for large bone defects and allows for dental prosthesis addition without the need for implants.

Validation for the effect of intra-exposure patient motion on the assessment of radiostereometric implant migration in a tibial component phantom study

BACKGROUND

An increasing number of radiostereometry (RSA) research studies have long-term follow-up implant migration outcomes, which show ascending curves of implant migration with occasionally decreasing migration. After scrutinizing images and RSA scenes related to the alternating curves, we suppose that intra-exposure patient motion may contribute to that. The main purposes of this in vitro study were 1) to identify whether the patient motion in different directions could result in the inaccurate assessment of implant migration, and 2) to figure out which direction(s) accounted for the alternating curves.

HYPOTHESIS

It was hypothesized that the assessments of implant migration would be less precise and accurate than they could be when patient motion occurred, and such motion would contribute to the alternating curves of radiostereometric implant migration.

MATERIALS AND METHODS

A customized phantom, assembled with a tibial component, was designed for simulating intra-exposure patient motion during follow-up RSA examinations. Two different Roentgen tubes were used as the current standard of radiology departments. Radiographs were acquired in a uniplanar technical arrangement. Two defined protocols were conducted: one is to simulate implant migration outcomes at post-op, the early stage (6months), and the later stage (2 to 10years) ; during the later stage, the other is to mimic patient motion by phantom motion in the medial-lateral (x), distal-proximal (y), and anterior-posterior (z) axes.

RESULTS

Phantom motion could result in the inaccurate assessment of implant migration, and translations along the medial-lateral (x) axis were the most influenced by patient motion. Motion along the medial-lateral (x) axis could account for the curves with decreasing migration.

DISCUSSION

Our assessments of implant migration may be less precise and accurate than they could be when intra-exposure patient motion occurs. We probably neglect the importance of 100% simultaneous exposures, and the influence of patient motion on RSA accuracy and data reliability, due to the difficulty in detecting patient (micro)motion. Electronically synchronized exposures of two paired Roentgen tubes are 100% simultaneous for image acquisition, and they are thus highly recommended for the assessment of implant migration in RSA.

TYPE OF STUDY AND LEVEL OF PROOF

not applicable.

Time-elapsed microstructural imaging of failure of the reverse shoulder implant

BACKGROUND

Reverse Shoulder Arthroplasties (RSA) have become a primary choice for improving shoulder function and pain. However, the biomechanical failure mechanism of the humeral component is still unclear. The present study reports a novel protocol for microstructural imaging of the entire humerus implant under load before and after fracture.

METHODS

A humerus specimen was obtained from a 75-year-old male donor. An expert surgeon implanted the specimen with a commonly used RSA implant (Aequalis reversed II, Stryker Orthopaedics, USA) and surgical procedure. The physiological glenohumeral contact force that maximized the distal implant migration was selected from a public repository ( orthoload.com ). Imaging and concomitant mechanical testing were performed using a large-volume micro-CT scanner (Nikon XT H 225 ST) and a custom-made compressive stage. Both when intact and once implanted, the specimen was tested under a pre-load and by imposing a constant deformation causing a physiological reaction load (650 N, 10 degrees adducted). The deformation of the implanted specimen was then increased up to fracture, which was identified by a sudden drop of the reaction force, and the specimen was then re-scanned.

RESULTS

The specimen's stiffness decreased from 874 N/mm to 464 N/mm after implantation, producing movements of the bone-implant interface consistent with the implant's long-term stability reported in the literature. The micro-CT images displayed fracture of the tuberosity, caused by a combined compression and circumferential tension, induced by the distal migration of the implant.

CONCLUSION

The developed protocol offers detailed information on implant mechanics under load relative to intact conditions and fracture, providing insights into the failure mechanics of RSA implants. This protocol can be used to inform future implant design and surgical technique improvements.

Passive Biotelemetric Detection of Tibial Debonding in Wireless Battery-Free Smart Knee Implants

Aseptic loosening is the dominant failure mechanism in contemporary knee replacement surgery, but diagnostic techniques are poorly sensitive to the early stages of loosening and poorly specific in delineating aseptic cases from infections. Smart implants have been proposed as a solution, but incorporating components for sensing, powering, processing, and communication increases device cost, size, and risk; hence, minimising onboard instrumentation is desirable. In this study, two wireless, battery-free smart implants were developed that used passive biotelemetry to measure fixation at the implant-cement interface of the tibial components. The sensing system comprised of a piezoelectric transducer and coil, with the transducer affixed to the superior surface of the tibial trays of both partial (PKR) and total knee replacement (TKR) systems. Fixation was measured via pulse-echo responses elicited via a three-coil inductive link. The instrumented systems could detect loss of fixation when the implants were partially debonded (+7.1% PKA, +32.6% TKA, both p < 0.001) and fully debonded in situ (+6.3% PKA, +32.5% TKA, both p < 0.001). Measurements were robust to variations in positioning of the external reader, soft tissue, and the femoral component. With low cost and small form factor, the smart implant concept could be adopted for clinical use, particularly for generating an understanding of uncertain aseptic loosening mechanisms.

Total knee arthroplasty survivorship and outcomes in young patients: a review of the literature and 40-year update to a longitudinal study

INTRODUCTION

Growing numbers of younger patients are electing to undergo total knee arthroplasty (TKA) for end-stage osteoarthritis. The purpose of this study was to compare established literature regarding TKA outcomes in patients under age 55, to data from an ongoing longitudinal young patient cohort curated by our study group. Further, we aimed to provide a novel update on survivorship at 40 years post-TKA from our longitudinal cohort.

METHODS

A literature search was conducted using the electronic databases PubMed, Embase, and Cochrane Library, using terms related to TKA, patients under age 55, and osteoarthritis. Demographic and outcome data were extracted from all studies that met the inclusion criteria. Data were divided into the "longitudinal study (LS) group," and the "literature review (LR) group" based on the patient population of the study from which it came.

RESULTS

After screening, 10 studies met the inclusion criteria; 6 studies comprised the LR group, and 4 studies comprised the LS group. 2613 TKAs were performed among the LR group, and 114 TKAs were longitudinally followed in the LS group. The mean patient ages of the LR and LS groups were 46.1 and 51, respectively. Mean follow-up was 10.1 years for the LR group. Mean postoperative range of motion was 113.6° and 114.5° for the LR and LS groups, respectively. All-cause survivorship reported at 10 years or less ranged from 90.6% to 99.0%. The LS cohort studies reported survivorship ranges of 70.1-70.6% and 52.1-65.3% at 30 and 40 years, respectively.

CONCLUSIONS

Young TKA patients demonstrated improved functionality at each follow-up time point assessed. Survivorship decreased with increasing lengths of follow-up, ultimately ranging from 52.1-65.3% at 40 years post-TKA. The paucity of literature on long-term TKA outcomes in this patient population reinforces the necessity of further research on this topic.

Unexpected early loosening of rectangular straight femoral Zweymüller stems with an alumina-reduced surface after total hip arthroplasty-a prospective, double-blind, randomized controlled trial

BACKGROUND

Alumina particles from the grit blasting of Ti-alloy stems are suspected to contribute to aseptic loosening. An alumina-reduced stem surface was hypothesized to improve osseointegration and show comparable short-term outcomes to those of a standard stem.

METHODS

In this prospective, double-blind, randomized trial, 26 standard (STD) and 27 experimental new technology (NT) stems were implanted. The latter were additionally treated by acid etching and ice blasting to remove alumina particles from the grit-blasting process. Follow-up occurred at 12 and 24 months. Bone mineral density (BMD) around the stem was measured by a dual-energy x-ray absorptiometry device (DEXA). Radiographs were reviewed for alterations. Clinical scoring comprised the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the Harris Hip Score (HHS). Survival rates were calculated up to 50 months.

RESULTS

Lower mean BMD and more severe cortical hypertrophies were found in the NT group. At 12 months, radiolucent lines were observed mostly in the metaphyseal zone for both groups, with a progression tendency in the NT group at 24 months. At 12 months, pain scores and the WOMAC total and physical activity scores were significantly lower in the NT group, without any differences thereafter. The number of NT stem revisions amounted to 6 (24%) and 11 (41%) at 24 and 50 months, respectively.

CONCLUSION

In the NT group, unexpected catastrophic failure rates of 41% caused by early aseptic loosening were noted within 50 months. Compared with the STD stems, NT stems lead to poor clinical and radiographic results.

LEVEL OF EVIDENCE

II.

TRIAL REGISTRATION

NCT05053048.

Orthopedic meta-implants

Meta-biomaterials, engineered materials with distinctive combinations of mechanical, physical, and biological properties stemming from their micro-architecture, have emerged as a promising domain within biomedical engineering. Correspondingly, meta-implants, which serve as the device counterparts of meta-biomaterials, offer exceptional functionalities, holding great potential for addressing complex skeletal diseases. This paper presents a comprehensive overview of the various types of meta-implants, including hybrid, shape-morphing, metallic clay, and deployable meta-implants, highlighting their unprecedented properties and recent achievement in the field. This paper also delves into the potential future developments of meta-implants, addressing the exploration of multi-functionalities in meta-biomaterials and their applications in diverse biomedical fields.

Effectiveness of strontium/silver-based titanium surface coatings in improving antibacterial and osteogenic implant characteristics: a systematic review of in-vitro studies

Introduction: Due to the high incidence of implant failures, dual functionalization of titanium surfaces with antibacterial and osteogenic agents, like silver (Ag) and strontium (Sr), has gained significant attention in recent years. However, so far, the combined antibacterial and osteoinductive effectiveness of Ag/Sr-based titanium surface coatings has only been analyzed in individual studies. Methods: This systematic review aims to evaluate the existing scientific literature regarding the PICOS question "Does dual incorporation of strontium/silver enhances the osteogenic and anti-bacterial characteristics of Ti surfaces in vitro?". As a result of a web-based search adhering to the PRISMA Guidelines using three electronic databases (PubMed, Scopus, and Web of Science) until March 31, 2023, a total of 69 publications were identified as potentially relevant and 17 of which were considered appropriate for inclusion into this review. Results and Discussion: In all included publications, the use of Sr/Ag combination showed enhanced osteogenic and antibacterial effects, either alone or in combination with other agents. Moreover, the combination of Sr and Ag shows potential to synergistically enhance these effects. Nevertheless, further studies need to validate these findings under clinically more relevant conditions and evaluate the mechanism of antimicrobial and osteogenic activity of Sr/Ag combination.

Compliant Intramedullary Stems for Joint Reconstruction

The longevity of current joint replacements is limited by aseptic loosening, which is the primary cause of non-infectious failure for hip, knee, and ankle arthroplasty. Aseptic loosening is typically caused either by osteolysis from particulate wear, or by high shear stresses at the bone-implant interface from over-constraint. Our objective was to demonstrate feasibility of a compliant intramedullary stem that eliminates over-constraint without generating particulate wear. The compliant stem is built around a compliant mechanism that permits rotation about a single axis. We first established several models to understand the relationship between mechanism geometry and implant performance under a given angular displacement and compressive load. We then used a neural network to identify a design space of geometries that would support an expected 100-year fatigue life inside the body. We additively manufactured one representative mechanism for each of three anatomic locations, and evaluated these prototypes on a KR-210 robot. The neural network predicts maximum stress and torsional stiffness with 2.69% and 4.08% error respectively, relative to finite element analysis data. We identified feasible design spaces for all three of the anatomic locations. Simulated peak stresses for the three stem prototypes were below the fatigue limit. Benchtop performance of all three prototypes was within design specifications. Our results demonstrate the feasibility of designing patient- and joint-specific compliant stems that address the root causes of aseptic loosening. Guided by these results, we expect the use of compliant intramedullary stems in joint reconstruction technology to increase implant lifetime.

[The third-generation modern cementing technique in hip and knee arthroplasty]

BACKGROUND

Implant loosening is the most common reason for revision surgery.

OBJECTIVES

Contribution of modern cementing technique to the long-term stability of an implant.

METHODS

Evaluation of the available evidence on modern cementing technique.

RESULTS

Modern cementing technique in hip arthroplasty is considered established and leads to better cementing results. In knee arthroplasty, there are also specific recommendations, including intensive cleaning of the bone bed, mixing of bone cement under vacuum and application of bone cement to the implant and the bone.

CONCLUSIONS

The use of modern cementing technique in hip and knee arthroplasty facilitates cementing, increases safety, and minimizes the risk of mechanical loosening.

Fostering Excellence in Knee Arthroplasty: Developing Optimal Patient Care Pathways and Inspiring Knowledge Transfer of Advanced Surgical Techniques

Osteoarthritis of the knee is common. Early sports trauma or cartilage defects are risk factors for osteoarthritis. If conservative treatment fails, partial or total joint replacement is often performed. A joint replacement aims to restore physiological biomechanics and the quality of life of affected patients. Total knee arthroplasty is one of the most performed surgeries in musculoskeletal medicine. Several developments have taken place over the last decades that have truly altered the way we look at knee arthroplasty today. Some of the fascinating aspects will be presented and discussed in the present narrative review.

The Impact of Al2O3 Particles from Grit-Blasted Ti6Al7Nb (Alloy) Implant Surfaces on Biocompatibility, Aseptic Loosening, and Infection

For the improvement of surface roughness, titanium joint arthroplasty (TJA) components are grit-blasted with Al2O3 (corundum) particles during manufacturing. There is an acute concern, particularly with uncemented implants, about polymeric, metallic, and corundum debris generation and accumulation in TJA, and its association with osteolysis and implant loosening. The surface morphology, chemistry, phase analysis, and surface chemistry of retrieved and new Al2O3 grit-blasted titanium alloy were determined with scanning electron microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and confocal laser fluorescence microscopy, respectively. Peri-prosthetic soft tissue was studied with histopathology. Blasted retrieved and new stems were exposed to human mesenchymal stromal stem cells (BMSCs) for 7 days to test biocompatibility and cytotoxicity. We found metallic particles in the peri-prosthetic soft tissue. Ti6Al7Nb with the residual Al2O3 particles exhibited a low cytotoxic effect while polished titanium and ceramic disks exhibited no cytotoxic effect. None of the tested materials caused cell death or even a zone of inhibition. Our results indicate a possible biological effect of the blasting debris; however, we found no significant toxicity with these materials. Further studies on the optimal size and properties of the blasting particles are indicated for minimizing their adverse biological effects.

The First Stage of Knee Revision Arthroplasty in Periprosthetic Infection with Replacement of a Large Defect Double Cementing Method: A Case Report

Aim

Large bone defects in patients with chronic deep periprosthetic knee infection is a major problem. It is widely accepted that bone defects filling with polymethylmethacrylate (PMMA) cement could be used only in selected cases of small bone defects (up to 5 mm) and less than 50% of articular surface due to multiple reasons: risk of thermal bone damage, inadequate cement pressurization and bone cement shrinkage, etc. Staged cementing for preventing bone heating and over negative effects of cementing on a thick layer of bone cement has limited support in the literature.

Case Presentation

We present the case of 4.5 years follow up after temporary-permanent spacer implantation in a 63-year-old male with chronic deep knee PJI and tibial AORI type 3 bone defect reconstructed via double cementing method.

Results

Method of double (staged) cementing used for reconstruction of epiphyseal tibial bone defect in a patient with fistula form of knee PJI shows excellent clinical results at 4.5 years follow up.

The role of the depth of resection of the distal tibia on biomechanical performance of the tibial component for TAR: A finite element analysis with three implant designs

The depth of resection of the tibia bone in total ankle replacement (TAR) may influence implant-bone micromotion and stress shielding. High implant-bone micromotion and stress-shielding lead to aseptic loosening of the tibial component for TAR. The aim was to improve the outcomes of the different designs of TAR (STAR, Mobility, and Salto) with the variation of the depth of resection of the distal tibia bone. Finite element (FE) models of the implanted tibia with the depth of resection varying from 6 mm to 16 mm and of the intact tibia was prepared. The value of micromotion increased as the depth of resection increased. The micromotion increased in the proximal anterior-posterior portion of the pegs for STAR, the posterior part of the stem for Mobility, and the proximal lateral portion of the keel for Salto with the increase in the depth of resection. Whereas, the stresses (von Mises) decreased in some regions and increased in some regions depending upon the implant design. But overall stresses decreased in the tibia bone. Furthermore, the mean stress shielding increased in all the designs as the depth of resection increased. This in silico study indicated that the depth of resection should be given more importance during TAR surgery. The ideal depth of resection should be minimum i.e., 6 mm based on this FE study.

Influence of stem design parameters on periprosthetic femoral fractures examined by subject specific finite element analyses

Due to the increasing number of periprosthetic femoral fractures (PFF), the optimisation of implant design gains importance. For the presented research a validated, subject specific finite element model of a human femur with an inlying total hip stem was used to compare the influence of different geometrical implant parameters on the development of PFF. The heterogeneous bone tissue was modelled on the basis of computed tomography scans. A ductile damage model with element deletion was applied to simulate bone fracture in a load case re-enacting a stumbling scenario. The results were compared in terms of fracture load, subsidence and fracture pattern to analyse the influence of friction at the implant-bone interface, implant size and stem length. The results showed that higher friction coefficients lead to an increase of fracture load. Also, the usage of an oversized implant has a negligible effect while an undersized implant reduces the fracture load by 48.9% for the investigated femur. Lastly, a higher fracture load was reached with an elongated stem, but the bending and change in fracture path indicate a more distal force transmission and subsequent stress shielding in the proximal femur.

Advanced surface engineering of titanium materials for biomedical applications: From static modification to dynamic responsive regulation

Titanium (Ti) and its alloys have been widely used as orthopedic implants, because of their favorable mechanical properties, corrosion resistance and biocompatibility. Despite their significant success in various clinical applications, the probability of failure, degradation and revision is undesirably high, especially for the patients with low bone density, insufficient quantity of bone or osteoporosis, which renders the studies on surface modification of Ti still active to further improve clinical results. It is discerned that surface physicochemical properties directly influence and even control the dynamic interaction that subsequently determines the success or rejection of orthopedic implants. Therefore, it is crucial to endow bulk materials with specific surface properties of high bioactivity that can be performed by surface modification to realize the osseointegration. This article first reviews surface characteristics of Ti materials and various conventional surface modification techniques involving mechanical, physical and chemical treatments based on the formation mechanism of the modified coatings. Such conventional methods are able to improve bioactivity of Ti implants, but the surfaces with static state cannot respond to the dynamic biological cascades from the living cells and tissues. Hence, beyond traditional static design, dynamic responsive avenues are then emerging. The dynamic stimuli sources for surface functionalization can originate from environmental triggers or physiological triggers. In short, this review surveys recent developments in the surface engineering of Ti materials, with a specific emphasis on advances in static to dynamic functionality, which provides perspectives for improving bioactivity and biocompatibility of Ti implants.

Carbon-fibre plates for traumatic and (impending) pathological fracture fixation: Where do we stand? A systematic review

BACKGROUND

Carbon-fibre (CF) plates are increasingly used for fracture fixation. This systematic review evaluated complications associated with CF plate fixation. It also compared outcomes of patients treated with CF plates versus metal plates, aiming to determine if CF plates offered comparable results. The study hypothesized that CF plates display similar complication rates and clinical outcomes as metal plates for fracture fixation.

METHODS

The study adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The following databases were searched from database inception until June 2023: PubMed, MEDLINE, Embase, Web of Science, Cochrane Library, Emcare, Academic Search Premier and Google Scholar. Studies reporting on clinical and radiological outcomes of patients treated with CF plates for traumatic fractures and (impending) pathological fractures were included. Study quality was assessed, and complications were documented as number and percentage per anatomic region.

RESULTS

A total of 27 studies of moderate to very low quality of evidence were included. Of these, 22 studies (800 patients, median follow-up 12 months) focused on traumatic fractures, and 5 studies (102 patients, median follow-up 12 months) on (impending) pathological fractures. A total of 11 studies (497 patients, median follow-up 16 months) compared CF plates with metal plates. Regarding traumatic fractures, the following complications were mostly reported: soft tissue complications (52 out of 391; 13%) for the humerus, structural complications (6 out of 291; 2%) for the distal radius, nonunion and structural complication (1 out of 34; 3%) for the femur, and infection (4 out of 104; 4%) for the ankle. For (impending) pathological fractures, the most frequently reported complications were infections (2 out of 14; 14%) for the humerus and structural complication (6 out of 86; 7%) for the femur/tibia. Comparative studies reported mixed results, although the majority (7 out of 11; 64%) reported no significant differences in clinical or radiological outcomes between patients treated with CF or metal plates.

CONCLUSION

This systematic review did not reveal a concerning number of complications related to CF plate fixation. Comparative studies showed no significant differences between CF plates and metal plates for traumatic fracture fixation. Therefore, CF plates appear to be a viable alternative to metal plates. However, high-quality randomized controlled trials (RCTs) with long-term follow-up are strongly recommended to provide additional evidence supporting the use of CF plates.

LEVEL OF EVIDENCE

III, systematic review.

Magnesium implant degradation provides immunomodulatory and proangiogenic effects and attenuates peri-implant fibrosis in soft tissues

Implants made of magnesium (Mg) are increasingly employed in patients to achieve osteosynthesis while degrading in situ. Since Mg implants and Mg²⁺ have been suggested to possess anti-inflammatory properties, the clinically observed soft tissue inflammation around Mg implants is enigmatic. Here, using a rat soft tissue model and a 1-28 d observation period, we determined the temporo-spatial cell distribution and behavior in relation to sequential changes of pure Mg implant surface properties and Mg²⁺ release. Compared to nondegradable titanium (Ti) implants, Mg degradation exacerbated initial inflammation. Release of Mg degradation products at the tissue-implant interface, culminating at 3 d, actively initiated chemotaxis and upregulated mRNA and protein immunomodulatory markers, particularly inducible nitric oxide synthase and toll-like receptor-4 up to 6 d, yet without a cytotoxic effect. Increased vascularization was demonstrated morphologically, preceded by high expression of vascular endothelial growth factor. The transition to appropriate tissue repair coincided with implant surface enrichment of Ca and P and reduced peri-implant Mg²⁺ concentration. Mg implants revealed a thinner fibrous encapsulation compared with Ti. The detailed understanding of the relationship between Mg material properties and the spatial and time-resolved cellular processes provides a basis for the interpretation of clinical observations and future tailoring of Mg implants.

An experimental study on the impact of prosthesis temperature on the biomechanical properties of bone cement fixation

PURPOSE

To investigate the effect of the femoral component and tibial plateau component temperature on the strength of cement fixation during total knee arthroplasty (TKA).

METHODS

Femoral prosthesis, tibial plateau prosthesis, and polypropylene mold base were used to simulate TKA for bone cement fixation. Pre-cooling or pre-warming of femoral and tibial plateau components at different temperatures (4 °C, 15 °C, 25 °C, 37 °C, 45 °C), followed by mixing and stirring of bone cement at laboratory room temperature (22 °C), were performed during research. The prosthesis and the base adhered together, and the bone cement was solidified for 24 h at a constant temperature of 37 °C to verify the hardness of the bone cement with a push-out test.

RESULTS

The push-out force of the femoral prosthesis after fixation was higher than that of the tibial plateau prosthesis, and with the increase of the prosthesis temperature, the push-out force after fixation of the bone cement also increased linearly and the porosity of the prosthetic cement in the tibia and femur decreased as the temperature increased.

CONCLUSION

Without changing the mixing temperature and solidification temperature, the fixation strength of the femoral prosthesis is higher than that of the tibial plateau prosthesis. Properly increasing the temperature of the prosthesis can increase the push-out force of the fixation strength.

TiNbSn stems with gradient changes of Young's modulus and stiffness reduce stress shielding compared to the standard fit-and-fill stems

BACKGROUND

The difference between Young's moduli of the femur and the stem causes stress shielding (SS). TiNbSn (TNS) stem has a low Young's modulus and strength with gradient functional properties during the change in elastic modulus with heat treatment. The aim of this study was to investigate the inhibitory effect of TNS stems on SS and their clinical outcomes compared to conventional stems.

METHODS

This study was a clinical trial. Primary THA was performed using a TNS stem from April 2016 to September 2017 for patients in the TNS group. Unilateral THA was performed using a Ti6Al4V alloy stem from January 2007 to February 2011 for patients in the control group. The TNS and Ti6Al4V stems were matched in shape. Radiographs were obtained at the 1- and 3-year follow-ups. Two surgeons independently checked the SS grade and appearance of cortical hypertrophy (CH). The Japanese Orthopaedic Association (JOA) scores before and 1 year after surgery were assessed as clinical scores.

RESULTS

None of the patients in the TNS group had grade 3 or 4 SS. In contrast, in the control group, 24% and 40% of patients had grade 3 and 4 SS at the 1- and 3-year follow-ups, respectively. The SS grade was lower in the TNS group than in the control group at the 1- and 3-year follow-ups (p < 0.001). The frequencies of CH in both groups were no significant difference at the 1- and 3-year follow-ups. The JOA scores of the TNS group significantly improved at 1 year after surgery and were comparable to control group.

CONCLUSION

The TNS stem reduced SS at 1 and 3 years after THA compared to the proximal-engaging cementless stem, although the shapes of the stems matched. The TNS stem could reduce SS, stem loosening, and periprosthetic fractures.

TRIAL REGISTRATION

Current Controlled Trials. ISRCTN21241251. https://www.isrctn.com/search?q=21241251 . The date of registration was October 26, 2021. Retrospectively registered.

Mechanical complications after total knee arthroplasty

INTRODUCTION

With the increasing demand for total knee arthroplasty (TKA) and the burden of revision TKA on the healthcare system, as well as the quality of life implications for patients, it is extremely important for surgeons to be able to anticipate and prevent TKA mechanical complications. Surgeons must be familiar with the different causes and mechanisms of TKA complications so that they can properly treat patients with failed TKAs and better avoid these complications.

AREAS COVERED

This review addresses TKA mechanical complications and provides context for the topic. A detailed review of surgical factors, implant factors, and patient factors that contribute to mechanical complications after TKA is provided. All of the literature cited in this review was gathered from the PubMed online database using different keywords based on the section of the manuscript.

EXPERT OPINION

As surgeons and engineers solve certain issues in TKA, new challenges will inevitably arise. We must continue to push forward and innovate from both a surgical technique and implant design perspective.

Aseptic loosening of tumor prostheses in distal femur after revision surgery: a retrospective study

BACKGROUND

Tumor prostheses of the distal femur after revision surgery is associated with high rates of aseptic loosening, which has introduced great challenges to the survival of patients, but only a few studies have evaluated their X-ray imaging. The purpose of this study was to analyze the risk factors for recurrence of aseptic loosening and make recommendations to reduce the incidence of aseptic loosening after revision surgery of tumor prostheses in the distal femur.

METHOD

A retrospective analysis was performed on 23 patients who had revision surgery for distal femur prostheses due to aseptic loosening between June 2002 and June 2021. They were divided into two groups based on the condition of the prostheses after revision surgery: loosening group (9 patients) and control group (14 patients). Following the initial replacement, the length and diameter of the prosthetic intramedullary stem were measured through the standard full-length anteroposterior X-ray imaging of both lower limbs. The osteotomy length, femoral length and diameter, femoral intramedullary stem diameter, hip-knee-ankle angle (HKAA), mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA), and so on were measured as well. Following that, statistical analysis was performed.

RESULTS

Patients in the loosening group had statistically significant differences in the ratio of prostheses length to femur length (71.89 ± 6.62) and the ratio of intramedullary stem diameter to femoral diameter (25.50 ± 6.90) (P < 0.05), when compared to the control group. The HKAA (175.58 ± 2.78), mLDFA (94.42 ± 2.57), and the deviation angle between the lower limb alignment and the tibial prostheses force line (2.23 ± 1.09) in the loosening group were significantly different from those in the control group (P < 0.05) on postoperative radiographs of the entire length of the lower limbs. The lowest score in intramedullary manubrium I indicated less osteolysis, while the highest score in intramedullary manubrium III indicated the most serious osteolysis, and the difference was statistically significant (P < 0.05).

CONCLUSIONS

Our study suggests that the use of longer and thicker intramedullary stems can effectively decrease the occurrence of aseptic loosening. Additionally, it is important to avoid using the original prostheses and reconstruct the standard line of lower limb force to further reduce the incidence of aseptic loosening. It is crucial to closely monitor the distal segment of the intramedullary stem for osteolysis after surgery.

Subject-specific tribo-contact conditions in total knee replacements: a simulation framework across scales

Fundamental knowledge about in vivo kinematics and contact conditions at the articulating interfaces of total knee replacements are essential for predicting and optimizing their behavior and durability. However, the prevailing motions and contact stresses in total knee replacements cannot be precisely determined using conventional in vivo measurement methods. In silico modeling, in turn, allows for a prediction of the loads, velocities, deformations, stress, and lubrication conditions across the scales during gait. Within the scope of this paper, we therefore combine musculoskeletal modeling with tribo-contact modeling. In the first step, we compute contact forces and sliding velocities by means of inverse dynamics approach and force-dependent kinematic solver based upon experimental gait data, revealing contact forces during healthy/physiological gait of young subjects. In a second step, the derived data are employed as input data for an elastohydrodynamic model based upon the finite element method full-system approach taking into account elastic deformation, the synovial fluid's hydrodynamics as well as mixed lubrication to predict and discuss the subject-specific pressure and lubrication conditions.

Dual-Action Effect of Gallium and Silver Providing Osseointegration and Antibacterial Properties to Calcium Titanate Coatings on Porous Titanium Implants

Previously, functional coatings on 3D-printed titanium implants were developed to improve their biointegration by separately incorporating Ga and Ag on the biomaterial surface. Now, a thermochemical treatment modification is proposed to study the effect of their simultaneous incorporation. Different concentrations of AgNO₃ and Ga(NO₃)₃ are evaluated, and the obtained surfaces are completely characterized. Ion release, cytotoxicity, and bioactivity studies complement the characterization. The provided antibacterial effect of the surfaces is analyzed, and cell response is assessed by the study of SaOS-2 cell adhesion, proliferation, and differentiation. The Ti surface doping is confirmed by the formation of Ga-containing Ca titanates and nanoparticles of metallic Ag within the titanate coating. The surfaces generated with all combinations of AgNO₃ and Ga(NO₃)₃ concentrations show bioactivity. The bacterial assay confirms a strong bactericidal impact achieved by the effect of both Ga and Ag present on the surface, especially for Pseudomonas aeruginosa, one of the main pathogens involved in orthopedic implant failures. SaOS-2 cells adhere and proliferate on the Ga/Ag-doped Ti surfaces, and the presence of gallium favors cell differentiation. The dual effect of both metallic agents doping the titanium surface provides bioactivity while protecting the biomaterial from the most frequent pathogens in implantology.

A combined FE-hybrid MCDM framework for improving the performance of the conical stem tibial design for TAR with the addition of pegs

BACKGROUND AND OBJECTIVES

The conical stemmed design of the tibial component for total ankle replacement (TAR) (example Mobility design) uses a single intramedullary stem for primary fixation. Tibial component loosening is a common mode of failure for TAR. Primary causes of loosening are lack of bone ingrowth due to excessive micromotion at the implant-bone interface and bone resorption due to stress shielding after implantation. The fixation feature of the conical stemmed design can be modified with the addition of small pegs to avoid loosening. The aim of the study is to select the improved design for conical stemmed TAR using a combined Finite Element (FE) hybrid Multi-Criteria Decision-Making (MCDM) framework.

METHODS

The geometry and material properties of the bone for FE modeling were extracted from the CT data. Thirty-two design alternatives with varying pegs in number (one, two, four, eight), location (anterior, posterior, medial, lateral, anterior-posterior, medial-lateral, equally spaced), and height (5 mm, 4 mm, 3 mm, 2 mm) were prepared. All models were analyzed for dorsiflexion, neutral, and plantarflexion loading. The proximal part of the tibia was fixed. The implant-bone interface coefficient of friction was taken as 0.5. The implant-bone micromotion, stress shielding, volume of bone resection, and surgical simplicity were the important criteria considered for evaluating the performance of TAR. The designs were compared using a hybrid MCDM method of WASPAS, TOPSIS, EDAS, and VIKOR. The weight calculations were based on fuzzy AHP and the final ranks on the Degree of Membership method.

RESULTS

The addition of pegs decreased the mean implant-bone micromotions and increased stress shielding. There was a marginal decrease in micromotion and a marginal increase in stress shielding when the peg heights were increased. The results of hybrid MCDM indicated that the most preferable alternative designs were two pegs of 4 mm height in the AP direction to the main stem, two pegs of 4 mm height in the ML direction, and one peg of 3 mm height in the A direction.

CONCLUSIONS

Outcomes of this study suggest that the addition of pegs can reduce the implant-bone micromotions. Modified three designs would be useful by considering implant-bone micromotions, stress shielding, volume of bone resection, and surgical simplicity.

A dual-functional PEEK implant coating for anti-bacterial and accelerated osseointegration

Polyetheretherketone (PEEK) has been widely applied in biomedical engineering. However, the unsatisfactory bioactivity essentially limits the clinical application of PEEK. In this study, a simply immersing method was proposed to fabricate a dual-functional PEEK with antibacterial properties and enhanced bone integration. Firstly, the surface of PEEK was modified with a polydopamine (PDA) coating by incubating at dopamine solution. Afterward, the PEEK-PDA was modified with manganese (Mn) and silver (Ag) ions by the soaking method to fabricate the PEEK-PDA-Mn/Ag. The physicochemical capabilities of PEEK-PDA-Mn/Ag were further explored in the ions release, wettability, morphology, and element distributions. PEEK-PDA-Mn/Ag obviously accelerated the adhesion and distribution of MC3T3-E1 cells, indicating favorable biosafety in vitro. Meanwhile, the osteogenic properties of PEEK-PDA-Mn and PEEK-PDA-Mn/Ag were proved by the increased expression of osteogenic genes, alkaline phosphatase (ALP), and mineralization in vitro. Additionally, the wide antibacterial capabilities of PEEK-PDA-Mn/Ag were proved in both Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in vitro. Furthermore, the PEEK-PDA-Mn/Ag was antibacterial with capability in enhancing osseointegration in vivo. Overall, the simply immersing method can modify the surface of PEEK, giving the bioactivity, biocompatibility, and antibacterial ability to the composited PEEK, which could be applied as an orthopedic implant in clinical.

Targeted therapy for peri-prosthetic osteolysis using macrophage membrane-encapsulated human urine-derived stem cell extracellular vesicles

Aseptic loosening of the prosthesis is a severe complication after joint replacement. It is of great practical significance and social value to discover the prevention and treatment strategies for this condition. Exosomes from urine-derived stem cells (Exos) have great potential in promoting bone repair, reconstruction, and regulating bone metabolism. However, they are easily eliminated by macrophages and incapable of targeting the osteolysis zone. In this study, based on macrophage "homing" into periprosthetic osteolysis region and cell membrane encapsulating nanotechnology, exosomes from urine-derived stem cells were encapsulated with macrophage membrane (MM) to prevent periprosthetic osteolysis. We found that macrophage membrane encapsulated urine-derived stem cell-derived exosomes (MM-Exos) can be targeted delivery to the osteolysis zone and enhance the therapeutic effectiveness of Exos, which alleviated wear particles-induced calvarial osteolysis. Furthermore, MM-Exos could provide immunological camouflage and allow the Exos to avoid phagocytosis by macrophages and stimulate cellular uptake by bone marrow-derived stem cells (BMSCs). Therefore, we demonstrated the unique ability of the macrophage membrane as a targeted transport of exosomes from urine-derived stem cells for the prevention and treatment of periprosthetic osteolysis. These biomimetic nanoparticles provided a new therapeutic exosome delivery system for preventing wear particles-induced osteolysis. STATEMENT OF SIGNIFICANCE: Macrophage membrane encapsulated urine-derived stem cell-derived exosomes (MM-Exos) can be targeted delivery to the osteolysis zone and enhance the therapeutic effect of Exos on peri‑prosthetic osteolysis prevention. MM-Exos could allow the Exos to avoid phagocytosis by macrophages and promote the uptake of Exos by BMSCs.

The histological assessment of new bone formation with zolendronic acid loaded bone allograft in rabbit femoral bone defect

The aim of this experimental study was to evaluate the effect of zolendronic acid (ZOL) combined with bone allograft prepared using the Marburg Bone Bank System on bone formation in the implant remodeling zone. Femoral bone defects with a diameter of 5 mm and a depth of 10 mm were created in 32 rabbits. Animals were divided into 2 similar groups: Group 1 (control), where defects were filled with bone allograft, and Group 2, where allograft was combined with ZOL. Eight animals from each group were sacrificed at 14- and 60-days post-surgery and bone defect healing was assessed using histopathological and histomorphometric analyses after 14 and 60 days. The results showed that new bone formation within the bone allograft was significantly greater in the control group than in the ZOL-treated group after 14 and 60 days (p<0.05). In conclusion, local co-administration of ZOL on heat-treated allograft inhibits allograft resorption and new bone formation in the bone defect.

Zirconia-Toughened Alumina Ceramic Wear Particles Do Not Elicit Inflammatory Responses in Human Macrophages

Ten percent of patients undergoing total hip arthroplasty (THA) require revision surgery. One of the reasons for THA are wear particles released from the implants that can activate the immune defense and cause osteolysis and failure of the joint implant. The discrepancies between reports on toxicity and immunogenicity of the implant materials led us to this study in which we compared toxicity and immunogenicity of well-defined nanoparticles from Al2O3, zirconia-toughened alumina (ZTA), and cobalt chrome (CoCr), a human THP-1 macrophage cell line, human PBMCs, and therefrom-derived primary macrophages. None of the tested materials decreased the viability of THP-1 macrophages nor human primary macrophages at the 24 h time point, indicating that at concentrations from 0.05 to 50 µm3/cell the tested materials are non-toxic. Forty-eight hours of treatment of THP-1 macrophages with 5 µm3/cell of CoCr and Al2O3 caused 8.3-fold and 4.6-fold increases in TNF-α excretion, respectively, which was not observed for ZTA. The comparison between THP-1 macrophages and human primary macrophages revealed that THP-1 macrophages show higher activation of cytokine expression in the presence of CoCr and Al2O3 particles than primary macrophages. Our results indicate that ZTA is a non-toxic implant material with no immunogenic effects in vitro.

Macrophages in aseptic loosening: Characteristics, functions, and mechanisms

Aseptic loosening (AL) is the most common complication of total joint arthroplasty (TJA). Both local inflammatory response and subsequent osteolysis around the prosthesis are the fundamental causes of disease pathology. As the earliest change of cell behavior, polarizations of macrophages play an essential role in the pathogenesis of AL, including regulating inflammatory responses and related pathological bone remodeling. The direction of macrophage polarization is closely dependent on the microenvironment of the periprosthetic tissue. When the classically activated macrophages (M1) are characterized by the augmented ability to produce proinflammatory cytokines, the primary functions of alternatively activated macrophages (M2) are related to inflammatory relief and tissue repair. Yet, both M1 macrophages and M2 macrophages are involved in the occurrence and development of AL, and a comprehensive understanding of polarized behaviors and inducing factors would help in identifying specific therapies. In recent years, studies have witnessed novel discoveries regarding the role of macrophages in AL pathology, the shifts between polarized phenotype during disease progression, as well as local mediators and signaling pathways responsible for regulations in macrophages and subsequent osteoclasts (OCs). In this review, we summarize recent progress on macrophage polarization and related mechanisms during the development of AL and discuss new findings and concepts in the context of existing work.

Patient-specific femoral implant design using metamaterials for improving load transfer at proximal-lateral region of the femur

Loading configuration of hip joint creates resultant bending effect on femoral implants. So, the lateral side of femoral implant which is under tension retracts from peri‑implant bone due to positive Poisson's ratio. This retraction of implant leads to load shielding and gap opening in proximal-lateral region, thereby allowing entry of wear particle to implant-bone interface. Retraction of femoral implant can be avoided by introducing auxetic metamaterial to the retracting side. This allows the implant to push peri‑implant bone under tensile condition by virtue of their auxetic (negative Poisson's ratio) nature. To develop such implants, a patient-specific conventional solid implant was first designed based on computed-tomography scan of a patient's femur. Two types of metamaterials (2D: type-1) and (3D: type-2) were employed to design femoral meta-implants. Type-1 and type-2 meta-implants were fabricated using metallic 3D printing method and mechanical compression testing was conducted. Three finite element (FE) models of the femur implanted with solid implant, type-1 meta-implant and type-2 meta-implant were developed and analysed under compression loading. Significant correlation (R² = 0.9821 and R² = 0.9977) was found between the experimental and FE predicted strains of the two meta-implants. In proximal-lateral region of the femur, an increase of 7.1% and 44.1% von-Mises strain was observed when implanted with type-1 and type-2 meta-implant over the solid implant. In this region, bone remodelling analysis revealed 2.5% bone resorption in case of solid implant. While bone apposition of 0.5% and 7.7% was observed in case of type-1 and type-2 meta-implants, respectively. The results of this study indicates that concept of introduction of metamaterial to the lateral side of femoral implant can prove to provide higher osseointegration-friendly environment in the proximal-lateral region of femur.

Mechanical properties and biocompatibility of a novel miniscrew made of Zr70Ni16Cu6Al8 bulk metallic glass for orthodontic anchorage

The purpose of the present study was to fabricate a miniscrew possible for clinical application using Zr₇₀Ni₁₆Cu₆Al₈ bulk metallic glass (BMG), which has high mechanical strength, low elastic modulus, and high biocompatibility. First, the elastic moduli of Zr-based metallic glass rods made of Zr₅₅Ni₅Cu₃₀Al₁₀, Zr₆₀Ni₁₀Cu₂₀Al₁₀, Zr₆₅Ni₁₀Cu_17.5Al_7.5, Zr₆₈Ni₁₂Cu₁₂Al₈, and Zr₇₀Ni₁₆Cu₆Al₈ were measured. Zr₇₀Ni₁₆Cu₆Al₈ had the lowest elastic modulus among them. Then, we fabricated Zr₇₀Ni₁₆Cu₆Al₈ BMG miniscrews with diameters from 0.9 to 1.3 mm, conducted a torsion test, and implanted them into the alveolar bone of beagle dogs to compare insertion torque, removal torque, Periotest, new bone formation around the miniscrew, and failure rate compared with 1.3 mm diameter Ti-6Al-4 V miniscrew. The Zr₇₀Ni₁₆Cu₆Al₈ BMG miniscrew exhibited a high torsion torque even if the miniscrew had a small diameter. Zr₇₀Ni₁₆Cu₆Al₈ BMG miniscrews with a diameter of 1.1 mm or less had higher stability and lower failure rate than 1.3 mm diameter Ti-6Al-4 V miniscrews. Furthermore, the smaller diameter Zr₇₀Ni₁₆Cu₆Al₈ BMG miniscrew was shown, for the first time, to have a higher success rate and to form more new bone around the miniscrew. These findings suggested the usefulness of our novel small miniscrew made of Zr₇₀Ni₁₆Cu₆Al₈ BMG for orthodontic anchorage.