Long-term Osseointegration Research Articles

The Effects of Ultrasonic Scaling and Air-Abrasive Powders on the Topography of Implant Surfaces: Scanning Electron Analysis and In Vitro Study.

This in vitro study aimed to investigate the impact of bicarbonate air-abrasive powders and ultrasonic scaling with stainless steel tips on the micro- and nanotopography and roughness of three different implant-abutment junction titanium surfaces. Three types of sterile and decontaminated titanium surfaces (RS, UTM, XA) were used for analysis. Nine disks per surface type were subjected to micro- and nanotopography analysis, scanning electron microscopy (SEM), roughness analysis, and fibroblast cultivation. Ultrasonic debridement and air polishing were performed on the surfaces. Human dermal fibroblasts were cultured on the surfaces for 5 days. Data analysis adhered to ISO 25178 standards for surface texture assessment. SEM micrographs were used to reconstruct areas for extracting roughness parameters. Excel and Mex 6.0 software were utilized for quantitative and stereoscopic analysis. The study found varying effects on surface roughness posttreatment. RS Disco samples exhibited higher surface roughness compared with UTM and XA samples, both in average and nanoscale roughness. Decontamination led to increased surface roughness for all samples, particularly RS Disco. Fibroblast growth tests revealed enhanced cell network formation on decontaminated discs, possibly due to increased nanoscale roughness or the presence of bicarbonate salts. The study underscores the complex interplay between surface topography, microbial biofilm, and treatment efficacy in peri-implant disease management. While smoother surfaces may resist biofilm accumulation, increased nanoscale roughness postdecontamination can enhance fibroblast attachment and soft tissue integration. This dichotomy highlights the need for tailored treatment protocols that consider material-specific factors, emphasizing that successful implant therapy should balance microbial control with conducive surface characteristics for long-term osseointegration and soft tissue stability.

Fabrication of a Nanoscale Magnesium/Copper Metal-Organic Framework on Zn-Based Guided Bone Generation Membranes for Enhancing Osteogenesis, Angiogenesis, and Bacteriostasis Properties.

Recently, zinc (Zn) and its alloys have demonstrated great potential as guided bone regeneration (GBR) membranes to treat the problems of insufficient alveolar bone volume and long-term osseointegration instability during dental implantology. However, bone regeneration is a complex process consisting of osteogenesis, angiogenesis, and antibacterial function. For now, the in vivo osteogenic performance and antibacterial activity of pure Zn are inadequate, and thus fabricating a platform to endow Zn membranes with multifunctions may be essential to address these issues. In this study, various bimetallic magnesium/copper metal-organic framework (Mg/Cu-MOF) coatings were fabricated and immobilized on pure Zn. The results indicated that the degradation rate and water stability of Mg/Cu-MOF coatings could be regulated by controlling the feeding ratio of Cu2+. As the coating and Zn substrate degraded, an alkaline microenvironment enriched with Zn2+, Mg2+, and Cu2+ was generated. It significantly improved calcium phosphate deposition, differentiation of osteoblasts, and vascularization of endothelial cells in the extracts. Among them, Mg/Cu1 showed the best comprehensive performance. The superior antibacterial activity of Mg/Cu1 was demonstrated in vitro and in vivo, which indicated significantly enhanced bacteriostatic activity against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli as compared to that of the bare sample. Bimetallic Mg/Cu-MOF coating could properly coordinate the multifunction on a Zn membrane and could be a promising platform for promoting its bone regeneration, which could pave the way for Zn-based materials to be used as barrier membranes in oral clinical trials.

An osteoinductive surface by adhesive bone morphogenetic protein-2 prepared using the bioorthogonal approach for tight binding of titanium with bone.

Inorganic biomaterials are used in various orthopedic and dental implants. Nevertheless, they cause clinical issues such as loosening of implants and patient morbidity. Therefore, inspired by mussel adhesive proteins, we aimed to design an adhesive and dimer-forming highly active bone morphogenetic protein-2 (BMP-2) using bioorthogonal chemistry, in which recombinant DNA technology was combined with enzymatic modifications, to achieve long-term osseointegration with titanium. The prepared BMP-2 exhibited substantially higher binding activity than wild-type BMP-2, while the adhered BMP-2 was more active than soluble BMP-2. Therefore, the adhesive BMP-2 was immobilized onto titanium wires and screws and implanted into rat bones, and long-term osteogenesis was evaluated. Adhesive BMP-2 promoted the mechanical binding of titanium to bones, enabling efficient bone regeneration and effective stabilization of implants. Thus, such adhesive biosignaling proteins can be used in regenerative medicine.

Static in bone implants: standard steady-state torque and primary stability in a bioactive kinetic screw

Establishing a standard measurement for drilling and screwing bone implants in different amounts and qualities of bone tissue, in a simple and adequate way to control and predict results, is the gold standard for successful primary stability and better results on long-term osseointegration. So far, the maximum insertion torque (MIT) has been used as the main parameter to achieve success in primary stability and osseointegration, although it has shown conflicting results in the literature for over four decades when predicting standard or minimum values. Basically, the surgeon's experience guides the planning and execution of the surgical procedure, adapted in each case according to his tactile experience, guided by X-ray analysis and the bone and general conditions of the patient. In this work, using a new biomechanical simple machine as a dental implant, a new method will be described mathematically and experimentally, which standardizes the compression and torque in the implant-bone contact, in five different bone densities, during the achievement of mechanical primary stability. The results described the relationship between the MIT, maximum removal torque, and maximum force of static friction between implant-bone and bone-to-bone, achieving a controlled and predictable standard steady-state torque that maintains equilibrium in elastic stress for the primary stability of bone implants, hereby established for an innovative simple machine Bioactive Kinetic Screw.

Interface contact behavior of 3D printed porous surfaces

When a 3D printed implant integrates a thin surface lattice, the geometry of this porous region controls the bone-implant interface, affecting both short-term implant stability and long-term osseointegration. In intervertebral devices, for example, high expulsion resistance and propensity to subside are imperative in reducing implant migration and loss of disc height. Moreover, the shear strength of the porous-solid metal interface is critical to prevent metal-to-metal decohesion prior to and after osseointegration. While lap shear and subsidence tests are both governed by ASTM standards, expulsion testing is not standardized, and the tradeoffs in the potential implant failure modes have not been thoroughly investigated to find an optimal porosity satisfactory in all three performance tests. In this multi parameter study, we perform a series of experiments on 3D printed porous gyroid surfaces to understand the interplays and inherent tradeoffs between porosity, expulsion resistance, propensity to subside, and porous layer strength. Porosity was the only significant factor affecting expulsion, subsidence, and ultimate shear strength. As porosity increased, expulsion resistance of the surface porosity sample increased, resulting in samples that are harder to push out of a constrained bony cavity; however, shear strength and propensity to subside both decreased, resulting in a weaker metal-to-metal porous layer adhesion and equivalent penetration into the Sawbone surface at lower forces. Within the error of the measurements, the 6 × 6 × 6 0.75 mm wall thickness gyroid (65% modeled porosity and 62% measured porosity) design presented the best overall performance characteristics.

Influence of a Calcium Phosphate Coating (BONIT®) on the Proliferation and Differentiation Potential of Human Mesenchymal Stroma Cells in the Early Phase of Bone Healing.

When implanting osteosynthetic materials or orthopedic implants, the surface condition plays a decisive role for mid- to long-term osseointegration. BONIT®, an electrochemically produced calcium phosphate (CaP) coating, has been used in the surface refinement of implants since 1995. More than 3.5 million coated implants have been successfully placed so far. BONIT® has thus been able to demonstrate clinical success. However, due to its surface properties and solubility, and the resulting difficulty in culturing cells, there are no in vitro studies investigating its influence at the molecular level, particularly on bone metabolism. In a first step, the cells from a total of ten donors were seeded separately on four different surfaces: 1. a pure corundum-blasted titanium surface (CELLTex®, CT), 2. CT with additional BONIT® coating (CT + B), 3. a hydroxyapatite-blasted titanium surface (DUOTex®, DT), 4. DT with additional BONIT® coating (DT + B). In a second step, the cells were grown for 48 h. The proliferation behavior and differentiation potential of hMSCs were investigated at three consecutive time points (12 h, 24 h and 48 h) by quantifying the mRNA expression of ten important differentiation markers using quantitative real-time polymerase chain reaction (qRT-PCR). We were able to show that BONIT® has an influence on the early proliferation and differentiation behavior of hMSCs in patients of all age groups. The additional BONIT® coating on CELLTex® or DUOTex® led to a defined mRNA expression pattern for the investigated factors: a tendency towards a higher expression rate with coating present could be found for bone morphogenetic protein 2 (BMP2), osteopontin (OPN), osteocalcin (OC), receptor activator of NF-κB ligand (RANKL) and osteoprotegerin (OPG). A similar or lower expression rate was detected for runt-related transcription factor 2 (RUNX2), alpha-1 type I collagen (COL1A1), alkaline phosphatase (AP), osteonectin (ON) and insulin-like growth factor I (IGF1). We have developed a new method that allows the cultivation of human mesenchymal stromal cells (hMSCs) on the soluble coating BONIT® for gene expression analysis. BONIT® has a significant influence on the proliferation and differentiation behavior of human mesenchymal stroma cells. This study describes a defined gene expression pattern of bone metabolism that may help to understand the influence of this CaP coating on the early phase of implant osseointegration.

Assessing the long-term in vivo degradation behavior of magnesium alloys - a high resolution synchrotron radiation micro computed tomography study

Biodegradable magnesium (Mg) implants are emerging as a potential game changer in implant technology in situations where the implant temporarily supports the bone thereby avoiding secondary surgery for implant removal. However, the consequences of the alteration in the degradation rate to bone healing and the localization of degradation and alloying products in the long term remain unknown. In this study, we present the long-term osseointegration of three different biodegradable Mg alloys, Mg-10Gd, Mg-4Y-3RE and Mg-2Ag, which were implanted into rabbit femur for 6 and 9 months. In addition, we have investigated the effect of blood pre-incubation on the in vivo performance of the aforementioned alloys. Using high-resolution synchrotron radiation based micro computed tomography, the bone implant contact (BIC), bone volume fraction (BV/TV) and implant morphology were studied. The elemental traces have been characterized using micro X-ray fluorescence. Qualitative histological evaluation of the surrounding bone was also performed. Matured bone formed around all three implant types and Ca as well as P which represent parts of the degradation layer were in intimate contact with the bone. Blood pre-incubation prior to implantation significantly improved BIC in Mg-2Ag screws at 9 months. Despite different implant degradation morphologies pointing toward different degradation dynamics, Mg-10Gd, Mg-4Y-3RE and Mg-2Ag induced a similar long-term bone response based on our quantified parameters. Importantly, RE elements Gd and Y used in the alloys remained at the implantation site implying that they might be released later on or might persist in the implantation site forever. As the bone formation was not disturbed by their presence, it might be concluded that Gd and Y are non-deleterious. Consequently, we have shown that short and mid-term in vivo evaluations do not fully represent indicators for long-term osseointegration of Mg-based implants.

Long-term osseointegration of laser-ablated hearing implants in sheep cranial bone.

Osseointegration, the ability for an implant to be anchored in bone tissue with direct bone-implant contact and allowing for continuous adaptive remodelling, is clinically used in different reconstructive fields, such as dentistry, orthopedics and otology. The latter uses a bone conducting sound processor connected to a skin-penetrating abutment that is mounted on a titanium implant placed in the temporal bone, thereby acting as a path for transmission of the vibrations generated by the sound processor. The success of the treatment relies on bone healing and osseointegration, which could be improved by surface modifications. The aim of this study was to evaluate the long-term osseointegration in a sheep skull model and compare a laser-ablated implant surface with a machined implant. Commercially available 4 mm titanium implants, either with a machined (Wide Ponto) or a laser-ablated surface (Ponto BHX, Oticon Medical, Sweden), were used in the current study. The surfaces were evaluated by scanning electron microscopy. The implantation was performed with a full soft tissue flap and the osteotomy was prepared using the MIPS drill kit (Oticon Medical, Sweden) prior to installation of the implants in the frontal bone of eight female sheep. After five months, biopsies including the implant and surrounding bone tissue obtained, processed and analysed using histology, histomorphometry, scanning electron microscopy and Raman spectroscopy. The animals healed well, without signs of adverse events. Histomorphometry showed a large amount of bone tissue around both implant types, with 75% of the threaded area occupied by bone for both implant types. A large amount of bone-implant contact was observed for both implant types, with 67%–71% of the surface covered by bone. Both implant types were surrounded by mature remodelled lamellar bone with high mineral content, corroborating the histological observations. The current results show that the laser-ablated surface induces healing similar to the well-known clinically used machined surface in ovine cranial bone. In conclusion, the present long-term experimental results indicate that a laser-ablated implant performs equally well as a clinically used implant with a machined surface. This, together with previously reported, improved early biomechanical anchorage, suggests future, safe and efficient clinical potential.

Type I collagen decorated nanoporous network on titanium implant surface promotes osseointegration through mediating immunomodulation, angiogenesis, and osteogenesis

Osseointegration of implants is a complex physiological process that requires temporal and spatial regulation of immune responses, angiogenesis, and osteogenesis. To achieve efficient and long-term osseointegration, type I collagen (COL1) decorated nanoporous network was developed on titanium substrates via alkali treatment, polydopamine coating, and layer-by-layer (LBL) self-assembly. It was noted that the simple physisorbed COL1 could be easily desorbed from the nanostructured surface, however, multilayer COL1 constructed by polydopamine and LBL self-assembly obscured the nanoporous network of the alkali-treated titanium surfaces. Interestingly, the nanostructured surface covalently immobilized with COL1 (T-ADC) could timely convert macrophages (MΦs) from pro-inflammatory M1 to pro-healing M2 phenotype, generating a beneficial osteoimmune microenvironment and promoting angio/osteo-genesis. RNA sequencing revealed that the nanostructure and COL1 could synergistically activate RhoA/ROCK, PI3K-AKT, and classical MAPK signaling pathways in MΦs to sustain the cell cycle, and trigger autocrine feedback-mediated JAK-STAT and FoxO signaling pathways, which in turn motivated autophagy and oxidative stress resistance and attenuated lipopolysaccharide-induced Toll-like receptor signaling pathway and its downstream NF-κB and JNK/p38 MAPK signaling cascades, leading to the inhibition of inflammation and osteoclastic-related gene expression of MΦs. Simultaneously, T-ADC prominently facilitated angiogenesis of endothelial cells and osteogenesis of osteoblasts as well as their cross-talks, further highlighting synergistically positive effects of the nanostructure and COL1 on osseointegration. In vivo experiments revealed that T-ADC could induce abundant new bone mass and ameliorative osseointegration, corroborating the in vitro results. The study elucidated that the COL1 decorated nanoporous network on titanium surfaces could significantly regulate early inflammatory reaction and subsequent angio/osteo-genesis processes, resulting in favorable osseointegration.

Effects of 3D printed surface topography and normal force on implant expulsion

3D printing is a critical method for manufacturing metallic implants as it enables direct fabrication of intricate geometries and porous structures inaccessible to other manufacturing methods. Some common 3D printed porous structures are strut based (e.g. octet truss), triply periodic minimal surfaces (TPMS) (e.g. gyroid) or randomized (e.g. stochastic). When designed to be on the surface of bone interfacing implants, the surface porous region impacts short-term adhesion and friction, ultimately affecting implant stability prior to and during long-term osseointegration. In many orthopedic procedures, expulsion resistance is an essential design requirement, to prevent the risk of the implant migrating from the implantation site. While expulsion tests are universal, they are a poorly understood method to examine the bone-implant interface in determining the performance of an orthopedic implant. In this foundational study, we examine the expulsion behavior of metallic samples in synthetic Sawbone with systematically varied surface topography at increasing applied normal forces. The applied normal force and size of the sample were shown to have the strongest influence on expulsion force followed by surface structure. Compared to a polished sample control, certain 3D printed surface structures are up to 10x more expulsion resistant and should be considered in implants where prevention of implant migration before and during osseointegration is critical. Nonlinear relationships were discovered that reveal “crossover” in expulsion resistance as a function of applied load revealing that the ranking of the relative expulsion resistance of different samples can depend on the normal force selected. This new fundamental understanding has broad implications on both the design and potential standardized regulatory testing of textured orthopedic implants with tailored topologies.

Analytical Techniques for the Characterization of Bioactive Coatings for Orthopaedic Implants.

The development of bioactive coatings for orthopedic implants has been of great interest in recent years in order to achieve both early- and long-term osseointegration. Numerous bioactive materials have been investigated for this purpose, along with loading coatings with therapeutic agents (active compounds) that are released into the surrounding media in a controlled manner after surgery. This review initially focuses on the importance and usefulness of characterization techniques for bioactive coatings, allowing the detailed evaluation of coating properties and further improvements. Various advanced analytical techniques that have been used to characterize the structure, interactions, and morphology of the designed bioactive coatings are comprehensively described by means of time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), 3D tomography, quartz crystal microbalance (QCM), coating adhesion, and contact angle (CA) measurements. Secondly, the design of controlled-release systems, the determination of drug release kinetics, and recent advances in drug release from bioactive coatings are addressed as the evaluation thereof is crucial for improving the synthesis parameters in designing optimal bioactive coatings.

Habitual caffeine intake affects implant osseointegration: An in vivo study.

This study aimed to evaluate the effect of habitual caffeine (CAF) intake on stability, bone regeneration, and expression of bone markers at the bone-implant interface. Studies show that habitual CAF alters bone health and remodeling. Yet, there is no information regarding CAF effects on osseointegration of bone-anchored implants. Wistar rats were divided into two groups: one received tap drinking water alone (control) and the other received tap water with CAF (300mg/L). After 12weeks, their tibiae received screw-shaped titanium implants. After another 12weeks, CAF (n=5) and control (n=5) animals were sacrificed and the implant stability was evaluated using a removal torque (RTQ) device. Thereafter, the implants were processed for gene expression analysis, and the implantation sites were harvested for histology. Implants with the surrounding bone were dissected en bloc and subjected to micro-computed tomography (micro-CT). The results showed that implants in the CAF group had an 87% significant increase in RTQ compared to the control. Further, micro-CT revealed a higher proportion of mineralized bone filling the implant threads in the CAF group. The molecular analysis indicated higher expression of bone formation (ALP), remodeling (CatK), and vascularization (VEGF) genes in implant-adherent cells in the CAF group. Histology suggested increased vascularity in the tissue surrounding the implant in the CAF group. Within the limit of this study, it is concluded that habitual CAF intake conveys a positive, promoting effect on long-term osseointegration. Clinical studies are worth pursuing to verify this experimental observation.

Comparative outcome analysis of osseointegrated reconstruction and replantation for digital amputations.

The long-term outcomes of osseointegration for digital amputations are not well established, and it is not known whether osseointegration can achieve similar function and patient satisfaction to conventional surgical options such as replantation and microsurgical toe transfer. We compared the long-term outcomes after digital osseointegration and replantation. Six patients treated by osseointegration and seven patients treated by replantation were included, with median follow-ups of 8 years and 4.6 years, respectively. Outcomes were assessed using the Michigan Hand Outcomes Questionnaire, grip and pinch strength, range of motion, two-point discrimination, Semmes-Weinstein tests, Jebsen-Taylor Hand Function Test and clinical photography. Osseointegration was associated with poorer sensibility and range of motion than replantation; no other differences reached statistical significance. Long-term osseointegration is a safe and effective reconstructive option that can deliver excellent outcomes in appropriately selected patients.Level of evidence: IV.

Energy-Dispersive X-ray Spectroscopic Investigation of Failed Dental Implants Associated with Odontogenic Maxillary Sinusitis

The failed dental implant associated with maxillary sinusitis is a multifactorial phenomenon and should be investigated thoroughly. The inflammatory process induced by accumulated biofilm and wear debris may increase mucous secretion and mucous thickening, which finally may lead to severe complications such as maxillary sinusitis. The inflammatory cytokines might compromise the long-term osseointegration of the related implant. In this study, implants retrieved from three patients who experienced implant failure relating to maxillary sinusitis were investigated using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy. SEM analysis of the implant apical region revealed a less-compact bone structure, indicating the high bone turnover due to an inflammatory process. The ratio of calcium (Ca) and phosphorus (P) was negligible in all specimens. Detection of fluorine (F), sodium (Na), silicon (Si), gold (Au), aluminum (Al), and magnesium (Mg) confirmed the contamination. The selected cases presented different biological aspects that might play the central role in the failed dental implants associated with maxillary sinusitis: the contamination of potentially toxic elements, microorganism infection, and long perforation of implant apex into the sinus. Each of the above phenomena needs to be confirmed with further clinical study with a larger number of failed implants and accompanying tissue samples.

Effects of chloride substitution on physical, mechanical, and biological properties of hydroxyapatite

Synthetic hydroxyapatite (HAp) bioceramics commonly serve as non-load bearing implants due to their bone-like composition. Additionally, the porous structure promotes tissue ingrowth and osseointegration. However, HAp bioceramics have insufficient mechanical properties and low bioactivity. This study aims to evaluate how substituted chloride levels in hydroxyapatite (ClHAP) affect the surface and mechanical properties, and osteoblastic response.ClHAP was made via an aqueous precipitation method followed by hydraulic compaction and sintering at 1100 °C for 16 h. This study demonstrated highly densified 2–10% ClHAP bioceramics with outstanding surface hardness and compressive strength, and enhanced surface wettability, relative to other HAp bioceramics. The 2–10% ClHAP bioceramics showed slight acidity and chloride release in vitro, which did not significantly affect the osteoblast adhesion or proliferation. In conclusion, 2–10% ClHAP bioceramics are optimal for implantation for their superior surface and mechanical properties, biocompatibility, and potential for long-term osseointegration.

Early Loading of Titanium Dental Implants with an Intraoperatively Conditioned Hydrophilic Implant Surface: 3-Year Results of a Prospective Case Series Study.

The hydrophilic implant surface (INICELL) is a chemical alteration of a sandblasted and thermally acid-etched surface that should lead to long-term osseointegration. This study investigated 3-year results after early loading of implants with a hydrophilic, moderately rough surface in occlusal contact. This prospective case series study was conducted in subjects with partially edentulous mandibles. Implants were placed on day 21 and loaded with a provisional reconstruction after at least 21 days of healing (baseline, day 0) if their implant stability quotient (ISQ) was ≥ 70 (mean of three measurements) and were replaced by definitive porcelain-fused-to-metal prostheses at the 6-month follow-up visit. Follow-up examinations were planned 1, 3, 6, 12, and 36 months after baseline. A total of 20 implants were placed in 15 patients (mean age: 51 years, range: 32 to 67 years). After 36 months, all implants were osseointegrated, and no suppuration was recorded. Small changes of bone level were observed between 3 months and 36 months. At 36 months, the median values of the 20 implants were 0.25 (range: 0 to 0.5, SD: 0.17), 0.25 (range: 0 to 1, SD: 0.27), and 4 (range: 2 to 7.25, SD: 1.17) for the mean modified Plaque Index (mPI), mean modified Sulcus Bleeding Index (mSBI), and mean probing pocket depth, respectively. The pairwise analysis between 3 and 36 months showed an improvement in the mean mPI (P = .0126) and mean mSBI (P = .0059). After 36 months, all patients (n = 15) were fully satisfied with a mean of 9.43 (range: 8 to 10, SD: 0.678) at the visual analog scale. Early functional loading of implants with a hydrophilic, moderately rough outer surface in occlusal contact 21 days after healing appears to be a safe and feasible treatment option when placed in the posterior mandible of partially edentulous patients.

Finite-Element analysis of a lateral femoro-tibial impact on the total knee arthroplasty

Background and ObjectiveTotal knee arthroplasty (TKA) is a routine surgery performed to treat patients with severe knee osteoarthritis. The success of a TKA depends strongly on the initial stability of the prosthetic components and its long-term osseointegration due to the optimal distribution of mechanical stresses in the surrounding bones under the effect of the different biomechanical loads applied to the Femur-TKA-Tibia system. The purpose of this study is to analyze the level and the distribution of the induced stresses in a Femur-TKA-Tibia system subjected to combined triaxial forces, which mimic a femoral mechanical shock. MethodsIn this study, complex TKA system implanted in both femoral and tibial bones has been analyzed numerically with a three-dimensional finite-element method. A virtual model is designed to examine in silico the effect of the combined triaxial forces acting on this prosthesis in femoral region. Anatomical three-dimensional finite-element models of both femoral and tibial bones were constructed to calculate the interfacial stresses around the TKA components. The 3D finite-element processing program ABAQUS was used to perform the analysis. ResultsThe stresses propagated in the bone regions adjacent to the TKA osseointegrated components, and the decreased in their magnitude to the outer region. These stresses reached the highest level in the cortical bone areas that are right next to the proximal upper attachment portions of the TKA osseointegrated components. The magnitude of the stresses in the tibial component is higher than that in the femoral component. Finally, it is very important to emphasize the role of the polyethylene articulating spacer in the shock absorption of bone support sections. Thus, this component should be preserved mechanically from the impact of high shocks in order to maintain healthy TKA systems. ConclusionsOptimizing TKA model by controlling the biomechanical stresses distributed within its both components and supporting bones is a valid approach to achieving favorable long-term outcomes. The 3D finite-element analysis provides an effective pre-operative method for planning patient-specific TKA prostheses, and for designing future models that preserves the biomechanical function of the Femur-TKA-Tibia system.

Initial stability of a percutaneous osseointegrated endoprosthesis with proximal interlocking screws for transhumeral amputees

BackgroundPercutaneous osseointegrated devices for skeletal fixation of prosthetic limbs have the potential to improve clinical outcomes in the transhumeral amputee population. Initial endoprosthesis stability is paramount for long-term osseointegration and safe clinical introduction of this technology. We evaluated an endoprosthetic design featuring a distally porous coated titanium stem with proximal slots for placement of bicortical interlocking screws. MethodsYield load, ultimate failure load, and construct stiffness were measured in 18 pairs of fresh-frozen and thawed cadaver humeri, at distal and proximal amputation levels, without and with screws, under axial pull-out, torsion, and bending loads. Paired statistical comparisons were performed without screws at the two resection levels, and at distal and proximal levels with and without screws. FindingsWithout screws, the location of the amputation influenced the stability only in torsional yield (p = 0.032) and torsional ultimate failure (p = 0.033). Proximally, the torsional yield and the torsional ultimate failure were 44% and 47% of that distally. Screws improved stability. In axial pull-out, screws increased the distal ultimate failure 3.2 times (p = 0.003). In torsion, screws increased the yield at the proximal level 1.9 times (p = 0.035), distal ultimate failure load 3.3 times (p = 0.016) and proximal ultimate failure 6.4 times (p = 0.013). In bending, screws increased ultimate failure at the proximal level 1.6 times (p = 0.026). InterpretationProximal slots and bicortical interlocking screws may find application in percutaneous osseointegrated devices for patients with amputations, especially in the less stable proximal bone of a short residual limb.

Factors That Influence Bone-Ingrowth Fixation of Press-Fit Acetabular Cups.

» In order to obtain long-term osseointegration, a press-fit acetabular cup must gain initial rigid stability with limited micromotion. In addition, the implant surface must promote ingrowth and maintain contact with viable bone.» Two-dimensional (2D) ongrowth surfaces that have been plasma-spray-coated (heated titanium alloy powder that is flame-sprayed on the substrate) and blasted with grit (surface roughness 4 to 6 µm) achieve fixation via bone interlocking into irregularities in the surface of the implant. Tridimensional ingrowth surfaces, such as titanium fiber mesh (titanium fiber diffusion-bonded to the substrate) and sintered cobalt-chromium and titanium beads, yield secure fixation when bone forms in the voids of the 3-dimensional (3D) surface.» Porous metals that mimic the trabeculae of bone and have a modulus of elasticity similar to bone have higher coefficients of friction than older designs and have demonstrated excellent osteoconductive properties. Not only do these highly porous 3D ingrowth surfaces have a high coefficient of friction, they have demonstrated higher initial stability compared with 2D ongrowth surfaces and older 3D ingrowth surface designs.» Acetabular cups promote biologic fixation with various tridimensional metal surfaces. Materials including porous Trabecular Metal (Zimmer Biomet) have been proven to achieve good osseointegration in patients with poor host bone, including patients with previous radiation exposure, osteonecrosis, or metabolic bone disease, or those who are undergoing revision surgery.

Biomimetic fluoridated hydroxyapatite coating with micron/nano-topography on magnesium alloy for orthopaedic application

Biomimicry strategies, inspired by nature, are being widely used in the design of advanced biomaterials. Learning from the topographic landscape of natural bone resorption surface, which consists of micron/submicron-scale resorption lacunae and nano-scale sharp-tipped collagen fibrils, herein, a biomimetic fluoridated hydroxyapatite (FHA) coating composed of bilayer arrays of nanoneedles with micron/nano-topography was constructed on magnesium alloy surface via a microwave aqueous approach. The FHA coating possesses micron/submicron-scale roughness so as to mimic resorption lacunae. In parallel, the nanoneedles exhibit similar size and shape to collagen fibrils, especially their sharp tips. The surface topography, growth mechanism, osteogenic differentiation capacity and protection performance of this FHA coating were investigated. In vitro biological test showed that FHA coating significantly enhanced osteogenic differentiation capacity comprared with hydroxyapatite (HA) coating. Moreover, simulated body fluid immersion test demonstrated that FHA coating combined with formed HA mineralized layer together offered favorable long-term protection for magnesium alloy. This work may provide a new avenue of biomimetic surface topography design for orthopaedic implants with superior osteogenic differentiation capacity and corrosion resistance for long-term osseointegration of implants and fast bone regeneration.