Abstract A newly developed magnesium implant is used to stimulate bone formation in vivo . The magnesium implant after undergoing dual aluminum and oxygen plasma implantation is able to suppress ...rapid corrosion, leaching of magnesium ions, as well as hydrogen gas release from the biodegradable alloy in simulated body fluid (SBF). No released aluminum is detected from the SBF extract and enhanced corrosion resistance properties are confirmed by electrochemical tests. In vitro studies reveal enhanced growth of GFP mouse osteoblasts on the aluminum oxide coated sample, but not on the untreated sample. In addition to that a small amount (50 ppm) of magnesium ions can enhance osteogenic differentiation as reported previously, our present data show a low concentration of hydrogen can give rise to the same effect. To compare the bone volume change between the plasma-treated magnesium implant and untreated control, micro-computed tomography is performed and the plasma-treated implant is found to induce significant new bone formation adjacent to the implant from day 1 until the end of the animal study. On the contrary, bone loss is observed during the first week post-operation from the untreated magnesium sample. Owing to the protection offered by the Al2 O3 layer, the plasma-treated implant degrades more slowly and the small amount of released magnesium ions stimulate new bone formation locally as revealed by histological analyses. Scanning electron microscopy discloses that the Al2 O3 layer at the bone-implant interface is still present two months after implantation. In addition, no inflammation or tissue necrosis is observed from both treated and untreated implants. These promising results suggest that the plasma-treated magnesium implant can stimulate bone formation in vivo in a minimal invasive way and without causing post-operative complications.
Five different sacral fracture fixation methods were compared using finite element (FE) analysis to study their biomechanical characteristics.
Denis type I sacral fractures were created by FE ...modeling. Five different fixation methods for the posterior pelvic ring were simulated: sacroiliac screw (SIS), lumbopelvic fixation (LPF), transiliac internal fixator (TIFI), S2-alar-iliac (S2AI) screw and S1 pedicle screw fixation (S2AI-S1) and S2AI screw and contralateral S1 pedicle screw fixation (S2AI-CS1). Four different loading methods were implemented in sequence to simulate the force in standing, flexion, right bending and left twisting, respectively. Vertical stiffness, relative displacement and change in relative displacement were recorded and analyzed.
As predicted by the FE model, the vertical stiffness of the five groups in descending order was S2AI-S1, SIS, S2AI-CS1, LPF and TIFI. In terms of relative displacement, groups S2AI-S1 and S2AI-CS1 displayed a lower mean relative displacement, although group S2AI-CS1 exhibited greater displacement in the upper sacrum than group S2AI-S1. Group SIS displayed a moderate mean relative displacement, although the displacement of the upper sacrum was smaller than the corresponding displacement in group S2AI-CS1, while groups LPF and TIFI displayed larger mean relative displacements. Finally, in terms of change in relative displacement, groups TIFI and LPF displayed the greatest fluctuations in their motion, while groups SIS, S2AI-S1 and S2AI-CS1 displayed smaller fluctuations.
Compared with SIS, unilateral LPF and TIFI, group S2AI-S1 displayed the greatest biomechanical stability of the Denis type I sacral fracture FE models. When the S1 pedicle screw insertion point on the affected side is damaged, S2AI-CS1 can be used as an appropriate alternative to S2AI-S1.
To achieve enhanced biological response and controlled degradation of magnesium alloy, a modified biodegradable polymer coating called polycaprolactone (PCL) is fabricated by a thermal approach in ...which the heat treatment neither alters the chemical composition of the PCL membrane nor the rate of magnesium ion release, pH value, or weight loss, compared with the untreated sample. The changes in the crystallinity, hydrophilicity, and oxygen content of heat‐treated PCL coating not only improve the mechanical adhesion strength between the coating and magnesium substrate but also enhance the biological properties. Moreover, the thermally modified sample can lead to higher spreading and elongation of osteoblasts, due to the enhanced hydrophilicity and CO to CO functional group ratio. In the analyses of microcomputed tomography from one to four weeks postoperation, the total volume of new bone formation on the heat‐treated sample is 10%–35% and 70%–90% higher than that of the untreated and uncoated controls, respectively. Surprisingly, the indentation modulus of the newly formed bone adjacent to the heat‐treated sample is ≈20% higher than that of both controls. These promising results reveal the clinical potential of the modified PCL coating on magnesium alloy in orthopedic applications.
Schematic illustrating the effects of the change of the ratio between CO and CO before and after the heat treatment as well as release of Mg on osteoblast adhesion and bone formation: (a) Before the heat treatment, cell spreading of osteoblasts diminished and (b) after the heat treatment, cell spreading on the PCL membrane is enhanced.
The side‐by‐side assembly of gold nanorods (GNRs) was shown to be directed by the supramolecular scaffolds formed by sulfonate‐containing alkynylplatium(II) terpyridine complexes. Driven by Pt⋅⋅⋅Pt ...and π–π stacking interactions, the PtII complex has a high propensity to assemble in water with the head‐to‐tail stacking arrangement to construct supramolecular scaffolds, in which the sulfonate groups on the terpyridine ligand at the peripheral position preferentially bind to the sides of the GNRs. The extent of the assembly of the GNRs into ladder rung‐like nanostructures can be modulated by the concentration of the PtII complex. The Pt⋅⋅⋅Pt interaction‐assisted formation of the scaffolds and its directed assembly of GNRs were characterized by UV/Vis spectroscopy, quantum‐chemical modeling, electron microscopy, energy dispersed X‐ray (EDX) analysis, and SERS. This work provides insights for the construction of higher‐ordered nano‐assemblies using both Pt⋅⋅⋅Pt interactions and template‐directed approaches.
Side‐by‐side assembly: Supramolecular scaffold‐templated side‐by‐side assembly of gold nanorods (GNRs) has been demonstrated by utilizing the sulfonate‐containing alkynylplatinum(II) terpyridine complexes. Driven by non‐covalent and directional Pt⋅⋅⋅Pt and π–π stacking interactions, the complexes show a high propensity to assemble in water with the plausible head‐to‐tail stacking arrangement to construct supramolecular scaffolds.
A range of magnesium ions (Mg2+) used has demonstrated osteogenic tendency in vitro. Hence, we propose to actualize this concept by designing a new system to precisely control the Mg2+ delivery at a ...particular concentration in vivo in order to effectively stimulate in-situ bone regeneration. To achieve this objective, a monodisperse core-shell microsphere delivery system comprising of poly (lactic-co-glycolic acid) (PLGA) biopolymer, alginate hydrogel, and magnesium oxide nano-particles has been designed by using customized microfluidic capillary device. The PLGA-MgO sponge-like spherical core works as a reservoir of Mg2+ while the alginate shell serves as physical barrier to control the outflow of Mg2+ at ∼50 ppm accurately for 2 weeks via its adjustable surface micro-porous network. With the aid of controlled release of Mg2+, the new core-shell microsphere system can effectively enhance osteoblastic activity in vitro and stimulate in-situ bone regeneration in vivo in terms of total bone volume, bone mineral density (BMD), and trabecular thickness after operation. Interestingly, the Young's moduli of formed bone on the core-shell microsphere group have been restored to ∼96% of that of the surrounding matured bone. These findings indicate that the concept of precisely controlled release of Mg2+ may potentially apply for in-situ bone regeneration clinically.
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The end-to-end aggregation of gold nanorods (GNRs) has been demonstrated to be directed by a thioacetate-containing alkynylplatinum(II) terpyridine complex. The in situ deprotected complex is ...preferentially attached at the ends of the gold nanorods (GNRs) and induce the aggregation of GNRs in an “end-to-end” manner by Pt···Pt and π–π interactions, which have been characterized by electron microscopy, energy dispersed X-ray (EDX) analysis, and UV–vis absorption spectroscopy. The assembly of the nanorods into chain-like nanostructures can be controlled by the concentration of the Pt(II) complexes.
Although S2 alar‐iliac screw technique has been widely used in spinal surgery, its applicability to pelvic fractures is largely unknown. This study aimed to evaluate the biomechanical stability of S2 ...alar‐iliac screw and S1 pedicle screw fixation in the treatment of Denis II sacral fractures. Twenty‐eight artificial pelvic fracture models were treated with unilateral lumbopelvic fixation, sacroiliac screw fixation, S2 alar‐iliac screw and S1 pedicle screw fixation, and S2 alar‐iliac screw and contralateral S1 pedicle screw fixation (Groups 1–4, respectively; N = 7 per group). Each model was cyclically tested under increasing axial compression. Optical motion‐tracking was used to assess relative displacement and gap angle, and the number of failure cycles. Relative displacement was significantly smaller in Group 3 than in Groups 1 (p = 0.004) and 4 (p < 0.001) but not significantly different between Groups 3 and 2 (p = 0.290). The gap angle in Group 3 was significantly smaller than that in Group 1 (p = 0.009) on the sagittal plane but significantly larger than that in Group 4 (p = 0.006) on the horizontal plane. A number of failure cycles was significantly higher in Group 3 than in Groups 1 (p = 0.002) and 4 (p = 0.004) but not significantly different between Groups 3 and 2 (p = 0.910). From a biomechanical perspective, S2 alar‐iliac screw and S1 pedicle screw fixation can provide good stability in the treatment of Denis II sacral fractures.
The use of dynamic finite element analysis to investigate the biomechanical behavior of the knee joint is mainly based on movement of the joint. Challenges are associated with simulation of knee ...joint flexion-extension activity. This study investigated changes in the length and stress state of ligaments during lunge with a displacement controlled finite element analysis of the knee joint based on in vivo fluoroscopic kinematic data. The geometric center axis (GCA) was used to represent knee kinematics to quantify femoral motion relative to the tibia. Because the GCA was considered as a functional flexion axis, 2 degrees of freedom could be reduced. Published data on the in vivo fluoroscopic kinematic features of the GCA were used to establish the equations for degrees of freedom. Data for 4 degrees of freedom were obtained simultaneously at every 5° of knee flexion. Displacement and rotation were applied to the femur and tibia to produce relative displacement, and the elongation and stress state of the knee ligaments were computed. The predictions confirmed that lunge affected the biomechanical behavior of ligaments. Displacement controlled finite element analysis of knee flexion can be simulated on the basis of fluoroscopic kinematic data to achieve physiologic movement. Orthopedics. 2021;44(1):e61-e67..
Purpose:
To evaluate the quality of reduction and clinical outcomes by using Percutaneous Distractor and Subtalar Arthroscopy Closed Reduction followed by Internal Fixation (PDSA-CRIF) in the ...intra-articular calcaneal fracture.
Methods:
A consecutive case series of 453 patients with 507 displaced intra-articular calcaneal fractures was recruited in this retrospective study. We performed PDSA-CRIF to treat intra-articular calcaneal fractures. The quality of reduction was assessed by early postoperative Computed Tomography (CT) scans and measurement of serial Bohler’s angles during follow-ups. Clinical outcomes were evaluated by Visual Analogue Scale (VAS) and the American Foot & Ankle Society ankle-hind foot scale (AOFAS) scoring system.
Results:
Fifty-nine patients (68 fractures) who had complete clinical data and follow-up of at least 12-months (mean: 14 months, range: 12–59 months) were finally included. Anatomical and near-anatomical reduction in subtalar articular surface which had less than 2 mm gap or step-off was found in 93% fractures. Unsatisfactory reduction was found in 7%.
Conclusion:
Arthroscopic-assisted percutaneous fixation using a distraction device is effective in achieving positive short-term results in the displaced intra-articular calcaneal fractures. A multicenter, large sample, randomized control trial is needed to fully evaluate the long-term effects of PDSA-CRIF in comparison to other methods.
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