The tibial tubercle osteotomy (TTO) is a versatile tool for unloading patellar and trochlear focal chondral defects as well as treating patellofemoral arthritis with or without patellofemoral ...instability. The TTO indirectly functions to address chondral defects in the patellofemoral joint (PFJ) by unloading compressive forces in the affected area and preventing further chondral deterioration and pain. Since its inception, the TTO technique has undergone iterative modification and refinement. The Fulkerson anteromedialization has persisted as the workhorse of modern TTO procedures with good surgical results, though it is not without limitations. Recently, the use of novel surgical systems such as the multidirectional tibial tubercle transfer as well as concomitant soft tissue balancing procedures have been implemented to address challenges posed by the classic Fulkerson technique and improve TTO customizability and reproducibility. In addition, TTO has increasingly been used in conjunction with concomitant procedures such as autologous chondrocyte implantation and osteochondral allograft transfer in the PFJ, to protect the restored cartilage from repeat injury. Though the anteriorization TTO has long been supported to help alleviate pathologic joint compression, recent advancements in surgical guides as well as combined procedures involving multiplane TTO, cartilage restoration, and soft tissue balancing allow for customization of treatment that more thoroughly addresses the complex anatomy and pathology in the PFJ. This article aims to provide an overview of the rationale and recent advancements in the use of TTO to unload and treat chondral defects in the PFJ.
The formation of the mullite phase is the main challenge in the preparation of alumina-mullite-zirconia (AMZ) composites. To overcome this limitation, a novel method based on the coating of zircon ...powder with aluminum alkoxide was proposed in this study. Reaction sintering of alumina and coated zircon was carried out at 1630 °C for 3 h. The microstructural, physical, mechanical, and tribological properties of samples were compared with the conventional AMZ composites prepared by common mixing of alumina and zircon. The microstructural analysis indicated the higher alumina phase of the sample prepared with the conventional method. On contrary, the samples prepared with the proposed method included higher percentages of mullite phase. In terms of mechanical properties, the conventional AMZ samples performed better. However, due to the beneficial effect of the mullite phase in tribological applications, the samples prepared with this new method show superior wear resistance. Especially, the samples prepared from 30 wt% aluminum alkoxide exhibited the best wear resistance. The delamination and adhesive wear mechanisms govern the wear process.
This paper presents a new method for preparing alumina-mullite-zirconia (AMZ) composites. For this purpose, zircon particles were coated by aluminum alkoxide using a wet processing method. The ...effects of zircon particle size and aluminum alkoxide content)10, 30 and 50 wt % (on the reaction sintering of AMZ composites were investigated. The sintering of samples was carried out for 3 h at the maximum temperature of 1630 °C. Scanning electron microscopy (SEM) was used to investigate the coating process. Energy dispersive spectroscopy (EDS) analysis was also performed to detect the alkoxide coating on zircon particles. The phase constituents of the sintered samples were characterized using X-ray diffraction (XRD) method and estimated using the Rietveld refinement method utilizing MAUD software. The results indicated that aluminum alkoxide promoted the formation of mullite phase and improved the microstructural homogeneity of the final composites. This new approach proposed that using aluminum alkoxide coated zircon can support obtaining desirable phases in the fabrication of AMZ composites. In this way, milling of zircon particles can help alkoxide to provide a homogenous coating.
Background:
Isolated chondral lesions of the patella are particularly challenging to treat, and long-term studies of treated isolated patellar lesions are limited. Previous short-term studies have ...reported favorable outcomes of autologous chondrocyte implantation (ACI) of the patella and/or trochlea, with a trend toward improvement when anteromedialization (AMZ) of the tibial tubercle was performed with the procedure.
Hypothesis:
Autologous chondrocyte implantation with concomitant AMZ for symptomatic isolated patellar lesions provides functional and symptomatic improvement in patients at a minimum 5-year follow-up.
Study Design:
Case series; Level of evidence, 4.
Methods:
Patients with failed primary treatment of isolated patellar full-thickness articular cartilage defects and patellofemoral malalignment who were treated with ACI and AMZ of the tibial tubercle at least 5 years prior were contacted for final postoperative outcome scores. Outcome scales including the International Knee Documentation Committee (IKDC), Lysholm, modified Cincinnati Knee Rating System, and 12-item Short Form Health Survey (SF-12) scores were assessed at baseline and final follow-up.
Results:
Of 27 eligible patients, 23 (25 knees) were available for assessment at a mean follow-up of 7.6 years (range, 5.1-11.4 years). Significant improvements from baseline to final follow-up were observed in the IKDC score (from 42.5 to 75.7; P < .0001), modified Cincinnati Knee Rating System score (from 3.0 to 7.0; P < .0001), Lysholm score (from 40.2 to 79.3; P < .0001), and SF-12 score (physical component score: from 41.2 to 47.6; P = .002; mental component score: from 48.1 to 60.7; P = .0001). Most patients (83%; 19/23) rated their surgery as good or excellent. The overall reoperation rate was 40% (10/25) largely because of periosteal hypertrophy (33%). One patient failed at 5.9 years postoperatively and underwent patellofemoral arthroplasty.
Conclusion:
Combined ACI and AMZ resulted in significant improvements in symptoms and function with a low incidence of adverse events in patients with isolated symptomatic patellar chondral defects after a mean follow-up of more than 7 years.
Long experience and recent evidence suggest that trochleoplasty is needed in very few patella stabilization surgeries. As trochleoplasty adds risk, this author recommends it only in patients with ...high degrees of dysplasia, prominent supratrochlear spurs, ligamentous laxity, and more dramatic J signs.
The aim of this study is to determine a relationship between zinc mineralization and a major fault in the Behabad area, central Iran, using the Concentration-Distance to Major Fault (C-DMF), Area of ...Mineralized Zone-Distance to Major Fault (AMZ-DMF), and Concentration-Area (C-A) fractal models for Zn deposit/mine classification according to their distance from the Behabad fault. Application of the C-DMF and the AMZ-DMF models for Zn mineralization classification in the Behabad fault zone reveals that the main Zn deposits have a good correlation with the major fault in the area. The distance from the known zinc deposits/mines with Zn values higher than 29% and the area of the mineralized zone of more than 900 m2 to the major fault is lower than 1 km, which shows a positive correlation between Zn mineralization and the structural zone. As a result, the AMZ-DMF and C-DMF fractal models can be utilized for the delineation and the recognition of different mineralized zones in different types of magmatic and hydrothermal deposits.
•Relationship between fault and MVT deposits by fractal modelling.•Classification MVT deposits using C-A, C-DMF and AMZ-DMF fractal models.•Fractal modeling based on distance of major fault and ore grades.
ABSTRACT
In this paper, three approaches were investigated for preparing alumina‐mullite‐zirconia (AMZ) composites. The weight ratio of alumina to zircon was selected to be 85/15. In the first ...approach, common well‐known reaction sintering or solid‐state mixing of alumina and zircon were used. In the second approach, suspensions of the raw materials were prepared to examine the effect of wet processing method. The third approach was based on the use of aluminum alkoxide coated zircon and alumina. The sintering of samples was carried out at the temperature of 1630°C for 3 hours. Phase composition and Rietveld refinement method, microstructural observation, EDS analysis, as well as physical and mechanical properties were used and determined to characterize the sintered samples. The results showed that aluminum alkoxide coating can develop the mentioned reaction sintering and mullite formation. However, the desired mechanical properties were not obtained. Wet processing approach resulted in more interesting data about the formation of mullite and could improve the microstructure homogeneity of final composites. Higher amount of tetragonal zirconia, good densification, high hardness, and fine microstructure were obtained by the wet approach. These interesting results were attributed to the fine discrete particles provided by mutual attraction in the wet preparation method.
An Al
2O
3–ZrO
2–SiO
2 system refractory with alumina–mullite–zirconia structure (AMZ) has been laser-melted to improve its surface density and to modify its microstructure in this study. ...Investigations into the laser-melted samples showed that laser scanning velocity had a significant influence on the surface morphology, the microstructure and the phase constituents of the laser-treated zones when other laser parameters were kept constant. Laser overlapping treatment at 8
mm
s
−1 produced a crack-free, smooth and dense surface on the refractory but melting treatments at a lower scanning velocity of 4
mm
s
−1 and a higher scanning velocity of 12
mm
s
−1 generated obvious cracking surface and rough surface respectively. After laser melting treatment, the microstructure was changed into a fine and dense dendrite structure in the central upper region of the laser-molten zone and a planar structure between the dendrite region and the substrate region; the dominant phases were changed from α-Al
2O
3+Al
6Si
2O
13+m-ZrO
2 to m-ZrO
2+α-Al
2O
3+Al
2.427O
3.64 due to the selected evaporation of constituents SiO
2 and Al
2O
3, and the phase m-ZrO
2 or c-ZrO
2 was uniformly dispersed into the dendrite instead of the nonuniform particle-like shape in the as-received refractory. An increase in scanning velocity resulted in more planar structure region and higher contents of the nonequilibrium phases c-ZrO
2 and Al
2.427O
3.64.
A mathematical model for the description of the detector signal obtained in flow injection asynchronous merging zone technique (FIA-AMZ) is proposed. FIA-AMZ is based on the separate injection of a ...sample and an appropriate reagent in such a way that both injected solutions are covered only partly. The resulted detector signal consists of two consecutive peaks whose heights are proportional to the concentration of the detectable component present in the sample and another component which becomes detectable after the reagent has been added. The detector signals (the concentration profiles of the analytes) are described by a modified Gauss curve, which proved to be better than a combination of Gauss-Lorentz curves. The conversion of undetectable to detectable form of the analyte is described by a sigmoidal function the slope of which corresponds to the frontal dispersion of the added reagent and to the reaction kinetics. The model is tested on the system for the simultaneous spectrophotometric determination Fe
2+ and Fe
3+. It is shown that fitting of the experimental curves with a model function enables the optimisation of the experimental conditions at applied FIA manifold, and consequently the simultaneous determination of concentrations of Fe
2+ and Fe
3+ ions in a single measurement.
