Jorge villafuerte - Academia.edu (original) (raw)
Papers by Jorge villafuerte
Ceramic Transactions Series, 2009
ABSTRACT
Journal of Arthroscopy and Joint Surgery, 2019
Background: A trend toward improved perioperative outcomes with direct anterior approach total hi... more Background: A trend toward improved perioperative outcomes with direct anterior approach total hip arthroplasty (DAA THA) in comparison to posterior approach THA has been described. The benefits of the DAA THA have not been examined in the Veteran's Affairs (VA), a health system unique in its highly comorbid patient demographic and federally subsidized budget. Optimizing outcomes in this population could help reduce costs, readmissions, and complications. This study sought to compare the perioperative and radiographic outcomes of veterans who underwent a DAA THA versus a posterior approach THA. Methods: We retrospectively reviewed the records of 110 primary posterior approach THAs and 93 primary DAA THAs performed for primary osteoarthritis by a single surgeon at a VA hospital between 2012 and 2018. We compared mean surgical duration, intraoperative blood loss, perioperative blood transfusion requirements, discharge disposition, hospital length of stay, as well as acetabular component inclination, femoral offset discrepancy, and leg length discrepancy using postoperative anteroposterior pelvis radiographs. Results: The DAA group demonstrated significantly lower perioperative blood transfusion rates (5% vs. 20%), increased likelihood of discharge prior to postoperative day three (OR 2.12; 95% CI 1.02e4.44), and higher rate of discharge to home (65% vs. 40%). Acceptable acetabular inclination rate was higher in the DAA group (83% vs. 37%). Conclusion: Among veterans undergoing primary THA at a VA hospital, patients undergoing DAA THA had better perioperative outcomes than patients treated with the posterior approach despite similar demographics, American Society of Anesthesiologists score, and the DAA learning curve.
Shockwave Induced Spraying (SISP) is a new solid-state spraying process for deposition of metals,... more Shockwave Induced Spraying (SISP) is a new solid-state spraying process for deposition of metals, alloys, cermets and polymers on virtually any type of substrate at lower temperatures than used in traditional thermal spray processes and with high deposition efficiencies and rates. In thermal spray processes such as High Velocity Oxy-Fuel (HVOF) and plasma spraying, bonding is obtained by the combination of thermal and kinetic energy of the sprayed particles. In such thermal spray processes, the thermal energy input, which typically involves melting of the feedstock material, is sufficient to produce undesirable oxidation, porosity, metallurgical transformations and residual stresses. Similar to Cold Gas Dynamic Spraying (or Cold Spray), SISP can produce thick coatings onto a diversity of surfaces at reduced temperature, minimizing thermal effects such as oxidation, tensile residual stresses, and metallurgical transformations. This innovative process can be used to enhance surfaces f...
Low Pressure Cold Spray (LPCS) was used to produce Al based powder coatings on AA2024-T3 Alclad A... more Low Pressure Cold Spray (LPCS) was used to produce Al based powder coatings on AA2024-T3 Alclad Aluminium alloy and AZ31 Magnesium alloy substrates. The corrosion protection provided by these coatings was evaluated by electrochemical measurements (polarization curves, electrochemical impedance spectroscopy) in 1M NaCl electrolyte. The microstructures and electrochemical behavior of the Al based coatings were investigated comparing with pure Al. Electrochemical measurements showed that cold sprayed Al-Al2O3 coatings exhibit: (i) corrosion potential of the Al coating is similar to solid Al, (ii) corrosion potential of the Al-Al2O3 coatings is comparable as Al, and (iii) change of polarization processes occurs for Al-Al2O3 coatings. The immersion tests revealed dependence of corrosion resistance on Al2O3 content. The electrochemical corrosion mechanisms of the coatings and microstructure were discussed. The coatings show a typical layered cold sprayed material structure.
Orthopedics, 2008
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The Journal of Arthroplasty, 2014
Unexpected positive intraoperative cultures (UPIC) in presumed aseptic revision arthroplasty can ... more Unexpected positive intraoperative cultures (UPIC) in presumed aseptic revision arthroplasty can be difficult to interpret. The purpose of this retrospective study was to compare the incidence of subsequent periprosthetic joint infection (PJI) in patients who received antibiotic therapy according to an institutional protocol with those who did not and whether they meet Musculoskeletal Infection Society (MSIS) criteria for PJI. In patients who were treated with antibiotic according to institutional criteria, the incidence of PJI after revision was higher in those who did not meet MSIS criteria (22%) than in those that met MSIS criteria (14%; P N 0.71). UPIC in aseptic revision arthroplasty are not uncommon. PJI cannot be excluded in patients that do not meet MSIS definition.
Aluminum particles were successfully sprayed on wrought magnesium AZ31B extrusion using the cold ... more Aluminum particles were successfully sprayed on wrought magnesium AZ31B extrusion using the cold spray technology. Cold spray high impact velocity of particles colliding with the substrate induced beneficial compressive residual stresses. Magnitude of the residual stress at the surface and its distribution through the thickness were measured using X-ray diffraction. With particle spraying velocity of 400 m/s, the residual stress was measured to be À25 MPa at the surface. The process of collision and development of residual stress was then modeled using LS-DYNA software to study the effect of the cold spray process parameters on the residual stress profile. Various models were employed to simulate the impact of the single and multiple particles. An asymmetric material model that considers the strain rate effect was employed to model AZ31B different behavior in tension and compression. Results of simulations for impact of multiple particles were compared with the results of XRD measurements on the substrate surface and through the depth of the substrate. After the validation of the models, a parametric study was performed on the impact of a single particle to find the optimum cold spray particle velocity, size, shape, incident angle, and friction parameters. Parameters leading to the optimum residual stress profile are introduced herein.
Key Engineering Materials, 1992
... w ix / v \t*s**i ¡*¡i. .~^ * Copyright Trans Tech Publications, Switzerland PHASE TRANSFORMAT... more ... w ix / v \t*s**i ¡*¡i. .~^ * Copyright Trans Tech Publications, Switzerland PHASE TRANSFORMATIONS IN STAINLESS STEEL WELD METAL AND HEAT-AFFECTED ZONES JC Villafuerte and HW Kerr Department of Mechanical Engineering, University of Waterloo ...
Metallurgical Transactions A, 1990
The columnar-equiaxed transition (CET) was investigated in full penetration gas-tungsten arc (GTA... more The columnar-equiaxed transition (CET) was investigated in full penetration gas-tungsten arc (GTA) welds on ferritic stainless steel plates containing different amounts of minor elements, such as titanium and aluminum, for a range of welding conditions. In general, the fraction of equiaxed grains increased, and the size of the equiaxed grains decreased with increasing titanium contents above 0.18 wt pct. At a given level of titanium, the equiaxed fraction increased, and the size of the equiaxed grains decreased with increased aluminum content. The CET was ascribed to heterogeneous nucleation of ferrite on Ti-rich cuboidal inclusions, since these inclusions were observed at the origin of equiaxed dendrites in the grain refined welds. Titanium-rich cuboidal inclusions, in turn, were found to contain A1-Ca-Mg-rich inclusions at their centers, consistent with observations by previous investigators for other processes. The welding conditions, in particular, the welding speed, were observed to affect the occurrence of the CET. Increasing the welding speed from 3 to 8 mm/s increased the equiaxed fraction noticeably, but a further increase in speed to 14 mm/s had a smaller additional effect. A finite element model (FEM) of heat transfer was used to examine the role of the welding conditions on the local solidification conditions along the weld pool edge. The results are compared with existing models for the CET.
Metallurgical Transactions A, 1990
The grain structures were investigated in full penetration gas tungsten-arc (GTA) welds in sheets... more The grain structures were investigated in full penetration gas tungsten-arc (GTA) welds in sheets of 304 and 321 austenitic stainless steels for a range of welding conditions. In type 321 steel welds, fine equiaxed ferrite dendrites were observed in the ferrite phase. The equiaxed structure was ascribed to heterogeneous nucleation of ferrite on Ti-rich cuboidal inclusions present in this steel, since these inclusions were observed at the origin of equiaxed dendrites. In type 304 welds, the ferrite grains were columnar, except in less complete penetration specimens, where a few coarse equiaxed dendrites appeared to originate from the weld surface. The secondary austenitic grain structure was columnar in both steels. In type 304 steel, the columnar austenitic grain structure did not necessarily correspond to the primary ferrite grains. In type 321 steel, the secondary austenite was columnar despite the equiaxed structure of the primary ferrite. Factors which affect the columnar-to-equiaxed transition (CET) are discussed. The failure to form equiaxed austenitic grains in type 321 steel is ascribed to austenite growing across the space between ferrite grains instead of renucleating on the primary equiaxed ferrite.
Materials Science and Engineering: A, 1995
Mechanisms of providing nuclei for equiaxed grains in gas tungsten arc welds in ferritic stainles... more Mechanisms of providing nuclei for equiaxed grains in gas tungsten arc welds in ferritic stainless steel were examined. Tinquenching of the solid-liquid interface revealed that TiN particles in commercial steels could act as heterogeneous nucleation sites. Direct additions of TiN also promoted an equiaxed region. However, no evidence for equiaxed grain formation by dendrite fragmentation was observed, despite the fact that titanium additions did produce a more branched dendritic structure.
Journal of Thermal Spray Technology, 2006
A computational fluid dynamic (CFD) model of the cold gas dynamic spray process is presented. The... more A computational fluid dynamic (CFD) model of the cold gas dynamic spray process is presented. The gas dynamic flow field and particle trajectories within an oval-shaped supersonic nozzle as well as in the immediate surroundings of the nozzle exit, before and after the impact with the target plane, are simulated. Predicted nozzle wall pressure values compare well with experimental data. In addition, predicted particle velocity results at the nozzle exit are in qualitative agreement with those obtained using a side-scatter laser Doppler anemometer (LDA). Details of the pattern of the particle release into the surroundings are visualized in a convenient manner.
The Journal of Hand Surgery, 2006
Purpose: To evaluate survival characteristics of malignant hand tumors compared with those occurr... more Purpose: To evaluate survival characteristics of malignant hand tumors compared with those occurring in other musculoskeletal locations over a 30-year period. Methods: Patients were identified through a computerized database maintained at the authors' institution over the past 30 years. Each patient's records were reviewed retrospectively. Diagnoses were categorized and survival data for patients with hand malignancies were compared with those of patients having similar tumors in other musculoskeletal sites by using multivariate statistical analysis. Results: The most common malignancies were epitheloid sarcoma, synovial sarcoma, and malignant fibrous histiocytoma. Improved survival during the follow-up period was found for hand malignancies versus those occurring in other musculoskeletal sites as a whole, and this difference was statistically significant. No significant survival benefit was identified for individual tumors. Conclusions: Patients presenting with primary malignancies of the hand may survive longer than those with similar tumors in other musculoskeletal locations (
Journal of Clinical Oncology, 2005
Purpose We have reviewed a series of 150 aneurysmal bone cysts treated over the last 20 years. Pa... more Purpose We have reviewed a series of 150 aneurysmal bone cysts treated over the last 20 years. Patients and Methods The lesions were principally located in the tibia, femur, pelvis, humerus, and spine and, in most cases, presented the imaging appearance originally described by Jaffe and Lichtenstein as a blowout with thin cortices. Results Only one of the patients was believed to have an osteoblastoma of the spine with secondary development of an aneurysmal bone cyst, and none of the patients developed additional lesions. The patients were treated primarily with curettage and implantation of allograft chips or polymethylmethacrylate, but some patients were treated with insertion of autografts or allografts. The local recurrence rate was 20%, which is consistent with that reported by other centers. Conclusion Aneurysmal bone cysts are enigmatic lesions of unknown cause and presentation and are difficult to distinguish from other lesions. Overall, the treatment is satisfactory, but it...
The Journal of Arthroplasty, 2014
orthojournalhms.org
DISCUSSION Giant cell tumor (GCT) is a rare, benign, but locally invasive and highly destructive ... more DISCUSSION Giant cell tumor (GCT) is a rare, benign, but locally invasive and highly destructive tumor that comprises only 4% to 5% of all primary bone tumors in the United States. The percentage rises to approximately 20% of all primary bone tumors in ...
Clinical Orthopaedics and Related Research, 2003
Ali et al Copyr ight © Lippincott Williams & Wilkins. Unauthorized reproduction of this article i... more Ali et al Copyr ight © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Ceramic Transactions Series, 2009
ABSTRACT
Journal of Arthroscopy and Joint Surgery, 2019
Background: A trend toward improved perioperative outcomes with direct anterior approach total hi... more Background: A trend toward improved perioperative outcomes with direct anterior approach total hip arthroplasty (DAA THA) in comparison to posterior approach THA has been described. The benefits of the DAA THA have not been examined in the Veteran's Affairs (VA), a health system unique in its highly comorbid patient demographic and federally subsidized budget. Optimizing outcomes in this population could help reduce costs, readmissions, and complications. This study sought to compare the perioperative and radiographic outcomes of veterans who underwent a DAA THA versus a posterior approach THA. Methods: We retrospectively reviewed the records of 110 primary posterior approach THAs and 93 primary DAA THAs performed for primary osteoarthritis by a single surgeon at a VA hospital between 2012 and 2018. We compared mean surgical duration, intraoperative blood loss, perioperative blood transfusion requirements, discharge disposition, hospital length of stay, as well as acetabular component inclination, femoral offset discrepancy, and leg length discrepancy using postoperative anteroposterior pelvis radiographs. Results: The DAA group demonstrated significantly lower perioperative blood transfusion rates (5% vs. 20%), increased likelihood of discharge prior to postoperative day three (OR 2.12; 95% CI 1.02e4.44), and higher rate of discharge to home (65% vs. 40%). Acceptable acetabular inclination rate was higher in the DAA group (83% vs. 37%). Conclusion: Among veterans undergoing primary THA at a VA hospital, patients undergoing DAA THA had better perioperative outcomes than patients treated with the posterior approach despite similar demographics, American Society of Anesthesiologists score, and the DAA learning curve.
Shockwave Induced Spraying (SISP) is a new solid-state spraying process for deposition of metals,... more Shockwave Induced Spraying (SISP) is a new solid-state spraying process for deposition of metals, alloys, cermets and polymers on virtually any type of substrate at lower temperatures than used in traditional thermal spray processes and with high deposition efficiencies and rates. In thermal spray processes such as High Velocity Oxy-Fuel (HVOF) and plasma spraying, bonding is obtained by the combination of thermal and kinetic energy of the sprayed particles. In such thermal spray processes, the thermal energy input, which typically involves melting of the feedstock material, is sufficient to produce undesirable oxidation, porosity, metallurgical transformations and residual stresses. Similar to Cold Gas Dynamic Spraying (or Cold Spray), SISP can produce thick coatings onto a diversity of surfaces at reduced temperature, minimizing thermal effects such as oxidation, tensile residual stresses, and metallurgical transformations. This innovative process can be used to enhance surfaces f...
Low Pressure Cold Spray (LPCS) was used to produce Al based powder coatings on AA2024-T3 Alclad A... more Low Pressure Cold Spray (LPCS) was used to produce Al based powder coatings on AA2024-T3 Alclad Aluminium alloy and AZ31 Magnesium alloy substrates. The corrosion protection provided by these coatings was evaluated by electrochemical measurements (polarization curves, electrochemical impedance spectroscopy) in 1M NaCl electrolyte. The microstructures and electrochemical behavior of the Al based coatings were investigated comparing with pure Al. Electrochemical measurements showed that cold sprayed Al-Al2O3 coatings exhibit: (i) corrosion potential of the Al coating is similar to solid Al, (ii) corrosion potential of the Al-Al2O3 coatings is comparable as Al, and (iii) change of polarization processes occurs for Al-Al2O3 coatings. The immersion tests revealed dependence of corrosion resistance on Al2O3 content. The electrochemical corrosion mechanisms of the coatings and microstructure were discussed. The coatings show a typical layered cold sprayed material structure.
Orthopedics, 2008
RefDoc Bienvenue - Welcome. Refdoc est un service / is powered by. ...
The Journal of Arthroplasty, 2014
Unexpected positive intraoperative cultures (UPIC) in presumed aseptic revision arthroplasty can ... more Unexpected positive intraoperative cultures (UPIC) in presumed aseptic revision arthroplasty can be difficult to interpret. The purpose of this retrospective study was to compare the incidence of subsequent periprosthetic joint infection (PJI) in patients who received antibiotic therapy according to an institutional protocol with those who did not and whether they meet Musculoskeletal Infection Society (MSIS) criteria for PJI. In patients who were treated with antibiotic according to institutional criteria, the incidence of PJI after revision was higher in those who did not meet MSIS criteria (22%) than in those that met MSIS criteria (14%; P N 0.71). UPIC in aseptic revision arthroplasty are not uncommon. PJI cannot be excluded in patients that do not meet MSIS definition.
Aluminum particles were successfully sprayed on wrought magnesium AZ31B extrusion using the cold ... more Aluminum particles were successfully sprayed on wrought magnesium AZ31B extrusion using the cold spray technology. Cold spray high impact velocity of particles colliding with the substrate induced beneficial compressive residual stresses. Magnitude of the residual stress at the surface and its distribution through the thickness were measured using X-ray diffraction. With particle spraying velocity of 400 m/s, the residual stress was measured to be À25 MPa at the surface. The process of collision and development of residual stress was then modeled using LS-DYNA software to study the effect of the cold spray process parameters on the residual stress profile. Various models were employed to simulate the impact of the single and multiple particles. An asymmetric material model that considers the strain rate effect was employed to model AZ31B different behavior in tension and compression. Results of simulations for impact of multiple particles were compared with the results of XRD measurements on the substrate surface and through the depth of the substrate. After the validation of the models, a parametric study was performed on the impact of a single particle to find the optimum cold spray particle velocity, size, shape, incident angle, and friction parameters. Parameters leading to the optimum residual stress profile are introduced herein.
Key Engineering Materials, 1992
... w ix / v \t*s**i ¡*¡i. .~^ * Copyright Trans Tech Publications, Switzerland PHASE TRANSFORMAT... more ... w ix / v \t*s**i ¡*¡i. .~^ * Copyright Trans Tech Publications, Switzerland PHASE TRANSFORMATIONS IN STAINLESS STEEL WELD METAL AND HEAT-AFFECTED ZONES JC Villafuerte and HW Kerr Department of Mechanical Engineering, University of Waterloo ...
Metallurgical Transactions A, 1990
The columnar-equiaxed transition (CET) was investigated in full penetration gas-tungsten arc (GTA... more The columnar-equiaxed transition (CET) was investigated in full penetration gas-tungsten arc (GTA) welds on ferritic stainless steel plates containing different amounts of minor elements, such as titanium and aluminum, for a range of welding conditions. In general, the fraction of equiaxed grains increased, and the size of the equiaxed grains decreased with increasing titanium contents above 0.18 wt pct. At a given level of titanium, the equiaxed fraction increased, and the size of the equiaxed grains decreased with increased aluminum content. The CET was ascribed to heterogeneous nucleation of ferrite on Ti-rich cuboidal inclusions, since these inclusions were observed at the origin of equiaxed dendrites in the grain refined welds. Titanium-rich cuboidal inclusions, in turn, were found to contain A1-Ca-Mg-rich inclusions at their centers, consistent with observations by previous investigators for other processes. The welding conditions, in particular, the welding speed, were observed to affect the occurrence of the CET. Increasing the welding speed from 3 to 8 mm/s increased the equiaxed fraction noticeably, but a further increase in speed to 14 mm/s had a smaller additional effect. A finite element model (FEM) of heat transfer was used to examine the role of the welding conditions on the local solidification conditions along the weld pool edge. The results are compared with existing models for the CET.
Metallurgical Transactions A, 1990
The grain structures were investigated in full penetration gas tungsten-arc (GTA) welds in sheets... more The grain structures were investigated in full penetration gas tungsten-arc (GTA) welds in sheets of 304 and 321 austenitic stainless steels for a range of welding conditions. In type 321 steel welds, fine equiaxed ferrite dendrites were observed in the ferrite phase. The equiaxed structure was ascribed to heterogeneous nucleation of ferrite on Ti-rich cuboidal inclusions present in this steel, since these inclusions were observed at the origin of equiaxed dendrites. In type 304 welds, the ferrite grains were columnar, except in less complete penetration specimens, where a few coarse equiaxed dendrites appeared to originate from the weld surface. The secondary austenitic grain structure was columnar in both steels. In type 304 steel, the columnar austenitic grain structure did not necessarily correspond to the primary ferrite grains. In type 321 steel, the secondary austenite was columnar despite the equiaxed structure of the primary ferrite. Factors which affect the columnar-to-equiaxed transition (CET) are discussed. The failure to form equiaxed austenitic grains in type 321 steel is ascribed to austenite growing across the space between ferrite grains instead of renucleating on the primary equiaxed ferrite.
Materials Science and Engineering: A, 1995
Mechanisms of providing nuclei for equiaxed grains in gas tungsten arc welds in ferritic stainles... more Mechanisms of providing nuclei for equiaxed grains in gas tungsten arc welds in ferritic stainless steel were examined. Tinquenching of the solid-liquid interface revealed that TiN particles in commercial steels could act as heterogeneous nucleation sites. Direct additions of TiN also promoted an equiaxed region. However, no evidence for equiaxed grain formation by dendrite fragmentation was observed, despite the fact that titanium additions did produce a more branched dendritic structure.
Journal of Thermal Spray Technology, 2006
A computational fluid dynamic (CFD) model of the cold gas dynamic spray process is presented. The... more A computational fluid dynamic (CFD) model of the cold gas dynamic spray process is presented. The gas dynamic flow field and particle trajectories within an oval-shaped supersonic nozzle as well as in the immediate surroundings of the nozzle exit, before and after the impact with the target plane, are simulated. Predicted nozzle wall pressure values compare well with experimental data. In addition, predicted particle velocity results at the nozzle exit are in qualitative agreement with those obtained using a side-scatter laser Doppler anemometer (LDA). Details of the pattern of the particle release into the surroundings are visualized in a convenient manner.
The Journal of Hand Surgery, 2006
Purpose: To evaluate survival characteristics of malignant hand tumors compared with those occurr... more Purpose: To evaluate survival characteristics of malignant hand tumors compared with those occurring in other musculoskeletal locations over a 30-year period. Methods: Patients were identified through a computerized database maintained at the authors' institution over the past 30 years. Each patient's records were reviewed retrospectively. Diagnoses were categorized and survival data for patients with hand malignancies were compared with those of patients having similar tumors in other musculoskeletal sites by using multivariate statistical analysis. Results: The most common malignancies were epitheloid sarcoma, synovial sarcoma, and malignant fibrous histiocytoma. Improved survival during the follow-up period was found for hand malignancies versus those occurring in other musculoskeletal sites as a whole, and this difference was statistically significant. No significant survival benefit was identified for individual tumors. Conclusions: Patients presenting with primary malignancies of the hand may survive longer than those with similar tumors in other musculoskeletal locations (
Journal of Clinical Oncology, 2005
Purpose We have reviewed a series of 150 aneurysmal bone cysts treated over the last 20 years. Pa... more Purpose We have reviewed a series of 150 aneurysmal bone cysts treated over the last 20 years. Patients and Methods The lesions were principally located in the tibia, femur, pelvis, humerus, and spine and, in most cases, presented the imaging appearance originally described by Jaffe and Lichtenstein as a blowout with thin cortices. Results Only one of the patients was believed to have an osteoblastoma of the spine with secondary development of an aneurysmal bone cyst, and none of the patients developed additional lesions. The patients were treated primarily with curettage and implantation of allograft chips or polymethylmethacrylate, but some patients were treated with insertion of autografts or allografts. The local recurrence rate was 20%, which is consistent with that reported by other centers. Conclusion Aneurysmal bone cysts are enigmatic lesions of unknown cause and presentation and are difficult to distinguish from other lesions. Overall, the treatment is satisfactory, but it...
The Journal of Arthroplasty, 2014
orthojournalhms.org
DISCUSSION Giant cell tumor (GCT) is a rare, benign, but locally invasive and highly destructive ... more DISCUSSION Giant cell tumor (GCT) is a rare, benign, but locally invasive and highly destructive tumor that comprises only 4% to 5% of all primary bone tumors in the United States. The percentage rises to approximately 20% of all primary bone tumors in ...
Clinical Orthopaedics and Related Research, 2003
Ali et al Copyr ight © Lippincott Williams & Wilkins. Unauthorized reproduction of this article i... more Ali et al Copyr ight © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.