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Suzanne A. Maher - One of the best experts on this subject based on the ideXlab platform.

  • lateral meniscal graft transplantation effect of fixation method on joint Contact Mechanics during simulated gait
    American Journal of Sports Medicine, 2019
    Co-Authors: Caroline Brial, Russell F Warren, Tony Chen, Moira M Mccarthy, Olufunmilayo Adebayo, Hongsheng Wang, Suzanne A. Maher
    Abstract:

    Background:Controversy exists regarding the optimal bony fixation technique for lateral meniscal allografts.Purpose/Hypothesis:The objective was to quantify knee joint Contact Mechanics across the ...

  • dynamic Contact Mechanics on the tibial plateau of the human knee during activities of daily living
    Journal of Biomechanics, 2014
    Co-Authors: Susannah L Gilbert, Russell F Warren, Tony Chen, Ian D Hutchinson, Daniel Choi, Clifford Voigt, Suzanne A. Maher
    Abstract:

    Despite significant advances in scaffold design, manufacture, and development, it remains unclear what forces these scaffolds must withstand when implanted into the heavily loaded environment of the knee joint. The objective of this study was to fully quantify the dynamic Contact Mechanics across the tibial plateau of the human knee joint during gait and stair climbing. Our model consisted of a modified Stanmore knee simulator (to apply multi-directional dynamic forces), a two-camera motion capture system (to record joint kinematics), an electronic sensor (to record Contact stresses on the tibial plateau), and a suite of post-processing algorithms. During gait, peak Contact stresses on the medial plateau occurred in areas of cartilage–cartilage Contact; while during stair climb, peak Contact stresses were located in the posterior aspect of the plateau, under the meniscus. On the lateral plateau, during gait and in early stair-climb, peak Contact stresses occurred under the meniscus, while in late stair-climb, peak Contact stresses were experienced in the zone of cartilage–cartilage Contact. At 45% of the gait cycle, and 20% and 48% of the stair-climb cycle, peak stresses were simultaneously experienced on both the medial and lateral compartment, suggesting that these phases of loading warrant particular consideration in any simulation intended to evaluate scaffold performance. Our study suggests that in order to design a scaffold capable of restoring ‘normal’ Contact Mechanics to the injured knees, the Mechanics of the intended site of implantation should be taken into account in any pre-clinical testing regime.

  • bone plug versus suture only fixation of meniscal grafts effect on joint Contact Mechanics during simulated gait
    American Journal of Sports Medicine, 2014
    Co-Authors: Hongsheng Wang, Russell F Warren, Tony Chen, Albert O Gee, Ian D Hutchinson, Kirsten Stoner, Suzanne A. Maher
    Abstract:

    Background:Meniscus allograft transplantation (MAT) is primarily undertaken to relieve the symptoms associated with meniscal deficiencies. However, its ability to restore normal knee joint Contact Mechanics under physiological loads is still unclear.Purpose:To quantify the dynamic Contact Mechanics associated with 2 commonly used fixation techniques in MAT of the medial compartment: transosseous suture fixation via bone plugs and suture-only fixation at the horns.Study Design:Controlled laboratory study.Methods:Physiological loads to mimic gait were applied across 7 human cadaveric knees on a simulator. A sensor placed on the medial tibial plateau recorded dynamic Contact stresses under the following conditions: (1) intact meniscus, (2) MAT using transosseous suture fixation via bone plugs at the anterior and posterior horns, (3) MAT using suture-only fixation, and (4) total medial meniscectomy. A “remove-replace” procedure was performed to place the same autograft for both MAT conditions to minimize the ...

  • changes in dynamic medial tibiofemoral Contact Mechanics and kinematics after injury of the anterior cruciate ligament a cadaveric model
    Proceedings of the Institution of Mechanical Engineers Part H: Journal of Engineering in Medicine, 2013
    Co-Authors: Asheesh Bedi, Russell F Warren, Tony Chen, Thomas J Santner, Saadiq F Elamin, Natalie H Kelly, Suzanne A. Maher
    Abstract:

    The effects of tears of the anterior cruciate ligament on knee kinematics and Contact Mechanics during dynamic everyday activities, such as gait, remains unclear. The objective of this study was to characterize anterior cruciate ligament-deficient knee Contact Mechanics and kinematics during simulated gait. Nine human cadaveric knees were each augmented with a sensor capable of measuring dynamic normal Contact stresses on the tibial plateau, mounted on a load-controlled simulator, and subjected to physiological, multidirectional, dynamic loads to mimic gait. Using a mixed model with random knee identifiers, confidence intervals were constructed for Contact stress before and after anterior cruciate ligament transection at two points in the gait cycle at which axial force peaked (14% and 45% of the gait cycle). Kinematic and Contact Mechanics changes after anterior cruciate ligament transection were highly variable across knees. Nonetheless, a statistically significant increase in Contact stress in the posterior-central aspect of the medial tibial plateau at 45% of the gait cycle was identified, the location of which corresponds to the location of degenerative changes that are frequently found in patients with chronic anterior cruciate ligament injury. The variability in the Contact stress in other regions of the medial plateau at 45% of the gait cycle was partly explained by the variations in osseous geometry across the nine knees tested. At 14% of gait, there was no significant change in peak Contact stress after anterior cruciate ligament transection in any of the four quadrants, and none of the possible explanatory variables showed statistical significance. Understanding the variable effect of anterior cruciate ligament injury on Contact Mechanics based on geometric differences in osseous anatomy is of paramount clinical importance and may be invaluable to select the best reconstruction techniques and counsel patients on their individual risk of subsequent chondral degeneration.

  • dynamic Contact Mechanics of radial tears of the lateral meniscus implications for treatment
    Arthroscopy, 2012
    Co-Authors: Russell F Warren, Asheesh Bedi, Natalie H Kelly, Michael Baad, Alice J S Fox, Suzanne A. Maher
    Abstract:

    Purpose To characterize the effect of radial tears (RTs) of the lateral meniscus and their subsequent treatment (inside-out repair, partial meniscectomy) on joint Contact Mechanics during simulated gait. Methods Six human cadaveric knees were mounted on a simulator programmed to mimic human gait. A sensor was inserted below the lateral meniscus to measure peak joint Contact pressure location, magnitude, and Contact area. The following conditions were compared: intact meniscus, 30% RT (at the popliteal hiatus), 60% RT, 90% RT, repair, and partial meniscectomy. Data were analyzed in the midstance phase of gait (14% and 45%) when axial force was at its highest (2,100 N). Results Intact knees had peak Contact pressures of 5.9 ± 0.9 MPa and 6.4 ± 1.1 MPa at 14% and 45% of gait, respectively. RTs of up to and including 60% had no effect on pressure magnitude or location. RTs of 90% resulted in significantly increased peak pressure (8.4 ± 1.1 MPa) in the postero-peripheral aspect of the tibial plateau and reduced Contact area versus the intact knee, at 45% of gait. Repair resulted in a significant decrease in peak pressure (7.7 ± 1.0 MPa) relative to 90% RT but had no effect on Contact area. Partial lateral meniscectomy resulted in areas and pressures that were not significantly different from 90% tears (8.7 ± 1.5 MPa). Conclusions Simulated large RTs of the lateral meniscus in the region of the popliteal hiatus show unfavorable dynamic Contact Mechanics that are not significantly different from those resulting from a partial lateral meniscectomy. Pressure was significantly reduced with inside-out repair but was not affected by partial meniscectomy; Contact area was not restored to that of the intact condition for either procedure. Clinical Relevance Large RTs in the region of the popliteal hiatus show unfavorable dynamic Contact Mechanics.

James A Johnson - One of the best experts on this subject based on the ideXlab platform.

  • the effect of radial head hemiarthroplasty geometry on proximal radioulnar joint Contact Mechanics
    Journal of Hand Surgery (European Volume), 2016
    Co-Authors: Daniel G G Langohr, Ryan Willing, Graham J W King, John B Medley, James A Johnson
    Abstract:

    Purpose To compare the joint Contact area and peak Contact stress of different radial head (RH) hemiarthroplasty articular profiles for the proximal radioulnar joint (PRUJ) to the native radial head with the hypothesis that the side radius and side angle closest to the native mating ulnar articular profile would provide the best Contact Mechanics. Methods Finite element models generated from the computed tomography geometry of 14 native elbows (73 ± 17.5 years) were subjected to 12 different RH profiles having varying side radii (flat [r = ∞ mm], 16.25, 8.12, and 4.50 mm) and side angles (0°, 5°, and 10°) under a constant compressive 20-N medial load. Contact areas and peak Contact stresses were computed and compared with the native joint. Results On average, RH implants significantly reduced PRUJ Contact area by 55% ± 16% and increased peak Contact stress by 337% ± 241% compared with the native RH. The prosthesis side radius had significant effects on both Contact area and stress, but side angle did not. The 16.25-mm radii produced the largest Contact areas, and the 4.50-mm radius model generated the smallest Contact areas. As the side radius was decreased, peak Contact stress was reduced as the Contact migrated toward the center of the native ulnar articulation, although the 8.12-mm radius achieved the lowest peak Contact stress. Conclusions Whereas RH hemiarthroplasty side radius can affect both Contact area and peak Contact stress, the magnitude of the effect on Contact area is relatively small compared with that of the peak Contact stress. Furthermore, although a flat RH side profile with a side angle of 5° more closely matched the side profile of the native ulnas used in the present study, the optimal profile was found to be a smaller radius of 8.12 mm. Clinical relevance Optimizing PRUJ Contact Mechanics after metallic RH hemiarthroplasty may contribute to better clinical outcomes by reducing the potential for native cartilage degeneration.

  • Contact Mechanics of reverse total shoulder arthroplasty during abduction the effect of neck shaft angle humeral cup depth and glenosphere diameter
    Journal of Shoulder and Elbow Surgery, 2016
    Co-Authors: Daniel G G Langohr, Ryan Willing, John B Medley, George S Athwal, James A Johnson
    Abstract:

    Background Implant design parameters can be changed during reverse shoulder arthroplasty (RSA) to improve range of motion and stability; however, little is known regarding their impact on articular Contact Mechanics. The purpose of this finite element study was to investigate RSA Contact Mechanics during abduction for different neck-shaft angles, glenosphere sizes, and polyethylene cup depths. Methods Finite element RSA models with varying neck-shaft angles (155°, 145°, 135°), sizes (38 mm, 42 mm), and cup depths (deep, normal, shallow) were loaded with 400 N at physiological abduction angles. The Contact area and maximum Contact stress were computed. Results The Contact patch and the location of maximum Contact stress were typically located inferomedially in the polyethylene cup. On average for all abduction angles investigated, reducing the neck-shaft angle reduced the Contact area by 29% for 155° to 145° and by 59% for 155° to 135° and increased maximum Contact stress by 71% for 155° to 145° and by 286% for 155° to 135°. Increasing the glenosphere size increased the Contact area by 12% but only decreased maximum Contact stress by 2%. Decreasing the cup depth reduced the Contact area by 40% and increased maximum Contact stress by 81%, whereas increasing the depth produced the opposite effect (+52% and –36%, respectively). Discussion The location of the Contact patch and maximum Contact stress in this study matches the area of damage seen frequently on clinical retrievals. This finding suggests that damage to the inferior cup due to notching may be potentiated by Contact stresses. Increasing the glenosphere diameter improved the joint Contact area and did not affect maximum Contact stress. However, although reducing the neck-shaft angle and cup depth can improve range of motion, our study shows that this also has some negative effects on RSA Contact Mechanics, particularly when combined.

  • implications of radial head hemiarthroplasty dish depth on radiocapitellar Contact Mechanics
    Journal of Hand Surgery (European Volume), 2015
    Co-Authors: Elizabeth S Irish, Ryan Willing, Daniel G G Langohr, Graham J W King, James A Johnson
    Abstract:

    Purpose To investigate the effect of radial head implant dish depth on radiocapitellar joint Contact Mechanics. Methods Computed tomography images of 13 fresh-frozen cadaveric humeri were reconstructed into 3-dimensional finite element models with accurate cartilage geometry. Native humeri were paired with the corresponding native radial heads and axisymmetric radial head prosthesis models of the following dish depths: 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, and 3.0 mm. Radiocapitellar Contact Mechanics were quantified at 4 different flexion angles (0°, 45°, 90°, and 135°) with a 100-N axial load applied to the radial head using a modeling protocol previously validated by cadaveric studies. The radial head was permitted to translate freely to its optimal position while the humerus was fully constrained. Output variables were Contact area and peak Contact stress. Results All prostheses had significantly decreased Contact area and increased peak Contact stress at all flexion angles relative to the native radiocapitellar joint. Contact area increased with prosthesis dish depth until reaching a plateau with a predicted local maximum at a mean depth of 3.2 ± 0.7 mm. Peak Contact stress was elevated for both the shallowest and deepest models and reached a predicted local minimum at a mean depth of 1.8 ± 0.3 mm. Conclusions Contact area and peak Contact stress were dependent on radial head prosthesis dish depth. There was an optimal implant dish depth for radiocapitellar Contact Mechanics at approximately 2 mm. Clinical relevance Optimizing radiocapitellar Contact Mechanics using rigorous and systematic prosthesis design techniques may lead to better clinical outcomes due to reduced capitellar cartilage degradation.

  • validation of a finite element model of the human elbow for determining cartilage Contact Mechanics
    Journal of Biomechanics, 2013
    Co-Authors: Ryan Willing, James A Johnson, Emily A Lalone, Hannah L Shannon, Graham J W King
    Abstract:

    It is important to study joint Contact Mechanics to better understand the processes which lead to cartilage degradation. The purpose of this study was to develop and validate a finite element (FE) model of a human elbow capable of predicting joint Contact area and stress. A cylindrical constrained elbow joint loading apparatus was used to measure the cartilage compression and Contact area for a single cadaveric specimen. A computer model of the same joint was created based on computed tomography images of the specimen, and the same loading was simulated using FE Contact analysis. The model-predicted joint compression and Contact area corresponded closely with experiment-measured results (differences of -4.9% and +9.6%). A sensitivity analysis showed that the model results were sensitive to cartilage and bone material properties, as well as the cartilage thickness distribution. The results of this study underline the importance of using accurate material properties and physiological cartilage thickness distributions when simulating cartilage Contact Mechanics.

  • the impact of capitellar arthroplasty on elbow Contact Mechanics implications for implant design
    Clinical Biomechanics, 2011
    Co-Authors: Marlis T Sabo, Hannah L Shannon, James A Johnson, Louis M Ferreira, Graham J W King
    Abstract:

    Abstract Background Radiocapitellar arthroplasty is indicated for capitellar deficiency. Although current implants employ a spherical capitellar surface, the capitellum is elliptical. This has implications for congruency and wear in capitellar arthroplasty. Our objective was to evaluate the Contact Mechanics of radiocapitellar arthroplasty. We hypothesized that capitellar replacement would decrease joint Contact area relative to the native articulation; and an anatomical implant design would replicate more normal Contact morphology than a spherical implant. Methods Eight paired humeri and radii were potted in a custom jig. A compressive load of 85 N was applied with the articulation flexed at 45° in neutral forearm rotation. Joint casts were made and the articular Contact area and shape were quantified. Anatomical and spherical capitellar implants were tested against the native radial head (hemiarthroplasty). Findings The Contact areas for the anatomical and spherical hemiarthroplasties were 59 and 51% of the native articulation ( P P Interpretation Placement of any capitellar implant resulted in a large decrease in Contact area when articulating with a native radial head. This suggests that the radial head cartilage would see a marked increase in Contact pressure relative to the native articulation. The unicompartmental arthroplasties demonstrated an even larger reduction in Contact area, raising concern about accelerated surface wear. Further investigation needs to correlate these Contact Mechanics to cartilage wear and implant longevity.

Graham J W King - One of the best experts on this subject based on the ideXlab platform.

  • the effect of radial head hemiarthroplasty geometry on proximal radioulnar joint Contact Mechanics
    Journal of Hand Surgery (European Volume), 2016
    Co-Authors: Daniel G G Langohr, Ryan Willing, Graham J W King, John B Medley, James A Johnson
    Abstract:

    Purpose To compare the joint Contact area and peak Contact stress of different radial head (RH) hemiarthroplasty articular profiles for the proximal radioulnar joint (PRUJ) to the native radial head with the hypothesis that the side radius and side angle closest to the native mating ulnar articular profile would provide the best Contact Mechanics. Methods Finite element models generated from the computed tomography geometry of 14 native elbows (73 ± 17.5 years) were subjected to 12 different RH profiles having varying side radii (flat [r = ∞ mm], 16.25, 8.12, and 4.50 mm) and side angles (0°, 5°, and 10°) under a constant compressive 20-N medial load. Contact areas and peak Contact stresses were computed and compared with the native joint. Results On average, RH implants significantly reduced PRUJ Contact area by 55% ± 16% and increased peak Contact stress by 337% ± 241% compared with the native RH. The prosthesis side radius had significant effects on both Contact area and stress, but side angle did not. The 16.25-mm radii produced the largest Contact areas, and the 4.50-mm radius model generated the smallest Contact areas. As the side radius was decreased, peak Contact stress was reduced as the Contact migrated toward the center of the native ulnar articulation, although the 8.12-mm radius achieved the lowest peak Contact stress. Conclusions Whereas RH hemiarthroplasty side radius can affect both Contact area and peak Contact stress, the magnitude of the effect on Contact area is relatively small compared with that of the peak Contact stress. Furthermore, although a flat RH side profile with a side angle of 5° more closely matched the side profile of the native ulnas used in the present study, the optimal profile was found to be a smaller radius of 8.12 mm. Clinical relevance Optimizing PRUJ Contact Mechanics after metallic RH hemiarthroplasty may contribute to better clinical outcomes by reducing the potential for native cartilage degeneration.

  • implications of radial head hemiarthroplasty dish depth on radiocapitellar Contact Mechanics
    Journal of Hand Surgery (European Volume), 2015
    Co-Authors: Elizabeth S Irish, Ryan Willing, Daniel G G Langohr, Graham J W King, James A Johnson
    Abstract:

    Purpose To investigate the effect of radial head implant dish depth on radiocapitellar joint Contact Mechanics. Methods Computed tomography images of 13 fresh-frozen cadaveric humeri were reconstructed into 3-dimensional finite element models with accurate cartilage geometry. Native humeri were paired with the corresponding native radial heads and axisymmetric radial head prosthesis models of the following dish depths: 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, and 3.0 mm. Radiocapitellar Contact Mechanics were quantified at 4 different flexion angles (0°, 45°, 90°, and 135°) with a 100-N axial load applied to the radial head using a modeling protocol previously validated by cadaveric studies. The radial head was permitted to translate freely to its optimal position while the humerus was fully constrained. Output variables were Contact area and peak Contact stress. Results All prostheses had significantly decreased Contact area and increased peak Contact stress at all flexion angles relative to the native radiocapitellar joint. Contact area increased with prosthesis dish depth until reaching a plateau with a predicted local maximum at a mean depth of 3.2 ± 0.7 mm. Peak Contact stress was elevated for both the shallowest and deepest models and reached a predicted local minimum at a mean depth of 1.8 ± 0.3 mm. Conclusions Contact area and peak Contact stress were dependent on radial head prosthesis dish depth. There was an optimal implant dish depth for radiocapitellar Contact Mechanics at approximately 2 mm. Clinical relevance Optimizing radiocapitellar Contact Mechanics using rigorous and systematic prosthesis design techniques may lead to better clinical outcomes due to reduced capitellar cartilage degradation.

  • validation of a finite element model of the human elbow for determining cartilage Contact Mechanics
    Journal of Biomechanics, 2013
    Co-Authors: Ryan Willing, James A Johnson, Emily A Lalone, Hannah L Shannon, Graham J W King
    Abstract:

    It is important to study joint Contact Mechanics to better understand the processes which lead to cartilage degradation. The purpose of this study was to develop and validate a finite element (FE) model of a human elbow capable of predicting joint Contact area and stress. A cylindrical constrained elbow joint loading apparatus was used to measure the cartilage compression and Contact area for a single cadaveric specimen. A computer model of the same joint was created based on computed tomography images of the specimen, and the same loading was simulated using FE Contact analysis. The model-predicted joint compression and Contact area corresponded closely with experiment-measured results (differences of -4.9% and +9.6%). A sensitivity analysis showed that the model results were sensitive to cartilage and bone material properties, as well as the cartilage thickness distribution. The results of this study underline the importance of using accurate material properties and physiological cartilage thickness distributions when simulating cartilage Contact Mechanics.

  • the impact of capitellar arthroplasty on elbow Contact Mechanics implications for implant design
    Clinical Biomechanics, 2011
    Co-Authors: Marlis T Sabo, Hannah L Shannon, James A Johnson, Louis M Ferreira, Graham J W King
    Abstract:

    Abstract Background Radiocapitellar arthroplasty is indicated for capitellar deficiency. Although current implants employ a spherical capitellar surface, the capitellum is elliptical. This has implications for congruency and wear in capitellar arthroplasty. Our objective was to evaluate the Contact Mechanics of radiocapitellar arthroplasty. We hypothesized that capitellar replacement would decrease joint Contact area relative to the native articulation; and an anatomical implant design would replicate more normal Contact morphology than a spherical implant. Methods Eight paired humeri and radii were potted in a custom jig. A compressive load of 85 N was applied with the articulation flexed at 45° in neutral forearm rotation. Joint casts were made and the articular Contact area and shape were quantified. Anatomical and spherical capitellar implants were tested against the native radial head (hemiarthroplasty). Findings The Contact areas for the anatomical and spherical hemiarthroplasties were 59 and 51% of the native articulation ( P P Interpretation Placement of any capitellar implant resulted in a large decrease in Contact area when articulating with a native radial head. This suggests that the radial head cartilage would see a marked increase in Contact pressure relative to the native articulation. The unicompartmental arthroplasties demonstrated an even larger reduction in Contact area, raising concern about accelerated surface wear. Further investigation needs to correlate these Contact Mechanics to cartilage wear and implant longevity.

Ryan Willing - One of the best experts on this subject based on the ideXlab platform.

  • design optimisation of patient specific distal humeral hemiarthroplasty implants for natural Contact Mechanics
    Orthopaedic Proceedings, 2018
    Co-Authors: Ryan Willing
    Abstract:

    IntroductionHemiarthroplasty is a treatment option for comminuted fractures and non-unions of the distal humerus. Unfortunately, the poor anatomical fit of off-the-shelf distal humeral hemiarthroplasty (DHH) implants can cause altered cartilage Contact Mechanics. The result is reduced Contact area and higher cartilage stresses, thus subsequent cartilage erosion a concern. Previous studies have investigated reverse-engineered DHH implants which reproduce the shape of the distal humerus bone or cartilage at the articulation, but still failed to match native Contact Mechanics. In this study, design optimization was used to determine the optimal DHH implant shape. We hypothesized that patient-specific optimal implants will outperform population-optimized designs, and both will optimize simple reverse-engineered designs.MethodsThe boney geometries of six elbow joints were created based on cadaver arm CT data using a semi-automatic threshold technique in 3D Slicer. CT scans were also obtained with the elbows de...

  • the effect of radial head hemiarthroplasty geometry on proximal radioulnar joint Contact Mechanics
    Journal of Hand Surgery (European Volume), 2016
    Co-Authors: Daniel G G Langohr, Ryan Willing, Graham J W King, John B Medley, James A Johnson
    Abstract:

    Purpose To compare the joint Contact area and peak Contact stress of different radial head (RH) hemiarthroplasty articular profiles for the proximal radioulnar joint (PRUJ) to the native radial head with the hypothesis that the side radius and side angle closest to the native mating ulnar articular profile would provide the best Contact Mechanics. Methods Finite element models generated from the computed tomography geometry of 14 native elbows (73 ± 17.5 years) were subjected to 12 different RH profiles having varying side radii (flat [r = ∞ mm], 16.25, 8.12, and 4.50 mm) and side angles (0°, 5°, and 10°) under a constant compressive 20-N medial load. Contact areas and peak Contact stresses were computed and compared with the native joint. Results On average, RH implants significantly reduced PRUJ Contact area by 55% ± 16% and increased peak Contact stress by 337% ± 241% compared with the native RH. The prosthesis side radius had significant effects on both Contact area and stress, but side angle did not. The 16.25-mm radii produced the largest Contact areas, and the 4.50-mm radius model generated the smallest Contact areas. As the side radius was decreased, peak Contact stress was reduced as the Contact migrated toward the center of the native ulnar articulation, although the 8.12-mm radius achieved the lowest peak Contact stress. Conclusions Whereas RH hemiarthroplasty side radius can affect both Contact area and peak Contact stress, the magnitude of the effect on Contact area is relatively small compared with that of the peak Contact stress. Furthermore, although a flat RH side profile with a side angle of 5° more closely matched the side profile of the native ulnas used in the present study, the optimal profile was found to be a smaller radius of 8.12 mm. Clinical relevance Optimizing PRUJ Contact Mechanics after metallic RH hemiarthroplasty may contribute to better clinical outcomes by reducing the potential for native cartilage degeneration.

  • Contact Mechanics of reverse total shoulder arthroplasty during abduction the effect of neck shaft angle humeral cup depth and glenosphere diameter
    Journal of Shoulder and Elbow Surgery, 2016
    Co-Authors: Daniel G G Langohr, Ryan Willing, John B Medley, George S Athwal, James A Johnson
    Abstract:

    Background Implant design parameters can be changed during reverse shoulder arthroplasty (RSA) to improve range of motion and stability; however, little is known regarding their impact on articular Contact Mechanics. The purpose of this finite element study was to investigate RSA Contact Mechanics during abduction for different neck-shaft angles, glenosphere sizes, and polyethylene cup depths. Methods Finite element RSA models with varying neck-shaft angles (155°, 145°, 135°), sizes (38 mm, 42 mm), and cup depths (deep, normal, shallow) were loaded with 400 N at physiological abduction angles. The Contact area and maximum Contact stress were computed. Results The Contact patch and the location of maximum Contact stress were typically located inferomedially in the polyethylene cup. On average for all abduction angles investigated, reducing the neck-shaft angle reduced the Contact area by 29% for 155° to 145° and by 59% for 155° to 135° and increased maximum Contact stress by 71% for 155° to 145° and by 286% for 155° to 135°. Increasing the glenosphere size increased the Contact area by 12% but only decreased maximum Contact stress by 2%. Decreasing the cup depth reduced the Contact area by 40% and increased maximum Contact stress by 81%, whereas increasing the depth produced the opposite effect (+52% and –36%, respectively). Discussion The location of the Contact patch and maximum Contact stress in this study matches the area of damage seen frequently on clinical retrievals. This finding suggests that damage to the inferior cup due to notching may be potentiated by Contact stresses. Increasing the glenosphere diameter improved the joint Contact area and did not affect maximum Contact stress. However, although reducing the neck-shaft angle and cup depth can improve range of motion, our study shows that this also has some negative effects on RSA Contact Mechanics, particularly when combined.

  • implications of radial head hemiarthroplasty dish depth on radiocapitellar Contact Mechanics
    Journal of Hand Surgery (European Volume), 2015
    Co-Authors: Elizabeth S Irish, Ryan Willing, Daniel G G Langohr, Graham J W King, James A Johnson
    Abstract:

    Purpose To investigate the effect of radial head implant dish depth on radiocapitellar joint Contact Mechanics. Methods Computed tomography images of 13 fresh-frozen cadaveric humeri were reconstructed into 3-dimensional finite element models with accurate cartilage geometry. Native humeri were paired with the corresponding native radial heads and axisymmetric radial head prosthesis models of the following dish depths: 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, and 3.0 mm. Radiocapitellar Contact Mechanics were quantified at 4 different flexion angles (0°, 45°, 90°, and 135°) with a 100-N axial load applied to the radial head using a modeling protocol previously validated by cadaveric studies. The radial head was permitted to translate freely to its optimal position while the humerus was fully constrained. Output variables were Contact area and peak Contact stress. Results All prostheses had significantly decreased Contact area and increased peak Contact stress at all flexion angles relative to the native radiocapitellar joint. Contact area increased with prosthesis dish depth until reaching a plateau with a predicted local maximum at a mean depth of 3.2 ± 0.7 mm. Peak Contact stress was elevated for both the shallowest and deepest models and reached a predicted local minimum at a mean depth of 1.8 ± 0.3 mm. Conclusions Contact area and peak Contact stress were dependent on radial head prosthesis dish depth. There was an optimal implant dish depth for radiocapitellar Contact Mechanics at approximately 2 mm. Clinical relevance Optimizing radiocapitellar Contact Mechanics using rigorous and systematic prosthesis design techniques may lead to better clinical outcomes due to reduced capitellar cartilage degradation.

  • validation of a finite element model of the human elbow for determining cartilage Contact Mechanics
    Journal of Biomechanics, 2013
    Co-Authors: Ryan Willing, James A Johnson, Emily A Lalone, Hannah L Shannon, Graham J W King
    Abstract:

    It is important to study joint Contact Mechanics to better understand the processes which lead to cartilage degradation. The purpose of this study was to develop and validate a finite element (FE) model of a human elbow capable of predicting joint Contact area and stress. A cylindrical constrained elbow joint loading apparatus was used to measure the cartilage compression and Contact area for a single cadaveric specimen. A computer model of the same joint was created based on computed tomography images of the specimen, and the same loading was simulated using FE Contact analysis. The model-predicted joint compression and Contact area corresponded closely with experiment-measured results (differences of -4.9% and +9.6%). A sensitivity analysis showed that the model results were sensitive to cartilage and bone material properties, as well as the cartilage thickness distribution. The results of this study underline the importance of using accurate material properties and physiological cartilage thickness distributions when simulating cartilage Contact Mechanics.

Young Jae Kim - One of the best experts on this subject based on the ideXlab platform.

  • tibiofemoral Contact Mechanics following posterior root of medial meniscus tear repair meniscectomy and allograft transplantation
    Knee Surgery Sports Traumatology Arthroscopy, 2013
    Co-Authors: Jin Goo Kim, Yong Seuk Lee, Tae Soo Bae, Donghoon Lee, Young Jae Kim
    Abstract:

    PURPOSE The purposes of this study were to evaluate the effect on tibiofemoral Contact Mechanics of repair of the posterior root of the medial meniscus and the effect of meniscal allograft transplantation (MAT) with medial collateral ligament (MCL) release at different flexion angles. METHODS Ten fresh-frozen human cadaveric knees (five pairs) were used. A digital pressure sensor was inserted by capsulotomy, and experiments were performed serially under the following six conditions, that is, with an intact medial meniscus (normal controls), with a root tear, after root repair, after total meniscectomy, after MAT, and after MAT plus MCL release. During each experiment, knees were positioned at 0°, 30°, 60°, and 90° of flexion, and peak pressure (kPa) and Contact area (cm2) were measured. RESULTS At 0° of flexion, Contact pressure did not differ among the six experimental settings. However, at 30° and 60° of flexion, Contact pressure differed significantly between root tear and root repair specimens (p = 0.04 and 0.03, respectively), and between total meniscectomy and MAT specimens (p = 0.02 and 0.03, respectively). On the other hand, mean Contact pressures were different between normal (476.7 ± 473.1 and 573.3 ± 479.1 kPa) and root repair (575.7 ± 357.8 and 598.6 ± 415.8), and between normal and MAT (635.7 ± 437.4 and 674.3 ± 533.2). At 0°, 30°, 60°, and 90° of flexion, Contact areas differed significantly between normal and total meniscectomy specimens (p = 0.02, 0.01, 0.02, and 0.02, respectively), and between MAT and total meniscectomy specimens (p = 0.03, 0.02, 0.02, and 0.03, respectively). Contact areas differed significantly between root tear and root repair specimens at 60° of flexion (p = 0.04), and between normal control and root repair specimens at 60° and 90° of flexion (p = 0.03 and 0.04, respectively). The effects of MAT plus MCL release on Contact Mechanics were not different from the effects of MAT alone (n.s.). CONCLUSIONS Both meniscal root repair and transplantation of meniscus improved Contact Mechanics, but it did not appear that repair of the meniscal root or transplantation of meniscus restores the biomechanical function back to normal level. The MAT plus MCL release was similar to those after MAT alone. Therefore, it is better to preserve meniscus and MCL release could be done during the MAT.

  • tibiofemoral Contact Mechanics following posterior root of medial meniscus tear repair meniscectomy and allograft transplantation
    Knee Surgery Sports Traumatology Arthroscopy, 2013
    Co-Authors: Jin Goo Kim, Yong Seuk Lee, Tae Soo Bae, Donghoon Lee, Young Jae Kim
    Abstract:

    The purposes of this study were to evaluate the effect on tibiofemoral Contact Mechanics of repair of the posterior root of the medial meniscus and the effect of meniscal allograft transplantation (MAT) with medial collateral ligament (MCL) release at different flexion angles. Ten fresh-frozen human cadaveric knees (five pairs) were used. A digital pressure sensor was inserted by capsulotomy, and experiments were performed serially under the following six conditions, that is, with an intact medial meniscus (normal controls), with a root tear, after root repair, after total meniscectomy, after MAT, and after MAT plus MCL release. During each experiment, knees were positioned at 0°, 30°, 60°, and 90° of flexion, and peak pressure (kPa) and Contact area (cm2) were measured. At 0° of flexion, Contact pressure did not differ among the six experimental settings. However, at 30° and 60° of flexion, Contact pressure differed significantly between root tear and root repair specimens (p = 0.04 and 0.03, respectively), and between total meniscectomy and MAT specimens (p = 0.02 and 0.03, respectively). On the other hand, mean Contact pressures were different between normal (476.7 ± 473.1 and 573.3 ± 479.1 kPa) and root repair (575.7 ± 357.8 and 598.6 ± 415.8), and between normal and MAT (635.7 ± 437.4 and 674.3 ± 533.2). At 0°, 30°, 60°, and 90° of flexion, Contact areas differed significantly between normal and total meniscectomy specimens (p = 0.02, 0.01, 0.02, and 0.02, respectively), and between MAT and total meniscectomy specimens (p = 0.03, 0.02, 0.02, and 0.03, respectively). Contact areas differed significantly between root tear and root repair specimens at 60° of flexion (p = 0.04), and between normal control and root repair specimens at 60° and 90° of flexion (p = 0.03 and 0.04, respectively). The effects of MAT plus MCL release on Contact Mechanics were not different from the effects of MAT alone (n.s.). Both meniscal root repair and transplantation of meniscus improved Contact Mechanics, but it did not appear that repair of the meniscal root or transplantation of meniscus restores the biomechanical function back to normal level. The MAT plus MCL release was similar to those after MAT alone. Therefore, it is better to preserve meniscus and MCL release could be done during the MAT.