James A Johnson

The University of Western Ontario, London, Ontario, Canada

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Publications (148)320.25 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Reverse total shoulder arthroplasty (RTSA) is widely used; however, the effects of RTSA geometric parameters on joint and muscle loading, which strongly influence implant survivorship and long-term function, are not well understood. By investigating these parameters, it should be possible to objectively optimize RTSA design and implantation technique. The purposes of this study were to evaluate the effect of RTSA implant design parameters on (1) the deltoid muscle forces required to produce abduction, and (2) the magnitude of joint load and (3) the loading angle throughout this motion. We also sought to determine how these parameters interacted. Seven cadaveric shoulders were tested using a muscle load-driven in vitro simulator to achieve repeatable motions. The effects of three implant parameters-humeral lateralization (0, 5, 10 mm), polyethylene thickness (3, 6, 9 mm), and glenosphere lateralization (0, 5, 10 mm)-were assessed for the three outcomes: deltoid muscle force required to produce abduction, magnitude of joint load, and joint loading angle throughout abduction. Increasing humeral lateralization decreased deltoid forces required for active abduction (0 mm: 68% ± 8% [95% CI, 60%-76% body weight (BW)]; 10 mm: 65% ± 8% [95% CI, 58%-72 % BW]; p = 0.022). Increasing glenosphere lateralization increased deltoid force (0 mm: 61% ± 8% [95% CI, 55%-68% BW]; 10 mm: 70% ± 11% [95% CI, 60%-81% BW]; p = 0.007) and joint loads (0 mm: 53% ± 8% [95% CI, 46%-61% BW]; 10 mm: 70% ± 10% [95% CI, 61%-79% BW]; p < 0.001). Increasing polyethylene cup thickness increased deltoid force (3 mm: 65% ± 8% [95% CI, 56%-73% BW]; 9 mm: 68% ± 8% [95% CI, 61%-75% BW]; p = 0.03) and joint load (3 mm: 60% ± 8% [95% CI, 53%-67% BW]; 9 mm: 64% ± 10% [95% CI, 56%-72% BW]; p = 0.034). Humeral lateralization was the only parameter that improved joint and muscle loading, whereas glenosphere lateralization resulted in increased loads. Humeral lateralization may be a useful implant parameter in countering some of the negative effects of glenosphere lateralization, but this should not be considered the sole solution for the negative effects of glenosphere lateralization. Overstuffing the articulation with progressively thicker humeral polyethylene inserts produced some adverse effects on deltoid muscle and joint loading. This systematic evaluation has determined that glenosphere lateralization produces marked negative effects on loading outcomes; however, the importance of avoiding scapular notching may outweigh these effects. Humeral lateralization's ability to decrease the effects of glenosphere lateralization was promising but further investigations are required to determine the effects of combined lateralization on functional outcomes including range of motion.
    Clinical Orthopaedics and Related Research 08/2015; DOI:10.1007/s11999-015-4526-0 · 2.88 Impact Factor
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    ABSTRACT: Computed tomography provides high contrast imaging of the joint anatomy and is used routinely to reconstruct 3D models of the osseous and cartilage geometry (CT arthrography) for use in the design of orthopedic implants, for computer assisted surgeries and computational dynamic and structural analysis. The objective of this study was to assess the accuracy of bone and cartilage surface model reconstructions by comparing reconstructed geometries with bone digitizations obtained using an optical tracking system. Bone surface digitizations obtained in this study determined the ground truth measure for the underlying geometry. We evaluated the use of a commercially available reconstruction technique using clinical CT scanning protocols using the elbow joint as an example of a surface with complex geometry. To assess the accuracies of the reconstructed models (8 fresh frozen cadaveric specimens) against the ground truth bony digitization-as defined by this study-proximity mapping was used to calculate residual error. The overall mean error was less than 0.4 mm in the cortical region and 0.3 mm in the subchondral region of the bone. Similarly creating 3D cartilage surface models from CT scans using air contrast had a mean error of less than 0.3 mm. Results from this study indicate that clinical CT scanning protocols and commonly used and commercially available reconstruction algorithms can create models which accurately represent the true geometry. Copyright © 2015 IPEM. Published by Elsevier Ltd. All rights reserved.
    Medical Engineering & Physics 05/2015; DOI:10.1016/j.medengphy.2015.04.010 · 1.84 Impact Factor
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    ABSTRACT: To investigate the effect of radial head implant dish depth on radiocapitellar joint contact mechanics. 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. 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. 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. Optimizing radiocapitellar contact mechanics using rigorous and systematic prosthesis design techniques may lead to better clinical outcomes due to reduced capitellar cartilage degradation. Copyright © 2015 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.
    The Journal of hand surgery 04/2015; 40(4). DOI:10.1016/j.jhsa.2015.01.030 · 1.66 Impact Factor
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    ABSTRACT: To examine the effect of implant shape on radiocapitellar joint contact area and location in vitro. We used 8 fresh-frozen cadaveric upper extremities. An elbow loading simulator examined joint contact in pronation, neutral rotation, and supination with the elbow at 90° flexion. Muscle tendons were attached to pneumatic actuators to allow for computer-controlled loading to achieve the desired forearm rotation. We performed testing with the native radial head, an axisymmetric implant, a reverse-engineered patient-specific implant, and a population-based quasi-anatomic implant. Implants were inserted using computer navigation. Contact area and location were quantified using a casting technique. We found no significant difference between contact locations for the native radial head and the 3 implants. All of the implants had a contact area lower than the native radial head; however, only the axisymmetric implant was significantly different. There was no significant difference in contact area between implant shapes. The similar contact areas and locations of the 3 implant designs suggest that the shape of the implant may not be important with respect to radiocapitellar joint contact mechanics when placed optimally using computer navigation. Further work is needed to explore the sensitivity of radial head implant malpositioning on articular contact. The lower contact area of the radial head implants relative to the native radial head is similar to previous benchtop studies and is likely the result of the greater stiffness of the implant. Radial head implant shape does not appear to have a pronounced influence on articular contact, and both axisymmetric and anatomic metal designs result in elevated cartilage stress relative to the intact state. Copyright © 2015 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.
    The Journal of hand surgery 04/2015; 40(4). DOI:10.1016/j.jhsa.2014.12.017 · 1.66 Impact Factor
  • Journal of Shoulder and Elbow Surgery 04/2015; 24(4):e118. DOI:10.1016/j.jse.2014.11.024 · 2.37 Impact Factor
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    ABSTRACT: Radial head (RH) implants are manufactured from stiff materials, resulting in reduced radiocapitellar contact area that may lead to cartilage degeneration. Although the native RH is nonaxisymmetric, most implants are axisymmetric, potentially contributing to altered contact mechanics. This study compared the joint contact area (Ac) and maximum contact stress (σmax) of axisymmetric and nonaxisymmetric RH implants to the native radiocapitellar joint. The contact mechanics of intact elbows derived from cadaveric computed tomography data (n = 15) were compared with axisymmetric (size: 18, 20, 22 mm) and nonaxisymmetric (size: 16 × 18, 18 × 20, 20 × 22 mm) RH hemiarthroplasty reconstructed elbows using Abaqus finite element software. Under a 100 N load, Ac and σmax were computed for ±90° pronation-supination and 0°, 45°, 90°, and 135° flexion. Compared with native, both hemiarthroplasty models produced significantly lower Ac and higher σmax (P < .001). In the best orientation, the nonaxisymmetric RH provided significantly larger Ac at 0° and 135° flexion (P = .03, P = .007) and reduced levels of σmax at 45° and 90° flexion (P = .003, P < .001). However, there was also a worst orientation that reduced Ac and increased σmax for all flexion angles (P < .003 for all). The native RH was less sensitive to rotation than the nonaxisymmetric RH in terms of σmax (P < .001). The axisymmetric RH was not sensitive to rotation. Whereas a nonaxisymmetric RH can provide improved contact mechanics at certain forearm rotations and flexions, there are also orientations where Ac is reduced and σmax is increased. Axisymmetric designs are more consistent throughout forearm rotation and therefore may be more forgiving than the nonaxisymmetric RH implant design used in this study. Copyright © 2015 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.
    Journal of shoulder and elbow surgery / American Shoulder and Elbow Surgeons ... [et al.] 02/2015; 24(5). DOI:10.1016/j.jse.2014.12.011 · 2.37 Impact Factor
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    ABSTRACT: To quantify the effects of dorsal translation deformities of the distal radius with and without dorsal angulation on volar displacement of the ulnar head during simulated active forearm rotation, both with the triangular fibrocartilage complex (TFCC) intact and sectioned. Eight fresh-frozen cadaveric upper extremities were mounted in an active forearm motion simulator, and distal radial deformities of 0 mm, 5 mm and 10 mm of dorsal translation with 0°, 10°, 20° and 30° of dorsal angulation were simulated. Volar displacement of the ulnar head at the distal radioulnar joint as a result of each distal radial deformity was quantified during simulated active supination. The data were collected with the TFCC intact and following sectioning the TFCC at its ulnar insertion. Increasing isolated dorsal translation deformities increased volar displacement of the ulnar head when the TFCC was intact (P < 0.001). Increasing dorsal translation combined with dorsal angulation increased volar displacement of the ulnar head compared with isolated dorsal angulation deformities (P < 0.001). Sectioning the TFCC increased the volar displacement of the ulnar head caused by each distal radial deformity (P = 0.001). These results emphasize the clinical importance of evaluating the magnitude of both dorsal translation and dorsal angulation when managing displaced distal radius fractures and malunions.
    Journal of Orthopaedic Trauma 01/2015; 29(6). DOI:10.1097/BOT.0000000000000273 · 1.54 Impact Factor
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    ABSTRACT: Little is known about the effects of glenosphere diameter on shoulder joint loads. The purpose of this biomechanical study was to investigate the effects of glenosphere diameter on joint load, load angle, and total deltoid force required for active abduction and range of motion in internal/external rotation and abduction. A custom, instrumented reverse shoulder arthroplasty implant system capable of measuring joint load and varying glenosphere diameter (38 and 42 mm) and glenoid offset (neutral and lateral) was implanted in 6 cadaveric shoulders to provide at least 80% power for all variables. A shoulder motion simulator was used to produce active glenohumeral and scapulothoracic motion. All implant configurations were tested with active and passive motion with joint kinematics, loads, and moments recorded. At neutral and lateralized glenosphere positions, increasing diameter significantly increased joint load (+12 ± 21 N and +6 ± 9 N; P < .01) and deltoid load required for active abduction (+9 ± 22 N and +11 ± 15 N; P < .02), whereas joint load angle was unaffected (P > .8). Passive internal rotation was reduced with increased diameter at both neutral and lateralized glenosphere positions (-6° ± 6° and -12° ± 6°; P < .002); however, external rotation was not affected (P > .05). At neutral glenosphere position, increasing diameter increased the maximum angles of both adduction (+1° ± 1°; P = .03) and abduction (+8° ± 9°; P < .05). Lateralization also increased abduction range of motion compared with neutral (P < .01). Although increasing glenosphere diameter significantly increased joint load and deltoid force, the clinical impact of these changes is presently unclear. Internal rotation, however, was reduced, which contradicts previous bone modeling studies, which we postulate is due to increased posterior capsular tension as it is forced to wrap around a larger 42 mm implant assembly. Copyright © 2014 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.
    Journal of shoulder and elbow surgery / American Shoulder and Elbow Surgeons ... [et al.] 12/2014; 24(6). DOI:10.1016/j.jse.2014.10.018 · 2.37 Impact Factor
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    ABSTRACT: To measure the effects of distal radius malalignment on loading at the distal ulna. Using an adjustable mechanism to simulate angulated and translated malalignments, clinically relevant distal radius deformities were simulated in a cadaveric model. A custom-built load cell was inserted just proximal to the native ulna head to measure the resultant force and torque in the distal ulna. Loads were measured before and after transecting the triangular fibrocartilage complex (TFCC). There was an increase in distal ulna load and torque with increasing dorsal translation and angulation. Combined conditions of angulation and translation increased force and torque in the distal ulna to a greater extent than with either condition in isolation. Transecting the TFCC resulted in a reduction in distal ulna load and torque. A progressive increase in load at the distal ulna was observed with increasing severity of malalignment, which may be an important contributor to residual ulnar wrist pain and dysfunction. However, no clear-cut threshold of malalignment of a dorsally angulated and translated distal radius fracture was identified. These observations suggest that radius deformities cause articular incongruity, which increases TFCC tension and distal radioulnar joint load. Cutting of the TFCC decreased distal ulna loading, likely by releasing the articular constraining effect of the TFCC on the distal radioulnar joint, allowing the radius to rotate more freely with respect to the ulna. Anatomical reduction of a distal radius fracture minimizes the forces in the distal ulna and may reduce residual ulnar wrist pain and dysfunction. Copyright © 2014 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.
    The Journal Of Hand Surgery 12/2014; 40(2). DOI:10.1016/j.jhsa.2014.10.012 · 1.66 Impact Factor
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    ABSTRACT: The strong advent of computer-assisted technologies experienced by the modern orthopedic surgery prompts for the expansion of computationally efficient techniques to be built on the broad base of computer-aided engineering tools that are readily available. However, one of the common challenges faced during the current developmental phase continues to remain the lack of reliable frameworks to allow a fast and precise conversion of the anatomical information acquired through computer tomography to a format that is acceptable to computer-aided engineering software. To address this, this study proposes an integrated and automatic framework capable to extract and then postprocess the original imaging data to a common planar and closed B-Spline representation. The core of the developed platform relies on the approximation of the discrete computer tomography data by means of an original two-step B-Spline fitting technique based on successive deformations of the control polygon. In addition to its rapidity and robustness, the developed fitting technique was validated to produce accurate representations that do not deviate by more than 0.2 mm with respect to alternate representations of the bone geometry that were obtained through different-contact-based-data acquisition or data processing methods. © IMechE 2014.
    Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 12/2014; 228(12):1241-57. DOI:10.1177/0954411914562267 · 1.14 Impact Factor
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    ABSTRACT: A number of radial head implants are in clinical use for the management of radial head fractures and their sequelae. However, the optimal shape of a radial head implant to ensure proper tracking relative to the capitellum has not been established. This in vitro biomechanical study compared radiocapitellar joint kinematics for 3 radial head implant designs as well as the native head. Eight cadaveric upper extremities were tested using a forearm rotation simulator with the elbow at 90° of flexion. Motion of the radius relative to the capitellum was optically tracked. A stem was navigated into a predetermined location and cemented in place. Three unipolar implant shapes were tested: axisymmetric, reverse-engineered patient-specific, and population-based quasi-anatomic. The patient-specific and quasi-anatomic implants were derived from measurements performed on computed tomography models. Medial-lateral and anterior-posterior translation of the radial head with respect to the capitellum varied with forearm rotation and radial head condition. A significant difference in medial-lateral (P = .03) and anterior-posterior (P = .03) translation was found between the native radial head and the 3 implants. No differences were observed among the radial head conditions except for a difference in medial-lateral translation between the axisymmetric and patient-specific implants (P = .04). Radiocapitellar kinematics of the tested radial head implants were similar in all but one comparison, and all had different kinematics from the native radial head. Patient-specific radial head implants did not prove advantageous relative to conventional implant designs. The shape of the fixed stem unipolar radial head implants had little influence on radiocapitellar kinematics when optimally positioned in this testing model. Copyright © 2014 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.
    Journal of Shoulder and Elbow Surgery 11/2014; 24(2). DOI:10.1016/j.jse.2014.09.019 · 2.37 Impact Factor
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    ABSTRACT: Background: In-vitro active shoulder motion simulation can provide improved understanding of shoulder biomechanics; however, accurate simulators using advanced control theory have not been developed. Therefore, our objective was to develop and evaluate a simulator which uses real-time kinematic feedback and closed-loop Proportional-Integral-Differential (PID) control to produce motion. The simulator's ability to investigate a clinically relevant variable - namely muscle loading changes resulting from reverse total shoulder arthroplasty (RTSA) - was evaluated and compared to previous findings to further demonstrate its efficacy. Method of approach: Motion control of cadaveric shoulders was achieved by applying continuously variable forces to seven muscle groups. Muscle forces controlling each of the three glenohumeral rotational Degrees-of-Freedom (DOF) were modulated using three independent PID controllers running in parallel, each using measured Euler angles as their process variable. Each PID controller was configured and tuned to control the loading of a set of muscles which, from previous in-vivo investigations, were found to be primarily responsible for movement in the PID's DOF. The simulator's ability to follow setpoint profiles for abduction, axial rotation, and horizontal extension was assessed using Root Mean Squared Error (RMSE) and Average Standard Deviation (ASD) for multiple levels of arm mass replacement. A specimen was then implanted with an RTSA, and the effect of joint lateralization (0, 5, 10mm) on the total deltoid force required to produce motion was assessed. Results: Maximum profiling error was <1.7 degrees for abduction and 2.2 degrees for horizontal extension with RMSE of <1 degree. The non-profiled DOF were maintained to within 5.0 degrees with RMSE <1.0 degrees. Repeatability was high, with ASDs of <0.31 degrees. RMSE and ASD were similar for all levels of arm mass replacement (0.73-1.04 and 0.14-0.22 degrees). Lateralizing the joint's center of rotation increased total deltoid force by up to 8.5% body weight with the maximum early abduction. Conclusions: This simulator, which is the first to use closed-loop control, accurately controls the shoulder's three rotational DOF with high repeatability, and produces results that are in agreement with previous investigations. This simulator's improved performance, in comparison to others, increases the statistical power of its findings and thus its ability to provide new biomechanical insights. Keywords: Shoulder, motion simulation, in-vitro, PID control, reverse total shoulder arthroplasty.
    Journal of Biomechanical Engineering 10/2014; 136(12). DOI:10.1115/1.4028820 · 1.75 Impact Factor
  • Ryan Willing · Michael Lapner · Graham J. W. King · James A. Johnson
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    ABSTRACT: Background Distal humeral hemiarthroplasty results in altered cartilage contact mechanics, which may predispose to osteoarthritis. Current distal humeral hemiarthroplasty prostheses do not replicate the native anatomy, and therefore contribute to these changes. We hypothesized that prostheses reverse-engineered from the native bone shape would provide similar contact patterns as the native articulation. Methods Reverse-engineered distal humeral hemiarthroplasty prostheses were manufactured for five cadaveric elbow specimens based on computed tomographic images of the distal humerus. Passive flexion trials with constant muscle forces were performed with the native articulation intact while bone motions were recorded using a motion tracking system. Motion trials were then repeated after the distal humerus was replaced with a corresponding reverse-engineered prosthesis. Contact areas and patterns were reconstructed using computer models created from computed tomography scan images combined with the motion tracker data. The total contact areas, as well as the contact area within smaller sub-regions of the ulna and radius, were analyzed for changes resulting from distal humeral hemiarthroplasty using repeated-measures analyses of variance. Findings Contact area at the ulna and radius decreased on average 42% (SD 19%, p = .008) and 41% (SD 42%, p = .096), respectively. Contact area decreases were not uniform throughout the different sub-regions, suggesting that contact patterns were also altered. Interpretation Reverse-engineered prostheses did not reproduce the same contact pattern as the native joints, possibly because the thickness of the distal humerus cartilage layer was neglected when generating the prosthesis shapes or as a consequence of the increased stiffness of the metallic implants. Alternative design strategies and materials for distal humeral hemiarthroplasty should be considered in future work.
    Clinical Biomechanics 09/2014; 29(9). DOI:10.1016/j.clinbiomech.2014.08.015 · 1.88 Impact Factor
  • Journal of Shoulder and Elbow Surgery 09/2014; 23(9):e235. DOI:10.1016/j.jse.2014.06.014 · 2.37 Impact Factor
  • Joshua W Giles · Ryan M Degen · James A Johnson · George S Athwal
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    ABSTRACT: Recurrent shoulder instability is commonly associated with glenoid bone defects. Coracoid transfer procedures, such as the Bristow and Latarjet procedures, are frequently used to address these bone deficiencies. Despite the frequent synonymous labeling of these transfers as the "Bristow-Latarjet" procedure, their true equivalence has not been demonstrated. Therefore, our purpose was to compare the biomechanical effects of these two procedures.
    The Journal of Bone and Joint Surgery 08/2014; 96(16):1340-8. DOI:10.2106/JBJS.M.00627 · 4.31 Impact Factor
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    ABSTRACT: Abstract Computer models capable of predicting elbow flexion and extension range of motion (ROM) limits would be useful for assisting surgeons in improving the outcomes of surgical treatment of patients with elbow contractures. A simple and robust computer-based model was developed that predicts elbow joint ROM using bone geometries calculated from computed tomography image data. The model assumes a hinge-like flexion-extension axis, and that elbow passive ROM limits can be based on terminal bony impingement. The model was validated against experimental results with a cadaveric specimen, and was able to predict the flexion and extension limits of the intact joint to 0° and 3°, respectively. The model was also able to predict the flexion and extension limits to 1° and 2°, respectively, when simulated osteophytes were inserted into the joint. Future studies based on this approach will be used for the prediction of elbow flexion-extension ROM in patients with primary osteoarthritis to help identify motion-limiting hypertrophic osteophytes, and will eventually permit real-time computer-assisted navigated excisions.
    Computer Aided Surgery 05/2014; 19(4-6):1-7. DOI:10.3109/10929088.2014.886083 · 1.08 Impact Factor
  • Michael Lapner · Ryan Willing · James A. Johnson · Graham J.W. King
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    ABSTRACT: Background Hemiarthroplasty is a treatment option for selected distal humerus fractures. The purpose of this study was to determine the effect of distal humeral hemiarthroplasty and implant size on articular contact in the elbow. We hypothesized that implants produce significantly different contact areas compared with the native elbow, and that oversized and undersized implants will alter contact area compared to the optimal sized implant. Methods Eight cadaveric arms were tested in an elbow simulator and the kinematics were recorded. Three-dimentional reconstructions of bones and cartilage were generated from computed-tomography images to determine contact patterns. The native articulation was compared to optimally sized, oversized, and undersized implants (Latitude Anatomic Hemiarthroplasty). Changes in contact patterns relative to the native articulation were measured using total contact area and a contact patch agreement score, defined as the sum of distance between contact patches × area. The score indicates how well the size, shape, and location of the contact patches agrees with the native contact pattern. Findings The native articulation had significantly lower ulnohumeral contact patch agreement scores compared to all implants tested (p < 0.05). Mean ulnohumeral and radiocapitellar contact area decreased an average 44% (p = 0.03) and 4% (p = 0.07) respectively following placement of an optimally sized implant. There was no effect of implant size on contact area or contact patch agreement score (p > 0.05). Interpretation Shape differences of the elbow implants relative to the native joint may be responsible for altered contact patterns and could be improved with design modifications. These changes may predispose the elbow to degenerative arthritis. The lack of influence of implant size suggests that implant shape and materials may be more important than implant sizing during surgery. Level of Evidence: Basic Science Study
    Clinical biomechanics (Bristol, Avon) 05/2014; 29(5). DOI:10.1016/j.clinbiomech.2014.03.010 · 1.88 Impact Factor
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    ABSTRACT: Distal humeral hemiarthroplasty is a treatment option for distal humeral fractures, nonunions, and avascular necrosis. The biomechanical effects, however, have not been reported. The purpose of this in vitro study was to quantify the effects of hemiarthroplasty and implant size on elbow joint kinematics. Eight fresh-frozen cadaveric arms were mounted in an in vitro motion simulator. An electromagnetic tracking system quantified elbow kinematics. A custom distal humeral stem was implanted by use of navigation, and 3 humeral articular spools were evaluated: optimally sized, undersized, and oversized. Statistical analysis was performed with repeated-measures analysis of variance. Distal humeral hemiarthroplasty altered elbow kinematics, regardless of implant size. In the valgus position, the optimally sized implant resulted in a mean increase in valgus angulation of 3° ± 1° (P = .003) as compared with the osteotomy control. In the varus position, the optimal and undersized implants both resulted in significant increases in varus angulation: 3° ± 1° (P = .01) and 3° ± 1° (P = .001), respectively. The undersized implant had the greatest alteration in kinematics, whereas the oversized implant best reproduced native elbow kinematics. This study showed a small but significant alteration in elbow joint kinematics with placement of a distal humeral hemiarthroplasty implant, regardless of implant size. This could be due to errors in implant positioning and/or differences in the shape of the humeral implant relative to the native elbow. These changes in joint tracking may cause abnormal articular contact and loading, which may result in pain and cartilage degeneration over time.
    Journal of shoulder and elbow surgery / American Shoulder and Elbow Surgeons ... [et al.] 04/2014; DOI:10.1016/j.jse.2014.02.011 · 2.37 Impact Factor
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    ABSTRACT: Autograft reconstruction of the coronoid using the tip of the olecranon has been described as a treatment option for comminuted coronoid fractures or coronoid nonunions that are not repairable. The purpose of this in vitro biomechanical study of the coronoid-deficient elbow was to determine whether coronoid reconstruction using the tip of the ipsilateral olecranon would restore elbow kinematics. An elbow motion simulator was used to perform active and passive extension of six cadaveric arms in the horizontal, valgus, varus, and vertical orientations. Elbow kinematics were quantified with use of the screw displacement axis of the ulna with respect to the humerus. Testing was performed with an intact coronoid, a 40% coronoid deficiency, and a coronoid reconstruction using the tip of the ipsilateral olecranon. Creation of a 40% coronoid deficiency resulted in significant changes (range, 3.6° to 10.9°) in the angular deviations of the screw displacement axis relative to the intact state during simulated active and passive extension in the varus orientation with the forearm in pronation and in supination (p < 0.05). Reconstruction of the coronoid using the ipsilateral olecranon tip restored the angular deviations to those in the intact state (p > 0.05) with the arm in all orientations except valgus, in which there was a small but significant difference (0.4° ± 0.2°, p = 0.04) during passive motion with forearm supination. Reconstruction of the coronoid using the tip of the ipsilateral olecranon was an effective method for restoring normal kinematics over a range of elbow motion from 20° to 120° in a cadaveric model of an elbow with a 40% coronoid deficiency. This reconstruction technique may prove beneficial for patients with elbow instability due to coronoid deficiency. This study supports the biomechanical concept of coronoid reconstruction using the ipsilateral olecranon tip for coronoid fractures or nonunions involving 40% of the coronoid process.
    The Journal of Bone and Joint Surgery 04/2014; 96(7):590-6. DOI:10.2106/JBJS.L.00698 · 4.31 Impact Factor
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    ABSTRACT: Purpose To examine the effects of dorsal angulation deformities of the distal radius with and without triangular fibrocartilage complex (TFCC) rupture on the 3-dimensional kinematics of the distal radioulnar joint (DRUJ) during simulated active motion. Methods Nine fresh-frozen cadaveric specimens were tested in a forearm simulator that produced active forearm rotation. Dorsal angulation deformities of the distal radius with 100, 20, and 30 angulation were created. Changes in the position of the ulna relative to the radius at the DRUJ as a consequence of each dorsal angulation deformity were quantified during simulated active supination in terms of volar, ulnar, and distal displacement of the ulna. Testing was performed initially with the TFCC intact and repeated after complete sectioning of the TFCC at its ulnar insertion. Results Increasing dorsal angulation deformities of the distal radius significantly increased volar, ulnar, and distal displacement of the ulna when the TFCC was intact. Sectioning of the TFCC significantly increased volar displacement of the ulna in dorsal angulation deformities. As little as 10 of dorsal angulation significantly increased distal displacement of the ulna with the TFCC intact and resulted in a significant increase in volar, ulnar, and distal displacement of the ulna with sectioned TFCC. Conclusions Dorsal angulation deformities of the distal radius affect the 3-dimensional kinematics of the DRUJ, especially with the TFCC sectioned. (Copyright (C) 2014 by the American Society for Surgery of the Hand. All rights reserved.)
    The Journal of hand surgery 04/2014; 39(4). DOI:10.1016/j.jhsa.2014.01.013 · 1.66 Impact Factor

Publication Stats

2k Citations
320.25 Total Impact Points


  • 1997–2015
    • The University of Western Ontario
      • • Department of Mechanical and Materials Engineering
      • • Department of Medical Biophysics
      • • Department of Surgery
      London, Ontario, Canada
  • 2007–2014
    • Western University
      London, Ontario, Canada
    • St. Joseph's Hospital
      Savannah, Georgia, United States
    • Lawson Health Research Institute
      Guilford, England, United Kingdom
  • 1998–2014
    • St. Joseph's Health Care London
      London, Ontario, Canada
  • 1997–2014
    • Lawson Health Research Institute
      London, Ontario, Canada