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Levi J. Hargrove - One of the best experts on this subject based on the ideXlab platform.

  • design development and validation of a lightweight nonbackdrivable robotic Ankle Prosthesis
    IEEE-ASME Transactions on Mechatronics, 2019
    Co-Authors: Tommaso Lenzi, Levi J. Hargrove, Marco Cempini, Todd A Kuiken
    Abstract:

    Robotic Ankle prostheses can imitate the biomechanical function of intact legs at the cost of a larger weight and size compared to conventional passive prostheses. Unfortunately, increased weight and size negatively affect comfort and socket stability, ultimately limiting their clinical viability. Alternatively, a nonbackdrivable transmission system can be used to actively regulate the Ankle position during nonweight bearing activities only. This semiactive design can be made smaller and lighter as a result of the lower actuation power requirements. However, the transmission system must withstand high loads during stance and standing. Thus, available semiactive prostheses are still significantly heavier and have a larger build height than passive Ankle prostheses. In this paper, we present the design, development, and validation of a semiactive Ankle Prosthesis with a nonbackdrivable cam-follower mechanism designed to lower the load on moving components and align with the foot longitudinally as necessary to reduce the Prosthesis weight and size. The proposed Ankle mechanism is ∼50% shorter, has ∼40% wider range of motion (ROM), and is estimated to be ∼27% lighter than available semiactive prostheses. Experiments with a transtibial subject show that the semiactive Prosthesis can increase foot clearance up to 142% and reduce the load on the residual limb as low as 32% compared to passive prostheses.

  • design and characterization of an open source robotic leg Prosthesis
    IEEE International Conference on Biomedical Robotics and Biomechatronics, 2018
    Co-Authors: Alejandro F Azocar, Luke M. Mooney, Levi J. Hargrove, Elliott J. Rouse
    Abstract:

    Challenges associated with current prosthetic technologies limit the quality of life of lower-limb amputees. Passive prostheses lead amputees to walk slower, use more energy, fall more often, and modify their gait patterns to compensate for the Prosthesis' lack of net-positive mechanical energy. Robotic prostheses can provide mechanical energy, but may also introduce challenges through controller design. Fortunately, talented researchers are studying how to best control robotic leg prostheses, but the time and resources required to develop prosthetic hardware has limited their potential impact. Even after research is completed, comparison of results is confounded by the use of different, researcher-specific hardware. To address these issues, we have developed the Open-source Leg (OSL): a scalable robotic knee/Ankle Prosthesis intended to foster investigations of control strategies. This paper introduces the design goals, transmission selection, hardware implementation, and initial control benchmarks for the OSL. The OSL provides a common hardware platform for comparison of control strategies, lowers the barrier to entry for Prosthesis research, and enables testing within the lab, community, and at home.

  • initial results of a variable speed knee controller for walking with a powered knee and Ankle Prosthesis
    IEEE International Conference on Biomedical Robotics and Biomechatronics, 2018
    Co-Authors: Kyle J Kaveny, Ann M. Simon, Suzanne B. Finucane, Tommaso Lenzi, Emily A Seyforth, Graci Finco, Kasen L Culler, Levi J. Hargrove
    Abstract:

    Powered knee and Ankle prostheses can potentially improve the mobility and function of their users, but determining the best way to control the Prosthesis is difficult. Controllers that vary knee swing speed have been shown to restore gait symmetry with a powered knee and Ankle Prosthesis. This study's goal was to combine an existing variable speed knee swing controller with an existing impedance stance controller to determine if comfortable walking with variable cadence can be achieved and if the control method transitions would be noticeable to the user. The knee swing trajectory and duration was varied based on user walking speed as a function of the previous stance phase duration. Four individuals with unilateral transfemoral amputations were fit with a powered knee and Ankle Prosthesis. After 30–45 minutes of practice walking with the variable knee swing controller, subjects performed a variable speed walk test, a steady state walk test, and a 10-meter walk test. A GAITRite mat was used to collect spatial and temporal walking parameters during the 10-meter walk test. Results showed that subjects could control prosthetic knee swing duration and kinematics by modifying their walking speed. Subjects were able to comfortably transition between speeds and achieve mean (SD) comfortable and fast speeds of 1.10 (0.05) and 1.51 (0.05) m/s, respectively for a 10-meter walk test. This study's contribution is to show that a variable speed knee controller can be combined with an impedance-based controller while maintaining the functionality of both controllers and to provide gait mechanics for amputee powered gait that can be used towards future studies of controller development and Prosthesis design.

  • Online adaptive neural control of a robotic lower limb Prosthesis.
    Journal of neural engineering, 2018
    Co-Authors: John A. Spanias, Ann M. Simon, Suzanne B. Finucane, Eric J. Perreault, Levi J. Hargrove
    Abstract:

    Objective The purpose of this study was to develop and evaluate an adaptive intent recognition algorithm that continuously learns to incorporate a lower limb amputee's neural information (acquired via electromyography (EMG)) as they ambulate with a robotic leg Prosthesis. Approach We present a powered lower limb Prosthesis that was configured to acquire the user's neural information and kinetic/kinematic information from embedded mechanical sensors, and identify and respond to the user's intent. We conducted an experiment with eight transfemoral amputees over multiple days. EMG and mechanical sensor data were collected while subjects using a powered knee/Ankle Prosthesis completed various ambulation activities such as walking on level ground, stairs, and ramps. Our adaptive intent recognition algorithm automatically transitioned the Prosthesis into the different locomotion modes and continuously updated the user's model of neural data during ambulation. Main results Our proposed algorithm accurately and consistently identified the user's intent over multiple days, despite changing neural signals. The algorithm incorporated 96.31% [0.91%] (mean, [standard error]) of neural information across multiple experimental sessions, and outperformed non-adaptive versions of our algorithm-with a 6.66% [3.16%] relative decrease in error rate. Significance This study demonstrates that our adaptive intent recognition algorithm enables incorporation of neural information over long periods of use, allowing assistive robotic devices to accurately respond to the user's intent with low error rates.

  • Across-Day Lower Limb Pattern Recognition Performance of a Powered Knee-Ankle Prosthesis
    2018 7th IEEE International Conference on Biomedical Robotics and Biomechatronics (Biorob), 2018
    Co-Authors: Ann M. Simon, Emily A Seyforth, Levi J. Hargrove
    Abstract:

    Powered lower limb prostheses have the capabilities to assist individuals with a lower limb amputation during ambulation. While these devices can generate power at the knee and/or Ankle to assist with incline walking and stair climbing, it is difficult to control the transition between these ambulation modes in a seamless and natural way. Pattern recognition has been suggested as an alternative to using a key fob to switch between modes and recent results have shown reliable performance (less than 5% error rate) across five ambulation modes. In this study we investigated performance of a similar system across multiple sessions of use, a necessary step prior to clinical use. Two individuals with a transfemoral amputation used a powered knee-Ankle for five ambulation activities including level-ground walking, ramp ascent, ramp descent, stair ascent, and stair descent over four sessions spaced out over at least two months. An intent recognition system was trained using embedded Prosthesis mechanical sensors with varying amounts of data collected across the sessions to determine the effect of multi-session use and increased variation in the activities trained. Overall system error rate decreased from 1.45% [0.3%] when the system was trained with Session 1 data only and tested with Session 4 data to 0.60% [0.02%] when the system was trained with Sessions 1-3 data and tested with Session 4 data. These results demonstrate that a reliable intent recognition system can be created with multiple sessions of use, bringing lower limb intent recognition systems for powered prostheses one step closer to clinical viability.

Michael Goldfarb - One of the best experts on this subject based on the ideXlab platform.

  • Design, Control, and Preliminary Assessment of a Multifunctional Semipowered Ankle Prosthesis
    IEEE-ASME Transactions on Mechatronics, 2019
    Co-Authors: Harrison L. Bartlett, Brian E Lawson, Michael Goldfarb
    Abstract:

    This paper describes the design, control, and preliminary assessment of a novel microprocessor-controlled multifunction Ankle Prosthesis that provides three microprocessor-controlled behaviors—a selectable stiffness equilibrium angle, lockable conformal damping, and swing-phase repositioning. Following a description of the motivation for providing these behaviors, the authors provide a detailed description of the device and walking controller design. This device utilizes a power-asymmetric linear actuator to provide the desired functionality in a compact and lightweight package through a combination of both hydraulic and electromechanical actuation approaches. The device is controlled for level ground walking via a finite-state machine. The functionality of the Prosthesis is demonstrated by a set of benchtop experiments that characterize the ability of the Prosthesis to provide the three desired behaviors and by an experiment in which the Prosthesis was worn by a transtibial amputee during walking. Both sets of experiments indicate that the Prosthesis provides the functionality for which it was designed.

  • impact of powered knee Ankle Prosthesis on low back muscle mechanics in transfemoral amputees a case series
    Frontiers in Neuroscience, 2018
    Co-Authors: Chandrasekaran Jayaraman, Michael Goldfarb, Brian E Lawson, Matt Mcguire, Chaithanya Mummidisetty, Rachel Siegal, Aileen Naef, Shenan Hoppeludwig, Susan Deemsdluhy, Keith E Gordon
    Abstract:

    Regular use of prostheses is critical for individuals with lower limb amputations to achieve everyday mobility, maintain physical and psychological health, and achieve a better quality of life. Use of prostheses is influenced by numerous factors, with prosthetic design playing a critical role in facilitating the extent of mobility capabilities an amputee could achieve. Thus, prostheses design can either lead to safe and efficient gait or biomechanically inefficient gait behavior. In addition to increased energy expenditure, such inefficient gait behavior could expose the prosthetic user to an increased risk of secondary musculoskeletal injuries and may eventually lead to rejection of the Prosthesis. Consequently, researchers have exploited the technological advancements in various fields to improve prosthetic devices and customize them for user specific needs. One such prosthetic technology which has been continuously evolving over the past few decades, is the powered prosthetic device family. Presently, an active area of research is the design of novel controllers and components for these devices in order to enable the users of such powered devices to be able to reproduce gait biomechanics that is similar in biomechanical behavior to a healthy limb. In this case series, we studied the impact of using a powered knee-Ankle prostheses (PKA) on two transfemoral amputees who currently use advanced microprocessor controlled knee prostheses (MPK). We integrated evaluations pertaining to kinematics, kinetics, metabolics, and functional activities of daily living to compare the efficacy between the MPK and PKA devices. Our case study investigations suggest that the PKA allows the participants to walk with gait kinematics similar to normal gait patterns observed in healthy limb. In addition to this it was also observed that using the PKA reduced the level of asymmetry in terms of mechanical loading and muscle activation specifically in the low back spinae regions and lower extremity muscles. Furthermore, the PKA allowed the participants to achieve a greater range of variable cadence than their predicate MPK, thus allowing them to safely ambulate in variable environments and also have the ability to dynamically control the lower limbs during mobility. Based on the results of this case study, it appears

  • a unified controller for walking on even and uneven terrain with a powered Ankle Prosthesis
    International Conference of the IEEE Engineering in Medicine and Biology Society, 2018
    Co-Authors: Amanda Huff Shultz, Michael Goldfarb
    Abstract:

    This paper describes the development of a controller for a powered Ankle Prosthesis that is intended to provide appropriate biomechanical behavior for walking on both even and uneven terrain without having to explicitly detect local slope to do so. In order to inform development of the controller, the authors conducted a small study of five healthy subjects walking on even and uneven terrain. Data from the healthy subject study were used to formulate behavioral models for the healthy Ankle, which were then implemented as controller behaviors in the powered Prosthesis prototype and comparatively assessed on an amputee subject.

  • A Stair Ascent and Descent Controller for a Powered Ankle Prosthesis
    IEEE transactions on neural systems and rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society, 2018
    Co-Authors: Steven Culver, Harrison L. Bartlett, Amanda Huff Shultz, Michael Goldfarb
    Abstract:

    This paper presents a control system for a powered transtibial Prosthesis that provides stair ascent and descent capability, as well as ability for user-controlled transitions between walking, standing, stair ascent, and stair descent. The control system was implemented on a powered Prosthesis and evaluated on a single unilateral transtibial amputee subject. The ability of the Prosthesis to provide appropriate functionality during stair ascent and descent was assessed by comparing gait kinematics and kinetics of the Prosthesis to those of a passive dynamic elastic response Prosthesis and those of a set of non-amputee subjects. Data from the assessment indicates that the powered Prosthesis is able to provide some desirable stair ascent and stair descent characteristics, relative to the passive Prosthesis.

  • Variable Cadence Walking and Ground Adaptive Standing With a Powered Ankle Prosthesis
    IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2016
    Co-Authors: Amanda H. Shultz, Brian E Lawson, Michael Goldfarb
    Abstract:

    This paper describes a control approach that provides walking and standing functionality for a powered Ankle Prosthesis, and demonstrates the efficacy of the approach in experiments with a unilateral transtibial amputee subject. Both controllers incorporate a finite-state structure that emulates healthy Ankle joint behavior via a series of piecewise passive impedance functions. The walking controller additionally modifies impedance parameters based on estimated cadence, while the standing controller modulates the Ankle equilibrium angle in order to adapt to the ground slope and user posture, and the supervisory controller selects between the walking and standing controllers. The system is shown to reproduce several essential biomechanical features of the healthy joint during walking, particularly relative to a passive Prosthesis, and is shown to adapt to various cadences. The system is also shown to adapt to slopes over a range of ±15°, providing support to the user, as validated by quasi-static stiffness measurements recorded by the Prosthesis. The subject is shown to place more weight on the powered Prosthesis than on his passive Prosthesis when standing on sloped surfaces, particularly at angles of 10° or greater. The authors also demonstrated that the Prosthesis typically began providing support within 1 s of initial ground contact. Further, the supervisory controller was shown to effectively switch between walking and standing, as well as determine ground slope just prior to the transition from the standing controller to the walking controller, where the estimated ground slope was accurate to within 1.25° for all trials.

Alexej Barg - One of the best experts on this subject based on the ideXlab platform.

  • Intraoperative Radiographic Assessment of Ankle Prosthesis Alignment
    SAGE Publishing, 2018
    Co-Authors: Alexej Barg, Maxwell Weinberg Bsc, Charles Saltzman
    Abstract:

    Category: Ankle Arthritis Introduction/Purpose: In the last 2 decades, total Ankle replacement (TAR) has gained greater acceptance as a treatment option for patients with end-stage Ankle osteoarthritis. However, TAR still has a higher failure rate than either hip or knee replacements. One of the most common reasons for TAR failure is malalignment of the Prosthesis component which accounts for 15% of all failures. The purpose of this study was to assess Ankle Prosthesis alignment using intraoperative fluoroscopy images and to compare the results with postoperative weightbearing radiographs. Methods: Sixty-eight primary TARs were performed using the Zimmer trabecular metal implant (37 men and 31 women, mean age of 67.7±8.2 years) from October 2012 to August 2017. Alpha and beta angles were used to assess the alignment of the tibial component in the coronal and sagittal plane, respectively. Gamma angle was used to assess the alignment of the talar component in the sagittal plane. All measurements were performed by two observers (ICC 0.787-0.984). One observer evaluated all images twice at a 6-week interval to determine the intraobserver reliability (ICC 0.858-0.986). Results: There were significant differences between intraoperative and postoperative assessment for all three angles. For the alpha angle, the mean absolute difference was 1.8º±1.5º with a range between 0º and 6º (p = 0.001). For the beta angle, the mean absolute difference was 2.1º±1.5º with a range between 0º and 7º (p = 0.034). For gamma angle, the mean absolute difference was 2.0º±1.5º with a range between 0º and 6º (p = 0.002). The Pearson coefficient for the alpha, beta, and gamma angle was 0.664 (p < 0.001), 0.852 (p < 0.001), and 0.928 (p < 0.001), respectively. Conclusion: In the present study, radiographic assessment of the Prosthesis’ component alignment demonstrated significant differences up to 7 degrees. This can be partially explained by the lack of a standardized radiographic technique to obtain fluoroscopic images, difficult identification of anatomic landmarks for intraoperative measurements, and distortion of x-rays using fluoroscopy

  • aseptic loosening of total Ankle replacement two stage revision with bone augmentation of osseous defects and secondary Prosthesis implantation
    Operative Orthopadie Und Traumatologie, 2017
    Co-Authors: Alexej Barg, Martin Wiewiorski, Victor Valderrabano
    Abstract:

    Objective To remove loosened Ankle Prosthesis components, perform osseous defect augmentation, and reimplant definitive Prosthesis components to preserve Ankle range of motion. Indications Aseptic loosening of the tibial and/or talar Ankle Prosthesis components with substantial bone defect. Contraindications General surgical/anesthesiological risks, infections, critical soft tissue conditions, nonmanageable hindfoot instability, neurovascular impairment of the lower extremity, neuroarthropathy, substantial nonreconstructable osseous defects with or without cysts on the tibial and/or talar side, noncompliance, primary total Ankle replacement (TAR) using intramedullary fixation (stem fixation), severely reduced bone quality, insulin-dependent diabetes mellitus, smoking, unrealistic patients' expectations, high activity in sports. Surgical technique Exposure of the Ankle joint using the previous incision. Mobilization and removal of loosened Prosthesis components. Debridement of bone stock. Assessment and measurement of osseous defects. Harvesting of iliac crest autograft. Screw fixation of iliac crest autograft. Placement of polyethylene inlay as a spacer. Wound closure in layers at the Ankle and the iliac crest. Implantation of definitive Prosthesis components. Postoperative management A soft wound dressing. Thromboprophylaxis recommended. Mobilization on postoperative day 1 using a stabilizing walking boot/cast for 6 weeks (sole contact but no weight bearing). Clinical and radiographic follow-up 3 months postoperatively including computed tomography to assess osseous consolidation. After the second surgery, patient mobilization on postoperative day 1 with 15 kg partial weight bearing using a stabilizing walking boot/cast for 6 weeks. Following clinical and radiographic follow-up at 6 weeks, full weight bearing is initiated gradually. Results From January 2007 to December 2012, a two-stage revision TAR was performed in 5 patients (46.8 and 71.4 years). The time between the initial TAR and revision was 2.4-11.5 years. No intra-/perioperative complications. Substantial pain relief in all patients. Comparable preoperative and postoperative Ankle range of motion.

  • hintegra total Ankle replacement survivorship analysis in 684 patients
    Journal of Bone and Joint Surgery American Volume, 2013
    Co-Authors: Alexej Barg, Markus Knupp, Lukas Zwicky, Heath B. Henninger, Beat Hintermann
    Abstract:

    Background: Total Ankle replacement is increasingly recommended for patients with end-stage Ankle osteoarthritis. We analyzed the survivorship of 722 arthroplasties performed with one type of three-component total Ankle Prosthesis. Methods: Seven hundred and seventy-nine primary total Ankle arthroplasties (741 patients) were performed between May 2000 and July 2010 with use of the HINTEGRA three-component Prosthesis. A logistic multiple regression model was used to identify independent risk factors for Prosthesis failure in 684 patients (722 Ankles). The mean time to final follow-up (and standard deviation) was 6.3 ± 2.9 years. Results: Seven hundred and twenty-two Ankles (684 patients) were available for survivorship analysis at the latest follow-up. The overall survival rates were 94% and 84% after five and ten years, respectively. Sixty-one Ankles had a revision arthroplasty (twenty-seven both components, thirteen the tibial component only, and fourteen the talar component only) or were converted to a fusion (seven Ankles).There were no polyethylene failures. There were no amputations. The generation category of the Prosthesis, the cause of Ankle osteoarthritis, and the age of the patient were identified as independent risk factors for Prosthesis failure. Conclusions: The midterm survivorship of the HINTEGRA implant was comparable with that of other third-generation total Ankle replacements. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

  • hintegra revision arthroplasty for failed total Ankle prostheses
    Journal of Bone and Joint Surgery American Volume, 2013
    Co-Authors: Beat Hintermann, Markus Knupp, Lukas Zwicky, Heath B. Henninger, Alexej Barg
    Abstract:

    Background When a total Ankle replacement fails, arthrodesis has been advocated as the treatment of choice. With the availability of a wide spectrum of implants, revision arthroplasty may become a viable alternative. Methods We reviewed a consecutive series of 117 cases (116 patients [fifty-six female and sixty male]; mean age, 55.0 ± 12.0 years) in which a total Ankle arthroplasty failed after a mean of 4.3 years and was revised with use of the HINTEGRA three-component total Ankle Prosthesis. The reason for revision involved the metallic components in sixty Ankles (51%), the bone in twenty-eight (24%), the soft tissues in twenty (17%), and infection in nine (8%). The talar component was revised in 104 Ankles (89%) and the tibial component, in 106 (91%). Results Early complications included a fracture of the malleoli in two Ankles and a dislocation of the polyethylene insert in one. Seventeen (15%) of the revision arthroplasties required further revision surgery, in most cases for loosening of one or two of the prosthetic components. The mean American Orthopaedic Foot & Ankle Society (AOFAS) hindfoot score for the remaining 100 Ankles (85%) improved from 44 ± 18 preoperatively to 72 ± 19 (p Conclusions The medium-term results of revision arthroplasty after a failed total Ankle arthroplasty were similar to those after primary arthroplasty. The key to success was firm anchorage of the components to primary bone stock. A single hydroxyapatite component coating should no longer be used for revision total Ankle arthroplasty.

  • HINTEGRA Revision Arthroplasty for Failed Total Ankle Prostheses
    JBJS essential surgical techniques, 2013
    Co-Authors: Beat Hintermann, Markus Knupp, Lukas Zwicky, Heath B. Henninger, Alexej Barg
    Abstract:

    [Introduction][1] In our experience, revision Ankle arthroplasty with a three-component total Ankle Prosthesis following a failed total Ankle replacement has provided encouraging midterm results with substantial pain relief while preserving the range of motion of the replaced Ankle. [Step 1: Preoperative Assessment and Planning][2] Determine the treatment using a decision algorithm. ![Figure][3] ![Figure][3] ![Figure][3] [Step 2: Patient Positioning][4] Use spinal or general anesthesia, administer intravenous antibiotics, position the patient supine, and apply a tourniquet. [Step 3: Surgical Approach to the Failed Prosthesis][5] Use an anterior approach to expose the failed Ankle Prosthesis. [Step 4: Removal of the Prosthesis][6] Remove the polyethylene insert, the talar component, and the tibial component, making sure to not compromise any remaining bone stock. ![Figure][3] [Step 5: Revision Ankle Arthroplasty][7] Prepare the tibial and talar bone stock to obtain solid osseous surfaces, and use the appropriate prosthetic components. ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] [Step 6: Additional SurgicalProcedures (If Necessary)][8] If necessary, perform arthrodesis of adjacent joints, correcting osteotomies of the distal parts of the tibia and fibula, calcaneal osteotomy, and/or ligamentoplasty. ![Figure][3] ![Figure][3] ![Figure][3] [Step 7: Closure of All Incisions][9] Close all incisions. [Step 8: Postoperative Care][10] A short leg splint is worn for two days, followed by partial weight-bearing; the Ankle is protected in a splint at night and with a walking boot during the day for six to eight weeks. [Results][11] Between 2000 and 2010, 117 Ankles in 116 patients (fifty-six female and sixty male; mean age, 55.0 ± 12.0 years) who presented with a failed total Ankle arthroplasty after a mean of 4.3 ± 3.9 years were treated by revision arthroplasty with use of the HINTEGRA three-component total Ankle Prosthesis[12][12]. [What to Watch For][13] [Indications][14] [Contraindications][15] [Pitfalls & Challenges][16] [Introduction][1] In our experience, revision Ankle arthroplasty with a three-component total Ankle Prosthesis following a failed total Ankle replacement has provided encouraging midterm results with substantial pain relief while preserving the range of motion of the replaced Ankle. [Step 1: Preoperative Assessment and Planning][2] Determine the treatment using a decision algorithm. ![Figure][3] ![Figure][3] ![Figure][3] [Step 2: Patient Positioning][4] Use spinal or general anesthesia, administer intravenous antibiotics, position the patient supine, and apply a tourniquet. [Step 3: Surgical Approach to the Failed Prosthesis][5] Use an anterior approach to expose the failed Ankle Prosthesis. [Step 4: Removal of the Prosthesis][6] Remove the polyethylene insert, the talar component, and the tibial component, making sure to not compromise any remaining bone stock. ![Figure][3] [Step 5: Revision Ankle Arthroplasty][7] Prepare the tibial and talar bone stock to obtain solid osseous surfaces, and use the appropriate prosthetic components. ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] [Step 6: Additional SurgicalProcedures (If Necessary)][8] If necessary, perform arthrodesis of adjacent joints, correcting osteotomies of the distal parts of the tibia and fibula, calcaneal osteotomy, and/or ligamentoplasty. ![Figure][3] ![Figure][3] ![Figure][3] [Step 7: Closure of All Incisions][9] Close all incisions. [Step 8: Postoperative Care][10] A short leg splint is worn for two days, followed by partial weight-bearing; the Ankle is protected in a splint at night and with a walking boot during the day for six to eight weeks. [Results][11] Between 2000 and 2010, 117 Ankles in 116 patients (fifty-six female and sixty male; mean age, 55.0 ± 12.0 years) who presented with a failed total Ankle arthroplasty after a mean of 4.3 ± 3.9 years were treated by revision arthroplasty with use of the HINTEGRA three-component total Ankle Prosthesis[12][12]. [What to Watch For][13] [Indications][14] [Contraindications][15] [Pitfalls & Challenges][16] [1]: #sec-12 [2]: #sec-13 [3]: pending:yes [4]: #sec-14 [5]: #sec-15 [6]: #sec-16 [7]: #sec-17 [8]: #sec-18 [9]: #sec-28 [10]: #sec-29 [11]: #sec-30 [12]: #ref-12 [13]: #sec-22 [14]: #sec-32 [15]: #sec-33 [16]: #sec-34

Beat Hintermann - One of the best experts on this subject based on the ideXlab platform.

  • hintegra total Ankle replacement survivorship analysis in 684 patients
    Journal of Bone and Joint Surgery American Volume, 2013
    Co-Authors: Alexej Barg, Markus Knupp, Lukas Zwicky, Heath B. Henninger, Beat Hintermann
    Abstract:

    Background: Total Ankle replacement is increasingly recommended for patients with end-stage Ankle osteoarthritis. We analyzed the survivorship of 722 arthroplasties performed with one type of three-component total Ankle Prosthesis. Methods: Seven hundred and seventy-nine primary total Ankle arthroplasties (741 patients) were performed between May 2000 and July 2010 with use of the HINTEGRA three-component Prosthesis. A logistic multiple regression model was used to identify independent risk factors for Prosthesis failure in 684 patients (722 Ankles). The mean time to final follow-up (and standard deviation) was 6.3 ± 2.9 years. Results: Seven hundred and twenty-two Ankles (684 patients) were available for survivorship analysis at the latest follow-up. The overall survival rates were 94% and 84% after five and ten years, respectively. Sixty-one Ankles had a revision arthroplasty (twenty-seven both components, thirteen the tibial component only, and fourteen the talar component only) or were converted to a fusion (seven Ankles).There were no polyethylene failures. There were no amputations. The generation category of the Prosthesis, the cause of Ankle osteoarthritis, and the age of the patient were identified as independent risk factors for Prosthesis failure. Conclusions: The midterm survivorship of the HINTEGRA implant was comparable with that of other third-generation total Ankle replacements. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

  • hintegra revision arthroplasty for failed total Ankle prostheses
    Journal of Bone and Joint Surgery American Volume, 2013
    Co-Authors: Beat Hintermann, Markus Knupp, Lukas Zwicky, Heath B. Henninger, Alexej Barg
    Abstract:

    Background When a total Ankle replacement fails, arthrodesis has been advocated as the treatment of choice. With the availability of a wide spectrum of implants, revision arthroplasty may become a viable alternative. Methods We reviewed a consecutive series of 117 cases (116 patients [fifty-six female and sixty male]; mean age, 55.0 ± 12.0 years) in which a total Ankle arthroplasty failed after a mean of 4.3 years and was revised with use of the HINTEGRA three-component total Ankle Prosthesis. The reason for revision involved the metallic components in sixty Ankles (51%), the bone in twenty-eight (24%), the soft tissues in twenty (17%), and infection in nine (8%). The talar component was revised in 104 Ankles (89%) and the tibial component, in 106 (91%). Results Early complications included a fracture of the malleoli in two Ankles and a dislocation of the polyethylene insert in one. Seventeen (15%) of the revision arthroplasties required further revision surgery, in most cases for loosening of one or two of the prosthetic components. The mean American Orthopaedic Foot & Ankle Society (AOFAS) hindfoot score for the remaining 100 Ankles (85%) improved from 44 ± 18 preoperatively to 72 ± 19 (p Conclusions The medium-term results of revision arthroplasty after a failed total Ankle arthroplasty were similar to those after primary arthroplasty. The key to success was firm anchorage of the components to primary bone stock. A single hydroxyapatite component coating should no longer be used for revision total Ankle arthroplasty.

  • HINTEGRA Revision Arthroplasty for Failed Total Ankle Prostheses
    JBJS essential surgical techniques, 2013
    Co-Authors: Beat Hintermann, Markus Knupp, Lukas Zwicky, Heath B. Henninger, Alexej Barg
    Abstract:

    [Introduction][1] In our experience, revision Ankle arthroplasty with a three-component total Ankle Prosthesis following a failed total Ankle replacement has provided encouraging midterm results with substantial pain relief while preserving the range of motion of the replaced Ankle. [Step 1: Preoperative Assessment and Planning][2] Determine the treatment using a decision algorithm. ![Figure][3] ![Figure][3] ![Figure][3] [Step 2: Patient Positioning][4] Use spinal or general anesthesia, administer intravenous antibiotics, position the patient supine, and apply a tourniquet. [Step 3: Surgical Approach to the Failed Prosthesis][5] Use an anterior approach to expose the failed Ankle Prosthesis. [Step 4: Removal of the Prosthesis][6] Remove the polyethylene insert, the talar component, and the tibial component, making sure to not compromise any remaining bone stock. ![Figure][3] [Step 5: Revision Ankle Arthroplasty][7] Prepare the tibial and talar bone stock to obtain solid osseous surfaces, and use the appropriate prosthetic components. ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] [Step 6: Additional SurgicalProcedures (If Necessary)][8] If necessary, perform arthrodesis of adjacent joints, correcting osteotomies of the distal parts of the tibia and fibula, calcaneal osteotomy, and/or ligamentoplasty. ![Figure][3] ![Figure][3] ![Figure][3] [Step 7: Closure of All Incisions][9] Close all incisions. [Step 8: Postoperative Care][10] A short leg splint is worn for two days, followed by partial weight-bearing; the Ankle is protected in a splint at night and with a walking boot during the day for six to eight weeks. [Results][11] Between 2000 and 2010, 117 Ankles in 116 patients (fifty-six female and sixty male; mean age, 55.0 ± 12.0 years) who presented with a failed total Ankle arthroplasty after a mean of 4.3 ± 3.9 years were treated by revision arthroplasty with use of the HINTEGRA three-component total Ankle Prosthesis[12][12]. [What to Watch For][13] [Indications][14] [Contraindications][15] [Pitfalls & Challenges][16] [Introduction][1] In our experience, revision Ankle arthroplasty with a three-component total Ankle Prosthesis following a failed total Ankle replacement has provided encouraging midterm results with substantial pain relief while preserving the range of motion of the replaced Ankle. [Step 1: Preoperative Assessment and Planning][2] Determine the treatment using a decision algorithm. ![Figure][3] ![Figure][3] ![Figure][3] [Step 2: Patient Positioning][4] Use spinal or general anesthesia, administer intravenous antibiotics, position the patient supine, and apply a tourniquet. [Step 3: Surgical Approach to the Failed Prosthesis][5] Use an anterior approach to expose the failed Ankle Prosthesis. [Step 4: Removal of the Prosthesis][6] Remove the polyethylene insert, the talar component, and the tibial component, making sure to not compromise any remaining bone stock. ![Figure][3] [Step 5: Revision Ankle Arthroplasty][7] Prepare the tibial and talar bone stock to obtain solid osseous surfaces, and use the appropriate prosthetic components. ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] [Step 6: Additional SurgicalProcedures (If Necessary)][8] If necessary, perform arthrodesis of adjacent joints, correcting osteotomies of the distal parts of the tibia and fibula, calcaneal osteotomy, and/or ligamentoplasty. ![Figure][3] ![Figure][3] ![Figure][3] [Step 7: Closure of All Incisions][9] Close all incisions. [Step 8: Postoperative Care][10] A short leg splint is worn for two days, followed by partial weight-bearing; the Ankle is protected in a splint at night and with a walking boot during the day for six to eight weeks. [Results][11] Between 2000 and 2010, 117 Ankles in 116 patients (fifty-six female and sixty male; mean age, 55.0 ± 12.0 years) who presented with a failed total Ankle arthroplasty after a mean of 4.3 ± 3.9 years were treated by revision arthroplasty with use of the HINTEGRA three-component total Ankle Prosthesis[12][12]. [What to Watch For][13] [Indications][14] [Contraindications][15] [Pitfalls & Challenges][16] [1]: #sec-12 [2]: #sec-13 [3]: pending:yes [4]: #sec-14 [5]: #sec-15 [6]: #sec-16 [7]: #sec-17 [8]: #sec-18 [9]: #sec-28 [10]: #sec-29 [11]: #sec-30 [12]: #ref-12 [13]: #sec-22 [14]: #sec-32 [15]: #sec-33 [16]: #sec-34

  • short and mid term results with the star total Ankle Prosthesis
    Orthopade, 1999
    Co-Authors: Beat Hintermann
    Abstract:

    We evaluated the short- to mid-term results of an unconstrained total Ankle Prosthesis (S. T. A. R.) with uncemented fixation. Fifty consecutive Ankle replacements were performed in 48 patients between 1996 and 1999. The initial diagnosis was posttraumatic osteoarthrosis in 31 cases (62 %), primary osteoarthrosis in 8 cases (16 %), and systemic joint affection in 11 cases (22 %), e. g. rheumatoid arthritis (6 cases), hemochromatosis (2 cases), psoriasis arthritis (1 case), lupus erythematodes (1 case), and sclerodermia (1 case). There were two perioperative complications: one superficial wound dehiscence that healed uneventfully, and one injury to the dorsal foot artery that necessitated primary reconstruction. Seven revisions, all in cases of posttraumatic arthrosis, were necessary: local revision of the fibula for painful lateral impingement (3 cases), posteromedial soft tissue revision for painful restriction of dorsiflexion (2 cases), percutaneous lengthening of the Achilles tendon (1 case), and osteotomy and callus distraction for angular correction after stress fracture of the distal tibia (1 case). At the last follow-up control, 21 patients (62 %) were very satisfied, 10 patients (29 %) were satisfied, and 3 patients (9 %) were satisfied with reservations. The obtained range of motion was 30 ° (range, 15 to 55 °), with a maximal plantarflexion of 25 ° (range, 15 to 45 °) and dorsiflexion of 5 ° (–3 to 20 °). When the AOFAS-Hindfoot-Score was applied, the 34 patients scored 84.1 points (range, 44 to 100 points). After settling of the implants within 6 weeks, no migration was noted in any case, and all implants were considered to be stable. The favorable results were considered to be a result of the mechanical properties of the S. T. A. R. total Ankle Prosthesis that allows for unconstrained motion of the polyethylene inlay on the tibial component, e. g. anteroposterior translation, mediolateral translation and axial rotation. The success of implantation may depend on exact technique, correct hindfoot alignement, sufficient capsuloligamentous stability of the Ankle, and a solid bone stock. Although our first results are very encouraging, a longer follow-up is mandatory to answer the question whether Ankle replacement is a viable alternative to Ankle arthrodesis.

Ann M. Simon - One of the best experts on this subject based on the ideXlab platform.

  • initial results of a variable speed knee controller for walking with a powered knee and Ankle Prosthesis
    IEEE International Conference on Biomedical Robotics and Biomechatronics, 2018
    Co-Authors: Kyle J Kaveny, Ann M. Simon, Suzanne B. Finucane, Tommaso Lenzi, Emily A Seyforth, Graci Finco, Kasen L Culler, Levi J. Hargrove
    Abstract:

    Powered knee and Ankle prostheses can potentially improve the mobility and function of their users, but determining the best way to control the Prosthesis is difficult. Controllers that vary knee swing speed have been shown to restore gait symmetry with a powered knee and Ankle Prosthesis. This study's goal was to combine an existing variable speed knee swing controller with an existing impedance stance controller to determine if comfortable walking with variable cadence can be achieved and if the control method transitions would be noticeable to the user. The knee swing trajectory and duration was varied based on user walking speed as a function of the previous stance phase duration. Four individuals with unilateral transfemoral amputations were fit with a powered knee and Ankle Prosthesis. After 30–45 minutes of practice walking with the variable knee swing controller, subjects performed a variable speed walk test, a steady state walk test, and a 10-meter walk test. A GAITRite mat was used to collect spatial and temporal walking parameters during the 10-meter walk test. Results showed that subjects could control prosthetic knee swing duration and kinematics by modifying their walking speed. Subjects were able to comfortably transition between speeds and achieve mean (SD) comfortable and fast speeds of 1.10 (0.05) and 1.51 (0.05) m/s, respectively for a 10-meter walk test. This study's contribution is to show that a variable speed knee controller can be combined with an impedance-based controller while maintaining the functionality of both controllers and to provide gait mechanics for amputee powered gait that can be used towards future studies of controller development and Prosthesis design.

  • Online adaptive neural control of a robotic lower limb Prosthesis.
    Journal of neural engineering, 2018
    Co-Authors: John A. Spanias, Ann M. Simon, Suzanne B. Finucane, Eric J. Perreault, Levi J. Hargrove
    Abstract:

    Objective The purpose of this study was to develop and evaluate an adaptive intent recognition algorithm that continuously learns to incorporate a lower limb amputee's neural information (acquired via electromyography (EMG)) as they ambulate with a robotic leg Prosthesis. Approach We present a powered lower limb Prosthesis that was configured to acquire the user's neural information and kinetic/kinematic information from embedded mechanical sensors, and identify and respond to the user's intent. We conducted an experiment with eight transfemoral amputees over multiple days. EMG and mechanical sensor data were collected while subjects using a powered knee/Ankle Prosthesis completed various ambulation activities such as walking on level ground, stairs, and ramps. Our adaptive intent recognition algorithm automatically transitioned the Prosthesis into the different locomotion modes and continuously updated the user's model of neural data during ambulation. Main results Our proposed algorithm accurately and consistently identified the user's intent over multiple days, despite changing neural signals. The algorithm incorporated 96.31% [0.91%] (mean, [standard error]) of neural information across multiple experimental sessions, and outperformed non-adaptive versions of our algorithm-with a 6.66% [3.16%] relative decrease in error rate. Significance This study demonstrates that our adaptive intent recognition algorithm enables incorporation of neural information over long periods of use, allowing assistive robotic devices to accurately respond to the user's intent with low error rates.

  • Across-Day Lower Limb Pattern Recognition Performance of a Powered Knee-Ankle Prosthesis
    2018 7th IEEE International Conference on Biomedical Robotics and Biomechatronics (Biorob), 2018
    Co-Authors: Ann M. Simon, Emily A Seyforth, Levi J. Hargrove
    Abstract:

    Powered lower limb prostheses have the capabilities to assist individuals with a lower limb amputation during ambulation. While these devices can generate power at the knee and/or Ankle to assist with incline walking and stair climbing, it is difficult to control the transition between these ambulation modes in a seamless and natural way. Pattern recognition has been suggested as an alternative to using a key fob to switch between modes and recent results have shown reliable performance (less than 5% error rate) across five ambulation modes. In this study we investigated performance of a similar system across multiple sessions of use, a necessary step prior to clinical use. Two individuals with a transfemoral amputation used a powered knee-Ankle for five ambulation activities including level-ground walking, ramp ascent, ramp descent, stair ascent, and stair descent over four sessions spaced out over at least two months. An intent recognition system was trained using embedded Prosthesis mechanical sensors with varying amounts of data collected across the sessions to determine the effect of multi-session use and increased variation in the activities trained. Overall system error rate decreased from 1.45% [0.3%] when the system was trained with Session 1 data only and tested with Session 4 data to 0.60% [0.02%] when the system was trained with Sessions 1-3 data and tested with Session 4 data. These results demonstrate that a reliable intent recognition system can be created with multiple sessions of use, bringing lower limb intent recognition systems for powered prostheses one step closer to clinical viability.

  • delaying ambulation mode transition decisions improves accuracy of a flexible control system for powered knee Ankle Prosthesis
    IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2017
    Co-Authors: Ann M. Simon, Aaron Young, John A. Spanias, Suzanne B. Finucane, Kimberly A Ingraham, Elizabeth G Halsne, Levi J. Hargrove
    Abstract:

    Powered lower limb prostheses can assist users in a variety of ambulation modes by providing knee and/or Ankle joint power. This study’s goal was to develop a flexible control system to allow users to perform a variety of tasks in a natural, accurate, and reliable way. Six transfemoral amputees used a powered knee-Ankle Prosthesis to ascend/descend a ramp, climb a 3- and 4-step staircase, perform walking and standing transitions to and from the staircase, and ambulate at various speeds. A mode-specific classification architecture was developed to allow seamless transitions at four discrete gait events. Prosthesis mode transitions (i.e., the Prosthesis’ mechanical response) were delayed by 90 ms. Overall, users were not affected by this small delay. Offline classification results demonstrate significantly reduced error rates with the delayed system compared to the non-delayed system (p < 0.001). The average error rate for all heel contact decisions was 1.65% [0.99%] for the non-delayed system and 0.43% [0.23%] for the delayed system. The average error rate for all toe off decisions was 0.47% [0.16%] for the non-delayed system and 0.13% [0.05%] for the delayed system. The results are encouraging and provide another step towards a clinically viable intent recognition system for a powered knee-Ankle Prosthesis.

  • improved weight bearing symmetry for transfemoral amputees during standing up and sitting down with a powered knee Ankle Prosthesis
    Archives of Physical Medicine and Rehabilitation, 2016
    Co-Authors: Ann M. Simon, Nicholas P. Fey, Levi J. Hargrove, Suzanne B. Finucane, Kimberly A Ingraham, Elizabeth G Halsne
    Abstract:

    Abstract Objective To test a new user-modulated control strategy that enables improved control of a powered knee-Ankle Prosthesis during sit-to-stand and stand-to-sit movements. Design Within-subject comparison study. Setting Gait laboratory. Participants Unilateral transfemoral amputees (N=7; 4 men, 3 women) capable of community ambulation. Interventions Subjects performed 10 repetitions of sit-to-stand and stand-to-sit with a powered knee-Ankle Prosthesis and with their prescribed passive Prosthesis in a randomized order. With the powered Prosthesis, knee and Ankle power generation were controlled as a function of weight transferred onto the Prosthesis. Main Outcome Measures Vertical ground reaction force limb asymmetry and durations of movement were compared statistically (Wilcoxon signed-rank test, α=.05). Results For sit-to-stand, peak vertical ground reaction forces were significantly less asymmetric using the powered Prosthesis (mean, 19.3%±11.8%) than the prescribed Prosthesis (57.9%±13.5%; P =.018), where positive asymmetry values represented greater force through the intact limb. For stand-to-sit, peak vertical ground reaction forces were also significantly less asymmetric using the powered Prosthesis (28.06%±11.6%) than the prescribed Prosthesis (48.2%±16%; P =.028). Duration of movement was not significantly different between devices (sit-to-stand: P =.18; stand-to-sit: P =.063). Conclusions Allowing transfemoral amputees more control over the timing and rate of knee and Ankle power generation enabled users to stand up and sit down with their weight distributed more equally between their lower limbs. Increased weight bearing on the prosthetic limb may make such activities of daily living easier for transfemoral amputees.