Publications by authors named "Kenneth Hunt"

139 Publications

Paediatric ankle cartilage lesions: Proceedings of the International Consensus Meeting on Cartilage Repair of the Ankle.

J ISAKOS 2022 Apr 13. Epub 2022 Apr 13.

Department of Orthopaedic Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA, USA.

Background: The evidence supporting best practice guidelines in the field of cartilage repair of the ankle are based on both low quality and low levels of evidence. Therefore, an international consensus group of experts was convened to collaboratively advance toward consensus opinions based on the best available evidence on key topics within cartilage repair of the ankle. The purpose of this article is to report the consensus statements on "Pediatric Ankle Cartilage Lesions" developed at the 2019 International Consensus Meeting on Cartilage Repair of the Ankle.

Methods: Forty-three international experts in cartilage repair of the ankle representing 20 countries convened to participate in a process based on the Delphi method of achieving consensus. Questions and statements were drafted within four working groups focusing on specific topics within cartilage repair of the ankle, after which a comprehensive literature review was performed and the available evidence for each statement was graded. Discussion and debate occurred in cases where statements were not agreed upon in unanimous fashion within the working groups. A final vote was then held, and the strength of consensus was characterised as follows: consensus: 51-74%; strong consensus: 75-99%; unanimous: 100%.

Results: A total of 12 statements on paediatric ankle cartilage lesions reached consensus during the 2019 International Consensus Meeting on Cartilage Repair of the Ankle. Five achieved unanimous support, and seven reached strong consensus (>75% agreement). All statements reached at least 84% agreement.

Conclusions: This international consensus derived from leaders in the field will assist clinicians with the management of paediatric ankle cartilage lesions.
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http://dx.doi.org/10.1016/j.jisako.2022.04.001DOI Listing
April 2022

Medical and Biomechanical Risk Factors for Incident Bone Stress Injury in Collegiate Runners: Can Plantar Pressure Predict Injury?

Orthop J Sports Med 2022 Jun 15;10(6):23259671221104793. Epub 2022 Jun 15.

Stanford Medical Center, Redwood City, California, USA.

Background: Bone stress injury (BSI) is a common reason for missed practices and competitions in elite track and field runners.

Hypothesis: It was hypothesized that, after accounting for medical risk factors, higher plantar loading during running, walking, and athletic movements would predict the risk of future BSI in elite collegiate runners.

Study Design: Cohort study; Level of evidence, 2.

Methods: A total of 39 elite collegiate runners (24 male, 15 female) were evaluated during the 2014-2015 academic year to determine the degree to which plantar pressure data and medical history (including Female and Male Athlete Triad risk factors) could predict subsequent BSI. Runners completed athletic movements while plantar pressures and contact areas in 7 key areas of the foot were recorded, and the measurements were reported overall and by specific foot area. Regression models were constructed to determine factors related to incident BSI.

Results: Twenty-one runners (12 male, 9 female) sustained ≥1 incident BSI during the study period. Four regression models incorporating both plantar pressure measurements and medical risk factors were able to predict the subsequent occurrence of (A) BSIs in female runners, (B) BSIs in male runners, (C) multiple BSIs in either male or female runners, and (D) foot BSIs in female runners. Model A used maximum mean pressure (MMP) under the first metatarsal during a jump takeoff and only misclassified 1 female with no BSI. Model B used increased impulses under the hindfoot and second through fifth distal metatarsals while walking, and under the lesser toes during a cutting task, correctly categorizing 83.3% of male runners. Model C used higher medial midfoot peak pressure during a shuttle run and triad cumulative risk scores and correctly categorized 93.3% of runners who did not incur multiple BSIs and 66.7% of those who did. Model D included lower hindfoot impulses in the shuttle run and higher first metatarsal MMP during treadmill walking to correctly predict the subsequent occurrence of a foot BSI for 75% of women and 100% without.

Conclusion: The models collectively suggested that higher plantar pressure may contribute to risk for BSI.
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http://dx.doi.org/10.1177/23259671221104793DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9208063PMC
June 2022

Management of Treatment Failures in Osteochondral Lesions of the Talus.

Foot Ankle Clin 2022 Jun 11;27(2):385-399. Epub 2022 May 11.

Department of Orthopaedic Surgery, University of Colorado School of Medicine, 12631 East 17th Ave, Room 4508, Aurora, CO 80045, USA.

Osteochondral lesions of the talus are a common result of traumatic ankle injury. Due to the low success rates of nonoperative management, surgical management of osteochondral lesions of the talus (OLTs) has evolved considerably over the past decade as more outcomes research has emerged, new techniques have been described, and we have developed a better understanding of the role of biologics in the treatment algorithm. We describe, in sequence, the surgical management options, including salvage procedures, for failed treatment of OLTs.
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http://dx.doi.org/10.1016/j.fcl.2021.12.002DOI Listing
June 2022

Terminology for osteochondral lesions of the ankle: proceedings of the International Consensus Meeting on Cartilage Repair of the Ankle.

J ISAKOS 2022 04 14;7(2):62-66. Epub 2022 Jan 14.

Department of Orthopaedics, Sahlgrenska University Hospital, Sahlgrenska Academy, Gothenburg University, Göteborg, Sweden.

Background: The evidence supporting best practice guidelines in the field of cartilage repair of the ankle is based on both low quality and low levels of evidence. Therefore, an international consensus group of experts was convened to collaboratively advance toward consensus opinions based on the best available evidence on key topics within cartilage repair of the ankle. The purpose of this article is to report the consensus statements on "terminology for osteochondral lesions of the ankle" developed at the 2019 International Consensus Meeting on Cartilage Repair of the Ankle.

Methods: Forty-three international experts in cartilage repair of the ankle representing 20 countries were convened and participated in a process based on the Delphi method of achieving consensus. Questions and statements were drafted within four working groups focusing on specific topics within cartilage repair of the ankle, after which a comprehensive literature review was performed, and the available evidence for each statement was graded. Discussion and debate occurred in cases where statements were not agreed on in unanimous fashion within the working groups. A final vote was then held, and the strength of consensus was characterised as follows: consensus, 51%-74%; strong consensus, 75%-99%; unanimous, 100%.

Results: A total of 11 statements on terminology and classification reached consensus during the 2019 International Consensus Meeting on Cartilage Repair of the Ankle. Definitions are provided for osseous, chondral and osteochondral lesions, as well as bone marrow stimulation and injury chronicity, among others. An osteochondral lesion of the talus can be abbreviated as OLT.

Conclusions: This international consensus derived from leaders in the field will assist clinicians with the appropriate terminology for osteochondral lesions of the ankle.
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http://dx.doi.org/10.1016/j.jisako.2021.12.001DOI Listing
April 2022

Significant variations in surgical construct and return to sport protocols with syndesmotic injuries: an ISAKOS global perspective.

J ISAKOS 2022 02 17;7(1):13-18. Epub 2021 Nov 17.

Duke University School of Medicine, Department of Orthopedic Surgery, Durham, NC, USA.

Objectives: Although the body of literature on syndesmosis injuries is growing with regard to both the biomechanics and clinical outcomes for various fixation constructs, there is little consensus on the optimal treatment and return to sport strategy for these injuries. We endeavoured to assess the current approaches to managing syndesmotic injuries through a Research Electronic Data Capture survey.

Methods: The survey consisted of 27 questions, including respondent demographics, indications for treatment of syndesmotic injuries, preferred treatment and technique, and postoperative management. Responses were generated through six different athlete scenarios: moderate impact, high impact, and very high impact athletes with/without complete deltoid injury. Frequencies and percentages were calculated for all categorical responses.

Results: A total of 742 providers responded to the survey, including 457 American surgeons and 285 members of various international societies. Flexible devices were the preferred fixation construct (47.1%), followed by screws (29.6%), hybrid fixation (e.g. combination of flexible device and screw, 18%), and other (5.3%). Sixty-four percent of respondents noted that their rehabilitation protocols would not change for each athlete scenario. Considerable variability was present in anticipated return to full participation, largely dependent on the presence or absence of a deltoid ligament injury.

Conclusion: The most common elements used as surgical indications were syndesmosis widening > 2 mm on x-ray, an anterior inferior talofibular ligament injury in combination with a posterior inferior talofinular ligament or deltoid ligament involvement on magnetic resonance imaging, and widening of the distal tibiofibular joint during arthroscopic evaluation. Overall, flexible fixation (e.g. suture button) was the preferred device choice for the repair of an injured syndesmosis. Most respondents did not alter their rehab protocol or anticipated return to play timeline based on the injury severity. However, there was considerable variability between respondents on the time to weight-bearing, running, and full participation. Further pragmatic outcomes data are necessary to guide safe return to play protocols for syndesmotic injuries.

Level Of Evidence: Level IV.
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http://dx.doi.org/10.1016/j.jisako.2021.10.005DOI Listing
February 2022

Usability evaluation of an interactive leg press training robot for children with neuromuscular impairments.

Technol Health Care 2022 Mar 18. Epub 2022 Mar 18.

Institute for Rehabilitation and Performance Technology, Bern University of Applied Sciences, Burgdorf, Switzerland.

Background: The use of robotic technology for neurorehabilitative applications has become increasingly important for adults and children with different motor impairments.

Objective: The aim of this study was to evaluate the technical feasibility and usability of a new interactive leg-press training robot that was developed to train leg muscle strength and control, suitable for children with neuromuscular impairments.

Methods: An interactive robotic training system was designed and constructed with various control strategies, actuators and force/position sensors to enable the performance of different training modes (passive, active resistance, and exergames). Five paediatric patients, aged between 7 and 16 years (one girl, age 13.0 ± 3.7 years, [mean ± SD]), with different neuromuscular impairments were recruited to participate in this study. Patients evaluated the device based on a user satisfaction questionnaire and Visual Analog Scale (VAS) scores, and therapists evaluated the device with the modified System Usability Scale (SUS).

Results: One patient could not perform the training session because of his small knee range of motion. Visual Analog Scale scores were given by the 4 patients who performed the training sessions. All the patients adjudged the training with the interactive device as satisfactory. The average SUS score given by the therapists was 61.2 ± 18.4.

Conclusion: This study proposed an interactive lower limb training device for children with different neuromuscular impairments. The device is deemed feasible for paediatric rehabilitation applications, both in terms of technical feasibility and usability acceptance. Both patients and therapists provided positive feedback regarding the training with the device.
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http://dx.doi.org/10.3233/THC-213629DOI Listing
March 2022

Diagnostic Accuracy of the Progressive Collapsing Foot Deformity (PCFD) Classification.

Foot Ankle Int 2022 Jun 18;43(6):800-809. Epub 2022 Mar 18.

Department of Orthopaedic Surgery, University of Colorado School of Medicine, Denver, CO, USA.

Background: A consensus group recently proposed the term (PCFD) and a new classification with 2 stages plus 5 classes to describe the complex array of flatfoot deformities. This study aimed to validate different diagnostic accuracy rates of the PCFD classification.

Methods: This was a survey-based study distributed among 13 foot and ankle fellowship programs for 3 groups of participants with varied experience in practice (group 1: fellows in training, group 2: surgeons in practice for 1-4 years, and group 3: surgeons in practice for ≥5 years). Each participant was asked to assign 20 different cases of flatfoot deformity to the appropriate classes and stages using the PCFD classification. The overall diagnostic accuracy, class, and stage diagnostic accuracy rates for the 20 cases were calculated first for the entire cohort and then compared among the 3 groups. The misdiagnosis rate for each class of deformity (the sum of overdiagnosis and underdiagnosis rates) of the entire cohort was calculated and compared with the other classes. Mean and standard evidence were used to describe numerical data. One-way analysis of variance was used to compare values among the 3 groups and the 5 classes. <.05 was considered statistically significant.

Results: For the whole cohort, the overall diagnostic accuracy, class diagnostic accuracy, and stage diagnostic accuracy rates were 71.0%, 78.3%, and 81.7%, respectively There was a statistically significant difference between group 1 and 2, and group 1 and 3, in overall diagnostic accuracy and class diagnostic accuracy, with no significant difference among the 3 groups regarding stage diagnostic accuracy. Class B had a significantly higher overdiagnosis rate than the rest of the classes, whereas class D was significantly underdiagnosed than others. The misdiagnosis rates for classes A to E were 3.3%, 17.5%, 11.1%, 26.0%, and 3.7%, respectively.

Conclusion: The PCFD classification showed overall fair diagnostic accuracy rates. The highest diagnostic accuracy was for "hindfoot valgus deformity" and "ankle instability." Further content validation of the PCFD classification is needed to examine the terminology and interpretation of those classes with low diagnostic accuracy including "midfoot/forefoot abduction deformity," "forefoot varus deformity/medial column instability," and "peritalar subluxation/dislocation." Level II, prospective comparative study.
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http://dx.doi.org/10.1177/10711007221078000DOI Listing
June 2022

Analysis of Postoperative Gait, Hip Strength, and Patient-Reported Outcomes After OTA/AO 61-B and 61-C Pelvic Ring Injuries.

J Orthop Trauma 2022 Sep;36(9):432-438

Department of Orthopedics, University of Colorado, Aurora, CO.

Objectives: To examine clinical gait parameters, hip muscle strength, pelvic functional outcomes, and psychological outcomes after surgical fixation of OTA/AO 61-B and 61-C pelvic ring injuries.

Design: Retrospective review identified 10 OTA/AO 61-B patients and 9 OTA/AO 61-C patients for recruitment who were between 1 and 5 years after pelvic fixation. Gait and strength assessments, and patient-reported outcome scores were performed/collected and analyzed.

Setting: Outpatient clinical motion performance laboratory.

Patients/participants: Patients with OTA/AO 61-B and OTA/AO 61-C fractures who were between 1 and 5 years after pelvic fixation.

Main Outcome Measurements: Hip strength, kinetics, and spatial-temporal outcomes; Majeed Pelvic Outcome Score; Short Form 36; Hamilton Anxiety/Depression Rating Scales.

Results: There were no differences in age, body mass index, or time since definitive fixation between OTA/AO 61-B and 61-C groups. The OTA/AO 61-C group had higher median injury severity scores, longer length of stay, and greater postoperative pelvic fracture displacement. There was no difference in bilateral hip strength, bilateral peak hip moments, peak hip power, and walking speed between groups. Patients with OTA/AO 61-C fractures had lower scores on Short Form 36 General Health and Majeed Work, with a trend toward a lower Total Majeed score. There were no differences in self-reported total anxiety and depression symptoms.

Conclusions: This study did not identify any gait, strength, or psychological differences between OTA/AO 61-B and 61-C injuries at 1-5 years of follow-up. However, increased injury severity in OTA/AO 61-C patients may have residual consequences on perceived general health and ability to work. This pilot study establishes a template for future research into functional recovery of patients with severe pelvic ring trauma.

Level Of Evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.
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http://dx.doi.org/10.1097/BOT.0000000000002359DOI Listing
September 2022

Osteochondral Lesions of the Tibial Plafond and Ankle Instability With Ankle Cartilage Lesions: Proceedings of the International Consensus Meeting on Cartilage Repair of the Ankle.

Foot Ankle Int 2022 03 5;43(3):448-452. Epub 2022 Jan 5.

Background: An international consensus group of experts was convened to collaboratively advance toward consensus opinions based on the best available evidence on key topics within cartilage repair of the ankle. The purpose of this article is to present the consensus statements on osteochondral lesions of the tibial plafond (OLTP) and on ankle instability with ankle cartilage lesions developed at the 2019 International Consensus Meeting on Cartilage Repair of the Ankle.

Methods: Forty-three experts in cartilage repair of the ankle were convened and participated in a process based on the Delphi method of achieving consensus. Questions and statements were drafted within 4 working groups focusing on specific topics within cartilage repair of the ankle, after which a comprehensive literature review was performed and the available evidence for each statement was graded. Discussion and debate occurred in cases where statements were not agreed on in unanimous fashion within the working groups. A final vote was then held.

Results: A total of 11 statements on OLTP reached consensus. Four achieved unanimous support and 7 reached strong consensus (greater than 75% agreement). A total of 8 statements on ankle instability with ankle cartilage lesions reached consensus during the 2019 International Consensus Meeting on Cartilage Repair of the Ankle. One achieved unanimous support, and seven reached strong consensus (greater than 75% agreement).

Conclusion: These consensus statements may assist clinicians in the management of these difficult clinical pathologies.

Level Of Evidence: Level V, mechanism-based reasoning.
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http://dx.doi.org/10.1177/10711007211049169DOI Listing
March 2022

Heart rate control using first- and second-order models during treadmill exercise.

Syst Sci Control Eng 2021 16;9(1):651-662. Epub 2021 Sep 16.

Institute for Rehabilitation and Performance Technology, Division of Mechanical Engineering, Department of Engineering and Information Technology, Bern University of Applied Sciences, Burgdorf, Switzerland.

Heart rate control using first- and second-order models was compared using a novel control design strategy which shapes the input sensitivity function. Ten participants performed two feedback control test series on a treadmill with square wave and constant references. Using a repeated measures, counterbalanced study design, each series compared controllers C1 and C2 based on first- and second-order models, respectively. In the first series, tracking accuracy root-mean-square tracking error (RMSE) was not significantly lower for C2: 2.59 bpm vs. 2.69 bpm (mean, C1 vs. C2),  = 0.79. But average control signal power was significantly higher for C2: vs. , . In the second series, RMSE was also not significantly lower for C2: 1.99 bpm vs. 1.94 bpm,  = 0.39; but average control signal power was again significantly higher for C2: vs. ,  = 0.045. The results provide no evidence that controllers based on second-order models lead to better tracking accuracy, despite the finding that they are significantly more dynamic. Further investigation using a substantially larger sample size is warranted.
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http://dx.doi.org/10.1080/21642583.2021.1976304DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8494276PMC
September 2021

Outcomes of Open Versus Arthroscopic Broström Surgery for Chronic Lateral Ankle Instability: A Systematic Review and Meta-analysis of Comparative Studies.

Orthop J Sports Med 2021 Jul 21;9(7):23259671211015207. Epub 2021 Jul 21.

Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar.

Background: Nearly 20% of acute ankle sprains progress to chronic lateral ankle instability that requires surgical intervention. In recent years, there has been a growing interest in arthroscopic Broström techniques as an alternative to open surgery.

Purpose: To review the most up-to-date evidence comparing the outcomes of open and arthroscopic Broström procedures for chronic lateral ankle instability.

Study Design: Systematic review; Level of evidence, 3.

Methods: This review was performed following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Relevant comparative studies in English up to May 2020 were identified. The primary outcomes were (1) functional scores (Karlsson Ankle Function Score and American Orthopaedic Foot & Ankle Society [AOFAS] score) and (2) the 10-point visual analog scale (VAS) score for pain. The secondary outcomes were differences in (1) postoperative anterior drawer and talar tilt, (2) surgical time and complication rate, and (3) time to return to sports and weightbearing.

Results: A total of 408 patients in 8 studies met the inclusion criteria. Of these, 193 (47.3%) patients underwent open surgery, while 215 (52.7%) patients underwent arthroscopic surgery. There were significant differences between the open and arthroscopic repair groups in mean 6-month AOFAS scores (82.4 vs 92.25, respectively; mean difference [MD], 11.36; 95% CI, 0.14-2.56; = 90%; = .03), 1-year AOFAS scores (80.05 vs 88.6; MD, -11.96; 95% CI, -21.26 to -2.76; = 82%; = .01), 6-month VAS scores (1.7 vs 1.4; MD, -0.38; 95% CI, -0.54 to -0.21; = 78%; < .001), and 1-year VAS scores (2.05 vs 1.45; MD, 0.31; 95% CI, 0.09-0.54; = 0%; < .001). The mean time to weightbearing was 14.25 and 9.0 weeks in the open and arthroscopic repair groups, respectively (MD, 1.89; 95% CI, 1.24-2.54; = 99%; < .001). There were no statistically significant differences in the remaining outcomes evaluated.

Conclusion: While technically more demanding, arthroscopic Broström was superior to open Broström-Gould surgery in postoperative AOFAS scores, VAS pain scores, and time to return to weightbearing. The operative time, complication rate, talar tilt, and anterior drawer tests were excellent and statistically comparable. Long-term clinical trials are required before recommending arthroscopic Broström as the new gold standard.
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http://dx.doi.org/10.1177/23259671211015207DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8299886PMC
July 2021

Development of an Active Cable-Driven, Force-Controlled Robotic System for Walking Rehabilitation.

Front Neurorobot 2021 21;15:651177. Epub 2021 May 21.

Division of Mechanical Engineering, Department of Engineering and Information Technology, Institute for Rehabilitation and Performance Technology, Bern University of Applied Sciences, Burgdorf, Switzerland.

In a parallel development to traditional rigid rehabilitation robotic systems, cable-driven systems are becoming popular. The robowalk expander product uses passive elastic bands in the training of the lower limbs. However, a well-controlled assistance or resistance is desirable for effective walking relearning and muscle training. To achieve well-controlled force during locomotion training with the robowalk expander, we replaced the elastic bands with actuator-driven cables and implemented force control algorithms for regulation of cable tensions. The aim of this work was to develop an active cable-driven robotic system, and to evaluate force control strategies for walking rehabilitation using frequency-domain analysis. The system parameters were determined through experiment-assisted simulation. Then force-feedback lead controllers were developed for static force tracking, and velocity-feedforward lead compensators were implemented to reduce velocity-related disturbances during walking. The technical evaluation of the active cable-driven robotic system showed that force-feedback lead controllers produced satisfactory force tracking in the static tests with a mean error of 5.5%, but in the dynamic tests, a mean error of 13.2% was observed. Further implementation of the velocity-feedforward lead compensators reduced the force tracking error to 9% in dynamic tests. With the combined control algorithms, the active cable-driven robotic system produced constant force within the four cables during walking on the treadmill, with a mean force-tracking error of 10.3%. This study demonstrates that the force control algorithms are technically feasible. The active cable-driven, force-controlled robotic system has the potential to produce user-defined assistance or resistance in rehabilitation and fitness training.
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http://dx.doi.org/10.3389/fnbot.2021.651177DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8176959PMC
May 2021

A Comprehensive Primer for Quality Assessment in Orthopaedic Surgery: Quality Measures, Payment Programs, and Registries.

J Am Acad Orthop Surg 2021 Aug;29(16):e794-e804

From the Department of Orthopedic Surgery, University of Colorado School of Medicine, Aurora, CO.

Practicing orthopaedic surgeons are subject to both the requirement and the opportunity to participate in individual or group quality assessment, quality-based payment programs, and clinical data registries. An important limitation to participating in and receiving the benefits of quality measuring activities and programs is the lack of a current resource outlining quality assessment models, current quality metrics, and the presence and function of current quality programs, payment models, and active orthopaedic registries. This article is intended as a primer for the practicing orthopaedic surgeon and orthopaedic groups. We provide a detailed overview of current quality metric databases, their categorization and use, and orthopaedic surgeon's role in creating and shaping the definition of quality care and outcomes assessment in the future.
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http://dx.doi.org/10.5435/JAAOS-D-20-01311DOI Listing
August 2021

Identification of heart rate dynamics during treadmill exercise: comparison of first- and second-order models.

Biomed Eng Online 2021 Apr 21;20(1):37. Epub 2021 Apr 21.

Department of Engineering and Information Technology, Division of Mechanical Engineering, Institute for Rehabilitation and Performance Technology, Bern University of Applied Sciences, 3400, Burgdorf, Switzerland.

Background: Characterisation of heart rate (HR) dynamics and their dependence on exercise intensity provides a basis for feedback design of automatic HR control systems. This work aimed to investigate whether the second-order models with separate Phase I and Phase II components of HR response can achieve better fitting performance compared to the first-order models that do not delineate the two phases.

Methods: Eleven participants each performed two open-loop identification tests while running at moderate-to-vigorous intensity on a treadmill. Treadmill speed was changed as a pseudo-random binary sequence (PRBS) to excite both the Phase I and Phase II components. A counterbalanced cross-validation approach was implemented for model parameter estimation and validation.

Results: Comparison of validation outcomes for 22 pairs of first- and second-order models showed that root-mean-square error (RMSE) was significantly lower and fit (normalised RMSE) significantly higher for the second-order models: RMSE was 2.07 bpm ± 0.36 bpm vs. 2.27 bpm ± 0.36 bpm (bpm = beats per min), second order vs. first order, with [Formula: see text]; fit was [Formula: see text]% vs. [Formula: see text]%, [Formula: see text].

Conclusion: Second-order models give significantly better goodness-of-fit than first-order models, likely due to the inclusion of both Phase I and Phase II components of heart rate response. Future work should investigate alternative parameterisations of the PRBS excitation, and whether feedback controllers calculated using second-order models give better performance than those based on first-order models.
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http://dx.doi.org/10.1186/s12938-021-00875-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8059023PMC
April 2021

High-Energy Achilles Tendon Rupture With Associated Medial Malleolus Fracture and Traumatic Peroneal Dislocation: A Case Report.

Foot Ankle Spec 2021 Oct 25;14(5):438-444. Epub 2021 Feb 25.

UCHealth Steadman Hawkins Clinic, Denver, Colorado.

Fracture, Achilles tendon rupture, or traumatic dislocation of the peroneal tendons are often seen in isolation after a trauma or sports-related injury. However, in rare circumstances, a combination of these injuries can occur simultaneously. Multiple previous case reports describe a combination of 2 of these injuries. Missed or delayed diagnosis is common in these combination injuries and can lead to significant patient morbidity and result in long-term consequences. We report a case of a 35-year-old man who sustained an Achilles tendon rupture with an associated medial malleolus fracture and traumatic peroneal dislocation after a snowboarding injury. These injuries were treated surgically, and at 9 months postoperatively, the patient had returned to all activities. Clinicians should have a high index of suspicion for concomitant injuries with higher-energy trauma to the ankle and should perform a thorough history, physical examination, and plain radiographs at a minimum. LEVEL 5.
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http://dx.doi.org/10.1177/1938640021997285DOI Listing
October 2021

Open Brostrom for Lateral Ligament Stabilization.

Curr Rev Musculoskelet Med 2020 Dec 7;13(6):788-796. Epub 2020 Nov 7.

Department of Orthopedic Surgery, University of Colorado, Aurora, USA.

Purpose Of Review: Lateral ankle ligament sprains are one of the most commonly reported injuries in high-level athletes and the general population. Unfortunately, up to 40% of these can go on to develop chronic lateral ankle instability which in the right circumstances requires surgical intervention. The purpose of this review is to present the gold standard surgical treatment for chronic lateral instability with anatomic ligament repair and to highlight the techniques, outcomes, and importance of anatomy when considering surgical treatment.

Recent Findings: Recent and remote literature agrees that the initial treatment for chronic ankle instability is non-operative rehabilitation. In the cases where this fails, the gold standard of surgical treatment is open anatomic repair using the Brostrom-Gould technique which stands out as having very good results over the course of time. Recent studies have shown equally good outcomes with arthroscopy as well as with internal brace devices, and both techniques show potential for earlier rehabilitation. In those with contraindications for anatomic repair including innate soft tissue laxity, high BMI, and in the revision setting, anatomic ligament reconstruction is an appropriate surgical option. Open modified Brostrom lateral ligament repair continues to be the preferred method of surgical treatment for chronic lateral ligament instability. In the setting of new modifications and techniques, long-term outcome studies are necessary to identify both their usefulness in long term and to compare them to the open surgery outcomes. It would be useful to standardize rehabilitation protocols as well as return to sport metrics in order to better evaluate outcomes moving forward.
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http://dx.doi.org/10.1007/s12178-020-09679-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7661567PMC
December 2020

Biomechanical Comparison of All-Soft Suture Anchor Single-Row vs Double-Row Bridging Construct for Insertional Achilles Tendinopathy.

Foot Ankle Int 2021 Feb 8;42(2):215-223. Epub 2020 Oct 8.

Department of Orthopaedic Surgery, University of Colorado School of Medicine, Aurora, CO, USA.

Background: Two common operative fixation techniques for insertional Achilles tendinopathy are the use of all-soft suture anchors vs synthetic anchors with a suture bridge. Despite increasing emphasis on early postoperative mobilization, the biomechanical profile of these repairs is not currently known. We hypothesized that the biomechanical profiles of single-row all-soft suture anchor repairs would differ when compared to double-row suture bridge repairs.

Methods: Achilles tendons were detached from their calcaneal insertions on 6 matched-pair, fresh-frozen cadaver through-knee amputation specimens. Group 1 underwent a single-row repair with all-soft suture anchors. Group 2 was repaired with a double-row bridging suture bridge construct. Achilles-calcaneal displacement was tracked while specimens were cyclically loaded from 10 to 100 N for 2000 cycles and then loaded to failure. Linear mixed models were used to analyze the independent effects of age, body mass index, tendon morphology, repair construct, and footprint size on clinical and ultimate failure loads, Achilles-calcaneal displacement, and mode of failure.

Results: The suture bridge group was independently associated with an approximately 50-N increase in the load to clinical failure (defined as more than 5 mm tendon displacement). There was no difference in ultimate load to failure or tendon/anchor displacement between the 2 groups.

Conclusion: This cadaveric study found that a double-row synthetic bridge construct had less displacement during cyclic loading but was not able to carry more load before clinical failure when compared to a single-row suture anchor construct for the operative repair of insertional Achilles tendinopathy.

Clinical Relevance: Our data suggest that double-row suture bridge constructs increase the load to clinical failure for operative repairs of insertional Achilles tendinopathy. It must be noted that these loads are well below what occurs during gait and the repair must be protected postoperatively without early mobilization. This study also identified several clinical factors that may help predict repair strength and inform further research.
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http://dx.doi.org/10.1177/1071100720959023DOI Listing
February 2021

Technical feasibility of constant-load and high-intensity interval training for cardiopulmonary conditioning using a re-engineered dynamic leg press.

BMC Biomed Eng 2019 3;1:26. Epub 2019 Oct 3.

Institute for Rehabilitation and Performance Technology, Division of Mechanical Engineering, Department of Engineering and Information Technology, Bern University of Applied Sciences, Burgdorf, CH-3400 Switzerland.

Background: Leg-press devices are one of the most widely used training tools for musculoskeletal strengthening of the lower-limbs, and have demonstrated important cardiopulmonary benefits for healthy and patient populations. Further engineering development was done on a dynamic leg-press for work-rate estimation by integrating force and motion sensors, power calculation and a visual feedback system for volitional work-rate control. This study aimed to assess the feasibility of the enhanced dynamic leg press for cardiopulmonary exercise training in constant-load training and high-intensity interval training. Five healthy participants aged 31.0±3.9 years (mean ± standard deviation) performed two cardiopulmonary training sessions: constant-load training and high-intensity interval training. Participants carried out the training sessions at a work rate that corresponds to their first ventilatory threshold for constant-load training, and their second ventilatory threshold for high-intensity interval training.

Results: All participants tolerated both training protocols, and could complete the training sessions with no complications. Substantial cardiopulmonary responses were observed. The difference between mean oxygen uptake and target oxygen uptake was 0.07±0.34 L/min (103 ±17%) during constant-load training, and 0.35±0.66 L/min (113 ±27%) during high-intensity interval training. The difference between mean heart rate and target heart rate was -7±19 bpm (94 ±15%) during constant-load training, and 4.2±16 bpm (103 ±12%) during high-intensity interval training.

Conclusions: The enhanced dynamic leg press was found to be feasible for cardiopulmonary exercise training, and for exercise prescription for different training programmes based on the ventilatory thresholds.
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http://dx.doi.org/10.1186/s42490-019-0025-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7422513PMC
October 2019

Dynamic Loading Assessment at the Fifth Metatarsal in Elite Athletes With a History of Jones Fracture.

Clin J Sport Med 2021 11;31(6):e321-e326

Department of Orthopedics, University of Colorado School of Medicine, Aurora, Colorado; and.

Objective: We hypothesize that athletes who have suffered Jones fractures will apply significantly higher loads at the fifth metatarsal base during athletic activities compared with matched uninjured athletes.

Design: Sixteen athletes were recruited to participate. Eight athletes had a history of Jones fracture, and 8 age, gender, and position-matched athletes without a history of foot injury were recruited as controls.

Setting: Institutional study at Stanford University.

Participants: Sixteen athletes with/without a history of foot injury from Stanford University.

Interventions: Athletes performed a standardized series of movements while wearing calibrated, wireless pressure mapping insoles, and then again with their custom corrective insoles.

Main Outcome Measures: Peak pressure, mean pressure, maximum force, and force-time integral (ie, impulse) were recorded for each activity.

Results: Athletes with a history of Jones fracture showed a significantly increased peak pressure (183 ± 23 vs 138 ± 7 kPA), mean pressure (124 ± 14 vs 95 ± 4 kPA), and maximum force (15 ± 1.2 vs 12 ± 1.2%BW) at the fifth metatarsal base during walking and running compared with uninjured matched controls (all P < 0.05).

Conclusions: Athletes with a history of Jones fracture exert significantly increased peak and mean forces at the base of the fifth metatarsal during common athletic activities. Custom orthoses do not seem to offload this region in all cases. Increased loads may contribute to the development of stress injury to the fifth metatarsal during repetitive loading, and ultimately fracture of the bone.
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http://dx.doi.org/10.1097/JSM.0000000000000830DOI Listing
November 2021

Normal Kinematics of the Syndesmosis and Ankle Mortise During Dynamic Movements.

Foot Ankle Orthop 2020 Jul 26;5(3):2473011420933007. Epub 2020 Aug 26.

Center for Orthopaedic Biomechanics, Department of Mechanical and Materials Engineering, The University of Denver, Denver, CO, USA.

Background: Documenting the healthy articulation of the syndesmosis and talocrural joints, and measurement of 3D medial and lateral clear spaces may improve diagnostic and treatment guidelines for patients suffering from severe syndesmotic injury or chronic instability. This study aimed to define the range of motion (ROM) and displacement of the fibula and talus during static and dynamic activities, and measure the 3D movement in the tibiofibular (syndesmosis) and medial clear space.

Methods: Six healthy volunteers performed dynamic weightbearing motions on a single-leg: heel-rise, squat, torso twist, and box jump. Participants posed in a nonweightbearing neutral stance as well as weightbearing neutral standing, plantarflexion, and dorsiflexion. High-speed stereoradiography measured 3D rotation and translation of the fibula and talus throughout each task. Medial clear space and tibiofibular gap distances were measured under each condition.

Results: Total ROM for the fibula was greatest in internal-external rotation (9.3 ± 3.5 degrees), and anteroposterior (3.3 ± 2.2 mm) and superior-inferior (2.5 ± 0.9 mm) translation, rather than lateral widening (1.7 ± 1.0 mm). The total rotational ROM of the talus was greatest in dorsiflexion-plantarflexion (34.7 ± 12.9 degrees) and internal-external rotation (15.0 ± 3.4 degrees). Single-leg squatting increased the lateral clear space ( = .045) and widened the medial tibiofibular joint, whereas single-leg heel-rises decreased the lateral clear space ( = .001) and widened the tibiotalar space. Gap spaces in the tibiofibular and medial clear spaces did not exceed 2.3 ± 0.9 mm and 2.7 ± 1.2 mm, respectively.

Conclusion: These data support a potential shift in the clinical understanding of fibula displacements during dynamic activities and how implant device constructs might be developed to restore physiologic mechanics.

Clinical Relevance: Syndesmosis stabilization and rehabilitation should consider restoration of normal physiologic rotation and translation of the fibula and ankle mortise rather than focusing solely on the restriction of lateral translation.
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http://dx.doi.org/10.1177/2473011420933007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8697205PMC
July 2020

Acute Fulminant Myocarditis in a Pediatric Patient With COVID-19 Infection.

Pediatrics 2020 08;146(2)

Ochsner Hospital for Children, New Orleans, Louisiana; and

The majority of patients with coronavirus disease 2019 (COVID-19) display pulmonary disease; however, a significant portion of patients have cardiac injury as well, with a high incidence of myocarditis documented in the adult population. Pediatric disease from COVID-19 has been relatively rare, and no cases of virus-related cardiac disease have been published. We present a case of an adolescent girl with fulminant myocarditis with complete heart block, elevated troponin I levels, and severely depressed systolic function in the setting of COVID-19 infection.
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http://dx.doi.org/10.1542/peds.2020-1509DOI Listing
August 2020

Preliminary development and technical evaluation of a belt-actuated robotic rehabilitation platform.

Technol Health Care 2021 ;29(3):595-607

Institute for Rehabilitation and Performance Technology IRPT, Division of Mechanical Engineering, Department of Engineering and Information Technology, Bern University of Applied Sciences, Burgdorf, Switzerland.

Background: To provide effective rehabilitation in the early post-injury stage, a novel robotic rehabilitation platform is proposed, which provides full-body arm-leg rehabilitation via belt actuation to severely disabled patients who are restricted to bed rest.

Objective: To design and technically evaluate the preliminary development of the rehabilitation platform, with focus on the generation of various leg movements.

Methods: Two computer models were developed by importing the components from SolidWorks into Simscape Multibody in MATLAB. This allowed simulation of various stepping movements in supine-lying and side-lying positions. Two belt-actuated test rigs were manufactured and automatic control programs were developed in TIA Portal. Finally, the functionality of the test rigs was technically evaluated.

Results: Computer simulation yielded target positions for the generation of various stepping movements in the experimental platforms. The control system enabled the two-drive test rig to provide three modes of stepping in a supine position. In addition, the four-drive test rig produced walking-like stepping in a side-lying position.

Conclusions: This work confirmed the feasibility of the mechanical development and control system of the test rigs, which are deemed applicable for further development of the overall novel robotic rehabilitation platform.
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http://dx.doi.org/10.3233/THC-202392DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8203225PMC
September 2021

In Fibular Fractures with Associated Syndesmotic Injury, Open Reduction and Internal Fixation with the TightRope Device Reduced Malreduction at 3 Months Compared with Screw Fixation.

Authors:
Kenneth J Hunt

J Bone Joint Surg Am 2020 08;102(16):1465

Department of Orthopaedics, University of Colorado Denver, Denver, Colorado.

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http://dx.doi.org/10.2106/JBJS.20.00992DOI Listing
August 2020

A Consensus Statement on the Surgical Treatment of Charcot-Marie-Tooth Disease.

Foot Ankle Int 2020 07 1;41(7):870-880. Epub 2020 Jun 1.

Cedars-Sinai Medical Center, Los Angeles, CA, USA.

Background: Charcot-Marie-Tooth (CMT) disease is a hereditary motor-sensory neuropathy that is often associated with a cavovarus foot deformity. Limited evidence exists for the orthopedic management of these patients. Our goal was to develop consensus guidelines based upon the clinical experiences and practices of an expert group of foot and ankle surgeons.

Methods: Thirteen experienced, board-certified orthopedic foot and ankle surgeons and a neurologist specializing in CMT disease convened at a 1-day meeting. The group discussed clinical and surgical considerations based upon existing literature and individual experience. After extensive debate, conclusion statements were deemed "consensus" if 85% of the group were in agreement and "unanimous" if 100% were in support.

Conclusions: The group defined consensus terminology, agreed upon standardized templates for history and physical examination, and recommended a comprehensive approach to surgery. Early in the course of the disease, an orthopedic foot and ankle surgeon should be part of the care team. This consensus statement by a team of experienced orthopedic foot and ankle surgeons provides a comprehensive approach to the management of CMT cavovarus deformity.

Level Of Evidence: Level V, expert opinion.
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http://dx.doi.org/10.1177/1071100720922220DOI Listing
July 2020

Editorial Commentary: Living in the Material World: Could Viscoelastic Properties of Sutures Impact Patient Outcomes?

Authors:
Kenneth J Hunt

Arthroscopy 2020 03;36(3):714-715

University of Colorado School of Medicine.

The viscoelastic properties of suture may impact how soft tissue (such as the shoulder rotator cuff tendons) heals to bone and therefore may impact patient outcomes. Thus, it is logical to use suture material less likely to creep and elongate. Suture tape, in particular, may show superior biomechanical properties compared with standard sutures. However, in cadaveric studies, failure generally occurs at the tissue interface, rather than the suture material (or anchor). Thus, the quality and thickness of local tissue must be taken into consideration when determining postoperative rehabilitation or return to activity. Clinical outcome studies comparing suture materials remain elusive, but there is little reason not to use stronger suture material, and this is an option within the surgeon's control.
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http://dx.doi.org/10.1016/j.arthro.2019.12.009DOI Listing
March 2020

Outcomes Following Ankle Fracture Fixation With or Without Ankle Arthroscopy.

Foot Ankle Orthop 2020 Jan 2;5(1):2473011420904046. Epub 2020 Mar 2.

University of Colorado Denver School of Medicine, CO, USA.

Background: Ankle fractures are one of the most common orthopedic injuries, and although most patients have a satisfactory outcome following operative fixation, there are patients that have persistent pain despite anatomic reduction. Intra-articular injuries have been suggested as one potential cause of these suboptimal outcomes. Our study assesses the clinical impact of performing an ankle arthroscopy during ankle fracture open reduction and internal fixation (ORIF).

Methods: This was a retrospective chart review of all patients who underwent operative fixation of a bimalleolar or trimalleolar ankle fracture at our institution from 2014 through 2018. We extracted all demographic data, fracture pattern, operative procedures performed, tourniquet times, arthroscopic findings and any arthroscopic interventions. We then conducted a phone and e-mail survey. Our study included 213 total patients (142 traditional ORIF, 71 ORIF plus arthroscopy) with an average age of 40 years. The average follow-up was 32.4 months with a survey follow-up rate of 50.7% (110/213).

Results: The average tourniquet time for the arthroscopy cohort was 10 minutes longer (89 minutes vs 79 minutes). During the arthroscopy, there was a 28% (20/71) rate of full-thickness osteochondral lesions, 33% (24/71) rate of loose bodies, and a 49% (35/71) rate of partial-thickness cartilage injury. The mean Patient Reported Outcome Information System (PROMIS) physical function score among Weber B fibula fractures was 45.8 and 42.3 in the arthroscopy and nonarthroscopy groups, respectively ( = .012). In addition, the patient satisfaction rate in Weber B fibula fractures was higher in those patients who underwent arthroscopy compared with ORIF alone (93% vs 75%, = .05). Patients who had a tibiotalar joint dislocation at the time of the ankle fracture had a significantly higher PROMIS physical function score (46.6 vs 40.2, = .005) when their surgery included arthroscopy.

Conclusion: Ankle arthroscopy at the time of ORIF led to statistically significant improvements in patient-reported outcomes for Weber B fibula fractures and ankle dislocations. There was no increase in complication rates and the arthroscopy took 10 minutes longer on average.

Level Of Evidence: Level III, retrospective cohort study.
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http://dx.doi.org/10.1177/2473011420904046DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8697299PMC
January 2020

Ankle joint contact loads and displacement in syndesmosis injuries repaired with Tightropes compared to screw fixation in a static model.

Injury 2019 Nov 9;50(11):1901-1907. Epub 2019 Sep 9.

Stanford University Medical Center, Department of Orthopaedic Surgery, 300 Pasteur Drive, Room R144, Stanford, CA, USA.

Background: The effect of syndesmotic fixation on restoration of pressure mechanics in the setting of a syndesmotic injury is largely unknown. The purpose of this study is to examine the contact mechanics of the tibiotalar joint following syndesmosis fixation with screws versus a flexible fixation device for complete syndesmotic injury.

Methods: Six matched pairs of cadaveric below knee specimens were dissected and motion capture trackers were fixed to the tibia, fibula, and talus and a pressure sensor was placed in the tibiotalar joint. Each specimen was first tested intact with axial compressive load followed by external rotation while maintaining axial compression. Next, syndesmotic ligaments were sectioned and randomly assigned to repair with either two TightRopes® or two 3.5 mm cortical screws and the protocol was repeated. Mean contact pressure, peak pressure, reduction in contact area, translation of the center of pressure, and relative talar and fibular motion were calculated. Specimens were then cyclically loaded in external rotation and surviving specimens were loaded in external rotation to failure.

Results: No differences in pressure measurements were observed between the intact and instrumented states during axial load. Mean contact presure relative to intact testing was increased in the screw group at 5 Nm and 7.5 Nm torque. Likewise, peak pressure was increased in the TightRope group at 7.5 Nm torque. There was no change in center of pressure in the TightRope group at any threshold; however, at every threshold tested there was significant medial and anterior translation in the screw group relative to the intact state.

Conclusion: Either screws or TightRope fixation is adequate with AL alone. With lower amounts of torque, the TightRope group appears to have contact and pressure mechanics that more closely match native mechanics.
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http://dx.doi.org/10.1016/j.injury.2019.09.012DOI Listing
November 2019

Congenital Unilateral Hypertrophy of the Foot Intrinsics: A Rare Case and Review of Literature.

J Orthop Case Rep 2019 ;9(2):34-37

Department of Orthopaedics, University of Colorado School of Medicine, Denver, CO, USA.

Introduction: Congenital hypertrophy of the intrinsic muscles of the foot is a rare disorder of unknown incidence characterized by unilateral muscular hypertrophy of one or more of the intrinsic muscles. Few cases have been reported in literature, many presenting with hypertrophy of a single muscle.

Case Report: A 12-year-oldCaucasian female with hypertrophy of all intrinsic muscles of the right foot present since birth presented with muscle imbalance resulting in hammer toe deformities of the second and third toes with the second toe crossing over the hallux. Our treatment consisted of the correction of the toe deformities without muscle debulking or excision.

Conclusions: Isolated congenital hypertrophy of muscles poses a unique challenge, particularly involving musculature of the foot. Indications for intervention include pain or functional impairment. Specific treatments should aim to address patient complaints with the understanding that debulking procedures carry the risk of abundant scar formation, neurovascular injury, and functional deficits.
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http://dx.doi.org/10.13107/jocr.2250-0685.1358DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6727443PMC
January 2019

Robust control of heart rate for cycle ergometer exercise.

Med Biol Eng Comput 2019 Nov 30;57(11):2471-2482. Epub 2019 Aug 30.

Institute for Rehabilitation and Performance Technology, Division of Mechanical Engineering, Department of Engineering and Information Technology, Bern University of Applied Sciences, Burgdorf, CH-3400, Switzerland.

The objective was to assess the performance and robustness of a novel strategy for automatic control of heart rate (HR) during cycle ergometry. Control design used a linear plant model and direct shaping of the closed-loop input-sensitivity function to achieve an appropriate response to disturbances attributable to broad-spectrum heart rate variability (HRV). The controller was evaluated in 73 feedback control experiments involving 49 participants. Performance and stability robustness were analysed using a separately identified family of 73 plant models. The controller gave highly accurate and stable HR tracking performance with mean root-mean-square tracking error between 2.5 beats/min (bpm) and 3.1 bpm, and with low average control signal power. Although plant parameters varied over a very wide range, key closed-loop transfer functions remained invariant to plant uncertainty in important frequency bands, while infinite gain margins and large phase margins (> 62) were preserved across the whole plant model family. Highly accurate, stable and robust HR control can be achieved using LTI controllers of remarkably simple structure. The results highlight that HR control design must focus on disturbances caused by HRV. The input-sensitivity approach evaluated in this work provides a transparent method of addressing this challenge. Graphical Abstract Heart rate control using a cycle ergometer.
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http://dx.doi.org/10.1007/s11517-019-02034-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6828638PMC
November 2019

Identification and comparison of heart-rate dynamics during cycle ergometer and treadmill exercise.

PLoS One 2019 22;14(8):e0220826. Epub 2019 Aug 22.

Institute for Rehabilitation and Performance Technology, Division of Mechanical Engineering, Department of Engineering and Information Technology, Bern University of Applied Sciences, Burgdorf, Switzerland.

Aim And Methods: The aim of this study was to compare the dynamics of heart rate (HR) response to exercise using a cycle ergometer (CE) and a treadmill (TM). Using a sample of 25 healthy male participants, the time constant of HR dynamics was estimated for both modalities in response to square-wave excitation.

Results: The principal finding was that the time constant of heart-rate dynamics around somewhat-hard exercise intensity (Borg rating of perceived exertion = 13) does not differ significantly between the CE and TM (68.7 s ± 21.5 s vs. 62.5 s ± 18.5 s [mean ± standard deviation]; CE vs. TM; p = 0.20). An observed moderate level of evidence that root-mean-square model error was higher for the CE than for the TM (2.5 bpm ± 0.5 bpm vs. 2.2 bpm ± 0.5 bpm, p = 0.059) may reflect a decrease in heart rate variability with increasing HR intensity because, in order to achieve similar levels of perceived intensity, mean heart rate for the CE was ∼25 bpm lower than for the TM.

Conclusion And Significance: These results have important implications for model-based design of automatic HR controllers, because, in principle, the same dynamic controller, merely scaled according to the differing steady-state gains, should be able to be applied to the CE and TM exercise modalities.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0220826PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6705825PMC
March 2020
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