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Background: The response of heart rate to changes in exercise intensity is comprised of several dynamic modes with differing magnitudes and temporal characteristics. Investigations of empirical identification of dynamic models of heart rate showed that second-order models gave substantially and significantly better model fidelity compared to the first order case. In the present work, we aimed to reanalyse data from previous studies to more closely consider the effect of including a zero and a pure delay in the model., Methods: This is a retrospective analysis of 22 treadmill (TM) and 54 cycle ergometer (CE) data sets from a total of 38 healthy participants. A linear, time-invariant plant model structure with up to two poles, a zero and a dead time is considered. Empirical estimation of the free parameters was performed using least-squares optimisation. The primary outcome measure is model fit, which is a normalised root-mean-square model error., Results: A model comprising parallel connection of two first-order transfer functions, one with a dead time and one without, was found to give the highest fit (56.7 % for TM, 54.3 % for CE), whereby the non-delayed component appeared to merely capture initial transients in the data and the part with dead time likely represented the true dynamic response of heart rate to the excitation. In comparison, a simple first-order model without dead time gave substantially lower fit than the parallel model (50.2 % for TM, 47.9 % for CE)., Conclusions: This preliminary analysis points to a linear first-order system with dead time as being an appropriate model for heart rate response to exercise using treadmill and cycle ergometer modalities. In order to avoid biased estimates, it is vitally important that, prior to parameter estimation and validation, careful attention is paid to data preprocessing in order to eliminate transients and trends., Competing Interests: No competing interests were disclosed., (Copyright: © 2024 Hunt KJ and Wang H.)

Background: Three-dimensional weightbearing CT (WBCT) has been widely used to assess foot and ankle alignment. However, most current measurement methods are based on 2-dimensional concepts-distance, long axis, angulation, etc-and are sensitive to changes in orientation of the WBCT images. This study demonstrated how changes in positioning of the image can significantly influence the evaluation of hindfoot alignment., Methods: WBCT scans of 10 feet without deformities were used. In the horizontal view, the long axis of the foot image was aligned to a neutral position and then rotated 5, 10, 15, and 20 degrees both internally and externally to simulate malposition. The Calcaneal Moment Arm (CMA) was measured by 2 investigators independently in the above positions. An intraclass correlation coefficient (ICC) model was used to assess the intra- and interobserver reliabilities. The correlation between the CMA and the rotation angle of the foot images was analyzed using linear regression., Results: The CMA measurements demonstrated that internal rotation of the image changed the neutral hindfoot into valgus, whereas external rotation led to varus. A 1-degree internal or external rotation of the image correlated with 0.48 (±0.03) mm increase or decrease in the modified WBCT-CMA value ( P  < .0001, R 2  = 0.6406)., Conclusion: This study demonstrated that although 3D WBCT provides the ability to observe the foot from different perspectives, current alignment evaluation tools are limited to 2 dimensions. Therefore, positioning the WBCT images in a consistent orientation is important to generate correct data., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. Disclosure forms for all authors are available online.

Hallux rigidus is a common degenerative condition of the hallux metatarsophalangeal joint (MTPJ) characterized by pain, swelling, stiffness, and limited range of motion with characteristic corresponding clinical, physical examination, and radiographic findings. Many historical risks factors including trauma and family history and patient factors including hallux valgus interphalangeus and inflammatory arthropathies have a well-substantiated etiologic role in the disease process. The purpose of this section is to review the normal and pathologic anatomy and biomechanics of the hallux MTPJ while providing an overview of the current understanding and remain debate regarding the disease process., Competing Interests: Disclosure The authors have no pertinent financial or funding disclosures related to the content of this article., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Objective: To investigate the effects of reduced weight running on the antigravity (AG) treadmill on maintenance of normal muscle activation and reduction of plantar forces in healthy subjects., Design: Descriptive laboratory study., Setting: Clinical sports medicine center., Participants: Twenty healthy subjects (10 male and 10 female) aged 18 to 29 years., Independent Variables: Subjects running at 6.5 miles per hour on a standard treadmill and on the AG treadmill at 100%, 90%, 80%, 70%, 60%, and 50% of bodyweight levels., Main Outcome Measures: Dynamic plantar loading data were recorded using pressure insoles. Surface electromyography electrodes with imbedded accelerometers were used to estimate timing and magnitude of muscle activity, stride length, and cadence., Results: There was a significant, sequential reduction in peak pressure, maximum force, and force time integral (FTI) with decreasing bodyweight. A 50% bodyweight reduction resulted in a 51% reduction in maximum force and a 59% reduction in FTI in the heel, as compared with 19% to 28% at the metatarsal heads. There was reduced contact area in the heel and midfoot at and below 70% BW. Lower limb muscle activity decreases with reduced bodyweight while maintain normal muscle recruitment timing., Conclusions: The AG treadmill provides a reduction in loading forces while maintaining normal muscle recruitment patterns. Decreased BW running preferentially unloads the hindfoot. The AG treadmill can be an effective rehabilitation tool following foot or ankle injury and may prove superior to other limited weight-bearing methods., Competing Interests: The authors report no conflicts of interest., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Patients with neurological disorders including stroke use rehabilitation to improve cognitive abilities, to regain motor function and to reduce the risk of further complications. Robotics-assisted tilt table technology has been developed to provide early mobilisation and to automate therapy involving the lower limbs. The aim of this study was to evaluate the feasibility of employing a feedback control system for heart rate (HR) during robotics-assisted tilt table exercise in patients after a stroke., Methods: This feasibility study was designed as a case series with 12 patients ( n = 12 ) with no restriction on the time post-stroke or on the degree of post-stroke impairment severity. A robotics-assisted tilt table was augmented with force sensors, a work rate estimation algorithm, and a biofeedback screen that facilitated volitional control of a target work rate. Dynamic models of HR response to changes in target work rate were estimated in system identification tests; nominal models were used to calculate the parameters of feedback controllers designed to give a specified closed-loop bandwidth; and the accuracy of HR control was assessed quantitatively in feedback control tests., Results: Feedback control tests were successfully conducted in all 12 patients. Dynamic models of heart rate response to imposed work rate were estimated with a mean root-mean-square (RMS) model error of 2.16 beats per minute (bpm), while highly accurate feedback control of heart rate was achieved with a mean RMS tracking error (RMSE) of 2.00 bpm. Control accuracy, i.e. RMSE, was found to be strongly correlated with the magnitude of heart rate variability (HRV): patients with a low magnitude of HRV had low RMSE, i.e. more accurate HR control performance, and vice versa., Conclusions: Feedback control of heart rate during robotics-assisted tilt table exercise was found to be feasible. Future work should investigate robustness aspects of the feedback control system. Modifications to the exercise modality, or alternative modalities, should be explored that allow higher levels of work rate and heart rate intensity to be achieved., (© 2024. The Author(s).)

Objectives: While previous investigations have demonstrated a positive correlation between previous concussion and risk of subsequent lower extremity musculoskeletal injury (LEMSKI), the effect of sport- and patient-specific factors on time to injury has not been thoroughly described. This study's main objective was to evaluate the relationship between prior concussion and time to LEMSKI among a population of collegiate student-athletes. Secondary objectives were to evaluate the relationship between playing surface, sport contact status, and biologic sex on time to LEMSKI. We hypothesized that those with previous concussions, those competing on synthetic surfaces, and those competing in collision sports would experience decreased latency to LEMSKI overall., Methods: A retrospective observational analysis of National Collegiate Athletic Association (NCAA) Division I student-athletes was conducted utilizing a mixed linear model analysis with contrasts. Inclusion criteria included participation in the Pac-12 Health Analytics Program with a documented LEMSKI between 2017 and 2020. Exclusion criteria included concurrent concussion and LEMSKI, injury resulting in serious morbidity or mortality, and incomplete medical record. Participants were classified by whether they sustained a concussion prior to LEMSKI in each athletic season., Results: Of 1179 athletes included, 1140 had no previous concussion and 37 had a previous concussion. There was no observed effect of previous concussion (F ​= ​0.038; p ​= ​0.846) on time to LEMSKI overall. Student-athletes competing on constructed surfaces sustained a subsequent LEMSKI 14.5 days sooner (SE ​= ​5.255; p ​= ​0.045), and those competing on organic surfaces sustained a subsequent LEMSKI 23.5 days sooner (SE ​= ​4.018; p ​< ​0.001) in the season than those competing on synthetic surfaces. Contact sport student-athletes sustained a subsequent LEMSKI 52.1 days sooner than collision sport student-athletes (SE ​= ​5.248; p ​< ​0.001), and limited contact sport student-athletes sustained a subsequent LEMSKI 42.29 days sooner than collision sport student-athletes (SE ​= ​4.463; p ​< ​0.001). There was no observed effect of biologic sex (F ​= ​0.602; p ​= ​0.438) on time to LEMSKI overall., Conclusion: There was no observed impact of concussion on time on LEMSKI overall in this collegiate athletic population. Contact sports were associated with decreased time to LEMSK, while synthetic surfaces were associated with increased time to LEMSKI in this population. There was no observed impact of biologic sex on time to LEMSKI., Level of Evidence: Case-control, level of evidence III., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

Competing Interests: Declaration of Conflicting InterestsThe author declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. Disclosure forms for all authors are available online.

Background: Heart rate variability (HRV) may provide objective information about cardiogenic autonomic balance in individuals with spinal cord injury (SCI). The aim of this study was to characterize the diurnal variation of HRV in individuals with SCI at lesion level T6 and above and lesion level below T6., Methods: This was a retrospective analysis of a prior cross-sectional study. Individuals with chronic SCI underwent 24 h recording of the time between consecutive R waves (RR interval) to derive parameters of HRV as follows: standard deviation of all normal-to-normal R-R intervals (SDNN) and square root of the mean of the squared differences between successive R-R intervals (RMSSD) (time domain); and high frequency power (HF), low-frequency power (LF), very low frequency power (VLF), ultra-low frequency power (ULF) and total power (TP) (frequency domain). Changes in the magnitude of HRV outcomes over the 24 h period were investigated using a novel multi-component cosinor model constrained to the form of a three-harmonic Fourier series., Results: Participants were grouped as lesion level T6 and above (n = 22) or below T6 (n = 36). Most of them were male (n = 40, 69%) and the median age (interquartile range) was 50.5 (28) years. Both groups exhibited similar diurnal patterns in most HRV metrics. The lowest values occurred in the late afternoon (4-6 pm) and gradually increased, peaking around midnight to early morning (1-6 am). Exceptions included RMSSD, which peaked before midnight, and ULF, which showed a double peak pattern that peaked from 11 am to 1 pm and 4-6 am in participants with lesion level at T6 and above. The HRV values in participants with lesion level T6 and above were generally lower than participants with lesion level below T6, except for peak values of RMSSD, HF and LF., Conclusion: This study demonstrated substantial diurnal variation of HRV in participants with SCI in both groups of participants. In clinical and research settings, diurnal variations in HRV must be taken into consideration., (© 2024. The Author(s).)

Total ankle arthroplasty (TAA) is an effective treatment for end-stage ankle arthritis consistently demonstrating good to excellent outcomes, even when considering factors such as deformity, patient age, bilaterality, and arthritis etiology. There is little consensus in the literature with regard to preferred patient-reported outcome metrics (PROMs) for assessing outcomes, although all metrics generally improve following TAA. Several countries have successful registries to track longevity of TAA in populations; however, PROMs are generally not successfully tracked in registries. A trend toward consensus on outcome metrics and collaborative registries is warranted to optimize patient selection and outcomes in TAA., Competing Interests: Disclosure The authors have nothing relevant to disclose., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Background: A previous study showed low reliability of 1-h HRV outcomes in participants with spinal cord injury (SCI), but it was not certain whether the low reliability was due to the unrestricted activity of participants. We aimed to investigate test-retest reliability of HRV metrics in individuals with SCI using a 1-h measurement in a supine position., Methods: Individuals with SCI underwent two sessions of 1-h recording of the time between consecutive R waves (RR-intervals) in a supine position. HRV outcomes were obtained from a single 5-min data segment and for the full 1-h recording. HRV parameters of interest were: standard deviation of all normal-to-normal R-R intervals (SDNN) and square root of the mean of the squared differences between successive R-R intervals (RMSSD) (time domain); and high frequency power (HF), low frequency power (LF), very low frequency power (VLF), ultra-low frequency power (ULF) and total power (TP) (frequency domain). Relative reliability was assessed by intraclass correlation coefficient (ICC). Absolute reliability was assessed by coefficient of variation (CV) and Bland-Altman limits of agreement (LoA)., Results: Data from 37 individuals (14 with tetraplegia and 23 with paraplegia) were included. Relative reliability was higher for the 1-h (ICCs ranged from 0.13-0.71) than for the 5-min duration (ICCs ranged from 0.06-0.50) in the overall SCI group for all HRV metrics. Participants with tetraplegia had lower relative reliability compared to participants with paraplegia in all HRV metrics for the 5-min duration (ICCs ranged from -0.01-0.34 vs . 0.21-0.57). For the 1-h duration, participants with paraplegia showed higher relative reliability than participants with tetraplegia in all HRV metrics (ICCs ranged from 0.18-0.79 vs . 0.07-0.54) except TP (ICC 0.69 vs . 0.82). In terms of absolute reliability, the CVs and LoAs for the 1-h duration were better than for the 5-min duration. In general, time domain metrics showed better reliability than frequency domain metrics for both durations in participants with tetraplegia and paraplegia. The lowest CV and narrowest 95% LoA were found for SDNN in 5-min and 1-h durations overall and in both lesion levels., Conclusions: The supine position did not provide better reliability compared to unrestricted activity in participants with SCI. HRV analysis using a 5-min duration is of limited value in SCI due to poor reliability. For the 1-h analysis duration, interpretation of the reliability of HRV varies according to lesion level: it is recommended to take lesion level into account when interpreting reliability measures., Competing Interests: The authors declare that they have no competing interests., (© 2023 Srirubkhwa et al.)

Study Design: Cross-sectional., Objectives: To investigate test-retest reliability of heart rate variability (HRV) metrics in SCI without restriction of activity over long (24-h) and shorter durations (5-min, 10-min, 1-h, 3-h and 6-h)., Settings: University hospital in Khon Kaen, Thailand., Methods: Forty-five participants (11 with tetraplegia and 34 with paraplegia) underwent two 24-h recordings of RR-intervals to derive time and frequency HRV metrics. Relative reliability was assessed by intraclass correlation coefficient (ICC) and absolute reliability by coefficient of variation (CV) and Bland-Altman limits of agreement (LoA)., Results: For 5- and 10-min durations, eight of eleven HRV metrics had moderate to excellent reliability (ICC 0.40-0.76); the remaining three were poor (ICC < 0.4). HRV values from 1-h and 3-h durations showed moderate to excellent reliability (ICC of 0.46-0.81), except for 1-h reliability of ULF and TP (ICC of 0.06 and 0.30, respectively). Relative reliability was excellent (ICC of 0.77-0.92) for 6-h and 24-h durations in all HRV metrics. Absolute reliability improved as recording duration increased (lower CVs and narrower LoAs). Participants with high AD risk (SCI level at or above T6) showed lower test-retest reliability of HF and LF values than participants with low AD risk., Conclusion: Relative reliability of HRV was excellent for 6-h and 24-h. The best absolute reliability values were for 24-h duration. Time-domain outcomes were more reliable than frequency domain outcomes. Participants with high risk of AD, particularly those with tetraplegia, showed lower reliability, especially for HF and LF., (© 2023. The Author(s).)

This work investigated automatic control of heart rate during treadmill exercise. The aim was to theoretically derive a generic feedback design strategy that achieves a constant input sensitivity function for linear, time-invariant plant models, and to empirically test whether a compensator C2 based on a second-order model is more dynamic and has better tracking accuracy than a compensator C1 based on a first-order model. Twenty-three healthy participants were tested using first and second order compensators, C1 and C2, respectively, during 35-minute bouts of constant heart rate treadmill running. It was found that compensator C2 was significantly more accurate, i.e. it had 7% lower mean root-mean-square tracking error (1.98 vs. 2.13 beats per minute, p = 0.026), and significantly more dynamic, i.e. it had 17% higher mean average control signal power (23.4 × 10-4 m2/s2 vs. 20.0 × 10-4 m2/s2, p = 0.011), than C1. This improvement likely stems from the substantially and significantly better fidelity of second-order models, compared to first order models, in line with classical descriptions of the different phases of the cardiac response to exercise. These outcomes, achieved using a treadmill, are consistent with previous observations for the cycle ergometer exercise modality. In summary, whenever heart rate tracking accuracy is of primary importance and a more dynamic control signal is acceptable, the use of a compensator based on a second-order nominal model is recommended., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Wang, Hunt. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Objectives: To evaluate how ligament augmentation repair (LAR) techniques are currently used in different anatomic regions in orthopaedic sports medicine, and to identify the most common indications and limitations of LAR., Methods: We sent survey invitations to 4,000 members of the International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine society. The survey consisted of 37 questions total, with members only receiving some branching questions specific to their area of specialisation. Data were analysed using descriptive statistics, and the significance between groups was evaluated using chi-square tests of independence., Results: Of 515 surveys received, 502 were complete and included for the analysis (97% completion rate). 27% of respondents report from Europe, 26% South America, 23% Asia, 15% North America, 5.2% Oceania, and 3.4% Africa. 75% of all survey respondents report using LAR, most frequently using it for the anterior talofibular ligament ( 69%), acromioclavicular joint ( 58%), and the anterior cruciate ligament (51%). Surgeons in Asia report using LAR the most (80%), and surgeons in Africa the least (59%). LAR is most commonly indicated for additional stability (72%), poor tissue quality (54%), and more rapid return-to-play (47%). LAR users state their greatest limitation is cost (62%), while non-LAR users state their greatest reason not to use LAR is that patients do well without it (46%). We also find that the frequency of LAR use among surgeons may differ based on practice characteristics and training. For example, surgeons who treat athletes at the professional or Olympic level are significantly more likely to have a high annual use of LAR (20+ cases) compared to surgeons that treat only recreational athletes (45% and 25%, respectively, p ​= ​0.005)., Conclusion: LAR is broadly applied in orthopaedics but its rate of use is not homogeneous. Outcomes and perceived benefits vary depending on factors such as surgeon specialty and treatment population., Level of Evidence: Level V., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Importance: Ligament augmentation techniques (LATs) are surgical procedures, in which an anatomical ligament repair or reconstruction is strengthened with a synthetic material. During the last decade, LATs have increased in prevalence in clinical practice and academic literature. Observing the trends in LAT publications can be used to identify clusters of strong evidence for clinical practice and to highlight areas of the literature which need further development., Objective: This article aims to define ligament augmentation as a technique category, observe anatomical, procedural, and temporal trends in LAT publication, and report on the state of current research in this field., Evidence Review: Primary literature in the English language, which describes ligament augmentation and reports on human, cadaveric, or biomechanical models, and published prior to May 24th, 2022, was targeted for analysis. PubMed, Embase, and Cochrane CENTRAL databases were explored using a focused keyword search strategy, and the resulting publications were reviewed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Data were collected and analysed using descriptive statistics., Findings: Two hundred eighty-three publications reporting ligament augmentation techniques, published from May 1989 to May 2022, were included for final analysis. A wide technical and anatomical variety of procedures are reported. 36.8% of LAT publications describe knee ligaments, among which the anterior cruciate ligamenthas the highest focus in ligament augmentation publications (31.8% of articles). LAT literature has recently expanded in anatomical scope, with many contemporary articles describing the usage of a LAT in the ankle syndesmosis and coracoclavicular ligaments. 60.4% of LAT literature has been published since 2017. There has been an 11% average increase in the rate of LAT publication reports since 2015. Novel fixation devices-suture buttons and suture anchors-have gained wide popularity in the literature., Conclusions and Relevance: In this review, we define LATs and quantitatively describe the expansion of LAT use reported in the literature. This data will provide physicians an overview of the history of these methods, as well as illustrate the broad range of applications available for the use of LATs., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

The aim of this work was to investigate the time and exercise intensity dependence of heart rate variability (HRV). Time-dependent, cardiovascular-drift-related increases in heart rate (HR) were inhibited by enforcing a constant heart rate throughout the exercise with a feedback control system. Thirty-two healthy adults performed HR-stabilised treadmill running exercise at two distinct exercise intensity levels. Standard time and frequency domain HRV metrics were computed and served as outcomes. Significant decreases were detected in 8 of the 14 outcomes for the time dependence analysis and in 6 of the 7 outcomes for the exercise intensity dependence analysis (excluding the experimental speed-signal frequency analysis). Furthermore, metrics that have been reported to reach an intensity-dependent near-zero minimum rapidly (usually at moderate intensity) were found to be near constant over time and only barely decreased with intensity. Taken together, these results highlight that HRV generally decreases with time and with exercise intensity. The intensity-related reductions were found to be greater in value and significance compared to the time-related reductions. Additionally, the results indicate that decreases in HRV metrics with time or exercise intensity are only detectable as long as their metric-specific near-zero minimum has not yet been reached., (© 2023. The Author(s).)

Background: Total ankle arthroplasty through the anterior approach (TAR-AA) is an increasingly popular treatment for ankle arthritis, but it carries a known risk for wound complications. Several products have been investigated to mitigate this risk; however, most are either costly or invasive. Noninvasive skin expansion strips (NSESs) were designed to transfer tension away from the incision and induce new skin growth at the edges of the strips. We hypothesize that postoperative application of NSESs will decrease unplanned clinic visits and wound complications after TAR-AA., Methods: This is a prospective cohort study of 41 patients at a single institution (3 surgeons) treated with NSESs after undergoing TAR-AA. An additional 41 consecutive historical patients treated without NSESs were retrospectively included as a control group. Patients received application of NSESs in the operating room after routine wound closure and again 2 weeks postoperatively. No other changes were made to the surgeons' wound closure technique, immobilization, follow-up timing, or rehabilitation protocols. Primary outcomes included (1) additional clinic visit required for wound assessment or suture removal, (2) superficial wound complication, and (3) deep infection., Results: Baseline demographics did not differ significantly from our 41 consecutively treated historical controls. Additional clinic visits for suture removal or wound evaluation were significantly lower for patients treated with NSESs (15%, 6 of 41) compared to the control group (49%, 20 of 41) ( P = .001). There was also a significant difference in the superficial wound complication rate in the treatment group vs control group, 2% and 12%, respectively ( P = .04). There were no deep infections in either group., Conclusion: Noninvasive skin expansion strips placed after TAR-AA with an anterior approach have the potential to decrease wound complications and unplanned clinic visits. Further high-volume or randomized studies are needed to clarify their cost effectiveness and effect on long-term outcomes., Level of Evidence: Level II, prospective cohort study.

Progressive collapsing foot deformity (PCFD; commonly referred to as flatfoot deformity) is a complex condition classically characterized by hindfoot valgus, midfoot abduction, and forefoot varus. Medial column arthrodesis can be used to reliably correct severe, arthritic, and unstable PCFD involving the medial column. Although both naviculocuneiform arthrodesis and talonavicular arthrodesis have their own indications, patient selection and careful radiographic and clinical assessment are crucial for any medial column arthrodesis. Herein, the authors discuss the indications for medial column arthrodesis procedures, outcomes as reported in the literature, and several case examples using medial column arthrodesis in deformity correction., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Background: End-stage hallux metatarsophalangeal (MTP) joint arthritis is commonly treated with arthrodesis using stainless steel or titanium implants. These implants provide static compression that is maximal at the time of implant insertion. Alternatively, nitinol staples are capable of dynamic compression. They have most frequently been used for midfoot arthrodesis procedures. However, their biomechanical performance during hallux MTP arthrodesis has not been described., Methods: 8 matched pairs of cadaveric feet (4 female, 4 male) were prepared for hallux MTP arthrodesis using cup and cone reamers. Cadaveric pairs were then instrumented with either (1) a transarticular lag screw and dorsal nitinol staple or (2) orthogonal nitinol staples placed dorsally and medially. Walking in a short leg cast for 6 weeks was simulated by applying 90-N forces at 3 Hz to the plantar proximal phalanx for up to 250 000 cycles. Failure was defined as catastrophic implant failure or plantar gapping beyond 7 mm., Results: 15 of 16 specimens failed cyclic loading. All 8 specimens fixed with orthogonal staples failed at an average of 37 ± 81 cycles. 7 of 8 specimens fixed with a dorsal staple and crossed screw failed at 14 900 ± 39 000 cycles. Collectively, 5 specimens failed because of bone fracture (1 in orthogonal staples, 4 in staple-screw group) and 10 failed because of excessive gap formation (7 in orthogonal staples, 3 in staple-screw group). The number of cycles to failure was significantly lower ( P = .0469) in the orthogonal staple constructs compared with the dorsal staple and crossed screw constructs., Conclusion: The tested constructs permit significant motion at the first MTP fusion surface during simulated protected weightbearing. Although multiple in vivo factors should be considered when extrapolating results from this cadaveric study, this motion may result in clinical failure with early postoperative weightbearing protocols., Clinical Relevance: We report the first biomechanical evaluation of hallux MTP arthrodesis using modern nitinol staples in 2 separate constructs.

In order to promote early rehabilitation, we proposed a system which provides full-body arm-leg training for patients in a bed-lying position. As the preliminary development, a platform for leg movement was investigated. An innovative system with four servo drives was designed and manufactured. An artificial leg frame was attached to the platform via belts. The positions of the hip and knee joints were recorded using potentiometers. Closed-loop PID position control algorithms were implemented for production of various stepping movements. Technical evaluation on a test participant showed that the platform tracked the circular trajectory of the foot in a supine-lying position with an area difference of 8.2%, and produced walking-like trajectories in the hip and knee joints in a side-lying position with a mean error of 10.6%. The mechanical structure can be resized, and the control system can be expanded, so as to produce 3-dimensional stepping movement in both arms and legs. This innovative platform combined with the closed-loop position control strategy shows the technical potential to be a promising full-body rehabilitation platform for the patients in the early post-injury stage.

Background: A consensus group recently proposed the term progressive collapsing foot deformity (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. P <.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 of Evidence: Level II, prospective comparative study.

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., (Copyright © 2022 Elsevier Inc. All rights reserved.)

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.

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., Competing Interests: Declaration of competing interest K.J.H. reports other from Panther Orthopaedics, during the conduct of the study; In addition, he has a patent Puma issued. The other authors have no competing interests to declare., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

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.

Background: Interlimb neural coupling implies that arm swing should be included during gait training to improve rehabilitation outcomes. We previously developed several systems for production of walking with arm swing, but the reaction forces on the foot sole during usage of the systems were not satisfactory and there was potential to improve control system performance. This work aimed to design and technically evaluate a novel system for producing walking with synchronised arm and leg movement and with dynamic force loading on the foot soles. Methods: The robotic system included a passive curved treadmill and a trunk frame, upon which the rigs for the upper and lower limbs were mounted. Ten actuators and servocontrollers with EtherCAT communication protocol controlled the bilateral shoulder, elbow, hip, knee and ankle joints. Impedance control algorithms were developed and ran in an industrial PC. Flexible pressure sensors recorded the plantar forces on the foot soles. The criteria of implementation and responsiveness were used to formally evaluate the technical feasibility of the system. Results: Using impedance algorithms, the system produced synchronous walking with arm swing on the curved treadmill, with mean RMS angular tracking error <2° in the 10 joint profiles. The foot trajectories relative to the hip presented similar shapes to those during normal gait, with mean RMS displacement error <1.5 cm. A force pattern that started at the heel and finished at the forefoot was observed during walking using the system, which was similar to the pattern from overground walking. Conclusion: The robotic system produced walking-like kinematics in the 10 joints and in the foot trajectories. Integrated with the curved treadmill, the system also produced walking-like force patterns on the foot soles. The system is considered feasible as far as implementation and responsiveness are concerned. Future work will focus on improvement of the mechanical system for future clinical application., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Fang and Hunt.)

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., Competing Interests: The authors report no conflicts of interest., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

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. Levels of Evidence: LEVEL 5.

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), p  = 0.79. But average control signal power was significantly higher for C2: 11.29 × 10 - 4 m 2 / s 2 vs. 27.91 × 10 - 4 m 2 / s 2 , p = 3.1 × 10 - 10 . In the second series, RMSE was also not significantly lower for C2: 1.99 bpm vs. 1.94 bpm, p  = 0.39; but average control signal power was again significantly higher for C2: 2.20 × 10 - 4 m 2 / s 2 vs. 2.78 × 10 - 4 m 2 / s 2 , p  = 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., Competing Interests: KH and HW designed the study. HW did the data acquisition. HW and KH contributed to the analysis and interpretation of the data. HW wrote the manuscript and KH revised it critically for important intellectual content. Both authors read and approved the final manuscript.No potential conflict of interest was reported by the author(s)., (© 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.)

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., (Copyright © 2021 by the American Academy of Orthopaedic Surgeons.)

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; I 2 = 90%; P = .03), 1-year AOFAS scores (80.05 vs 88.6; MD, -11.96; 95% CI, -21.26 to -2.76; I 2 = 82%; P = .01), 6-month VAS scores (1.7 vs 1.4; MD, -0.38; 95% CI, -0.54 to -0.21; I 2 = 78%; P < .001), and 1-year VAS scores (2.05 vs 1.45; MD, 0.31; 95% CI, 0.09-0.54; I 2 = 0%; P < .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; I 2 = 99%; P < .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., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: T.T. has received hospitality payments from Stryker, NuVasive, Smith & Nephew, Medtronics, and Zimmer Biomet. K.M. has received educational support from Arthrex. K.J.H. has received education payments from Wright Medical Technology, Pacific Medical, and Zimmer Biomet; consulting fees from Paragon 28; nonconsulting fees from Arthrex; and honoraria from Cartiva and has a patent pending and stock options with Panther Orthopaedics. S.A.L. has received grant support from Arthrosurface and Zimmer Biologics; education payments from United Orthopedics and Arthrex; consulting fees from Heron Therapeutics, Stryker, and Arthrosurface; personal fees from Stryker; and hospitality payments from Exactech and has stock options with Medshape. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto., (© The Author(s) 2021.)

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., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Fang, Haldimann, Marchal-Crespo and Hunt.)

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.

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.

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.

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.

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 ( P = .045) and widened the medial tibiofibular joint, whereas single-leg heel-rises decreased the lateral clear space ( P = .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., Competing Interests: Declaration of Conflicting Interests: The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Paul J. Rullkoetter, PhD, reports grants from DePuy Synthes Products, Inc, during the conduct of the study. ICMJE forms for all authors are available online., (© The Author(s) 2020.)

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 ( P = .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%, P = .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, P = .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., Competing Interests: Declaration of Conflicting Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. ICMJE forms for all authors are available online., (© The Author(s) 2020.)

Purpose: To assess the impact on ankle stability after repairing the ATFL alone compared to repairing both the ATFL and CFL in a biomechanical cadaver model., Methods: Ten matched pairs of intact, fresh frozen human cadaver ankles (normal) were mounted to a test machine in 20.0° plantar flexion and 15.0° of internal rotation. Each ankle was loaded to body weight and then tested from 0.0° to 20.0° of inversion. The data recorded were torque at 20.0° and stiffness, peak pressure and contact area in the ankle joint using a Tekscan sensor, rotation of the talus and calcaneus, and translation of the calcaneus using a three-dimensional motion capture system. Ankles then underwent sectioning of the ATFL and CFL (injured), retested, then randomly assigned to ATFL-only Broström repair or combined ATFL and CFL repair. Testing was repeated after repair then loaded in inversion to failure (LTF)., Results: The stiffness of the ankle was not significantly increased compared to the injured condition by repairing the ATFL only (n.s.) or the ATFL/CFL (n.s.). The calcaneus had significantly more rotation than the injured condition in the ATFL-only repair (p = 0.037) but not in the ATFL/CFL repair (n.s.). The ATFL failed at 40.3% higher torque than the CFL, at 17.4 ± 7.0 N m and 12.4 ± 4.1 N m, respectively, and 62.0% more rotation, at 43.9 ± 5.6° and 27.1 ± 6.8°, respectively., Conclusions: There was a greater increase in stiffness following combined ATFL/CFL repair compared to ATFL-only repair, although this did not reach statistical significance. The CFL fails before the ATFL, potentially indicating its vulnerability immediately following repair., Level of Evidence: III, case-control therapeutic study.

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., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Background: The limitations of functional electrical stimulation (FES) cycling directly affect the health benefits acquired from this technology and prevents its' full potential to be realised. Experiments should be done on a test bed which can isolate and focus only on one muscle group, namely the quadriceps. The aim of this work was to design and develop an isokinetic robotic leg extension/flexion dynamometer which can mimic knee joint motion during actual cycling to be used for evaluation of novel functional electrical stimulation strategies. Although the main motivation for development of the dynamometer was for application in FES studies, it has the potential to be used for various different muscle physiology studies., Methods: A feedback control system with integrated electrical stimulation for isokinetic knee joint torque measurement has been developed and tested for safety and functionality. The leg extension/flexion device was modified and equipped with a DC motor drive system to imitate isokinetic knee joint motion during cycling when the hip joint remains fixed. Real-time bi-directional effective torque on the lever arm was measured by a magnetostrictive torque sensor and a load cell. Closed-loop motor control system was also designed to mimic the cyclical motion at desired angular velocity., Results: A functional model of the robotic dynamometer was developed and evaluated. The dynamometer is capable of simulating the knee angle during cycling at a cadence of up to 70 rpm with range of motion of 72 ∘ . The magnetostrictive torque sensor can measure torque values up to 75 Nm. The lever arm can be adjusted and the target knee angle was controlled with RMSE tracking error of less than 2.1 ∘ in tests with and without a test person, and with and without muscle stimulation., Conclusions: The isokinetic knee joint torque measurement system was designed and validated in this work, and subsequently used to develop and evaluate novel muscle activation strategies. This is important for fundamental research on effective stimulation patterns and novel activation strategies. This will, in turn, enhance the efficiency of FES cycling exercise and has the potential to improve the health-beneficial effects., (Copyright © 2019 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

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.

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., Competing Interests: Competing interestsThe authors declare that they have no competing interests., (© The Author(s) 2019.)

Chronic Achilles tendon ruptures typically are treated with surgical intervention except in low-demand patients or patients who are unable to tolerate surgery. Although several treatment strategies are described, most literature is case reports and case series. There is no widely accepted algorithm or gold standard for surgical treatment of chronic Achilles tendon ruptures. Treatment strategy depends on the size of the tendon gap after excision of nonviable tissue and scar tissue. Smaller gaps can be treated with direct end-to-end repair. Medium-sized gaps can be treated with tendon-lengthening procedures. Tendon transfers, autograft, allograft, xenograft, and synthetic grafting are described for the reconstruction of large defects., (Copyright © 2019 Elsevier Inc. All rights reserved.)

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., Competing Interests: The authors have declared that no competing interests exist.

Patient-reported outcomes (PROs) are a measure of health care quality that reflect the patient's perceptions of their own health status. Recently, there has been a renewed interest in implementation of PROs into everyday clinical practice. There are many dozens of PROs available to foot and ankle surgeons with little consensus on which measures are most appropriate for a given condition. These measures vary widely in length, validity, and content. When integrating PROs into clinical practice, we recommend that clinicians should collect, at a minimum, validated PRO scores that assess pain, function, and general health. Furthermore, concise instruments should be used wherever possible to minimize patient burden, maximize patient engagement, and ensure meaningful data are collected. In the near future, outcomes registries employing computer adaptive testing will facilitate the routine collection of PRO data from all patients., Level of Evidence: Level V, expert opinion., Competing Interests: Declaration of Conflicting Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. ICMJE forms for all authors are available online., (© The Author(s) 2019.)