Impact of the COVID-19 pandemic on the rate of lower limb amputation in Veterans.

BACKGROUND: The COVID-19 pandemic led to changes in health care, including postponement of nonurgent appointments. These changes, combined with overall decreased activity levels, may have placed individuals with vascular disease at increased risk for skin ulceration and amputation. OBJECTIVE: To determine the rates of lower limb amputation in Veterans due to complications of diabetes and/or vascular disease in the year following onset of the COVID-19 pandemic (March 2020-March 2021) compared to the previous 3 years (March 2017-March 2020). DESIGN: Retrospective chart review. SETTING: Minneapolis Veterans Affairs Health Care System. PARTICIPANTS: Veterans with a vascular consult appointment note between March 1, 2017, and February 28, 2021. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Primary outcome was lower limb amputation rate in the year following onset of the COVID-19 pandemic compared to the previous 3 years. Secondary outcome was the rate of lower limb wounds in the same time frame. We hypothesized that rates of lower limb amputation and wounds increased during the pandemic. RESULTS: Vascular consult appointments (n = 4183) were reviewed between March 1, 2017, and February 28, 2021. Significantly higher rates of amputation (7.52% vs. 5.19%; p = .006) and wound presence (16.77% vs. 11.66%; p < .001) were found 1 year postpandemic compared to the previous 3 years. Amputation and wound rates did not significantly increase between pairs of consecutive years prior to the pandemic but significantly increased between the year preceding the pandemic and the first year of the pandemic (amputation p = .047; wound p = .004). CONCLUSIONS: Increased rates of amputation and wounds in Veterans following the onset of the COVID-19 pandemic are likely due to disruption of care, lifestyle changes, and other pandemic-related factors. Awareness of COVID-19-related negative health effects is imperative for health care providers to ensure appropriate allocation of resources and alternate models for care delivery for amputation and preventative care as part of disaster response.

Validation of Proprietary and Novel Step-counting Algorithms for Individuals Ambulating With a Lower Limb Prosthesis.

OBJECTIVE: To compare the accuracy and reliability of 10 different accelerometer-based step-counting algorithms for individuals with lower limb loss, accounting for different clinical characteristics and real-world activities. DESIGN: Cross-sectional study. SETTING: General community setting (ie, institutional research laboratory and community free-living). PARTICIPANTS: Forty-eight individuals with a lower limb amputation (N=48) wore an ActiGraph (AG) wGT3x-BT accelerometer proximal to the foot of their prosthetic limb during labeled indoor/outdoor activities and community free-living. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Intraclass correlation coefficient (ICC), absolute and root mean square error (RMSE), and Bland Altman plots were used to compare true (manual) step counts to estimated step counts from the proprietary AG Default algorithm and low frequency extension filter, as well as from 8 novel algorithms based on continuous wavelet transforms, fast Fourier transforms (FFTs), and peak detection. RESULTS: All algorithms had excellent agreement with manual step counts (ICC>0.9). The AG Default and FFT algorithms had the highest overall error (RMSE=17.81 and 19.91 steps, respectively), widest limits of agreement, and highest error during outdoor and ramp ambulation. The AG Default algorithm also had among the highest error during indoor ambulation and stairs, while a FFT algorithm had the highest error during stationary tasks. Peak detection algorithms, especially those using pre-set parameters with a trial-specific component, had among the lowest error across all activities (RMSE=4.07-8.99 steps). CONCLUSIONS: Because of its simplicity and accuracy across activities and clinical characteristics, we recommend the peak detection algorithm with set parameters to count steps using a prosthetic-worn AG among individuals with lower limb loss for clinical and research applications.

Using kinematics to re-define the pull test as a quantitative biomarker of the postural response in normal pressure hydrocephalus patients.

Quantitative biomarkers are needed for the diagnosis, monitoring and therapeutic assessment of postural instability in movement disorder patients. The goal of this study was to create a practical, objective measure of postural instability using kinematic measurements of the pull test. Twenty-one patients with normal pressure hydrocephalus and 20 age-matched control subjects were fitted with inertial measurement units and underwent 10-20 pull tests of varying intensities performed by a trained clinician. Kinematic data were extracted for each pull test and aggregated. Patients participated in 103 sessions for a total of 1555 trials while controls participated in 20 sessions for a total of 299 trials. Patients were separated into groups by MDS-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) pull test score. The center of mass velocity profile easily distinguished between patient groups such that score increases correlated with decreases in peak velocity and later peak velocity onset. All patients except those scored as "3" demonstrated an increase in step length and decrease in reaction time with increasing pull intensity. Groups were distinguished by differences in the relationship of step length to pull intensity (slope) and their overall step length or reaction time regardless of pull intensity (y-intercept). NPH patients scored as "normal" on the MDS-UPDRS scale were kinematically indistinguishable from age-matched control subjects during a standardized perturbation, but could be distinguished from controls by their response to a range of pull intensities. An instrumented, purposefully varied pull test produces kinematic metrics useful for distinguishing clinically meaningful differences within hydrocephalus patients as well as distinguishing these patients from healthy, control subjects.

User-centered design and development of a trunk control device for persons with spinal cord injury: A pilot study.

CONTEXT/OBJECTIVE: There are no wheelchair products designed to allow users to dynamically control trunk posture to both significantly improve functional reach and provide pressure relief during forward lean. This pilot study sought to (1) gather stakeholder desires regarding necessary features for a trunk control system and (2) subsequently develop and pilot test a first-generation trunk control prototype. DESIGN: Multi-staged mixed methods study design. SETTING: Minneapolis VA Health Care System, Minneapolis, MN. PARTICIPANTS: Eight people with spinal cord injuries were recruited to participate in a focus group. Five participants returned to discuss, rate, and select a design concepts for prototype development. Two participants returned to test the first-generation trunk control prototype. INTERVENTIONS: The focus group members selected a trunk control device design that uses backpack straps with a single cable as the most desired option. Our design team then manufactured the first-generation prototype at the Minneapolis VA. OUTCOME MEASURES: Bimanual workspace capabilities (n = 1) and pressure map relief changes (n = 2) during supported forward lean were measured. Both participants also provided feedback on the trunk control devices usability. RESULTS: Bimanual workspace (for Participant 1) was increased by 311% in the sagittal plane with use of the trunk control device as compared to without. Pressure relief during a forward lean was increased with an overall dispersion index reduction of 87.6% and 27.7% for Participant 1 and Participant 2 respectfully. CONCLUSION: This pilot study successfully elicited desired features for a trunk control device from stakeholders and successfully developed and tested a first-generation trunk control prototype.

Adapting a fatigue model for shoulder flexion fatigue: Enhancing recovery rate during intermittent rest intervals.

Although the rotator cuff muscles are susceptible to fatigue, shoulder fatigue studies reporting torque decline during intermittent tasks are relatively uncommon in the literature. A previous modification to the three-compartment controller (3CC) fatigue model incorporated a rest recovery multiplier (3CC-r model) to represent augmented blood flow to muscle during rest intervals (Looft et al., 2018). A rest recovery value of r = 15 was optimal for ankle, knee, and elbow joint regions, whereas r = 30 was better for hand/grip muscles. However, shoulder torque decline data was unavailable in the literature for comparison. Thus, the purpose of this study was to collect fatigue data for two different intermittent, isometric shoulder flexion fatiguing tasks and assess the 3CC-r model with r = 15 or 30 compared to the original 3CC model. Twenty healthy participants (9 M) completed two fatigue tasks: 50% maximum voluntary contraction (MVC) with 50% duty cycle (DC) and 70% MVC with 70% DC. MVCs were assessed at discrete time points (1, 3, 5, 10, and 15 min) until endurance time (MET). Mean observed percent torque decline (%TD) for the two tasks were compared to three model estimates: 3CC-r (using r = 15 and r = 30) and 3CC. Using these data, we confirmed that the addition of a rest multiplier (r = 15 somewhat better than r = 30) substantially improved predictions of shoulder fatigue using a previously validated analytical fatigue model (3CC). The relatively large reduction in model errors over the original model suggests the importance of representing augmented recovery during rest periods.

Finite element analysis of the rotator cuff: A systematic review.

BACKGROUND: Finite element modeling serves as a promising tool for investigating underlying rotator cuff biomechanics and pathology. However, there are currently no concrete guidelines for reporting in finite element model studies. This has compromised the reliability, validity, and reproducibility of literature due to omission of pertinent items within publications. Recently a Finite Element Model Grading Procedure has been proposed as a reporting guideline for model developers. The aim of this study was to conduct a systematic review of rotator cuff focused finite element models and characterize the reporting quality of those articles. METHODS: A comprehensive literature search was performed in PubMed, Web of Science, and Embase to find relevant articles. Each article was graded and given a reporting quality ranking based on a score generated from the Finite Element Model Grading Procedure. FINDINGS: We found that only 5/22 articles had scores of 75% or higher and fell within the "exceptional" reporting quality range. Most of the articles (16/22) fell within the "good" reporting quality range with scores between 50% and 75%. However, 9/16 articles within the "good" reporting quality range had scores below 60%. INTERPRETATION: This study indicates that improved guidelines and standards for good reporting practices must be made in the field of finite element modeling. Furthermore, it supports the use of the Finite Element Model Grading Procedure as an objective method for evaluating the quality of finite element model reporting in the literature.

Modification of a three-compartment muscle fatigue model to predict peak torque decline during intermittent tasks.

This study aimed to test whether adding a rest recovery parameter, r, to the analytical three-compartment controller (3CC) fatigue model (Xia and Frey Law, 2008) will improve fatigue estimates during intermittent contractions. The 3CC muscle fatigue model uses differential equations to predict the flow of muscle between three muscle states: Resting (MR), Active (MA), and Fatigued (MF). This model uses a feedback controller to match the active state to target loads and two joint-specific parameters: F, fatigue rate controlling flow from active to fatigued compartments) and R, the recovery rate controlling flow from the fatigued to the resting compartments. This model does well to predict intensity-endurance time curves for sustained isometric tasks. However, previous studies find when rest intervals are present that the model over predicts fatigue. Intermittent rest periods would allow for the occurrence of subsequent reactive vasodilation and post-contraction hyperemia. We hypothesize a modified 3CC-r fatigue model will improve predictions of force decay during intermittent contractions with the addition of a rest recovery parameter, r, to augment recovery during rest intervals, representing muscle re-perfusion. A meta-analysis compiling intermittent fatigue data from 63 publications reporting decline in peak torque (% torque decline) were used for comparison. The original model over-predicted fatigue development from 19 to 29% torque decline; the addition of a rest multiplier significantly improved fatigue estimates to 6-10% torque decline. We conclude the addition of a rest multiplier to the three-compartment controller fatigue model provides a physiologically consistent modification for tasks involving rest intervals, resulting in improved estimates of muscle fatigue.

Unicortical and bicortical plating in the fixation of comminuted fractures of the clavicle: a biomechanical study.

BACKGROUND: Intraoperative neurovascular complications with clavicle fracture fixation are often due to far cortex penetration by drills and screws, but could be avoided using a unicortical construct. The objective of this study was to compare the bending and torsional strength of a unicortical locking screw plate construct and a hybrid (with central locked and outer non-locked long oblique screws) unicortical plate construct for clavicle fracture fixation with that of a conventional bicortical locking screw construct of plate fixation. METHODS: Twenty-four human clavicle specimens were harvested and fractured in a comminuted mid-shaft butterfly configuration. Clavicles were randomly allocated to three surgical fixation groups: unicortical locking screw, bicortical locking screw and hybrid unicortical screw fixation. Clavicles were tested in torsion and cantilever bending. Construct bending and torsional stiffness were measured, as well as ultimate strength in bending. RESULTS: There were no significant differences in bending stiffness or ultimate bending moment between all three plating techniques. The unicortical locked construct had similar torsional stiffness compared with the bicortical locked construct; however, the hybrid technique was found to have significantly lower torsional stiffness to that of the bicortical locking screw construct (mean difference: 87.5 Nmm/degree, P = 0.028). CONCLUSIONS: Unicortical locked screw plate fixation and hybrid unicortical plating fixation with centrally locked screws and outer long, oblique screws may alleviate far cortex penetration, protecting nearby anatomical structures, and may ease implant removal and conversion to bicortical fixation for revision surgery; however, use of long oblique screws may increase the risk of early loosening under torsion.

A three-compartment muscle fatigue model accurately predicts joint-specific maximum endurance times for sustained isometric tasks.

The development of localized muscle fatigue has classically been described by the nonlinear intensity-endurance time (ET) curve (Rohmert, 1960; El Ahrache et al., 2006). These empirical intensity-ET relationships have been well-documented and vary between joint regions. We previously proposed a three-compartment biophysical fatigue model, consisting of compartments (i.e. states) for active (M(A)), fatigued (M(F)), and resting (M(R)) muscles, to predict the decay and recovery of muscle force (Xia and Frey Law, 2008). The purpose of this investigation was to determine optimal model parameter values, fatigue (F) and recovery (R), which define the "flow rate" between muscle states and to evaluate the model's accuracy for estimating expected intensity-ET curves. Using a grid-search approach with modified Monte Carlo simulations, over 1 million F and R permutations were used to predict the maximum ET for sustained isometric tasks at 9 intensities ranging from 10% to 90% of maximum in 10% increments (over 9 million simulations total). Optimal F and R values ranged from 0.00589 (F(ankle)) and 0.0182 (R(ankle)) to 0.00058 (F(shoulder)) and 0.00168 (R(shoulder)), reproducing the intensity-ET curves with low mean RMS errors: shoulder (2.7s), hand/grip (5.6s), knee (6.7s), trunk (9.3s), elbow (9.9s), and ankle (11.2s). Testing the model at different task intensities (15-95% maximum in 10% increments) produced slightly higher errors, but largely within the 95% prediction intervals expected for the intensity-ET curves. We conclude that this three-compartment fatigue model can be used to accurately represent joint-specific intensity-ET curves, which may be useful for ergonomic analyses and/or digital human modeling applications.