Leap-frog patterns in systems of two coupled FitzHugh-Nagumo units

We study a system of two identical FitzHugh-Nagumo units with a mutual linear coupling in the fast variables. While an attractive coupling always leads to synchronous behavior, a repulsive coupling can give rise to dynamical regimes with alternating spiking order, called leap-frogging. We analyze various types of periodic and chaotic leap-frogging regimes, using numerical pathfollowing methods to investigate their emergence and stability, as well as to obtain the complex bifurcation scenario which organizes their appearance in parameter space. In particular, we show that the stability region of the simplest periodic leap-frog pattern has the shape of a locking cone pointing to the canard transition of the uncoupled system. We also discuss the role of the timescale separation in the coupled FitzHugh-Nagumo system and the relation of the leap-frog solutions to the theory of mixed-mode oscillations in multiple timescale systems

Comparison of pre- and post-operative shoulder muscle EMG profiles in reverse total shoulder arthroplasty patients

Background: Deltoid muscle function is central in reverse total shoulder arthroplasty (RTSA) function; however, there is limited information available regarding changes in deltoid activity before and after surgery. Few tests exist to evaluate specific muscle metrics pre and post operatively. Surface Electromyographic (EMG) is non-invasive and allows for observation of motions with multifaceted analysis of movement with minimal patient demand. Understanding the changes in shoulder muscle activation, namely in the deltoid, in patients pre and post-RTSA can further advance understanding of the procedure and rehabilitation efforts. Methods: Nine individuals were recruited for this study: all patients underwent RTSA by a single fellowship trained shoulder and elbow surgeon. Participants executed shoulder abduction, forward flexion, internal and external rotation at slow, medium and fast speeds as well as static maximum contraction of these motions against force at each EMG testing session. EMG activation of the anterior, middle and posterior aspects of the deltoid, upper and middle trapezius, supraspinatus, infraspinatus, teres major and teres minor was recorded on the surgical shoulder preoperatively, and 6 weeks, 3 months and 6 months postoperatively. Delsys EMG acquisition software linked to Bluetooth sensors captured shoulder motion. Statistical comparisons between pre-RTSA and post-RTSA shoulders, as well as consecutive post-RTSA shoulders were performed using one-way ANOVA (p\u3c0.05). Results: Analysis pending- will be fully available at the symposium. Preliminary data show an overall significant increase in concentric muscle activity (RMS) of the anterior and lateral deltoid during abduction when comparing: 6 week post-RTSA patients (6w-RTSA) to pre-RTSA and 6w-RTSA to 3 month post-RTSA (3m-RTSA). Furthermore, there was a significant increase in frequency (PSD) in anterior and lateral deltoid during abduction when comparing the same groups. There were no significant changes in RMS or PSD when comparing 3m to 6m-RTSA during abduction. During forward flexion in the sagittal plane, an overall significant increase in RMS and PSD of the anterior and lateral deltoid was observed in 3m-RTSA compared to pre-RTSA. Deltoid muscle activation time significantly decreased for abduction and forward flexion at medium and fast speeds when comparing 6w-RTSA to 3m-RTSA and 3m-RTSA to 6m-RTSA. There was an insignificant increase in posterior deltoid activation during external rotation when comparing 6w- to 3m-RTSA. Conclusion: Post-RTSA patients showed increased concentric muscle activity and muscle fiber frequency in the anterior and lateral deltoid muscle fibers when compared with pre-RTSA patients during abduction, forward flexion and external rotation. Some degree of increase in deltoid activation was seen when comparting specific post-RTSA groups. Overall, these findings suggest the deltoid muscle has an increased role in abduction, forward flexion and external rotation in RTSA patients

Patient-Reported Outcomes Measurements Information System (PROMIS) upper extremity and pain interference do not significantly predict rotator cuff tear dimensions

BACKGROUND: Proper diagnosis of rotator cuff tears is typically established with magnetic resonance imaging (MRI); however, studies show that MRI-derived measurements of tear severity may not align with patient-reported pain and shoulder function. The purpose of this study is to investigate the capacity for the Patient-reported Outcomes Measurements Information System (PROMIS) computer adaptive tests to predict rotator cuff tear severity by correlating preoperative tear morphology observed on MRI with PROMIS upper extremity (UE) and pain interference (PI) scores. This is the first study to investigate the relationship between tear characteristics and preoperative patient-reported symptoms using PROMIS. Considering the essential roles MRI and patient-reported outcomes play in the management of rotator cuff tears, the findings of this study have important implications for both treatment planning and outcome reporting. METHODS: Two PROMIS-computer adaptive test forms (PROMIS-UE and PROMIS-PI) were provided to all patients undergoing rotator cuff repair by one of three fellowship-trained surgeons at a single institution. Demographic information including age, sex, race, employment status, body mass index, smoking status, zip code, and preoperative PROMIS-UE and -PI scores was prospectively recorded. A retrospective chart review of small to large full- or partial-thickness rotator cuff tears between May 1, 2017 and February 27, 2019 was used to collect each patient\u27s MRI-derived tear dimensions and determine tendon involvement. RESULTS: Our cohort consisted of 180 patients (56.7% male, 43.3% female) with an average age of 58.9 years (standard deviation, 9.0). There was no significant difference in PROMIS-UE or -PI scores based on which rotator cuff tendons were involved in the tear (P \u3e .05). Neither PROMIS-UE nor PROMIS-PI significantly correlated with tear length or retraction length of the supraspinatus tendon (P \u3e .05). The sum of tear lengths in the anterior-posterior and medial-lateral directions was weakly correlated with PROMIS-UE (P = .042; r = -0.152, r = .031) and PROMIS-PI (P = .027; r = 0.165, r = 0.012). CONCLUSION: Rotator cuff tear severity does not significantly relate to preoperative PROMIS-UE and -PI scores. This finding underscores the importance of obtaining a balanced preoperative assessment of rotator cuff tears that acknowledges the inconsistent relationship between rotator cuff tear characteristics observed on MRI and patient-reported pain and physical function

Rockwood Grade-III Acromioclavicular Joint Separation: A Cost-Effectiveness Analysis of Treatment Options

Background: The treatment of Rockwood Grade-III acromioclavicular (AC) joint separation has been widely disputed since the introduction of the classification system. The present literature does not reach consensus on whether operative or nonoperative management is more advantageous, nor does it effectively distinguish between operative measures. We hypothesized that nonoperative treatment of Rockwood Grade-III AC joint separation would be more cost-effective when compared with surgical options. Methods: We created a decision-tree model outlining the treatment of Rockwood Grade-III separations using nonoperative management or hook-plate, suture-button, or allograft fixation. After nonoperative intervention, the possible outcomes predicted by the model were uneventful healing, delayed operative management, a second round of sling use and physical therapy, or no reduction and no action; and after operative intervention, the possible outcomes were uneventful healing, loss of reduction and revision, and depending on the implant, loss of reduction and no action, or removal of the implant. A systematic review was conducted, and probabilities of each model state were averaged. A cost-effectiveness analysis was conducted both through rollback analysis yielding net monetary benefit and through incremental cost-effectiveness ratios (ICERs). Thresholds of $50,000/quality-adjusted life-year (QALY) and$100,000/QALY were used for ICER analysis. Furthermore, a sensitivity analysis was utilized to determine whether differential probabilities could impact the model. Results: Forty-five papers were selected from a potential 768 papers identified through our literature review. Nonoperative treatment was used as our reference case and showed dominance over all 3 of the operative measures at both the $50,000 and$100,000 ICER thresholds. Nonoperative treatment also showed the greatest net monetary benefit. Nonoperative management yielded the lowest total cost ($6,060) and greatest utility (0.95 QALY). Sensitivity analysis showed that allograft fixation became the favored technique at a willingness-to-pay threshold of$50,000 if the rate of failure of nonoperative treatment rose to 14.6%. Similarly, at the $100,000 threshold, allograft became dominant if the probability of failure of nonoperative treatment rose to 22.8%. Conclusions: The cost-effectiveness of nonoperative treatment is fueled by its notably lower costs and overall high rates of success in Grade-III separations. It is important to note that, in our analysis, the societal cost (measured in lost productivity) of nonoperative treatment neared that of surgical treatment, but the cost from the health-care system perspective was minimal. Physicians should bear in mind the sensitivity of these conclusions and should consider cost-effectiveness analyses in their decision-making guidelines. Level of Evidence: Economic and Decision Analysis Level IV. See Instructions for Authors for a complete description of levels of evidence

PROMIS CAT Forms Demonstrate Responsiveness in Patients Following Reverse Total Arthroplasty Across Numerous Health Domains

Aim: The purpose of this study was to investigate the responsiveness of three PROMIS CAT domains in patients undergoing reverse shoulder arthroplasty. Background: To better optimize the administration and postoperative tracking of patients using PROM, the Patient-Reported Outcomes Measurement Information System (PROMIS) was established by the National Institutes of Health. PROMIS CAT domains have been since validated in multiple orthopedic interventions of the shoulder, however, no one to date has studied the responsiveness of PROMIS CAT domains in a cohort of patients undergoing reverse shoulder arthroplasty. Methods: Patients undergoing reverse shoulder arthroplasty by a board-certified shoulder and elbow surgeon were included in this study. PROMIS CAT Upper Extremity Physical Function (“PROMIS-UE”), Pain Interference (“PROMIS-PI”), and Depression (“PROMIS-D”) scores were collected preoperatively and at five postoperative timepoints. Patient-centric demographic factors, range of motion, and clinical characteristics were also reviewed and analyzed for association with PROMIS scores. Results: 104 patients undergoing primary reverse shoulder arthroplasty were included in this study. The patient cohort consisted of 52 males (50.0%), an average age of 70.3 years (standard deviation, 11.2), and a BMI of 30.2 (standard deviation, 6.1). All three PROMIS domains showed significant improvement as early as 6 weeks after surgery, with values of 32.4 ± 6.6, 56.2 ± 7.5, and 44.6 ± 8.6, for PROMIS-UE, PROMIS-PI, and PROMIS-D, respectively. Significant improvements were noted for each postoperative timepoint thereafter, with 1-year follow up values as follows: 42.1 ± 8.7, 52.5 ± 8.6, and 43.6 ± 9.5 for PROMIS-UE, PROMIS-PI, and PROMIS-D, respectively. Moderate correlations were identified with postoperative PROMIS-UE and abduction (r=0.439, p\u3c0.01), as well as postoperative PROMIS-PI and PROMIS-D (r=0.502, p\u3c0.01). Conclusions: PROMIS CAT forms demonstrate responsiveness in patients undergoing reverse shoulder arthroplasty

PROMIS MCID and SCB Achievement in Rotator Cuff Repair

The purpose of this study was to establish threshold score changes to determine minimal clinically important difference (MCID) and substantial clinical benefit (SCB) in PROMIS computer adaptive test (CAT) scores following rotator cuff repair (RCR). Patients undergoing arthroscopic RCR were identified over a 24-month period. PROMIS CAT forms for upper extremity physical function (PROMIS-UE), pain interference (PROMIS-PI), and depression (PROMIS-D) were utilized. Analysis of variance testing with post hoc least significant difference pairwise comparisons and Tukey’s B subset analysis were used in determining if anchor question responses showed statistically significant differences between answers. These findings were used to establish two clinically significant outcome (CSO) groups, MCID and substantial clinical benefit (SCB). Patients were then dichotomized into two separate analyses, no MCID achievement compared with MCID achievement and no SCB achievement compared with SCB achievement. Of the 198 eligible patients, 168 patients (84.8%) were included in analysis. Receiver operating curve analysis determined delta PROMIS-UE values of 5.8 and 9.7 (area under the curve (AUC) = 0.906 and 0.949, respectively) and delta PROMIS-PI values of -11.4 and -12.9 (AUC = 0.875 and 0.938, respectively) to be excellent threshold predictors of MCID and SCB achievement. On average, 81.1%, 65.0%, and 54.5% of patients achieved MCID for PROMIS-UE, PROMIS-PI, and PROMIS-D while 70.7%, 60.7%, and 37.7% of patients in the cohort respectively achieved SCB

Establishing Age-calibrated Normative PROMIS Scores for Hand and Upper Extremity Clinic

The purpose of our study is to investigate differences in normative PROMIS upper extremity function (PROMIS-UE), physical function (PROMIS-PF), and pain interference (PROMIS-PI) scores across age cohorts in individuals without upper extremity disability. Methods: Individuals without upper extremity disability were prospectively enrolled. Subjects were administered PROMIS-UE, PROMIS-PF, and PROMIS-PI forms. Retrospective PROMIS data for eligible subjects were also utilized. The enrolled cohort was divided into age groups: 20-39, 40-59, and 60-79 years old. ANOVA, ceiling and floor effect analysis, and kurtosis and skewness statistics were performed to assess PROMIS scores trends with age. Results: This study included 346 individuals. In the 20-39 age group, mean PROMIS scores were 56.2 ± 6.1, 59.8 ± 6.9, and 43.1 ± 6.7 for PROMIS-UE, PROMIS-PF, and PROMIS-PI, respectively. In the 40-59 age group, mean PROMIS computer adaptive test scores were 53.3 ± 7.5, 55.3 ± 7.6, and 46.6 ± 7.8 for PROMIS-UE, PROMIS-PF, and PROMIS-PI, respectively. In the 60-79 age group, mean PROMIS scores were 48.4 ± 7.6, 48.5 ± 5.6, and 48.7 ± 6.9 for PROMIS-UE, PROMIS-PF, and PROMIS-PI, respectively. Differences in mean PROMIS scores were significant across all PROMIS domains and age cohorts (P \u3c 0.001). Conclusion: Younger individuals without hand or upper extremity disability show higher normative PROMIS-UE and PROMIS-PF scores and lower PROMIS-PI scores, indicating greater function and less pain than older counterparts. A universal reference PROMIS score of 50 appears suboptimal for clinical assessment and decision-making in the hand and upper extremity clinic. This study included 346 individuals. In the 20-39 age group, mean PROMIS scores were 56.2 ± 6.1, 59.8 ± 6.9, and 43.1 ± 6.7 for PROMIS-UE, PROMIS-PF, and PROMIS-PI, respectively. In the 40-59 age group, mean PROMIS computer adaptive test scores were 53.3 ± 7.5, 55.3 ± 7.6, and 46.6 ± 7.8 for PROMIS-UE, PROMIS-PF, and PROMIS-PI, respectively. In the 60-79 age group, mean PROMIS scores were 48.4 ± 7.6, 48.5 ± 5.6, and 48.7 ± 6.9 for PROMIS-UE, PROMIS-PF, and PROMIS-PI, respectively. Differences in mean PROMIS scores were significant across all PROMIS domains and age cohorts (P \u3c 0.001)