Results of a feasibility and initial efficacy clinical trial of a high-intensity interval training program using adaptive equipment in persons with multiple sclerosis who have walking disability.

BACKGROUND: High intensity interval training (HIIT) has been identified as potential stimulus for eliciting health-promoting physical activity in an efficient manner among persons with multiple sclerosis (MS). The current study aimed to examine the feasibility and initial efficacy of a 12-week HIIT program using a recumbent stepper (RSTEP) in persons with MS who have walking disability. Feasibility outcomes of interest included process (i.e., recruitment, adherence, and retention rates), resource (i.e., time and monetary costs), management (i.e., data management and safety reporting assessment), and science (i.e., safety, burden, and treatment effect assessment). We hypothesized that 12-weeks of HIIT will be feasible via meeting a priori benchmarks in process, resource, management, and scientific outcomes. The efficacy outcomes of interest included changes in aerobic fitness, physical activity, walking, upper arm function, cognition, fatigue, and depressive symptoms. We hypothesized that 12 weeks of HIIT would result in improvements in aerobic capacity, walking, upper arm function, cognition, fatigue, and depression. METHODS: A pre-post clinical trial design was applied. Participants (N = 16) were recruited and enrolled in the 12-week RSTEP HIIT program who met the following inclusion criteria: age ≥18 years, self-reported diagnosis of MS, Patient Determined Disability Steps scale score 3.0-7.0, relapse free in past 30 days, willing to visit a University Laboratory for study protocol, asymptomatic status for maximal exercise testing, physician approval, and a self-reported ability to speak, read, and understand English. Measures of efficacy outcomes of interest included Six Minute Walk Test (6MW), Timed 25 Foot Walk Test (T25FW), the Brief International Cognitive Assessment in MS (BICAMS), 9-hole peg test (9-HPT), Expanded Disability Status Scale (EDSS), Fatigue Severity Survey (FSS), Hospital Anxiety and Depression Scale (HADS), Godin Leisure Time Exercise Questionnaire (GLTEQ), Multiple Sclerosis Walking Scale-12 (MSWS-12). Participants completed a graded maximal exercise test for measuring aerobic fitness (VO2peak) and prescription of exercise throughout the intervention. All outcomes were measured at baseline, mid-point (6-weeks), and post-intervention (12-weeks). The intervention involved 12 weeks of supervised, individualized HIIT sessions two times per week using RSTEP. The individual HIIT sessions included 10 cycles of 60 s intervals at the work rate associated with 90 % VO2peak followed by 60 s of active recovery intervals, totaling 20 minutes plus 5-minute warm-up and cool-down periods. Process, resources, management, and scientific feasibility outcomes were examined using descriptive statistics, percentage, and frequency analyses. The efficacy of the intervention was assessed using a 1-factor (Time), repeated measure analysis of variance to identify significant changes over time. RESULTS: Fourteen of 16 participants were retained throughout the full study period and adherence with prescribed exercise sessions was 97 %. Twenty-three staff were comprehensively trained across two sites. There was only one adverse event reported that did not impact participation in the study and overall mean satisfaction rating with the program among participants was 4.7/5. There were statistically significant changes in cognitive processing speed (p = 0.002), GLTEQ (p = 0.005), and MSWS-12 (p = 0.04), but not the other outcomes of fitness, arm function, and walking. Of note, there were large effect sizes noted for peak power output (d = 1.10) and FSS (d = 1.05) despite the lack of statistically significant changes CONCLUSION: Feasibility of a 12-week individualized RSTEP HIIT program was established and participants significantly improved on measures of cognition, physical activity, and walking.

Neural circuit basis of adolescent THC-induced potentiation of opioid responses in adult mice.

Use of one drug of abuse typically influences the behavioral response to other drugs, either administered at the same time or a subsequent time point. The nature of the drugs being used, as well as the timing and dosing, also influence how these drugs interact. Here, we tested the effects of adolescent THC exposure on the development of morphine-induced behavioral adaptations following repeated morphine exposure during adulthood. We found that adolescent THC administration impacted morphine-induced behaviors across several dimensions, including potentiating reward and paradoxically impairing the development of morphine reward. We then mapped the whole-brain response to a reinstatement dose of morphine, finding that adolescent THC administration led to increased activity in the basal ganglia and increased functional connectivity between frontal cortical regions and the ventral tegmental area. Last, we show using rabies virus-based circuit mapping that adolescent THC exposure triggers a long-lasting elevation in connectivity from the frontal cortex regions onto ventral tegmental dopamine cells that has the potential to influence dopaminergic response to morphine administration during adulthood. Our study adds to the rich literature on the interaction between drugs of abuse and provides potential circuit substates by which adolescent THC exposure influences responses to morphine later in life.

An Unusual Cause of Longstanding Diarrhea.

Colchicine is an alkaloid drug used in multiple medical conditions. It has a narrow therapeutic index, and gastrointestinal symptoms can occur at the beginning or after long-term therapy. Unintentional toxicity is common and has a high mortality rate when missed. Histopathologic recognition is challenging, and timely identification is conducted to improve patients' outcomes. We describe the case of a 77-year-old female who presented to the emergency room for dehydration, longstanding diarrhea, and weight loss. Upper and lower endoscopies showed erythematous mucosa without bleeding in the gastric antrum and an unremarkable duodenum and colon. Duodenal biopsies demonstrated partial villous atrophy with elongated glands and numerous arrested ring mitoses, consistent with colchicine toxicity.

Early emergency department discharge for intermediate heart score patients presenting for chest pain.

Study Objective: The use of the HEART score to risk stratify patients for short-term major adverse cardiac events in the emergency department (ED) setting is well established. Although discharge to home for low-risk HEART score patients is widely accepted as safe practice, there are limited outcomes data on moderate-risk HEART score patients discharged to home. We investigated the safety of discharging moderate-risk HEART score patients to home from the ED with established early cardiology follow-up. Methods: We performed a retrospective cohort analysis of patients presenting to the ED with chest pain from April 2020 through December 2020. Patients were evaluated in the ED and underwent serial conventional troponin testing and electrocardiogram (ECG). Clinicians calculated a HEART score and employed shared decision-making with moderate-risk patients (score 4-6), offering hospital admission versus discharge home with a formalized process for rapid cardiology follow-up (within 2 business days). We assessed the frequency of acute myocardial infarction or death at 30 days and before cardiology follow-up. Results: During our study period, 2939 patient encounters were screened for chest pain. Of these, 333 of 547 eligible moderate-risk HEART score patients were referred for rapid follow-up. The median time to follow-up appointment was 2.9 business days (interquartile range 1.3, 6.5), and 264 (79%) of patients kept their follow-up appointment. One patient (0.3%) suffered death within 30 days, before cardiology follow-up. There were no myocardial infarctions. Conclusions: These results suggest that moderate-risk HEART score patients may be considered for discharge from the ED with rapid cardiology follow-up. Formalizing processes to facilitate these early evaluations may represent a viable alternative to hospital admission, without diminishing patient outcomes.

An extended amygdala-midbrain circuit controlling cocaine withdrawal-induced anxiety and reinstatement.

Although midbrain dopamine (DA) circuits are central to motivated behaviors, our knowledge of how experience modifies these circuits to facilitate subsequent behavioral adaptations is limited. Here we demonstrate the selective role of a ventral tegmental area DA projection to the amygdala (VTADA→amygdala) for cocaine-induced anxiety but not cocaine reward or sensitization. Our rabies virus-mediated circuit mapping approach reveals a persistent elevation in spontaneous and task-related activity of inhibitory GABAergic cells from the bed nucleus of the stria terminalis (BNST) and downstream VTADA→amygdala cells that can be detected even after a single cocaine exposure. Activity in BNSTGABA→midbrain cells is related to cocaine-induced anxiety but not reward or sensitization, and silencing this projection prevents development of anxiety during protracted withdrawal after cocaine administration. Finally, we observe that VTADA→amygdala cells are strongly activated after a challenge exposure to cocaine and that activity in these cells is necessary and sufficient for reinstatement of cocaine place preference.

The Costs of Interfacility Transfers for Nonurgent Pediatric Supracondylar Fractures.

BACKGROUND: Unnecessary transfers of nonemergent pediatric musculoskeletal injuries to regional trauma centers can be costly. The severity of fracture displacement in supracondylar humerus fractures dictates the risk of complications, the urgency of transfer and the need for surgical treatment. The purpose of this study is to examine the transfer patterns of Gartland type II pediatric supracondylar humerus fractures to identify strategies for improving patient care, improving health care system efficiency, and reducing costs. We hypothesize that there will be a high rate of unnecessary, emergent transfers resulting in increased cost. METHODS: We retrospectively identified all pediatric patients that underwent treatment for a supracondylar humerus fracture between 2013 and 2018. Patient demographics, injury characteristics, chronological data, and surgical data were collected and analyzed from ambulance run sheets, transferring hospital records, and electronic medical records. Transfer distances were estimated using Google-Maps, while transfer costs were estimated using Internal Revenue Service (IRS) standard mileage rates and the American Ambulance Association Medicare Rate Calculator. A student t test was used to evaluate different treatment groups. RESULTS: Sixty-two patients had available and complete transfer data, of which 44 (71%) patients were safely transferred via private vehicle an average distance of 51.8 miles, and 18 (29%) patients were transferred via ambulance on an average distance of 55.6 miles ( P =0.76). The average transfer time was 4.1 hours by private vehicle, compared with 3.9 hours by ambulance ( P =0.56). The average estimated cost of transportation was $28.23 by private vehicle, compared with $647.83 by ambulance ( P =0.0001). On average, it took 16.1 hours after injury to undergo surgery and 25.7 hours to be discharged from the hospital, without a significant difference in either of these times between groups. There were no preoperative or postoperative neurovascular deficits. CONCLUSION: Patients with isolated Gartland type II supracondylar humerus fractures that are transferred emergently via ambulance are subjected to a significantly greater financial burden with no demonstrable improvement in the quality of their care, since prior research has shown these injuries can safely be treated on an outpatient basis. Potential options to help limit costs could include greater provider education, telemedicine and improved coordination of care. LEVEL OF EVIDENCE: Level III (retrospective comparative study).

Predictors of appointment adherence following operative treatment of pediatric supracondylar humerus fractures: which patients are not following up?

This study aims to identify characteristics associated with poor appointment adherence after surgical stabilization of supracondylar humerus fractures (SCHFX) in children. A retrospective review of 560 consecutive, surgically managed patients with SCHFX from 2010 to 2015 was performed. One missed follow-up appointment was classified as 'low adherence', whereas missing two or more appointments was classified as 'very low adherence'. Demographics, insurance status, estimated family income and distance from clinic were analyzed to identify differences in variables between adherent and low-adherent groups. Of 560, 121 (21.8%) missed one follow-up visit and 39/560 (7.1%) missed more than two visits. Age, gender, distance traveled, insurance status and primary language were nonpredictive. Estimated income <$50 000 was associated with a >200% increase in low adherence vs patients with estimated income >$50 000 (9.3 vs 3.8%; P = 0.012). African American patients had significantly lower adherence vs patients of other races (47.5 vs 19.6%; P < 0.0001). Ethnicity remained the only significant factor correlated to adherence after multivariate analysis. African Americans were three times more likely demonstrate low adherence (P = 0.0014). Ethnicity and estimated income <$50 000 were predictors of missing two or more visits. African American patients were four times more likely to miss two or more visits [odds ratio (OR), 4.17; P = 0.0026] than others; estimated income <$50 000 was associated with a two-fold increase in missing two or more visits (OR, 2.33; P = 0.035). By identifying at-risk patient populations, healthcare systems can adopt strategies to remove barriers of accessing follow-up care.

A student-centered seminar course as a complementary approach to a traditional journal club.

Graduate physiology programs strive to provide students with in-depth expertise in a particular academic discipline, often facilitating this process in the form of a departmental seminar course. Within the Department of Physiology and Biophysics at the University of California Irvine (UCI), students are required to attend a seminar course, most often designed as a journal club, each quarter until they are ready to graduate. While this format may work well in departments where research topics are closely related, it has historically been less successful in UCI's Department of Physiology and Biophysics, where wide-ranging interests make for little overlap in foundational knowledge, limiting meaningful engagement with the material or with peers in the class. In this paper, we describe a complementary approach of developing a syllabus around student interests and covering topics that are critical for student success but often omitted from graduate curricula, such as interview skills, grant writing, and scientific communication. Results from our preclass survey motivated this approach to the class, and our retrospective survey demonstrated the substantial differences in student engagement, enthusiasm, and perceived benefits of this course relative to the journal club style course. We hope that the success of our course may serve as an exemplar for strategies to engage students more effectively and provide critical training in diverse skillsets that will help students after graduation.

Cytologic analysis of vitreous fluids: A retrospective review of our 24 years of experience.

BACKGROUND: Cytologic analysis of vitreous fluid is an important component in diagnosis of vitreitis. No standard reporting guidelines exist for these specimens. This study chronicles our 24 years experience and proposes a tentative diagnostic model. METHODS: Retrospective cytology reports review and database study. Clinical indications, cytologic patterns, ancillary studies performed, and diagnoses were recorded. RESULTS: 176 samples from 160 patients were included and main cytologic patterns are reflected in Table 1. Most fluids were negative for malignancy (88%) and patterns IIB (53%) and IIA (19%) were dominant. The non-diagnostic rate was 7%; atypical and suspicious categories represented <0.5% of fluids tested and only 2% were positive for malignancy (3 intraocular lymphoma and one melanoma). Clinical indications for fluid examination were infection/inflammation (59%), to rule out lymphoma (11%), amyloidosis (3%), melanoma (2%), or to investigate intraocular hemorrhage. Fungal elements were demonstrated in 7 cases. No viral inclusions were appreciated; however, one case was positive for HSV 2 by IHC and 2 were negative by PCR. One case had Gram + cocci. Flow cytometry studies were suboptimal in 6 fluids, negative for an aberrant lymphocyte population in 11, and positive for high grade lymphoma in 3 cases. Atypical, suspicious and positive for melanoma were reported in 3 samples. Amyloid was identified in 1 aspirate. CONCLUSIONS: Cytologic analysis of vitreous fluid is a useful tool. Modern techniques like flow cytometry and PCR testing further expand the diagnostic possibilities. Standardization of diagnostic terminology will aid clinicians caring for patients suffering from ocular disease.

A connectomic analysis of deep brain stimulation for treatment-resistant depression.

OBJECTIVE: Deep brain stimulation (DBS) has been used as a treatment of last resort for treatment-resistant depression (TRD) for more than a decade. Many DBS targets have been proposed and tested clinically, but the underlying circuit mechanisms remain unclear. Uncovering white matter tracts (WMT) activated by DBS targets may provide crucial information about the circuit substrates mediating DBS efficacy in ameliorating TRD. METHODS: We performed probabilistic tractography using diffusion magnetic resonance imaging datas from 100 healthy volunteers in Human Connectome Project datasets to analyze the structural connectivity patterns of stimulation targeting currently-used DBS target for TRD. We generated mean and binary fiber distribution maps and calculated the numbers of WMT streamlines in the dataset. RESULTS: Probabilistic tracking results revealed that activation of distinct DBS targets demonstrated modulation of overlapping but considerably distinct pathways. DBS targets were categorized into 4 groups: Cortical, Striatal, Thalamic, and Medial Forebrain Bundle according to their main modulated WMT and brain areas. Our data also revealed that Brodmann area 10 and amygdala are hub structures that are associated with all DBS targets. CONCLUSIONS: Our results together suggest that the distinct mechanism of DBS targets implies individualized target selection and formulation in the future of DBS treatment for TRD. The modulation of Brodmann area 10 and amygdala may be critical for the efficacy of DBS-mediated treatment of TRD.

Do subcortical gray matter volumes and aerobic capacity account for cognitive-motor coupling in multiple sclerosis?

BACKGROUND: There is evidence of cognitive-motor coupling in multiple sclerosis (MS) such that the slowing of cognitive processing speed correlates with the worsening of walking speed and endurance. OBJECTIVE: The current study first established the presence of cognitive-motor coupling and second examined the possibility that volumes of subcortical gray matter (SGM) structures and aerobic capacity might explain the coupling of cognitive and motor functions in persons with MS. METHODS: We included data from 62 persons with clinically definite MS who underwent assessments of cognitive processing speed, walking performance, and aerobic capacity, and completed magnetic resonance imaging (MRI) within 7 days of the aforementioned assessments. RESULTS: The strong correlations between cognitive processing speed and walking performance were attenuated in magnitude and not statistically significant when controlling for aerobic capacity alone and aerobic capacity and SGM volumes together. The associations between cognitive processing speed and walking performance remained statistically significant when controlling for SGM volumes alone. CONCLUSION: Aerobic capacity may be an important target for neurorehabilitation-based approaches for managing co-occurring cognitive and motor dysfunction in MS.

Feasibility and initial efficacy of a high-intensity interval training program using adaptive equipment in persons with multiple sclerosis who have walking disability: study protocol for a single-group, feasibility trial.

BACKGROUND: There is considerable evidence for the efficacy of moderate-intensity continuous exercise benefitting clinically relevant outcomes in persons with multiple sclerosis (MS). However, persons with MS who have walking disability (pwMS-wd) are severely deconditioned and may achieve superior benefits by engaging in high-intensity interval training (HIIT), especially while utilizing adaptive equipment, such as recumbent arm/leg stepping (RSTEP). The proposed study will assess the feasibility of a 12-week, RSTEP HIIT program in pwMS-wd. The secondary aim will examine changes in aerobic fitness, physical activity, ambulation, upper arm function, cognition, fatigue, and depression as clinically relevant efficacy outcomes following the 12-week, RSTEP HIIT intervention. METHODS: The study will recruit 15 pwMS-wd. Feasibility will be measured via process, resource, management, and scientific outcomes throughout the entirety of the research study. The secondary, clinically relevant outcomes will consist of a neurological exam, aerobic capacity, physical activity, ambulation, cognition, upper arm function, fatigue, and depression. Outcomes will be assessed at baseline (T1), midpoint (T2, following 6 weeks), and post-intervention (T3, following 12 weeks). The intervention will involve 12 weeks of supervised, individualized HIIT sessions two to three times per week. The individual HIIT sessions will each involve 10 cycles of 60-s intervals at the wattage associated with 90% VO2peak followed by 60 s of active recovery intervals at 15 W, totaling 20 min in length plus 5-min warm-up and cool-down periods. DISCUSSION: The feasibility design of the proposed study will provide experience and preliminary data for advancing towards a proof-of-concept study comparing HIIT to moderate-intensity continuous RSTEP for improving clinically relevant outcomes in a randomized control trial design. The results will be disseminated via manuscripts for publication and a report for distribution among the National Multiple Sclerosis Society. TRIAL REGISTRATION: ClinicalTrials.gov NCT04416243 . Retrospectively registered on June 4, 2020.

Improving ROSE: Discrepant touch preparation and histology findings in cytology of renal masses: A 10-year retrospective review.

BACKGROUND: The number of "renal incidentalomas" is on the rise due to increasing use of radiologic studies. Image-guided core needle biopsies (CNB) with touch preparations are performed to guide specimen collection and triage of sample for additional studies. Results allow the clinical team to make appropriate treatment decisions. DESIGN: Our electronic database was searched for a 10-year period to identify 180 image-guided biopsies of renal masses with rapid on-site evaluations (ROSE) and corresponding biopsy/resection specimens. Touch preparations were classified as non-diagnostic, negative/benign, adequate/positive for malignancy/oncocytic predominance, or atypical. These results were compared to the final diagnosis on the biopsy or resection specimen (if available). Diagnostic accuracy, sensitivity, specificity, and positive and negative predictive values were determined. Non-diagnostic cases and cases in which ROSE and final diagnosis were discordant were reviewed by cytopathologists blinded to the original interpretation to reconcile discrepancies and highlight interpretation pitfalls. RESULTS: A ROSE diagnosis was rendered in 133 of 180 cases; 47 cases were non-diagnostic. Of the 133 diagnostic cases, the ROSE diagnosis was concordant with the core biopsy final diagnosis in 125 cases, yielding a diagnostic accuracy of 94%. The overall sensitivity was calculated to be 80.1%; specificity 72.4%; positive predictive value 94%; and negative predictive value 41.2%. CONCLUSIONS: Touch preparation slides are vital but imperfect tools in evaluating renal masses. In our study, distinction between malignant and benign samples was accomplished in most cases (94% accuracy), but there are limitations. Awareness of interpretation pitfalls allows informed decisions to be made regarding specimen collection and patient management.

Gradual Deformity Correction in Blount Disease.

BACKGROUND: Blount disease is a disorder of the posteromedial proximal tibial physis which causes a progressive varus, procurvatum, and internal rotation deformity of the tibia. Untreated, it can cause significant limb malalignment. The goal of this study is to evaluate the results of correction of Blount disease using types of external fixation. METHODS: We conducted a retrospective review of 41 patients (51 limbs) who underwent correction of Blount disease with an Ilizarov external fixator or a Taylor spatial frame (TSF) by a single surgeon. The medial proximal tibial angle (MPTA), mean axis deviation (MAD), posterior proximal tibial angle, and joint line congruence angle (JLCA) were measured on radiographs preoperatively, at frame removal and at final follow-up. RESULTS: The average age at treatment was 9.6 years old, with a mean follow-up time of 34 months. Mean preoperative MPTA, MAD, and JLCA were significantly improved at the time of frame removal as well as at final follow-up with no significant changes in correction between the time of frame removal and final follow-up. There was no difference in MPTA and MAD in patients treated with an Ilizarov frame versus a TSF. MPTA, MAD, and JLCA all significantly improved regardless of the underlying diagnosis (infantile vs. adolescent Blount disease) or history of prior surgical intervention. The most common complication was superficial pin-site infection. CONCLUSIONS: Both Iliazarov and TSF are viable treatment options for infantile and adolescent Blount disease, with the ability to significantly improve both the limb mechanical axis and the mechanical axis of the affected tibia. Correction can be attained regardless of whether patients have previously failed surgical intervention. LEVEL OF EVIDENCE: Level III-retrospective comparative study.

Understanding Skeletal Growth and Predicting Limb-Length Inequality in Pediatric Patients.

Limb-length inequality in a child can be a complex condition for patients, parents, and medical providers. Managing these patients and explaining the treatment options to families requires knowledge of the potential risks associated with leaving a discrepancy untreated and a thorough understanding of skeletal growth. The provider must also be familiar with the available growth prediction methods as treatment is influenced by the anticipated discrepancy at skeletal maturity. This article provides an overview to skeletal growth, assessing skeletal maturity and growth prediction to help providers develop an organized and thoughtful approach to treating pediatric patients with limb-length inequalities.

The interpretation of physical activity, exercise, and sedentary behaviours by persons with multiple sclerosis.

OBJECTIVES: This study adopted a qualitative research design with directed content analysis and examined the interpretations of physical activity, exercise, and sedentary behaviour by persons with multiple sclerosis. METHODS: Fifty three persons with multiple sclerosis who were enrolled in an exercise trial took part in semi-structured interviews regarding personal interpretations of physical activity, exercise, and sedentary behaviours. RESULTS: Forty three percent of participants indicated a consistent understanding of physical activity, 42% of participants indicated a consistent understanding of exercise, and 83% of participants indicated a consistent understanding of sedentary behaviour with the standard definitions. There was evidence of definitional ambiguity (i.e., 57, 58, and 11% of the sample for physical activity, exercise, and sedentary behaviour, respectively); 6% of the sample inconsistently defined sedentary behaviour with standard definitions. Some participants described physical activity in a manner that more closely aligned with exercise and confused sedentary behaviour with exercise or sleeping/napping. CONCLUSIONS: Results highlight the need to provide and utilise consistent definitions for accurate understanding, proper evaluation and communication of physical activity, exercise, and sedentary behaviours among persons with multiple sclerosis. PRACTICE IMPLICATIONS: The application of consistent definitions may minimise ambiguity, alleviate the equivocality of findings in the literature, and translate into improved communication about these behaviours in multiple sclerosis. Implications for Rehabilitation The symptoms of multiple sclerosis can be managed through participation in physical activity and exercise. Persons with multiple sclerosis are not engaging in sufficient levels of physical activity and exercise for health benefits. Rehabilitation professionals should use established definitions of physical activity, exercise, and sedentary behaviours when communicating about these behaviours among persons with multiple sclerosis.

Retrograde Stainless Steel Flexible Nails Have Superior Resistance to Bending in Distal Third Femoral Shaft Fractures.

BACKGROUND: It has been shown that retrograde titanium flexible intramedullary nails (Ti FIN) provide superior resistance to bending compared to antegrade Ti FIN in distal femur fractures. The purpose of this study was to compare resistance to torsional and bending forces of stainless steel (SS) FIN, with or without a locking screw, and Ti FIN in distal third femoral shaft fractures. We hypothesize that locked retrograde SS FIN will demonstrate greater resistance to both bending and torsional forces. METHODS: Thirty adolescent synthetic femur models were used to simulate transverse distal femoral fractures at either 60 mm or 90 mm proximal to the distal femoral physis. The femurs were instrumented with antegrade Ti FIN, antegrade SS FIN, retrograde Ti FIN, retrograde SS FIN, or retrograde locked SS FIN. Three models for each construct at both osteotomy levels were tested. Models were analyzed to determine maximum resistance to bending and torsion. RESULTS: In fractures 60 mm from the physis, retrograde SS FIN demonstrated statistically superior resistance to bending when compared with both antegrade and retrograde Ti FIN (P=0.001 and 0.008, respectively) and antegrade SS FIN (P=0.0001). Locked SS constructs showed a trend towards greater resistance to bending forces when compared with unlocked constructs (P>0.05). No significant difference was seen in resistance to bending when fractures were 90 mm proximal to the distal femoral physis between the five groups. No significant differences were observed in resistance to torsion in either the proximal or distal fracture models, regardless of construct type. CONCLUSIONS: Retrograde SS FIN confer significantly greater resistance to bending forces for fractures 60 mm proximal to the distal femoral physis compared with Ti FIN or antegrade entry SS FIN. In fractures 90 mm from the physis, no differences were noted in our model. Our results support the use of retrograde SS nails in the pediatric patient with distal femoral shaft fractures. LEVEL OF EVIDENCE: Level II-comparative biomechanical study.

Acute High-Intensity Interval Exercise in Multiple Sclerosis with Mobility Disability.

INTRODUCTION: Multiple sclerosis (MS) is an immune-mediated, neurological disease that results in physiological deconditioning with increasing disability. High-intensity interval training (HIIT) exercise has induced significant improvements in physiological conditioning in healthy and clinical populations and might be appropriate for persons with MS who have mobility disability. The feasibility and acute effects of HIIT using recumbent stepping in persons with MS who have mobility disability are relatively unknown. METHODS: The physiological effects of single sessions of HIIT and continuous (CON), steady-state aerobic exercise using recumbent stepping were compared in 20 persons with MS with mobility disability (i.e., Expanded Disability Status Scale of 4.0-6.5). The HIIT bout included 10 cycles of 1-min intervals at the work rate associated with 90% peak aerobic capacity (V˙O2peak) followed by 1-min recovery intervals at 15 W, totaling 20 min in length. The CON bout consisted of 20 min at the work rate associated with 50% to 60% V˙O2peak. Physiological (i.e., power output, oxygen consumption, carbon dioxide expiration, respiratory exchange ratio, ventilation, HR, and core temperature) and perceptual (i.e., ratings of perceived exertion) measures were collected across the acute sessions. RESULTS: There were statistically significant condition-time interactions for all physiological measures and ratings of perceived exertion expressing differential patterns of change over time for HIIT versus CON (P < 0.05). The main effect of condition was significant for all physiological outcomes, except core temperature, with the HIIT condition inducing significantly higher values than CON (P < 0.05). CONCLUSIONS: High-intensity interval training exercise taxes the cardiorespiratory system significantly more than CON, yet without deleterious effects on core temperature in persons with MS. This has important implications for informing an evidence-based exercise prescription that is appropriate for improving physiological conditioning in persons with MS who have mobility disabilities.