Effect of schooling on flow generated sounds from carangiform swimmers.

Computational models are used to examine the effect of schooling on flow generated noise from fish swimming using their caudal fins. We simulate the flow as well as the far-field hydrodynamic sound generated by the time-varying pressure loading on these carangiform swimmers. The effect of the number of swimmers in the school, the relative phase of fin flapping of the swimmers, and their spatial arrangement is examined. The simulations indicate that the phase of the fin flapping is a dominant factor in the total sound radiated into the far-field by a group of swimmers. For small schools, a suitable choice of relative phase between the swimmers can significantly reduce the overall intensity of the sound radiated to the far-field. The relative positioning of the swimmers is also shown to have an impact on the total radiated noise. For a larger school, even highly uncorrelated phases of fin movement between the swimmers in the school are very effective in significantly reducing the overall intensity of sound radiated into the far-field. The implications of these findings for fish ethology as well as the design and operation of bioinspired vehicles are discussed.

Changes in aorta hemodynamics in Left-Right Type 1 bicuspid aortic valve patients after replacement with bioprosthetic valves: An in-silico study.

Bicuspid aortic valve (BAV) is the most common cardiac congenital abnormality with a high rate of concomitant aortic valve and ascending aorta (AAo) pathologic changes throughout the patient's lifetime. The etiology of BAV-related aortopathy was historically believed to be genetic. However, recent studies theorize that adverse hemodynamics secondary to BAVs also contribute to aortopathy, but their precise role, specifically, that of wall shear stress (WSS) magnitude and directionality remains controversial. Moreover, the primary therapeutic option for BAV patients is aortic valve replacement (AVR), but the role of improved post-AVR hemodynamics on aortopathy progression is also not well-understood. To address these issues, this study employs a computational fluid dynamics model to simulate personalized AAo hemodynamics before and after TAVR for a small cohort of 6 Left-Right fused BAV patients. Regional distributions of five hemodynamic metrics, namely, time-averaged wall shear stress (TAWSS) and oscillating shear index (OSI), divergence of wall shear (DWSS), helicity flux integral & endothelial cell activation potential (ECAP), which are hypothesized to be associated with potential aortic injury are computed in the root, proximal and distal ascending aorta. BAVs are characterized by strong, eccentric jets, with peak velocities exceeding 4 m/s and axially circulating flow away from the jets. Such conditions result in focused WSS loading along jet attachment regions on the lumen boundary and weaker, oscillating WSS on other regions. The jet attachment regions also show alternating streaks of positive and negative DWSS, which may increase risk for local tissue stretching. Large WSS magnitudes, strong helical flows and circumferential WSS have been previously implicated in the progression of BAV aortopathy. Post-intervention hemodynamics exhibit weaker, less eccentric jets. Significant reductions are observed in flow helicity, TAWSS and DWSS in localized regions of the proximal AAo. On the other hand, OSI increases post-intervention and ECAP is observed to be low in both pre- and post-intervention scenarios, although significant increases are also observed in this ECAP. These results indicate a significant alleviation of pathological hemodynamics post AVR.

Does preoperative opioid use predict outcomes to 6 months following primary unilateral knee or hip arthroplasty for osteoarthritis? A data-linked retrospective study.

BACKGROUND: Few Australian studies have examined the incidence of prescribed opioid use prior to primary total knee or total hip arthroplasty (TKA, THA) and whether it predicts post-surgery outcomes. A recent Australian study demonstrated that the prevalence of pre-arthroplasty opioid use was approximately 16%. In the United States, approximately 24% of people undergoing TKA or THA are chronic opioid users preoperatively. PURPOSE: This study aimed to determine (i) the proportion of TKA and THA patients who use prescribed opioids regularly (daily) before surgery (i.e., opioid use reported between the time of waitlisting and any time up to 3 months before surgery), (ii) if opioid use before surgery predicts (a) complication/readmission rates to 6-months post-surgery, and (b) patient-reported outcomes to 6-months post-surgery. METHODS: A retrospective cohort study of patients who underwent TKA or THA between January 2013 and June 2018 from two Australian public hospitals was undertaken utilizing linked individual patient-level data from two prospectively collected independent databases comprising approximately 3,500 and 9,500 people (database contained known opioid usage data within the 5-year time frame). Inclusion criteria included (i) primary diagnosis of osteoarthritis of the index joint, (ii) primary elective THA or TKA, and (iii) age ≥ 18 years. Exclusion criteria included (i) revision arthroplasty, (ii) non-elective arthroplasty, (iii) hip hemiarthroplasty, (iv) uni-compartmental knee arthroplasty, and (v) previous unilateral high tibial osteotomy. RESULTS: Analysis was completed on 1,187 study participants (64% female, 69% TKA, mean (SD) age 67 [9.9]). 30% were using regular opioids preoperatively. Adjusted regression analyses controlling for multiple co-variates indicated no significant association between preoperative opioid use and complications/readmission rates or patient-reported outcomes to 6 months post-surgery. Model diagnostics produced poor discrimination for area under the curves and non-significant goodness of fit tests. Pre-arthroplasty opioid use was associated with lower health-related quality of life (EuroQol-Visual Analogue Scale) compared to non-opioid users undergoing primary THA (mean difference -5.04 [-9.87, -0.22], P = 0.04, Adjusted R2 = 0.06) CONCLUSION: In this study, 30% of patients were using prescribed opioids daily prior to primary TKA or THA. Pre-arthroplasty opioid use was not associated with postoperative adverse events or patient-reported pain, function, or global perceived improvement up to six months post-surgery.

In silico modelling of the effect of pyloric intervention procedures on gastric flow and emptying in a stomach with gastroparesis.

Pyloric interventions are surgical procedures employed to increase the gastric emptying rate in gastroparesis patients. In this study, we use an in silico model to investigate the consequences of pyloric intervention on gastric flow and emptying for two phenotypes of gastroparesis: antral hypomotility and decreased gastric tone. The transpyloric pressure gradient predicted by the in silico model, based on viscous fluid flow equations, is compared against in vivo measurements. Both phenotypes exhibit a similar pre-procedural emptying rate reduction, but after pyloric surgery, antral hypomotility case with preserved gastric tone shows significant improvements in emptying rates, up to 131%, accompanied by bile reflux from the duodenum into the stomach. Conversely, severely reduced gastric tone cases exhibited a post-procedural reduction in the net emptying rate due to the relatively larger bile reflux. In cases with a combination of antral hypomotility and reduced gastric tone, post-procedural improvements were observed only when both conditions were mild. Our findings highlight the pivotal role of the relative increase in pyloric orifice diameter in determining post-operative emptying rates. The study suggests a possible explanation for the selective response of patients toward these procedures and underscores the potential of in silico modelling to generate valuable insights to inform gastric surgery.

A pilot study of intraoperative application of cooled radiofrequency to reduce post-operative pain following total knee arthroplasty.

BACKGROUND: Total Knee Arthroplasty (TKA) is a successful treatment for end stage knee osteoarthritis (OA), but can be associated with significant pain in the early post-operative period. Cooled radiofrequency ablation (CRFA) has reported to reduce knee OA pain by targeting the periarticular nerves. The objective of this pilot study was to assess the effectiveness of intra-operative CRFA for reducing pain and opiate use after TKA. METHODS: This was a non randomised prospective study with control group. Participants were sequentially recruited preoperatively and underwent TKA, with CRFA to 6 targeted sites prior to cementing of implants, and were compared to controls who underwent TKA without CRFA. The primary outcome was Day 3 pain scores, and secondary outcomes included week one pain scores, and opiate use up to six weeks post-operative. RESULTS: 17 participants were recruited to the control group and 12 were recruited to the CRFA group. There was no significant difference in demographics or baseline pain scores between the groups. On day 2 the CRFA group had a lower mean pain VAS score of 3.2 compared to 4.4 in the control group (p = 0.03). The mean post operative VAS pain score did not differ between the groups for Day 1, 3, 4, or any other time points up to 6 weeks. There were no significant reduction in opiate use in the CRFA group compared to the control group. There were no adverse events. CONCLUSION: This study demonstrated intra-operative CRFA was not effective in reducing pain by 50% after TKA in a pilot study.

Origin and evolution of immersed boundary methods in computational fluid dynamics.

This article presents the evolutionary history of Immersed Boundary Methods (IBMs), tracing their origins to the very beginning of computational fluid dynamics in the late 1950s all the way to the present day. The article highlights the advancements in this simulation methodology over the last fifty years and explores the interplay between IBMs and body-conformal grid (BCG) methods during this time. Drawing upon the author's combined experience of over forty years in this arena, the perspective offered is personal and subjective. By employing a critical and comparative approach through the chronological lens, we hope that this article empowers the reader to understand both the capabilities and limitations of these methods, and to pursue advancements that fill the key gaps and break new ground.

Pancreatic duct pressure: A review of technical aspects and clinical significance.

Pancreatic duct pressure (PDP) dynamics comprise an intricately modulated system that helps maintain homeostasis of pancreatic function. It is affected by various factors, including the rate of pancreatic fluid secretion, patency of the ductal system, sphincter of Oddi function, and pancreatic fluid characteristics. Disease states such as acute and chronic pancreatitis can alter the normal PDP dynamics. Ductal hypertension or increased PDP is suspected to be involved in the pathogenesis of pancreatic pain, endocrine and exocrine pancreatic insufficiency, and recurrent pancreatitis. This review provides a comprehensive appraisal of the available literature on PDP, including the methods used in the measurement and clinical implications of elevated PDP.

Efficient trapping and destruction of SARS-CoV-2 using PECO-assisted Molekule air purifiers in the laboratory and real-world settings.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is transmitted human-to-human via aerosols and air-borne droplets. Therefore, capturing and destroying viruses from indoor premises are essential to reduce the probability of human exposure and virus transmission. While the heating, ventilation, and air conditioning (HVAC) systems help in reducing the indoor viral load, a targeted approach is required to effectively remove SARS-CoV-2 from indoor air to address human exposure concerns. The present study demonstrates efficient trapping and destruction of SARS-CoV-2 via nano-enabled filter technology using the UV-A-stimulated photoelectrochemical oxidation (PECO) process. Aerosols containing SARS-CoV-2 were generated by nebulization inside an air-controlled test chamber where an air purifier (Air Mini+) was placed. The study demonstrated the efficient removal of SARS-CoV-2 (99.98 %) from the test chamber in less than two minutes and PECO-assisted destruction (over 99%) on the filtration media in 1 h. Furthermore, in a real-world scenario, the Molekule Air-Pro air purifier removed SARS-CoV-2 (a negative RT-qPCR result post-running the filter device) from the circulating air in a COVID-19 testing facility. Overall, the ability of two FDA-approved class II medical devices, Molekule Air-Mini+ and Air-Pro air purifiers, to remove and destroy SARS-CoV-2 in indoor settings was successfully demonstrated. The study indicates that as the "tripledemic" of COVID-19, influenza, and respiratory syncytial virus (RSV) overwhelm the healthcare facilities in the USA, the use of a portable air filtration device will help contain the spread of the viruses in close door facilities, such as in schools and daycare facilities.

Rate of Infection and Causative Organisms in a Lateral Approach Total Ankle Replacement.

BACKGROUND: Although the rate of both superficial and deep infection in total ankle replacement (TAR) can reach up to 13% as reported in the literature, there is little information on the causative organisms, especially in laterally implanted prosthesis. This study aims to identify organisms causing infections to ultimately guide to better antibiotic prophylaxis. METHODS: Between September 2016 and April 2021, we retrospectively reviewed patients who had an infection after a lateral TAR. Cause of the infection, causative organisms, and implant survival were recorded. RESULTS: Out of 130 patients, 10 of 130 patients (7.6%) had a superficial infection whereas 3 of 130 patients (2.3%) had a deep infection. Staphylococcus and Pseudomonas species were found to be the most common. No significant difference was found between the type of plate used for fibula fixation regarding wound dehiscence. CONCLUSIONS: Infection after lateral TAR is generally polymicrobial in nature with Staphylococcus and Pseudomonas species being the most common. LEVEL OF EVIDENCE: Level IV Case Series.

Trends in management of adult tarsometatarsal joint injuries in a contemporary Australian context: a nationwide study of claims data over 20 years.

BACKGROUND: Traumatic tarsometatarsal joint (TMTJ) injuries are uncommon, but can cause significant morbidity due to delayed or missed diagnosis. Recent evidence highlights the importance of achieving anatomical reduction via operative management. This study aims to analyse trends in rates of open reduction internal fixation (ORIF) for Lisfranc injuries in Australia according to Nationwide claims data. METHODS: Claims according to the Medicare Benefits Schedule (MBS) on ORIF of traumatic TMTJ injuries were collated for the period from January 2000 to December 2020. Paediatric patients were excluded. Two negative binomial models were utilized to analyse the trends in TMTJ injuries over time after controlling for sex, age group and population changes. Results were absolute and per 100 000 population. RESULTS: 7840 patients underwent TMTJ ORIF over the period studied. There was a mean yearly increase of 12% (P < 0.001). Age group (P < 0.001) and year (P < 0.001) were significant predictors for TMTJ fixation, whilst sex was not (P = 0.48). Patients older than 65 years were noted to have a 53% lower rate of TMTJ ORIF per person, when compared to the reference group of 25-34 year-olds (P < 0.001). Five-year block analysis revealed increases in rate of fixation for all age groups. CONCLUSION: Rates of operative fixation for TMTJ injuries are increasing in Australia. This is likely due to improved diagnostics, understanding of optimal treatment goals, and increased orthopaedic subspecialisation. Further studies with clinical and patient reported outcomes, as well as comparing rates of operative intervention to incidence, will be useful.

Does Radiographic Alignment Correlate With Patient-Reported Functional Outcomes and Posttreatment Complications in Older Patients Treated for Wrist Fractures?

PURPOSE: Surgical treatment of distal radius fractures provides better fracture alignment than closed reduction; however, surgical treatment does not lead to better patient-reported function at 12 months. The aims of this study were to report the radiographic outcomes from the Combined Randomized and Observational Study of Surgery for Fractures In the distal Radius in the Elderly trial, investigate the association between radiographic outcomes and patient-reported function, and explore whether this association was affected by posttreatment complications and direction of malalignment. METHODS: This study used the outcomes of the Combined Randomized and Observational Study of Surgery for Fractures In the distal Radius in the Elderly trial, which is a combined randomized and observational trial that compared volar-locking plate fixation with closed reduction and cast immobilization, to treat distal radius fractures in patients aged ≥60 years. Four radiographic outcomes (dorsal angulation, radial inclination, ulnar variance, and articular step) were reported at the following three time frames: (1) baseline, (2) after treatment, and (3) ≥6 weeks by treatment group. Secondary analysis was correlation of 12-month patient-reported function scores with 6-week radiographic measures for each of four radiographic parameters, and a subgroup analysis was conducted to investigate if this was affected by posttreatment complications. Tertiary analysis investigated if direction of malalignment affected the secondary analysis. RESULTS: We recruited 300 participants (166 randomized and 134 observational); 113 had volar-locking plate fixation, and 187 had closed reduction. There were no between-group differences for each of the four pretreatment radiographic parameters, but there were between-treatment group differences for all four radiographic parameters apart from articular step. We found no association between patient-reported function at 12 months and each of the four radiographic parameters at 6 weeks. This lack of association was unaffected by posttreatment complications and the direction of malalignment. CONCLUSIONS: For patients with wrist fractures aged ≥60 years, final radiographic alignment did not correlate with patient-reported function at 12 months. These findings were not affected by treatment type, and there was no association between radiographic alignment and posttreatment complications. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.

Preliminary insights into patient preparedness for knee or hip arthroplasty: a descriptive survey study.

OBJECTIVE: Knowledge-based preparedness for surgery is achieved through education. It is unclear which of brief or extended education programs prior to knee or hip arthroplasty provides better patient preparedness. Using the Patient Preparedness for Surgery survey, we investigated whether people awaiting arthroplasty attending a hospital that provided education over multiple visits via a pre-surgery management program ('Extended') report superior preparedness compared to those attending a hospital in the same health district that only provides education at the pre-admission clinic assessment ('Brief'). RESULTS: A consecutive sample of 128 people (n = 101, 'Extended', n = 27 'Brief') completed the anonymized survey. COVID-19 related service disruptions undermined the sample size, reducing statistical power. The pre-specified superiority of the Extended program (a relative 20% more reporting 'agree'/'strongly agree') was not observed for 'Overall preparedness' [95% (Extended) vs. 89% (Brief), p = 0.36]. Between-group differences exceeding 20% relative superiority were observed for three preparedness sub-domains ['Alternatives explained' (52 vs. 33%, p = 0.09); 'Prepared for home' (85 vs. 57%, p < 0.01); 'Recall of complications' (42 vs 26%, p = 0.14)]. The preliminary findings suggest an extended education program potentially yields better patient-reported preparedness in some preparedness sub-domains, but not all.

Reconstructing the pressure field around swimming fish using a physics-informed neural network.

Fish detect predators, flow conditions, environments and each other through pressure signals. Lateral line ablation is often performed to understand the role of pressure sensing. In the present study, we propose a non-invasive method for reconstructing the instantaneous pressure field sensed by a fish's lateral line system from two-dimensional particle image velocimetry (PIV) measurements. The method uses a physics-informed neural network (PINN) to predict an optimized solution for the pressure field near and on the fish's body that satisfies both the Navier-Stokes equations and the constraints put forward by the PIV measurements. The method was validated using a direct numerical simulation of a swimming mackerel, Scomber scombrus, and was applied to experimental data of a turning zebrafish, Danio rerio. The results demonstrate that this method is relatively insensitive to the spatio-temporal resolution of the PIV measurements and accurately reconstructs the pressure on the fish's body.

A Shoulder/Elbow Triage and Assessment model of care reduced a public orthopaedic shoulder/elbow clinic waitlist with high patient satisfaction.

BACKGROUND: Patients referred to public orthopaedic clinics can experience long waiting times before assessment. This study aims to evaluate the effectiveness of a collaborative Shoulder/Elbow Triage and Assessment (SHELTA) model of care involving orthopaedic surgeons and physiotherapists to reduce the waitlist and improve service and clinical outcomes for patients on an orthopaedic shoulder/elbow clinic waitlist. METHODS: Patients on the waitlist were triaged by surgeons and physiotherapists and invited to an assessment by experienced physiotherapists. Patients were treated nonoperatively or transferred to orthopaedic management based on clinical discussion. The primary outcome was the number of patients on the waitlist. Secondary outcomes included adverse events, patient satisfaction, re-referral and conversion to surgery rates. Pain, function and patient global impression of change were recorded for participants managed nonoperatively. RESULTS: From July 2019 to December 2019, the waitlist reduced from 451 to 298 patients with no adverse events. Seventy-nine patients could not be contacted and 25 no longer required assessment, and were removed from the waitlist. Nonoperatively managed participants reported satisfaction with the service, a median score of 6 on a 7-point Patient Global Impression of Change scale, change in pain of -2.5/10 (95% CI -3.3, -1.7; P < 0.001) on a numerical pain rating scale, and change in function of -17.4/100 (95% CI: -24.1, -10.8; P < 0.001) on the QuickDASH, indicating improvement. CONCLUSIONS: The SHELTA model of care effectively reduced the number of patients on an orthopaedic shoulder/elbow clinic waitlist with good service and clinical outcomes.

Towards Longitudinal Monitoring of Leaflet Mobility in Prosthetic Aortic Valves via In-Situ Pressure Sensors: In-Silico Modeling and Analysis.

BACKGROUND: Transcatheter aortic valves (TAVs) are susceptible to leaflet thrombosis which may lead to thromboembolic events, and early detection and intervention are believed to be the key to avoiding such adverse outcomes. An embedded sensor system installed on the valve stent, coupled with an appropriate machine learning-based continuous monitoring algorithm can facilitate early detection to predict severity of reduced leaflet motion (RLM) and avoid adverse outcomes. METHODS: We present a data-driven, in silico, proof-of-concept analysis of a pressure microsensor based system for quantifying RLM in TAVs. We generate a dataset of 21 high-fidelity transvalvular flow simulations with healthy and mildly stenotic TAVs to train a logistic regression model to correlate individual leaflet mobility in each simulation with principal components of corresponding hemodynamic pressure recorded at strategic locations of the TAV stent. A separate test dataset of 7 simulations is also generated for prospective assessment of model performance. RESULTS: An array of 6 sensors embedded on the TAV stent, with two sensors tracking individual leaflet, successfully correlates leaflet mobility with recorded pressure. The sensors are placed along leaflet centerlines, one in the sinus, and the other at the sino-tubular junction. The regression model is tuned using cross-validation to achieve high accuracy on both training (R2 = 0.93) and test (R2 = 0.77) sets. CONCLUSION: Discrete blood pressure recordings on TAV stents can be successfully correlated with individual leaflet mobility. Further development of this technology can enable longitudinal monitoring of TAVs and early detection of valve failure.

Quantifying the Effect of Body Habitus on Cardiac Auscultation Via Computational Hemoacoustics.

The effect of body habitus on auscultation of heart murmurs is investigated via computational hemoacoustic modeling. The source of the heart murmur is first obtained from a hemodynamic simulation of blood flow through a stenosed aortic valve. This sound source is then placed at the aortic valve location in four distinct human thorax models, and the propagation of the murmur in each thorax model is simulated by solving the elastic wave equations in the time-domain. Placing the same sound source in different thorax models allows for the disambiguation of the effect of body habitus on cardiac auscultation. The surface acceleration resulting from the murmur on each subject's chest surface shows that subjects with higher body-mass index and thoracic cross-sectional area yield smaller acceleration values for the S1 sound. Moreover, the spectral analysis of the signal shows that slope from linear regression in the normal heart sound frequency range (10-150 Hz) is larger for children at the aortic, pulmonic, and mitral auscultation points compared to that for adults. The slope in the murmur frequency range (150-400 Hz) was larger for female subjects at the mitral point compared to that for male subjects. The trends from the results show the potential of the proposed computational method to provide quantitative insights regarding the effect of various anatomical factors on cardiac auscultation.

Early Clinical Outcomes and Complications of Transfibular Total Ankle Arthroplasty: The Australian Experience.

BACKGROUND: We report the short-term outcomes of a retrospective cohort of Trabecular Metal total ankle arthroplasties (TAAs) via a transfibular approach from a single, nondesigner surgeon in Australia. METHODS: This was a retrospective cohort study. Demographic, clinical, and patient-reported outcome measures (PROMs) were collected. The primary outcome was the Foot and Ankle Outcome Score (FAOS), and secondary outcomes included patient satisfaction, the EuroQol-5 Dimension (EQ5D), and complications including revision rates. RESULTS: Between 2016 and 2019, 84 trabecular metal prostheses were implanted in 84 patients. Mean age (SD) at time of surgery was 68 (7.8) years, and 46 (55%) were male. Mean follow-up (SD) was 26.1 (13) months. There were significant (P < .001) improvements in the FAOS in the subscales of pain (47.9 to 79.1), activities of daily living (59.5 to 83.7), and quality of life (25.5 to 60.2) and EQ-5D (0.55 to 0.75) (P < .001), and overall satisfaction was 69.6%. The commonest complications were wound infection or breakdown (11.9%, n=10), fibular nonunion (3.5%), plate irritation (3.5%), and tibial nerve neuropathy (3.5%). There were no thromboembolic complications. Implant survivorship was 100%, with Trabecular Metal components retained in all patients. Two patients developed deep infection, with 1 requiring debridement and polyethylene exchange. No patients experienced implant loosening. CONCLUSION: Our results demonstrate that the trabecular metal survival rates are comparable with other total ankle implants in the Australian Orthopaedic Association National Joint Replacement Registry and as published in other international literature. Overall patient satisfaction was high, as were PROMs. However, the data highlight potential complications uniquely associated with this implant. The authors believe that these figures support TAA via a transfibular approach as a viable option in the treatment of ankle arthritis. LEVEL OF EVIDENCE: Level IV, retrospective cohort study.

Effect of stomach motility on food hydrolysis and gastric emptying: Insight from computational models.

The peristaltic motion of stomach walls combines with the secretion of digestive enzymes to initiate the process that breaks down food. In this study, the mixing, breakdown, and emptying of a liquid meal containing protein is simulated in a model of a human stomach. In this model, pepsin, the gastric enzyme responsible for protein hydrolysis, is secreted from the proximal region of the stomach walls and allowed to react with the contents of the stomach. The velocities of the retropulsive jet induced by the peristaltic motion, the emptying rate, and the extent of hydrolysis are quantified for a control case as well as for three other cases with reduced motility of the stomach, which may result from conditions such as diabetes mellitus. This study quantifies the effect of stomach motility on the rate of food breakdown and its emptying into the duodenum and we correlate these observations with the mixing in the stomach induced by the wall motion.

Minimum 5-Year Follow-up Results: CROSSBAT (Combined Randomised and Observational Study of Surgery vs No Surgery for Type B Ankle Fracture Treatment).

BACKGROUND: Isolated Weber B, AO (Association for the Study of Internal Fixation) type 44B ankle fractures with no fracture to the medial side are the most common type of ankle fracture and may be treated with internal fixation or without surgery.This study aimed to determine if surgery is superior to nonsurgical management for the treatment of these fractures after a minimum 5-year follow-up. METHODS: Design: A pragmatic, multicenter, single-masked, randomized controlled trial with minimum 5-year follow-up. Setting/participants/interventions: Participants between 18 and 65 years with AO type 44B ankle fracture and minimal talar shift were recruited from 22 hospitals in Australia and New Zealand. Participants willing to be randomized were randomly allocated to undergo surgical fixation followed by mobilization in a walking boot for 6 weeks. Those treated nonsurgically were managed in a walking boot for 6 weeks. Outcome assessors were masked for the treatment allocation. Primary outcomes: Patient-reported ankle function using the American Academy of Orthopaedic Surgeons Foot and Ankle Outcomes Questionnaire (FAOQ) and the physical component summary (PCS) of the SF-12v2 General Health Survey at 12 months postinjury and at minimum 5 years post injury. Primary analysis was intention-to-treat. RESULTS: Of the 160 (80 surgical, 80 nonoperative) randomized patients included in the CROSSBAT analysis, 77 (40 surgical, 37 nonoperative) were followed up for repeat analysis at minimum 5-year follow-up (mean 7.3 years, range 5.1-8.9). This cohort demonstrated that surgery was not associated with clinically or statistically significant differences compared to nonoperative management for the FAOQ (51.7 vs 49.6; mean difference 2.1, 95% CI -2.1 to 6.2, P = .95), or the PCS (51.5 vs 49.1; mean difference 2.3, 95% CI -2.0 to 6.7, P = .54). The surgical cohort had a higher rate of any adverse events (odds ratio 3.7, 95% CI 1.2-11.6, P = .04). CONCLUSION: The results of this study suggest that surgical management is not superior to nonsurgical management in type B ankle (fibula) fractures with minimal talar shift over a 5-year period and is associated with increased adverse events. LEVEL OF EVIDENCE: Level II, randomized clinical trial.

Improved swimming performance in schooling fish via leading-edge vortex enhancement.

The hydrodynamics of schooling fish has been the subject of continued investigation over the last 50 years; fish schools exhibit a variety of arrangements and several distinct mechanisms have been proposed to explain the hydrodynamic benefits of schooling. In the current study, we use direct numerical simulations to show that a caudal fin swimmer trailing another similar swimmer can significantly improve its swimming performance by positioning itself such that the wake-induced flow of the leading fish, enhances the leading-edge vortex (LEV) on the fin of the trailing fish. Improvements of up to 12% in both the thrust and efficiency of the trailing fish are possible with this mechanism. The mechanisms underlying these interactional effects are quantitatively analyzed by applying the force partitioning method, a powerful data-driven method that partitions the pressure forces on the fish into mechanistically distinct components. The analysis reveals that the LEV on the fin dominates the overall thrust production for these swimmers and its enhancement therefore provides an effective and robust means for harnessing fish-fish hydrodynamic interactions in a school. In addition to confirming the potential energetic benefits of schooling, the LEV enhancement mechanism could be exploited in coordinated swimming of bioinspired multi-vehicle or multi-foil flapping foil propulsion systems.