External Clamping Research Articles

Comparing Multipin Clamps With Outriggers With Standard Clamps for Lower Extremity Periarticular External Fixation: Similar Radiographic and Clinical Outcomes.

Staged treatment of high-energy periarticular tibia fractures involves temporization with closed reduction and external fixation, aiming to provide early reduction and stabilization while mitigating soft-tissue complications. Various external fixator configurations exist, including those that use a "multipin" clamp capable of holding multiple pins but limiting pin placement to a single plane. The purpose of this study was to compare clinical and radiographic outcomes and associated costs of standard and multipin outrigger clamp constructs in tibial plateau and pilon fractures treated with temporary external fixation. We hypothesized that use of the multipin clamp may be associated with poorly aligned reductions and increased complication rates. A retrospective review of 100 patients with periarticular tibial plateau (AO/OTA: 41B/C) or pilon (43B/C) fracture at a Level 1 trauma center from 2014 to 2023 was conducted. Patient, injury, and complication characteristics were collected. Patients were categorized based on the external fixator clamp used: multipin (MP) or standard (S). Clinical outcomes and complication rates were assessed. Radiographic alignment was evaluated by the change in anterior and lateral distal tibial angles, and sagittal plane translation for pilon fractures, and medial and posterior proximal tibial angles for plateau fractures. 70 patients underwent standard (25 pilon, 45 plateau) and 30 multipin (10 pilon, 20 plateau) external fixation. MP and S groups showed no notable differences in demographics or injury characteristics. Both groups demonstrated comparable complication rates and radiological alignment outcomes, with no notable differences observed. MP constructs were more costly than standard systems. In this retrospective study of 100 patients, there was no difference in radiographic or clinical outcomes between the standard frame and multipin frame groups. Typical costs for the multipin frame constructs were $635 to $1249 more than the standard frame constructs.

Rapid repair of RC columns with post-tensioned external clamps

A recent technique for repair of damaged reinforced concrete (RC) columns is reviewed. The technique involves the application of external post-tensioned clamps. The clamps are composed of steel angles and high-strength steel rods. The pairs of angles are placed on the corners of the cross-section, and they are connected with steel rods to each other. To evaluate the effectiveness of the repair technique, four large-scale RC columns with insufficient transverse reinforcement were subjected to lateral displacement reversals and constant axial load. The tests were conducted in two phases: initial testing of columns with none to light transverse reinforcement, followed by the application of clamps on the damaged columns and further testing. The study focused on the efficacy of the clamps to a) restore the lateral-carrying capacity of damaged RC columns, and b) increase drift capacity. Variations in lateral expansion of the column core and their plausible correlations with damage and ‘repairability’ are examined. Within the conditions investigated, two key requirements are proposed for safe column repair: 1) the concrete in damaged columns with cross-sectional expansion exceeding 1% should be replaced or repaired before clamps are applied as a repair measure, and 2) clamps should be proportioned to resist 100% of the maximum plausible shear demand even though perceptible contributions to shear resistance attributable to the concrete were observed in columns repaired before excessive expansion occurred. In columns with crisscrossing inclined cracks leading to lateral cross-sectional expansion of up to 1%, clamps were observed to provide effective shear resistance comparable to what conventional transverse reinforcement can provide.

Biomechanical Evaluation of a Locally Manufactured Modular External Fixator for Tibial Shaft Fractures

Background: Modular external fixations used in the Philippines are manufactured abroad, leading to high costs and limited availability, making them unaffordable for most Filipino patients. The reliability of some external fixators is limited because not all have undergone biomechanical testing. Objective: This study aims to determine the biomechanical stability of locally manufactured modular external fixator clamps (iFIX) versus commercially available fixators (Roger-Anderson) for tibial shaft fractures. Methodology: The biomechanical stability (stiffness, yield, ultimate strength) under loading of the local prototypes compared with the commercially available fixators. Result: No slippage was observed in all rods, pins, and clamps in all groups. No bending occurred in any rods or pins in all groups. There was also no apparent deformation of the internal threading of the pins within the tibial analogs. The commercial fixator group’s ultimate load to failure up was double (110.57% difference) that of the local prototype. Conclusion: The differences in the biomechanical performance between the iFIX and Roger-Anderson clamps may be attributed to variations in clamp material composition. The iFIX fixator exhibited lower stiffness but did not display deformation under axial loading, component displaced slippage, or thread loosening, making it comparable to the commercial fixator.

Simple model of pulmonary hypertension secondary to left heart pressure overload induced by partial intravascular occlusion of the ascending aorta.

Pulmonary hypertension is a group of diseases characterized by elevated pulmonary artery pressure and pulmonary vascular resistance with significant morbidity and mortality. The most prevalent type is pulmonary hypertension secondary to left heart disease (PH-LHD). The available experimental models of PH-LHD use partial pulmonary clamping by technically nontrivial open-chest surgery with lengthy recovery. We present a simple model in which the reduction of the cross-sectional area of the ascending aorta is achieved not by external clamping but by partial intravascular obstruction without opening the chest. In anesthetized rats, a blind polyethylene tubing was advanced from the right carotid artery to just above the aortic valve. The procedure is quick and easy to learn. Three weeks after the procedure, left heart pressure overload was confirmed by measuring left ventricular end-diastolic pressure by puncture (1.3 ± 0.2 vs. 0.4 ± 0.3 mmHg in controls, mean ± SD, P < 0.0001). The presence of pulmonary hypertension was documented by measuring pulmonary artery pressure by catheterization (22.3 ± 2.3 vs. 16.9 ± 2.7 mmHg, P = 0.0282) and by detecting right ventricular hypertrophy and increased muscularization of peripheral pulmonary vessels. Contributions of a precapillary vascular segment and vasoconstriction to the increased pulmonary vascular resistance were demonstrated, respectively, by arterial occlusion technique and by normalization of resistance by a vasodilator, sodium nitroprusside, in isolated lungs. These changes were comparable, but not additive, to those induced by an established pulmonary hypertension model, chronic hypoxic exposure. Intravascular partial aortic obstruction offers an easy model of pulmonary hypertension induced by left heart disease that has a vasoconstrictor and precapillary component.NEW & NOTEWORTHY We present a new, simple model of a clinically important type of pulmonary hypertension, that induced by left heart failure. Left ventricular pressure overload is induced in rats by inserting a blinded cannula into the ascending aorta via carotid artery access. This partial intravascular aortic obstruction, which does not require opening of the chest and prolonged recovery, causes pulmonary hypertension, which has a precapillary and vasoconstrictor as well as a vascular remodeling component.

A comparative study of functional outcome of percutaneous kirschner wire fixation versus philos plating of proximal humerus fractures

: Proximal humerus fractures, accounting for approximately 5% of all fractures, pose a significant challenge in orthopedic management due to their complex anatomy and diverse fracture patterns. Treatment options range from conservative methods to various surgical interventions, each with its pros and cons. This study specifically compares two commonly employed surgical techniques: Open reduction &amp; internal fixation with PHILOS plate and percutaneous k-wire fixation with/without external clamps. This study aims to address the effectiveness of each technique by evaluating functional outcomes using validated scoring systems like the Constant-Murley Score. To assess the functional outcomes of two surgical treatment methods (K-wire application and PHILOS plate fixation) for proximal humerus fractures. : A randomized prospective study was conducted on patients coming to the Orthopaedics outpatient department or casualty of tertiary care hospital for a duration of 1 year from Dec 2022 to Nov 2023. A total of 18 patients were included in the study. The mean Constant- Murley Score (CMS) was 81 +/- 6.13 for the PHILOS plating group and 76.88 +/- 7.37 for the K-wire treated group with a p-value of 0.08. The results for CMS were excellent in 22.2% of patients and good in 66.7% of patients in PHILOS treated group and excellent for 11.11%, good for 66.67% and satisfactory for 22.2% in the K-wire treated group. Both groups achieved satisfactory functional outcomes with CM Score at the final follow-up. Both techniques achieved favorable outcomes, with a majority of patients in both groups (88.89% for PHILOS and 77.78% for K-wire) achieving good to excellent results based on the CMS scores.

Robotic Mitral Valve Repair: Impact of Experience on Results and Complex Mitral Disease Treatment.

Background/Objectives: Robotically assisted mitral valve (MV) surgery is the least invasive surgical approach to the MV. The aim of the present study is to report our experience with robotically assisted MV repair, trying to define how experience could impact on postoperative results. Methods: This is a retrospective study on 144 patients who underwent robotic MV repair from November 2011 to March 2023. Patients were divided in two groups: Group 1, including 39 patients (November 2011-January 2013) operated using the Da Vinci Si system, and Group 2, including 105 patients operated (February 2020-March 2023) using the new Da Vinci Xi system. Results: Mean age was 58 ± 10 years. Increased use of external aortic clamp was observed in Group 2. A significant reduction of surgical times was observed: cardiopulmonary bypass time was 155 ± 44 min in Group 1 and 121 ± 36 min in Group 2 (p = 0.002), whereas cross-clamp time was 112 ± 25 min in Group 1 and 68 ± 39 min in Group 2 (p < 0.001). In-hospital mortality was 0.7%, and 10-year survival was 96 ± 2%. Freedom from reoperation was 100%. A higher percentage of complex and most complex MV repairs were performed in Group 2 (36% in Group 1 vs. 52% in Group 2, p = 0.001). Conclusions: Robotic-assisted MV repair is associated with excellent results. Experience is a key element to overcome the limitations of this technology. Finally, the robotic platform could improve results in difficult MV repair.

Bailout Distal Internal Carotid Artery Stenting after Carotid Endarterectomy: Indications, Technique, and Outcomes

Distal internal carotid artery (ICA) stenting may be employed as a bailout maneuver when an inadequate end point or clamp injury is encountered at the time of carotid endarterectomy (CEA) in a surgically inaccessible region of the distal ICA. We sought to characterize the indications, technique, and outcomes for this infrequently encountered clinical scenario. We performed a retrospective review of all patients who underwent distal ICA stenting at the time of CEA at our institution between September 2008 and July 2022. Procedural details and postoperative follow-up were reviewed for each patient. Six patients were identified during the study period. All were male with an age range of 63 to 82years. Five underwent carotid revascularization for asymptomatic carotid artery stenosis, and one patient was treated for amaurosis fugax. Three patients were on dual antiplatelet therapy preoperatively, whereas 2 were on aspirin monotherapy, and one was on aspirin and low-dose rivaroxaban. Five patients underwent CEA with patch angioplasty, and one underwent eversion CEA. The indication for stenting was distal ICA dissection due to clamp or shunt injury in 2 patients and an inadequate distal ICA end point in 4 patients. In all cases, access for stenting was obtained under direct visualization within the common carotid artery, and a standard carotid stent was deployed with its proximal aspect landing within the endarterectomized site. Embolic protection was typically achieved via proximal common carotid artery and external carotid artery clamping for flow arrest with aspiration of debris before restoration of antegrade flow. There was 100% technical success. Postoperatively, 2 patients were found to have a cranial nerve injury, likely occurring due to the need for high ICA exposure. Median length of stay was 2days (range 1-7days) with no instances of perioperative stroke or myocardial infarction. All patients were discharged on dual antiplatelet therapy with no further occurrence of stroke, carotid restenosis, or reintervention through a median follow-up of 17months. Distal ICA stenting is a useful adjunct in the setting of CEA complicated by inadequate end point or vessel dissection in a surgically inaccessible region of the ICA and can minimize the need for high-risk extensive distal dissection of the ICA in this situation.

Dynamic property evaluation of pipeline clamp based on analyzing the propagation characteristics of flexural wave in pipeline

The external clamp of hydraulic pipeline plays an important role in strengthening pipeline stiffness and improving vibration attenuation ability. In this study, wave propagation method is proposed to evaluate the translational and rotational stiffness and their loss factors of the clamp by analyzing the flexural wave propagation characteristics of pipeline. In order to validate the measured dynamic properties, experimental modal analysis was performed on the two-end elastically-supported pipeline. By modelling the pipeline with translational and rotational edge restraints, the analytical modal frequency parameters, wave numbers, and waveform coefficients were obtained. By comparing of the first-order flexural mode frequencies between experiment and analysis, the dynamic stiffness predicted by the wave propagation method was validated. The effects of the magnitude of torque, direction, clamping torque cycle, and clamp size on the complex dynamic properties of pipeline clamp were investigated. The proposed wave propagation method allows non-destructive continuous monitoring of a clamp stiffness, provides additional information about the vibration attenuation feature. It has advantages in clamp applications and is an effective methodology for measuring the dynamic properties of viscoelastic materials.

Shear Strength of Reinforced Concrete Columns with External Post-Tensioned Clamps

Shear Strength of Reinforced Concrete Columns with External Post-Tensioned Clamps

Development and Validation of a Model for Operationally Seized Bolted Joints for the Research on Gentle Bolt Disassembly

Thread galling and seizure is a major impediment to the disassembly of bolted joints. The near-locking of the joint can result in damage to or even breakage of parts of the bolt when a seized bolt is unscrewed. In maintenance, repair, and overhaul (MRO) of complex capital goods such as aircraft engines, seized bolts result in additional disassembly and repair work. Especially in the aircraft engine's hot-section, joints are vulnerable to seizure and galling due to material pairing and thermal conditions. Extensive investigation of the disassembly of joints seized during operation may not be implemented during maintenance orders. The manufacturer's specifications and aviation safety authorities only permit predetermined tools. Therefore, artificial samples are needed to perform fundamental experiments. In this article, a model for artificially and reproducibly replicating seized bolted joints is presented. By adding and adjusting an external clamping force on the thread, the loosening torque can be adjusted as a function of the additional forces. The statistical evaluation of performed experiments will validate the assumed relationship between clamping force and loosening torque. Therefore, this model provides the basis for further disassembly studies by providing artificial and reproducible samples.

Cost and Clinical Outcomes Evaluation Between the Endoaortic Balloon and External Aortic Clamp in Cardiac Surgery.

Endoaortic balloon occlusion facilitates cardioplegic arrest during minimally invasive surgery (MIS). Studies have shown endoclamping to be as safe as traditional aortic clamping. We compared outcomes and hospital costs of endoclamping versus external aortic occlusion in a large administrative database. There were 52,882 adults undergoing eligible cardiac surgery (October 2015 to March 2020) identified in the Premier Healthcare Database. Endoclamp procedures (n = 419) were 1:3 propensity score matched to similar procedures using external aortic occlusion (n = 1,244). Generalized linear modeling measured differences in in-hospital complications (major adverse renal and cardiac events, including mortality, new-onset atrial fibrillation, acute kidney injury [AKI], myocardial infarction [MI], postcardiotomy syndrome, stroke/transient ischemic attack [TIA], and aortic dissection) and length of stay (LOS). The mean age was 63 years, and 53% were male (n = 882). The majority (93%, n = 1,543) were mitral valve procedures, and 17% of procedures (n = 285) were robot-assisted. Total hospitalization costs were not statistically significantly different between the 2 groups ($52,158 vs $49,839, P = 0.06). The median LOS was significantly shorter in the endoclamp group (incident rate ratio = 0.87, P < 0.001). Mortality, atrial fibrillation, AKI, and stroke/TIA were similar between the 2 groups. MI and postcardiotomy syndrome were lower in the endoclamp group (odds ratio [OR] = 0.14, P = 0.006, and OR = 0.27, P = 0.005). There were no aortic dissections in the endoclamp group. Aortic endoclamping in MIS was associated with similar costs, shorter LOS, no dissections, and comparably low mortality and stroke rates when compared with external clamping in this hospital billing dataset. These results demonstrate the clinical safety and efficacy of endoaortic balloon clamping in a real-world setting. Further studies are warranted.

Automatic identification of intracranial pressure waveform during external ventricular drainage clamping: segmentation via wavelet analysis

Objective. The objective of this study is to develop and validate a method for automatically identifying segments of intracranial pressure (ICP) waveform data from external ventricular drainage (EVD) recordings during intermittent drainage and closure. Methods. The proposed method uses time-frequency analysis through wavelets to distinguish periods of ICP waveform in EVD data. By comparing the frequency compositions of the ICP signals (when the EVD system is clamped) and the artifacts (when the system is open), the algorithm can detect short, uninterrupted segments of ICP waveform from the longer periods of non-measurement data. The method involves applying a wavelet transform, calculating the absolute power in a specific range, using Otsu thresholding to automatically identify a threshold, and performing a morphological operation to remove small segments. Two investigators manually graded the same randomly selected one-hour segments of the resulting processed data. Performance metrics were calculated as a percentage. Results. The study analyzed data from 229 patients who had EVD placed following subarachnoid hemorrhage between June 2006 and December 2012. Of these, 155 (67.7%) were female and 62 (27%) developed delayed cerebral ischemia. A total of 45 150 h of data were segmented. 2044 one-hour segments were randomly selected and evaluated by two investigators (MM and DN). Of those, the evaluators agreed on the classification of 1556 one-hour segments. The algorithm was able to correctly identify 86% (1338 h) of ICP waveform data. 8.2% (128 h) of the time the algorithm either partially or fully failed to segment the ICP waveform. 5.4% (84 h) of data, artifacts were mistakenly identified as ICP waveforms (false positives). Conclusion. The proposed algorithm automates the identification of valid ICP waveform segments of waveform in EVD data and thus enables the inclusion in real-time data analysis for decision support. It also standardizes and makes research data management more efficient.

Benchmarking Hospital Practices and Policies on Intrahospital Neurocritical Care Transport: The Safe-Neuro-Transport Study.

An electronic survey was administered to multidisciplinary neurocritical care providers at 365 hospitals in 32 countries to describe intrahospital transport (IHT) practices of neurocritically ill patients at their institutions. The reported IHT practices were stratified by World Bank country income level. Variability between high-income (HIC) and low/middle-income (LMIC) groups, as well as variability between hospitals within countries, were expressed as counts/percentages and intracluster correlation coefficients (ICCs) with a 95% confidence interval (CI). A total of 246 hospitals (67% response rate; n = 103, 42% HIC and n = 143, 58% LMIC) participated. LMIC hospitals were less likely to report a portable CT scanner (RR 0.39, 95% CI [0.23; 0.67]), more likely to report a pre-IHT checklist (RR 2.18, 95% CI [1.53; 3.11]), and more likely to report that intensive care unit (ICU) physicians routinely participated in IHTs (RR 1.33, 95% CI [1.02; 1.72]). Between- and across-country variation were highest for pre-IHT external ventricular drain clamp tolerance (reported by 40% of the hospitals, ICC 0.22, 95% CI 0.00-0.46) and end-tidal carbon dioxide monitoring during IHT (reported by 29% of the hospitals, ICC 0.46, 95% CI 0.07-0.71). Brain tissue oxygenation monitoring during IHT was reported by only 9% of the participating hospitals. An IHT standard operating procedure (SOP)/hospital policy (HP) was reported by 37% (n = 90); HIC: 43% (n= 44) vs. LMIC: 32% (n = 46), p = 0.56. Amongst the IHT SOP/HPs reviewed (n = 13), 90% did not address the continuation of hemodynamic and neurophysiological monitoring during IHT. In conclusion, the development of a neurocritical-care-specific IHT SOP/HP as well as the alignment of practices related to the IHT of neurocritically ill patients are urgent unmet needs. Inconsistent standards related to neurophysiological monitoring during IHT warrant in-depth scrutiny across hospitals and suggest a need for international guidelines for neurocritical care IHT.

Design and experiment of an auxiliary device for dragging submarine cable with external surface clamp

To extend the tugging distance of submarine cables inside mooring tubes, this paper presents an auxiliary submarine cable tugging device with an external surface clamp. There are few existing auxiliary tug devices for submarine cables, and it is necessary to develop such a device that is suitable for long distances and large-diameter heavy submarine cables. The structural size of the cable is analyzed, and the drag force required by the marine cable and the obstacle surmounting ability of the auxiliary device are examined. The friction-reducing performance of the device is verified by experiments using short and long sea cables. The experimental results show that the marine cable dragging auxiliary device reduces the friction by more than 50%, enabling dragging distances to reach 1500 m in the underwater protective tube.

Study and Validation of a Novel Grouting Clamp Type Deepwater Oilfield Pipeline Repair Method Based on Computational Fluid Dynamics

In order to handle the corrosion of underwater production pipe sinks in deepwater oil fields, a non-solid phase silicone plugging agent, an external clamp, and an underwater injection tool are combined in this paper’s innovative pipeline repair technique proposal. The optimal main agent to curing the agent ratio for non-solid phase silicone plugging agents was found to be 100:25, which was achieved through an experimental examination of the curing process. The compressive and cementing strength changes in the curd plugging agent were disclosed by testing and evaluating the mechanical behavior of the plugging agent. In addition, the limits of the compressive and cementing strength were found to be 143 MPa and 11.6 MPa, respectively. Based on this, a computational-fluid-dynamics(CFD)-based analytical approach of the complicated flow field in a deep sea environment on the eroding impact of a plugging agent was developed. Through numerical simulation testing, the mathematical relationship between the plugging agent’s maximum pressure and the flow field’s velocity was established. The limits of saltwater and petroleum oil on the erosion of the plugging agent were found to be 4.19 MPa and 3.29 MPa, respectively, which are values that are far below their strength limits. In this way, the viability and efficacy of this novel pipeline repair technique were confirmed. The study presented in this paper sets the groundwork for an in-depth analysis and optimization of novel corrosion control solutions for deepwater oil field subsea process pipes.

A Retrospective Evaluation of Endo-Aortic Balloon Occlusion Compared to External Clamping in Minimally Invasive Mitral Valve Surgery

We compare outcomes of endo-aortic balloon occlusion (EABO) vs external aortic clamping (EAC) in patients undergoing minimally invasive mitral valve surgery (MIMVS) in the Society of Thoracic Surgeons (STS) Adult Cardiac Surgery Database. Adults undergoing mitral valve surgery (July 2017-December 2018) were identified within the STS database (N=60,607). Total 7,978 patients underwent a minimally invasive approach (including robotically assisted). About 1,163 EABO patients were 1:1 propensity-matched to EAC patients using exact matching on age, sex, and type of mitral procedure, and propensity score average matching for 16 other risk indicators. Early outcomes were compared. Categorical variables were compared using logistic regression; hospital and intensive care unit length of stay were compared using negative binomial regression. In the matched cohort, mean age was 62 years; 35.9% were female, and 86% underwent mitral valve repair. Cardiopulmonary bypass time was shorter for EABO vs EAC group (125.0 ± 53.0 vs 134.0 ± 67.0 minutes, P=0.0009). There was one aortic dissection in the EAC group and none in the EABO group (P value > 0.31), and no statistically significant differences in cross-clamp time, major intraoperative bleeding, perioperative mortality, stroke, new onset of atrial fibrillation, postoperative acute kidney injury, success of repair. Median hospital LOS was shorter for EABO vs EAC procedures (4 vs 5 days, P < 0.0001). In this large, retrospective, STS database propensity-matched analysis ofpatients undergoing MIMVS, we observed similar safety outcomes for EABO and EAC, including no aortic dissections in the EABO group. The EABO group showed slightly shorter CPB times and hospital LOS.

Finite Element Analysis and Material Selection of 3D-Printed External Metacarpal Fixator Clamp

One of the most common orthopedic injuries is fracture found on the metacarpal bones of the hand. It is composed of 14-28 % emergency room cases in hospitals. Despite its frequent occurrence, they are often neglected which may lead to major disability or deformity that limits movement. This is merely due to the high cost of treatment which includes the usage of an external metacarpal fixator. In this paper, an external metacarpal fixator clamp with additive manufacturing polymer material is evaluated based on scenarios of flexural and compressive load on the metacarpal bone with simulated fracture. The material is selected using Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) multi-attribute decision making. Finite Element Analysis (FEA) is also done with increasing load per scenario. The result shows nylon as a suitable polymer additive manufacturing material for external metacarpal fixator. The equivalent stress on the fixator clamp and the deformation at a maximum load of 120 N is less than 1 Mpa and 0.5 mm, respectively. This comprises the suitability of 3D printed polymer material for an external metacarpal application. Future studies of comparison of FEA simulation and actual 3D printed part is recommended.

Comparative myocardial protection of endoaortic balloon versus external clamp in minimally invasive mitral valve surgery.

Minimally invasive mitral valve surgery leads to shorter postoperative recovery time, cosmetic advantages and significant pain reduction compared with the standard sternotomy approach. Both an external aortic clamp and an endoaortic balloon occlusion can be used to manage the ascending aorta and the myocardial protection. In this study, we aimed to compare these two strategies in terms of effectiveness of myocardial protection and associated early postoperative outcomes. We investigated the retrospective records of prospectively collected data of patients treated by minimally invasive mitral valve surgery from March 2014 to June 2019. A total of 180 cases (78 in the external aortic clamp group and 102 in the endoaortic balloon clamp group) were collected. A propensity weighting analysis was adopted to adjust for baseline variables. The endoaortic balloon clamp presented higher EuroSCORE II (higher reoperative surgery rate). The intra- and postoperative data were similar between the two groups: the postoperative troponin-I levels, peak of serum lactates and rate of myocardial infarction were also comparable. The endoaortic clamp group recorded longer operative, cardiopulmonary bypass and cross-clamp times. The external clamp group showed a higher rate of postoperative atrial fibrillation and conduction block. In experienced centers, the use of the endoaortic balloon clamp is safe, reproducible and comparable to the external aortic clamp regarding the effectiveness of myocardial protection: its employment might facilitate minimally invasive mitral valve surgery.

Cost Variation in Temporizing External Fixation of Tibial Plateau and Pilon Fractures: Is There Room to Improve?

IntroductionExternal fixator costs have been shown to be highly variable. Current information on external fixator costs and cost drivers is limited. The aim of this study was to examine the cost variation as well as the patient-, injury-, and surgeon-related cost drivers associated with temporizing external fixation constructs in tibial plateau and pilon fracture management. Materials and MethodsA retrospective review was conducted to identify isolated tibial plateau and pilon fractures treated with temporizing external fixation from 2006-2018 at a level 1 trauma center. Inclusion criteria were based on fractures managed with primary external fixation, skeletal maturity, and isolated ipsilateral fracture fixation. Fracture patterns were identified radiographically using Schatzker, Weber, and OTA classification systems. Implant costs were determined using direct purchase price from the institution. The primary outcome was the external fixator total construct cost. Clinical covariates and secondary outcomes, namely unplanned reoperations, were extracted. Factors associated with cost (i.e. cost drivers) were identified via multivariable regression analysis. ResultsA total of 319 patients were included in this study (121 tibial plateau and 198 pilon fractures). Mean plateau construct cost was $5,372.12 and mean pilon construct cost was $3,938.97. Implant cost correlated poorly with demographic (r2=0.01 & r2=0.01), injury-independent (r2<0.01 & r2=0.03), and fracture pattern classifications (r2=0.03 & r2=0.02). Traumatologists produced significantly cheaper implants for pilon fractures (p=0.05) but not for plateau fractures (p=0.85). There was no difference in construct cost or components between patients that underwent unplanned reoperation and those that did not for both tibial plateau (p>0.19) and pilon (p>0.06). Clamps contributed to 69.9% and 77.3% of construct costs for tibial plateau and pilon, respectively. The most cost-efficient fixation constructs for tibial plateau and pilon fractures were the following respectively: of 5 clamps, 2 bars, and 4 pins; and of 4 clamps, 2 bars, and 3 pins. ConclusionsThere is large cost variation in temporizing external fixation management. Cost drivers included surgeon bias and implant preference as well as use of external fixator clamps. Introducing construct standardization will contain healthcare spending without sacrificing patient outcomes. LEVEL OF EVIDENCELevel III. Retrospective Cohort

Influence of external clamping pressure on nanoscopic mechanical deformation and catalyst utilization of quaternion PtC catalyst layers for PEMFCs

The external clamping pressure (CP) has a significant influence on the morphology, transport characteristics, and performance of catalyst layers (CLs) of the proton exchange membrane fuel cells (PEMFCs). Therefore, comprehensive understanding the nanoscale mechanical deformation and its impact on the utilization of precious platinum catalysts are extremely important for designing effective CLs. In this study, the effect of external CP on the morphology, interconnectivity and electrochemical catalyst utilization of CLs is explored. The quaternion carbon-supported platinum (PtC) CL agglomerate nanostructures are reconstructed for the predetermined fuel cell catalyst compositions containing platinum (Pts) supported on carbon black, ionomers, and pores. The compression model is developed using an effective medium theory based on a unit cell and implemented on the reconstructed CL domain with a 98% confidence level. The results of CL compression model are validated based on the experimental data from previous studies. The effect of compression on the thickness, porosity, local pore size distribution, electron-conducting PtC, and proton-conducting electrolyte are investigated in detail because these parameters are critical for the transport properties and performance of the CLs. Moreover, the numerical experiments are repeated for a range of CL compositions by varying the ionomer-to-carbon weight ratio (I/C) from 0.5 to 1.2 for different CPs (0, 1, and 2 MPa). The numerical results show that the interconnectivities of PtC, ionomer, and pore phases are strongly dependent on the applied CPs. Finally, the electrochemical performance of the CLs is compared for the maximum electrochemical catalyst utilization factor (ECUF) to enhance overall fuel cell performance. Insights gathered from this modeling study can be used for further investigation of mass transfer in compressed PtC CLs for better understanding fuel cell performance.