Measurement Of Contact Pressure Research Articles

Neonatal Noninvasive Ventilation Nasal Mask Interface Pressure and the Inter-Individual Variation of Mask Placement.

The 2014 American Academy of Pediatrics recommendation for CPAP as an alternative to mechanical ventilation for treatment of neonatal respiratory distress prompted a rapid shift to noninvasive ventilation (NIV). Since most patients receive nasal bubble CPAP (a form of NIV), a concomitant increase in nasal pressure injuries followed. This prospective observational study aims to develop strategies to reduce nasal mask pressure injury in neonates by 1.) quantifying CPAP mask-interface pressure and 2.) assessing placement variability. A 1F MEMS Connect pressure sensor (Millar®) was modified for contact pressure measurements with silicone embedding and calibrated. The CPAP generator and interface components were sized for a 24-week neonatal simulator. Thirteen neonatal ICU staff placed the simulator on CPAP at 6 cmH2O and 8 L/min of flow with no humidification. Pressure was measured at three locations (the forehead, nasal bridge, and philtrum) in triplicate (three measurements per site). Descriptive statistics, a location-specific, one-way analysis of variance (ANOVA) with a Tukey post hoc test, and a two-sample paired t-test of the means of the first and last triplicate were performed (Minitab, LLC). Pressure ranged from 12.3 to 377.3 mmHg. The mean (SD) interface pressure at the philtrum was significantly higher than both the nasal bridge and the forehead (philtrum: 173.9 (101.3), nasal bridge: 67.79 (28.9), and forehead 79.02 (36.87), p ˂ 0.001). CPAP fixation varied, including bonnet placement, trunk angle, mask compression, use of hook and loop extenders, and level of vigorous bubble feedback achieved. This study developed a modified pressure sensor for quantifying the pressure exerted by a nasal mask on facial skin. Maximum pressures were higher than those previously reported. Inter-individual differences were present in both quantitative and qualitative measures of pressure. Reduction of NIV-associated pressure injuries may be achieved through NIV fixation technique training and improved nasal mask stability and size increments.

The Effect of First Metatarsal Shortening and Sagittal Displacement on Forefoot Pressure in Minimally Invasive Hallux Valgus Correction.

Minimally invasive (MIS) treatment of hallux valgus (HV) deformity is increasing in popularity. A 2-mm diameter burr is used to create a distal first metatarsal osteotomy prior to capital fragment translation and fixation. The metatarsal will shorten by the burr's diameter (2 mm). Plantar or dorsal capital fragment displacement may also cause load transference and possibly transfer metatarsalgia. The purpose of this study is to examine the effect of MIS HV on forefoot loading mechanics with respect to metatarsal shortening and sagittal plane displacement. Four lower-limb cadaveric specimens were studied. A pedobarography pressure-sensing mat was used to record forefoot plantar pressure in a controlled weight-bearing stance position. Control and postosteotomy measurements were obtained with the capital fragment fixated in 3 possible positions: 0 mm, 5 mm dorsal, and 5 mm plantar displacement. Pedobarography data yielded pressure data within measurable graphical depictions. Raw mean contact pressure measurements were taken under the first and fourth metatarsal heads to establish medial and lateral forefoot loading pressure ratios. An a priori power analysis was performed based on previous peer-reviewed pedobarographic data, and our study was adequately powered. Around 40 measurements were recorded, and ratios of medial-to-lateral forefoot loading were constructed. Medial forefoot pressure control versus 0 mm displacement, and control versus dorsal displacement were not found to be statistically significant (p = 0.525, p = 0.55, respectively). Medial pressure significantly increased when comparing control versus plantar displacement (P = .006). Lateral pressure significantly increased with dorsal displacement of the osteotomy (P = .013). Our study found that MIS HV correction did not cause an increase in lateral forefoot pressure loading when sagittal plane displacements were controlled. Plantar displacement increased medial loading, and dorsal displacement increased lateral loading. It may be valuable for surgeons to consider metatarsal head position postosteotomy, as a decrease in medial loading and subsequent increase in lateral loading may lead to lateral forefoot pain and transfer metatarsalgia. IV.

Identification of excessive contact pressures under hand orthosis based on finite element analysis.

Implicit magnitudes and distribution of excessive contact pressures under hand orthoses hinder clinicians from precisely adjusting them to relieve the pressures. To address this, contact pressure under a hand orthosis were analysed using finite element method. This paper proposed a method to numerically predict the relatively high magnitudes and critical distribution of contact pressures under hand orthosis through finite element analysis, to identify excessive contact pressure locations. The finite element model was established consisting of the hand, orthosis and bones. The hand and bones were assumed to be homogeneous and elastic bodies, and the orthosis was considered as an isotropic and elastic shell. Two predictions were conducted by assigning either low (fat) or high (skin) material stiffness to the hand model to attain the range of pressure magnitudes. An experiment was conducted to measure contact pressures at the predicted pressure locations. Identical pressure distributions were obtained from both predictions with relatively high pressure values disseminated at 12 anatomical locations. The highest magnitude was found at the thumb metacarpophalangeal joint with the maximum pressure range from 13 to 78 KPa. The measured values were within the predicted range of pressure magnitudes. Moreover, 6 excessive contact pressure locations were identified. The proposed method was verified by the measurement results. It renders understanding of interface conditions underneath the orthosis to inform clinicians regarding orthosis design and adjustment. It could also guide the development of 3D printed or sensorised orthosis by indicating optimal locations for perforations or pressure sensors.

Optimizing Reverse-Engineered Finite Element Models for Accurate Predictions of Experimental Measurements

This study investigates the challenges of reverse engineering in finite element modelling of sheet metal forming, specifically for the Volvo XC90 front door inner component. Advanced models incorporating anisotropic behaviour of steel and non-linear friction are compared against actual real-world measurements. The methodology involves simplifying complex continuous parameters into more manageable representative data sets and assessing model accuracy under both uniform and varied blank holder force settings, guided by measured contact pressure distributions. Although the results indicate an improvement in accuracy, they underscore the need for additional methodological improvements and more accurate replication of tooling effects to enhance the fidelity and effectiveness of these models.

Upper extremity contact pressure measurement in robot-assisted pelvic surgery

Upper extremity complications are often a problem in robot-assisted pelvic surgery (RAPS) with the lithotomy-Trendelenburg position (LT-position). This study focused on upper extremity contact pressure (UEP) and examined the relationship between UEP and upper extremity complications. From May 2020 to April 2022 at the University of Tokyo Hospital, UEP was measured in 155 patients undergoing RARP and 20 patients undergoing RARC. A total of 350 sets of UEP were investigated in this study. UEP was measured using a portable interface pressure sensor (Palm Q, Cape CO., Kanagawa, Japan) in the preoperative lithotripsy position (L-position), preoperative LT-position, and postoperative L-position. UEP was increased in the preoperative LT-position than in the preoperative L-position (right side 5.2 mmHg vs. 17.1 mmHg, left side 5.3 mmHg vs. 17.1 mmHg, P < 0.001, respectively), and was decreased in the postoperative L-position than in preoperative LT-position (right side 17.1 mmHg vs. 10.8 mmHg, left side 17.1 mmHg vs. 10.6 mmHg, P < 0.001, respectively). Eleven upper extremities developed shoulder pain. UEP of the preoperative LT-position tended to be higher in the upper extremity exhibiting shoulder pain (25.6 mmHg (15.4–30.3) vs. 17.1 mmHg (12.0–24.4) P = 0.0901). UEP measurements may help prevent postoperative shoulder pain.

The Effect of First Metatarsal Shortening and Sagittal Displacement on Forefoot Pressure in MIS Hallux Valgus Correction

Introduction/Purpose: Minimally invasive surgical (MIS) treatment of hallux valgus (HV) deformity is increasing in popularity. A 2mm-diameter burr is used to create a distal first metatarsal osteotomy prior to capital fragment translation and fixation. The metatarsal will shorten by the burr’s diameter (2mm). Plantar or dorsal capital fragment displacement may also cause load transference and possibly transfer metatarsalgia. In this study, we examine the effect of MIS HV on forefoot loading mechanics with respect to metatarsal shortening and sagittal plane displacement. Methods: Four lower-limb cadaveric specimens were studied. A pedobarography pressure-sensing mat was used to record forefoot plantar pressure in a controlled weightbearing stance position.10 Control and post-osteotomy measurements were obtained with the capital fragment fixated in 3 possible positions: 0mm, 5mm dorsal, and 5mm plantar displacement. Pedobarography data yielded pressure data within measurable graphical depictions. Raw mean contact pressure measurements were taken under the first and fifth metatarsal heads to establish medial and lateral forefoot loading pressure ratios. A priori power analysis was performed based on previous peer-reviewed pedobarographic data and our study was adequately powered. Results: 40 measurements were recorded and ratios of medial-to-lateral forefoot loading were constructed. Medial forefoot pressure change control versus 0mm displacement, and control versus dorsal displacement was not found to be statistically significant (p=0.525, p=0.55 respectively). Significant medial pressure increase was identified comparing control versus plantar displacement (p=0.006). Lateral pressure increased significantly with dorsal displacement of the osteotomy (p=0.013). Conclusion: MIS hallux valgus correction does not appear to cause increase in lateral forefoot pressure loading when sagittal plane displacements are controlled. Plantar displacement increases medial loading, and dorsal displacement increases lateral loading. The clinician must consider metatarsal head position post-osteotomy, as decrease in medial loading and subsequent increase in lateral loading may lead to lateral forefoot pain and transfer metatarsalgia.

Simulation and experimental study on contact pressure distribution of contact interface in single and double bolted connection structures

Bolted joints play an important role in aerospace, machinery manufacturing, weapons and other fields, and the contact pressure distribution at the connection interface seriously affects the service performance of the bolts. Contact pressure analysis is an essential basis and reference for structural design, calibration, inspection, and safety monitoring of bolted connection structures. Considering the preload force and frictional contact between the joint components, a block mapping hexahedron mesh generation and finite element modeling method for bolted connections is presented, and the finite element models of single and double bolted structures are constructed. Then, an experimental test platform for measuring contact pressure distribution is constructed. Comparison of finite element analysis results with experimental results for the contact pressure distribution in the single and double-bolted joints; the root mean squared error of contact pressure distribution is less than 5%, which verifies the effectiveness of the finite element models. After that, the models are used to study the contact pressure distribution in single-bolted joints and contact pressure coupling effect of double-bolted joints, and the normal stress distribution features within members and contact pressure distribution contour are revealed for single and double-bolted joint. Finally, the finite element models are adopted to investigate the effects of the clamping length, preload, material properties, hole clearance, and bolt size on contact pressure distribution in single-bolted joints. The coupling effect of contact pressure distribution in double-bolted joints under different preloads and geometric parameters are also examined.

Electronics-Free Soft Robotic Knee Brace for Dynamic Unloading During Gait for Knee Osteoarthritis: A Proof-of-Concept Study

Abstract We present a novel electronics-free soft robotic knee brace which employs a closed-loop fluidic regenerative (CLFR) system for dynamic unloading in unicompartmental tibiofemoral osteoarthritis (OA). The existing dynamic unloaders are bulky, large, and heavy, and have low compliance likely due to the use of an electrical control box, which is eliminated in the CLFR system. The system consists of a commercial unloading knee brace, a spring-loaded bellow inserted under the heel inside a shoe, a soft-fluidic actuator (bladder), and tubing for fluid transfer. The novelty lies in the fact that the user's body weight (self-powered) compresses the bellow to provide energy to inflate the air bladder placed at the knee. As a result, the yielded pressure unloads the undesirable forces due to knee OA during the stance phase of gait while strategically applying no forces during the swing phase. The knee bladder contact pressure/force, the system response time, and the durability were evaluated via contact pressure measurements for six systems with varying bellow volumes and either pneumatic or hydraulic configurations. All systems produced safe pressure outputs for human skin within a tested bodyweight range of 60–90 kg. Pneumatic and hydraulic systems achieved 250 ms and 400 ms pressurization response times, respectively. During cyclic loading, pneumatic and hydraulic systems demonstrated less than 1% and ∼10% pressure loss, respectively. Overall, the CLFR system created a promising electronics-free solution for dynamically unloading the knee during gait, indicating a potential new paradigm for knee braces.

Flexible Tactile Sensors Using AlN and MOSFETs Based Ultra-Thin Chips

This paper presents ultrathin chips (UTCs) based flexible tactile sensing system for dynamic contact pressure measurement. The device comprises of an AlN piezocapacitor based UTCs tightly coupled with another UTCs having metal-oxide-semiconductor field-effect transistors (MOSFETs). In this arrangement the AlN piezocapacitor forms the extended gate of MOSFETs. Both AlN piezocapacitor and MOSFET based UTCs are obtained by post-process reduction of wafer thicknesses to ~35μm using backside lapping. The performances of both UTCs were evaluated both before and after thinning and there was no noticeable performance degradation. The UTC-based AlN piezocapacitor exhibited six times higher sensitivity (43.79mV/N) than the thin filmbased AlN sensors. When coupled with MOSFETs based UTC, the observed sensitivity was 0.43N-1. The excellent performance, flexible form factor and compactness shows the potential of presented device in applications such minimal invasive surgical instruments where high-resolution tactile feedback is much needed.

Wireless Human Motion Detection with a Highly Sensitive Wearable Pressure Sensing Technology

AbstractWireless flexible sensing devices using inductive‐capacitive (LC) resonator‐enabled transmission technologies are attractive in the areas of human motion detection, health inspection, and implantable medical devices. However, challenges remain in LC‐based wireless sensing devices, including low device sensitivity/resolution and slow signal readout speed based on sweeping excitation frequencies. Herein, an LC resonator‐based wireless pressure sensing technology (LC‐WPS) is proposed for flexible contact pressure measurements in a real‐time manner. It includes a fully flexible passive LC pressure sensor and a signal‐reading circuit for wireless communication with the sensor and real‐time data processing. The passive sensor detects external pressure by the changes in resonant frequency. Importantly, by optimizing the design of the LC resonator in the sensor, the LC‐WPS converts the pressure‐dependent resonant frequency into circuit output voltage to a great extent, achieving a high sensitivity (1.23 × 10−2 kPa−1) and resolution (54 Pa) within a pressure range of 0–15 kPa. In addition, the LC‐WPS utilizes a single operating frequency (i.e., 13.56 MHz) instead of sweeping the operating frequencies to identify the sensor resonant frequency, featuring fast and real‐time data analysis and processing. Real‐time monitoring of human motions, such as laryngeal movement, neck bending and wrist rotation, is demonstrated, verifying the applicability of the LC‐WPS in the fields of wearable medical care and sports biomechanics.

ERGOBOSS: Ergonomic Optimization of Body-Supporting Surfaces.

Humans routinely sit or lean against supporting surfaces and it is important to shape these surfaces to be comfortable and ergonomic. We give a method to design the geometric shape of rigid supporting surfaces to maximize the ergonomics of physically based contact between the surface and a deformable human. We model the soft deformable human using a layer of FEM deformable tissue surrounding a rigid core, with measured realistic elastic material properties, and large-deformation nonlinear analysis. We define a novel cost function to measure the ergonomics of contact between the human and the supporting surface. We give a stable and computationally efficient contact model that is differentiable with respect to the supporting surface shape. This makes it possible to optimize our ergonomic cost function using gradient-based optimizers. Our optimizer produces supporting surfaces superior to prior work on ergonomic shape design. Our examples include furniture, apparel and tools. We also validate our results by scanning a real human subject's foot and optimizing a shoe sole shape to maximize foot contact ergonomics. We 3D-print the optimized shoe sole, measure contact pressure using pressure sensors, and demonstrate that the real unoptimized and optimized pressure distributions qualitatively match those predicted by our simulation.

A framework for effective face-mask contact modeling based on finite element analysis for custom design of a facial mask.

A novel contact model is presented to efficiently solve a face-mask contact problem by using the finite element (FE) method for the optimized design of a custom facial mask. Simulation of contact pressure for various mask designs considering material properties of the face allows virtual evaluation of the suitability of a mask design for a person's face without conducting empirical measurement of the face-mask contact pressure. The proposed contact model is accomplished by combining three approaches to reduce the calculation cost of simulating the face-mask contact: (1) use of a simplified and modifiable mask model that applies a spline curve to design points; (2) reduction of the FE model of the face by applying static condensation; and (3) application of a contact assumption that uses the Lagrange multiplier method. A numerical case study of a medical mask design showed that the proposed model could calculate the face-mask contact pressure efficiently (0.0448 sec per design). In a pilot usability experiment, the measured contact pressure was found similar values (range of mean contact pressure: 0.0093 ~ 0.0150 MPa) to the estimated values (range of mean contact pressure: 0.0097 ~ 0.0116 MPa).

Finite Element Modeling of Planus and Rectus Foot Types for the Study of First Metatarsophalangeal and First Metatarsocuneiform Joint Contact Mechanics.

The foot is a highly complex biomechanical system for which finite element (FE) modeling has been used to evaluate its loading environment. However, there is limited knowledge of first metatarsophalangeal (MTP) and first metatarsocuneiform (MTC) joint contact mechanics. Our goal was to develop a framework for FE modeling of the medial forefoot which could accurately predict experimental measurements of first MTP and first MTC joint loading. Simulations of planus and rectus foot types were conducted for midstance of gait. A custom-built force-controlled cadaveric test-rig was used to derive intracapsular pressure sensor measurements of contact pressure, force, and area during quasi-static loading. The FE model was driven under the same boundary and loading conditions as the cadaver. Mesh sensitivity analyses and best-fit calibrations of moduli for first MTP and first MTC joint cartilage were performed. Consistent with previous experimental research, a lower compressive modulus was best-fit to the first MTP compared to first MTC joint at 10 MPa and 20 MPa, respectively. Mean errors in contact pressures, forces, and areas were 24%, 4%, and 40% at the first MTP joint and 23%, 12%, and 19% at the first MTC joint, respectively. The present developmental framework may provide a basis for future modeling of first MTP and first MTC joint contact mechanics. This study acts as a precursor to validation of realistic physiological loading across gait to investigate joint loading, foot type biomechanics, and surgical interventions of the medial forefoot.

Fabricated leg mannequin for the pressure measurement of compression stockings

Different lower limbs and devices used for the contact pressure measurement of the compression stocking make a significant difference to the precise contact pressure value. This study aimed to fabricate a novel soft leg mannequin based on the standard-sized wooden leg mannequin, but closer to the human leg with soft tissue and bones and to evaluate further the performance of the fabricated leg mannequin. The contact pressure exerted by the graduated compression stocking was measured by the fabricated leg mannequin at four different locations along six different cross-sections. Comparing the contact pressure measured by the fabricated leg mannequin, the standard-sized wooden leg mannequin and human legs, the fabricated leg mannequin has a similar pattern to human legs, and contact pressure exerted by the wooden leg mannequin was far higher than that of human legs. In addition, the local contact pressure measured by the fabricated leg mannequin also has a remarkable agreement with that of human legs. Moreover, there was a significant Spearman rank correlation between the contact pressure measured by the fabricated leg mannequin and the human leg. Therefore, the performance of the fabricated leg mannequin can be consistent with the human leg, which enables the fabricated leg mannequin to replace the standard-sized wooden leg mannequin for standard tests.

Research on the Electric Life Prediction of Relay Contact Based on Harris Hawk Optimized

The failure of ac relay contacts will cause electrical control system fault, which will bring certain economic losses. Therefore, accurate prediction and evaluation of the electrical life of the relay have certain research value and practical significance. The measurement of the contact resistance of the relay was performed using a self-designed experimental platform. An electrical life prediction method of ac relay was proposed. First, the measured contact resistance signal was decomposed using empirical mode decomposition (EMD), and several sub-sequence components and residual components were obtained. Second, prediction of these components was conducted using a long short-term memory neural network (LSTM), and the prediction value was reconstructed. Third, the group method of data handling (GMDH) algorithm and Harris Hawk optimization (HHO) algorithm were used to optimize LSTM. Finally, contact pressure was calculated using the predicted contact resistance. The electrical life of the relay was predicted according to a contact-pressure-based electrical life criterion. Compared with other models, the prediction accuracy of the contact resistance is higher. The electrical life of the relay can be predicted effectively using the prediction results of both contact resistance and contact pressure. In practical application, a pressure sensor can be installed in the relay, and the electrical life of the contact can be predicted by the measured contact pressure.

Realization of Imitation Behavior by Robot Legs Using a Device for Measuring Contact Pressure Distribution at the Outer Edge of the Human Foot

Realization of Imitation Behavior by Robot Legs Using a Device for Measuring Contact Pressure Distribution at the Outer Edge of the Human Foot

Contact Pressure Reduction in the Anterior Ankle During Placement of Short Leg Splints

Category:Trauma; AnkleIntroduction/Purpose:Lower extremity splints are commonly used in orthopaedic care throughout emergency departments, operating rooms, and outpatient clinics. Although the mainstay of ankle immobilization, they have been associated with ulcers due to high contact pressures over bony prominences and the anterior ankle. High contact pressures may occur in the anterior ankle when splint padding is applied while the ankle is in a plantarflexed position and subsequently dorsiflexed as the plaster or fiberglass hardens. The purpose of this study is to measure contact pressures in the anterior ankle when cast padding is applied in a plantarflexed position and subsequently dorsiflexed. We hypothesized, that the removal of padding over the anterior ankle following dorsiflexion would result in reduced anterior ankle contact pressures.Methods:Short leg posterior U-splints were applied to the right lower extremity in two healthy volunteers with an underlying pressure transducer [Tekscan I-Scan system (Tekscan Inc, South Boston, MA, USA)] on the skin surface centered over the tibialis anterior tendon. Anterior ankle surface pressures were measured when the padding was applied in maximum plantar flexion and dorsiflexed to neutral position as measured by a goniometer. This was then repeated in the same subjects but prior to dorsiflexion, a 3cm x 3cm square of padding was removed over the pressure transducer prior to dorsiflexion. Percent change from initial contact pressure centered on the tibialis anterior with either Webril (Covidien/Medtronic, Dublin, Ireland), or Specialist Cotton Blend Cast Padding (BSN Medical, Charlotte, NC, USA) was calculated.Results:There were 2 limbs analyzed for presentation of this pilot data. The percent change in anterior ankle contact pressure when padding was applied in plantar flexion and then placed in neutral was an average increase of 264% with just padding and 238% with padding and plaster. [TP1] Subsequently, the removal of padding from the anterior ankle resulted in an average decrease of 126% of[TP2] the increased pressure relative to baseline measurements (Figure 1). The reduction in contact force with the removal of Webril was greater than Specialist.Conclusion:In this pilot data, we report increases in anterior ankle contact pressures when splint padding is applied in plantar flexion and re-positioned into neutral. However, removal of anterior ankle padding reduces pressure over the anterior ankle and may reduce the risk of iatrogenic splint related ulcers in this area. Additionally, this technique may elicit varying reductions in anterior ankle pressure depending on the type of cast padding utilized. This data, though preliminary, underscores the importance of avoiding excess padding over the anterior ankle during splint application.

Influence of Menisci on Tibiofemoral Contact Mechanics in Human Knees: A Systematic Review.

Purpose: Menisci transfer axial loads, while increasing the load-bearing tibiofemoral contact area and decreasing tibiofemoral contact pressure (CP). Numerous clinical and experimental studies agree that an increased CP is one predominant indicator for post-traumatic osteoarthritis (PTOA) of the knee joint. However, due to the immense variability in experimental test setups and wide range of treatment possibilities in meniscus surgery, it is difficult to objectively assess their impact on the CP determination, which is clearly crucial for knee joint health. Therefore, the aim of this systematic review is to investigate the influence of different meniscal injuries and their associated surgical treatments on the CP. Secondly, the influence of different test setups on CP measurements is assessed. On the basis of these results, we established the basis for recommendations for future investigations with the aim to determine CPs under different meniscal states. Methods: This review was conducted in accordance with the PRISMA guidelines. Studies were identified through a systematic literature search in Cochrane, PubMed and Web of Science databases. Literature was searched through pre-defined keywords and medical subject headings. Results: This review indicates a significant increase of up to 235% in peak CP when comparing healthy joints and intact menisci with impaired knee joints, injured or resected menisci. In addition, different test setups were indicated to have major influences on CP: The variety of test setups ranged from standard material testing machines, including customized setups via horizontal and vertical knee joint simulators, through to robotic systems. Differences in applied axial knee joint loads ranged from 0 N up to 2,700 N and resulted unsurprisingly in significantly different peak CPs of between 0.1 and 12.06 MPa. Conclusion: It was shown that untreated traumatic meniscal tears result in an increased CP. Surgical repair intervention were able to restore the CP comparable to the healthy, native condition. Test setup differences and particularly axial joint loading variability also led to major CP differences. In conclusion, when focusing on CP measurements in the knee joint, transparent and traceable in vitro testing conditions are essential to allow researchers to make a direct comparison between future biomechanical investigations.

Intra-tracheal multiplexed sensing of contact pressure and perfusion.

Incorrect endotracheal tube (ETT) cuff inflation pressure causes significant problems for intubated patients. The technical development and first in vivo use of a smart ETT for measurements at the cuff-trachea interface during mechanical ventilation are described. The intra-tracheal multiplexed sensing (iTraXS) ETT contains integrated optical fibre sensors to measure contact pressure and blood perfusion. The device is tested during mechanical ventilation in a porcine model (N=6). For contact pressure, signals were obtained in all 30 measurements. For perfusion, data could be obtained in all 33 measurements. In the 3 cases where the cuff was inflated to an artificially high-level, blood occlusion is observed.

Arthroscopic single anchor repair techniques for upper third subscapularis tears provide sufficient biomechanical stability.

Upper third tears of the subscapularis tendon can be repaired successfully with a single anchor according to previous literature. The aim of the present study was to compare three single anchor repair techniques regarding fixation strength, footprint coverage and contact pressure in a biomechanical test set-up on human cadaveric shoulders. Eighteen human cadaveric shoulders were randomized in three groups with respect to the repair technique; group 1: knotted lasso-loop mattress, group 2: knotted mattress and group 3: knotless tape repair. Upper third tears of the subscapularis tendon (Lafosse type 2) were created and repairs were performed with additional contact pressure and area measurement using a pressure mapping system. Cyclic testing was performed by loading the subscapularis from 10 to 100N for 300 cycles. A position-controlled ramp protocol up to 30 and 50N was used to allow for pressure measurements. Finally, specimens were loaded to failure and failure modes were recorded. The three groups were not significantly different regarding age, gender, bone mineral density at the lesser tuberosity, subscapularis footprint size and defect area created at the upper subscapularis insertion. A significant difference was detected between group 1 (48.6 ± 13.8%) and group 2 (25.9 ± 5.7%) regarding pressurized footprint coverage (p = 0.028). Ultimate load to failure was 630.8 ± 145.3N in group 1, 586.9 ± 220.7N in group 2 and 678.2 ± 236.5N in group 3, respectively. Cyclic displacement was similar in all three groups with an average displacement of 1.2 ± 0.6mm. The highest stiffness was found in group 1 with 88 ± 30.3, which was not statistically significantly different to group 2 (65 ± 27N/mm) and group 3 (83.9 ± 32.9N/mm). The most common mode of failure was suture cut-through at the suture-tendon interface (44%). Failures in group 3 were less common associated with suture cut-through (33% vs. 50% in group 1 and 2), but no significant differences were found. All three tested single anchor repair techniques of upper third subscapularis tears were able to provide sufficient biomechanical stability. Knotted lasso-loop mattress and knotless tape repair were superior regarding pressurized footprint coverage compared to a knotted horizontal mattress technique and are, therefore, preferable techniques for upper subscapularis repair.