Validation of a newly developed low-cost, high-accuracy, camera-based gait analysis system.

BACKGROUND: Gait analysis is essential for evaluating locomotor function and fall risk, particularly in the elderly and in various musculoskeletal disorders. Traditional gait analysis systems face challenges such as technical difficulties, high cost, and complexity of use. Therefore, there is a need for a more accessible and cost-effective system with a wider clinical applicability. RESEARCH QUESTION: This study aimed to validate the newly developed IB-gait® system (InBody, Republic of Korea), a camera-based gait analysis tool, by comparing it against the VICON system. METHODS: A total of 28 community-dwelling adults without gait abnormalities (mean age 24.9 years) were enrolled in this study. The participants underwent gait analysis at their self-selected speed using VICON and IB-gait® simultaneously. Nine spatiotemporal gait parameters, including stride length (m), step length (m), stride duration (s), double-limb duration (s), stance phase (s), swing phase (s), cadence (velocity × 120/stride length), and gait velocity (m/s) were measured. The agreement between the two systems was tested using Bland-Altman plots and intraclass correlation coefficients (ICC). RESULTS: The IB-gait® showed a high degree of agreement with the VICON system in most gait parameters. The ICC showed excellent reliability for stride length (0.97), step length (0.92), gait velocity (0.97), cadence (0.97), and stride duration (0.79). However, it showed lower reliability in time-based parameters, including double-limb duration (0.12), stance phase (0.54), swing phase (0.241), and stance/swing phase ratio (0.11). SIGNIFICANCE: The IB-gait® system appears to be a feasible and cost-effective alternative to VICON system for gait analysis, particularly showing a high level of agreement in the distance-based parameters. Its practicality in clinical settings makes it a valuable tool for widespread use in gait analysis. However, further refinement of time-based parameter measurements and validation in diverse patient populations are needed to enhance its applicability.

Investigating the Mechanisms of Intradermal Injection for Easier "Skin Booster" Treatment: A Fluid Mechanics Approach to Determine Optimal Delivery Method.

Background: The use of "skin boosters" for rejuvenating aged skin is widely used. However, the accurate injection of the skin booster into the dermal layer remains a challenge due to the density of the dermis. The purpose of this study was to investigate the optimal mechanical variables of delivery that enabled correct targeting of the product to the dermis for optimal results. Methods: We investigated the impact of mechanical variables (syringe diameter, needle diameter and length, and viscosity of the skin booster) on the force required for intradermal injection in porcine skin. The correlation between these variables and the injection force was examined as well. Results: The results show that smaller syringe diameters, larger needle diameters, shorter needle lengths, and lower viscosity of the skin boosters reduce the injection force needed for intradermal injections. Conclusions: During the administration of skin booster injections, clinicians should take into account optimal conditions that facilitate intradermal injections, thus maximizing rejuvenating outcomes. Furthermore, manufacturers of skin boosters should formulate the products with decreased viscosity and provide the product in conjunction with appropriate needles and syringes, designed to optimize ease of injection.

A Pneumatically Controlled Prosthetic Socket for Transfemoral Amputees.

Amputees typically experience changes in residual limb volume in their daily lives. It causes an uncomfortable fit of the socket by applying high pressure on the sensitive area of the residual limb or by loosening the socket. In this study, we developed a transfemoral prosthetic socket for above-the-knee amputees that ensures a good socket fit by maintaining uniform and constant contact pressure despite volume changes in the residual limb. The socket has two air bladders in the posterior femoral region, and the pneumatic controller is located on the tibia of the prosthesis. The pneumatic system aims to minimize unstable fitting of the socket and improve walking performance by inflating or deflating the air bladder. The developed socket autonomously maintains the air pressure inside the prosthetic socket at a steady-state error of 3 mmHg or less by adjusting the amount of air in the air bladder via closed-loop control. In the clinical trial, amputee participants walked on flat and inclined surfaces. The displacement between the residual limb and socket during the gait cycle was reduced by up to 33.4% after air injection into the socket. The inflatable bladder increased the knee flexion angle on the affected side, resulting in increased stride length and gait velocity. The pneumatic socket provides a stable and comfortable walking experience not only when walking on flat ground but also on slopes.

Association of atypical femoral fracture location and lower limb mechanical axis: a computed tomography-based finite element analysis.

Atypical femoral fractures (AFFs) are categorized as low-energy fractures of the femoral shaft or subtrochanteric region. The use of computed tomography-based finite element analysis demonstrated that the femoral weakest point against tensile stress coincided with AFF location, which was determined by the lower limb axis and femoral bowing. INTRODUCTION: This study aimed to assess the relationship between the femoral weakest point against tensile stress and the lower limb axis and geometry, including femoral bowing, using a computed tomography (CT)-based finite element analysis (FEA) model. METHODS: We retrospectively reviewed 19 patients with AFFs and analyzed their CT images of the contralateral intact femur. We performed FEA to find the maximum principal stress (MPS) and maximal tensile stress loading area (femoral weakest point, FWP) of each patient and matched the FWP with the real location of AFF. We applied mechanical axes differently, as neutral, varus, and valgus, in the FEA model, when we analyzed the change in MPS and FWP based on lower limb alignment. We compared the degree of agreement between the real fracture location and FWP before and after knee mechanical axis adjustment. RESULTS: The average participant age was 75.9 (range, 61-87) years, and all participants were women. In the 19 patients included, we observed 20 and 7 shaft and subtrochanteric AFFs, respectively. The average mechanical axis at the knee joint level was 22.6 mm (range, 0-70 mm) of the varus. All the patients showed an increasing trend of MPS and a distal movement of FWP when the mechanical axis of the knee was applied from the valgus to varus alignment. The root mean square errors between the FWP and real fracture location were 14.58% and 10.87% before and after adjustment, respectively, implying that the degree of agreement was better in patients who underwent mechanical adjustment. CONCLUSION: The use of CT/FEA demonstrated that the FWP against tensile stress coincided with AFF location, which was determined by the lower limb axis and femoral bowing.

Comparison of hyaluronic acid filler ejection pressure with injection force for safe filler injection.

BACKGROUND: Owing to the increase in the number of medical procedures performed every year, the frequency of filler injection-related complications has also increased. Although slow, gentle injections with low pressure are usually considered to be safe, the differences in ejection pressure during a filler injection remain to be determined. This study aimed to identify the optimal pressure during filler injections and evaluate its capacity to overcome the arterial blood pressure and reflux the filler material. METHODS: Twelve combinations of four hyaluronic acid (HA) fillers with different rheological properties and three needles of different diameters were assessed to determine the force exerted by the injection model. The ejection forces corresponding to varying injection forces were measured and HA filler ejection pressures were calculated. RESULTS: The highest and lowest injection forces were achieved using 30- and 25-G needles, respectively. In accordance with the expected ejection force, high ejection pressure was achieved by administering the HA filler under a high injection force. Irrespective of the injection force, the ejection pressure was likely to be higher than the vascular pressure at the time of entry into the vessel, rendering the injection dangerous. CONCLUSION: During filler injection, penetration of blood vessels and intravascular injection can be avoided by approaching the target area gently using a cannula or needle.

Optimal plate position in minimally invasive plate osteosynthesis for mid-shaft clavicle fractures: simulation using 3D-printed models of actual clinical cases.

INTRODUCTION: This study evaluated the optimal anatomical locking plate position using three-dimensional printed models of the clavicle. MATERIALS AND METHODS: Three-dimensional models of the fractured clavicle were reproduced from seventeen patients who underwent minimally invasive plate osteosynthesis (MIPO) procedures. The fracture location-the percentage of the distal fragment length compared to the entire clavicle-ranged from 30-44%. We evaluated four commercially available plate systems for position and fitting with the bone. After reducing the fracture on each three-dimensional model, we determined the optimal plate and its position. RESULTS: The anatomical plate fitted well when positioned in the middle of the clavicle for a fracture location ranging from 40 to 60%. When the fracture location was 30-40%, the anatomical plate fit well onto the bone model only in 36% of clavicles; otherwise, the reversed position of the anatomical plate or the lateral plate fit well. The anatomical plate was found to be unsuitable when the fracture location was less than 30%; in this case, the lateral plate was the best fit. CONCLUSION: Fitting the anatomical plate in MIPO for clavicle fractures depends on the fracture location. This can help surgeons determine the optimal plate for clavicle MIPO.

Active Body Pressure Relief System with Time-of-Flight Optical Pressure Sensors for Pressure Ulcer Prevention.

A body pressure relief system was newly developed with optical pressure sensors for pressure ulcer prevention. Unlike a conventional alternating pressure air mattress (APAM), this system automatically regulates air flow into a body supporting mattress with adaptive inflation (or deflation) duration in response to the pressure level in order to reduce skin stress due to prolonged high pressures. The system continuously quantifies the body pressure distribution using time-of-flight (ToF) optical sensors. The proposed pressure sensor, a ToF optical sensor in the air-filled cell, measures changes in surface height of mattress when pressed under body weight, thereby indirectly indicating the interface pressure. Non-contact measurement of optical sensor usually improves the durability and repeatability of the system. The pressure sensor was successfully identified the 4 different-predefined postures, and quantitatively measured the body pressure distribution of them. Duty cycle of switches in solenoid valves was adjusted to 0-50% for pressure relief, which shows that the interface pressure was lower than 32 mmHg for pressure ulcer prevention.

Clinical experience with three-dimensional printing techniques in orthopedic trauma.

BACKGROUND: To report our experiences with the use of three-dimensional (3D) printing in the field of orthopedic trauma. METHODS: This retrospective study enrolled 24 patients from three university teaching hospitals in whom 3D printing technique was applied: 14 patients with acetabular fractures and 10 patients with clavicular shaft fractures. We summarized our experiences with 3D printed bone models. RESULTS: Three-dimensional printed acetabular models improved understanding of complex acetabular anatomy and fracture pattern to plan the optimal positioning of a reduction clamp and the trajectory of screws. Pre-bending of a reconstruction plate could reduce operative time. We also recorded fluoroscopic images of a simulated surgery for percutaneous screw fixation of the acetabular posterior column, with the optimal positioning of the guide wire determined during the simulation used as a reference during the actual operation. This surgical simulation was performed by a resident and served as a helpful training method. For fractures of the clavicle, we identified the optimal position of anatomical plates using 3D printed clavicle models. CONCLUSION: In our experience, 3D printing technique provided surgeons with improved understanding of the fracture pattern and anatomy and was effectively used for preoperative planning, education of surgical trainees, and performing simulations to improve intra-operative technical outcomes.

Spiral shape microfluidic channel for selective isolating of heterogenic circulating tumor cells.

Detecting heterogenic tumor cells that are traveling in our body through blood stream for the tumor metastasis is one way for cancer prognosis. Due to the heterogeneity of circulating tumor cells (CTCs), further identification of tumor cell types should be accompanied with CTCs isolation from blood cells in peripheral blood sample. Both negative enrichment and recollection of isolated CTCs are required in the downstream analysis, which are time-consuming, labor-intensive, and massive equipment required. To solve these limitations, we have developed a simple and disposable spiral shape microfluidic channel that can separate all CTCs from blood cells, and at the same time, can identify the types of CTCs based on epithelial cell adhesion molecule (EpCAM) expression level. Two different types of tumor cells, MCF-7 and MDA-MB-231, both from the same origin of breast carcinoma cells, were used to demonstrate the functionality of the developed system. The spiral channel system could capture the EpCAM positive and negative CTCs with 96.3% and 81.2% purity, respectively, while both EpCAM positive and negative CTCs were differently positioned along the microfluidic channel. The average selectivity of EpCAM positive and negative CTCs is 6.1:4.8. In addition, the throughput of the system was optimized at a sample flow rate of 150µl/min. The developed system successfully demonstrated its potential to identify biomarkers, including EpCAM, for detecting the heterogenic CTCs.

Computational analysis of the safe zone for the antegrade lag screw in posterior column fixation with the anterior approach in acetabular fracture: A cadaveric study.

OBJECTIVE: The fluoroscopically-guided procedure of antegrade posterior lag screw in posterior column fixation through anterior approach is technique-dependent and requires an experienced surgeon. The purpose of this study was to establish the safe zone for the antegrade posterior lag screw by using computational analysis. METHOD: The virtual three-dimensional model of 178 hemi-pelvises was created from the CT data (DICOM format) by using Mimics® program, and were used to measure the safe zone of antegrade lag screw fixation on the inner table of the iliac wing, and the largest diameter of cylindrical implant inside safe zone. The central point (point A) of the cylinder was assessed and was compared with the intersection point (point B) between the linea terminalis and the anterior border of the sacroiliac articulation. RESULTS: The safe zone was triangular with an average area of 670.4mm2 (range, 374.8-1084.5mm2). The largest diameter of the cylinder was a mean 7.4mm (range, 5.0-10.0mm). When height was under 156.3cm, the diameter of the cylindrical implant was smaller than 7.0mm (p<0.001, regression coefficient=0.09). The linear distance between points A and B was 32.5mm (range, 19.2-49.3mm). Point A was far enough away from the well-positioned anterior column plate to prevent collision between the two. CONCLUSION: The safe zone was shaped like a triangle, and was large enough for multiple screws. Considering the straight-line distance between points A and B, the central screw can be fixed without overlapping with the well-positioned anterior column plate at the point between holes 2 and 3.

Surgical tips of intramedullary nailing in severely bowed femurs in atypical femur fractures: Simulation with 3D printed model.

INTRODUCTION: The surgical management of atypical femoral fractures (AFFs) is complex in cases with severe bowing of the femur, being associated with a high rate of failure. Our first aim was to use preoperative templating and 3D printed model characterise the technical difficulties associated with use of current commercially available intramedullary nail (IMN) systems for the management of AFFs with severe bowing. Our second aim was to use outcomes of our 3D printing analysis to define technical criteria to overcome these problems. MATERIAL AND METHODS: The modelled femur with 3D printing had an anterior bowing curvature radius of 772mm and an angle of lateral bowing of 15.4°. Nine commercially available IMN systems were evaluated in terms of position of the nail within the medullary canal, occurrence of perforation of femoral cortex by the distal tip of the nail, and location of the site of perforation relative to the knee joint. The following IMN systems were evaluated: unreamed femoral nail (UFN), cannulated femoral nail (CFN), Sirus nail, right and left expert Asian femoral nail (A2FN), right and left Zimmer Natural Nail (ZNN), proximal femoral nail anti-rotation (PFNA), and Zimmer Cephalomedullary Nail (CMN). RESULTS: Along the sagittal plane, the UFN, CFN and Sirus systems were acceptably contained within the medullary canal, as well as the "opposite side" A2FN and ZNN. Only the Sirus IMN system was contained along the coronal plane. The distal part of the all other IMN systems perforated the anterior cortex of the femur, at distances ranging between 2.8 and 11.7cm above the distal end of the femoral condyles. Using simulated fracture reduction in the 3D printed model, none of the 9 IMN systems provided acceptable anatomical reduction of the fracture. A residual gap in fragment position and translation was provided by the "opposite side" ZNN, followed by the UFN and Sirus systems. CONCLUSION: Commercially available IMN systems showed mismatch with severely bowed femurs. Our simulation supports that fit of these systems can be improved using an IMN system with a small radius of curvature and diameter, and by applying specific operative procedures.