Biomechanical Loading Research Articles

Ergonomic considerations when slotting piece-pick operations in distribution centers

Many warehouse slotting algorithms have overlooked worker ergonomics. This research aimed to develop ergonomics slotting guidelines based upon the back and shoulder postures and electromyographic (EMG) responses of the deltoid and erector spinae muscles when individual items are picked from, or full cases replenished to, different shelf heights In the first study of two studies, participants lifted small items representative of piece-pick tasks from seven shelf heights. In the second study, participants performed a simulated full case replenishment task in which they lifted boxes weighing between 2.7 and 10.9 kg from a cart into a flow rack. Shelf height significantly affected all postural and EMG variables and there was a trade-off between back and shoulder muscle activity across the varying shelf heights. Together, these studies were used to develop some general ergonomic slotting guidelines that could be implemented to reduce biomechanical load exposures experienced by distribution center workers.

Exploring the relationship between pain intensity and knee moments in participants with medial knee osteoarthritis: a cross-sectional study

BackgroundHigh biomechanical loading is believed to be a risk factor to pain in people with knee osteoarthritis (OA), but controversial findings have been reported on the relationship between external knee adduction moment (KAM) and pain. A more comprehensive analysis considering other factor such as external knee flexion moment (KFM) could help better reveal this relationship. This study explored the relationship between external knee adduction moment and pain intensity in participants with knee osteoarthritis (OA) using an integrated path analysis model.MethodsThis was a cross-sectional study based on laboratory setting. Forty-seven participants with clinical and radiographic medial knee OA were analyzed for their external knee adduction moment (KAM) and knee flexion moment (KFM) during walking using a motion analysis system. Pain intensity was measured by visual analogue scale (VAS) and the pain subscale of the Knee Injury and Osteoarthritis Outcome Score. Varus/valgus alignment was captured and quantified using a bi-planar X-ray system. Using a path analysis model, the relationships between pain intensity, KAM, KFM, OA radiographic severity, knee varus angle and walking speed were examined.ResultsThe proposed path model met the goodness-of-fit criteria. Based on this model, KAM had a negative effect on VAS pain indirectly through the mediation of KFM. The model indicated KAM and KFM were negatively related to one another; and KFM was positively related to VAS. The KAM index, defined as (KAM/ (KAM + KFM)), was negatively related to VAS.ConclusionsPath analysis enabled the construction of a more integrated pathokinematic framework for people with knee OA. The KAM index which reflected the load sharing on the frontal and sagittal planes also revealed its relationship with pain. Re-distribution of mechanical loading from frontal to sagittal plane might be a strategy for pain avoidance associated with mechanical irritation.

122. Does vertebral body tethering cause disc and facet joint degeneration? An MRI study with minimum two years of follow-up

<h3>BACKGROUND CONTEXT</h3> Disc health after various growth modulation techniques have been assessed in animal models, and tethering was claimed to prevent degeneration due to its less rigid nature compared to other growth-friendly techniques. Yet, the results of animal studies wherein tethering is applied on healthy spines to create a deformity cannot be extrapolated to humans, in which tethering is used for deformity correction. As biomechanical properties are different, effects of vertebral body tethering (VBT) surgery on discs and facet joints in clinical series are not precisely acknowledged. There are concerns that VBT surgery may cause degeneration at both intermediate and adjacent levels. <h3>PURPOSE</h3> Our aim was to investigate the integrity of discs and facet joints that are subject to compressive forces and relative stabilization during growth modulation. <h3>STUDY DESIGN/SETTING</h3> Retrospective analysis of a prospectively collected data. <h3>PATIENT SAMPLE</h3> This study included 25 (23F, 2M) consecutive adolescent idiopathic scoliosis (AIS) patients with a mean follow-up of 29 (24-62) months who underwent thoracoscopic VBT surgery between 2014 to 2017 were included. <h3>OUTCOME MEASURES</h3> Disc and facet joint degeneration scores on MRI. <h3>Methods</h3> Demographic, perioperative and radiographic data were collected. Overcorrection, mechanical and pulmonary complications, and reoperations were recorded. MRIs taken before surgery and at a minimum of 2 years of follow-up were evaluated for degeneration at the intermediate and adjacent segment intervertebral discs and facet joints by a blinded senior radiologist and compared. Discs were assessed using Pfirrmann grade. Facet joint degeneration was graded on a scale of 0-3. Changes from preop to follow-up MRIs were analyzed using McNemar's Test and Related Samples Marginal Homogeneity Test. <h3>Results</h3> The mean age at surgery was 12.2 (10–14) years and median Sanders stage was 3 (1-7). A mean of 7.7±1.1 (6-11) levels were tethered. Preoperative mean height of 155.3 (130-178) cm was increased to 163.4 (149-187) cm at latest follow-up. The mean preoperative MT curve magnitude of 46°±7.7° was corrected to 23.3°±5.9° at first erect, which was modulated to 12°±11.5° during follow-up. There was 1 (4%) broken tether, 5 (20%) overcorrected curves, 3 (12%) implant-related complications and 1 (4%) reoperation for a thoracoscopic tether release before the follow-up MRI was obtained. A total of 217 levels of discs and bilateral facet joints, were evaluated in the preoperative and follow-up MRI images. Analyses of disc and facet joint scores revealed no significant differences between patients. One case (4%) with an increase in disc scores already had multilevel moderate degeneration preoperatively, while another case (4%) displayed a single-level new-onset grade-2 bilateral facet degeneration. <h3>Conclusions</h3> This study reports MRI findings of 25 rapid and steady growing adolescents (Sanders 2-7) who had undergone thoracoscopic VBT surgery. At an average of 29 months (24-62) after growth modulation with VBT surgery, radiographic degenerative findings were not present in 97.7% of the intermediate and adjacent discs and 99.3% of the facet joints. Studies with longer follow-up are warranted to further analyze the effects of relative stabilization and altered biomechanical loads. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Effects of real-time feedback during decline walking on kinematic and kinetic gait parameters in a healthy population: study protocol for a randomized trial\xa0\u2014\xa0up and down

BackgroundThe control of the dynamic functional leg alignment (dFLA) and biomechanical load are important joint-related aspects regarding the development of osteoarthritis (OA). Research on level walking with feedback on load-related parameters has provided innovative treatment possibilities. With regard to walking on sloped surfaces, fundamental biomechanical knowledge exists. However, comprehensive data on the agreement of kinematics and kinetics of self-paced ramp versus sloped treadmill walking is lacking. Further, deeper insights into the control of the dFLA during decline walking and the usefulness of real-time feedback are missing.Methods/designThirty healthy participants aged between 18 and 35 years will be included. They will complete a three-dimensional gait analysis walking self-paced up and down on a 5-m ramp with a 10° inclination. Subsequently, speed-matched to ramp-up walking and self-paced 10° incline split-belt treadmill walking will be assessed. Afterwards, the participants will be observed under four different conditions of 10° declined walking on the same treadmill (a) self-paced walking, (b) self-paced walking with an internal focus of attention, (c) self-paced walking with real-time feedback, and (d) condition c speed-matched walking. The primary outcome parameter will be the frontal knee range of motion (fKROM). Secondary outcomes include the ground reaction force loading rate, spatial-temporal parameters, as well as sagittal, frontal and transversal kinematics, and kinetics for the lower extremities.DiscussionThe findings aim at improving the understanding of the effects of real-time feedback on the control of the dFLA and lower limb loading. Following clinical practicable methods for effective feedback devices can be developed and evaluated. Additionally, the first dataset comparing kinematic and kinetic parameters for decline and incline ramp walking versus walking on an instrumented treadmill will be available for appropriate intervention planning.Trial registrationClinicalTrials.govNCT04763850. Prospectively registered on 21 February 2021.

The Wearable Robotic Forearm: Design and Predictive Control of a Collaborative Supernumerary Robot

This article presents the design process of a supernumerary wearable robotic forearm (WRF), along with methods for stabilizing the robot’s end-effector using human motion prediction. The device acts as a lightweight “third arm” for the user, extending their reach during handovers and manipulation in close-range collaborative activities. It was developed iteratively, following a user-centered design process that included an online survey, contextual inquiry, and an in-person usability study. Simulations show that the WRF significantly enhances a wearer’s reachable workspace volume, while remaining within biomechanical ergonomic load limits during typical usage scenarios. While operating the device in such scenarios, the user introduces disturbances in its pose due to their body movements. We present two methods to overcome these disturbances: autoregressive (AR) time series and a recurrent neural network (RNN). These models were used for forecasting the wearer’s body movements to compensate for disturbances, with prediction horizons determined through linear system identification. The models were trained offline on a subset of the KIT Human Motion Database, and tested in five usage scenarios to keep the 3D pose of the WRF’s end-effector static. The addition of the predictive models reduced the end-effector position errors by up to 26% compared to direct feedback control.

Muscle Activation during Gait in Unilateral Transtibial Amputee Patients with Prosthesis: The Influence of the Insole Material Density.

Background: Walking is a complex process that is highly automated and efficient. This knowledge is essential for the study of pathological gait. The amputation of lower limbs involves new biomechanical load and gait patterns, and injuries due to overload or disuse may occur. The objective of this study is to assess muscle activation as part of the gait in unilateral transtibial amputee patients with prosthesis, at different speeds and with different plantar supports. Method: Included in the sample were 25 people with amputation and 25 control participants. Muscle activation was evaluated in both groups by means of surface electromyography (EMG) under normal and altered conditions. Results: Control participants did not show statistically significant differences (p ˃ 0.05) between their muscle groups, irrespective of support and speed. However, people with amputation did show differences in muscle activity in the quadriceps, all of which occurred at the highest speeds, irrespective of support. In the analysis between groups, significant differences (p < 0.05) were obtained between the leg of the amputee patient and the leg of the control participant, all of them in the quadriceps, and at speeds 3 and 4, regardless of the insole used. Conclusions: Participants with unilateral transtibial amputation carry out more quadriceps muscle activity during gait compared to the control group.

Evaluation of the HeroWear Apex back-assist exosuit during multiple brief tasks

Trunk exoskeletons are wearable devices that support humans during physically demanding tasks by reducing biomechanical loads on the back. While most trunk exoskeletons are rigid devices, more lightweight soft exoskeletons (exosuits) have recently been developed. One such exosuit is the HeroWear Apex, which achieved promising results in the developers’ own work but has not been independently evaluated. This paper thus presents an evaluation of the Apex with 20 adult participants during multiple brief tasks: standing up from a stool with a symmetric or asymmetric load, lifting a unilateral or bilateral load from the floor to waist level, lifting the same bilateral load with a 90-degree turn to the right, lowering a bilateral load from waist level to floor, and walking while carrying a bilateral load. The tasks were performed in an ABA-style protocol: first with exosuit assistance disengaged, then with it engaged, then disengaged again. Four measurement types were taken: electromyography (of the erector spinae, rectus abdominis, and middle trapezius), trunk kinematics, self-report ratings, and heart rate. The exosuit decreased the erector spinae electromyogram by about 15% during object lifting and lowering tasks; furthermore, participants found the exosuit mildly to moderately helpful. No adverse effects on other muscles or during non-lifting tasks were noted, and a decrease in middle trapezius electromyogram was observed for one task. This confirms that the HeroWear Apex could reduce muscle demand and fatigue. The results may transfer to other exoskeletons with similar design principles, and may inform researchers working with other wearable devices.

Біомеханічне моделювання та проблемні питання хірургічної корекції вродженої лійкоподібної деформації грудної клітки

Congenital funnel chest deformity (CFCD) is noted in 0.6–2.3% of the population and accounts for 90% of all congenital chest deformities. Nuss thoracoplasty is the most common method for treating CFCD, which is considered a minimally invasive technology and provides a quick cosmetic effect. Purpose is to search for models of CFCD and its surgical correction in order to create a technique that is as close to reality as possible, which will make it possible to optimally plan and rationally carry out the forthcoming operation. Analysis of literature sources showed that, on the one hand, the construction of simplified models of the chest allows quick research, but these simplifications do not allow for an objective assessment of the influence and interaction of various elements of the complex biomechanical system «sternum–rib–spine». On the other hand, complex models are more reliable, but hardly available for implementation due to their ultra-high manufacturability and cost. In addition, in studies of stress-strain state on models of the chest, the presence of the spinal column or the interaction of the ribs with the vertebrae has been insufficiently studied. When in the works on modeling road traffic injuries this is justified due to the support of the spine on the seat, then when modeling the correction of chest deformities, the lack of consideration of the mobility of the articular joints and the flexibility of the spinal column can lead to incorrect and false results. It is promising to create a technique for modeling CFCD and its surgical correction in conditions close to reality. This will make it possible to develop a rational modification of thoracoplasty based on the D. Nuss operation under the condition of one–stage full–fledged stable correction and minimal biomechanical loads in the «sternum-rib-spine» system. No conflicts of interest was declared by the authors. Key words: funnel chest deformity, thoracoplasty, biomechanics.

Ergonomic evaluation of ergonomically designed chalkboard erasers on shoulder and hand-arm muscle activity among college professors

Teaching professionals regularly use the chalk board eraser or duster throughout their life which leads to several unnoticed musculoskeletal disorders. The purpose of this study was to provide an alternate design for the existing Indian model chalk board eraser, because current eraser design causes noticeable amount of biomechanical load on the wrist, hand and shoulder region when its frequency of usage was high and repetitive. Initially, pilot study was conducted through an online modified Nordic questionnaire among 60 college professors to identify the risky regions of the body due to the use of existing chalk board eraser. This was followed by an experimental trial using surface Electromyography Sensors (sEMG) in which the muscle behaviour was evaluated during the chalkboard erasing process employing three newly designed dusters and a traditional duster. The results revealed that Model A designed with a large palm rest to align the palm and the forearm had better usability and the musculoskeletal distress was reduced when compared with the traditional duster. Whereas Model C designed with slip guards to improve the gripping forces was found to have better performance rating after Model A. Model B provided with separate handle was found to be the worst performer when compared with the conventional duster. Results suggested that providing an improved palm rest and slip guards such as grooves reduces the musculoskeletal distress.

Excessive mechanical stretch‑mediated osteoblasts promote the catabolism and apoptosis of chondrocytes via the Wnt/β‑catenin signaling pathway.

Excessive biomechanical loading is considered an important cause of osteoarthritis. Although the mechanical responses of chondrocytes and osteoblasts have been investigated, their communication during mechanical loading and the underlying molecular mechanisms are not yet fully known. The present study investigated the effects of excessive mechanically stretched osteoblasts on the metabolism and apoptosis of chondrocytes, and also assessed the involvement of the Wnt/β-catenin signaling pathway. In the present study, rat chondrocytes and osteoblasts were subjected to mechanical tensile strain, and an indirect chondrocyte-osteoblast co-culture model was established. Reverse transcription-quantitative PCR and western blotting were performed to determine the expression levels of genes and proteins of interest. An ELISA was performed to investigate the levels of cytokines, including matrix metalloproteinase (MMP) 13, MMP 3, interleukin-6 (IL-6) and prostaglandin E2 (PG E2), released from osteoblasts. Flow cytometry was performed to detect the apoptosis of chondrocytes exposed to stretched osteoblast conditioned culture medium. The levels of MMP 13, IL-6 and PG E2 increased significantly in the supernatants of stretched osteoblasts compared with the un-stretched group. By contrast, the mRNA expression levels of Collagen 1a and alkaline phosphatase were significantly decreased in osteoblasts subjected to mechanical stretch compared with the un-stretched group. The mRNA expression level of Collagen 2a was significantly decreased, whereas the expression levels of MMP 13 and a disintegrin and metalloproteinase with thrombospondin-like motifs 5 were significantly increased in chondrocytes subjected to mechanical stretch compared with the un-stretched group. In the co-culture model, the results indicated that excessive mechanically stretched osteoblasts induced the catabolism and apoptosis of chondrocytes, which was partly inhibited by Wnt inhibitor XAV-939. The results of the present study demonstrated that excessive mechanical stretch led to chondrocyte degradation and inhibited osteoblast osteogenic differentiation; furthermore, excessive mechanically stretched osteoblasts induced the catabolism and apoptosis of chondrocytes via the Wnt/β-catenin signaling pathway.

NEW ADVANCED METHODS IN SIDE CRASH TESTING

&#x0D; &#x0D; &#x0D; &#x0D; This work follows up the previous work [1] regarding the used methodology in the field of passive safety, ie. crash testing. The work is based on experience gained in the Active Lateral Impact Simulator (ALIS) project and describes complete process. The main focus has been given to the fine-tuning of the boundary conditions and loading of the system in order to ensure correct biomechanical loads.&#x0D; &#x0D; &#x0D; &#x0D;

Exploring the Interaction Between Head-Supported Mass, Posture, and Visual Stress on Neck Muscle Activation.

Assess neck muscle activity for varying interactions between helmet, posture, and visual stress in a simulated "helo-hunch" posture. Military aviators frequently report neck pain (NP). Risk factors for NP include head-supported mass, awkward postures, and mental workload. Interactions between these factors could induce constant low-level muscle activation during helicopter flight and better explain instances of NP. Interactions between physical loading (helmet doffed/donned), posture (symmetric/asymmetric), and visual stress (low/high contrast) were studied through neck muscle electromyography (EMG), head kinematics, subjective discomfort, perceived workload, and task performance. Subjects (n = 16) performed eight 30-min test conditions (varied physical loading, posture, and visual stress) while performing a simple task in a simulated "helo-hunch" seating environment. Conditions with a helmet donned had fewer EMG median frequency cycles (which infer motor unit rotation for rest/recovery, where more cycles are better) in the left cervical extensor and left sternocleidomastoid. Asymmetric posture (to the right) resulted in higher normalized EMG activity in the right cervical extensor and left sternocleidomastoid and resulted in less lateral bending compared with neutral across all conditions. Conditions with high visual stress also resulted in fewer EMG cycles in the right cervical extensor. A complex interaction exists between the physical load of the helmet, postural stress from awkward postures, and visual stress within a simulated "helo-hunch" seating environment. These results provide insight into how visual factors influence biomechanical loading. Such insights may assist future studies in designing short-term administrative controls and long-term engineering controls.

The Concurrent Validity, Test-Retest Reliability and Usability of a New Foot Temperature Monitoring System for Persons with Diabetes at High Risk of Foot Ulceration.

At-home foot temperature monitoring may be useful in the early recognition of imminent foot ulcers that occur through biomechanical loading in people with diabetes. We assessed the concurrent validity, test–retest reliability, and usability of a new plantar foot temperature monitoring device in 50 people with diabetes and peripheral neuropathy. We compared plantar foot temperature measurements with a platform system that consists of embedded temperature sensors with those from a handheld infrared thermometer that was used as a reference. Repeated platform assessments were compared for test–retest reliability. Usability was assessed in 15 participants who used both devices daily for two weeks at home, after which they completed a questionnaire. Agreement between devices was excellent for the metatarsal heads and heel (ICCs ≥ 0.98, LOA: −0.89 °C; 1.16 °C) and hallux and lateral midfoot (0.93 ≤ ICC ≤ 0.96, LOA: −2.87 °C; 2.2 °C), good for digits 2–5 (0.75 ≤ ICC ≤ 0.88, LOA: −5.04 °C; 2.76 °C), and poor for the medial midfoot (ICC = 0.19, LOA: −8.21 °C; −0.05 °C). Test–retest reliability was high (ICC = 0.99, LOA: −0.59 °C; 1.35 °C). Participants scored between 3.8 and 4.3 on a 5-point Likert scale for willingness to measure, ease of use, measurement comfort, and duration. In conclusion, the platform shows good concurrent validity in foot regions where most ulcers occur, good test–retest reliability, and good usability for measuring plantar foot temperature. Further research should assess the clinical validity of the platform to help prevent plantar diabetic foot ulcers.

Does vertebral body tethering cause disc and facet joint degeneration? A preliminary MRI study with minimum two years follow-up

BACKGROUND CONTEXTVertebral body tethering (VBT), a flexible compression-based growth modulation technique, was claimed to prevent disc degeneration due to its less rigid nature compared to other growth-friendly techniques. Yet, the consequences of VBT surgery on discs and facet joints have not been precisely acknowledged. PURPOSEThe purpose of this study was to determine the changes in the intermediate and adjacent levels at least 2 years after surgery. STUDY DESIGN/SETTINGProspectively-followed consecutive patient cohort PATIENT SAMPLEAdolescent idiopathic scoliosis patients who underwent thoracoscopic VBT between 2014 and 2017 were included. OUTCOME MEASURESDegeneration of the intervertebral discs using the Pfirrmann classification; Degeneration of facet joints using a scale of 0 to 3. METHODSDemographic, perioperative, clinical, radiographic data were collected. Skeletal maturity and height gain were assessed in every follow-up. Overcorrection, tether breakage, mechanical and pulmonary complications as well as readmission and reoperations were recorded. MRIs taken before surgery and at a minimum of 2 years follow-up were evaluated for degeneration at the intermediate and adjacent segment intervertebral discs and facet joints by a blinded senior radiologist and compared. RESULTSTwenty-five patients with a mean of 38.6±10.6 months (24–62) of follow-up were included. The mean age at surgery was 12.2 (10–14), and the median Sanders stage was 3 (1–7). A mean of 7.7±1.1 (6–11) levels were tethered. The mean preoperative main thoracic curve magnitude of 46°±7.7° was corrected to 23.3°±5.9° postoperatively, which was subsequently modulated to 12° ±11.5° during the follow-up. At the time of the MRI (mean 29±9.5 (24–62) months), the median Sanders stages was 7 (5–8). A total of 217 levels of discs and bilateral facet joints were evaluated in the preoperative and follow-up MRI images. Analyses of disc and facet scores revealed no significant differences between patients. Deterioration of previously degenerated discs was noted in one patient (from grade 2 to 3), while previously healthy lower adjacent facet joints were degenerated (grade 2) in another patient. CONCLUSIONSIntermediate discs and facet joints were preserved after growth modulation with VBT surgery at a mean of 29 months of follow-up. Studies in larger cohorts with longer follow-up are warranted to have more in-depth analyses of the effects of relative stabilization and altered biomechanical loads.

Biomechanical and perceptual cushioning sensitivity based on mechanical running shoe properties

Mechanical shoe properties impact running biomechanics, triggering subjective shoe perception. Regarding midsole hardness little is known about the minimal mechanical alteration needed to change running biomechanics and perception. Three ethylene-vinyl acetate midsoles differing in rearfoot hardness (47, 53, 57 Asker C), and peak rearfoot impact acceleration (11.65, 12.40, 12.96 g), were used to create experimental shoe conditions (softer, medium, harder), featuring differing peak rearfoot impact accelerations (12.83, 13.49, 13.95 g) when measured with insoles. Twenty-five male rearfoot runners ran on a concrete loop, while capturing ground reaction forces and lower extremity kinematics of eight valid right foot ground contacts in each shoe. Perception of shoe cushioning and shoe rebound was also assessed during these runs using a 15 cm visual analogue scale. Variable magnitude means were compared for main effects (p < 0.05) by repeated measures analysis of variance, Bonferroni post-hoc tests, and effect size estimation (ηp2). No lower limb kinematic effects were induced by the shoes. Kinetically the softer shoe significantly reduced maximal vertical loading rate 1 compared to the medium and harder shoe (131.28 to 138.40 and 139.54 bw/s). Runners significantly perceived the difference in shoe cushioning between the softer and harder shoe (6.32 to 8.06 cm). For the running shoe model in this research a difference in mechanical peak impact acceleration of 0.66 g was sufficient to elicit different biomechanical loading. To elicit different cushioning perception a mechanical difference of 1.12 g was sufficient, resulting in a maximal vertical loading rate 1 difference of 8.26 bw/s. Knowing a shoe model’s biomechanical and perceptual sensitivity to mechanical alteration allows better informed design, development, and manufacturing decisions.

The Effect of Tooth Loss on Craniofacial Morphology

The morphology of the craniofacial skeleton is known to be responsive to changing biomechanical loads produced by feeding. Edentulism, or tooth loss, has previously been shown to have an impact on the structure of the craniofacial bones, particularly the alveolar bone and palate, as well as on the material properties of the cortical bone. However, it is less clear what effect tooth loss has on the masticatory muscles and their bony attachment sites. In this study, we use geometric morphometrics on human skulls to compare the shape of the mandible and facial skeleton in edentulous and dentate individuals. Following from previous work, we expect that edentulous individuals will exhibit decreased alveolar bone height in both the mandible and maxilla. We further hypothesize that edentulous individuals will display a recession of bone at the insertion sites of the masticatory muscles, namely the zygomatic arch and the mandibular ramus. CT scans of individuals greater than 50 years of age (n=40) were obtained from the New Mexico Decedent Imaging Database (NMDID). Individuals with no teeth were sorted into the edentulous group, while individuals with more than 22 of 36 teeth were sorted into the functionally dentate. 3D Slicer software was used to generate 3D models, and 3D fixed and sliding landmarks were placed along the mandible, maxilla, zygomatic arch, palate, and orbit. Principal component analysis (PCA) and Procrustes ANOVAs were performed separately on the Procrustes-aligned coordinate data for the crania and mandibles. We identified significant differences in facial and mandibular shape between groups. In both cases, differences were largely driven by resorption along the alveolus. Variation in the morphology of edentulous individuals suggests that the time since tooth loss and behavioral factors, such as denture wearing, may impact the degree of alveolar resorption. Interestingly, edentulous individuals tended to have relatively smaller coronoid processes and posteriorly extended mandibular angles. This suggests that tooth loss may result in greater relative atrophy of the temporalis muscle, a jaw elevator/retractor, compared to the masseter muscle, another jaw elevator which is involved in resisting gravity and positional jaw closure. Further studies are needed to investigate the impact of tooth loss on muscle morphology to confirm this. These additive effects between bone resorption and muscle atrophy likely explain the altered facial morphology demonstrated by edentulous populations.

A lattice topology optimization of cervical interbody fusion cage and finite element comparison with ZK60 and Ti-6Al-4V cages

BackgroundIn current clinical practice, the most commonly used fusion cage materials are titanium (Ti) alloys. However, titanium alloys are non-degradable and may cause stress shielding. ZK60 is a bio-absorbable implant that can effectively avoid long-term complications, such as stress shielding effects, implant displacement, and foreign body reactions. In this study, we aimed at investigating the biomechanical behavior of the cervical spine after implanting different interbody fusion cages.MethodsThe finite element (FE) models of anterior cervical disc removal and bone graft fusion (ACDF) with a ZK60 cage and a Ti cage were constructed, respectively. Simulations were performed to evaluate their properties of flexion, extension, lateral bending, and axial rotation of the cervical spine. Moreover, a side-by-side comparison was conducted on the range of motion (ROM), the deformation of cages, the stress in the cages, bone grafts, and cage-end plate interface. Simultaneously, according to the biomechanical analysis results, the microporous structure of the ZK60 cage was improved by the lattice topology optimization technology and validation using static structure.ResultsThe ROMs in the current study were comparable with the results reported in the literature. There was no significant difference in the deformation of the two cages under various conditions. Moreover, the maximum stress occurred at the rear of the cage in all cases. The cage’s and endplate-cage interface’s stress of the ZK60 group was reduced compared with the Ti cage, while the bone graft stress in the ZK60 fusion cage was significantly greater than that in the Ti fusion cage (average 27.70%). We further optimized the cage by filling it with lattice structures, the volume was decreased by 40%, and validation showed more significant biomechanical properties than ZK60 and Ti cages.ConclusionThe application of the ZK60 cage can significantly increase the stress stimulation to the bone graft by reducing the stress shielding effect between the two instrumented bodies. We also observed that the stress of the endplate-cage interface decreased as the reduction of the cage’s stiffness, indicating that subsidence is less likely to occur in the cage with lower stiffness. Moreover, we successfully designed a porous cage based on the biomechanical load by lattice optimization.

The Effect of Footwear, Running Speed, and Location on the Validity of Two Commercially Available Inertial Measurement Units During Running.

Introduction: Most running-related injuries are believed to be caused by abrupt changes in training load, compounded by biomechanical movement patterns. Wearable technology has made it possible for runners to quantify biomechanical loads (e.g., peak positive acceleration; PPA) using commercially available inertial measurement units (IMUs). However, few devices have established criterion validity. The aim of this study was to assess the validity of two commercially available IMUs during running. Secondary aims were to determine the effect of footwear, running speed, and IMU location on PPA.Materials and Methods: Healthy runners underwent a biomechanical running analysis on an instrumented treadmill. Participants ran at their preferred speed in three footwear conditions (neutral, minimalist, and maximalist), and at three speeds (preferred, +10%, −10%) in the neutral running shoes. Four IMUs were affixed at the distal tibia (IMeasureU-Tibia), shoelaces (RunScribe and IMeasureU-Shoe), and insole (Plantiga) of the right shoe. Pearson correlations were calculated for average vertical loading rate (AVLR) and PPA at each IMU location.Results: The AVLR had a high positive association with PPA (IMeasureU-Tibia) in the neutral and maximalist (r = 0.70–0.72; p ≤ 0.001) shoes and in all running speed conditions (r = 0.71–0.83; p ≤ 0.001), but low positive association in the minimalist (r = 0.47; p < 0.05) footwear condition. Conversely, the relationship between AVLR and PPA (Plantiga) was high in the minimalist (r = 0.75; p ≤ 0.001) condition and moderate in the neutral (r = 0.50; p < 0.05) and maximalist (r = 0.57; p < 0.01) footwear. The RunScribe metrics demonstrated low to moderate positive associations (r = 0.40–0.62; p < 0.05) with AVLR across most footwear and speed conditions.Discussion: Our findings indicate that the commercially available Plantiga IMU is comparable to a tibia-mounted IMU when acting as a surrogate for AVLR. However, these results vary between different levels of footwear and running speeds. The shoe-mounted RunScribe IMU exhibited slightly lower positive associations with AVLR. In general, the relationship with AVLR improved for the RunScribe sensor at slower speeds and improved for the Plantiga and tibia-mounted IMeasureU sensors at faster speeds.

P119 Average percent fat is associated with decreased bone mineral density at the hip but increase at the spine longitudinally, where weight shows a positive association at all anatomical locations

Abstract Background/Aims Body composition changes are associated with changes in bone mineral density (BMD). Composite measures of body compartments, such as weight and body mass index (BMI) have a positive association with BMD. The aim was to study average percent fat from dual energy X-ray absorptiometry (DEXA) as a potentially useful clinical measurement. Methods BMD data in grams/cenitmetre2 was collected from DEXA scans after referral from secondary care to the Royal Lancaster Infirmary from 2004-2010. BMD data related to the left and right hip (the neck, Ward’s area, trochanter, and total hip), and the spine (L1-L4) was measured. Data was collected longitudinally, and BMD in g/cm2 was modelled at the regions of the hip and spine using mixed effects linear models. Average percent fat and weight (kg) were used as explanatory variables, whilst adjusting for age at scan, gender, and other risk factors such as FRAX risk factors. Results 7910 patients (88% female) were included, all with average percent fat and weight measurements. The results of the models (Table 1) all have a P value&amp;lt;0.05. Average percent fat had a significant negative association at all regions of the left and right hip, but a significant positive association at the spine. Weight showed a significant positive association with BMD at the hip and spine. P119 Table 1:Effect size estimates from mixed effects models of BMD at regions of the hip, and the spine.Anatomical locationEffect size estimate for average percent fat (95% confidence intervals)Effect size estimate for weight (95% confidence intervals)Left neck-6.63x10-4 (-9.69x10-4, -3.56x10-4)2.07x10-3 (1.91x10-3, 2.23x10-3)Left total-1.03x10-3 (-1.32x10-3, -7.41x10-4)3.45x10-3 (3.29x10-3, 3.61x10-3)Left Ward’s-1.07x10-3 (-1.38x10-3, -7.65x10-4)1.85x10-3 (1.69x10-3, 2.02x10-3)Left trochanter-1.15x10-3 (-1.46x10-3, -8.47x10-4)3.65x10-3 (3.48x10-3, 3.81x10-3)Right neck-6.91x10-4 (-9.94x10-4, -3.88x10-4)1.97x10-3 (1.81x10-3, 2.14x10-3)Right total-1.19x10-3 (-1.48x10-3, -8.96x10-4)3.39x10-3 (3.23x10-3, 3.55x10-3)Right Ward’s-1.07x10-3 (-1.38x10-3, -7.65x10-4)1.85x10-3 (1.69x10-3, 2.02x10-3)Right trochanter-1.19x10-3 (-1.52x10-3, -8.72x10-4)3.65x10-3 (3.39x10-3, 3.73x10-3)Spine (averaged L1-L4)1.76x10-3 (1.46x10-3, 2.05x10-3)1.42x10-3 (1.16x10-3, 1.68x10-3) Conclusion The negative association seen with average percent fat at the hip could reflect the potential negative endocrine effects of fat, and the effect of localized inflammation at the hip. Increased adiposity is also linked to sarcopenia, and further body compositional changes. However, the potential negative effects of increased adiposity at the abdomen and spine are potentially overridden by the increased biomechanical loading generated by the increased adiposity, highlighted by weight’s positive association with BMD at the spine. The average percent fat results are not mirrored with weight at the hip. This highlights that composite measures are not specific enough to measure changes in body composition compartments, and their resulting change in risk related to BMD. Disclosure C. Thurston: None. J. Kerns: None. F. Dondelinger: None. A. Hale: None. M. Bukhari: None.

Differences in Biomechanical Loading Magnitude During a Landing Task in Male Athletes with and without Patellar Tendinopathy.

Prior research has not established if overloading or underloading movement profiles are present in symptomatic and asymptomatic athletes with patellar tendon structural abnormality (PTA) compared to healthy athletes. The purpose was to compare involved limb landing biomechanics between male athletes with and without patellar tendinopathy. Cross-sectional study Setting: Laboratory Patients or Other Participants: 43 males were grouped based on patellar tendon pain & ultrasound imaging of the proximal patellar tendon: symptomatic with PTA (SYM-PTA; n=13; 20±2yrs; 1.8±0.1m; 84±5kg), asymptomatic with PTA (ASYM-PTA; n=15; 21±2yrs; 1.8±0.1m; 82±13kg), and healthy control (CON; n=15; 20±2yrs; 1.8±0.1m; 79±12kg). 3D biomechanics were collected during double-limb jump-landing. Kinematic (knee flexion angle (KF)) and kinetic (vertical ground reaction force (VGRF); internal knee extension moment (KEM); patellar tendon force (FPT)) variables were analyzed as continuous waveforms during the stance phase for the involved limb. Mean values were calculated for each 1% of stance, normalized over 202 data points (0-100%), and plotted with 95% confidence intervals. Statistical significance was defined as a lack of 95% CI overlap for ≥ 6 consecutive data points. SYM-PTA had lesser KF than CON throughout the stance phase. ASYM-PTA had lesser KF than CON in the early and late stance phase. SYM-PTA group had lesser KEM and FPT than CON in early stance, as well as ASYM-PTA in mid-stance. Male athletes with SYM-PTA demonstrated a patellar tendon load-avoidance profile compared to ASYM-PTA and CON athletes. ASYM-PTA did not show evidence of overloading compared to CON. Our findings support the need for individualized treatments for athletes with tendinopathy to maximize load-capacity. ClinicalTrials.gov (#XXX).