Plataforma cone morse, a melhor opção para a biomecânica e estética em próteses sobre implante: uma revisão de literatura / Conemorse platform, the best option for biomechanics and aesthetics in implant-supported prostheses: a literature review

A escolha da plataforma protética em implantodontia é fundamental para garantir o sucesso a longo prazo dos procedimentos. Todos os tipos de conexão protética apresentam vantagens e desvantagens, cabendo ao cirurgião-dentista optar pelo o que melhor se adepta ao seu caso. Uma revisão de literatura foi realizada, abrangendo estudos relevantes que compararam essas duas plataformas protéticas em termos de biomecânica e estética. Foram analisadas revisões de literatura e estudos in vitro, sob as palavras-chave "cone morse", "biomechanics", "abuptment". As pesquisas foram feitas nas bases de dados Scielo e PubMed, e os artigos escolhidos deveriam abordar a estabilidade das conexões, a preservação óssea e a estética peri-implantar. Os resultados da revisão demonstram que a plataforma Cone Morse oferece uma interface mais estável, reduz o afrouxamento de parafusos e minimiza a infiltração bacteriana. Com isso, o Cone Morse contribui para a preservação das estruturas ósseas e gengivais ao redor do implante, tornando-se uma escolha valiosa, especialmente em procedimentos de reabilitação estética.

A choice of the prosthetic platform in implant dentistry is fundamental to ensure long-term success of procedures. All types of prosthetic connections have their advantages and disadvantages, and it's up to the dentist to choose what best suits their case. A literature review was conducted, encompassing relevant studies comparing these two prosthetic platforms in terms of biomechanics and aesthetics. Literature reviews and in vitro studies were analyzed using keywords such as "Cone Morse," "biomechanics," and "abutment." The research was conducted on Scielo and PubMed databases, and the selected articles should address connection stability, bone preservation, and peri-implant aesthetics. The review results demonstrate that the Cone Morse platform offers a more stable interface, reduces screw loosening, and minimizes bacterial infiltration. As a result, Cone Morse contributes to the preservation of bone and gingival structures around the implant, making it a valuable choice, especially in aesthetic rehabilitation procedures.

Optic nerve elongation during fronto-facial surgery for Crouzon syndrome: 3D quantification and clinical implications.

OBJECTIVE: Fronto-facial monobloc advancement with internal distraction (FFMBA) is a key procedure in the management of syndromic craniosynostoses. FFMBA involves circumferential dissection and linear enlargement of the orbit, potentially leading to mechanical stress on the optic nerve (ON). Several reports of transient vision loss during the distraction process led us to investigate ON shape modifications during facial advancement, with the aim to potentially refine current clinical guidelines on postoperative management and the distraction schedule. METHODS: Twenty-six patients with Crouzon syndrome were included in this study. ONs were segmented on pre- and postoperative CT scans. Distraction amplitudes, linear and curved lengths, and cross-section diameters of the ON were assessed along the main axis of the nerve. A two-level hierarchical multivariate linear model was used to screen for factors associated with ON morphology. RESULTS: The mean age at FFMBA was 4.4 ± 3.8 years. Two patients presented with transient impaired vision during distraction. The final mean fronto-orbital and temporo-zygomatic distraction amplitudes were 18 ± 4 mm and 18 ± 6 mm, respectively. At the end of distraction, ONs were elongated (+1.8 mm for curved lengths, p = 0.013), and their mean cross-section was reduced (-1.9 mm2, p < 0.001) in the proximal intraorbital portion (first 15 mm). In the 2 patients with visual symptoms, functional impairment was associated with ON area reduction (OR 0.487, p < 0.001) and increased temporo-zygomatic distraction amplitude (OR 2.240, p < 0.001). CONCLUSIONS: ON was elongated during FFMBA, with proximal diameter reduction. Transient visual impairment with normal fundus examination during distraction seemed to have a morphological basis, based on 2 cases. These results suggest the importance of vision monitoring associated with fundus examination during distraction, and advocate for early extubation after FFMBA to allow clinical follow-up.

Effect of ball positions on trunk, hip, knee, and ankle joint kinematics and kinetics during a spike jump in volleyball.

BACKGROUND: Anterior cruciate ligament injuries are serious conditions encountered in volleyball players and occur frequently during spike jump landings. During spike jumps, the lower limb kinematics and kinetics during landing may be altered in relation to the ball position. RESEARCH QUESTION: Does the ball position have an effect on lower-limb kinematics and kinetics during spike jumps? METHODS: We measured the lower limb kinematics and kinetics of 20 healthy female college volleyball athletes during a spike jump using a three-dimensional motion analysis system. The ball positions were set to normal, dominant, and non-dominant positions. A repeated analysis of variance was used to compare the lower limb kinematics and kinetics at the initial contact and the maximum knee flexion during jump landing. Additionally, statistical parametric mapping analysis was used to analyze changes over time during the spike jumps. RESULTS: At the initial contact of the spike jump landing, the knee valgus angle, trunk lateral bending angle, and maximum knee valgus moment when the ball was set at the non-dominant position increased compared to those at the dominant position. Statistical parametric mapping analysis showed no significant change in knee valgus angle and moment of jump landing. CONCLUSION: Knee valgus angle, trunk lateral bending angle, and maximum knee valgus moment increased with the non-dominant position; furthermore, the risk of ACL injury may also be increased. SIGNIFICANCE: The posture at ball impact may influence the landing kinematics and kinetics. Therefore, it is necessary to pay close attention to movements during and prior to landing.

Mapping wrist motion: 3D CT analysis after scapholunate ligament transection.

The injury of the scapholunate (SL) ligament is common in wrist traumas leading to pain and reduced wrist function. The wrist's unique joint design and possible underlying theories as the carpal row theory were subject to earlier investigations studying wrist kinematics. Nevertheless, a comprehensive understanding of how SL ligament injuries affect wrist biomechanics is still lacking. Through a quantitative analysis of carpal bone motion patterns, we evaluated the impact on wrist kinematics occurring after SL ligament injury. We conducted a study using computer tomography imaging to analyse wrist kinematics after SL ligament transection in 21 fresh-frozen anatomical specimens. The collected data were then transformed into 3D models, employing both standardized global and object coordinate systems. The study encompassed the evaluation of rotation and translation for each individual carpal bone, as well as the ulna, and all metacarpal bones in reference to the radius. The study showed a significant increase in rotation towards palmar (p < 0.01), particularly notable for the scaphoid, following transection of the SL ligament during palmar flexion. Ulnar deviation did not significantly affect rotation or translation, and radial deviation also showed no significant changes in rotation or translation. The study highlights the significance of the SL ligament in wrist kinematics, revealing that SL ligament tears lead to changes in wrist motion. While we observed significant rotational changes for the scaphoid, other carpal bones showed less pronounced alterations, emphasizing the complexity of wrist biomechanics.

A biomechanical study of a polymer material bundled rib fracture fixator.

BACKGROUND: Rib fractures are one of the most common blunt injuries, accounting for approximately 10% of all trauma patients and 60% of thoracic injuries. Multiple rib fractures, especially flail chest, can cause local chest wall softening due to the loss of rib support, leading to paradoxical breathing, severe pain, and a high likelihood of accompanying lung contusions. OBJECTIVE: This study investigates the mechanical properties of a new polymer material rib internal fixator to provide theoretical data for its clinical use. METHODS: We conducted in vitro mechanical tests on 20 fresh caudal fin sheep ribs, using different fracture models across four randomly assigned groups (five ribs per group). The fixators were assessed using non-destructive three-point bending, torsion, and unilateral compression tests, with results averaged. Additionally, finite element analysis compared stress and strain in the polymer fixators and titanium alloy rib plates during bending and torsion tests. RESULTS: In vitro tests showed that the polymer fixators handled loads effectively up to a maximum without increase beyond a certain displacement. Bending and torsion tests via finite element analysis showed the polymer material sustained lower maximum equivalent stresses (84.455 MPa and 14.426 MPa) compared to titanium alloy plates (219.88 MPa and 46.47 MPa). CONCLUSION: The polymer rib fixator demonstrated sufficient strength for rib fracture fixation and was superior in stress management compared to titanium alloy plates in both bending and torsion tests, supporting its potential clinical application.

Validation of reliable reference genes for qPCR of CD4+ T cells exposed to compressive strain.

For accurate interpretation of quantitative real-time PCR (qPCR) data, stable reference genes are essential for normalization of target genes. To date, there is no information on reliable housekeeping genes in CD4+ T cells in a three-dimensional (3D) matrix under pressure stimulation. This in vitro study describes for the first time a method for pressure stimulation of CD4+ T cells in a 3D matrix in the context of orthodontic tooth movement (OTM) and identifies a set of reliable reference genes. CD4+ T cells were isolated from murine spleen and activated with anti-CD3/-CD28 Dynabeads (Thermo Fisher, Langenselbold, Germany) on standard cell culture plates or in 3D scaffolds with or without compressive strain. Expression stability of nine potential reference genes was examined using four mathematical algorithms. Gene expression of Il2 was normalized to all potential reference genes to highlight the importance of correct normalization. Cell proliferation and the expression of the surface markers CD25 and CD69 were also determined. The 3D matrix did not inhibit proliferation after immunological activation of T cells and embedded the cells sufficiently to expose them to pressure load. Expression of ubiquitin C (Ubc) and hypoxanthine phosphoribosyltransferase (Hprt) was the most stable under all conditions tested. A combination of these two genes was suitable for normalization of qPCR data. Normalization of Il2 gene expression showed highly variable results depending on the reference gene used. Pressure reduced cell proliferation and the number of CD69-positive T cells. This study provides a basis for performing valid and reliable qPCR experiments with CD4+ T cells cultured in 3D scaffolds and exposed to compressive forces simulating OTM.

Finite element simulations of smart fracture plates capable of cyclic shortening and lengthening: which stroke for which fracture?

Introduction: Bone healing can be improved by axial micromovement, as has been shown in animals and human patients with external fixators. In the development of smart fracture plates, the ideal amount of stroke for different fracture types in the different healing stages is currently unknown. It was hypothesized that the resulting strain in the fracture gap of a simple tibial shaft fracture does not vary with the amount of axial stroke in the plate, the fracture gap size, and the fracture angle. Methods: With finite element simulations based on body donation computed tomography data, the second invariant of the deviatoric strain tensor (J2), strain energy density, hydrostatic strain, octahedral shear strain, and percentage of the fracture gap in the "perfect healing window" were computed for different gap sizes (1-3 mm), angles (5°-60°), and plate stroke levels (0.05-0.60 mm) in three healing stages. Multiple linear regression analyses were performed. Results: Findings showed that an active fracture plate should deliver an axial stroke in the range of 0.10-0.45 mm. Different optimal stroke values were found for each healing phase, namely, 0.10-0.25 mm for the first, 0.10 mm for the second, and 0.35-0.45 mm for the third healing phase, depending on the fracture gap size and less on the fracture angle. J2, hydrostatic strain, octahedral shear strain and the strain energy density correlated with the fracture gap size and angle (all p < 0.001). The influence of the fracture gap size and angle on the variability (adjusted R2) in several outcome measures in the fracture gap was shown to vary throughout healing. The contribution to the variability of the percentage of the fracture gap in the perfect healing window was greatest during the second healing phase. For J2, strain energy density, hydrostatic strain, and octahedral shear strain, the fracture gap size showed the greatest contribution in the third fracture healing phase, while the influence of fracture angle was independent of the healing phase. Discussion: The present findings are relevant for implant development and to design clinical studies that aim to accelerate fracture healing using axial micromovement.

Instrumented mouthguards in elite-level men's and women's rugby union: characterising tackle-based head acceleration events.

Objectives: To examine the propensity of tackle height and the number of tacklers that result in head acceleration events (HAEs) in elite-level male and female rugby tackles. Methods: Instrumented mouthguard data were collected from women (n=67) and men (n=72) elite-level rugby players from five elite and three international teams. Peak linear acceleration and peak angular acceleration were extracted from HAEs. Propensities for HAEs at a range of thresholds were calculated as the proportion of tackles/carries that resulted in an HAE exceeding a given magnitude for coded tackle height (low, medium, high) and number of tacklers. Propensity ratios with 95% CIs were calculated for tackle heights and number of tacklers. Results: High tackles had a 32.7 (95% CI=6.89 to 155.02) and 41.2 (95% CI=9.22 to 184.58) propensity ratio to cause ball carrier HAEs>30 g compared with medium tackles for men and women, respectively. Low tackles had a 2.6 (95% CI=1.91 to 3.42) and 5.3 (95% CI=3.28 to 8.53) propensity ratio to cause tackler HAEs>30 g compared with medium tackles for men and women, respectively. In men, multiple tacklers had a higher propensity ratio (6.1; 95% CI=3.71 to 9.93) than singular tacklers to cause ball carrier HAEs>30 g but a lower propensity ratio (0.4; 95% CI=0.29 to 0.56) to cause tackler HAEs>30 g. No significant differences were observed in female tacklers or carriers for singular or multiple tacklers. Conclusion: To limit HAE exposure, rule changes and coaching interventions that promote tacklers aiming for the torso (medium tackle) could be explored, along with changes to multiple tackler events in the male game.

Unraveling stroke gait deviations with movement analytics, more than meets the eye: a case control study.

Background: This study aimed to identify and quantify the kinematic and kinetic gait deviations in post-stroke hemiplegic patients with matched healthy controls using Statistical Parametric Mapping (SPM). Methods: Fifteen chronic stroke patients [4 females, 11 males; age 53.7 (standard deviation 12.2) years; body mass 65.4 (10.4) kg; standing height 168.5 (9.6) cm] and 15 matched healthy controls [4 females, 11 males; age 52.9 (11.7) years; body weight 66.5 (10.7) years; standing height 168.3 (8.8) cm] were recruited. In a 10-m walking task, joint angles, ground reaction forces (GRF), and joint moments were collected, analyzed, and compared using SPM for an entire gait cycle. Results: Generally, when comparing the stroke patients' affected (hemiplegic) and less-affected (contralateral) limbs with the control group, SPM identified significant differences in the late stance phase and early swing phase in the joint angles and moments in bilateral limbs (all p < 0.005). In addition, the vertical and anteroposterior components of GRF were significantly different in various periods of the stance phase (all p < 0.005), while the mediolateral component showed no differences between the two groups. Conclusion: SPM was able to detect abnormal gait patterns in both the affected and less-affected limbs of stroke patients with significant differences when compared with matched controls. The findings draw attention to significant quantifiable gait deviations in the less-affected post-stroke limb with the potential impact to inform gait retraining strategies for clinicians and physiotherapists.

The potential effect of romosozumab on perioperative management for instrumentation surgery.

Background: Age-related changes in bone health increase the risk for complications in elderly patients undergoing orthopedic surgery. Osteoporosis is a key therapeutic target that needs to be addressed to ensure successful instrumentation surgery. The effectiveness of pharmacological interventions in orthopedic surgery, particularly the new drug romosozumab, is still unknown. We aim to evaluate the effect of 3-month romosozumab treatment on biomechanical parameters related to spinal instrumentation surgery, using the Quantitative Computed Tomography (QCT)-based Finite Element Method (FEM). Methods: This open-labeled, prospective study included 81 patients aged 60 to 90 years, who met the osteoporosis criteria and were scheduled for either romosozumab or eldecalcitol treatment. Patients were assessed using blood samples, dual-energy absorptiometry (DXA), and QCT. Biomechanical parameters were evaluated using FEM at baseline and 3 months post-treatment. The primary endpoints were biomechanical parameters at 3 months, while secondary endpoints included changes in regional volumetric bone mineral density around the pedicle (P-vBMD) and vertebral body (V-vBMD). Results: Romosozumab treatment led to significant gains in P-vBMD, and V-vBMD compared to eldecalcitol at 3 months. Notably, the romosozumab group showed greater improvements in all biomechanical parameters estimated by FEM at 3 months compared to the eldecalcitol group. Conclusion: Romosozumab significantly increased the regional vBMD as well as biomechanical parameters, potentially offering clinical benefits in reducing post-operative complications in patients with osteoporosis undergoing orthopedic instrumentation surgery. This study highlights the novel advantages of romosozumab treatment and advocates further research on its effectiveness in perioperative management.

Peak vertical ground reaction force used to identify sub-groups of individuals with differing biomechanical gait profiles post-anterior cruciate ligament reconstruction.

Lesser peak vertical ground reaction force (vGRF) has been widely reported among individuals with anterior cruciate ligament reconstruction (ACLR). Peak vGRF remains less than uninjured controls and relatively stable during the first year following ACLR. However, it is unknown whether there are subgroups of individuals exhibiting consistently greater peak vGRF in the first 6-months following ACLR and if individuals with consistently greater peak vGRF exhibit kinematic and kinetic gait differences compared to individuals with low vGRF. The purpose of this study was to determine if distinct clusters exist based upon magnitude of peak vGRF 2- and 6-months post-ACLR. Subsequently, we explored between cluster differences in vGRF, knee flexion angle, and sagittal and frontal plane knee kinetics throughout stance between clusters. Forty-three individuals (58.1%female, 21.4 ± 4.4 years-old, 95.3% patellar-tendon autograft) completed five gait trials at their habitual walking speed 2- and 6-months post-ACLR. A single K-means cluster analysis was used to identify clusters of individuals based on peak vGRF at 2- and 6-months post-ACLR. Functional waveform analyses were used to compare gait outcomes between clusters with and without controlling for gait speed and age. We identified two clusters that included a subgroup with high vGRF (n = 16) and low vGRF (n = 27). The cluster with high vGRF demonstrated greater vGRFs, knee flexion angles, and knee extension moments during early stance as compared to the low vGRF cluster 2- and 6-months post-ACLR. Individuals with peak vGRF ≥1.02 times body-weight 2-months post-ACLR had 35.4 times greater odds of being assigned to the high vGRF cluster.

Angle-Specific Analysis of Isokinetic Quadriceps and Hamstring Strength at 6 and 12 Months After Unilateral ACL Reconstruction.

BACKGROUND: Quadriceps and hamstring strength deficits are related to the increased risk of reinjury after anterior cruciate ligament reconstruction (ACLR). HYPOTHESIS: Knee angle-specific quadriceps and hamstring strength differences would be observed in patients with ACLR 6 and 12 months after surgery. STUDY DESIGN: Case-series. LEVEL OF EVIDENCE: Level 4. METHODS: A total of 23 postprimary unilateral ACLR patients followed-up at 6 and 12 months postoperatively and 25 controls were included. Isokinetic knee extension and flexion strength were evaluated at 60 deg/s from 20° to 90°. Statistical parametric mapping were performed to explore the angle-specific strength and the limb symmetry index (LSI). RESULTS: At 6 months postoperatively, the reconstructed leg demonstrated lower knee extension and flexion strength than the contralateral (20°-77°, 24°-90°) (P < 0.01) and control legs (22°-90°, 40°-82°) (P < 0.01). From 6 months to 12 months, knee extension (60°-90°) and flexion (20°-79°) strength improved in the reconstructed leg (P < 0.05), while LSI remained unchanged (P > 0.02). At 12 months, knee extension strength differences persisted in the reconstructed leg compared with the contralateral (20°-81°) and controls (25°-63°) (P < 0.01). ACLR patients had lower LSI of knee extension strength at 6 (20°-59°) and 12 (24°-57°) months postoperatively than the controls (P < 0.02). CONCLUSION: The reconstructed leg exhibited differences in knee extension strength compared with the contralateral and control legs. Although bilateral knee extension strength increased from 6 to 12 months postoperatively, LSI did not show improvement during this period. CLINICAL RELEVANCE: Quadriceps restoration was observed only in knee flexion angles greater than 60° compared with controls. Future studies should investigate whether knee extension strength, especially in lower flexion angles, can be enhanced through rehabilitation programs. Furthermore, assessing the impact of this improvement on long-term outcomes and reinjury risk in ACLR patients is warranted.

The Impact of Drive Leg Impulse and Slope on Throwing Velocity and Kinematics in the Competitive Throwing Athlete.

BACKGROUND: Multiple studies have analyzed pitching kinematics using motion analysis technology, but lower extremity drive leg impulse (DLI) and drive leg slope (DLS) are not as well characterized. The purpose of this study was to investigate associations between DLI and DLS and pitch velocity as well as angular velocity of the pelvis, trunk, and humerus. HYPOTHESIS: Increased DLI and DLS will be correlated positively with pitch velocity and associated with increased angular velocities in the humerus, trunk, and pelvis. STUDY DESIGN: Retrospective case series. LEVEL OF EVIDENCE: Level 4. METHODS: Three-dimensional motion analyses data from 174 pitchers (age, 17.0 ± 1.0 years; height, 1.82 ± 0.07 m; weight, 80.0 ± 11.3 kg) throwing combined 613 fastball pitches were included. Pitchers threw 2 to 5 pitches, and the variables collected between pitches were averaged and recorded. Statistical analysis was performed using linear regressions to determine the association between DLS as well as DLI and pitch velocity and angular velocities of the pelvis, trunk, and humerus. RESULTS: Pitchers with higher DLI were associated with lower pitch velocities (ß = -22.32; 95% CI, -32.75 to -11.88, P < 0.01). There were no significant associations for DLS and velocity (ß = -0.60; 95% CI, -1.48 to 0.29, P = 0.18) or DLS and DLI with rotational velocities except for DLI and trunk kinematics (ß = -0.60; 95% CI, -1.48 to 0.29, P = 0.18). CONCLUSION: In the combined cohort, DLI correlated negatively with pitch velocity, although this relationship does not exist in the subgroup analysis. Higher DLS was found in pitchers with slower pitch velocities in the elite, high school, and youth groups, although not statistically significant. No associations were found with DLS and any angular velocities between any level of play analyzed in this study, suggesting no consistent association regardless of playing level.

Comparative Biomechanical Study of Fragment-Specific Plates and Headless Screws for Radial Styloid and Lunate Facet Fixation in Distal Radius Fracture Evaluated in a Synthetic Composite.

PURPOSE: To evaluate the compressive stiffness (ability to resist compression under an applied load) of fragment-specific plate and headless screw fixation for radial styloid and volar lunate facet fractures in a synthetic composite distal radius. METHODS: A simulated radial styloid fracture (AO type B1.1) and simulated volar lunate facet fracture (AO type B3.3) were created in synthetic composite distal radii and fixed with a fragment-specific plate (FSP) using a radial styloid or lunate facet plate or with two- or three-headless screws (2HS, 3HS), creating 6 fixation models: B1.1/FSP, B1.1/2HS, B1.1/3HS, B3.3/FSP, B3.3/2HS, and B3.3/3HS. Compressive stiffness of fixation constructs under initial static load, cyclic load, and final static load was investigated. Nonaxial loadings, including shearing and rotation, were not evaluated. RESULTS: Regarding AO type B1.1, the mean stiffness of the B1.1/FSP construct was not significantly different from the intact radius, and the mean stiffness was greatest in the B1.1/3HS and lowest in the B1.1/2HS construct. For AO type B3.3, the mean stiffness of the B3.3/3HS construct was not significantly different from the intact radius, and the mean stiffness of the B3.3/FSP and B3.3/2HS construct was greatest and lowest, respectively. Minimal differences in stiffness between initial and final static loads confirmed that there was no evidence of failure implant under cyclic compressive loads. CONCLUSIONS: Fragment-specific plates and two- or three-headless screw fixation maintained mechanical stability through compressive cyclic loading for radial styloid and volar lunate facet fractures. The FSPs and three-headless screws fixations provided superior stiffness over the two-headless screws fixation. There was no articular fracture failure in all fixation constructs with initial static compression, cyclic loading, and final compression. CLINICAL RELEVANCE: Fragment-specific plates and headless screws can both be considered as adequate fixation for radial styloid and volar lunate facet fractures.

Sex differences in cervical disc height and neck muscle activation during manipulation of external load from helmets.

Neck pain associated with helmet-wear is an occupational health problem often observed in helicopter pilots and aircrew. Whether aircrew helmet wearing is associated with physiological and biomechanical differences between sexes is currently unknown. This study investigated neuromuscular activation patterns during different helmet-wearing conditions. The helmet load was manipulated through a novel Helmet Balancing System (HBS) in healthy, non-pilot male and female participants (n = 10 each, age 19-45 years) in two phases. Phase A assessed the acute effects of helmet-wear on neck muscles activation during head movements. Phase B examined changes in muscle activity and cervical disc height after wearing a helmet for 45 min. In Phase A, muscle activity was similar between sexes in many movements, but it was higher in female participants when wearing a helmet than in males. The HBS reduced muscle activity in both sexes. In Phase B, female participants exhibited a greater level of muscular fatigue, and male participants' cervical disc height was significantly decreased [5.7 (1.4) vs. 4.4 (1.5) mm, P < 0.001] after continuous wearing. Both sexes showed no significant change in muscle fatigue and disc height [male: 5.0 (1.3) vs. 5.2 (1.4) mm, P = 0.604] after applying HBS. These findings demonstrate sex-specific physiological and biomechanical responses to wearing a helmet. They may indicate different postural and motor control strategies, associated with different neck pain aetiologies in male and female aircrew, the knowledge of which is important to reduce or prevent musculoskeletal injuries associated with helmet wearing. HIGHLIGHTS: What is the central question of this study? Do sex differences exist in the neck physiological response to helmet-wearing? What is the main finding and its importance? Sex differences exist in both the acute response and after 45 min of helmet wearing: during a given head movement, female participants' muscle activity was greater than male participants' and females also demonstrated greater muscular fatigue after continuous helmet-wear than males while cervical disc height showed a significant reduction after 45 min helmet-wear in males only. These findings could provide insight into future training or injury prevention strategy for pilots.

Modelling take-off moment arms in an ornithocheiraean pterosaur.

Take-off is a vital part of powered flight which likely constrains the size of birds, yet extinct pterosaurs are known to have reached far larger sizes. Three different hypothesised take-off motions (bipedal burst launching, bipedal countermotion launching, and quadrupedal launching) have been proposed as explanations for how pterosaurs became airborne and circumvented this proposed morphological limit. We have constructed a computational musculoskeletal model of a 5 m wingspan ornithocheiraean pterosaur, reconstructing thirty-four key muscles to estimate the muscle moment arms throughout the three hypothesised take-off motions. Range of motion constrained hypothetical kinematic sequences for bipedal and quadrupedal take-off motions were modelled after extant flying vertebrates. Across our simulations we did not find higher hindlimb moment arms for bipedal take-off motions or noticeably higher forelimb moment arms in the forelimb for quadrupedal take-off motions. Despite this, in all our models we found the muscles utilised in the quadrupedal take-off have the largest total launch applicable moment arms throughout the entire take-off sequences and for the take-off pose. This indicates the potential availability of higher leverage for a quadrupedal take-off than hypothesised bipedal motions in pterosaurs pending further examination of muscle forces.

Predicting incident radiographic knee osteoarthritis through quantitative meniscal lesion parameters: data from the osteoarthritis initiative.

BACKGROUND: This study investigates the potential of novel meniscal parameters as predictive factors for incident radiographic knee osteoarthritis (ROA) over a span of four years, as part of the Osteoarthritis Initiative (OAI) study. OBJECTIVES: Quantitative measurements of meniscal parameters alteration could serve as predictors of OA's occurrence and progression. METHODS AND MATERIALS: A nested matched case-control study design was used to select participants from OAI study. Case knees (n = 178) were defined as those with incident ROA (Kellgren Lawrence Grade (KLG) 0 or 1 at baseline (BL), evolving into KLG 2 or above by year 4). Control knees were matched one-to-one by sex, age and radiographic status with case knees. The mean distance from medial-to-lateral meniscal lesions [Mean(MLD)], mean value of tibial plateau width [Mean(TPW)] and the mean of the relative percentage of the medial-to-lateral meniscal lesions distance [Mean(RMLD)] were evaluated through coronal T2-weighted turbo spin echo (TSE) MRI at P-0 (visit when incident ROA was found on radiograph), P-1(one year prior to P-0) and baseline, respectively. Using the imaging data of one patient, the mechanism was investigated by finite element analysis. RESULTS: Participants were on average 60.22 years old, predominantly female (66.7%) and overweight (mean BMI: 28.15). Mean(MLD) and Mean(RMLD) were significantly greater for incident knees compared to no incident knees at baseline, P-1 and P-0. [Mean(MLD), Mean(RMLD); (42.56-49.73) mean ± (7.70-9.52) mm SD vs. (38.14-40.78) mean ± (5.51-7.05)mm SD; (58.61-68.95) mean ± (8.52-11.40) mm SD vs. (52.52-56.35) mean ± (6.53-7.85)mm SD, respectively]. Baseline Mean(MLD) and Mean(RMLD), [Adjusted OR, 95%CI: 1.11(1.07 to 1.16) and 1.13(1.09 to 1.17), respectively], were associated with incident ROA during 4 years, However, Mean(TPW) [Adjusted OR, 95%CI: 0.98(0.94 to 1.02)] was not associated with incident ROA during 4 years. While Mean(TPW) at P-1 and P-0 was not associated with the risk of incident ROA, Mean(MLD) and Mean(RMLD) at P-1 and P-0 were significantly positively associated with the risk of incident ROA. CONCLUSIONS: The meniscal parameters alteration could be an important imaging biomarker to predict the occurrence of ROA.

Metamaterial design for aortic aneurysm simulation using 3D printing.

INTRODUCTION: The use of three-dimensional (3D) printed anatomic models is steadily increasing in research and as a tool for clinical decision-making. The mechanical properties of polymers and metamaterials were investigated to evaluate their application in mimicking the biomechanics of the aortic vessel wall. METHODOLOGY: Uniaxial tensile tests were performed to determine the elastic modulus, mechanical stress, and strain of 3D printed samples. We used a combination of materials, designed to mimic biological tissues' properties, the rigid VeroTM family, and the flexible Agilus30™. Metamaterials were designed by tessellating unit cells that were used as lattice-reinforcement to tune their mechanical properties. The lattice-reinforcements were based on two groups of patterns, mainly responding to the movement between links/threads (chain and knitted) or to deformation (origami and diamond crystal). The mechanical properties of the printed materials were compared with the characteristics of healthy and aneurysmal aortas. RESULTS: Uniaxial tensile tests showed that the use of a lattice-reinforcement increased rigidity and may increase the maximum stress generated. The pattern and material of the lattice-reinforcement may increase or reduce the strain at maximum stress, which is also affected by the base material used. Printed samples showed max stress ranging from 0.39 ± 0.01 MPa to 0.88 ± 0.02 MPa, and strain at max stress ranging from 70.44 ± 0.86% to 158.21 ± 8.99%. An example of an application was created by inserting a metamaterial designed as a lattice-reinforcement on a model of the aorta to simulate an abdominal aortic aneurysm. CONCLUSION: The maximum stresses obtained with the printed models were similar to those of aortic tissue reported in the literature, despite the fact that the models did not perfectly reproduce the biological tissue behavior.

Time course of biomechanics during jump landing before and after two different fatigue tasks.

Objective: Muscle fatigue contributes to anterior cruciate ligament (ACL) injuries, with increased knee and hip abduction observed during fatigue. However, there have been no reports revealing the differences between fatigue tasks or the duration of these changes. In this study, we conducted single-leg drop landings before and after hip and knee fatigue tasks to elucidate the changes in lower limb biomechanics over time. Methods: Twenty-two male participants performed single-leg drop landings before, immediately after, and 5, 10, and 15 min after fatigue tasks involving isokinetic hip abduction/adduction (hip fatigue task [HFT]) and knee extension/flexion (knee fatigue task [KFT]). Hip and knee kinematic and kinetic data were collected using a three-dimensional motion analysis device and two force plates. A two-way ANOVA was performed with both the fatigue task (HFT and KFT) and time point (Time 1 to Time 4) as factors, and the main effects and interactions were calculated. Results: The knee adduction angle after the HFT was significantly greater than that after KFT immediately following the fatigue task. The knee flexion moment was significantly lower in the KFT, whereas the knee adduction and internal rotation moments were significantly higher in the HFT immediately after the fatigue task. Conclusion: This study revealed distinct kinematic and kinetic changes specific to each fatigue task, particularly in the frontal plane for hip joint tasks and the sagittal plane for knee joint tasks. These findings could assist in the development of ACL injury prevention programs tailored to the functional improvement and exercise capacity of each joint.

Gearing in a hydrostatic skeleton: the tube feet of juvenile sea stars (Leptasterias sp.).

Hydrostatic skeletons, such as an elephant trunk or a squid tentacle, permit the transmission of mechanical work through a soft body. Despite the ubiquity of these structures among animals, we generally do not understand how differences in their morphology affect their ability to transmit muscular work. Therefore, the present study used mathematical modeling, morphometrics, and kinematics to understand the transmission of force and displacement in the tube feet of the juvenile six-rayed star (Leptasterias sp.). An inverse-dynamic analysis revealed that the forces generated by the feet during crawling primarily serve to overcome the submerged weight of the body. These forces were disproportionately generated by the feet at more proximal positions along each ray, which were used more frequently for crawling. Due to a combination of mechanical advantage and muscle mass, these proximal feet exhibited a greater capacity for force generation than the distal feet. However, the higher displacement advantage of the more elongated distal feet offer a superior ability to extend the feet into the environment. Therefore, the morphology of tube feet demonstrates a gradient in gearing along each ray that compliments their role in behavior.