Acta of bioengineering and biomechanics最新文献

Purpose: Brain aneurysms often prove fatal if ruptured, therefore, understanding their mechanical behaviour in the coupled system of vessels and blood flow can significantly help preventive surgical treatment. The purpose of this work was to analyse measurement data and to determine material parameters for the hyperelastic Mooney-Rivlin model for model building and numerical simulations of aneurysms.

Methods: A total of 88 human brain aneurysm specimens of 41 patients obtained from surgery were processed in this work based on the tests performed by the authors in a previous project. A novel algorithm was proposed and applied in this work to fit stress-stretch ratio curves for multiple measurement data using constrained optimization with hard conditions to comply with known mechanical behaviour.

Results: The method produced parameters of stretch ratio-stress curves for a number of groups of the specimens representing the average as well as the extreme stresses, separately for male and female subsamples. Stretch range both in compression and in tension up to rupture was covered and material stability for the entire range was also verified.

Conclusions: The fitted curves with recommended range of validity are directly applicable to numerical finite element or coupled simulations of aneurysms supporting preventive medical treatment or decision making.

Purpose: This analysis is the first part of research that aims to develop a model of the tribological wear of PE-UHMW cord - biometal rod combination. This type of sliding joint is applied in spine stabilization systems that enable the treatment of early-onset idiopathic scoliosis.

Methods: The friction tests included force measurements, followed by the determination of static and kinetic friction coefficients as a function of the number of the performed movement cycles, and static friction coefficient with regards to the string tension force FN in the range of 50-300 N. Additionally, the surface roughness and microscopic observations of the metal rods were made. The friction measurements were carried out at a stabilized temperature T = 38 °C in the presence of distilled water and acidic sodium lactate.

Results: The measurements confirmed the impact of both the number of completed movement cycles and the value of the force loaded on the cord on the static friction coefficient. Similar values of kinetic friction force occur for the pairs with the titanium alloys rods, as well as for the pairs with the steel and CoCr rod. The type of lubricant affected the obtained measurement results unevenly: (Ti6Al4V and Ti6Al7Nb - slight impact, steel 316L and CoCrMo - large impact). During microscopic observations, numerous wear products, were visible, including harder than the base material large conglomerates.

Conclusions: Susceptibility of polymer fibres results in its increased resistance to wear, but it can be also combined with an increase in wear of the surface of the metal rod.

Purpose: The purpose of this study was to assess the influence of physiological and kinematic predictors on 400-m front crawl race in young male swimmers and to consider the interrelation between them.

Methods: Nineteen male swimmers took part in this study (age: 13.5 ± 0.44 years, height: 168.6 ± 7.77 cm, body mass: 56.9 ± 10.57 kg). Measurements of physiological parameters were conducted using expired air analyzer (Start 2000 MES, Poland) during step-test in water flume. Kinematic indices were computed while analyzing video recording of 400-m front crawl race. To check for possible influence of biological age (BA) diversity in studied group, partial correlation with age control was computed.

Results: Swimming to exhaustion in water flume defined as speed at maximum oxygen uptake and anaerobic threshold ( VVO2 max and VAT) occurred to be strongly positively correlated with 400-m race speed. Speed in surface swimming zones (Vsurface) was related to ability of kinematics adjustment and significantly correlated with stroke index (SI). Vsurface at the beginning and the end of the race, i.e., at 1st, 7th and 8th lap interplayed with stroke rate (SR) measured at corresponding laps.

Conclusions: Our study showed that 400-m front crawl performance of young male swimmers is strongly dependent on swimming efficiency developed with aerobic conditioning. Significant role of proper pacing strategy was also identified, which indicates that race pace training should be implemented.

Purpose: The aim of this study was to assess the biomechanics of the foot in beauty pageant contestants wearing shoes that increase calcaneal height. Plantar pressure distribution and postural balance were examined in women after one hour of wearing high-heeled shoes.

Methods: Foot arch measurements were conducted using EPSR1. Based on these measurements, 18 of the 19 tested women were diagnosed with significant pes cavus.

Results: The experiment revealed a significant reduction in the excessively high metatarsal arch of both feet. The mean load on the metatarsus measured at rest was 0.0% in both feet, and it increased by 0.6% in the left leg (p ≤ 0.022; Z = 2.293) and by 2.7% in the right leg (p ≤ 0.023; Z = 2.271). These results suggest that excessive stretching of the plantar fascia and impaired function of the short muscles of the foot lead to a temporary reduction in the arch of the foot. This phenomenon can be compared to stretching a bowstring and its return to the shortest length under static conditions. A statistical analysis of the results of stabilographic measurements revealed significant changes only in the left foot barycenter. An analysis of the ability to maintain postural balance revealed that the observed changes contributed to postural destabilization at p ≤ 0.011 and Z = 2.535.

Conclusions: Further research involving electromyography tests is needed to examine plantar muscle tension during isotonic contractions. The duration of the exercise-induced reduction in pes cavus should also be determined for therapeutic purposes.

Purpose: The aim of this study was to determine the reliability of the RunScribe™ system to measure kinematic variables of the pelvis during walking and running.

Methods: In this study, a treadmill protocol was implemented where the participants (n = 23) completed 3 sets of 1 minute at 5, 10 and 15 km/h.

Results: All the recorded measurements during walking reported a low reliability with coefficients of variation (CV) greater than 10% in all variables and small-moderate intraclass correlation coefficient (ICC) (<0.6) in seven out of ten variables. Similarly, the CVs reported in running were greater than 10%, except for the maximum angular rate in the obliquity of the pelvis and the vertical oscillation that together with the angular velocity variables showed almost perfect ICCs (>0.92).

Conclusions: Therefore, the data obtained suggests that the RunScribe™ system with 3 IMUs does not provide reliable metrics about the kinematics of the pelvis during locomotion (i.e., walking and running).

Purpose: Rotation of the knee puts stress on the medial meniscus and can be a factor in the progression of knee osteoarthritis. This study aimed to investigate the rotational moment (internal rotation and external rotation) of the knee during gait and relationship between the rotational moments of the knee and other joints, including the free moment during gait.

Methods: We included 18 patients with medial meniscus tears (MM group) and 10 asymptomatic participants in this study. We performed 3D gait analysis. The internal ankle, knee, and hip rotational moments as well as free moment were compared between the groups. Additionally, we investigated correlations between rotational moments of the knee and other joints during gait.

Results: The maximal knee external rotation moment in the MM group was smaller than that in the asymptomatic group ( p = 0.04, g = 0.76); however, there were no significant differences in the maximal internal rotation moment between the groups ( p = 0.97, g = 0.02). The internal rotation (external knee external rotation) moment positively correlated with the hip internal rotation moment ( p 〈 0.01, r = 0.69) in the MM group.

Conclusions: The internal rotation (passive knee external rotation moment) did not decrease sufficiently, and correlation was observed between moments of the knee and hip in the MM group, especially during the late stance phase of gait. Reducing these abnormal moments during gait through rehabilitation may be important in patients with medial meniscus tears to prevent rapid progression of knee osteoarthritis.

Purpose: The aim of this study was to compare the effects of scapular stabilization exercise with and without cognitive functional therapy (CFT) on disability and scapular kinematics in people suffering from chronic neck pain.

Methods: A total of 72 patients with chronic non-specific neck pain were randomized into scapular stabilization exercise alone, n = 24, combined (scapular stabilization exercise + CFT), n = 24, and a control group, n = 24. Scapular kinematic and disability were measured at baseline and after the intervention.

Results: Statistically significant differences in neck pain and disability scale (NPAD) were found when the multimodal physiotherapy group including a cognitive functional approach was compared with stabilization exercises group at 6 weeks (effect size (95%CI) = -1.63 (-2.55, -.71); P = 0.019)). Regarding the neck disability index (NDI), a significant between-group difference was observed at six-week (effect size (95%CI) = -2.69 (-3.80, -1.58); P = 0.007), with the superiority of effect in multimodal physiotherapy group. A significant between-group difference was observed in the scapular upward rotation and scapular osterior tilt at 30°, 60°, 90° and 120° of shoulder adduction.

Conclusions: A group-based multimodal rehabilitation program including scapular stabilization exercise plus cognitive functional therapy was superior to group-based stabilization exercises alone for decreasing disability and, improving scapular kinematic in patients with chronic neck pain.