The influence of UKA Installation Error of Joint Line on Contact Mechanics and Kinematics of Knee Joint / 医用生物力学

Objective Aiming at the medial prosthetic loosening failure and lateral cartilage degeneration after unicompartmental knee arthroplasty ( UKA), the effects of prosthetic installation errors of joint line in UKA on knee contact mechanics and kinematics during different physiologic activities were studied using musculoskeletal multi-body dynamic method. Methods Taking the medial natural joint line as 0 mm error, six installation errors ofjoint line including ±2 mm, ±4 mm and ±6 mm were considered respectively, and seven musculoskeletal multi body dynamic models of medial UKA were established, to comparatively study the variations in knee contact mechanics and kinematics during walking and squatting. Results At 70% of walking gait cycle, compared with 0 mm error, the medial prosthetic contact force was increased by 127. 3% and the contact force of the lateral cartilage was decreased by 12. 0% under 2 mm elevation in joint line, the medial prosthetic contact force was close to 0 N, but the lateral cartilage contact forces were increased by 10. 1% under 4 mm reduction in joint line. The tibiofemoral total contact forces were increased by 19. 7% and decreased by 14. 2% under 2 mm elevation and 2 mm reduction in joint line, respectively. At the 100°knee flexion during squatting, compared with 0 mm error, the medial prosthetic contact force and the tibiofemoral total contact force increased by 31. 6% and 11. 1% under 2 mm elevation in joint line, and decreased by 24. 5% and 8. 5% under 2 mm reduction in joint line, respectively. The change in the lateral cartilage contact force was not marked. Moreover, at 70% of walking gait cycle, the varus angle decreased, the internal rotation and the anterior translation increased along with the elevation of joint line in UKA, while it was just the opposite along with the reduction of joint line in UKA. The trends of the varus valgus movement and anterior-posterior translation during squatting were consistent with those during swing phase of walking, but the trend of the internal-external rotation was opposite. Conclusions In order to reduce the risk of medial prosthetic loosening failure and lateral cartilage degeneration, it is recommended that the installation error of joint line in UKA should be controlled in the range of -2 mm to +2 mm. This study provides theoretical basis for UKA clinical failure caused by changes in joint line

Musculoskeletal multibody dynamics investigation for the different medial-lateral installation position of the femoral component in unicompartmental knee arthroplasty / 生物医学工程学杂志

The surgical installation accuracy of the components in unicompartmental knee arthroplasty (UKA) is an important factor affecting the joint function and the implant life. Taking the ratio of the medial-lateral position of the femoral component relative to the tibial insert (a/A) as a parameter, and considering nine installation conditions of the femoral component, this study established the musculoskeletal multibody dynamics models of UKA to simulate the patients' walking gait, and investigated the influences of the medial-lateral installation positions of the femoral component in UKA on the contact force, joint motion and ligament force of the knee joint. The results showed that, with the increase of a/A ratio, the medial contact force of the UKA implant was decreased and the lateral contact force of the cartilage was increased; the varus rotation, external rotation and posterior translation of the knee joint were increased; and the anterior cruciate ligament force, posterior cruciate ligament force and medial collateral ligament force were decreased. The medial-lateral installation positions of the femoral component in UKA had little effect on knee flexion-extension movement and lateral collateral ligament force. When the a/A ratio was less than or equalled to 0.375, the femoral component collided with the tibia. In order to prevent the overload on the medial implant and lateral cartilage, the excessive ligament force, and the collision between the femoral component and the tibia, it is suggested that the a/A ratio should be controlled within the range of 0.427-0.688 when the femoral component is installed in UKA. This study provides a reference for the accurate installation of the femoral component in UKA.

Factores asociados con rigidez de las articulaciones del hombro y la cadera en adultos mayores / Factors associated with stiffness of the shoulder and hips joints in the elderly

Introducción: mantener el nivel adecuado de flexibilidad en la edad adulta es importante para realizar las actividades básicas de la vida diaria; sin embargo, esta puede verse afectada negativamente por distintos factores, como el sedentarismo, la artrosis, la diabetes y el estado emocional. Objetivo: analizar la prevalencia de la rigidez en las articulaciones del hombro y coxofemoral, con factores asociados en los adultos mayores de la ciudad de Cuenca, Ecuador. Metodología: estudio analítico transversal con una muestra de 160 adultos mayores de las residencias geriátricas de la ciudad de Cuenca, Ecuador. La información se recolectó aplicando dos tests que valoran la flexibilidad, incluidos en la batería Senior fitness test (SFT): el Back scratch (TBS) y el test Chair sit and reach (TCSAR), para valorar el grado de rigidez de las articulaciones del hombro y coxofemoral. El nivel de actividad física se evaluó utilizando el test Rapid Assessment of Physical Activity (RAPA), y se utilizaron el test Yesavege para valorar el grado de depresión y la historia clínica de cada paciente, para conocer antecedentes de diabetes mellitus o artrosis. Se analizaron los datos con el programa SPSS versión 20.0®, por medio de medidas de frecuencia, dispersión, análisis bivariado (OR, IC, valor P). Resultados: se evidenció la inactividad física como factor de riesgo importante para padecer rigidez de articulación del hombro p=0,023, articulación coxofemoral p<0,001; además, la artrosis como factor de riesgo para rigidez en miembros superiores. La pre-valencia de rigidez articular fue de 40,6% en miembros inferiores y el 70,6%en los miembros superiores. Conclusión: los hallazgos de esta investigación corroboran que la inactividad física pue-de llevar a la pérdida progresiva de la flexibilidad en adultos mayores, con disminución en el rango de movimiento articular y limitación funcional. (AU)

Introduction: maintaining the appropriate level of flexibility in adulthood is important to carry out the basic activities of daily life; however, this can be negatively affected by different factors, such as a sedentary lifestyle, osteoarthritis, diabetes and emotional state. Objective: to analyze the prevalence of stiffness in the shoulder and coxofemoral joints, with associated factors in older adults in the city of Cuenca, Ecuador. Methodology: cross-sectional analytical study with a sample of 160 older adults from nursing homes in the city of Cuenca. The information was collected by applying two tests that assess flexibility, included in the senior fitness test (SFT) battery: the back scratch (TBS) and the chair sit and reach test (TCSAR), to assess the degree of stiffness of the knee joint. shoulder and coxofemoral. The level of physical activity was evaluated using the Rapid Assessment of Physical Activity (RAPA) test, the Yesavege test was used to assess the degree of depression and the clinical history of each patient to determine a history of diabetes mellitus or osteoarthritis. The data were analyzed with the SPSS version 20.0 program, through measures of frequency, dispersion, and bivariate analysis (OR, CI, P value). Results: physical inactivity was evidenced as an important risk factor for shoulder joint stiffness p=0.023, coxofemoral joint p=<0.001; in addition, osteoarthritis as a risk factor for stiffness in the upper limbs. The prevalence of joint stiffness was 40.6% in the lower limbs and 70.6% in the upper limbs. Conclusion: the findings of this research corroborate that physical inactivity can lead to progressive loss of flexibility in older adults, with decreased range of joint movement and functional limitation. (AU)

EMG characteristics of lower extremities during movement of white crane spreads its wings in Tai Chi Quan / 医用生物力学

Objective To analyze how the athletes control postural balance through observing their joint angular motion change，center of pressure (COP) change and EMG activities of lower extremities for both athletes and beginners when performing the movement of white crane spreads its wings in Tai Chi Quan. Methods Twenty subjects were divided into 2 groups as 10 athletes and 10 beginners of Tai Chi Quan in each. When performing the movement of white crane spreads its wings, their EMG activities of 10 skeletal muscles, two-dimensional angular motion of 3 large joints in bilateral lower extremities, and COP displacements in lateral and anterior-posterior directions were recorded. Each performing trial took 8 seconds and repeated 5 times. All data were statistically processed for EMG, motion and balance analysis, and the EMG data were normalized to compare the differences between the athletes and beginners of Tai Chi Quan. Results The EMG activities of tibialis anterior(Ta), biceps femur(bF), gluteus medium(Gm) in support leg of athletes were significantly greater than those of the ipsilateral muscles in support leg of beginners, and the same was the EMG activities of gastrocnemius (G) and rectus femur（rF) in virtual leg of athletes compared with the beginners. The maximal average angular motion of 3 large joints and the coxa -joint motion of support leg in athletes were both significantly greater than that in beginners, but the anterior-posterior COP displacement in athletes was significantly smaller than that in beginners. Conclusions When performing the movement of white crane spreads its wings in Tai Chi Quan, athletes could oppose the COP change by enhancing muscle activities to maintain the postural balance, while beginners couldn’t make such active muscle activities against the uncontrolled anterior-posterior COP displacement. This may preliminarily explain the reason why Tai Chi Quan exercise can improve the muscle strength in lower extremities and enhance the ability of postural control.

Lower extremity muscle coordination in stroke patients revealed by surface electromyography / 中华物理医学与康复杂志

Objective To explore the changes in muscle activity patterns in the lower leg during ankle dorsiflexion and plantarflexion in stroke patients. Methods Ten recovering stroke patients with hemiparesis(Pa- tient group)and ten age-and sex-matched healthy volunteers(Healthy control group)were studied.The subjects performed ankle dorsiflexion and plantarflexion synchronized with a visual cue while supine.Surface electrodes were applied over the anterior tibialis(TA),caput laterale musculi gastrocnemius(IGM),caput mediale musculi gas-troenemius(mGM)and soleus muscles(SOL)for integrated electromyography(iEMG).Results During ankle dorsiflexion,the TA,lGM,mGM and SOL of the affected side showed a significantly lower iEMG signal than the unaffected side.Activity of the lGM,mGM and SOL of the affected side were significantly lower than in the healthy controls.During ankle plantaflexion,the TA,lGM and mGM on the affected side had significantly lower activity than those of the healthy controls.The mGM of the affected side showed significantly lower muscle activity than the unaffeeted side.The SOL contraction ratio on the affected side was significantly higher than on the unaffected side and in the healthy control group. Conclusion Except for the soleus,there is an obvious decline in muscle activi-ty in the affected lower extremities of stoke patients during ankle dorsiflexion and plantaflexion.The soleus on the affected side becomes the primary plantarflexor in patients with stroke,rather than the caput laterale musculi gas-trocnemius or caput mediale musculi gastroenemius as in healthy subjects.

Electromyogram patterns during ankle joint movements at various angular velocities in the triceps surae muscles / 体力科学

Surface electromyograms (EMGs) were recorded from the triceps surae muscles in order to examine muscle activities during concentric and eccentric ankle joint movements at various angular velocities under constant load (5 and 10%MVC) . The results were summarized as follows ;<BR>1) At slow angular velocity (6 deg/s) of ankle joint movement, EMG amplitude tended to increase at a larger ankle joint angle in the gastrocnemius muscle, and at a smaller angle in the soleus muscle.<BR>2) Following an increase in angular velocities (6→30→60 deg/s), peak values of integrated EMGs were significantly increased (7-15%) in the medial gastrocnemius muscle. However, these peak values were significantly decreased in the soleus muscle (22-49%) . These results suggest selective recruitment of motor units depending on angular velocity.<BR>3) Ankle joint angle at the peak integrated EMGs was significantly increased following an increase in angular velocity (6→30→60 deg/s) in the soleus muscle. This suggests that the angle at the recruitment of motor units may be dependent on angular velocity in the soleus muscle.