Medical Additive Manufacturing: From a Frontier Technology to the Research and Development of Products

1.Research and development(R&D)and the challenges of raw materials for medical additive manufacturing Raw materials for medical additive manufacturing have a wide range of commonalities that are also seen in many other fields,making them an important basis in the field of three-dimensional(3D)printing.Problems and challenges related to material types,powder properties,formability,viscoelasticity,and so forth also share common features.For example,many metal materials are used in the field of aviation,while metals,polymers,and inorganic materials are used in the field of biomedicine.The most widely used materials in biomedicine are biocompatible.Various homogeneous and non-homogeneous composites are also available for 3D printing,and impose an additional challenge in additive manufacturing;the use of heterogeneous composites in 3D printing is particularly challenging.

Sport medicine among the past three decades in China

In 1955,Professor Mianyu Qu,the founder of Chinese sports medicine,and the older generation of sports medicine practitioners,founded China’s sports medicine in response to the needs of the development of national sports and health.In therst 30 years of the establishment of sports medicine,they played an important role in the academic development,talent cultivation,international communication,construction of the society and organization,national Olympic glory,and nationaltness.Their contributions established a solid foundation for the rapid development of China’s sports medicine in the following 30 years.

Effects of visual restoration on gait performance and kinematics of lower extremities in patients with age-related cataract

Background:Visual inputs are critical for locomotor navigation and sensorimotor integration in the elderly;however,the mechanism needs to be explored intensively.The present study assessed the gait pattern after cataract surgery to investigate the effects of visual restoration on locomotion.Methods:The prospective study recruited 32 patients(70.1±5.2 years)with bilateral age-related cataracts in the Department of Ophthalmology at Peking University Third Hospital from October 2016 to December 2019.The temporal-spatial gait parameters and kinematic parameters were measured by the Footscan system and inertial measurement units.Paired t-test was employed to compare data normally distributed and Wilcoxon rank-sum test for non-normally distributed.Results:After visual restoration,the walking speed increased by 9.3%(1.19±0.40 m/s vs.1.09±0.34 m/s,P=0.008)and exhibited an efficient gait pattern with significant decrease in gait cycle(1.02±0.08 s vs.1.04±0.07 s,P=0.012),stance time(0.66±0.06 s vs.0.68±0.06 s,P=0.045),and single support time(0.36±0.03 s vs.0.37±0.02 s,P=0.011).High amplitude of joint motion was detected in the sagittal plane in the left hip(37.6°±5.3°vs.35.5°±6.2°,P=0.014),left thigh(38.0°±5.2°vs.36.4°±5.8°,P=0.026),left shank(71.9°±5.7°vs.70.1°±5.6°,P=0.031),and right knee(59.1°±4.8°vs.56.4°±4.8°,P=0.001).The motor symmetry of thigh improved from 8.35±5.30%to 6.30±4.73%(P=0.042).Conclusions:The accelerated gait in response to visual restoration is characterized by decreased stance time and increased range of joint motion.Training programs for improving muscle strength of lower extremities might be helpful to facilitate the adaptation to these changes in gait.

Cryo-self-assembled silk fibroin sponge as a biodegradable platform for enzyme-responsive delivery of exosomes

Although advances in protein assembly preparation have provided a new platform for drug delivery during tissue engineering,achieving long-term controlled exosome delivery remains a significant challenge.Diffusion-dominated exosome release using protein hydrogels results in burst release of exosomes.Here,a fibroin-based cryo-sponge was developed to provide controlled exosome release.Fibroin chains can self-assemble into silk I structures under ice-cold conditions when annealed above the glass transition temperature.Exosome release is enzyme-responsive,with rates primarily determined by enzymatic degradation of the scaffolds.In vivo experiments have demonstrated that exosomes remain in undigested sponge material for two months,superior to their retention in fibrin glue,a commonly used biomaterial in clinical practice.Fibroin cryo-sponges were implanted subcutaneously in nude mice.The exosome-containing sponge group exhibited better neovascularization and tissue ingrowth effects,demonstrating the efficacy of this exosome-encapsulating strategy by realizing sustained release and maintaining exosome bioactivity.These silk fibroin cryo-sponges containing exosomes provide a new platform for future studies of exosome therapy.

Posterior hip capsular tenderness test improved the sensitivity and positive predictive value of FADIR test in diagnosing femoroacetabular impingement

To the Editor:Many physical examination tests are used to diagnose femoroacetabular impingement(FAI).The sensitivity and specificity of the flexion,abduction,and external rotation(FABER)test and the flexion,adduction,and internal rotation(FADIR)test for FAI diagnosis are quite different.Therefore,based on clinical practice,we proposed the possibility of adding a physical examination test to improve the accuracy of the traditional physical examinations.

SEMG-based fighter pilot muscle fatigue analysis and operation performance research

Fatigue has a tremendously adverse impact on pilot performance.This study aims to explore the Biceps Brachii(BB),Rectus Femoris(RF),Flexor Carpi Radialis(FCR),and Tibialis Anterior(TA)activities of fighter pilots in the early and late combat stages,and the target hitting time.A total of 13 volunteers were recruited to conduct simulated combats inside a real fighter cockpit.The surface Electromyography(sEMG)was collected from all volunteers in the initial and final 20s of flight,and the target hitting time during three simulated combats was recorded.The root mean square(RMS)values of right BB and TA were significantly higher than the left side values(p<0.001),while insignificant differences were found in the RMS values between the bilateral RF and FCR.Compared to the early flight period,the median frequency(MF)values of BB and TA were significantly lower during the late flight period,and the RMS values were significantly higher(p<0.047).Contrastively,the RMS values of FCR and RF differed insignificantly during the late flight period.Regarding the target hitting time,a significant difference was noted between task 1 and rask3.Subjects exhibit varying levels of muscle fatigue for different muscle groups before and after the flight.The muscle fatigue levels are asymmetrical on the left and right sides.Muscle fatigue might reduce the pilots'operational ability.This study provides a reference for fighter pilot fatigue protection and treatment.