“四个自由度肌电控制全臂假肢”肩关节机构的设计

全臂假肢肩关节结构，不但要符合人手臂的外形特征，而且在结构设计的布局上还要考虑仿生性和造型的美观逼真。由于在肩关节处要承受相当大的力矩，肩关节机构要经得起前臂的较大负载外力，所以功能可靠更为重要。因此关肩节机构的 设计具有相当的难度。本机构利用蜗轮蜗杆传动的优点，来实现肩关节前屈后伸运动。克服了链传间隙大的缺点，缩短了力臂改善了肩关节处的受力状态，并且在假肢的上臂安装了上臂手动旋转环，其既可在任意     

Morphology and function of the shoulder joint of bats (Mammalia: Chiroptera)1

The shoulder joint of the Microchiroptera shows a remarkable morphological variation that has been studied in 20 individual bats from 15 species and 11 families. The basic morphology of the shoulder joint, with a globular humeral head and a corresponding glenoid cavity, is found in the Megachiroptera and, within the Microchiroptera, in the Rhinopomatidae. Besides this basic shoulder joint, there are two derived joint types: the derived and specialized shoulder joint with a single articular surface on the scapula and a more-or-less oblong humeral head, and the derived and specialized shoulder joint with secondary articular surfaces on the trochiter and on the dorsal aspect of the scapula. The first type of derived joint is most strikingly developed in the Mormoopidae and the Noctilionidae, the second one in the Vespertilionidae and the Molossidae. It is suggested that both types of derived shoulder joints have the functional significance of reducing the pronatory movements of the abducted forearm during the downstroke of the wing-beat cycle. This suggested function of the secondary shoulder joint is a new approach to understanding this very peculiar structure. In species with these specialized shoulder joints, the downstroke musculature is comparatively better developed and the M. serratus ant. post. div. comparatively less well developed. A hypothesis is offered to explain and combine the osteological and myological findings. Each of the derived types of shoulder joints has developed independently more than once through parallel evolution.     

Tooth chipping patterns in Archaeolemur provide insight into diet and behavior

Objectives

Archaeolemur is a recently extinct genus of lemur that is often compared to some Cercopithecidae, especially baboons. This is due in part to their derived dentition, with large anterior teeth and reduced bilophodont molars. Research involving comparative morphology, analysis of coprolites, isotopes, and enamel structure, have suggested Archaeolemur had an omnivorous diet involving mechanically challenging items. Yet, microwear analysis of posterior teeth does not necessarily support this conclusion.

Materials and Methods

In this macroscopic study, dental chipping was recorded on permanent teeth of Archaeolemur from different localities (53 individuals; 447 permanent teeth; including both A. edwardsi and A. majori specimens). This study aimed to compare chipping patterns across the dentition of Archaeolemur with chipping in other primates.

Results

The results show enamel chipping was prevalent on the anterior teeth of Archaeolemur (38.9% of anterior teeth showed at least one fracture) yet rare in posterior teeth (9%). There was a decrease in chipping frequency across the dentition, moving distally from incisors (50%; 20/40), through caniniform teeth (30%; 15/50), premolars (9.5%; 16/169), and molars (8.5%; 16/188).

Discussion

The results support previous research suggesting Archaeolemur had a varied omnivorous diet in which the anterior dentition was used for extensive food processing. This likely included mechanically challenging items such as tough/hard large fruits, small vertebrates, and crustaceans. Such a high rate of chipping in the anterior dentition is uncommon in other primates, with exception of hominins.

     

Muscular fatigue during repeated isokinetic shoulder forward flexions in young females

Peak torque, work, mean power and electromyographic (EMG) activity were recorded for each of 150 repeated isokinetic maximal shoulder flexions (45 degrees-90 degrees) in 23 healthy females. From the EMG signals of trapezius, deltoid, infraspinatus and biceps brachii the mean power frequency and the signal amplitude were determined in real time. The mechanical output showed a steep decrease during the first 40 contractions, followed by a plateau maintained until the end. In all muscles, except the biceps brachii, significant decreases in mean power frequency occurred during the first 40 contractions, showing a tendency to stabilize around the same absolute frequency value. Signal amplitude increased in the trapezius, the deltoid and the infraspinatus, but was constant in the biceps brachii. For some individuals rather high EMG activity was recorded in the muscles during the time the arm was supposed to be passively extended to the starting position, and this was found to be associated with lower strength and endurance levels. Longitudinal analyses showed that the mean power frequencies correlated better than the signal amplitudes with the three mechanical variables. The results suggest that the initial steep decrease in mechanical performance and mean power frequency is caused by fatiguing of type 2 motor units.     

In vivo measurement of shoulder joint loads during activities of daily living

Until recently the contact loads acting in the glenohumeral joint have been calculated using musculoskeletal models or measured in vitro. Now, contact forces and moments are measured in vivo using telemeterized shoulder implants. Mean total contact forces from four patients during eight activities of daily living are reported here.Lifting a coffee pot (1.5 kg) with straight arm caused an average force of 105.0%BW (%body weight) (range: 90–124.6%BW), while setting down the coffee pot in the same position led to higher forces of 122.9%BW on the average (105.3–153.4%BW). The highest joint contact forces were measured when the straight arm was abducted or elevated by 90° or more, with a weight in the hand. Lifting up 2 kg from a board up to head height caused a contact force of 98.3%BW (93–103.6%BW); again, setting it down on the board led to higher forces of 131.5%BW (118.8–144.1%BW). In contrast to previously calculated high loads, the contact force during passive holding of a 10 kg weight laterally was only 12.3%BW (9.2–17.9%BW), but when lifting it up to belt height it increased to 91.5%BW (87–95%BW).The moments transferred inside the joint at our patients varied much more than did the forces both inter and intra-individually.Our data suggest that patients with shoulder problems or during the first post-operative weeks after shoulder fractures or joint replacements should avoid certain activities encountered during daily living e.g. lifting or holding a weight with an outstretched arm. Some energy-related optimization criteria used in the literature for analytical musculoskeletal shoulder models must now be reconsidered.     

The Risk Factors for Developing Clustered Vertebral Compression Fractures: A Single-Center Study

ObjectiveVertebral compression fractures (VCFs) are common among elderly individuals, but clustered VCFs (C-VCFs) are rare and more severe. The risk factors for C-VCFs remain unclear. Thus, we investigated the clinical characteristics of C-VCFs to identify the imminent fracture risk and improve the treatment for such patients.MethodsWe reviewed the records of patients with VCF at a single medical center between January 2011 and September 2020. Patients who had 4 or more VCFs within 1 year were categorized into the C-VCF group, and the remaining patients were paired into the control group at a ratio of 2:1. We collected demographic, clinical, laboratory, and radiologic information regarding these patients. Univariate analyses, stratified analyses, and multivariate logistic regression were performed to identify the risk factors for C-VCFs.ResultsA total of 156 patients were enrolled, of whom 52 were patients with C-VCF. Patients with C-VCF had more severe fractures and pain, with fractures occurring at uncommon sites of the spine. The independent risk factors for C-VCFs included glucocorticoid (GC) treatment (P < .001; hazard ratio [HR], 12.7), recent fracture history (P = .021; HR, 5.5), and lower trabecular bone score (TBS) (P = .044; HR, 1.6). TBS and bone mineral density had greater predictive values in patients without GC treatment (P < .001). Sex, age, and bone turnover biomarkers were not independent risk factors for C-VCFs.ConclusionC-VCFs are rare adverse consequences of severe osteoporosis, for which GC treatment, recent fracture history, and lower TBS are unique risk factors that are valuable for the early identification and prevention of C-VCFs.     

Intramuscular pressure and muscle blood flow in supraspinatus

Intramuscular pressure and muscle blood flow was measured in the supraspinatus muscle in 6 healthy subjects. The recordings were performed at rest, during isometric exercise, during an isometric muscle contraction of 5.6 kPa (42 mm Hg) and 10.4 kPa (78 mm Hg) and at rest after the contraction. Intramuscular pressure was measured by the microcapillary infusion technique, and muscle blood flow by the Xenon-133 washout technique. Intramuscular pressure was 38.2 kPa (SD 12.0) (287 mm Hg) during maximal voluntary contraction. A muscle contraction pressure of 5.6 kPa (42 mm Hg), which is 16% of maximal voluntary contraction, reduces local muscle blood flow significantly. It is concluded that the high intramuscular pressures found in supraspinatus during work with the arms elevated impedes local muscle blood flow.     

Trauma among early Californians

The incidence and distribution of trauma is examined in a large number of individuals from many burial sites in California. The material represents part of an on-going curational effort at the Lowie Museum of Anthropology. Trauma is confined to fractures, dislocations, and projectile wounds for the purposes of this study. Only antemortem fractures are considered. The findings suggest that most fracture were due to accidents, though several parry fractures are present. The functional results of healing do not warrant any conclusions as to the efficacy of treatment or lack thereof. Several projectile wounds are seen, some with evidence of healing. Presented in part at the 55th annual meeting of the American Association of Physical Anthropologists, Albuquerque, New Mexico, April 1986.