The pace of modern life, revisited.

Wild populations must continuously respond to environmental changes or they risk extinction. Those responses can be measured as phenotypic rates of change, which can allow us to predict contemporary adaptive responses, some of which are evolutionary. About two decades ago, a database of phenotypic rates of change in wild populations was compiled. Since then, researchers have used (and expanded) this database to examine phenotypic responses to specific types of human disturbance. Here, we update the database by adding 5675 new estimates of phenotypic change. Using this newer version of the data base, now containing 7338 estimates of phenotypic change, we revisit the conclusions of four published articles. We then synthesize the expanded database to compare rates of change across different types of human disturbance. Analyses of this expanded database suggest that: (i) a small absolute difference in rates of change exists between human disturbed and natural populations, (ii) harvesting by humans results in higher rates of change than other types of disturbance, (iii) introduced populations have increased rates of change, and (iv) body size does not increase through time. Thus, findings from earlier analyses have largely held-up in analyses of our new database that encompass a much larger breadth of species, traits, and human disturbances. Lastly, we use new analyses to explore how various types of human disturbances affect rates of phenotypic change, and we call for this database to serve as a steppingstone for further analyses to understand patterns of contemporary phenotypic change.

A Recurrent Stress Fracture of the Humerus following Fixation: The Effect of Implant Stress Shielding.

INTRODUCTION: Non-traumatic stress fractures of the humerus are often related to a throwing motion. This type of humeral fracture is often due to uncoordinated muscular activity on the humeral shaft. These forces over time may contribute to mid-shaft humeral stress fractures, an injury often referred to as a "throwers fracture." The ultimate strength of bone is decreased when a screw hole is created, as in open reduction and internal fixation repairs (ORIF). CASE REPORT: This case study discusses a patient who underwent plate and screw fixation of a previous stress fracture of the humerus. He continued to remain active and competitive in collegiate baseball, playing the catcher position which leads to a recurrent stress fracture. A combination of low Vitamin D and stress-shielded bone likely resulted in the reinjury. Physicians treating patients with these injuries should be aware of the possibility of refracture if inciting factors are not modified. This case of a non-traumatic humeral shaft stress refracture, following ORIF, has not been described in the literature. CONCLUSION: The unusual case of a humeral stress refracture following ORIF is presented. A combination of low Vitamin D and stress-shielded bone likely resulted in the reinjury. Physicians treating patients with these injuries should be aware of the possibility of refracture if inciting factors are not modified.

Corrosion and Tribology of Materials Used in a Novel Reverse Hip Replacement.

Total hip arthroplasty has been utilized for the past 50 years as an effective treatment for degenerative, inflammatory and traumatic disorders of the hip. The design of these implants has generally followed the anatomy of the hip as a ball and socket joint with the femoral head representing the ball and the acetabulum representing the socket. We describe a novel hip arthroplasty design in which the "ball" is located on the acetabular side and the "socket" is located on the femoral side. The results of extensive biomechanical testing are described and document wear and corrosion characteristics that are at least equivalent to standard designs. These results support clinical assessment as the next step of the evaluation.

Biomechanics of Fractures.

BACKGROUND: This video presents the digitized, original, reel-to-reel footage of Victor Frankel's groundbreaking 1960s experiments demonstrating the viscoelastic properties and fracture mechanics of loaded bone. As can be seen, novel instrumentation was used that resulted in an easily reproducible method of controlling bone loading rates. The innovation, and associated experiments, radically advanced our understanding of the mechanisms of acute fractures and bone's response to energy. METHODS: Using the "Standard Torsion Testing Machine" that he helped design, the author explains how the mechanical and functional properties of bone are affected by various defects. Examples used include an intact dog femur, a femur with a hole in the cortex, and a femur with an open section defect. Slow motion depiction allows the viewer to appreciate the potential soft tissue damage associated with bone fragmentation and how this varies with energy input. The video concludes with a demonstration of the effect of torsional motion on the vasculature. RESULTS: Graphs produced by the torsion tester display torque versus angular deformation plots for each experiment. These illustrate the relationship between bone structure, fracture, and energy. The x-ray contrast segment provides an example of associated arterial damage secondary to a fracture. CONCLUSION: This previously unreleased piece of orthopaedic history provides viewers with perspective on the early days of biomechanical study and an easy-to-understand tutorial on acute fracture mechanics and the role of energy in injury.

Host preference of an introduced 'generalist' parasite for a non-native host.

Parasites can invade new ecosystems if they are introduced with their native hosts or if they successfully infect and colonise new hosts upon arrival. Here, we ask to what extent an introduced parasite demonstrates specialisation among novel host species. Infection surveys across three field sites in Gatun Lake, Panama, revealed that the invasive peacock bass, Cichla monoculus, was more commonly infected by the introduced trematode parasite Centrocestus formosanus than were three other common cichlid fishes. Laboratory infection experiments were conducted to determine whether parasitism might be driven by differential encounter/exposure to parasites or by differential infection susceptibility/preference across different host species. These experiments were performed by controlling for parasite exposure in single host (compatibility) experiments and in mixed host (preference) experiments. In all cases, the peacock bass exhibited higher infection rates with viable metacercariae relative to the other potential fish hosts. Our experiments thus support that an introduced generalist parasite shows apparent specialisation on a specific novel host. Further studies are needed to determine whether these patterns of specialisation are the result of local adaptation following invasion by the parasite.

Effects of aging on Type II muscle fibers: a systematic review of the literature.

The authors conducted a systematic review of the literature for scientific articles in selected databases to determine the effects of aging on Type II muscle fibers in human skeletal muscles. They found that aging of Type II muscle fibers is primarily associated with a loss of fibers and a decrease in fiber size. Morphological changes with increasing age particularly included Type II fiber grouping. There is conflicting evidence regarding the change of proportion of Type II fibers. Type II muscle fibers seem to play an important role in the aging process of human skeletal muscles. According to this literature review, loss of fibers, decrease in size, and fiber-type grouping represent major quantitative changes. Because the process of aging involves various complex phenomena such as fiber-type coexpression, however, it seems difficult to assign those changes solely to a specific fiber type.

Calf muscle pump stimulation as an adjunct to orthopaedic surgery.

Management of patients following extensive orthopaedic surgery, and in particular, joint replacement surgery, represents a continuing challenge. The associated bed rest burdens a broad range of physiologic functions, exacerbating vascular, venous, and lymphatic conditions, as well as cardiovascular conditions and glucose regulation in the hyperglycemic or diabetic patient. Most of these problems arise from a lack of mobility/exercise during recuperation. In a recent series of clinical studies, non-invasive micromechanical stimulation (MMS) of the plantar surface has been demonstrated to significantly enhance skeletal muscle pump activity in the lower limbs of patients, which results in improved blood and lymphatic flow in the lower body. These studies demonstrate efficacy in both the supine and upright positions, suggesting the potential of MMS technology to significantly improve post-surgical patient care. Moreover, evidence is increasing that sustained skeletal muscle pump activity helps to maintain normal fluid flow in bone tissue, such that MMS may provide a non-drug treatment for maintaining bone mass during bed rest, or possibly increasing bone mass following extended bed rest.

Development and testing of a novel biosynthesized XCell for treating chronic wounds.

Biosynthesized cellulose is produced by the bacteria, Acetobacter xylinum, and possesses unique properties not present in other biomaterials. The material is formed during fermentation having a multi-layered structure composed of fine, nonwoven, cellulose hydrophilic fibers. This structure allows biosynthesized cellulose to have a high-fluid capacity, superior strength, and biocompatibility, which makes it suitable for topical and implantable biomedical applications. Initial product development of biosynthesized cellulose has focused on advanced wound-care applications. The product, XCell (Xylos Corporation, Langhorne, PA, USA), has been bioengineered to have the ability to both donate and absorb moisture, depending on the wound environment. Comparative bench testing has shown that XCell is the only wound dressing with this unique dual-fluid-handling capability. The product has been studied thoroughly using animal models and proved to be safe and biocompatible. Human clinical testing has demonstrated its effectiveness in providing a moist environment, essential to treating hard-to-heal chronic wounds. The major clinical benefits of the product include: 1) help in removal of non-viable tissue and promotion of autolytic debridement, which results in increased granulation tissue; 2) cleansing of wound margins that leads to epithelial migration and reduction of wound size; and 3) healing of various types of chronic wounds.

Management of non-union with pulsed low-intensity ultrasound therapy--international results.

In prospective, randomized, double-blind, placebo-controlled, multi-center clinical studies, pulsed, low-intensity ultrasound has been proven to be effective in decreasing the time to heal in both fresh diaphyseal (tibia) and metaphyseal (distal radius) fractures. It also decreases the likelihood of a delayed union (>150 days to heal) in tibia fractures and loss of reduction in distal radius fractures. World-wide clinical studies, using pulsed, low-intensity ultrasound for treatment of non-union in a self-paired control study design, have demonstrated a heal rate of 88% with an average treatment time of 4.5 months in non-unions and an average fracture age of 23 months. The therapy is safe and non-invasive, and is used by the patient at home for a 20-minute treatment session per day.