Intra-cellular Staphylococcus aureus alone causes infection in vivo.

Chronic and recurrent bone infections occur frequently but have not been explained. Staphylococcus aureus (S. aureus) is often found among chronic and recurrent infections and may be responsible for such infections. One possible reason is that S. aureus can internalize and survive within host cells and by doing so, S. aureus can evade both host defense mechanisms and most conventional antibiotic treatments. In this study, we hypothesized that intra-cellular S. aureus could induce infections in vivo. Osteoblasts were infected with S. aureus and, after eliminating extra-cellular S. aureus, inoculated into an open fracture rat model. Bacterial cultures and radiographic observations at post-operative day 21 confirmed local bone infections in animals inoculated with intra-cellular S. aureus within osteoblasts alone. We present direct in vivo evidence that intra-cellular S. aureus could be sufficient to induce bone infection in animals; we found that intra-cellular S. aureus inoculation of as low as 102 colony forming units could induce severe bone infections. Our data may suggest that intra-cellular S. aureus can "hide" in host cells during symptom-free periods and, under certain conditions, they may escape and lead to infection recurrence. Intra-cellular S. aureus therefore could play an important role in the pathogenesis of S. aureus infections, especially those chronic and recurrent infections in which disease episodes may be separated by weeks, months, or even years.

Anatomical consideration of vascularized bone graft transfer from the medial calcaneus to the talus.

To investigate the possibility of use of the calcaneal branches of the posterior tibial artery as the pedicle for the vascularized bone graft to the talus, a detailed anatomical study was carried out on 30 fresh cadaver feet. Although there are several branches from the posterior tibial artery to the calcaneus, the largest posterior branch was defined as the main calcaneal branch. We recognized frequently a large branch nourishing the superior part of the calcaneus and named it the superior calcaneal branch. Twenty feet had the superior calcaneal branches. Pedicled bone grafts using the superior calcaneal branch to the postero-medial portion of the talar body were possible in 18 of 20 feet. Pedicled bone grafts using the main calcaneal branches were possible in 9 of 12 feet in which the superior calcaneal branches were not available. Finally, vascularized bone grafts were judged to be feasible in 27 feet (90%).

Anatomical consideration of reverse-flow island flap transfers from the midpalm for finger reconstruction.

Primary soft-tissue coverage for large palmar defects of the fingers is a difficult problem for cases in which homodigital or heterodigital flaps cannot be used. The aim of this study was to explore the vascular and neural anatomy of the midpalmar area to assess the possibility of reverse island flaps from this area. In 24 cadaver hands perfused with a silicone compound, the arterial pattern of the superficial palmar arch and common palmar digital artery was examined. The cutaneous perforating arteries and nerve branches supplying the midpalmar area were dissected, and the number, location, and arterial diameter of these branches were measured. In six other specimens, the common palmar digital artery was injected to determine the skin territory supplied by the artery. The superficial palmar arch contained the three common palmar digital arteries and its terminal branch coursed along the radial margin of the index metacarpus. This terminal branch had three to six cutaneous perforators (diameter range, 0.1 to 0.5 mm) and supplied the radial aspect of the midpalmar area located over the ulnar half of the adductor pollicis muscles. The midpalmar area was divided into two regions-the proximal and distal-according to the vascular distributions. The proximal region contained dense aponeurosis and thin subcutaneous tissue, and the cutaneous perforators were rather sparse (between three and nine) and had a small diameter (0.1 to 0.3 mm). The distal region, which had loose aponeurosis and abundant subcutaneous tissue, had a rich vascular supply from the common and proper digital artery. Perforating arteries of this region coursed frequently in an oblique fashion and the number of perforators (between eight and 15) and their arterial diameters (diameter range, 0.1 to 0.5 mm) were higher than those of the proximal region. The area of skin perfused by the common palmar digital artery was 5 x 3 cm at the distal midpalmar region. There were three to five cutaneous nerve branches from the palmar digital nerve supplying the midpalmar area. From this study, two different reverse flaps were proposed. First, a 5 x 2 cm flap from the distal midpalmar region was elevated on the basis of the common and proper palmar digital artery. Measurement of the rotation arc revealed that the pivot point of this flap was located at the proximal interphalangeal joint level and could cover the finger pulp of the digits. The second flap candidate was that from the radial aspect of the midpalm, which was supplied by the terminal branch of the superficial palmar arch. In studies with cadaver hands, connection of this artery with the deep arterial system enabled this flap to reach the thumb pulp. These flaps may be a useful reconstruction option for significant palmar soft-tissue loss of the fingers.

Aerobic exercise as a countermeasure for microgravity-induced bone loss and muscle atrophy in a rat hindlimb suspension model.

BACKGROUND: Loss of bone and skeletal muscle atrophy resulting from non-weight-bearing are major concerns associated with microgravity environment and spaceflight deconditioning. The objective of this research was to address the fundamental issue of whether bone loss and muscle atrophy could be attenuated using weight-bearing aerobic exercise on a treadmill as a countermeasure in rats subjected to simulated weightlessness by hindlimb suspension. METHOD: Bone and muscle from control and hindlimb-suspended groups with and without exercise were evaluated by bone mineral density (BMD), mechanical tests, bone histomorphometry and muscle mass. RESULTS: Femoral BMD of hindlimb-suspended (HS) rats subjected to treadmill exercise was significantly greater than femoral BMD of HS rats without exercise and also was equivalent to that of weight-bearing controls. Muscle mass from HS rats exercised on a treadmill was significantly greater than muscle mass from HS rats that did not exercise. Exercise did not result in muscle mass equal to that of controls, however. In addition, histomorphometric analysis of the metaphysis of the proximal tibia revealed that HS rats that exercised did not maintain bone formation equivalent to controls. No other bone parameters were found to vary significantly between groups. CONCLUSIONS: It was concluded that moderate aerobic exercise on a treadmill did attenuate bone loss and muscle atrophy due to simulated weightlessness by hindlimb suspension, however its effectiveness differed by tissue, anatomical site and parameter investigated.

Effect of clamp versus anastomotic-induced ischemia on critical ischemic time and survival of rat epigastric fasciocutaneous flap.

BACKGROUND: There are many models used to explore ischemic-related phenomena. The rat epigastric fasciocutaneous flap model is the one most commonly used. Critical ischemic time is the maximum ischemic insult that tissue can undergo and still remain viable. Experimentally, ischemia is induced either by clamping the vascular pedicle or by dividing the pedicle then performing microvascular arterial and venous anastomosis. We sought to determine what effect the different methods of inducing ischemia have on the critical primary ischemic time and, thus, flap survival. METHODS: A right 3 cm x 6 cm groin flap based on the inferior epigastric vessels was raised in each rat. Ischemic times of 4, 6, 8, or 10 hours were induced either by placing temporary occlusion clamps on each vessel of the vascular pedicle (island pedicle group) or by ligation and division of the pedicle with subsequent microvascular anastomosis (free flap group). Survival was assessed at 7 days. RESULTS: The primary ischemic time at which one half of free flaps are predicted to die was calculated to be 7.60 hours, compared with 6.09 hours for the island pedicle flaps (p<.05). CONCLUSIONS: Fasciocutaneous flaps undergoing ligation and anastomosis are more resistant to ischemia than are those undergoing clamping of the pedicle. Possible etiologic factors responsible for this experimental finding are discussed.