Tsao A

Comparison of Two Different Fixation Techniques for a Segmental Defect in a Rat Femur Model

Studies have attempted to identify the osteogenic effects of bone morphogenetic proteins using a rat femur model, which commonly involves the creation of a critical size defect followed by internal fixation of the femur. Among the most familiar fixation methods are either plating or intramedullary placement of a Kirschner wire (K-wire). There are advantages and disadvantages to each method; however, this study attempts to identify the best method by exploring the histological effects of each technique. The experiment involved two groups with no added treatment: Group P (plate fixation method) and Group K (K-wire fixation method). The animals were allowed a 4-week interval for the femurs to heal, and proximal, distal, and two midshaft cuts were examined under high-power microscopy after the fixation apparatus was removed. Group K exhibited a peculiar fibrotic healing pattern that followed the shaft of the then vacated K-wire and there was minimal new viable bone formation. Group P, however, exhibited a more natural ingrowth of newly formed bone that began at the proximal and distal cuts and proceeded centrally into the core of the defect. Due to the fibrotic tissue in Group K, this study shows that the model is insufficient due to the micromotion created and thus supports plating of critical defects as the fixation method of choice due to the creation of a stable healing environment.

Analysis Of Tissues Collected During Primary And Revision Hip Arthroplasty

that when foreign introduced into a host a sequence of biologicdl owing the marerial to become thin the tissues. The reactive form between the implant and bone an lead to late aseptic loosening. This type of loosening is implicated to be the most a m o n reason for implant failure. It is beIieved that more mature aseptic loosening involves abnormaI and even normal mechanical suesses can Iead to the production of m pic wear particles. Submicron wear p can either be trapped within the joint or to adjacent tissues where they can init de of inflammatory reactions that allow for the recruitment of M a , lymphs and with time a fibrous ,“doma like tissue will develop around the implant. The cell types found at the interface are capable of secreting bone-resorbing cytokines. Ln addition to the osteouophic factors (cytokines), biologicd oxidation of tissues has also been reco,onized as a primary event in the pad.lo,oenesis of many diseases. Reactive ies of O._ and hydroxyl radicals (OH? ar rmed within norma1 biologica1 tissues and propagate along the ’ phospholipid membranes which can cause dative damage of tissues. n e goal ‘of this ine the levels of cytokines and e herface tiSsues reuieved ,

Detection of nonspecific immunohistochemical response caused by tissue necrosis and the presence of metallic wear debris

Tissues retrieved during revision arthroplasty (n=25) were processed for routine immunohistochemical techniques to localize the presence of bone resorbing cytokines (IL-1 and IL-6), and to identify areas of significant necrosis and metallic deposition. Tissues were processed and embedded according to standard laboratory techniques. Several slides were prepared for each tissue sample taken. Several sequential slides were stained for Hematoxylin and Eosin to demonstrate cell type. Other slides of the same tissues were processed for localization of cytokines, IL-1 and IL-6. To identify specific cytokine reactions, the tissues were first blocked with proteins to ensure that all. The results revealed that there were several locations on the tissues that appeared highly reactive for cytokines IL-1 and IL-6. However, some of these areas turned out to be nonspecific when compared with negative controls and the Hematoxylin and Eosin stained slides. Areas of extreme necrosis or where metal debris was presence demonstrated sites of nonspecific reactivity. Areas of necrosis have a high nonspecific affinity for antibodies and these areas of necrosis can be demonstrated on the Hematoxylin and Eosin sections, and should be avoided in determining the amount of specific cellular reactivity. In addition, new immunohistochemical techniques use cobalt ions as enhancers of peroxidase response, in areas on slides labeled as negative controls where metallic debris was trapped, there was an increase in nonspecific positive reactivity. These factors must be carefully controlled in determining true cellular responses that causes resorption of bone and implant failure.

Maintenance of prostatic function by means of exogenous sustained delivery of testosterone in castrated male rats

The objective of this study was to evaluate the effect of various dosages of testosterone (T) delivered in a sustained manner by means of a tricalcium phosphate-lysine (TCPL) delivery system on morphological changes of prostatic tissue using adult male rats as a model. In this experiment, adult male rats (250-300 g BW) were randomly divided into five equal groups (n=8). Rats in group I, II, and III were implanted subcutaneously with TCPL loaded with three different dosages (10, 100 and 200 mg, respectively) of T. Rats in group IV were implanted with sham TCPL capsules, and rats in group V served as intact unimplanted controls. At the end of 8 weeks post implantation, all animals were sacrificed and the prostate tissues were collected, weighted, and embedded for histo-pathological evaluations. Data collected from this study have shown that exogenous intake of T delivered in a sustained manner for eight weeks induced several pathophysiological conditions in ventral prostatic tissue in comparison to the control and sham operated groups. This phenomenon was found to be directly proportional to the dose or the level of sustained delivery. The results demonstrated that the use of 10 mg filled TCPL implants decreased the total mass weight of ventral prostate. Light microscopic evaluation of this group (Group I) revealed a cellular adaptation through an atrophy in the epithelium component. Cytopathological observations such as low cuboidal and thin glands, pleomorphism, and occasional presence of connective tissue stroma were detected. In contrast, ventral prostate collected from animals implanted with TCPL filled with 200 mg T (Group III) showed a significant increase in weights of the wet prostatic tissues in comparison to all groups. Histopathological evaluations demonstrated the following: (i) prostatic hypertrophy alone, or in conjunction with hyperplasia of the epithelial cells, (ii) less connective tissue stroma in comparison to the control group, (iii) occasional involvement of mitotic figures, and (iv) increased angiogenesis. No significant change was observed in those animals implanted with TCPL capsules containing 100 mg T compared to the intact control animals.