In vivo evaluation of the effects of gravitational force (+Gz) on over-the-wire stainless steel Greenfield inferior vena cava filter in swine.

This study was done to determine the effect of exposure to gravitational force (acceleration stress) on in vivo over-the-wire stainless steel Greenfield inferior vena cava filters. Fifteen pigs underwent venous cut down and placement of a stainless steel Greenfield filter. A 4-week observation period simulated realistic convalescence and allowed sufficient time for epithelialization. Ten pigs were exposed to acceleration stress in a centrifuge (3G run for 15 sec followed by rest until return to baseline heart rate, then a 9G run for 15 sec), with inertial loading in a head-to-tail direction (+Gz). Fluoroscopy during acceleration stress allowed assessment for filter migration. Five pigs were not exposed to acceleration stress. AP and lateral abdominal radiographs were obtained at post-filter placement, convalescence, and centrifuge exposure to determine the position and integrity of the filter. All 15 IVCs were resected and evaluated for gross or histological injury to the vessel wall. IVC filter placement was technically successful in all 15 pigs. Radiographic measurements were limited secondary to differences in pig positioning. Fluoroscopy showed no filter migration. All filters were securely attached to the vena cava by the hooks without gross evidence of perforation or hemorrhage. There were varying degrees of fibroplasia involving the hooks and tip of the filters in both the control and experimental groups. Histologically, there was evidence of prior hemorrhage at the level of the hooks, which was similar between the control and experimental groups. It is concluded that Greenfield filter position and vena caval integrity at the implantation site is unaffected by high acceleration stress.

Evaluation of multiphase implants for repair of focal osteochondral defects in goats.

The use of biodegradable scaffolds for articular cartilage repair has been investigated by numerous researchers. The objective of this screening study was to examine how the mechanical and physical properties of four multiphase implants can affect the cartilage healing response. Multiphase implant prototypes were prepared using poly(D,L)lactide-co-glycolide as the base material. PGA fibers (FR), 45S5 Bioglass (BG) and medical grade calcium sulfate (MGCS) were used as additives to vary stiffness and chemical properties. Osteochondral defects (3 mm dia. and 4 mm in depth) were created bilaterally in the medial femoral condyle (high-weight bearing) and the distal medial portion of the patellar groove (low-weight bearing) of 16 Spanish goats. Half of the implants were loaded with autologous costochondral chondrocytes. Defect sites (total n = 64, 4 sites/treatment) were randomly treated and allowed to heal for 16 weeks, fully weight bearing. At euthanasia, gross evaluations and biomechanical testing were conducted. Histological sections of the defect sites were stained with H and E, Safranin O/Fast Green or processed to analyze collagen architecture. Sections were semi-quantitatively scored for repair tissue structure. Qualitative evaluations showed that all groups had a high percentage of hyaline cartilage and good bony restoration, with new tissue integrating well with the native cartilage. Gross and histology scoring indicated a significantly higher score for defect healing in the condyle than in the patellar groove, but no difference in healing for implant types or addition/omission of cells was found. This investigation demonstrates that focal, osteochondral defects in caprine distal femurs treated with various implant constructs were repaired with hyaline-like cartilage and good underlying bone. The multiphase implants show potential for treatment of osteochondral defects and long-term studies need to be undertaken to confirm the longevity of the regenerated tissue.

Spontaneous dermatophytosis due to Microsporum canis in rabbits.

Reports of naturally occurring Microsporum canis infection in the rabbit are rare. During the tenth week of a 91 day percutaneous toxicity study, 17 of 30 adult New Zealand white rabbits developed skin lesions varying from multiple papules to ringed lesions 1 X 2 cm in diameter. The lesions were not pruritic. Hair and scale samples taken from rabbits with lesions were cultured for dermatophytes. Based upon colony morphology and macroconidial characteristics, M canis identification was confirmed. At the time of necropsy, fluorescence was observed in three animals examined with a Wood's lamp, and of 10 rabbits that were positive on culture, seven were clinically normal. Microscopically, hair follicles contained spores and mycelia. The source of this outbreak was not determined. Tap water was cultured and found negative for pathogenic fungi. These findings document M canis infections in laboratory-housed New Zealand white rabbit, such an asymptomatic carrier state should be considered in this outbreak. The significance of dermatomycosis in laboratory animals is primarily as a zoonosis and a research complication.