ABSTRACT
Bone-methyl methacrylate interfacial shear strength at failure in chronically implanted hip prostheses was studied. Gorman total hip prostheses fixed with methyl methacrylate bone cement were implanted in 6 large dogs. Interface shear strength studies were performed at 8, 16, and 24 weeks. Mechanical testing determined that the mean interfacial shear strength was 15.2 +/- 13.0 kg/cm2. Variability of the data was too great to allow conclusions to be drawn from statistical analysis, but trends in the data were observed. It was concluded that the interfacial bond had sufficient strength to withstand axial loads 3 to 6 times greater than those applied under normal physiologic conditions.
Subject(s)
Bone Cements , Dogs/surgery , Joint Prosthesis/veterinary , Methylmethacrylates , Animals , Biomechanical Phenomena , Femur/physiology , Hip Joint , Stress, MechanicalABSTRACT
Cardiac output function curves were used to investigate the effects of carbon monoxide on the heart in the conscious dog. Each dog was briefly exposed to 1,500 ppm carbon monoxide through a permanent tracheostomy. Immediately upon attaining either 10%, 20%, or 30% HbCO a rapid infusion of Ringer's lactate was given to test cardiac capabilities. The combined effects of carbon monoxide and infusion produced significant increases in cardiac output, heart rate, mean left ventricular pressure, dP/dt and (dP/dt)/IP. Cardiac output was sufficient to prevent peripheral hypoxia at all HbCO levels; however, there was evidence of impending cardiac depression beginning at 20% HbCO.
Subject(s)
Carbon Monoxide Poisoning/physiopathology , Heart/physiopathology , Animals , Blood Pressure , Cardiac Output , Dogs , Heart Rate , Heart Ventricles/physiopathology , RespirationABSTRACT
The second lumbar vertebra was surgically removed from 10 dogs, and the shortened vertebral column was stabilized by internal fixation with two types of plastic plates. Shortening of the spinal column was usually not associated with detectable loss of function or neurological deficit. Histological lesions, however, included widely disseminated axonal degeneration, gliosis, and atrophy of spinal nerve roots in the surgical area. The spinal cord adapted to shortening of the vertebral column by becoming intrinsically shorter, rather than be being displaced within the spinal canal.
