In this study, a method was developed for distinguishing insertion and driving performance between different self-tapping bone screw designs. To measure screw starting load, torque and displacements, a test apparatus was developed utilizing a modified drill press with the capability to measure in-line torque, axial compression load, and axial displacement. Specimens were inserted into cadaver bone to measure a baseline response and a bone analog was developed to mimic the bicortical application of screws in the cadaver model. Recorded data could be used to measure a distinguishable screw starting load and the torque for the insertion of bone screws. The results were similar between the cadaver bone and the bone analog. The average insertion load ranged from 5.4 to 64.5 N in cadaver tests and 9.0-41.0 N in the construct tests. Average first cortex insertion torques ranged from 0.53 to 0.66 N-m in the cadaver tests and 0.29-0.32 N-m in the construct test. Average second cortex insertion torques ranged from 0.70 to 1.03 N-m in the cadaver tests and 0.60-0.63 N-m in the construct tests. This method successfully illuminated differences between several different selftapping screw designs and was also successfully employed to determine the impact of design and manufacturing methods on screw performance. An interesting finding in this study is that axial starting load is very sensitive to screw tip design whereas insertion torque is not.
Summary
Spontaneous echocardiographic contrast is the term used by ultrasonographers to describe particulate material visible in intracardiac blood by ultrasound. The purpose of the present study was to determine the prevalence of spontaneous contrast in a farm population of Thoroughbreds and in the farm's racehorses. The results showed that spontaneous echocardiographic contrast is common in Thoroughbreds, and that the prevalence of contrast is affected by age, male gender, racing and pregnancy. The amount of right‐sided cardiac contrast was quantitated by videodensitometry and was increased in horses with a history of exercise‐induced pulmonary haemorrhage, in comparison with racehorses without a history of bleeding. Since circulating platelet aggregates are known to produce pulmonary haemorrhage in experimental animals and their presence has been associated with echocardiographic contrast, additional studies evaluating platelet aggregates as the aetiologic agent for exercise‐induced pulmonary haemorrhage are warranted.
Total elbow replacement (TER) is a clinically successful procedure yet isolated, gross mechanical complications associated with implant durability persist. The objectives of this study were to (1) develop a clinically relevant in vitro methodology to replicate the reported damage modes and (2) demonstrate durability improvements of a next-generation linked, semiconstrained design. Two TER prostheses were tested on a biaxial test frame at 1.4 Hz in 37 AE 3 deionized water through 0 to 130 flexion/extension at various load levels simulating high demand, posttraumatic patients until either component failure or run out to 200 000 cycles. The damage patterns of tested components were qualitatively compared to retrieved components to establish the clinical validity of the methodology. The run out load of design 1 was equivalent to 100 N weight in hand (WIH). Specimens tested at higher load levels exhibited multimodal damage consistent in appearance with the clinical literature. The minimum run out load of design 2 was 110 N WIH with no significant damage observed on the components. The methodology developed here was shown to reproduce the clinical damage modes associated with TER in high demand, posttraumatic patients. The method was able to distinguish performance differences within and between 2 different linked, semiconstrained designs.
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