The compressive forces generated by the AO/ASIF 3.0
mm cannulated cancellous and 2.0
mm cortical screws, Mini-Acutrak and Herbert/Whipple small bone cannulated screws were measured in the laboratory ...with the use of simulated cancellous bone and a load cell washer as a means of quantifying their fixation capabilities. The Herbert/Whipple screw and the Mini-Acutrak screw were found to have nearly identical compression capabilities and provided more compression than the cortical screw. The AO/ASIF cannulated screw when used with a support screw demonstrated a compressive capacity twice that of the 2.0
mm cortical screw and higher than the headless Mini-Acutrak and Herbert/Whipple screws. The Mini-Acutrak screw produced about 70% of compression of the cancellous screw in spite of having a diameter almost half that of the cancellous screw. The Herbert/Whipple screw in spite of its larger size compared to the Mini-Acutrak produced almost the same amount of compression.
The compression forces on disc of spine were recommended from The National Institute for Occupational Safety and Health (NIOSH). The safety level for disc compression forces during lifting object in ...manual material handling should less than 3,400 N. There are many studies about disc compression forces in manual material handling, but manual human handling less researched. The aim of this study is to compare L4/L5 compression forces in four manual human lifting techniques and three phases of lifting and transferring. Thirty two subjects lifted a 60±5 kilogram person in four techniques: two-handed seat carry, four-handed seat carry, Fore-and-Aft carry and Chair carry from table height 50 cm walked 9 m, rested 3-5 minutes between each technique. Lifting and transferring was divided 3 phases (origin lift, carry and destination lift). Five cameras were installed in different angle of views to record subject movement during lifting. The static mode of the University of Michigan's Three-Dimensional Static Strength Prediction Model (3DSSPP) was used to predict lumbar disc compression forces (L4/L5) in each technique during lifting. Only origin lift phase has the average maximum L4/L5 compression forces more than 3,400 N especially Two-handed seat carry and Four-handed seat carry techniques. The results of L4/L5 compression forces of manual human lifting might help to prevent lifters or authorities from back injury.
Recent studies of the spine in adolescents who have sustained trauma have shown injuries to the growth zone, whereas injuries to the vertebral body have been described in other studies of only ...adults. There are also reports on different clinical signs and radiological findings in adolescents with lumbar disc herniation when compared to adults. In order to find an explanation for these differences between adolescents and adults, this experimental study was performed. Six cadaveric lumbar motion segments (vertebral body-disc-vertebral body) obtained from three young male pigs and six lumbar motion segments obtained from three mature male pigs were tested in axial compression to failure. All units were examined with plain radiography and magnetic resonance imaging before and after compression. After the compression, histological samples were taken from the injury site. In the adolescents, a fracture was consistently found in the endplate through the posterior part of the growth zone, displacing the anulus fibrosus with a bony fragment at the point of insertion to the vertebra. This type of injury could not be detected in any of the adults; instead, there was a fracture of the vertebra in four cases, and in two cases, a rupture of the anulus fibrosus without a bony fragment was seen. This study showed that, when compressed to failure, the weakest part of the lumbar spine of the adolescent pig differs from that of the mature pig in the same way that studies on human spinal units have shown.
In order to repair a fractured bone, one must understand the forces applied to the bone and how the various repair methods can counteract those forces. This understanding is what allows a surgeon to ...select the appropriate repair method. The forces to consider are: compression, tension, torsional, shear, and bending. When a bone breaks, the contractile force of the muscle will cause the ends to override. Ensuring that the muscles are relaxed and/or stretched can greatly assist the surgeon in reducing the fracture. Hanging the limb under general anesthesia while the patient is being prepared for surgery is helpful, as well as having a very good analgesia regime on board. There are a variety of types of drill that will work well for orthopedic surgery. The general fracture repair instruments necessary will vary slightly based on the size of the patient and implants being used.
Since a patient's ability to perform simulated work activities guides return-to-work decisions, a significant question to address is whether the simulated work environment accurately reflects the ...actual work environment. Work hardening programs have been used extensively as a method of rehabilitating workers to return to their pre-injury functioning levels. Re-training workers to lift boxes is a common method used to simulate the work environment. Although very few boxes used in the real work environment have handles, boxes with handles are often used in the simulated work environment. The difference in compression forces at the L5/S1 joint while lifting boxes with and without handles was investigated. The Lift Trak Motion Analysis system was used to estimate lumbar isometric compression forces exerted while lifting a 20-pound (9.07-kg) box. The results indicated that estimates of compression forces when lifting a box without handles were significantly different (p < 0.01) than when lifting the same box with handles. Based on these results, it is recommended that work hardening professionals carefully re-evaluate the simulated work environments currently being used for treatment.
An unusual occurrence of decreasing tablet disintegration time with increasing tablet hardness was explored. Tablets were made with varying ratios of starch disintegrant to starch paste and ...compressed with eight different forces. This unusual disintegration pattern is modified by changes in the starch ratios. The reason for this phenomenon is ascribed to gain swelling as the mechanism by which starch acts as a disintegrant.
Ten subjects executed a number of weight-holding and force-resisting work tasks while standing either upright or with their trunks in 30 degrees of forward flexion. All tasks involved sagitally ...symmetric body configurations and were performed isometrically. A simple calculation scheme was devised to predict the lumbar trunk muscle contraction forces and the lumbar spine compression forces required for execution of each task. The myoelectric activity was recorded quantitatively at eight sites over the lumbar trunk muscles and at four sites over the abdominal muscles. Good correlation was found between the predicted muscle contraction forces and the myoelectric activities.
Techniques similar to those used in instrumenting tablet presses were applied to an automatic capsule-filling machine. The dosing unit was modified to allow the bonding of strain gauges to the ...compression piston. The guages formed the arms of a Wheatstone bridge circuit. Thus, compression and ejection events were monitored by measuring the bridge unbalance voltage using a suitable amplifier-recording system. The instrumented piston was calibrated in a physical testing machine. Dosing unit rotation required the interposing of a mercury contact swivel between the amplifier and instrumented piston. The instrumentation system required only one minor, permanent modification to the machine, a cut in the dosator tube. Since the same dosator piston sensed both compression and ejection, only one of the two dosing units was instrumented and the other was removed from the machine. A solenoid switching system was devised which only permitted the feeding of empty gelatin shells into the filling cycle for the instrumented piston. Representative fillers were run at constant powder bed and piston heights. Oscilloscope tracings showed two stages in slug formation: (a) "precompression," representing the force sensed during dipping of the dosator into the powder before actual compression, and (b) actual piston compression. Generally, the maximum slug compression force fell to zero rapidly on retraction of the piston, but in some cases a retention force was noted, possibly due to elastric rebound of the slug against the retracted piston. A negative deflection due to binding of the piston also was observed in tracings of one material. Lubricated batches exhibited ejection forces of less than 1 kg.
PDF
