Papers by Elizabeth Friis
Springer eBooks, 1999
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Springer eBooks, 1999
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Springer eBooks, 1999
Charley Davidson did not belong to a motorcycle gang. He had never heard of Sturgis, South Dakota... more Charley Davidson did not belong to a motorcycle gang. He had never heard of Sturgis, South Dakota, and did not even have a tattoo, but he loved the rush of wind in his face as he rode his big motorcycle back and forth to work. He was a very careful rider and always wore his helmet, but he was always worried about the lack of courtesy automobile drivers often show around bikes. It was not discourtesy, however, that caused a pickup truck suddenly to turn in front of him. The ensuing collision with a road sign resulted in a severe, open fracture of Davidson’s leg. After an assessment in the emergency room indicated no other injuries, he was taken to the operating room, where the large soft tissue wound was cleaned and debrided, and his tibia stabilized with a monoplane external fixture. Will such a stabilization device allow this fracture to heal?
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Springer eBooks, 1999
Twenty-four-year-old Jack Jones, a second-year orthopaedic resident, had been a track star in the... more Twenty-four-year-old Jack Jones, a second-year orthopaedic resident, had been a track star in the decalthalon when he went to undergraduate school at Wichita State University. During medical school at the University of Kansas, he concentrated on the high jump, practiced nearly every day, and even competed in the 1996 Olympic Games tryouts. He trained constantly, running sprints and jumping when the pit was available. But on becoming a resident with a more rigid and demanding schedule, he found it almost impossible to get in his daily workout and had to be content with a more erratic calendar of practicing. Sometimes he got up at 5 a.m. to work out and jump before early morning rounds at the hospital, or he worked out late at night after coming home from the hospital. Nevertheless, he did manage to train three or four times a week and thus burn up enough calories to allow him to cope with the hospital’s food and maintain a weight of 65 kg. In his high jump, he did work and consumed energy. How much potential energy could he convert to kinetic energy by just barely clearing the six-and-a- half-foot high bar?
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Springer eBooks, 1999
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Springer eBooks, 1999
Fifty-year-old Wilma Jones tripped on the step as she was returning to her apartment and knew imm... more Fifty-year-old Wilma Jones tripped on the step as she was returning to her apartment and knew immediately—when she put out her hand to break her fall—that she had severely injured her wrist. An X ray confirmed a fracture of the distal radius, Colles’ type, and she was treated by a closed manipulation and casting in the emergency room. Why did Wilma’s radius break with such a minor fall?
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Journal of Biomechanics, Jun 1, 1992
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Springer eBooks, 1999
Justin Dawn, engineering diploma in hand, was hired to work in the Orthopaedic Research Laborator... more Justin Dawn, engineering diploma in hand, was hired to work in the Orthopaedic Research Laboratory at Mega General Hospital shortly after Sanza Time was admitted with the broken femoral rod. Having seen such broken rods too many times in her long career, the chief orthopaedic surgeon at Mega General asked the staff of the research laboratory to design a stronger rod. In order to design such a device, the staff immediately recognized that some notion of the strains incurred by the current rod would have to be taken into account. Justin’s first project was thus to determine what such strains might be during normal walking. How would Justin go about doing this?
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Journal of Biomechanics, Mar 1, 1993
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American Journal of Sports Medicine, Sep 1, 1994
Thermoelastic stress analysis was used to examine stresses on the anterior surface of patellae af... more Thermoelastic stress analysis was used to examine stresses on the anterior surface of patellae after patellar bone block excision for autogenous graft anterior cru ciate ligament reconstruction. Complications of anterior cruciate ligament injury often lead to degenerative changes in the knee that can require total knee joint replacement. It was hypothesized that stresses in a bone block-compromised patella may be increased even further by insertion of a patellar prosthesis. All pa tellae were first tested intact and then were retested after a sequence of surgical modifications including pa tellar prosthesis implantation, tapered bone block ex cision, square bone block excision, and both shapes of excised bone blocks with a patellar prosthesis in place. Stresses in patellae with bone blocks excised were sig nificantly greater than stresses in intact patellae. The anterior surface stress pattern in the loaded patella was significantly altered by excision of a bone block. There were no significant differences between maximum stress in patellae with tapered and square bone blocks excised. A finite element analysis showed that excision of a larger trapezoid-shaped bone block greatly in creased maximum stress levels. Insertion of a patellar prosthesis did not significantly alter stress patterns or maximum stress levels in the patella.
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Springer eBooks, 1999
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Springer eBooks, 1999
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Springer eBooks, 1999
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Charley Davidson’ s pal Sanza Time had a similar accident, but, instead of fracturing his tibia, ... more Charley Davidson’ s pal Sanza Time had a similar accident, but, instead of fracturing his tibia, he sustained a closed fracture of the femur. This fracture was treated by closed intramedullary rodding, and Sanza, against the advice of his surgeon, was back on his bike as soon as the repair shop pronounced it ready. Also against the advice of his doctor, he went back to his job in a steel mill, where he was on his feet all day, and even played a little Softball on weekends. His doctor was hardly surprised, then, that, about 11 weeks after his operation, Sanza had a sudden pain in the thigh. A roentgenogram showed a broken rod associated with an ununited femur. How could such a thing happen?
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Journal of Arthroplasty, Feb 1, 2008
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Springer eBooks, 1999
Instead of doing something dramatic (such as skiing) to break a bone, Fred Ferd tripped over the ... more Instead of doing something dramatic (such as skiing) to break a bone, Fred Ferd tripped over the curb on the way to his car after work and fractured the midshaft of his radius and ulna. His fractures were treated the following day by open reduction and plating of both bones in the Swiss manner. His convalescence was uneventful, and his fractures healed in about 10 weeks, but subsequent X rays showed some resorption of the bone under the plates, and his surgeon began to suggest that the bone might not be as strong as he had hoped. What could cause bone under a rigid plate to suddenly begin to be absorbed?
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Journal of Medical Engineering & Technology, Jun 8, 2022
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Journal of The Mechanical Behavior of Biomedical Materials, Feb 1, 2022
Quality and timing of bone healing from orthopedic surgeries, especially lumbar spinal fusion pro... more Quality and timing of bone healing from orthopedic surgeries, especially lumbar spinal fusion procedures, is problematic for many patients. To address this issue, clinicians often use electrical stimulation to improve surgery success rates and decrease healing time in patients with increased risk of pseudarthrosis, including smokers and diabetics. Current invasive electrical stimulation devices require an implantable battery and a second surgery for removal. Piezoelectric composites within an interbody implant generate sufficient power under physiologic loads to deliver pulsed electrical stimulation without a battery and have demonstrated promising preclinical bone growth and fusion success. The objective of the current study was to assess the power generation and fatigue resistance of three commercially manufactured piezocomposite configurations in a modified implant design to demonstrate efficacy as a robust biomaterial within osteogenic implants. The three configurations were electromechanically assessed under physiological lumbar loading conditions, and all configurations produced sufficient power to promote bone healing. Additionally, electrical and mechanical fatigue performance was assessed under high load, low cycle conditions. All configurations demonstrated runout with no gross mechanical failure and two configurations demonstrated electrical fatigue resistance. Future piezoelectric implant design decisions should be based on power generation needs to stimulate bone growth, as mechanical fatigue efficacy was proven for all piezocomposite configurations tested.
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ASTM International eBooks, Mar 4, 2009
A finite element model for predicting the effect of fiber bridging, fiber properties, and fiber-m... more A finite element model for predicting the effect of fiber bridging, fiber properties, and fiber-matrix interface strength on the crack-tip stresses and crack propagation potential of a chopped-fiber composite is proposed.The method of virtual crack extension was used to model crack growth in a micromechanics composite material model. The purpose of this study was to investigate the effects of fiber bridging of a crack and fiber-matrix interface strength on the stress intensity and strain energy release rate in virtual crack extension. A model of an aligned, 1% by volume fiber loading, chopped-fiber composite with a preexisting crack was developed to represent a portion of a fracture toughness or fatigue crack propagation specimen. Nonlinear contact elements were used to model fiber-matrix interface strengths. The von Mises stress at the crack tip was calculated for each configuration before crack extension, and the strain energy release rate was calculated for each crack step. The presence of fibers without bridging of the crack did not greatly affect the stress at the crack tip. However, fiber bridging of the crack reduced the crack tip stress by a factor of seven. The magnitude of strain energy release rate was greatly reduced and the sign of the slope of the strain energy release rate versus crack length curve was changed from positive to negative by fiber bridging. In accordance with the theory of tough fiber reinforcement of brittle matrices, the results of applying nonlinear contact elements with varying coefficients of friction predict that an intermediate fiber-matrix interface strength will be most effective in toughening a brittle composite.
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Springer eBooks, 1999
Mabel Able, 80 years old, lived alone in a two-story house taking care of her own needs, such as ... more Mabel Able, 80 years old, lived alone in a two-story house taking care of her own needs, such as cooking, cleaning, and tending a small garden and a flower bed. Until about two years ago she also walked around the block every day but recently has confined herself to her house and yard. Her next-door neighbor comes by to check on her every day and helps her with her grocery list, mails packages for her, and so on. On Monday morning when the neighbor went to check Mabel, she found Mabel lying on the kitchen floor, moaning and complaining of pain in her right hip. The neighbor could see that the leg was turned out and shortened, and she immediately suspected that Mabel had slipped on the linoleum when she came downstairs to make her morning coffee. The rescue squad was called, and Mabel was transported to the hospital, where the suspicion of a fractured hip was confirmed by a radiograph. After her family doctor came in and pronounced Mabel fit for surgery, she was taken to the operating room, where internal fixation with a compression screw and side plate was accomplished without any complications. The pre- and intra-operatice X rays are shown in Figure 4.1. What were the mechanical factors c ausing Mabel’s hip to break?
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Papers by Elizabeth Friis