Skip to main content
main-content
Top

Over dit boek

A PRIMER OF BIOMECHANICS is the first volume of its kind to present the principles of biomechanics with a highly clinical orientation. Dr. Lucas and his colleagues (specialists in biomechanics) have assembled a practical guide utilizing case presentations to make this very technical and complicated material palatable to the orthopaedic resident and practitioner. This "user-friendly" text is further enhanced by well integrated chapters covering all the basic materials and the latest information of this rapidly evolving field from the perspective of its useful application. Each case presentation is followed by a detailed, but easily understandable explanation of the biomechanical principles involved and includes protocols for treatment. This volume is a must-have for orthopaedic residents and practitioners.

Inhoudsopgave

Voorwerk

1. Mechanics

Abstract
Willie Wonderment, 9 years old, was more inquisitive than the typical youngster. Instead of merely wondering if he could jump higher or run faster than the rest of his playmates, he had to prove to himself that he could indeed do so. Not content simply to wonder what was in a bird’s nest high in a tree, he climbed up to take a look.
George L. Lucas, Francis W. Cooke, Elizabeth A. Friis

2. Moments

Abstract
A first-year orthopaedic resident, Barkley Brown found himself on radiology service shortly after arriving at Metro General Hospital to start his residency and discovered that he had a little unexpected spare time. Having lifted weights during high school and college to keep in shape for wrestling and football, Dr. Brown welcomed the chance to go to the gym and pump a little iron. He preceded his lifting by doing a series of upper- and lower-body stretches and then started to work on individual muscle groups—first the biceps, then the triceps, then the “pecs,” then the “lats,” and so on. How much force did he generate across the elbow joint by doing a biceps curl with a 15-kg weight?
George L. Lucas, Francis W. Cooke, Elizabeth A. Friis

3. Strength of Materials

Abstract
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?
George L. Lucas, Francis W. Cooke, Elizabeth A. Friis

4. Stresses in Bending

Abstract
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?
George L. Lucas, Francis W. Cooke, Elizabeth A. Friis

5. Stresses in Torsion

Abstract
Sandra Snowflake, an X-ray technician at Mega General Hospital, spent most of her spare time either in the gym or in the park running. Thus she was in excellent physical shape. Her major reason for staying in shape was her love of skiing, and she worked and lived for the three separate weeks she took for ski vacations in Colorado. This year spring skiing was exceptionally good, and she was at the top of her form, schussing down the black diamond runs with ease. Unfortunately, the new bindings she was getting used to had not been adjusted exactly right, and she knew immediately —when she hit the icy patch and lost control of her outside ski—that her leg was broken. This was confirmed at the small hospital at the base of the slope where she was taken by the ski patrol. When Dr. Fromm showed her the film of her leg, her experienced eye recognized a spiral fracture of the tibia. Why does torsion create a tibial fracture?
George L. Lucas, Francis W. Cooke, Elizabeth A. Friis

6. Stress Shielding of Bone

Abstract
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?
George L. Lucas, Francis W. Cooke, Elizabeth A. Friis

7. Work and Energy Concepts

Abstract
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?
George L. Lucas, Francis W. Cooke, Elizabeth A. Friis

8. Stress Raisers, Fracture, and Fatigue

Abstract
Sixty-eight-year-old Martha Mainstream had a replacement arthroplasty for her hip three years ago for severe osteoarthritis. Because she no longer had to utilize a cane to get around, the operation changed her life, and she was relieved of the nearly constant pain in her groin and down her thigh. As a matter of fact, she had resumed walking and swimming for exercise and had lost 20 pounds of excess weight. Alas, when was went out ot feed her cats, she slipped on some wet grass and sustained a fracture of her femur well below the prosthetic femoral stem. She underwent surgery again and had a large bone plate applied across the fracture, shown in figure 8.1. What problems are likely to arise from having two metal devices close together in this fashion?
George L. Lucas, Francis W. Cooke, Elizabeth A. Friis

9. Biomechanics of Pathology

Abstract
Martha Mainstream’s twin sister Matilda also had pain in her groin and in the thigh, but this had been a problem for only a couple of months. The discomfort was so persistent at night that she had great difficulty turning over in bed. Matilda had no cats to feed; she simply fell in her kitchen &or more accurately, her leg collapsed, causing her to fall. When she arrived at the hospital, the orthopaedic resident took a careful medical history before examining her and learned that she had had a mastectomy five years earlier but otherwise had had no serious medical problems. Unfortunately, the roentgenogram of the femur showed a large lucent lesion with a pathologic fracture that was most likely a metastatic focus related to her mastectomy. Many complex biochemical and biological activities are associated with such a fracture, but some are straightforward biomechanical ones, and the question arises, “How does replacement of bone by tumor weaken the bone?”
George L. Lucas, Francis W. Cooke, Elizabeth A. Friis

10. Mechanics of Treatment

Abstract
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?
George L. Lucas, Francis W. Cooke, Elizabeth A. Friis

11. Mechanics of Implants

Abstract
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?
George L. Lucas, Francis W. Cooke, Elizabeth A. Friis

12. Considerations in Biomechanical Testing

Abstract
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?
George L. Lucas, Francis W. Cooke, Elizabeth A. Friis

13. Biomaterials Basics

Abstract
Dr. J. P. Curmudgeon, chief of orthopaedic surgery at Mega General Hospital had done thousands of total hip arthroplasty operations with generally excellent results. Still, he was constantly in search of new and better methods of dealing with the problems of the arthritic hip. When he learned about the frequent use in Japan of a ceramic femoral head replacement, he contacted a Japanese colleague in Tokyo and went there to learn the technique. His gracious host invited him to assist in the operating room and even handed him the ceramic femoral head when it was time to insert it into the patient. Unfortunately, Dr. Curmudgeon did not realize how slippery the device was and dropped it onto the operating room floor, where it shattered. Needless to say, Dr. Curmudgeon was highly embarrassed. Was the ceramic head defective? If not, could something so brittle be expected to function as a hip replacement?
George L. Lucas, Francis W. Cooke, Elizabeth A. Friis

14. Orthopaedic Alloys

Abstract
At the time that Charley Davidson had his fractured tibia treated, it was customary to treat such fractures with an intramedullary rod if the soft tissue wound was not too severe. Tibial rods were customarily made of cobalt-chrome alloy and were quite serviceable, but recently a trend to making such rods out of titanium had developed. Metal is metal, is it not, and why would one type be any better or worse than another?
George L. Lucas, Francis W. Cooke, Elizabeth A. Friis

15. Corrosion in the Body

Abstract
Continuing with the question concerning titanium, a further episode in the life of Dr. Curmudgeon bears repeating. Early in the development of total hip implants, the implants were available in just a few sizes and configurations, but as more and more different types of patients were operated on, more options were needed. Thus evolved the concept of modularity, which allowed different heads to be put together with different shaft configurations, neck lengths, and so on. Dr. Curmudgeon was not aware one day that, after he had placed a titanium shaft into the femoral canal, the scrub nurse had handed him a cobalt-chromium (Co- Cr) alloy femoral head of the appropriate size. Is the difference in the two metals likely to cause any problems, and, if so, what sort of problems should we expect?
George L. Lucas, Francis W. Cooke, Elizabeth A. Friis

16. Orthopaedic Polymers

Abstract
The Mainstream twins’ friend Pearl had an arthritic knee that had been treated by implant arthroplasty, and she was doing very well indeed. She was able to do virtually anything she wished, but in recent months she had begun to have pain in the knee. Because the discomfort limited her walking ability, she made an appointment to see her surgeon, who told her she needed a revision operation. When the surgeon opened the knee, he found the femoral component intact but the plastic on the tibial side badly worn. These modern plastic components should last forever, should they not? What happened to this one?
George L. Lucas, Francis W. Cooke, Elizabeth A. Friis

17. Tissue Mechanics

Abstract
Arrowhead Stadium was the site of the umpteenth meeting of the Kansas City Chiefs and their arch rivals, the Oakland Raiders. Kansas City returned the kickoff to their own 28-yard line and, determined to strike early and often, sent their prime wide receiver on a long down and out into Raider territory. Just as the receiver caught the ball, he was hit by two Oakland defenders, and his knee flexed acutely. The receiver felt an immediate burning pain in the front of his knee and was unable to stand up again. Examination in the locker room by the team physician revealed a high-riding patella and a palpable depression where the patellar tendon normally resided. How could such a well-conditioned athlete sustain a tendon rupture?
George L. Lucas, Francis W. Cooke, Elizabeth A. Friis

Nawerk

Meer informatie