The Study of Osteoporosis Induced Femoral and Vertebral Fractures
Date Issued
2010
Date
2010
Author(s)
Lin, Shih-Wei
Abstract
During the past few years, several existing problems in the treatment of osteoporotic fractures were selected for study. The results are presented in chapter two to six. This essay consists of two major parts. For the first part, the task of fixation failure and aiming problems for the treatment of proximal femoral fractures were studied. In the second part, we concentrated on improving the techniques of vertebroplasty to avoid cement leakage.
For the biomechanical study of proximal femoral fractures, a proper specimen is needed for testing. Because the source of cadaver specimens is scarce and the preservation of specimens is difficult.We tried to apply a porcine model to perform the mechanical test in the pilot study which is discussed in chapter 2. Unfortunately, the result was disappointing; the non-osteoporotic specimen is so tough that its performance is completely different than we had expected. So, it may not be appropriate to use non-porotic specimens to simulate the osteoporotic proximal femoral fractures. This conclusion may be expanded to other fields, such as spinal or skeletal biomechanical studies.
Owing to osteoporosis, the internal fixation of proximal femoral intertrochanteric fractures can easily be failed. In order to strengthen the fixation effect in the surgery, in chapter 3 we modified the traditional Dynamic Hip Screw by increasing the diameter of the lag screw. The diameter of the lag screw is enlarged so that two transfixing screws are allowed to pass through it and be affixed to the femoral neck. We applied weak saw bone to simulate the osteoporotic proximal femoral fracture and fixation. The biomechanical results of this study showed that the strengthening effect of the modified lag screw can be significant.
Because malposition of lag screw is one of the most important reasons of fixation failure, the increase in accuracy of the lag screw position is extremely important. Because the lag screw tip can be incorporated with the strong subchondral bone, and hence the chance of lag screw migration can be decreased. In order to increase the accuracy of surgery, in chapter 4, we have designed a new intramedullary guiding device. A clinical test was performed to validate the feasibility of using the guide. From the results of the study, the accuracy of the lag screw placement can be increased; so the expected fixation failure would be decreased. The fluoroscopy time can be decreased as well which is helpful for the patient and medical personnel. Other benefits of the technique are an increase in operation efficiency and a decrease in operation time as well.
Vertebroplasty is commonly used in the treatment of unhealed painful vertebral fractures. The cement is injected into the fractured vertebra in low viscosity and high pressure, where cement leakage is common. Severe complications can result if cement leaks into the spinal canal and pulmonary area. To reduce the above complications, Kyphoplasty was developed; cement is injected at lower pressure and higher viscosity. However, the material cost of Kyphoplasty is high and there exists a risk of bone fragment extrusion into the spinal canal while the balloon is inflated. To avoid the above potential complications in chapter 5, vertebroplasty is performed with mini invasive open surgery. A small wound and a cavity is created at the vertebral body by a curate. When the cement is in the state of viscoplastisity, it is delivered into the cavity of the vertebral body and then tamped for compactness. We have successful experiences in 6 cases. Because cement is delivered in a high viscous state, the risk of leakage is extremely low and pain relief is excellent in all cases. To validate the biomechanical effectiveness of the above technique; we performed a biomechanical test in seven human cadaveric thoracic vertebrae. From the experimental data, the viscoplastic state bone cement vertebroplasty can restore the strength of a fractured vertebra. The restored strength can explain the clinical observed pain relief of the patient. From the macroscopic view of the sliced specimen, there was good bonding between bone cement and trabecular bone.
In summary, we tried to improve the technique and solve some of the problems which are encountered in the treatment of osteoporotic proximal femoral fractures and spine compression fractures. We hope these works do help increase the efficacy of surgery and decrease complications.
Subjects
osteoporosis
femoral intertrochanteric fracture
lag screw cutout
spine compression fracture
vertebroplasty
Type
thesis
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