ABSTRACT
BACKGROUND: The previous biomechanical study of hip and hip replacement mostly analyzed the compressive, flexural and torsional mechanical properties and the three-dimensional finite element mechanics after prosthesis placement. There are few reports about the stress relaxation characteristics after femoral implant replacement. OBJECTIVE: To compare and analyze two kinds of artificial prostheses after hip replacement from the angle of rheology by simulating femoral stress relaxation experiment so as to provide stress relaxation characteristics parameters. METHODS: Eight femoral samples were randomly selected as the conventional prosthesis group. The specimen was fixed to the operation platform. The specimens were taken from the part of 1.5 cm above trochanter minor to trochanter major. After removal of the femoral head and most of the femoral neck, cancellous bone distal to the femoral section was removed. Medullary cavity was dredged from the distal side of trochanter major to determine the position of medullary cavity. The medullary cavity hammer was used to expand the medullary cavity. The detritus inside was removed. An additional eight femoral specimens were randomly taken for femoral neck prosthesis group. Two groups of samples were placed on the workbench, and experiment was conducted at increased strain speed of 50%/min. The time was set at 7 200 s, and 100 data were collected. RESULTS AND CONCLUSION: (1) Stress relaxation amount was 0.384 MPa at 7 200 s in normal femur as previously reported. The stress relaxation amount was 0.379 MPa and 0.362 MPa in the conventional prosthesis group and femoral neck prosthesis group. The stress relaxation amount was significantly larger in the femoral neck prosthesis group than in the conventional prosthesis group at 7 200 s (P < 0.05). (2) Two groups of stress relaxation data were obtained and stress relaxation equation was established by three parameters of the model. It is conducive to clarify the stress relaxation characteristics of different implants into the femur. (3) Femoral neck prosthesis group and conventional prosthesis group have different stress relaxation mechanics. Due to the retention of the femoral neck, less impact was found on the stress relaxation mechanics.
ABSTRACT
Objective To analyze the trend of incidence and mortality on thyroid cancer in China.Methods Data from 32 cancer registry sites in China was collected and Jionpoint model was used to obtain the crude,age-specified incidence and mortality,both Chinese national and world age-standardized rates of incidence and mortality and their trends.Results The crude incidence of thyroid cancer was 4.44/105,and the Chinese national and world age-standardized rates were 2.89/105 and 3.31/105 respectively.The crude mortality of thyroid cancer was 0.44/105,with the Chinese national and world age-standardized rates as 0.21/105 and 0.29/105 during 2003-2007 in the country.Thyroid cancer accounted for 1.67％ and 0.26％ of the Chinese national and world age-standardized proportions,for total cancers.Both incidence and mortality of thyroid cancer were higher in females than in males,3.38 and 1.75 times higher in urban areas than those in rural areas.The incidence of thyroid cancer showed annually increase of 14.51％ while the mortality had an increase of 1.42％.Conclusion The incidence and mortality of thyroid cancer increased rapidly in China,calling for more control efforts on this disease.