| Objection: As the population ages, osteoporosis will increase dramati- cally, along with the increased fracture risk, including the vertebral fractures and the extremity fractures such as the proximal femoral fractures, fractures of the proximal humerus and of the distal radius. The treatment of osteoporo- tic extremity fractures has become the main challenge for the osthopaedic surgeons. Especaily the femoral neck fracture, it accounts for 53% of the hip fracture. Because of the specialy of the anatomic structure and biomechanics, it would be injured easily when the fracture took place. This not only affected the fracture healing but also would produce ischemic necrosis of femoral head easily. It is reported that femoral neck fracture nonunion is 20% and femoral head ischemic necrosis is 30%.It is a diffcult problem in orthopaedics because it′s rate of nonunion and avascular necrosis is so highly. To the special pathologic state of osteoporosis and some bone biomethanics characteristic, it is important for clinical meanings to launch the fixed mechanics and biological study in osteoporosis fracture, increase fracture fixed instantaneous stability, long-term stability, offer the good symphysis environment. Poor implant anchorage in the osteoporotic bone requires the new solutions for the treatment. Cement -augmentation of the femoral neck fracture could reinforce osteoporotic bones. This study was to evaluate: (1) the feasibility of cement-augmentation with cannulated screws with side holes (2) its influence on stable osteosynthesis by mechanical testing .Methods:1. The preparation of the screw: Improve general cannulated screw, design 2 side holes between the pitch of whorl district, diameter about 1.5mm, alternate 2-3rd pitch, rotated 180°by pole along spiral shell.2. Eight pairs of embalmed elderly female osteoporotic femur were obtained, and the average age at the time of death was 71.5 years (range,63 to 78),The soft tissues were stripped ,and the radiography was done to evacuate congenital abnormality, fracture and tumor. All specimens were evaluated with dual energy x-ray absorptiometry to determine the bone-mineral density. A swing saw was used to creat an osteotomy as the femoral neck fracture model and to remove at one-third of distal femur for being easily potted in dental cement.3.All the specimens were randomly divided into 2 groups , The fractures fixed using standard cannulated screws, marked group B and using modified cannulated screws marked group A.4 First , the displacement of group A ,B samples were tested under physiological load of 700N, Subsequently, specimens of group A were augmented with bone cement ,tested their displacement as the previous method. Third, failure load of group A (after cement-augmentation modified cannulated screw) and group B (with general cannulated screw) was tested.5.comparing biomechanical result of group A and B by statistical.Result:1. All the specimens were osteoporotic, and no significant difference were observed among their bone mineral densities.2. Between group B ,group A with bone cement and without bone cement ,under physiological load of 700N,the displacement of specimens with modified cannulated screw together bone cement(5.408±2.057 mm*10-1) significantly decreased than that group B(9.761±3.236 mm*10-1)and group A without bone-cement(10.088±3.834 mm*10-1), respectively 55.4% and 54%(P<0.05), Specimens of group A augmented with bone cement failed at mean of 3,667N(SD=841N) ,This was significantly greater (P<0.05) than the mean of group B for controls 2887N(SD=667N), There was a mean relative improvement in fixation strength of 127 percent.Conclusion: The treatment of femoral neck fracture using modified cannulated screw with bone cement increased the initial stability of the fracture fixation technique and improved fixation strength .It is a feasibility method to reinforce fixation strength of the femoral neck fracture in osteoporosis fracture. It is promising for fixation in osteoporotic femoral neck fracture in old patients.
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