| Femoral neck fracture, that is,"cervical hip fracture"constitutes 54% of the proximal femur fractures and 3.58% of all fractures of the body. It is one of the most common traumatic injuries, which could happen to any age people, especially the elderly. As the aging population increases, the number is on the up rise, according to the available data, the number of hip fractures in the world is estimated to 1.26 million in 1990, which is approximately double to 2.6 million by the year 2025, and 4.5 million by the year 2050. Most domestic and overseas studies pay more attention to the incidence of elderly, but seldom to the incidences of youth and children. The relationship between the cause of femoral neck fracture and age distribution is reported fewer, so is the relationship between AO classification and age distribution.Before 19th century, femoral neck fractures were treated by conservative method, because of long-term lying in the bed, many patients died of complications, such as hypostatic pneumonia, infection et al. And the ratio of fractures healing was low. Since Smith-Peterson introduced the triflanged nail in 1931, internal fixation remains an effective option for orthopedic surgeons to treat femoral neck fractures. Despite the techniques and the internal implants have been improved, the incidence of nonunion and avascular necrosis is still high, which has been reported to range from 10% to 20% for nonunion and 10% to 43% for avascular necrosis. So the femoral neck fracture is also called"unsolved fracture".The method of bone transplanting has been used in treating femoral neck fracture as a method to prevent nonunion and avascular necrosis. Muscle pedicle bone grafts transplanting and vascularized pedicle grafts transplanting are the major two surgical schedules used most by the orthopedist. Unfortunately, the blood supply with this construct is unreliable, and the procedure is traumatic largely and technically demanding, which requires microsurgical facilities and rich experience. By contrast, free bone graft transplanting is a minimally invasive and easy operation method, which is now used for the treatment of neglected femoral neck fracture and not healed fracture. There is not report about large samples of femoral neck fractures treated by free bone graft transplanting. AO cannulated screws'ability of anti-pressure and anti-rotation are excellent, which could also put pressure on the fracture. So it has become the most popular method to treat femoral neck fractures. But how about the therapeutic effect of fresh femoral neck fractures treated by cannulated screws fixation plus free bone graft transplanting? How do the cannulated screws and the bone graft place can achieve the best biomechanical stability? My study will do some research on the questions mentioned above.Part 1 The clinical epidemiological analysis of femoral neck fracturesObjective To investigate the clinical epidemiological feature of femoral neck fractures. Methods All the femoral neck fracture patients (during the period from 2003 to 2007 year in HeBei Orthopedics) were studied in retrospective method, which were divided into three groups according to age, children group(<16 years),adult group(16~60 years),older group(>60 years). All femoral neck fractures were divided into three types according to AO classification. The gender, age, fracture type, injury reason, treatment type and clinical results of the patients were analyzed.Results The survey found 2064 femoral neck fractures from 2003 to 2007 year. The numbers in each observation year were 356 , 381, 397, 454 and 476 .There were 74(3.59%) cases in the children group, 979(47.43%)in the adult group and 1011(48.98%)in the older group. The numbers according to AO classification were 960(46.51%),860(41.67.%), 244(11.82%)in the types 31-B1,31-B2,31-B3. 351 cases were followed up for about 4.3 years(range, 3 to 7 years), all of which were treated by cannulated screws. 12 cases (3.4%) of the fracture did not healed, and avascular necrosis of femoral head was fond in 54 cases (15.4%).Conclusion The numbers of femoral neck fracture are increasing gradually form 2003 to 2007 year. The incidence rates in older groups are higher than another two groups. The femoral neck fractures of man is more than women in adult group, and lower in older group. The highest incidence of AO type in children and adult groups were 31-B2 type, which in older group is 31-B1 type. These years along with the improving of surgical techniques and internal implants, the incidence of nonunion is becoming lower, but avascular necrosis rate is still high.Part 2 Biomechanical study of femoral neck fracture fixed with cannulated screws and iliac bone graft Objective Femoral neck fracture may get good clinical results when treated with bone graft. The purpose of this study is to evaluate the biomechanical stability of three cannulated screws supplemented with one cross iliac bone graft for femoral neck fractures and provide scientific basis for clinical application.Methods Ten pairs of proximal femora and ipsilateral iliac bone grafts with lateral and upper surface retaining cortex were harvested from ten cadavers fixed in formalin. Mean age of the cadavers was 62 years (rang, 57-78years). They were all males and of Chinese origin. The bone mineral density (BMD) of the proximal femora was checked by dual-energy X-ray bone densitometry. The ten pairs of femora and bone grafts were assigned into two groups randomly: cannulated screw fixation group(CS group) , cannulated screw with bone graft fixation group(CSB group). The specimens were cut with power saw to create a standardized midcervical osteotomy perpendicular to the cervical neck. The fracture was then reduced. In the CS group, the fracture was fixed by three parallel 7.3-mm cannulated screws, which were placed triangularly with one screw superior and two inferior. And in the CSB group, the fracture was fixed by three cannulated screws and an iliac bone graft. The screws were placed the same as the CS group, and the bone graft made an angle of 95°with the femoral shaft on postero-anterior position, which was inserted from greater trochanter toward the inferior and anterior part of femoral head and passed across the fracture line about 1.5cm. Each specimen was tested by a testing machine. First for rotation testing, the femoral head was rotated clockwise to 5°at a rate of 0.5°/s. The rotation and torque were recorded by the computer. Second the femoral head was loaded with a vertical compressive force to 1000N at a rate of 20N/s via a spherical shaped metal shell. The displacement and load were recorded by the computer. Then each specimen was loaded sinusoidally of 700N at a frequency of 0.5 Hz for 1000 cycles. After that each specimen was subjected to vertical compressive testing and rotation testing again. At last, each specimen was loaded to failure at a rate of 20N/s. Failure was defined as penetration of the femoral head by the screws, fracture extension beyond the plane of the osteotomy, permanent screws deformation or the load-displacement curve flatting on the computer The maximum load was recorded. All data was analyzed with a paired t-test using SAS V8 system. A p value of <0.5 was considered statistically significant.Results The mean BMD of the left and right femora were 0.871±0.157g/cm2 and 0.889±0.134g/cm2. No significant difference was observed between the left and right femora. Before the cycling compression testing, the torque in the CSB and CS group was 10.440±1.529Nm and 9.548±1.457Nm respectively when the femoral head was rotated to 3°, 14.720±1.422Nm and 14.115±1.384Nm respectively when the femoral head was rotated to 5°. The difference was statistically significant between the two groups (p<0.05).The displacement in the CSB and CS group was 0.323±0.021mm and 0.313±0.013mm respectively at a load of 700N, 0.417±0.013mm and 0.410±0.024mm respectively at a load of 1000N. There was no significant difference between the two groups in compression test at the load of 700N and 1000N (p>0.05). All the specimens finished the cycling compression testing at 700N compression force successfully. No fatigue fracture or screw failure occurred. After the cycling compression testing, the torque in the CSB and CS group was 10.562±1.622Nm and 10.018±1.355 Nm respectively when the femoral head was rotated to 3°,14.468±1.430Nm and 13.941±1.186Nm respectively when the femoral head was rotated to 5°. The difference was statistically significant between the two groups (p<0.05). The displacement in the CSB and CS group was 0.263±0.019 mm and 0.272±0.018mm respectively at a load of 700N, 0.358±0.021mm and 0.366±0.017 mm respectively at a load of 1000N. There was no significant difference between the two groups in compression test at the 700N and 1000N (p>0.05). The mean failure load of the CSB and CS groups was 2582.8±353.7N and 2474.9±252.7N respectively. No statistical difference was fond between the two groups(p> 0.05).Conclusions The strength of fixation with three triangle parallel cannulated screws for femoral neck fractures was not reduced when supplemented with one iliac bone graft,which make an angle of 95°with the femoral shaft. From the biomechanical viewpoint, this new surgery method could be used for the treatment of femoral neck fractures.Part 3 Biomechanical study of femoral neck fracture fixed with cannulated screws and iliac bone graft performed at different angleObjective To evaluate the biomechanical stability of three cannulated screws supplemented with iliac bone grafts at different angles used for fixation of femoral neck fractures and provide scientific basis for clinical application.Methods Nine pairs of proximal femora and ipsilateral iliac bone grafts with lateral and upper surface retaining cortex were harvested from nine cadavers fixed in formalin. There were six males and three females, mean age of which was 67 years (rang, 47-73years). The bone mineral density (BMD) of each proximal femora was checked by dual-energy X-ray bone densitometry. The nine pairs of femora and bone grafts were assigned into two groups randomly: cannulated screw with medial bone graft fixation group (CMB group), cannulated screw with cross bone graft fixation group (CCB group). The specimens were cut with power saw to create a standardized midcervical osteotomy perpendicular to the cervical neck. The fracture was then reduced and fixed with three parallel 7.3-mm cannulated screws and an iliac bone graft. The cannulated screws were placed triangularly with one screw superior and two inferior. In the CMB group, the bone graft was in the middle of three cannulated screws and parallel with it. And in the CCB group, the bone graft made an angle of 95°with the femoral shaft on postero-anterior position. All the bone grafts passed across the fracture line about 1.5cm. Each specimen was tested by a testing machine. First for rotation testing, the femoral head was rotated to 5°at a rate of 0.5°/s. The rotation angle and torque were recorded by the computer. Second the femoral head was loaded with a vertical compressive force to 1000N at a rate of 20N/s via a spherical shaped metal shell. The displacement and load were recorded by the computer. Then each specimen was loaded sinusoidally of 700N at a frequency of 0.5 Hz for 1000 cycles. After that each specimen was subjected to vertical compressive testing and rotation testing again. At last, each specimen was loaded to failure at a rate of 20N/s. Failure was defined as penetration of the femoral head by the screws, fracture extension beyond the plane of the osteotomy, permanent screws deformation or the load-displacement curve flatting on the computer The maximum load was recorded. All data was analyzed with a paired t-test using SAS V8 system. A p value of <0.5 was considered statistically significant.Results The mean BMD of the left and right femora were 0.794±0.073g/ cm2 and 0.803±0.082g/cm2. No significant difference was observed between the left and right femora. Before the cycling compression testing: The torque in CMB group was 8.716±1.731Nm, 12.490±1.744Nm respectively when the femoral head was rotated to 3°and 5°, and 9.914±1.658Nm, 14.027±1.780Nm in CCB group. The difference was statistically significant between the two groups (p<0.05). The displacement in CMB group was 0.522±0.064mm and 0.675±0.063mm respectively at a load of 700N and 1000N, and 0.364±0.046mm, 0.444±0.050mm in CCB group. There was significant difference between the two groups in compression test at the load of 700N and 1000N (p<0.05). All the specimens finished the cycling compression testing at 700N compression force successfully. No fatigue fracture or screw failure occurred. After the cycling compression testing: The torque in CMB group was 7.936±1.547Nm, 11.173±1.653Nm respectively when the femoral head was rotated to 3°and 5°, and 9.561±1.913Nm, 13.205±2.111Nm in CCB group. There was significant difference between the two groups in torque at 3°and 5°(P<0.05).The displacement in CMB group was 0.606±0.049mm and 0.732±0.071mm respectively at a load of 700N and 1000N, and 0.315±0.049mm, 0.398±0.051mm in CCB group. There was significant difference between the two groups in compression test at the 700N and 1000N(p<0.05). The mean failure load of the CMB and CCB groups was 2112.689±186.913N and 2360.811±204.340N respectively. The difference was statistically significant (p< 0.05).Conclusions Based on the data mentioned above, we can come to the conclusion: The biomechanical stability of fixation in CCB group is superior to which in the CMB group in rotation resistance, compressive resistance and the maximal load. This study provides a theoretical foundation for bone grafting in the treatment of femoral neck fracture. Part 4 Results of close reduction, cannulated screws fixation and free bone grafting for femoral neck fracturesObjective To study the therapeutic effect of femoral neck fractures treated by closed reduction, cannulated screws fixation plus free iliac bone graft transplanting.Methods From December 2008 to February 2010, 121 patients with femoral neck fracture were treated, including 64 males and 57 females aged 21-86 years old (average 55.5 years old). All cases were fresh and close fractures, 67 cases were left and 54 were right. According to the fractured part, there were 53 cases of subcapital fracture, 63 of transcervical fracture and 5 of basal fracture. According to Garden classification, there were 21 cases of typeâ…¡, 64 of type III and 36 of type IV. The time from injury to operation was 1 days to 14 days(average 4 days). All cases received closed reduction and cannulated screws fixation and iliac bone graft transplanting.Results The mean operation time was 65 minutes (from 45 to 100 minutes). All the fracture reduction reached Garden reduction indexâ… orâ…¡. Blood loss was from 70 ml to 255 ml, averaging 105 ml. No patients died during the hospitalization, all wounds healed, no infection was observed. One patient experienced incision edema and one patient got deep venous thrombosis of lower extremity, all the two patients were cured after symptomatic treatment. All the patients were followed up for 12 to 26 months, averaging 16.9 months. All the fractures achieved union at 4-9 months after operation. One case got fracture healing delayed. Avascular necrosis of femoral head occurred in 6 cases, 5 of which were treated with bone graft in the middle of cannulated screws and one with the bone graft made an angle of 95°with the femoral shaft. According to the Ficat classifications, 2 cases were stage one, 3 cases were stage three and 1 case was stage four. The earliest time when femoral head necrosis occurred was the twelfth month after the operation and the latest time was 26th month. Of the 6 patients, one was treated by core decompression of the femoral head and iliac bone graft transplanting, one was treated by total hip arthroplasty, the others by conservative therapy. There was no internal fixation failure or second fracture for all the patients. The Harris grading was used to evaluate the outcomes, the mean grade was 88.2 scores.Conclusion Closed reduction, cannulated screws fixation plus free iliac bone graft transplanting is a minimally invasive and easy operation method to treat femoral neck fractures, which has significant influences on the fracture healing and can reduce the incidence of femoral head necrosis. It provides an effective method to treat femoral neck fractures for the orthopedist.
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