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[Related factor analysis of avascular necrosis of the femoral head after internal fixation with cannulated screws in femoral neck fractures].

OBJECTIVE
To observe the accident of avascular necrosis of the femoral head after internal fixation with cannulated screws in femoral neck fractures and analysis of the related factors.


METHODS
212 cases of femoral neck fracture treated with cannulated screws between Sep. 1989 and Dec. 1999 were reviewed retrospectively. The average age was 45.2 years old, ranging from 13 to 70 years. Among the fractures, 3 were Garden stage I, 32 were Garden stage II, 107 were Garden stage III, 53 were Garden stage IV, and 17 unclassified. Average duration of follow-up was 32.7 months, ranging from 12 to 101 months.


RESULTS
Fracture healing occurred in 203 cases (95.8%). Avascular necrosis of the femoral head occurred in 70 cases (33.0%) and late collapse developed in 30 cases (14.3%). The rate of the avascular necrosis and late collapse of the femoral head according to the Garden stage was 0/0, Garden stage I; 6.3%/0, Garden stage II; 33.6%/15.9%, Garden stage III; 49.1%/20.8%, Garden stage IV. Avascular necroses of the femoral head were observed within 3 years in most cases (95.7%). Correlation analysis shows Garden stage of the fracture was the major factor contributed to the accident of avascular necrosis and late collapse of the femoral head. It also shows the low risk of avascular necrosis and late collapse of the femoral head was related to the patient's age over 60; time of surgery within 14 days and Garden's reduction index within 155-180 degrees on both AP and Lateral views.


CONCLUSION
Garden stage of the fracture is the major factor contributed to the accident of avascular necrosis and late collapse of the femoral head, emergency operation and good reduction is beneficial to reduce the accident of avascular necrosis of femoral head.