| Objective(s):The aim of this study was to compare the biomechanical stability of 3 and 4 cannulated screw internal fixation in the treatment of PauwelsⅢ femoral neck fracture,and the influence on the on healing time,the incidence rate of avascular necrosis and nonunion with two different kinds of fixation.Methods:1.The study included 20 cadaver right femurs of adult randomly divided into two "groups(Group A had 12 cadaver right femurs while Group B had 8 cadaver right femurs).Samples in both two groups were osteotomized in the basicervical region to create Pauwels type-3 femoral neck fractures.Fixation was carried out using cannulated screws.In Group A,three screws were used in an inverted isosceles triangle configuration in parallel with the neck axis.In Group B,four screws were used ’including 3 in an inverted isosceles triangle configuration in parallel with the neck axis and the fourth screw transversely into the calcar.Load test was performed on two groups,and the strength of the screw fixations against axial load and their amount of relocation were be recorded.2.We collected 46 cases of patients with type Pauwels type-3 femoral neck fractures treated with this two methods in recent 5 years,of which there were a total of 21 cases used 3 srews configuration,and a total of 25 cases used 4.The incidence of complications(femoral head necrosis,nonunion),the Harris score of hip joint function and the average time of fracture healing.between the two groups were statistically analyzed.Results:1.Biomechanical test:Averrage maximum strength was 2020.46±146.74N in Group A(3 screws),2817.64 ± 163.97N in Group B(4 screws),P<0.05;Averrage maximum relocation was 10.88±1.47mm in Group A(3 screws)at the averrage maximum strength load,while 6.43± 0.62 mm in Group B(4 screws),P<0.05.2.Clinical efficacy:There were 46 cases were followed up for an average of 33.7(18-48)months.There were 2 cases(9.5%)of nonunion and 5(23.8%)cases of femoral head necrosis in Group 1(3 screws configuration),the average Harris hip score(HHS)was(85.1 ±9.0),and the average time of fracture healing in Group 1(except 3 cases of nonunion)was(4.2±1.3)months;there were 2(8.0%)cases of femoral head necrosis in Group 2(4screws configuration),no nonunion cases,the average Harris hip score was(89.6 + 3.2)points,and the average time of fracture healing in Group 2 was(4.2 + 1.3)months.There was no significant difference of complications(femoral head necrosis,nonunion)and Harris ’score between the two groups(P>0.05),but there was significant difference between the two groups(P<0.05)in the sum of complications and the average time of fracture healing.Conclusion(s):(1)The utilization of multiple can-nulated screws in closed reduction and internal fixation(CRIF)is an effective method for the treatment of Pauwels type-three femoral neck fractures,3 or 4 cannulated s-crew fixation can achieve better therapeutic effect.(2)4 cannulated screws fixation for the treatment of Pauwels type-three femoral neck fracture has stronger shear force effect than the 3 cannulated screws,and has stronger biomechanical stability.4 cannulated screws fixation has a lower rate of posto-perative complications and shorter fracture healing time than 3 cannu-lated screws. |
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