ABSTRACT
Objective:To investigate the biomechanical properties of cannulated screws fixation in a configuration of "axial compression and lateral buttress" in the treatment of Pauwels type Ⅱ femoral neck fractures.Methods:Ten specimens of Sawbones artificial femur were first made into models of type Ⅱ femoral neck fracture with a Pauwells angle of 50° and then randomized into 2 equal groups ( n=5). The specimens in the experimental group were subjected to fixation with cannulated screws in a configuration of "axial compression and lateral buttress" in which the axial screw was 8.5 mm in diameter and the lateral screw 6.5 mm in diameter. The specimens in the control group were subjected to conventional fixation with cannulated screws in a configuration of "inverted triangle and parallel compression" in which the 3 screws was 7.3 mm in diameter. Finally, the specimens were placed onto a biomechanical testing machine to determine the parameters of static axial stiffness, displacement under 60 to 600 N load for 5,000 cycles, ultimate load and ultimate stiffness in turn. The 2 groups were compared to find out their differences. Results:The static axial stiffness was (1,492.00 ± 87.86) N/mm, significantly higher than that in the control group [(1,200.22 ± 228.06) N/mm] ( P<0.05). There was no significant difference between the 2 groups in the cyclic load displacement [(0.44 ± 0.01) mm versus (0.57 ± 0.17) mm] ( P>0.05), but the experimental group showed a lower trend. The ultimate load and ultimate stiffness were (4,292.61 ± 804.29) N and (1,623.55 ± 180.94) N/mm in the experimental group and (4,383.64 ± 1,423.24) N and (1,433.77 ± 289.93) N/mm in the control group, showing no significant difference between the 2 groups ( P>0.05). Conclusion:In the treatment of Pauwels type Ⅱ femoral neck fractures, fixation with cannulated screws in a configuration of "axial compression and lateral buttress" may exhibit better biomechanical properties than that in a conventional configuration of "inverted triangle" .
ABSTRACT
PURPOSE: This study was performed to evaluate the risk factors affecting the failure of fixation and to analyze the clinical and radiologic results after operation with using a sliding hip screw for treating OTA type A2 intertrochanteric fractures of the femur. MATERIALS AND METHODS: From January 2001 to June 2005, we reviewed the clinical records and the serial radiographs of 53 patients (OTA type A2 intertrochanteric fractures of the femur) who were treated with a 135-degree angled sliding hip screw. We analyzed the change in the neck-shaft angle, the sliding distance and failure of the sliding screw, according to the reduction of the lesser trochanteric fragment and the stability of the lateral buttress. RESULTS: Among 53 patients, there were 15 cases (28.3%) of failures to reduce the lesser trochanteric fragment. Losses of the lateral buttress were observed in 35 cases (66.0%). There were 8 cases (15.1%, 8/15) that failed radiologically, including cutting out of the sliding hip screw from a femoral head (3 cases), metal failure (1 case) and excessive sliding (4 cases). There were significantly differences for the changes of the angle of the neck-shaft, the distance of sliding and the length of penetration of the sliding hip screw, according to the reduction of the lesser trochanteric fragment and the stability of the lateral buttress. CONCLUSION: It is important to consider the reduction of the lesser trochanteric fragment and the stability of lateral buttress when treating OTA type A2 intertrochanteric fractures with using a sliding hip screw.
Subject(s)
Humans , Femur , Head , Hip Fractures , Hip , Risk FactorsABSTRACT
PURPOSE: To investigate the effect of lateral buttress on the fracture healing of Jensen type 4 intertrochanteric fracture of the femur treated by dynamic compression hip screw (DCS) in elderly patients, retrospectively. MATERIALS AND METHODS: From March 1999 to February 2003, 54 patients, older than 65 years, of Jensen type 4 intertrochanteric fractures of the femur treated by DCS were included. The relationship between the structual integrity of lateral buttress measured by proximal-medial fragment angle (PMFA) and postoperative neck-shaft angle, penetrating length of lag screw, the sliding length and incidence of fixation loss were evaluated. RESULTS: Among 38 patients of group II (PMFA above 50 degree), 6 cases (15.8%) including 4 cases of cutting out of lag screw from femoral head, 1 case of nonunion and 1 case of excessive extrusion of lag screw failed radiologically. But there was no fixation loss case in 16 cases of group I (PMFA 50 and below 50). The neck-shaft angle in last follow-up was 138.1 degree in group I and 132.1 in group II. The sliding length of lag screw was 7.0 mm in group I and 12. 5 mm in group II (p<0.05). CONCLUSION: Preoperative evaluation of intactness of lateral buttress measured by proximal-medial fragmentary angle is an useful method in treatment of Jensen type 4 intertrochanteric fractures treated by DCS in elderly patients.