Résumé
ObjectiveTo develop an EZ screw remover for screwing out the skidded screws,discuss its design features and biomechanical characteristics and verify its extracting effect by clinical applications.MethodsFresh skeleton specimens were used in the study,including the femur (n =3),tibia ( n =3 ),radius and ulna ( n =3 ).The screws were fixed to the specimens according to clinical requirements and bone cement was filled into the medullary cavity.The specimens were randomized into three biomechanical test model groups,ie,Group A (measuring the skidded screws with the biggest torsion when the screws were taken out by screwdriver),Group B (measuring the skidded screws with the biggest torsion when the screws were taken out by one handle of EZ screw remover) and Group C ( measuring the skidded screws with the biggest torsion when the screws were taken out by two handles).The fixed screws were divided into two types of φ4.5 mm and φ3.5 mm.The experimental specimens were tested on the universal testing machines to measure the maximum torque,torsion angle,power consumption value and efficiency when drawing out the screws. The experimental data were compared between groups.The skidded screws encountered in clinical were taken out with EZ screw remover to verify the extracting effect.ResultsThe pullout torque in Groups A,B and C was 2.87-3.27 N · m,3.06-4.83N · m and 4.12-8.36 N · m respectively ( P ＜ 0.05 ).The average torsion angle value in each corresponding group was 0.77°,0.28°,0.16° respectively (P ＜ 0.05 ).When the screws were screwed out,the average power consumption was 21 J,32 J and 45 J in Groups A,B and C respectively and power ( mechanical efficiency) was 0.35 J/s,0.53 J/s and 0.75J/s in Groups A,B and C respectively,with significant differences ( P ＜ 0.05 ).Seventeen pieces of the cannulated skidded screws of φ7.3 mm in seven patients were successfully taken out by using the EZ screw remover.ConclusionEZ screw removerhas enough resistance strength and rigidity to torsion as well as powerful clamping force and hence is an ideal tool for screwing out the skidded screw in orthopedics.
Résumé
Objective To discuss the clinical effect of dynamic hip screw(DHS)and microtrauma dynamic hip screw(MTDHS)in treatment of comminuted intertrochanteric femur fractures in the elderly patients.Methods From September 2006 to July 2009,42 patients with comminuted intertrochanteric femur fractures were treated by DHS and MTDHS.According to Evans classification,there were 16 patients with type Ⅲ fractures and six with type Ⅳ fractures in MTDHS group and 15 patients with type Ⅲ fractures and five with type Ⅳ fractures in DHS group.The operation time,amount of bleeding,hospital stay and postoperative hip function were evaluated.Results All patients were followed up for 9-17 months(average 13 months).Harris score was 76.4 points in 20 patients treated by DHS and 89.8 points in 22 patients treated by MTDHS,with better functional restoration,shorter operation time and less amount of bleeding in MTDHS group than DHS group.Conclusions Compared with DHS,MTDHS has advantages of minimal invasion,minor trauma,sound recovery of hip joint function and low incidence of complications and hence is a good choice for treating intertrochanteric femur fractures.