ABSTRACT
Objective To investigate biomechanical properties of the patella tension plating system in order to provide a theoretical basis for its clinical application. Methods Thirty-six models of artificial patella were randomly divided into 3 groups ( n=12 ) . After transverse patellar fractures were created in the models, the 3 groups were subjected to fixation respectively with Kirschner wire tension band ( tension band group ) , patellar concentrator ( concentrator group ) and patellar tension plate ( tension plate group ) . Next, 6 specimens from each group were placed on a mechanical testing machine to measure the fracture displacements after 100 cycles of simulated knee flexion and extension movements. Tensile strength tests were performed on the remaining 6 specimens in each group to measure the maximum load at fixation failure. Results The fracture displacement in the tension plate group ( 0. 40 ± 0. 26 mm ) was significantly smaller than those in the tension band group ( 2. 58 ± 0. 72 mm ) and in the concentrator group ( 1. 25 ± 0. 74 mm ) ( P < 0. 05 );the maximum load at fixation failure in the tension plate group ( 1 , 709 ± 206 N ) was significantly greater than those in the tension band group ( 581 ± 122 N ) and in the concentrator group ( 1, 003 ± 211 N ) ( P <0. 05 ) . Conclusion As a new treatment for patellar fractures, the patellar tension plating system can perform better in biomechanical properties than Kirschner wire tension band and patellar concentrator.
ABSTRACT
Objective To assess the biomechanical stability and vertebra strain distribution of asymmetrical posterior internal fixation for minimally invasive transforaminal lumbar interbody fusion ( MI-TLIF) . Methods Range of motion ( ROM) and strain distribution testing were performed in 8 fresh-frozen calf lumbar spine motion segments in flexion/extension, lateral bending, and axial rotation using 5. 0 Nm torques at the L4-5 motion segment. The sequential test configurations included intact motion segment, TLIF with unilateral pedicle screw ( UPS) , TLIF with UPS plus transfacet pedicle screws ( UPS+TFPS) , and TLIF with bilateral pedicle screw ( BPS) . The ROM was deter-mined to assess the construct stability. Strain distribution was recorded along with flexion and lateral bending configurations. Results In flexion/extension, lateral bending, and axial rotation, there was no significant difference in the ROM between BPS and UPS+TFPS fixation after TLIF. After TLIF, the UPS construct provided less segment stability than BPS and UPS+TFPS fixation in flexion, lateral bending. Strain distribution under UPS+TFPS fixation was respectively 21. 8% and 24. 2% higher than that under BPS fixation along with flexion and lateral bending. Conclusion UPS+TFPS fixation provides stability comparable to that of MI-TLIF with bilateral PS, with better load share with the vertebrae body.
ABSTRACT
External fixators have been widely u sed in treatment of war trauma due to t heir small size,light weight,easy application,and convenience in transport.There are several types of military external fixato r,such as FESSA(Fixateur Externe du Service de Sant?des Arm?es),CMC(Croatian Medical Corps),Synthes and Hoffman-Ⅱ.All of these have been used on the battlefields of Rwandese War,Croatia Wa r and the first Persian Gulf War.Most of military external fixators are unilateral connectable-joint.For temp orary fixation,one bar is enough;by adding another parallel bar,the fixation can be use d for long-time fixing.Facing with a great demand of war trauma treatment ,we should develop new types of military external fixator with more simplicity and less size or weight. [