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Objective To analyze the effect of different areas of paries medialis defect of femoral trochanter on the stability of fracture ends after percutaneous compression plating for femoral intertrochanteric fracture.Methods Thirteen preserved cadaveric specimens of adult femur were used in this experiment.The age of death ranged from 30 to 50 years.Oblique osteotomy was conducted under the same condition using a wire saw to create experimental models of fracture of Evans-Jensen type Ⅳ.The ratios of the area of paries medialis defect to the projected area of lesser trochanter in the specimens 1 to 13 were set respectively as 0,10.0％,14.5％,20.2％,23.4％,30.6％,45.8％,56.8％,76.8％,88.7％,99.8％,121.3％ and 149.4％.All the fractures were fixated by standard percutaneous compression plating.Cyclic load was applied on each specimen using Instron 2000 universal material tester.A vertical load of 600 N was applied for respectively 1,10,100 and 1,000 times to measure the displacements of proximal and distal fracture ends.Results When the ratio of the area of paries medialis defect to the projected area of lesser trochanter was 30.6％,the average displacements of the proximal and distal ends were 0.14 cm and 0.10 cm.When the ratio was 45.8％,the average displacement of the proximal end was 0.53 cm,278.6％ greater than that for 30.6％;the average displacement of the distal end was 0.41 cm,310.0％ greater than that for 30.6％.When the ratio was 149.4％,the average displacement of the proximal end was 0.93 cm,564.3％ greater than that for 30.6％;the average displacement of the distal end was 0.65 cm,550.0％ greater than that for 30.6％.Conclusions When the ratio of the area of paries medialis defect to the projected area of lesser trochanter reaches ＞ 45.8％,the area of paries medialis defect will have a significant effect on the stability of fracture ends after percutaneous compression plating for femoral intertrochanteric fracture.The displacement will increase linearly under the same compression with the increase in defect area.
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BACKGROUND:Traditional studies on foot and ankle biomechanics have limitation. Ankle joint was complicated and had big range of motion, so it is difficult to establish finite element models and to analyze the type of fracture. OBJECTIVE: To construct the finite element models of distal tibial fractures and analyze the stability. METHODS: CT data of ankle were colected from a normal male volunteer and the three-dimensional reconstruction of volunteer was made by Mimics software, and the effectiveness was verified. The ratio of different joint involvement and height of fracture block were assumed with Solidwork software, and finite element models of distal tibial fractures were established. Fracture stability was analyzed by ANSYS software using finite element method. RESULTS AND CONCLUSION:The distal tibia fracture model was consistent with the relevant literature data, and finite element analysis could be further conducted. The ratio of articular surface involved was positively associated with fragment height and fracture displacement, and negatively associated with fracture stability. These results indicate that the three-dimensional finite element models of distal tibial fractures were successfuly established. Fracture stability was associated with the ratio of articular surface involved and fragment height.
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Objective To investigate the initial effect of LARS artificial ligaments arthroscopically in reconstruction of ipsilateral anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL).Methods A total of 21 patients (13 males and 8 females,at average age of 31.5 years) received ACL and PCL restoration using LARS artificial ligaments since June 2006.Preoperative MRI exactly confirmed them as ACL and PCL ruptures.Lysholm score on knee joint was (47.6 ±6.7) points.Surgery had reconstruction of PCL prior to ACL under arthroscope.Results All patients were followed up for average 42 months (range,36-49 months),which showed no infection,ligament rupture,ligament loosening,or other postoperative complications.At postoperative 3 years,Lysholm score was (90.8 ± 3.7) points and International Knee Documentation Committee (IKDC) score was normal in 14 patients,near normal in six,and abnormal in one,with excellent-good rate of 95％.Conclusions LARS artificial ligaments can attain anatomical reconstruction and stability of the knee joint in treatment of ACL and PCL ruptures.Meanwhile,arthroscopic surgery shows superiorities of micro-wound,rapid recovery and satisfactory curative effect.