A Biomechanical Study Of Tibial Plateau Fracture Of Different Reduction Quality

Objective:Tibial plateau fracture is a intra-articular fractures.the incidence of fractures is 4.83% in total body fractures.If tibial plateau fracture was not treated properly, it often is result in more complications ,for example joint pain, malunion, joint stiffness, joint instability, traumatic arthritis etc.Tibial plateau fracture is often associated with joint surface collapse.Articular surface step-off of tibial plateau will increase the unit area pressure ,which speed up the wear of articular cartilage.If the wear of articular cartilage exceed articular cartilage regeneration capacity , it lead to traumatic arthritis which cause the joint dysfunction, which influence seriously life quality of patient.Experiments demonstrate that accurate reduction of fractures of the articular cartilage and strong fixed help to heal in the form of hyaline cartilage chondrocytes and to prevent cartilage degradation, to reduce the incidence of traumatic arthritis.But the acceptable degree of displacement of articular surface remains controversial.Brown pointed out that when the step-off of articular surface exceed 1. 5mm, the intra-articular pressure obviously change. when the step-off of articular surface is more than 3mm, the pressure significantly increase and fracture block of the step-off no longer contact the femoral condyle.Bai bo demonstrate that more than 4mm step-off of the articular surface can cause knee valgus angle, the contact pressure increased significantly.The objective of our study is to evaluate the effect of the normal lateral tibial plateau,fractures reduced quality for collapse 0mm, 1mm, 2mm, 3mm, 4mm, on biomechanical characters of tibiofemoral joint,such as contact area,mean contact pressure and peak contact pressure,at neutral position,with pressure sensitive film techniques.It will prescribe the most acceptable extent of collapse of tibial plateau and provide reference for clinical treatment of tibial plateau fracture and related diseases.Methods: six recent anti-corrosive specimens from the four Cadaver don't have bone diseases and anatomical variation,such as osteoporosis, arthritis, tuberculosis, cancer, traumatic arthritis etc,by visual observation and X-ray. Femur is amputated through 15cm above the knee and tibia and fibula is amputated through 20cm below the knee. The soft tissues such as skin, muscle, meniscus etc and the patella, except for the important ligaments and the ankle joint capsul,for example tibia and fibula interosseous membrane retention, knee lateral and internal collateral ligament were removed from specimens to maintain the stability of the knee.Anteroposterior diameter and transverse diameter of the lateral and internal tibial plateau with a vernier caliper. Sawing off the lateral tibial plateau along the vertical plane through the midpoint of the lateral tibial plateau lead to SchatzkerI fracture models.Cleavage fracture block is fixed with locking plate at the step-off 0mm,1mm,2mm,3mm,4mm by Pads of different thickness measuring,which form different quality of reduction of tibial plateau model.Proximal and proximal end of specimens is fixed by being inserted in to sleeve of fixture which keep legs natural straight position at vertical plane and coronal Plane.At room temperature 25 ~ 30°C, relative humidity of 35-80%,pressure sensitive film sealed with polyethylene membrane.The sealed pressure sensitive film is put into the knee and fixed.Everything is ready, Increasing load was applied through the Femur,at a rate of 25N/s,to the peak value of 700N and last for 1minute.The pressure sensitive film is removed after unloading and affixed to cardboard in turns for test brow-up of the C-chip. The change of the contact pressure and area in the tibiofemoral joint,were measured with the use of Fuji FDP-305E density meter and the FDP-306E pressure transducer, AutoCAD software which made in Japan.Every group of specimen carried out a biomechanical test in the turn of intact,collapse 0mm, 1mm, 2mm, 3mm, 4mm.The tested pressure sensitive film was divided into four quadrants named as"zoneof medial tibial plateau","zone of lateral tibial plateau","inner zone of lateral tibial plateau".Their contact area ,pressure and the position of touching location of tibiofemoral joint on the tibial plateau were measured and the data was analyzed to draw a conclusion.Results:1 Corresponding relationship between normal tibiofemoral joint at legs natural straight positionTouching location of tibioemoral joint on the tibial plateau:About 1/3 of the anteroposterior diameter of the tibial plateau;About 1/2 of the diameter of the lateral or medial tibial plateau by itself and near to Eminence2 Changes of contact area in each zone of the tibial plateau At the natural straight position of the knee ,with the development of the step-off,through the pressure sensitive film,we found that,the contact area in the zone of lateral tibial plateau tended to decrease;from 1 mm step-off,the value had displayed a statistical difference(p<0.05),reduced by about 25.8%.While the contact area in the zone of medial tibial plateau and inner zone of lateral tibial plateau tended to increase ;from 2 mm step-off,the value in the zone of medial tibial plateau had displayed a statistical difference(p<0.0 5), increased by about 10.63%;the value in the zone of inner zone of lateral tibial plateau hadn't displayed a statistical difference(p<0.05).Fracture block of collapse at this time is no longer contacts with the femoral condyle.3 Changes of contact pressure in each zone of the tibial plateau :At the natural straight position of the knee,with the development of the step-off,through the pressure sensitive film,we found that,the mean contact pressure and peak contact pressure in the zone of lateral tibial plateau,medial tibial plateau and inner of lateral tibial plateau tended to increase;from 1mm step-off,the value in the zone of lateral tibial plateau had displayed a statistical difference(p<0.05),the mean contact pressure and peak contact pressure increased by about 20.64% and 10.07% respectively;In the zone of medial tibial plateau,from 1mm step-off the value had displayed a statistical difference(p<0.05), the mean contact pressure and peak increased by about 25.27% and 27.10% respectively.From 1mm step-off,the value in inner zone of lateral tibial plateau had displayed a statistical difference(p<0.05),the mean contact pressure and peak contact pressure increased by about 20.91% and 23.22% respectively.Conclusion:1 In the lateral tibial split fractures,the reduction of poor quality of articular surface after operation can lead to many complications, especially traumatic arthritis, and influence the long-term knee function directly.2 After tibial plateau fractures,the step-off of the articular surface in the weight-bearing area led to increase Intra-articular pressure . From 1mm step-off,the value had displayed a statistical difference.So,If weight-bearing articular step-off is over 1mm ,open reduction surgery should be performed and reseted anatomic reduction as soon as possible .3 At the natural straight position of the knee, the femoral condyle contact tibial plateau in the front of the tibial plateau, different types of violence cause fracture of different types in the front of the tibial plateau.