Biomechanical Analysis In Using Different Internal Fixations For The Treatment Of Distal Femoral Fractures

Distal femoral fracture includes supracondylar femoral fracture, intercondylar femoral fracture and singular condyle fracture. It is a kind of injury of high energy and it is often led to immediate force or vertical compressive force. As comminuted fracture usually the reductions of distal femoral fracture are difficult and the effect is not satisfied. Complications are often appear after operations. With the development of biomechanics, all kinds of equipments in internal fixation are wide-ranging used in clinical therapy. But there are not unanimity of opinion in the choice of internal fixational equipments and clinical effect in A-type fracture of AO classification at home and abroad at present. And there are not connected reports about the different of adoption of DCS, interlocking intramedullary nailing, retrograde intramedullary nailing in A-type distal femoral fracture in biomechanics. This study will focus on DCS, interlocking intramedullary nailing and retrograde intramedullary nailing three different ways to deal with A-type distal femoral fracture and illumine which one is more suitable therapy to it in biomechanics. And we will compare the information of a large amount of cases of reports that DCS, interlocking intramedullary nailing and retrograde intramedullary nailing are used to treat this type of fracture at home and abroad. To provide confident scientific basis on which one is the most suitable treatment in A-type distal femoral fracture. [Objective] Distal femoral fracture is often led to immediate force or vertical compressive force to cause comminuted fracture and the reductions are difficult and dissatisfied. Now we can use all kinds of equipments to treat it, but there are no reports about the different of adoption of DCS, interlocking intramedullary nailing and retrograde intramedullary nailing in biomechanics. We will illumine which way is the most suitable to it in biomechanics and compare large cases reports that DCS, interlocking intramedullary nailing and retrograde intramedullary nailing are used to this type of fracture at home ang abroad so that we can provide scientific basis in the future to treat it. [Method] 6 pairs of femurs of adult cadavar soaked in formalin were used as the models of A-type slanting fracture of AO classification in the same standard. Retrograde intramedullary nailing fixed 3 left femurs in the first group, interlocking intramedullary nailing fixed 3 left femurs in the second group, DCS fixed 6 right femurs in both group. Under one-foot standing condition, these models were given 0-600N classifiable loads, by velocity of 1mm/min. Electric variable through farcture ends are measured and the outcome of biomechanics is analysised by statistical SAS software. Information about reports of a large amount of cases that DCS, interlocking intramedullary nailing and retrograde intramedullary nailing are used to treat this type of fracture at home and abroad is analyzed and compared. [Result] With the same load, the electric variable measurement of fracure end is the most remarkable in DCS groups and the least remarkable in the retrograde intramedullary nailing groups. Displacement is the most obvious in interlocking intramedullary nailing groups and the least obvious in DCS groups. The difference of electric variable and displacement caused by interlocking intramedullary nailing, retrograde intramedullary nailing and DCS is significant (p<0.01), but there is not statistical difference between them. The difference of electric variable measurement among four points varies as the following blank shows (3point >4point>2point>1point) with the same equipment, the variation is the most remarkable in DCS groups and the less in intramedullary nailing groups, the least in retrograde intramedullary nailing.groups. The electric variablemeasurement is the most remarkable in the internal-side of fracture end (3point) and rear-side (4point) with DCS, which is 3.59, 6.57 as much as with interlocking intramedullary nailing and 8.48,3.88 as much as with retrograde intramedullary nailing (p<0.01). The average electric variable of distal femoral outside (1point) is less than inside (3point). The compressive strength is the most remarkable in DCS and the least in interlocking intramedullary nailing. There is significant difference between with DCS and with interlocking intramedullary nailing, retrograde intramedullary nailing (p<0.01). [Discussion] In this study we find that the average electric variable is less in intramedullary nailing, so we can conclude that the retograde intramedullay nailing to the distal femoral fracture is more stable compared with the other groups. Displacement is also the most remarkable and the electric variable is least remarkable in the intramedullary nailing. This result tells us tha the fracture will be fixed by 6-intramedullary nailing can provide a better elasticity, strong fixation. If there is little steady in both fracure ends or the two fracure ends cannot contact tightly, the DCS fixation is better than intramedullary nailing. The difference about electric variable of 4 points which is more marked with DCS than with intramedullary nailing shows that axial centre fixed intramedullary nailing can provide better anti-bending strength. There is obvious eccentrical pressure in DCS groups and the pressure is centralized.in the same group. [Conclusion] Intramedullary nailing can provide axial fixation and a better elasticity through femoral axis in marrow cavity, so it is more appropriate to the biological fixation. Fixation with DCS has eccentrical pressure and pressure is much more centralized compared with Intramedullary nailing. But if the snapped ends cannot contact tightly, especially in the comminuted A-type distal femoral fracture, we consider that the fixation with DCS is stable. Compared with DCS in...