Effect of different combination of locking compression plate's holes and screw on the axial micromotion of fracture site / 中华创伤杂志

ABSTRACT

Objective:To investigate the effect of different screw and screw hole combination of locking compression plates (LCP) on axial micromotion of fracture ends.Methods:Eighteen mature male New Zealand white rabbits were enrollled and divided into Groups A, B and C according to the random number table method, with six rabbits in each group. After obtaining the whole fresh right tibial specimens, the tibia was cut off transversely at the middle part and fixed with LCP. All specimens were fixed with locking screws in locking holes at the distal side of the fracture end. In Group A, locking screws were fixed in locking holes at proximal end. In Group B, common screws were fixed in locking holes at proximal end. While in Group C, common screws were fixed in compression holes at proximal end. All specimens were subjected to a dynamic axial load of 0-50 N on a universal test machine. The distance of the micromotion of the fracture site was measured and axial compression stiffness corresponding to each fixing method was calculated through the instrument's own system.Results:All specimens generated corresponding axial displacement under the axial load. Under an axial load that approximated a body weight (25 N), the axial displacement value of the fracture end was (0.101±0.017)mm in Group A, (0.164±0.007)mm in Group B, and (0.305±0.041)mm in Group C. Under the axial load of approximately two body weights (50 N), the axial displacement value of the fracture end was (0.218±0.012)mm in Group A, (0.285±0.013)mm in Group B, and (0.513±0.051)mm in Group C. Under the same load, the average axial displacement value of fracture site was Group C>Group B>Group A ( P<0.01). The axial stiffness of LCP device was (234.36±13.28)N/mm in Group A, (203.78±16.46)N/mm in Group B, and (112.62±16.23)N/mm in Group C, namely Group A>Group B>Group C ( P<0.01). Conclusion:LCP fixed with common screws or via compression holes can significantly increase axial micromotion of the fracture end. While the combined application of the two methods has better effect and can reduce the stiffness of LCP device.