松质骨骨折不同位置螺钉固定效果的生物力学研究

Biomechanical study of screw fixation at different position in cancellous fracture

目的：分析松质骨骨折不同位置的固定效果。方法：成人防腐固定的股骨、胫骨标本各１５侧，测股骨髁部、胫骨踝部骨密度。摹拟股骨外侧髁和胫骨内踝骨折，于骨折面中心Ｏ 点、Ｏ 点正上方（ 近关节面）Ａ 点及正下方Ｂ 点旋入金属拉力螺钉，应用生物力学方法，测试螺钉最大轴向拔出力。结果：股骨髁部骨密度平均为０ ．３０ｇ／ｃｍ ２；踝部骨密度为０ ．４７ｇ／ｃｍ ２。股骨外侧髁骨折面Ａ、Ｏ、Ｂ 点螺钉的最大轴向拔出力分别为４０４ ．９Ｎ、２３３ ．８Ｎ 和１０５ ．２Ｎ。内踝骨折时，Ａ、Ｏ、Ｂ 点螺钉最大轴向拔出力分别为３３５ ．１Ｎ、１９３ ．１Ｎ、１４１ ．９Ｎ。Ｏ、Ａ 两点最大轴向拔出力的差异有显著性（Ｐ＜ ０ ．０５） ，Ａ、Ｂ 两点的差异非常显著（ Ｐ＜ ０ ．０１） 。结论：拔出力大小与螺钉固定位置有关。拉力螺钉固定松质骨骨折，进钉点应尽可能选择在骨折面中点或靠近关节面一侧。

To evaluate extraction force of screw fixation at different position in cancellous fracture. Methods:Fifteen embedded cadaveric femurs and tibias were used. The bone mineral density(BMD) was measured in condylus femoris and malleolus. Imitating condylus lateralis femoris fracture and medial malleolus fracture separately, screw was inserted from A、O、B point succesively and axial extraction forces were measured. Results:The BMD of condylus femoris averaged 0.30g/cm 2,and that of malleolus averaged 0.47g/cm 2.In condylus lateralis femoris fracture,the extraction force of A、O、B point were 404.9N,233.8N and 105.2N respectively. While in medial malleolus fracture, the data were 335.1N,193.1N and 141.9N separately. The difference between the extraction force of O point and that of A point was significant( P <0.05), and the difference between the extraction force of A point and that B point was Significant greatly ( p <0.01). Conclusions: Extraction force was relevant to screw position. In cancellous fracture, screw should better be inserted at the center point of the fracture plate or adjacent to articular surface.