Strauss Eric J, Pahk Brian, Kummer Frederick J, Egol Kenneth
Department of Orthopaedic Surgery, NYU-Hospital for Joint Diseases, New York, New York 10003, USA.
J Orthop Trauma. 2007 May;21(5):295-300. doi: 10.1097/BOT.0b013e3180616ba5.
To determine the effect of reinforced calcium phosphate cement augmentation of the femoral neck defect created after dynamic hip screw removal in a cadaveric model.
The lag screws of dynamic hip screw implants were inserted and subsequently removed in 8 matched pairs of cadaveric, osteoporotic femurs to create a femoral neck defect. One of each pair had the defect augmented with osteoconductive calcium phosphate cement reinforced with poly(lactide-coglycolide) fibers (Norian Reinforced, Synthes, West Chester, PA), and the other defect was not augmented. Each specimen was first cyclically loaded with 750 N vertical loads applied for 1000 cycles to simulate early weightbearing, and then loaded to failure.
Calcium phosphate cement augmentation of the lag screw defect significantly increased the mean femoral neck failure strength (4819 N) compared to specimens in which the defect was left untreated (3995 N) (P < 0.004). The mechanism of failure for each specimen was a fracture through the femoral neck. Regression analysis demonstrated that load to failure was directly related to the bone mineral density at Ward's triangle, and the impact of cement augmentation on failure strength was greatest for specimens with the lowest bone mineral density (correlation coefficient: -0.82, P < 0.0001).
This study demonstrates that augmentation of the bony defect created by dynamic hip screw removal with reinforced calcium phosphate cement significantly improved the failure strength of the bone. Cement augmentation after hardware removal may decrease the risk of refracture and allow early weightbearing, especially in elderly patients with osteoporotic bone.
在尸体模型中确定聚（丙交酯 - 乙交酯）纤维增强磷酸钙骨水泥对动力髋螺钉取出后股骨颈缺损的增强效果。
在8对匹配的尸体骨质疏松股骨中插入并随后取出动力髋螺钉植入物的拉力螺钉，以制造股骨颈缺损。每对中的一个缺损用聚（丙交酯 - 乙交酯）纤维增强的骨传导性磷酸钙骨水泥（Norian Reinforced，Synthes，韦斯特切斯特，宾夕法尼亚州）增强，另一个缺损不进行增强。每个标本首先承受750 N垂直载荷循环加载1000次以模拟早期负重，然后加载至破坏。
与未处理缺损的标本相比，拉力螺钉缺损用磷酸钙骨水泥增强显著提高了股骨颈平均破坏强度（4819 N）（3995 N）（P < 0.004）。每个标本的破坏机制均为股骨颈骨折。回归分析表明，破坏载荷与沃德三角区的骨密度直接相关，对于骨密度最低的标本，骨水泥增强对破坏强度的影响最大（相关系数： - 0.82，P < 0.0001）。
本研究表明，用增强型磷酸钙骨水泥增强动力髋螺钉取出后造成的骨缺损可显著提高骨的破坏强度。取出内固定后使用骨水泥增强可能会降低再骨折风险并允许早期负重，尤其是在患有骨质疏松性骨的老年患者中。
