Abstract：
Background and Objectives: Intramedullary nailing of trochanteric fractures can be challenging and sometimes the clinical situation does not allow perfect implant positioning. The aim of this study was (1) to compare in human cadaveric femoral heads the biomechanical competence of two recently launched cephalic implants inserted in either an ideal (centre-centre) or less-ideal anterior off-centre position, and (2) to investigate the effect of bone cement augmentation on their fixation strength in the less-ideal position. Materials and Methods: Fourty-two paired human cadaveric femoral heads were assigned for pairwise implantation using either a TFNA helical blade or a TFNA screw as head element, implanted in either centre-centre or 7 mm anterior off-centre position. Next, seven paired specimens implanted in the off-centre position were augmented with bone cement. As a result, six study groups were created as follows: group 1 with a centre-centre positioned helical blade, paired with group 2 featuring a centre-centre screw, group 3 with an off-centre positioned helical blade, paired with group 4 featuring an off-centre screw, and group 5 with an off-centre positioned augmented helical blade, paired with group 6 featuring an off-centre augmented screw. All specimens were tested until failure under progressively increasing cyclic loading. Results: Stiffness was not significantly different among the study groups (p = 0.388). Varus deformation was significantly higher in group 4 versus group 6 (p = 0.026). Femoral head rotation was significantly higher in group 4 versus group 3 (p = 0.034), significantly lower in group 2 versus group 4 (p = 0.005), and significantly higher in group 4 versus group 6 (p = 0.007). Cycles to clinically relevant failure were 14,919 ± 4763 in group 1, 10,824 ± 5396 in group 2, 10,900 ± 3285 in group 3, 1382 ± 2701 in group 4, 25,811 ± 19,107 in group 5 and 17,817 ± 11,924 in group 6. Significantly higher number of cycles to failure were indicated for group 1 versus group 2 (p = 0.021), group 3 versus group 4 (p = 0.007), and in group 6 versus group 4 (p = 0.010). Conclusions: From a biomechanical perspective, proper centre-centre implant positioning in the femoral head is of utmost importance. In cases when this is not achievable in a clinical setting, a helical blade is more forgiving in the less ideal (anterior) malposition when compared to a screw, the latter revealing unacceptable low resistance to femoral head rotation and early failure. Cement augmentation of both off-centre implanted helical blade and screw head elements increases their resistance against failure; however, this effect might be redundant for helical blades and is highly unpredictable for screws.
摘要：
背景和目的：髓内钉治疗股骨转子骨折具有挑战性，有时临床情况不允许完美的植入物定位。这项研究的目的是（1）比较人尸体股骨头中插入理想（中心-中心）或不太理想的前偏心位置的两个最近启动的头部植入物的生物力学能力，（2）研究在不太理想的位置增强骨水泥对其固定强度的影响。材料和方法：使用TFNA螺旋刀片或TFNA螺钉作为头部元件，将四十二对人类尸体股骨头分配成对植入，植入在中心中心或7毫米前偏心位置。接下来,在偏心位置植入的7对标本增加了骨水泥。因此,六个研究组如下：第1组具有中心定位的螺旋叶片，与具有中心螺钉的第2组配对，具有偏心定位的螺旋叶片的第3组，与具有偏心螺钉的第4组配对，和第5组，具有偏心定位的增强螺旋叶片，与具有偏心增强螺钉的第6组配对。在逐渐增加的循环载荷下测试所有样品直至失效。结果：研究组之间的刚度没有显着差异（p=0.388）。第4组的内翻变形明显高于第6组（p=0.026）。第4组股骨头旋转明显高于第3组（p=0.034），第2组明显低于第4组（p=0.005），4组明显高于6组（p=0.007）。临床相关失败的周期在第1组中为14,919±4763，在第2组中为10,824±5396，在第3组中为10,900±3285，在第4组中为1382±2701，在第5组中为25,811±19,107，在第6组中为17,817±11,924。与第2组相比，第1组的失败周期数明显更高（p=0.021），第3组与第4组（p=0.007），第6组与第4组(p=0.010)。结论：从生物力学的角度来看，正确的中心-中心植入定位在股骨头是最重要的。如果这在临床环境中无法实现，与螺钉相比，螺旋刀片在较不理想的（前部）错位时更宽容，后者揭示了不可接受的低阻力股骨头旋转和早期失败。偏心植入的螺旋刀片和螺钉头元件的水泥增强增加了它们对失败的抵抗力；然而，这种影响可能是多余的螺旋叶片和是高度不可预测的螺钉。
