Edwards Sara L, Wilson Nicole A, Zhang Li-Qun, Flores Steven, Merk Bradley R
Department of Orthopaedic Surgery, Northwestern University, 645 North Michigan Avenue, Suite 910, Chicago, IL 60611, USA.
J Bone Joint Surg Am. 2006 Oct;88(10):2258-64. doi: 10.2106/JBJS.E.00757.
Successful internal fixation of fractures of the surgical neck of the humerus can be difficult to achieve because of osteopenia of the proximal aspect of the humerus. The purpose of this study was to compare the biomechanical stability of a proximal humeral intramedullary nail and a locking plate for the treatment of a comminuted two-part fracture of the surgical neck in a human cadaver model.
Twenty-four cadaveric humeri were instrumented with use of either a titanium proximal humeral nail (PHN) or a 3.5-mm locking compression plate for the proximal part of the humerus (LCP-PH). The specimens were matched by bone mineral density and were separated into four experimental groups with six humeri in each: PHN bending, LCP-PH bending, PHN torsion, or LCP-PH torsion. Comminuted fractures of the surgical neck were simulated by excising a 10-mm wedge of bone. Bending specimens were cyclically loaded from 0 to 7.5 Nm of varus bending moment at the fracture site. Torsion specimens were cyclically loaded to +/-2 Nm of axial torque. The mean and maximum displacement in bending, mean and maximum angular rotation in torsion, and stiffness of the bone-implant constructs were compared.
In bending, the LCP-PH group demonstrated significantly less mean displacement of the distal fragment than did the PHN group over 5000 cycles (p = 0.002). In torsion, the LCP-PH group demonstrated significantly less mean angular rotation than did the PHN group over 5000 cycles (p = 0.04). A significant number of specimens in the PHN group failed prior to reaching 5000 cycles (p = 0.04). The LCP-PH implant created a significantly stiffer bone-implant construct than did the PHN implant (p = 0.007).
The LCP proximal humeral plate demonstrated superior biomechanical characteristics compared with the proximal humeral nail when tested cyclically in both cantilevered varus bending and torsion. The rate of early failure of the proximal humeral nail could reflect the high moment transmitted to the locking proximal screw-bone interface in this implant.
The high failure rate in torsion of the proximal humeral nail-bone construct is concerning, and, with relatively osteoporotic bone and early motion, the results could be poor.
由于肱骨近端骨质减少，肱骨外科颈骨折的成功内固定可能难以实现。本研究的目的是在人体尸体模型中比较肱骨近端髓内钉和锁定钢板治疗肱骨外科颈粉碎性二部分骨折的生物力学稳定性。
使用钛制肱骨近端钉（PHN）或用于肱骨近端的3.5毫米锁定加压钢板（LCP-PH）对24具尸体肱骨进行器械固定。标本根据骨密度进行匹配，并分为四个实验组，每组六具肱骨：PHN弯曲、LCP-PH弯曲、PHN扭转或LCP-PH扭转。通过切除10毫米楔形骨来模拟外科颈的粉碎性骨折。对弯曲标本在骨折部位以0至7.5牛米的内翻弯矩进行循环加载。对扭转标本以+/-2牛米的轴向扭矩进行循环加载。比较了弯曲时的平均和最大位移、扭转时的平均和最大角旋转以及骨植入物结构的刚度。
在弯曲方面，LCP-PH组在5000次循环中远端骨折块的平均位移明显小于PHN组（p = 0.002）。在扭转方面，LCP-PH组在5000次循环中的平均角旋转明显小于PHN组（p = 0.04）。PHN组中有相当数量的标本在达到5000次循环之前就失效了（p = 0.04）。LCP-PH植入物产生的骨植入物结构比PHN植入物明显更硬（p = 0.007）。
在悬臂内翻弯曲和扭转试验中，LCP肱骨近端钢板的生物力学特性优于肱骨近端钉。肱骨近端钉的早期失败率可能反映了该植入物传递到锁定近端螺钉-骨界面的高力矩。
肱骨近端钉-骨结构在扭转时的高失败率令人担忧，并且在骨质相对疏松和早期活动的情况下，结果可能较差。
