Ahmad M, Nanda R, Bajwa A S, Candal-Couto J, Green S, Hui A C
Orthopaedic Department, James Cook University Hospital, Middlesbrough TS4 3BW, Cleveland, UK.
Injury. 2007 Mar;38(3):358-64. doi: 10.1016/j.injury.2006.08.058. Epub 2007 Feb 12.
To investigate in vitro the mechanical stability of a locking compression plate (LCP) construct in a simulated diaphyseal fracture of the humerus at increasing distances between the plate and bone.
A series of biomechanical in vitro experiments were performed using composite humerus sawbone as the bone model. Osteotomy created in the mid-diaphyseal region. A 10mm osteotomy gap was bridged with a seven-hole 4.5 stainless steel plate with one of four methods: a control group consisted of a dynamic compression plate applied flush to the bone and three study groups which comprised of a LCP applied flush to the bone, at 2mm and at 5mm from the bone. Standard AO technique used with locking head screws used for LCP fixation. Static and dynamic loading tests performed in a custom made jig in which the bone model was fixed both proximally and distally. Samples were subjected to cyclical compression, compression load to failure, cyclical torque and torque to failure. Plastic deformation and failure was assessed using three-dimensional measurements. Scanning electron microscopy of the plate and screw surface allowed detailed inspection of micro-fracture in areas of fatigue.
Comparable results were achieved in both the DCP and LCP constructs in which the plate was applied at or less than 2mm from the bone. When applied 5mm from the bone the LCP demonstrated significantly increased plastic deformation during cyclical compression and required lower loads to induce construct failure.
At a distance 5 mm we observe an inferior performance in the mechanical properties of the LCP construct with decrease in axial stiffness and torsional rigidity. If it is desirable for an LCP to be used the distance between plate and bone should be <or=2 mm.
在体外研究锁定加压钢板（LCP）在模拟肱骨干骨折中，钢板与骨骼间距增加时的力学稳定性。
使用复合肱骨锯骨作为骨模型进行一系列体外生物力学实验。在骨干中部区域进行截骨术。用一块七孔4.5不锈钢钢板以四种方法之一桥接10mm的截骨间隙：对照组为将动力加压钢板紧贴骨骼放置，三个研究组分别为将LCP紧贴骨骼放置、与骨骼相距2mm放置以及与骨骼相距5mm放置。LCP固定采用标准AO技术并使用锁定头螺钉。在定制夹具中进行静态和动态加载测试，其中骨模型在近端和远端均被固定。对样本施加循环压缩、压缩至破坏的载荷、循环扭矩以及扭矩至破坏。使用三维测量评估塑性变形和破坏情况。对钢板和螺钉表面进行扫描电子显微镜检查，以便详细观察疲劳区域的微骨折情况。
当钢板与骨骼的距离在2mm及以内时，DCP和LCP结构均取得了可比的结果。当钢板与骨骼相距5mm放置时，LCP在循环压缩过程中表现出明显增加的塑性变形，并且诱导结构破坏所需的载荷更低。
在相距5mm时，我们观察到LCP结构的力学性能较差，轴向刚度和扭转刚度均下降。如果希望使用LCP，则钢板与骨骼之间的距离应≤2mm。
