McKnight R Randall, Lee Steve K, Gaston R Glenn
Department of Orthopaedic Surgery, Carolinas Medical Center, Charlotte, NC.
Department of Hand and Upper Extremity Surgery, Hospital for Special Surgery, New York, NY.
J Hand Surg Am. 2019 Jun;44(6):520.e1-520.e9. doi: 10.1016/j.jhsa.2018.08.017. Epub 2018 Oct 18.
Nitinol memory compression staples are a recent addition to carpal bone fixation. Compared with traditional staples, they have been shown to have superior compression at the far cortex relative to standard and traditional compression staples. The purpose of this study was to (1) determine the effective leg length of different nitinol staples, (2) confirm the effect of 1 versus 2 staples on biomechanical compression, and (3) determine the effect of troughing (countersinking the staple into bone) the bone on staple biomechanical properties.
Three commonly used nitinol staples of various bridge and leg lengths were used in a bicortical sawbones block construct. There were 3 separate constructs tested, which included single staple, double staple, and troughed. We measured compression force, stiffness, and bending strength for each construct before and after cyclical 4-point bending. Compression mapping was used to determine the effective leg length of each staple, which included the distance that compression extended beyond the tips of the staple legs.
Effective leg length for each staple construct extended 2 mm distal to the tip of the shortest staple leg. Two staple constructs more than doubled compressive force and increased bending strength by greater than 90% in all staple types. There was no loss of compressive force before or after loading for single, double, or troughed constructs with any staple type.
This study supports that nitinol staples do not have to be placed bicortically to achieve adequate compression; placing staples 2 mm short of the far cortex has the same compression as bicortical placement; and troughing of the bone will not significantly diminish the biomechanical properties of the construct.
Better understanding of the effective leg length of nitinol staples provides support that bicortical placement is not necessary for adequate compression. This study supports troughing bone to minimize implant prominence.
镍钛诺记忆加压钉是腕骨固定领域的新成员。与传统钉相比，相对于标准和传统加压钉，它们在远侧皮质处具有更强的加压效果。本研究的目的是：（1）确定不同镍钛诺钉的有效钉腿长度；（2）确认单枚与两枚钉对生物力学加压的影响；（3）确定在骨上开槽（将钉沉入骨中）对钉生物力学性能的影响。
在双皮质锯骨块结构中使用三种常用的不同桥长和钉腿长度的镍钛诺钉。测试了3种独立的结构，包括单枚钉、双枚钉和开槽结构。在进行周期性四点弯曲之前和之后，我们测量了每种结构的压缩力、刚度和抗弯强度。使用压缩映射来确定每枚钉的有效钉腿长度，这包括压缩超出钉腿尖端的距离。
每种钉结构的有效钉腿长度在最短钉腿尖端向远侧延伸2毫米。在所有钉类型中，双枚钉结构的压缩力增加了一倍多，抗弯强度提高了90%以上。对于任何钉类型的单枚、双枚或开槽结构，加载前后压缩力均无损失。
本研究支持镍钛诺钉不必双皮质放置即可实现充分加压；在距远侧皮质短2毫米处放置钉子与双皮质放置具有相同的加压效果；在骨上开槽不会显著降低结构的生物力学性能。
更好地了解镍钛诺钉的有效钉腿长度为充分加压不必双皮质放置提供了支持。本研究支持在骨上开槽以尽量减少植入物突出。
