Shetty Sameer, Nelson Brody, Knopp Brian, Schneppendahl Johannes, Kaufmann Robert A
Department of Orthopedics, University of Pittsburgh Medical Center, Bethel Park, PA.
Element Materials Technology, Fairfield, OH.
J Hand Surg Am. 2022 Oct;47(10):1014.e1-1014.e8. doi: 10.1016/j.jhsa.2021.07.037. Epub 2021 Sep 24.
The goal of this study was to test the pullout strength of intramedullary (IM) screws from within the humerus to establish their ability to seat an uncemented elbow arthroplasty.
Six humerus and 6 ulna Sawbones specimens were drilled with a drill bit diameter of 5/16 inches, and the inner cortex was hand tapped for a ⅜-16 thread. A ⅜-16 custom-made titanium screw with an outer bolt diameter of 3/8 inches and 16 threads per inch was inserted by hand into the tapped holes. The specimens were then axially tensile loaded at a rate of 5 mm per minute until either the screw began to pull out from the bone or a fracture was noted.
Intramedullary screw fixation in the humerus achieved an average pullout strength of 1,439 pound-force (6,401 N), and IM screw fixation in the ulna achieved an average pullout strength of 882 pound-force (3,923 N). A fracture was noted in 3 humeral specimens, with 3 screws pulling out. In the ulna, the IM axial load caused a fracture in 5 specimens, and in 1 specimen, the screw pulled out.
Our findings demonstrate that IM screw fixation can create a tensile force within the screw that is greater than that required to generate the calculated level of compression between the implant and bone.
This may be beneficial in ensuring fixation between arthroplasty components and bone.
本研究的目的是测试肱骨骨髓内（IM）螺钉的拔出强度，以确定其在非骨水泥型肘关节置换术中固定假体的能力。
对6个肱骨和6个尺骨Sawbones标本用直径5/16英寸的钻头钻孔，并用手攻丝在内侧皮质上形成3/8 - 16的螺纹。将一个外径为3/8英寸、每英寸16牙的定制3/8 - 16钛螺钉手动插入攻丝孔中。然后以每分钟5毫米的速度对标本进行轴向拉伸加载，直到螺钉开始从骨中拔出或出现骨折。
肱骨的髓内螺钉固定平均拔出强度为1439磅力（6401牛），尺骨的髓内螺钉固定平均拔出强度为882磅力（3923牛）。在3个肱骨标本中出现骨折，3个螺钉拔出。在尺骨中，髓内轴向载荷导致5个标本骨折，1个标本螺钉拔出。
我们的研究结果表明，髓内螺钉固定可在螺钉内产生大于在植入物与骨之间产生计算压缩水平所需的拉力。
这可能有助于确保关节置换部件与骨之间的固定。
