Seebeck J, Goldhahn J, Städele H, Messmer P, Morlock M M, Schneider E
AO Research Institute, Davos, Clavadelerstrasse, CH-7270 Davos Platz, Switzerland.
J Orthop Res. 2004 Nov;22(6):1237-42. doi: 10.1016/j.orthres.2004.04.001.
Internal fixators are a new class of implants designed to preserve the periosteal blood supply of the bone. In contrast to conventional plate fixation in which the screws have spherical heads and are loaded mainly by axial pullout forces, screws in internal fixators are "locked" within the plate and therefore subjected to axial as well as bending loads. In this study the ultimate loads of screws of a commercially available internal fixator system were tested in a pullout (n = 72) and cantilever bending mode (n = 72) in metaphyseal and diaphyseal regions of four pairs of human tibiae with different bone qualities. Cortical thickness and cancellous bone density were determined at the screw insertion sites. Stepwise multiple linear regression revealed that cortical thickness and cancellous density can explain 93% and 98% of the variance of the ultimate load of the screws in an axial pullout and cantilever bending mode. Screws in internal fixators are better suited to transmit shear forces and thereby make better use of the strength potential of bone than screws used in conventional plate fixation: this is especially advantageous when bone strength is reduced, e.g. due to osteoporosis.
内固定器是一类新型植入物，旨在保留骨膜的血液供应。与传统钢板固定不同，传统钢板固定中的螺钉头部为球形，主要承受轴向拔出力，而内固定器中的螺钉“锁定”在钢板内，因此承受轴向和弯曲载荷。在本研究中，在四对具有不同骨质的人体胫骨的干骺端和骨干区域，以拔出试验（n = 72）和悬臂弯曲试验（n = 72）对一种市售内固定器系统的螺钉极限载荷进行了测试。测定了螺钉植入部位的皮质厚度和松质骨密度。逐步多元线性回归显示，在轴向拔出和悬臂弯曲模式下，皮质厚度和松质骨密度可分别解释螺钉极限载荷方差的93%和98%。与传统钢板固定中使用的螺钉相比，内固定器中的螺钉更适合传递剪切力，从而能更好地利用骨的强度潜力：当骨强度降低时，如由于骨质疏松症，这一点尤为有利。
