Guichet J M, Casar R S
Department of Bioengineering, Hospital for Joint Diseases Orthopaedic Institute, New York, NY, USA.
Clin Orthop Relat Res. 1997 Apr(337):281-90. doi: 10.1097/00003086-199704000-00032.
An intramedullary gradual elongation nail (Albizzia) capable of fulfilling the function of traditional intramedullary nails while providing the gradual, controlled distraction of an external fixator was designed for progressive lengthening of lower limbs. In this study, the biomechanics of the gradual elongation nail were compared with several intramedullary nails: Grosse & Kempf, Russell-Taylor, AO, and Laffay. Bending stiffness, torsional stiffness, ultimate bending strength, and torsional strength were determined using the American Society for Testing and Materials standard F383-73 as a guide. The results show that in unextended and elongated conditions, the gradual elongation nail has torsional stiffness (1-5 Nm2) comparable with the AO nail (2 Nm2) and bending stiffness (41-89 Nm2), ultimate bending (246 Nm), and torsional (28-37 Nm) strengths within the ranges obtained for other intramedullary nails (27-105 Nm2, 167-298 Nm, and 2-100 Nm, respectively). Additionally, the low torque required to lengthen the device under a 500 N load (3 Nm) and the low longitudinal stiffness because of the active dynamization system with bimodal load deformation characteristics (80-120 N/mm initial, 600-800 N/mm secondary) produce a device with almost no torsional and longitudinal stress shielding. From a biomechanical point of view, this single, completely implantable device is a safe, viable, and efficacious alternative to external fixation for progressive lengthening of lower limbs.
一种能够实现传统髓内钉功能，同时提供外固定器逐渐、可控牵张作用的髓内渐进延长钉（合欢树钉）被设计用于下肢的渐进性延长。在本研究中，将渐进延长钉的生物力学性能与几种髓内钉进行了比较：格罗斯&肯普夫髓内钉、拉塞尔 - 泰勒髓内钉、AO髓内钉和拉费髓内钉。以美国材料与试验协会标准F383 - 73为指导，测定了弯曲刚度、扭转刚度、极限弯曲强度和扭转强度。结果表明，在未延长和延长状态下，渐进延长钉的扭转刚度（1 - 5 N·m²）与AO髓内钉（2 N·m²）相当，弯曲刚度（41 - 89 N·m²）、极限弯曲强度（246 N·m）和扭转强度（28 - 37 N·m）在其他髓内钉所测得的范围内（分别为27 - 105 N·m²、167 - 298 N·m和2 - 100 N·m）。此外，在500 N载荷下延长该装置所需的低扭矩（3 N·m）以及由于具有双峰载荷变形特性的主动动力化系统导致的低纵向刚度（初始80 - 120 N/mm，二次600 - 800 N/mm）使得该装置几乎没有扭转和纵向应力遮挡。从生物力学角度来看，这种单一的、完全可植入的装置是下肢渐进性延长外固定的一种安全、可行且有效的替代方案。
