Foruria Antonio M, Carrascal Maria Teresa, Revilla Carlos, Munuera Luis, Sanchez-Sotelo Joaquin
Departamento de Traumatología y Cirugía Ortopédica, Hospital La Paz, Madrid, Spain.
Clin Biomech (Bristol). 2010 May;25(4):307-11. doi: 10.1016/j.clinbiomech.2010.01.009. Epub 2010 Feb 13.
Fixed-angle locked devices have been developed to improve internal fixation of proximal humerus fractures. Available low-profile precontoured locking plates and intramedullary nails with fixed-angle interlocks are currently favored by most surgeons in this setting. The aim of this study was to assess the relative stability of these two methods of fixation under torsion load.
A surgical neck osteotomy was created in six pairs of embalmed humeri. In each pair, one specimen was secured with a titanium locking-compression plate, and the contralateral was secured with a titanium nail with a proximal locked spiral blade. The specimens were first tested cyclically in internal-external rotation for 10,000 cycles to evaluate interfragmentary motion (dynamic study). At the end of the cyclic testing, the specimens were loaded to failure in external rotation to measure torque to failure and construct stiffness (static study).
There were no significant differences in interfragmentary motion between the two fixation devices in the dynamic study. When tested to failure, fixation with the locking plate tolerated on average 20 more degrees in torsion before failure, and demonstrated higher torsional load to failure and less torsional stiffness (P<0.05).
Both locking plates and locked intramedullary nails may provide enough stability to avoid secondary displacement of proximal humerus fractures during early physical therapy. Locking plates demonstrated superior biomechanical properties under high rotational loads than locked intramedullary nails in a cadaveric proximal humerus two-part osteotomy model, and could provide more protection against unexpected high torsion loads.
为改善肱骨近端骨折的内固定，已研发出固定角度锁定装置。目前，大多数外科医生在此情况下更青睐现有的低轮廓预塑形锁定钢板和带固定角度互锁的髓内钉。本研究旨在评估这两种固定方法在扭转载荷下的相对稳定性。
在六对防腐处理的肱骨上制造外科颈截骨术。每对中，一个标本用钛锁定加压钢板固定，对侧用带近端锁定螺旋刀片的钛钉固定。标本首先在内-外旋转方向上进行10000次循环测试，以评估骨折块间的运动（动态研究）。在循环测试结束时，将标本在外旋方向加载至失效，以测量失效扭矩并构建刚度（静态研究）。
在动态研究中，两种固定装置在骨折块间运动方面无显著差异。在测试至失效时，锁定钢板固定在失效前平均能耐受多20度的扭转，且显示出更高的失效扭转载荷和更低的扭转刚度（P<0.05）。
锁定钢板和锁定髓内钉均可提供足够的稳定性，以避免肱骨近端骨折在早期物理治疗期间发生二次移位。在尸体肱骨近端两部分截骨模型中，锁定钢板在高旋转载荷下比锁定髓内钉表现出更好的生物力学性能，并且能为抵御意外的高扭转载荷提供更多保护。
