Experimental and Theoretical Investigation of Static and Dynamic Bending Properties of Intramedullary Nails

Year 2019, , 595 - 606, 31.08.2019

Halim Kovacı

https://doi.org/10.18185/erzifbed.454431

Abstract

The greatest expectation from
intramedullary nails, which are used in the treatment of long bones by placing
in the bone marrow, is that they cannot be damaged during bone healing and
allow the adequate load distribution. There are many different kind of commercially
available intramedullary nails and also, one of the mostly used types of this
nails are hollow nails. Also, static and fatigue bending loads are taken into
account in different international biomechanical test standards, which refers
the worst-case working conditions. However, the intramedullary nails produced
in hollow form are not known to change their properties under these loads due
to the change in cross-sectional thickness. Therefore, the effects of
cross-sectional thickness in intramedullary nails on their static and fatigue
properties were investigated in this study. For this purpose, the hollow
intramedullary nails manufactured from Grade 23 Ti6Al4V ELI with thicknesses of
6.2, 6.7 and 7.2 mm were subjected to static four-point bending and fatigue
tests. After tests, it was observed that both static and fatigue strengths of
nails improved with increasing cross-sectional thickness. Also, it was
determined that a mathematical model to be used in the design process of nails
can be established by using static four-point bending tests results and
theoretical results. Additionally, it was observed that there wasn’t a direct
proportion between increasing cross-sectional thickness and increase rate of
fatigue strength although fatigue properties of intramedullary nails improved
when its cross-sectional thickness increased.

İntramedüller Çivilerin Statik ve Dinamik Eğilme Özelliklerinin Deneysel ve Teorik Olarak İncelenmesi

Abstract

Kemik iliği içerisine
yerleştirilerek uzun kemiklerin tedavisinde kullanılan intramedüller çivilerden
en büyük beklenti kemik iyileşmesi süresince hasara uğramamaları ve yeterli yük
dağılımına olanak sağlamalarıdır. Ticari olarak farklı pek çok türde
intramedüller çivi olmakla birlikte bu çiviler içerisinde en çok kullanılan
türlerden biri silindirik kesitli içi boş olan türleridir. Ayrıca,
intramedüller çivilerin en kötü koşullarda çalışmasını referans alan birçok
uluslararası biyomekanik test standardında statik ve dinamik eğilme yükleri
dikkate alınmaktadır. Ancak, içi boş şekilde üretilen intramedüller çivilerin,
kesit kalınlığının değişimi sebebi ile bu yükler altında özelliklerinin ne
yönde değişeceği bilinmemektedir. Bu sebeple, bu çalışmada, intramedüller
çivilerde kesit etkisinin intramedüller çivilerinin statik ve yorulma
dayanımları üzerindeki etkileri incelenmiştir. Bu amaçla, Grade 23 Ti6Al4V ELI
malzemeden imal edilen 6.2, 6.7 ve 7.2 mm kesit kalınlığına sahip içi boş
geometrideki intramedüller çiviler statik dört noktadan eğme ve yorulma
testlerine tabii tutulmuşlar. Testler sonrasında, intramedüller çivilerde kesit
kalınlığı arttıkça hem statik hem de yorulma dayanımlarının arttığı
belirlenmiştir. Bununla birlikte, statik dört noktadan eğilme deneyleri
sonucunda elde edilen sonuçlar ile teorik olarak hesaplanan değerler kullanılarak;
intramedüller çivilerin tasarımı aşamasında kullanılabilecek matematiksel bir
model oluşturulabileceği belirlenmiştir. Ayrıca, intramedüller çivilerde kesit
kalınlığı arttıkça yorulma dayanımının da arttığı ancak artan kesit
kalınlığındaki artış oranı ile yorulma dayanımındaki artışın doğru orantılı
olmadığı gözlemlenmiştir.

Keywords

İntramedüller çivi, biyomekanik, eğilme, dört noktadan eğme, yorulma

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