Fixation of femoral neck fractures with three cannulated screws: biomechanical changes at critical fracture angles

Year 2020, Volume: 4 Issue: 8, 660 - 663, 01.08.2020

Kerim Öner Ahmet Emre Paksoy Alaettin Özer

https://doi.org/10.28982/josam.780442

Cited By: 1

Abstract

Aim: Increased fracture angle in the coronal plane results in more instability and complications in femoral neck fractures. Our aim in this study was to analyze biomechanical changes at critical fracture angles (30 degrees, 50 degrees, and 70 degrees) as described in Pauwels classification.
Methods: A femur model was obtained by 3D computerized tomography (CT) scanning. The angle of femoral neck fracture in the coronal plane observed on the CT image was created on the model at 30, 50 and 70-degree angles. Three cannulated screws were placed in the inverted triangle position. Screws were named “anterior-superior” (A), “posterior -superior” (B), and “inferior” (C). The obtained three different models were transferred to the ANSYS Workbench program. Von Mises stress distribution on the screws and distal fracture surfaces were recorded.
Results: In the 30-degree fracture model, the maximum stress was 18.062 MPa on the "A" screw. It was 22.13 MPa on screw "B" and 16.21 MPa on screw "C". In the 50-degree fracture model, the maximum stress values were 68.04 MPa, 89.52 MPa and 48.94 MPa in screws "A", "B", and "C", respectively. In the 70-degree fracture model, the maximum stress values were 120.02 MPa, 138.32 MPa and 98.37 MPa in screws "A", "B", and "C", respectively. The stress values on the distal fracture surfaces were 13.54 MPa, 43.80 MPa, and 50.07 MPa in the 30, 50, and 70-degree models, respectively.
Conclusion: Increasing fracture angle from 30 to 50 degrees in femoral neck fractures significantly increases the stress on the distal fracture surface and implants.
However, this increase is minimal at angles higher than 50 degrees.

Keywords

Femoral neck fractures, Pauwels classification, cannulated screw fixation, finite element study

Thanks

We would like to thank Ahmet Çankaya, who made the modelling work for the purposes of this study.

Femur boyun kırıklarında üç kanüllü vida ile tespit: kritik kırık açılarında biyomekanik değişiklikler

Abstract

Amaç: Femur boyun kırıklarında koronal planda kırık açısının artması instabiliteyi ve komplikasyonları arttırmaktadır. Bu çalışmadaki amacımız Pauwels sınıflamasında belirlenmiş olan kritik açılardaki (30 derece, 50 derece, 70 derece) biyomekanik değişiklikleri analiz etmektir.
Yöntemler: 3D bilgisayarlı tomografi taramasından elde edilen femur modelinde koronal plandaki kırık açısına göre 30, 50 ve 70 derece femur boyun kırığı oluşturuldu. Inverted triangle pozisyonunda 3 adet kanüllü vida yerleştirildi. Vidalar anterior-superior (A), posterior –süperior (B) ve inferior (C) olarak isimlendirildi. Üç model Ansys Workbench programına aktarılarak vidalardaki ve distal kırık yüzeyindeki von mises stres dağılımları kaydedildi.
Bulgular: Maximum stres 30 derece kırık modelinde A vidasında 18,06 mpa idi. B vidasında ise 22,13 MPa, C vidasında 16,21 MPa olarak bulundu. 50 derece kırık modeline baktığımızda max stres değerleri A vidasında 68,04 MPa iken B vidasında 89,52 MPa ,C vidasında ise 48,94 MPa olarak bulundu. 70 derece kırık modelinde A vidasında maximum stres 120,02 MPa, B vidasında 138,32 MPa idi. C vidasında ise 98,37 MPa olarak bulundu. Distal kırık yüzeyindeki stres değerleri ise 30, 50, 70 derece modellerde sırası ile 13,54 MPa, 43,80 MPa ve 50,07 MPa idi.
Sonuç: Femur boyun kırıklarında kırık açısının 30 dereceden 50 dereceye yükseltilmesi distal kırık yüzeyi ve implantlar üzerindeki gerilimi önemli ölçüde artırmaktadır. Ancak bu artış 50 derecenin üzerindeki açılarda minimumdur.

Keywords

Femur boyun kırığı, Pauwels sınıflaması, Kanüllü vida ile fiksasyon, Sonlu elemanlar analizi

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