Konik ve silindirik pedikül vidalarının sıyırma dirençleri ve direngenliklerinin karşılaştırmalı biyomekanik analizi

Öz

Amaç: Transpediküler enstrümantasyonda konik ve silindirik pedikül vidaları sık kullanılmaktadır. Vidaların mekanik performansı kemik-vida yüzeyinin biyomekanik özellikleri ve vidanın fiziksel yapısı ile ilişkilidir. Bu çalışmada, konik ve silindirik pedikül vidalarının biyomekanik açıdan farklarının olup olmadığının araştırılması amaçlandı. Yöntem: İskelet maturasyonunu tamamlamış, 400-600 kg ağırlığında 24–32 haftalık danalardan elde edilmiş taze lomber vertebralar kullanıldı. Toplam 24 vertebranın her iki pedikülüne (48 pedikül) vida yerleştirilerek biyomekanik testler uygulandı. Vidaların maksimum giriş tork değerleri analog tork metre kullanılarak kaydedildi. Rijid tespitin sağlanması için polimetilmetakrilat içeren metal kutuların içerisine gömülü vertebradaki pedikül vidaları mekanik test makinasına bağlanarak sıyırma direnci ölçüldü. Bulgular: Konik vidaların sıyırma dirençlerinin ve direngenliklerinin ilk atım ve tekrarlayan atımlarda silindirik vidalara göre yüksek olduğu, ancak aradaki farkın istatistiksel olarak anlamlı olmadığı tespit edildi (p>0.05). Maksimum giriş tork değeri ise konik vidalarda silindirik vidalara göre istatistiksel olarak anlamlı düzeyde yüksek idi (p=0.04). Vidaların 180º ve 360°geri çekimli sıyırma direnci ve direngenlik verileri arasında istatistiksel olarak anlamlı fark olmadığı tespit edildi (p>0.05). Sonuç: Konik vidaların silindirik vidalara göre daha dirençli tutunma verilerine sahip olmalarının yanı sıra, aynı delikten yapılan çoklu vida atımlarında ya da geri çekilme işlemi sonucunda vidalar arasında sıyrılma verileri açısından belirgin bir fark izlenmemiş olması, konik vidaların gelecekte daha sık kullanılacaklarını düşündürmektedir. 

Anahtar Kelimeler

• Transpediküler fiksasyon,Konik vida,Silindirik vida,Biyomekanin analiz

A comparative biomechanical analysis of pull-out resistance and stiffness of conical and cylindrical pedicle screws

Öz

Aim: Conical and cylindrical pedicle screws are frequently used in transpedicular instrumentation. The mechanical performance of screws is associated with the biomechanical properties of the bone–screw surface and the physical structure of the screw. The purpose of this study was to investigate whether conical and cylindrical pedicle screws differ in their biomechanical properties. Methods: Fresh lumbar vertebrae were obtained from 24–32-week-old calves that completed skeletal maturation and weighed 400–600 kg. Screws were placed on both pedicles (48 pedicles) of total 24 vertebrae, and biomechanical tests were performed. The maximum input torque values of the screws were recorded using an analog torque meter. Pull-out resistance was measured by attaching pedicle screws in the vertebra. The vertebral pedicle screws were embedded into metal boxes containing polymethyl-methacrylate to provide rigid fixation to a mechanical tester. Results: Pull-out resistance and stiffness were higher in conical screws than in cylindrical screws in the first and repetitive insertions; however, the difference was not statistically significant (p>0.05). The maximum input torque was significantly higher (p=0.04) in conical screws than in cylindrical screws. No significant difference (p>0.05) was observed between pull-out resistance and stiffness values of the screws with 180° and 360° back-outs. Conclusion: Conical screws had more resistant fixation data than cylindrical screws, and there was no significant difference between the screws in terms of pull-out resistance data due to multiple screw insertions performed from the same hole or due to the back-out procedure; this indicates that conical screws are likely be used more frequently in the future.

Anahtar Kelimeler

• Transpedicular fixation,conical screw,cylindrical screw,biomechanical analysis

Kaynakça

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