A Biomechanical Study Comparing Helical Blade with Screw Design for Sliding Hip Fixations of Unstable Intertrochanteric Fractures

Qiang Luo,Grace Yuen,Frankie Leung,Tak-Wing Lau,Kelvin Yeung

doi:10.1155/2013/351936

Abstract

Dynamic hip screw (DHS) is a well-established conventional implant for treating intertrochanteric fracture. However, revision surgery sometimes still occurs due to the cutting out of implants. A helical blade instead of threaded screw (DHS blade) was designed to improve the fixation power of the osteoporotic intertrochanteric fracture. In this study, the biomechanical properties of DHS blade compared to the conventional DHS were evaluated using an unstable AO/OTA 31-A2 intertrochanteric fracture model. Fifty synthetic proximal femoral bone models with such configuration were fixed with DHS and DHS blade in five different positions: centre-centre (CC), superior-centre (SC), inferior-center (IC), centre-anterior (CA), and centre-posterior (CP). All models had undergone mechanical compression test, and the vertical and rotational displacements were recorded. The results showed that DHS blade had less vertical or rotational displacement than the conventional DHS in CC, CA, and IC positions. The greatest vertical and rotational displacements were found at CP position in both groups. Overall speaking, DHS blade was superior in resisting vertical or rotational displacement in comparison to conventional DHS, and the centre-posterior position had the poorest performance in both groups.

Highlights

Sliding hip screw has been a well-established treatment for intertrochanteric fracture [1,2,3]
In order to improve the fixation of unstable intertrochanteric fracture, a helical-shaped blade in dynamic hip fixation (DHS blade) with larger transverse area to resist cutting out was introduced in recent years
X-ray showed that dynamic hip screw (DHS) blade reached the top without cutting out, and no further displacement or rotation at SC position

Summary

Introduction

Sliding hip screw has been a well-established treatment for intertrochanteric fracture [1,2,3]. The revision rate of dynamic hip screw (DHS) was reported to be in the range of 4%–12% [4,5,6], and the complications of failed fixation led to the femoral head cutting out rates of 1.7% to 6.8% [7,8,9], especially in osteoporotic fractures. In order to improve the fixation of unstable intertrochanteric fracture, a helical-shaped blade in dynamic hip fixation (DHS blade) with larger transverse area to resist cutting out was introduced in recent years. By inserting the blade into the femoral head, the surrounding trabecular structure would undergo a volumetric compaction It offers the potential of resisting rotation and a better holding power in osteoporotic femoral head with more cancellous bones compaction and theoretically can decrease the rate of cutting out. No such guidelines had been described for the blade design, and there is only little information in the literature about the performance of DHS blade

Objectives

Methods

Results