Abstract
Introduction
Mechanical stabilization following periprosthetic fractures is challenging. A variety of cable and crimping devices with different design configurations are available for clinical use. This study evaluated the mechanical performance of 5 different cable systems in vitro. The effect of crimping device position on the static failure properties were examined using a idealized testing set up.
Materials and Methods
Five cable systems were used in this study; Accord (Smith & Nephew), Cable Ready (Zimmer), Dall-Miles (Stryker), Osteo Clage (Acumed) and Control Cable (DePuy). Cables were looped over two 25 mm steel rods. Cable tension was applied to the maximum amount using the manufactures instrumentation. Devices were crimped by orthopaedic surgeon according to instructions. Crimping device/sleeve was secured in two different positions; 1. Long axis in-line with the load; 2. Long axis perpendicular to the load (Fig 1). Four constructs were tested for each cable system at each position. All constructs were tested following equilibration in phosphate buffered saline at 37 degrees Celsius using a servohydraulic testing machine (MTS 858 Bionix Testing Machine, MTS Systems) at a displacement rate of 10 mm per minute until failure. The failure load, stiffness and failure model (cable failure or slippage) was determined for all samples. Data was analysed using a two way analysis of variance (ANOVA) followed by a Games Howell post hoc test. One sample of each cable – crimping construct was embedded in PMMA and sectioned to examine the crimping mechanism.
Results
In vitro mechanical performance of the five cable systems tested differed between systems. Position of the crimping device was also a significant variable which influenced the peak load, stiffness as well as failure mode. Cable failure, cable failure inside crimping sleeve as well as cable slippage was observed when the crimper was perpendicular to the applied load while cable slippage was found when the load was in line with the crimper. Peak loads of the systems ranged from well over 5 kN (Cable Ready) to 1 kN (Accord) (Fig 2). Analysis of the crimping technique varied between systems as was achieved either with direct or indirect cable compression (Fig 3).
Discussion
Cable systems achieve fixation through different means as demonstrated in this study. These differences translated into different failure modes as well as a wide range of mechanical properties when tested under idealized conditions. Placement of the crimping device can influence the failure loads as noted in the current testing.
