Established hip and knee arthroplasty registers exist in many countries but this is not the case with spinal implants. Moreover, in the case of a rod intended to guide spinal growth in a child and then be removed, the definition of ‘failure’ (revision) used for hip or knee arthroplasty is inappropriate. How can the performance of such spinal implants be judged? Ninety-six MAGnetic Expansion Control (MAGEC) spinal rods were obtained from multiple centres after removal from the spines of 52 children with scoliosis. Clinical details were assessed and divided between unplanned revision operations (‘failures’) and those which were planned. Of the explanted rods, 49 were tested for the amount of force they could output, using the manufacturer's supplied test jig. Sixty-five rods were cut apart so that the internal components (bearings, O-ring seals, drive pins) could be assessed, alongside if there was evidence of internal wear.Background
Methods
Deformation of modular acetabular press-fit shells is a topic of much interest for surgeons and manufacturer. Such modular components utilise a titanium shell with a liner manufactured from metal, polyethylene or ceramic. Initial fixation is achieved through a press-fit between shell and acetabulum with the shell mechanically deforming upon insertion. Shell deformation may disrupt the assembly process of inserting the bearing liner into the acetabular shell for modular systems. This may adversely affect the integrity and durability of the components and the tribology of the bearing. Most clinically relevant data to quantify and understand such shell deformation can be achieved by cadaver measurements. ATOS Triple Scan III was identified as a measurement system with the potential to perform those measurements. The study aim was to validate an ATOS Triple Scan III optical measurement system against a co-ordinate measuring machine (CMM) using in-vitro testing and to check capability/ repeatability under cadaver lab conditions.INTRODUCTION
OBJECTIVE
