Assessment of material loss of retrieved magnetically controlled implants for limb lengthening.

PURPOSE: We aimed to understand wear from the telescopic component of PRECICE nails, which are used for distraction osteogenesis of the femur or tibia. We also aimed to identify any correlation between implant performance and patient factors.

METHODS: This retrieval study involved 11 magnetically controlled intramedullary nails from nine patients who had achieved the targeted leg length. All the nails were assessed macroscopically and microscopically for wear. All implants were radiographed to assess the internal mechanism. A Talyrond 365 (Taylor Hobson, Leicester, UK) roundness measuring machine was used to generate three-dimensional surface maps of the telescopic components to allow for measurement of wear.

RESULTS: Visual assessment of all the nails showed evidence of wear from the telescopic component. The radiographs revealed that all the nails had intact internal mechanism and no evidence of fractured pins. The roundness measuring machine showed that the quantity of wear was lowest in the latest design of the PRECICE nail. There was no significant correlation between wear and the two patient factors (duration of the lengthening phase, the time of implantation) included in this study.

CONCLUSION: This study is the first to investigate the performance of the three different designs of the PRECICE system with a focus on wear. We found that the latest design had the best implant performance. We are confident of the continued success of the PRECICE system and reassure surgeons and patients that they are unlikely to encounter problems with the implant related to wear.