Failure rates of Metal-on-Metal (MoM) ASR XL hip implants have been unacceptably high compared with other bearing surfaces, so patients must be monitored over the time checking for disorders in clinical condition, blood tests or in diagnostic imaging. We have carried out a continuing prospective investigation to evaluate the relationship between blood metal ions measurements and ultrasound levels and to evaluate if ultrasound score can predict a future indication to revision.Introduction
Objectives
The Articular Surface Replacement XL system (ASRXL) with metal-on-metal (MoM) of the articular surfaces was produced by DePuy Orhopaedics since 2003 for total hip replacement. In 2010 following the notification received from the National Joint Registry (NJR) of England and Wales concerning the excessive failure rate of the ASR system (approximately 13% at 5 years), the DePuy send the recall of the product. All operated patients were checked. We enrolled in our Followup 106 patients (51 males, 55 females, mean age 63.6) with a total of 107 implants (one is a bilateral case), subjected with clinical and instrumental investigations. The controls were performed annually; for the patients who presented positive clinical-instrumental condictions and values of Chromium (Cr) and Cobalt (Co)> 7 mg /l it has been proposed followup closer, every 6 months for the entire life of the implant. For the evaluation of the cases in our study, we used the following scales:
Clinical Score: Harris Hip Score (pain and functional limitation) Rx score: 0 normal; 1 bone resorbtion and mobilization Ultrasound score: 0 none 1 fluid collection <20 mm 2 fluid collection >20 mm 3 solid mass: metallosis Blood metal levels of Cr-Co (μg/l = parts per billion = ppb) Normal < 3 ppb Alert 3–7 ppb Pathological >7 ppb The analysis of ionemia was made at the Clinical Chemistry at Charing Cross Hospital in London.INTRODUCTION
MATERIALS AND METHODS
