Abstract
INTRODUCTION
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.
MATERIALS AND METHODS
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:
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Clinical Score: Harris Hip Score (pain and functional limitation)
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Rx score:
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0 normal;
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1 bone resorbtion and mobilization
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Ultrasound score:
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0 none
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1 fluid collection <20 mm
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2 fluid collection >20 mm
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3 solid mass: metallosis
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Blood metal levels of Cr-Co (μg/l = parts per billion = ppb)
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Normal < 3 ppb
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Alert 3–7 ppb
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Pathological >7 ppb
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The analysis of ionemia was made at the Clinical Chemistry at Charing Cross Hospital in London.
RESULTS
The followup includes 106 patients for a total of 107 hip prostheses. Of these patients, 34.5% (36 patients, 22 women and 14 men, average age 61 years, min. 34 – max. 79), had implant revision with a dual mobility cup implant. The Mean follow-up was 76.5 months. In patients who underwent revision surgery it was evaluated the trend of Cr and Co concentration in the period after the replacement. In 7 patients (2 women, 5 men) (19.4%) the replanting is caused to the mobilization of the cup, in 1 case (2.6%) to a severe functional limitation and pain. In the remaining 29 patients (19 women, 10 men) (78%) the replanting is due to high levels of Cr and Co and ultrasound positive for collection. We are following the additional 70 patients (34 women, 36 men), not revised.
DISCUSSION
From our study we show that the main cause of revision was the ionemia. Analysis of variance for repeated measures shows a statistically significant reduction of the concentrations of Cr and Co as a result of the revision, supporting evidence that the wear of MoM implants was the main cause.
CONCLUSION
From our analysis, we observed that the metal-metal hip replacement system DePuy J&J showed a excessive revision rate, associated with levels of metal ions significantly higher than the other hip prosthesis. The return values of ionemia, after the revision surgery, has appeared in all operated cases and the fluid collection after revision has disappeared, with a clear improvement in the clinical condition of patients.
