Post-marketing studies carried out by the US orthopaedic company DePuy showed a high revision rate for its ASR (articular surface replacement) hip implant three years before it was recalled from the global market, newly released internal documents show.

The controversial prosthesis was recalled in August 2010 after “new data” from the National Joint Registry of England and Wales showed that it was failing at a higher rate than competing implants, a “Dear doctor” letter sent out by the company to surgeons said. It stated revision rates of 8-9% at three years.

The ASR comes in two types, one used in a resurfacing technique and the other as part of a total hip replacement called the ASR XL.

However, an unpublished survival analysis conducted in June 2007 from the company’s own database showed …