We are extremely grateful to Professor Carl Heneghan of Oxford University, and his many colleagues, who trawled the flimsy evidence and flawed approval system for medical implants, to shine a spotlight on the mesh scandal.

In his latest blog, Trans Vaginal Mesh. Part 1: Deadly Devices Heneghan proves that not only does pelvic mesh give rise to life-altering complications, it hasn’t been shown to work any better than the traditional operation that requires no implant.  

“The long-term consequences of lax approval and the failure to heed the early warnings would lead to hundreds of thousands of women being irreversibly harmed,” he writes. “But it would take many more problems to finally face up to the troubles.” 

Commercial interest trumped clinical need

Pelvic mesh was approved after a few tests in laboratory animals. “Clinical trial data was never part of the requirement. It goes without saying that this is deeply troubling,” Heneghan says.

“Regulatory approval creates a smokescreen suggesting mesh devices are safe and effective. Imagine, though, if you were to undergo an operation for a device designed to be implanted lifelong, and you were told it’s only been tested on animals and a few laboratory tests.”

Pelvic mesh history

Heneghan writes that In 1996, the US FDA approved the ProtoGen sling, agreeing that the product was “substantially equivalent” to the Mersilene Mesh used to treat hernias. Boston Scientific relied on a 90-day study in rats and its use in cardiovascular implants for approval. At the time, clinical data for its use in the vaginal area wasn’t required for approval. 

By November 1997, the company started its first long-term study,  despite already knowing of at least 125 harmful events.  By 1999, a small study of 34 women, who had the Protogen removed for complications, showed that half the meshes had eroded through the vaginal wall. At the end of 1999, Boston Scientific voluntarily recalled 20,000 of its implants because of the mounting problems related to its use.  

The withdrawal should have prompted regulators to require clinical data for the approval of subsequent devices. However, they did not. The FDA continued to approve vaginal mesh based on the flimsiest of evidence. More concerning is that later devices went on to use the Protogen Sling as the example device in their applications for approval. To gain US approval, all you had to do was report your new device was similar to a pre-existing device (the predicate) already on the market. Throw in a few animal tests and a bit of lab testing, and you’re done. 

For example, by January 1998, Ethicon’s Tension Free Transvaginal Tape (TVT) was cleared, naming the ProteGen as its predicate device. Soon after, the TVT-obturator was also cleared based on the ProteGen. 

Often, no one has a clue as to which devices were used as the predicates for approval. 

Flawed scientific evidence

‘Few trials are reported by authors in a complete fashion and most information came from abstracts presented in annual meetings. The broader effects of suburethral slings could not be established since trials did not include appropriate outcome measures such as general health status….Reliable evidence on which to judge whether or not suburethral slings are better or worse than other surgical or conservative management is currently not available.’

Cochrane Database Syst Rev. 2005 doi: 10.1002/14651858.CD001754.pub2.

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