Could a "dissolvable wafer" revolutionise pain relief for knee replacements?

The night after his first knee replacement operation, retired company director Markus Rasche asked for some pain relief.

“I took just one dose of morphine at 2am, when I couldn’t sleep from the pain, but that’s it,” he explained, speaking to a newspaper after the experience.

“Despite a 10cm wound down the front of my knee, I could bend it almost immediately. Given how little morphine I needed, it seemed likely that I had been given the dissolving implant…”

The implant Mr Rasche mentions is the ATX-101 wafer, a medical technology that takes a completely new approach to relieving pain after major knee surgery.

Mr Rasche, from North Yorkshire, took part in one of the first international trials of the implant last year – and the results, so far, have been very encouraging. So what exactly is this dissolvable wafer – and can we expect to see it arriving in UK hospitals soon? Let’s look at the story in a bit more detail.

What is the standard pain relief after a knee replacement?

Knee replacement is a common procedure for people, like Mr Rasche, who suffer from severe osteoarthritis: there are around 100,000 every year in the UK, and most of the operations are very successful. But it’s also a major surgery that can cause significant pain in the early stages. One of the main types of medicine that patients receive in hospital is an opioid, such as morphine or tramadol. These drugs are very effective at relieving pain, but they have both pros and cons.

What are the downsides of opioids?

One of the disadvantages of opioid-based medicine is that it can cause side effects in some patients. Some of the more common ones are nausea and constipation. The other problem is that they can be very addictive, even after a few days of use. That’s why doctors will ask you to shift towards standard pain relievers like ibuprofen and paracetamol when you get home. A further issue with common post-surgery injections is that their pain-relieving impact can only last so long – usually around 12-18 hours, after which the effects wear off.

How is the ATX-101 wafer different?

It has two big differences from standard pain relievers:

Drug type – the active ingredient in ATX-101 is bupivacaine – not a regular painkiller but a type of anaesthetic
Delivery – the drug is held in a wafer, which the surgeon places inside the knee joint at the end of the operation

The wafer is pretty small: about the shape and size of a guitar pick. Created by the US biotech company Allay Therapeutics, it’s made of a thin, surgical suture material, which is bioabsorbable, i.e. it’s designed to dissolve in the body.

What are the advantages of a dissolvable wafer?

The first benefit is that it doesn’t involve opioids. Bupivacaine is a local anaesthetic, which targets pain by blocking the signals at nerve endings. It has been around since the 1950s and is used in everything from childbirth to dental procedures. In fact the World Health Organization lists bupivacaine as one of its Essential Medicines. The other key advantage is the form factor. The wafer is designed to release the anaesthetic gradually, over a period of weeks rather than hours. It has been described as a “round-the-clock” pain reliever.

What does this mean for knee patients?

The team at Leeds Teaching Hospitals NHS Trust, which was involved in Mr Rausche’s trial, is very positive about its potential impact. “Latest study results show the wafer provided sustained post-surgical pain relief for up to four weeks for patients following total knee replacement,” they reported, in the summer of 2024. “Compared to the standard of care, the wafer provided longer-lasting pain relief, reduced the need for opioids, and allowed patients to return to daily activities sooner.” That’s all very encouraging. And indeed it was followed by the news (in December 2024) that the influential US Food & Drug Administration (FDA) has given the wafer a “Breakthrough Therapy designation“.

So we await further research, and the all-important approval and guidance from the regulators if and when it comes. But the outlook for this new drug is certainly exciting. As ever, we’ll keep you updated on developments as we get them.