Waffle that dissolves in the knee – slow release painkillers to ease the pain of surgery

A wafer that slowly releases painkilling medication as it dissolves in the body could boost recovery after knee replacement surgery.

The implant, the size of a 20p coin, is sewn into the new joint during an operation, which is performed on around 100,000 NHS patients each year.

Each wafer – made from the same material as dissolvable sutures – contains 500 mg of bupivacaine, a local anesthetic commonly used in dental procedures and childbirth.

As the wafer slowly breaks down over three to four weeks, the bupivacaine seeps into surrounding nerve endings in the knee, blocking pain signals.

The dose released is highest in the first few weeks after surgery, when pain is usually at its worst.

A slow-release medication waffle could help relieve pain after knee replacement surgery (archive photo)

Allay Therapeutics, the US company that developed the wafer, is also planning trials in patients requiring other joint replacements and abdominal surgeries.

British doctors testing the wafer – called ATX101 – hope it will eventually allow thousands of NHS patients to use fewer opioid drugs, such as morphine, routinely used to treat pain after joint replacement surgery.

Morphine and other opioids are effective in treating pain, but their effects wear off within 24 hours. They can cause side effects ranging from nausea to breathing problems and dependence, even after a few days of use.

“A small but significant proportion of patients may become addicted to opioids,” said Professor Hemant Pandit, an expert in hip and knee surgery at the University of Leeds and Leeds Teaching Hospitals NHS Trust, who is leading the UK arm of an international trial of the painkilling wafer.

“The goal is to reduce or even eliminate the need for patients who have undergone knee replacement to use opioids.”

Around nine million people in the UK have osteoarthritis, where the protective cartilage in a joint breaks down, causing bone to rub against bone, causing pain and problems moving the joint. It is often caused by wear and tear, although other risk factors include being overweight and sports injuries.

While anti-inflammatory painkillers and steroid injections can help, many will eventually require a knee replacement. Opioid medications such as morphine, oxycodone, and tramadol are the mainstays of post-operative pain management.

In addition to the serious side effects, the medications often need to be taken several times a day to be effective.

However, the wafer is intended to provide 24-hour relief for up to a month. It is designed to dissolve in such a way that it releases half of its drug content in the first few days and then smaller amounts as the pain subsides.

File photo of a surgical team operating on a patient. The new wafer is expected to provide 24-hour relief for up to a month after surgery

A recent study of 112 patients from the United Kingdom, Canada and Australia – yet to be published in a medical journal – found that 22 percent of patients who received the wafer did not need opioids during their recovery from knee surgery, compared with just 2 percent of those who did not.

They were also able to get up faster after surgery, climb stairs faster and sleep better than those who used strong painkillers.

A larger study involving approximately 200 patients is now being planned.

Dr Wendy Holden, a consultant rheumatologist and medical advisor to the charity Arthritis Action, said the waffle ‘appears to be much better at reducing pain and is great news for patients. Hopefully it will be available on the NHS soon’.