An innovative hip stem developed 50 years ago has now been implanted in more than two million patients across the globe.

The Exeter hip stem was developed in a collaboration between NHS surgeon Professor Robin Ling and University of Exeter engineer Dr Clive Lee and is globally manufactured by Stryker.

Their ground-breaking design overcame a problem of previous hip implants – that they eventually became slightly loose, requiring further surgery.

Previous prosthetic hips had been designed with the idea that the implant should remain rigidly fixed to the acrylic bone cement in which it is implanted.

Prof Ling and Dr Lee’s design was revolutionary an unlike previous prosthetic hip stems, the Exeter design did not have a collar between the neck and the stem of the implant.

This allowed the stem to subside slightly into the acrylic, self-tightening as it did so.

This made best use of the material properties of the polymer when bearing weight as the person moved on their new hip, which helped to significantly reduce the number of follow-up revision surgeries needed.

Since the first implant on November 27 1970, the Exeter hip stem has been implanted globally in more than two million patients, with one million happening in the last 10 years alone.

In 2018, the Exeter hip was listed among the 100 best breakthroughs from university innovation.

A 2016 study found the hip was still functioning well in 99% of patients at 23 years follow-up, and in another study in 2020, patients implanted with an Exeter stem 50 years or younger demonstrated that the hip performed well over time in 96% of people.

Dr Lee said: “I started out not really knowing what a total hip replacement should look like – that was probably a huge advantage.

“I designed a very simple structure, and it turned out that going back to basic principles worked out very well indeed.

“We were aiming for a hip replacement that would last perhaps eight or nine years, and that would benefit patients locally.

“It’s a huge testament to the Exeter team and the university and NHS working together that it’s had such fantastic success. It’s a source of great pride.”

The results proved to be outstanding – word spread, and the reliability of the Exeter hip led to its use extending across the globe

Jonathan Howell, consultant orthopaedic surgeon at the Royal Devon and Exeter NHS Foundation Trust, added: “The worldwide success of the Exeter hip replacement is really quite extraordinary.

“It started 50 years ago, in 1970, and for the first five years, its use was essentially restricted to Exeter because its inventors, Professor Robin Ling and Dr Clive Lee, wanted to study its results closely.

“The results proved to be outstanding – word spread, and the reliability of the Exeter hip led to its use extending across the globe.

“The Exeter hip has relieved the pain of those afflicted with hip arthritis, both old and young, allowing them to resume the activities that they enjoy.

“We have patients returning to hiking, swimming, tennis, golf, and even activities that people may not associate with hip replacements, such as skiing.”