A new type of hip replacement implant reduces the risk of joint dislocation after surgery by 70 per cent. This is the finding of a new study involving 1,600 patients across 44 hospitals in Sweden and the UK, as published in The Lancet. The new implant consists of a small ball encased in a much larger plastic ball, which gives better stability.
Each year, over 14 million patients in the world suffer from a femoral neck fracture. Total hip replacement (THR), where both the ball and the socket of the hip are replaced, is recommended for older, active individuals with a displaced fracture of the femoral neck. While the vast majority regain good mobility and quality of life, up to 8 per cent of these patients experience a dislocation of their hip, a very painful condition where the artificial joint slips out of place.
New type of cup
In a new study, researchers from Uppsala University and Queen Mary University of London investigated whether a new type of cup, referred to as a dual-mobility total hip replacement (DM THR) could reduce the risk of complications.
"It is extremely painful when a hip replacement dislocates. When it occurs, patients require sedation or further surgery to realign the joint. Once the joint has dislocated, this impairs quality of life, as the patient may feel that they can no longer really trust the implant. There is also a significant strain on healthcare resources," says Nils Hailer, consultant orthopaedic surgeon at Uppsala University Hospital, professor of orthopaedics, and one of the researchers behind the study.
Patients from Sweden and the United Kingdom
The study included 1,600 people aged 65 or over who had suffered a femoral neck fracture and who were deemed suitable for a THR. Patients treated at 20 hospitals in Sweden and 24 in the UK were randomly assigned to receive either a dual-mobility hip replacement or a standard hip replacement.
Risk reduced by 70 per cent
The study found that the risk of dislocations fell by 70 per cent for patients who received the new dual mobility cup. One year after surgery, only 1.3 per cent of these patients had experienced hip dislocation, compared with 4.2 per cent in the group who received a traditional hip replacement. In addition to the significant improvement in terms of dislocations, the study showed that the overall risk of surgical complications was also lower in the group that received the new cup. However, no differences were observed between the groups regarding the incidence of implant infection or mortality, nor were there any differences in quality of life during the first year post-surgery.
"I, along with our surgeons around the world, have been wondering if there is any benefit of these types of hip replacements in people with a broken hip for over a decade. I've tried to run similar studies before but never been able to deliver one that is big enough to give us a reliable answer to the question. Meeting the team in Uppsala and making this international collaboration a reality has been a game changer for accelerating how quickly we can discover the answers to these sorts of questions," says Xavier Griffin, professor at Queen Mary University of London and Honorary Consultant Orthopaedic Surgeon at Barts Health NHS Trust.
Included smaller hospitals
"No one has previously conducted such a large study in which patients were randomly assigned to either a dual-mobility cup or the standard type of cup. It is very significant that we did not limit participation to university hospitals, but instead included smaller hospitals from a variety of locations in both countries, even from places without extensive research experience," says Nils Hailer of Uppsala University. "Together, surgeons in Sweden and the UK succeeded in delivering a large, pragmatic orthopaedic randomised trial involving both smaller hospitals and major referral centres across two countries. Beyond the findings themselves, we believe this collaboration sets a new benchmark for future randomized trials in European orthopaedic research."
No new technology or training required
Although dual mobility implants are currently more expensive than standard implants, researchers believe the reduction in complications could offset the higher upfront cost and are currently undertaking a full health economic analysis.
"Crucially, DM-THR requires no new technology or training. Surgeons are already familiar with both implant types, meaning the change could be implemented immediately within existing practice," says Xavier Griffin.
