Advancing joint replacements and prosthetic joint infection treatment

Joint replacements are incredibly effective, helping patients recover their mobility and return to their day-to-day lives with less pain. Most joint replacements last up to 20 years, and over time their bearings wear away. This causes the prosthetic to come loose from the bone it’s attached to, which can be very painful and leads to further bone loss.

This expected wear is called aseptic loosening, and is typical for all prosthetic joint replacements. When this happens, the implants need to be replaced in what’s called a revision surgery. Compared to an initial joint replacement, a revision surgery is more complex, requiring more planning, specialist equipment and a longer hospital stay. “The length of a stay for a normal knee replacement is about two to three days, but is often five or more days for a revision,” explains Mr Stevenson. The surgery involves using the same incision as the initial replacement, removing the old prostheses and reconstructing the joint with new prostheses.

The prosthetic joint replacements used in revision surgeries are more complex than those used in a primary replacement. The worn prosthetics often cause damage to the bone, so specialist implants and techniques are used. “We use special 3D printed porous metal bone grafts,” says Mr Stevenson. “They replace lost bone and have tiny pores that allow new bone to grow into the metal and secure it in place.” 

Innovation isn’t just in the implants, but also in the dressings for the wounds. Revision surgeries involve larger incisions, which require specialist wound care. To reduce the risk of failure and infection, Mr Stevenson uses vacuum dressings. These have negative pressure that acts like a vacuum, holding the edges of the wound together to promote healing and minimise the risk of unnecessary dressing changes during admission, which is much more convenient for patients. In high risk wounds, these vacuum dressings have been shown to also reduce the risk of reoperation. 

Whilst the majority of revision replacements are indicated by gradual loosening of the prostheses, in a small number of cases, other factors can result in a prosthetic failing early. The leading cause of early failure is infection, which can affect one to two percent of all hip and knee replacements. 

Infections can become serious if left untreated, so require rapid assessment and surgery. “I specialise in treating infected hip and knee replacements and bone tumour prostheses,” Mr Stevenson says. Tumour prostheses add an additional layer of complexity as these are large prostheses used to replace bone lost after the removal of a bone tumour, and have much higher infection rates. 

The typical patient suffering from infection poses a significant challenge for surgery. Patients are often older, or with more co-morbidities such immunosuppression. “We see a lot of patients who’ve had chemotherapy or radiotherapy which makes them more vulnerable to infection,” Mr Stevenson explains. “We also see patients being treated for skin conditions such as psoriasis who are on immunosuppressant drugs to control their skin disease.” While these patients increase the complexity of surgery, they’re also much more vulnerable to the infection itself, which if left untreated will significantly impact their quality of life.

The surgery itself is also more complex than a typical revision surgery. “The surgical management is much more involved,” Mr Stevenson explains. “The gold standard for eradicating infections isn’t one operation, it’s two.” During the first operation, all the infected material – the implant, bone and surrounding soft tissues – is removed. “That’s quite a radical resection of anything the infection has touched,” describes Mr Stevenson. He then implants a temporary joint replacement so the patient is still mobile while recovering, before undertaking a second surgery three to six months later to implant a new joint replacement. 

While two operations are seen as the gold standard, Mr Stevenson tailors his approach for each individual patient. “In patients who are fit and healthy and who have infections susceptible to antibiotics, we may carry out the revision in a single operation,” explains Mr Stevenson. 

For the more complex patients, Mr Stevenson collaborates with a range of specialists in a multidisciplinary team (MDT) to determine the best treatment option for each patient. “I co-chair the West Midlands regional MDT for revision arthroplasty,” he explains. “We determine each patient’s management plan in conjunction with specialists in microbiology, pharmacy and infectious diseases.” 
With their combined expertise, the specialists come to a joint consensus on the most beneficial treatment plan for every patient. “We discuss 30 to 35 cases a week,” says Mr Stevenson. These discussions include diagnosing the specific infection each patient has to provide them with the right antibiotics to best treat the infection, followed by determining how to approach their surgery. Everything is done with the benefit of the patient as the priority. “We need the patients to be treated by the right clinicians to minimise the risk of failure and, ultimately, give patients the best outcomes.”

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