Researchers at Massachusetts General Hospital (MGH) have developed a new polymer that can be used as a coating for artificial joints to simplify the treatment of prosthetic joint infections.
Joint replacement surgery is now one of the most common orthopedic surgical procedures performed in the United States. Damaged joints are replaced with artificial joints and the procedure is usually effective, with nine out of ten patients experiencing immediate relief from joint pain.
However, one of the major complications from joint replacement surgery is infection. According to the American Academy of Orthopedic Surgeons, infection occurs in fewer than 1-2% of patients, requiring patients to undergo further surgery. Around 30,000 patients in the United States each year suffer from infections post-surgery.
Infection can be discovered at hospital, although it can take many weeks or even years after surgery before infection is diagnosed. The longer the infection remains undiagnosed, the more difficult it is to treat.
Delivering antibiotics to the joints is difficult, since there is a limited supply of blood to the area. Further surgery is therefore required. In some cases, the only option is to remove the implant.
In such cases, the patient has bone cement positioned in the joint which releases antibiotics and cures the infection. It can be several weeks before surgeons are able to fit a new artificial joint. The infection can also recur, which may require permanent joint fusion or amputation of the limb.
Bone cement can only release a limited dose of antibiotics, which is typically delivered over the course of a week. Increase the content of antibiotics in the bone cement and it affects the durability of the material, while some beneficial antibiotics cannot be incorporated into bone cement.
Orhun Muratoglu, PhD, director of the Harris Orthopaedics Laboratory in the MGH Department of Orthopaedic Surgery, said “Currently, most infections involving total joint replacement prostheses require a two-stage surgery, in which the patient’s daily activities are largely compromised for four to six months.”
The new polymer coating simplifies the treatment of prosthetic joint infections, requiring only one surgical intervention. This new treatment of prosthetic joint infections reduces the discomfort and inconvenience for the patient as well as the risk of complications.
The team used an animal model and deliberately infected joints with Staphylococcus aureus. In all cases, the new coating cleared up the bacterial infection, whereas the infection persisted in the control group, which involved treatment with antibiotic-infused bone cement.
Muratoglu said, “We used two separate infection models because, when patients present with prosthetic joint infection symptoms, it is not clear what proportion of bacteria may be in a biofilm and what are free floating in solution.” The treatment was effective for both infection models.
The team is now working with the FDA and other regulators to get approval to have the material incorporated into clinical products.
The researcher’s study – A fully functional drug-eluting joint implant – has recently been published in Nature Biomedical Engineering.