Intra-Articular Injection Before THA Linked to Early Revision

In a retrospective study using databases for Ontario, Canada, researchers found intra-articular injection one year before elective, primary total hip arthroplasty for osteoarthritis was associated with early revision precipitated by infection.

“We found that most arthroplasty patients who had a prior [intra-articular] injection had it a year before their surgery and that this injection was a risk factor for early revision mediated by infection,” said Bheeshma Ravi, M.D., of the Women’s College Hospital at the University of Toronto in Ontario, Canada.

Reseachers identified 37,881 patients who underwent primary total hip arthroplasty (THA) between 2002 and 2009 for osteoarthritis. Of these patients, 2,468 had at least one intra-articular injection by a radiologist five years before their surgery and nearly 70 percent of this group received the injection one year before THA.

“Patients who had an injection were likely to be female, were more likely to receive their joint replacement at a teaching hospital, and interestingly enough, they were not particularly different in terms of their comorbidity as measured by the Charlton score,” Ravi said.

A univariate analysis showed a higher risk for both infection and revision within two years for patients who had an injection one year before THA compared to patients who did not undergo injection. After including infection in a multivariate model, the investigators found injection was no longer associated with revision. They found significant results using the Sobel t-test, indicating that the relationship between injection and revision was mediated by infection.

Limitations of the study included use of billing codes, which did not specify which joint was injected, and a lack of knowledge about the type of substance injected.

“While we can say that prior injection is a risk factor for revision, we cannot determine if it was based on a particular solution that was used,” Ravi said.