The Link Between Hip Injections and PJI after THA
A recently published study suggests that the time period between intraarticular hip injection and total hip arthroplasty influences the possibility that the patient will develop a periprosthetic joint infection after the joint replacement procedure.
Nicole Stevens, MD, and Ajit Deshmukh, MD
Werner BC, Cancienne JM, Browne JA. The timing of total hip arthroplasty after intraartricular hip injection affects post operative infection risk. J Arthroplasty 2016(30): 820-823
Intraarticular hip injections are often done for diagnostic or therapeutic reasons in patients who are candidates for total hip arthroplasty (THA). Current literature is conflicting on the impact of these injections on infection rates following THA.
In this study, Werner et al sought to investigate the rate of postoperative periprosthetic joint infections (PJI) in patients who had had hip injections and then THA within certain time periods:
- THA within 3 months of injection
- THA 3 to 6 months after injection
- THA 6 to 12 months after injection
They hypothesized that recent ipsilateral hip injection was associated with a higher incidence of PJI after THA.
The authors collected data from the PearlDiver Patient Records Database. The database was queried for CPT codes for THA and large joint injections associated with ICD-9 hip diagnoses. Boolean code then identified patients who underwent THA following ipsilateral hip injection.
A total of 34,597 patients who underwent THA were included in the study. Of those, 829 patients underwent THA within 3 months of injection, 1379 between 3 and 6 months after the injection, and 1160 between 6 and 12 months of the injection. The authors used 31,229 patients who did not have preoperative injections as controls. There was no significant difference between the demographics of each cohort and the controls.
Two time points were chosen for infection monitoring: 3 months after THA and 6 months after THA. The infection rates for each group at these 2 time points were:
- THA within 3 months: 2.41% at 3 months and 3.74% at 6 monthsTHA 3 to 6 months after injection: 1.31% at 3 months and 2.39% at 6 months
- THA 6 to 12 months after injection: 1.12% at 3 months and 2.45% at 6 months
- Control group: 1.27% at 3 months and 2.45% at 6 months
Using Pearson chi-squared analysis, it was found that the incidence of PJI after THA at 3 months and 6 months was significantly higher (P= 0.004 and P= 0.019, respectively) in the group that underwent THA within 3 months of hip injection. No difference was found in the 3 to 6-month group or the 6 to 12-month group.
Periprosthetic joint infection is a devastating complication of total joint arthroplasty, resulting in significant morbidity and healthcare costs. Recent meta-analysis data estimate the PJI rates to be 2.5% for surgical site infections and 0.9% for deep infections after THA.
Surgeons have been concern about the relationship between intraarticular injections and PJI. Previous studies examining the rate of PJI following intraarticular injection have yielded conflicting evidence on their impact. Many of these studies were underpowered or had long average times between injection and THA.
Statistically, there is a good chance that patients undergoing intraarticular hip injections will progress to THA within a year of the injection. The study by Werner et al reflects this paradigm and includes much shorter intervals between injection and THA than in many previous studies.
The results of this study suggest that only patients who undergo THA within 3 months of intraarticular steroid injection are at increased risk for PJI.
This study had several limitations, however, including its retrospective nature and its use of data based on coding information. Furthermore, only Medicare data were used in the study, so the results may not be generalizable to all THA patients. Moreover, follow-up was only recorded to 6 months postoperatively.
Given the morbidity associated with PJI following THA, surgeons should work to minimize infection risk and, based on this study, consider waiting at least 3 months before performing THA in patients who have had intraarticular hip injections.
More research would be helpful in setting specific parameters to reduce the risk of infection in THA patients following intraarticular hip injections.
Nicole Stevens, MD, is an orthopaedic surgery resident at NYU Langone Medical Center – Hospital for Joint Diseases, New York, New York. Ajit Deshmukh, MD, is an Assistant Professor of Orthopaedic Surgery, Division of Adult Reconstruction, Department of Orthopaedic Surgery, at NYU Langone Medical Center – Hospital for Joint Diseases, New York, New York. He is also an orthopaedic surgeon at the VA New York Harbor Healthcare System, New York, New York.