CORR Insights®: Low Reinfection Rates but a High Rate of Complications in THA for Infection Sequelae in Childhood: A Systematic Review

Where Are We Now?

All arthroplasty surgeons dread infections. My own discomfort regarding infections arises from the reality that I still do not really understand how or why infections occur. Although we have made great gains over time by improving our understanding of surgical sterility, antibiotics, pathogens “hiding” in biofilms, host susceptibilities, and microbiomes, we still do not know why any given patient becomes infected, barring rare instances of overt contamination. In many ways, our understanding of periprosthetic joint infection (PJI) is like our understanding of cancer [4]; we know many of the details and pathways, and we have won some isolated battles, but our most-basic questions of how and why remain unanswered, and our overall ability to cure it has not dramatically improved.

Given our deep-seated dread of infection, it is natural for us to hesitate to offer THA to a patient who has had septic arthritis as a child. Is the childhood infection still hiding in the joint? Does the patient have some immune abnormality that puts him or her at a higher risk of developing PJI? We do know that joints with a history of PJI may later become infected again with the same pathogen, suggesting a mechanism of “hiding” in these recurrences [6]. We also know that patients with a history of PJI in one joint have a much higher chance [1] of having a subsequent infection at a different site joint arthroplasty, suggesting the presence of inherent deficiencies in host immune function. However, given the low prevalence of childhood septic arthritis and the time between childhood septic arthritis and adult arthroplasty, it is difficult to methodically evaluate the risk of arthroplasty after childhood septic arthritis.

The authors of the current study [2] suggest with caution that although the overall risk of complications may be higher, only 1% of adult arthroplasty patients with a history of childhood septic arthritis developed PJI at a mean follow-up of 9.1 years. While their methods of a systematic review (11 studies with 691 patients) may provide a best-case scenario, and in so doing they likely underestimate the risk of PJI, it appears that performing hip arthroplasty on a patient who had childhood septic arthritis does not expose the patient to a disastrously high risk of PJI. However, although they observed relatively few PJIs, the authors did find that serious complications were fairly common (11% overall), including nerve palsies and femoral fractures, which are not surprising given the residual deformities observed in the proximal femur after childhood septic arthritis. In light of these discoveries, I believe surgeons should take appropriate steps such as a joint aspiration to evaluate for active infection, but then focus emotional and surgical efforts on avoiding mechanical complications, as it appears that these are far more likely than infection.

Where Do We Need to Go?

If the findings of this systematic review can be replicated in robust registry settings, it would relieve both surgeons and patients of the fear that a problem from the distant past would mysteriously come back to haunt them. This would allow surgeons to recommend surgery with somewhat more confidence to a population of patients who are disproportionately likely to have painful arthritis at a younger age, and also would likely reduce the delays prior to surgery that I think occur in many patients with a history of childhood septic arthritis. This is all positive.

However, we really do need to replicate and validate these findings and realize the limitations and potential problems with such an analysis. Do we really trust the diagnosis of septic arthritis as it was made in some older papers that systematic reviews like this one [2] will capture? How sure are we that the follow-up in those older papers was complete and accurately identified all postoperative infections? If we are not sure, then we must question the conclusion that the risk of PJI in patients with a history of septic arthritis is low.

In addition to replicating and validating the results of this systematic review, there remain other interesting and relevant questions. Do we have a work-up that can help identify those patients that do become infected? How long after pediatric septic arthritis should we wait before arthroplasty? Historically, hip arthroplasty in the setting of deformity often has resulted in a high risk of complications, but shouldn’t modern techniques lower this risk?

How Do We Get There?

Several recent advances should facilitate an even-better understanding of the impact of childhood septic arthritis on adult arthroplasty, including the use of electronic medical records, improved diagnosis of childhood septic arthritis [3], standardized tools to define PJI in research [7], and advances in arthroplasty techniques in the setting of deformity [5]. These improvements should be leveraged to confirm the results of this systematic review [2] and to redefine the modern complication rate in THA among patients with a history of pediatric septic arthritis.

As much as we would like prospective data on this topic, it is nearly impossible to conduct a multicenter prospective trial on patients with childhood septic arthritis, as the low prevalence and long necessary follow-up make such a study impractical in the extreme. However, as the current systematic review demonstrates [2], smaller retrospective studies are possible, and when they are considered in aggregate, they can be quite helpful. This will be even more true going forward as widespread EMR utilization, better coding, and larger healthcare networks should facilitate the ability to identify modern series of adult patients having THA after childhood septic arthritis. Furthermore, modern definitions of PJI [7] would provide standardization to outcomes, providing a higher quality of analysis when modern case series are combined.

Additionally, it is important that modern series carefully specify the time from childhood infection to arthroplasty, providing our field with a better understanding of whether the quiescent period has an impact on PJI rates after arthroplasty. The reliability and low risk of modern arthroplasty has increased the willingness of surgeons to perform THA on young patients. Therefore, it would be very useful to know how important it is to delay THA for a certain number of years after a childhood infection, and if it is important, how long that period should be in order to maintain a low risk of PJI after THA.

Finally, future studies should assess whether modern THA techniques can reduce the overall risk of complications that were observed in this systematic review. Many of the case series included in the review reflect the performance of THA as performed 20 to 30 years ago. We have newer, more-reliable techniques for surgeons tackling difficult hip deformities [5]. Modern series should carefully document the use of modular tapered revision stems, porous metal augments, and head size as these modern solutions to complex anatomy may impact risk of overall complications seen in studies from decades past. If it is true that the risk of PJI in these patients is low, then mitigating the mechanical complication rate would a good goal for future studies.