The PARITY Trial

7/30/2023:

Interesting topics from the Journal of Bone and Joint Surgery American Edition July 19, 2023. 

This appears to be somewhat of an orthopaedic oncology themed edition, with much regarding the PARITY trial, which was a 604 patient multi-center randomized controlled trial looking at infection rates for patients that underwent resection and endoprosthesis reconstruction with 1 or 5 days of IV antibiotics.  They concluded that 1 day regimen of cefazolin or cefuroxime was sufficient.

They subanalyzed the group to look at 388 cemented versus 115 uncemented implants and looked at reoperation rates at 1 year.  While 131 reoperations were identified (is that a large number??), there were no differences between cemented and uncemented for all cause reoperation, septic or aseptic reoperations.  This would make sense, specifically for cemented/uncemented as these will usually fail 5-10-20 years along the line.  They did find that for every hour, there was a small 10% increase on the risk for reoperation (likely due to infection).  10% sounds like a lot, but that is a 10% increase on the absolute value (which may be 2-5%, thus the increased total risk is 2.2-5.5%).

Another subanalysis looked at whether drain use or negative pressure wound therapy (NPWT) would have an effect on surgical site infections.  409 patients received a drain, while only 15 patients received NPWT, and 68 patients received both.  While use of any of these modalities was not associated with infection (p=0.14), drain use longer than 14 days and operation length greater than 8 hours was associated with surgical site infection.  This makes sense for several reasons.  First, drainage longer than 7 days is associated with infection as demonstrated by the late Dr. Kenneth Krakow in the 1980s.  Second, many studies have demonstrated that longer operative times increase risk for infection.  You can see that in the data from the sub-analysis above.  Also, this PARITY data, may have this built it now that it is seen in both of these sub-analyses.  Further analysis of this data will likely yield a similar result in another way.

An additional subanalysis asked the question: does postop infection provide a progression free survival benefit at 1 year?  This is an interesting concept.  There were a few studies in the late 2000s, one in dogs, and one retrospective in humans that suggested patients with osteosarcoma undergoing resection and reconstruction, if they developed a postoperative infection that it conferred a survival benefit (Lascelles Surg Oncol 2005, Jeys Ann Surg Oncol 2007).  This study of 274 patients with osteosarcoma reported no association between postoperative infection and one year progressive free survival. 

Finally, an institution well known to me, UC Davis sub-analyzed if a 5 day course of post operative antibiotics could lower risk of surgical site infection if duration of surgery was longer.  They looked at all 604 patients and determined if surgical duration had an effect on SSI.  It did, with surgeries longer than 6.2 hours were associated with SSI and less than 5 hours were associated with lower SSI.  They did not find a lower rate of SSI in the group that had 5 days of antibiotics.

Ultimately, we know that longer operative time can increase the risk for infection.  Surgical sites are not sterile, no matter how much we prep.  The prep is only good for 3 hours, and we ultimately rely on the human body to clear it’s own bioburden as we reduce the load or count.  To me, these studies represent the notion that it is important to be a good surgeon, but to also have a plan and be expeditious.