Comparison of wound irrigation solutions using an ex vivo human bone organ culture model

Author(s):
Hugh Jones; Mark Coggins; Angus Brooks; Catherine Ambrose; Steven Schroder; David Doherty; Kenneth Mathis; Robert Frangie; David Rodriguez

Background:

It is estimated that by 2030 total knee arthroplasties (TKA) will reach 3.5 million. As this number grows, the number of revisions increase with some estimates being as high as 12%. There are several mechanisms of TKA failure with infection being the leading factor (29.3%). Use of intra-operative irrigation solutions which balance antimicrobial efficacy and host cell toxicity can be an effective strategy in reducing infection. In this study we evaluate 7 irrigation fluids using a human ex vivo organ culture method to best replicate the infection site.  The solutions evaluated use an array of antimicrobial agents, including acids and surfactants, chlorhexidine gluconate (CHG), benzalkonium chloride, polyhexamethylene biguanide (PHMB), and povidone iodine.

Hypothesis:

Ex vivo models that include the geometric and biochemical environment can provide insight into the performance of irrigation fluids

Methods:

Human femoral heads were collected during total hip arthroplasty. Cancellous bone cores were harvested and inoculated with S. aureus in media best replicating human serum. Half of the cores were treated with the irrigation solutions and the remaining patient matched cores were washed in saline. CFU counts were compared both acutely and 24 hrs after treatment. Other treated cores were incubated in a dynamic bioreactor system that provide the biochemical and mechanical environment for bone. These specimens were metabolically and histologically compared to saline controls.

Results:

PHMB and CHG containing solutions showed acute reductions greater than 3-log (Fig 2). After 24 hrs of incubation, PHMB and acetic acid formulations reduced by 6-log.

Conclusions:

Conclusions: While standard in vitro cell culture has a place, use of more complex and relevant models, such as the ex vivo model described here, can provide more insight as the biochemical environment impacts both bacterial metabolic activity and antimicrobial efficacy.