At the weekend his off (right) hind leg was fitted with an external skeletal fixation device, replacing the custom fabricated brace which was fitted last Thursday.
Doctors decided the surgery was necessary because of the development of a deep subsolar abscess secondary to bruising.
"It is not laminitis but the undermining of the sole and part of the lateral heel region are potentially just as serious. We attempted to manage the right hind foot in a cast and then in a custom fabricated brace but it was impossible to have access to the foot for treatment as well as acceptable stability and comfort," Dr Dean Richardson said.
"We elected to place his right hind in an external skeletal fixation device in order to provide the foot a chance to heal."
Two steel pins have been placed transversely through his right hind cannon bone, and are connected to external sidebars that in turn are connected to a lightweight alloy foot plate. This results in the horse eliminating all weight bearing from the foot; his weight is borne through the pins across his cannon bone.
"There is significant risk in this approach but we believed it was our only option given the worsening of the right hind foot problem. The major risk of the external skeletal fixation device is that the bone bearing the weight can fracture. Unfortunately, we felt we needed to take this risk because this approach offered our only hope of keeping Barbaro acceptably comfortable,"Dr Richardson said.
Barbaro recovered well from the anesthesia and has been in and out of the sling since then. Dr Richardson said Barbaro's left hind (laminitic) foot appears to be stable. Both front feet are of concern to the medical team.
But Barbaro is a fighter: "Remarkably, his attitude and appetite were excellent overnight," Dr Richardson said.
"We will continue to treat Barbaro aggressively as long as he remains bright, alert and eating. This is another significant setback that exemplifies how complex his medical situation remains because both hind limbs have major problems."
Barbaro remains in the Intensive Care Unit of Penn's George D. Widener Hospital at New Bolton Center.