Biomedical Engineering Reference
In-Depth Information
using ECM-based graft materials for tissue repair depends greatly on not only
the implant material, but also on the ability of the patient to accept such a
bioactive implant that requires `self' to be successful and the surgical technique
that is used to implant it.
Evidence suggests that healthy people are less likely to have complications
when biologic grafts are implanted than are the elderly and frail. Consider, for
example, the years of successful outcomes in preclinical animal models where
healthy animals were used to test biologic implant grafts, or the high rates of
success and minimal complications observed when trained athletes are
implanted with biologic mesh to treat `sports' hernias (Edelman and Selesnick,
2006). Conversely, obese, diabetic patients who also use nicotine on a regular
basis are a more challenging lot and are susceptible to poorer outcomes and a
higher incidence of complications (Misra et al., 2008). It has been shown, for
example, that people who smoke or have diabetes are less likely to achieve
successful closure of their anal fistulas following placement of a biologic mesh
plug than are their non-smoking or non-diabetic counterparts (Schwandner et al.,
2009). Clearly, we have much more to learn about the individual patient
characteristics that can affect clinical outcome when biologic implants are used
for tissue repair, but it is obvious that since the ECM graft depends on intimate
interaction with the patient's tissues to be successful, the health of the graft
recipient is a determining factor in the eventual outcome achieved. That is not to
say that success cannot be achieved in the face of critically ill patients. Clearly,
biologic graft materials have been successful in treating diabetic skin ulcers
(Niezgoda et al., 2005) and have their place in treating grossly contaminated
wounds (Helton et al., 2005); however, the healthier the patient, the better the
likely outcome.
In addition to the nature of the graft and the characteristics of the individual
patient recipient playing a role in the outcome of a biologic implant, pristine
surgical technique that adheres to historical surgical tenets is critical to
achieving a successful outcome absent of complications. For example, Edelman
and Selesnick (2006) and Fine (2006) report recurrences that occurred following
implant of a biologic graft material to repair direct inguinal hernias and attribute
the failures to inadequate size of the graft material used. Additionally, Knoll
(2007) has discovered that, much like synthetic materials, biologic graft
materials shrink after implant and that this shrinkage needs to be considered
during surgical placement. In his report on treating Peyronie's disease, Knoll
reports that oversizing the graft by 30% when sewing it in is important in
preventing recurvature of the penis. While the shrinkage observed with
synthetics is likely to cause pain and discomfort as the material scars into the
surrounding tissues, the shrinkage that occurs when decellularized biologic
grafts are used is more likely to cause recurrence. Clearly, broad overlap of the
biologic graft with the adjacent tissues ± as much as 5 cm in all directions for
hernia repair ± is essential to preventing recurrence (Klinge et al., 2005).
