dressing (SPD) is a United States Food and Drug Administration (FDA)
approved, non-experimental device and treatment method for healing
of open wounds, that has been commercially available in the United
States since 1995. The device is manufactured by Kinetic Concepts,
Inc., San Antonio, TX, and is marketed under the brand name VAC(TM)
(vacuum assisted closure). It is currently being used in a number
of medical centers in the United States. It has had the most dramatic
impact on wound healing of any development in the past several decades.
The VACTM system employs a medical grade, reticulated, polyurethane
ether foam dressing, with 400 to 600 um size pores that maximize
tissue growth. Embedded in the foam is a non-collapsible evacuation
tube that is connected to a bedside vacuum unit, which creates a
specified subatmospheric pressure over the wound. Side ports in
the evacuation tube allow communication to its lumen, while the
open cell nature of the foam ensures equal distribution of any applied
(subatmospheric) pressure to every surface of the wound in contact
with the foam.
The SPD sterile foam dressing is trimmed at the bedside in a clean
fashion to the appropriate size for each individual wound. The foam
dressing is placed into the wound, allowing the evacuation tube
to exit parallel to the skin surface. For very large wounds, multiple
foam dressings are placed in contact with one another. Provided
the foam dressings are in contact with one another, subatmospheric
pressure transmitted to one foam is equally transmitted to all contiguous
foam dressings. The surface of the wound containing the foam dressing
is covered with an adhesive drape (Ioban(TM)), that extends 5 cm
beyond the margins of the wound, onto adjacent intact skin, to create
an airtight seal. The open wound is thus encased in a controlled,
closed environment. The evacuation tube is located to avoid bony
prominences and other stress intolerant tissues, so it does not
become a source of pressure on adjoining tissues. The proximal end
of the evacuation tube leads to a remote collection canister, into
which the effluent from the wound is drawn when subatmospheric pressure
is applied. Sensing devices are incorporated into the VACTM System
collection canister, so that warnings are sounded when the canister
is filled, to avoid uncontrolled, excessively rapid fluid egress.
The magnitude of the subatmospheric pressure applied, and whether
the vacuum application is continuous or intermittent is adjustable
[Argenta, et al. 1997].
Russian medical literature describes the use of a "vacuum"
version of SPD to heal wounds as early as 1966 [Mirazimov, et al.
1966]. German surgeons published reports of their use of SPD therapy
on wounds in 1993 [Fleischmann, et al. 1993]. In the United States,
a plastic surgeon began placing patents on his version of SPD in
the early 1990s [Zamierowski 1990]. At approximately the same time,
Argenta and Morykwas, of the Bowman Gray Medical Center Department
of Plastic Surgery began work on the current commercially available
version known as Vacuum Assisted Closure? (VAC?). Kinetic Concepts,
San Antonio, TX, the manufacturer obtained FDA approval for the
VAC? and has marketed it since 1995. The Argenta-Morykwas team published
their landmark articles on SPD in 1997 [Argenta, et al. 1997; Morykwas,
et al. 1997]. Their animal and human studies showed SPD to be effective
in reducing edema, increasing local blood flow, decreasing bacterial
wound count, promoting granulation tissue formation, and closing
most varieties of open wounds. In applications to date, no serious
complications have been reported that are attributable to SPD.
A review of the pathophysiology of subacute and chronic wounds helps
explain how SPD treatment works in enhancing wound healing. Edema,
infection, and poor blood flow are conditions that impair wound
healing. Landis showed that edema detrimentally increases interstitial
pressures and venous congestion and decreases capillary flow [Aston
1997]. Also, by mechanisms not completely understood, edema of chronic
wounds has been shown to inhibit the cells crucial to wound healing
[Falanga, et al. 1994]. SPD treatment reduces edema, increases local
blood flow, and decreases bacterial wound count to a greater degree
than WTMD. These vulnerary effects, in turn, stimulate wound healing
and granulation tissue formation necessary for regenerative skin
coverage and wound repair.
To date SPD treatment of amputation wounds has been limited. This
application, however, especially in treatment of traumatic amputation
wounds, such as those incurred from land mines where immediate closure
is contraindicated because of wound contamination from (blast) injury,
offers special promise. In the 1960's and early 1970's, progress
in improving amputation wound healing was made with introduction
of enhanced surgical procedures, including osseous beveling, myodesis,
neurovasculature ligation, musculocutaneous flap rotation, incorporation
of Penrose drains, etc.; and with development of immediate post-operative
prosthetic fitting (IPOP) techniques and rigorous rehabilitative
care programs [Weiss 1966, 1970; Schrock, et al. 1968; Burgess,
et al. 1969]. Enhanced results were reported under the comprehensive
and closely coordinated rehabilitative and prosthetics care programs
developed at the respective institutions [Burgess, et al. 1968;
Goldbranson, et al. 1967; Mooney, et al. 1971; Wu and Krick 1987].
However, at other centers without closely managed, comprehensive
surgical and rehabilitative care programs, only moderate, or no,
improvement in outcome was obtained [Cohen, et al. 1974; Imparato
1974; Kane and Pollak 1980]. Because of this, and the extra expense
and effort entailed in IPOP treatment and rehabilitative care, soft
dressing treatments of amputation wounds, with delay of residual
limb prosthetic fitting and patient rehabilitation until completion
of healing, has remained the most common practice. For complex,
open amputation wounds this is almost invariably true. However,
no controlled, comparative studies, stratified by wound type and
complication, have been performed to date to establish treatment
efficacies, or general indications and contraindications . There
is no evidence to date showing improved outcomes with either IPOP
treatment and immediate post-surgical rehabilitative care, or with
saline WTMD treatment and post-healing rehabilitative care. Research
in amputation wound healing conducted more recently has been principally
directed toward predicting the most distal level at which a limb
will heal following amputation, and thus obviate the need for revision
or more proximal reamputation [Ray, et al. 1997; Malanin, et al.
1998; Padberg, et al. 1996; Mears, et al. 1996; Boyko, et al. 1996;
Bunt and Holloway 1996; Wutschert and Bounameaux 1997; Holloway,
et al. 1976 ]. This is because below-knee amputees' (BKA's) residual
limbs are biomechanically more functional, stable, and strength
and energy efficient than are more proximally amputated limbs. As
such, BKA's evidence a much higher rehabilitation success rate than
AKA's [Rutherford 1995]. Thus, it is desirable to salvage BKA limbs
whenever possible. SPD treatment can substantially contribute toward
achievement of this goal.
A research study currently underway at the New York University School
of Medicine and the Department of Veterans Affairs New York Harbor
Health Care System is comparing the efficacy of SPD treatment versus
conventional WTMD treatment in a controlled investigation of patients
with complicated and open BKA wounds (the group that evidences the
highest rate of wound complication and limb salvage failure). This
study includes: quantitative measurement of wound geometry (volume,
surface area, and depth) versus treatment time, control for patient
vascularity, smoking, history of diabetes, state of health and nutrition,
plus measurement of changes in cellular and molecular determinants
of healing, e.g., growth factor expression, matrix metalloproteinase
production and activation, and the ability of the wound effluent
to stimulate cell division and collagen gel contraction. A future
study comparing SPD and IPOP treatment is also planned to establish
the relative performance and efficacy, and indications and contra-indications
for each of the three regimens in treating cases of trauma, vascular
and other systemic disease, and cancer. Preliminary results to date
indicate SPD to be the treatment of choice in traumatic cases. Results
of the NYUSM/VA NYHHCCS research will more precisely define the
role of SPD, as well as that of the other traditional methods, in
treating amputation wounds of specific etiologies.
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