Composite graft design.
Mean percentage of graft survival
in the control and treatment groups for the 1.5 × 4.0-cm composite graft.
Mean percentage of graft survival
in the control and treatment groups for the 1.0 × 3.0-cm composite graft.
Renner G, McClane SD, Early E, Bell P, Shaw B. Enhancement of Auricular Composite Graft Survival With Hyperbaric Oxygen Therapy. Arch Facial Plast Surg. 2002;4(2):102-104. doi:
From the Division of Otolaryngology–Head and Neck Surgery, University
of Missouri, Columbia.
Objective To continue investigation regarding the efficacy of hyperbaric oxygen
(HBO) therapy in improving survival of reattached auricular composite grafts.
Design A prospective, randomized, double-blind study using 20 New Zealand albino
rabbits randomized to a treatment or control group. The treatment group received
30 HBO treatments over 19 days following amputation and reattachment of composite
auricular grafts. The control group received standard care. Ears were examined
grossly and microscopically on postoperative day 21 to determine the percentage
of graft survival.
Results The mean percentage of graft survival for the 2 separate grafts (a larger
1.5 × 4.0-cm and a smaller 1.0 × 3.0-cm graft) in the treatment
group was 26.5% and 27.9%, respectively. The mean percentage of graft survival
for the larger and smaller graft in the control group was 9.7% and 14.0%,
respectively. An analysis of variance test was used to evaluate this difference,
which was found to be statistically significant (P
Conclusions This study represents a continued investigation following a pilot study,
which suggested some enhancement of composite graft survival with the use
of HBO therapy in the rabbit ear. Both experiments have demonstrated a slight
survival benefit using HBO therapy in auricular composite grafts in the rabbit
FACIAL PLASTIC and reconstructive surgeons have long recognized the
challenges set forth with the traumatically amputated auricle.1
Investigators have tried to improve survival with various pharmacological
agents and surgical techniques.2-9
Microvascular anastomosis is ideal but is generally not a possibility owing
to severe vascular and soft tissue destruction and small vessel size.10-11
Hyperbaric oxygen (HBO) therapy has several medical applications (eg,
augmentation of wound healing, treatment of decompression sickness, and therapy
for osteoradionecrosis). Hyperbaric oxygen therapy is believed to help prevent
white cell–mediated damage related to reperfusion injury.12
It also helps promote angiogenesis and enhanced oxygen delivery to body tissues.12 Multiple studies have been conducted to further evaluate
the use of HBO in tissue healing.12-17
McFarlane and Wermuth15 studied the effect
of HBO in preventing necrosis in pedicle flaps and composite skin grafts.
Their treatment groups received 1, 2, or 3 atm of absolute pressure.
Our initial pilot study18 demonstrated
an enhanced mean percentage of graft survival with the use of HBO therapy.
The design of the pilot study included 2 separate auricular composite grafts
in the rabbit model, one at the tip of the ear and the other in the thicker
base portion of the ear. In the present study, grafts of 2 different size
were made only in the base portion of the ear. In both studies, after amputation
and reattachment of the grafts, 10 rabbits received a series of HBO treatments,
and 10 rabbits received routine postoperative wound care. The rabbits in the
treatment group in both the present study and pilot study demonstrated a slightly
improved graft survival.
We noted several problems with the rabbit as a model for these studies,
but were encouraged by our initial findings, which prompted further investigation.
Accordingly, this second study was undertaken to reconfirm the initial findings
and to hopefully further define the role of HBO therapy in improving survival
of auricular composite grafts.
The basic protocol used in the pilot study18
was repeated in the present study with a few significant design changes; this
is a prospective, randomized, blinded, controlled study. Twenty adult New
Zealand albino rabbits, weighing from 1.4 to 1.8 kg (3-4 lb), were obtained
from an approved rabbitry. The rabbits were housed in a university-approved
animal research laboratory and fed a standard rabbit diet. The Animal Care
and Use Committee at the University of Missouri, Columbia, approved this investigation.
Investigators participated in a training course in animal care, and guidelines
were followed to ensure humane care of the rabbits.
Technicians from the university's Office of Laboratory Animal Medicine
provided anesthesia support and monitoring. Xylazine hydrochloride (7 mg/kg)
and ketamine hydrochloride (33 mg/kg) were administered subcutaneously as
the preanesthetic agent. Isoflurane was used as the principal anesthetic agent.
The ears were shaved and then prepared with an iodine solution. The animals
were brought to the operative room where their ears were measured and marked.
An independent assistant randomized the rabbits to (1) treatment and
control groups, (2) right vs left ear to undergo amputation first, and (3)
which size graft to be used in the right vs left ear. Two types of composite
amputation and reattachment were performed on each rabbit with only 1 graft
performed on each ear. One graft design was identical to that used in the
pilot study, a vertically oriented, rectangular shape measuring 1.5 ×
4.0 cm located near the base portion of the ear (Figure 1). The second composite graft used in this study was similar
in shape and placement but measured 1.0 × 3.0 cm (Figure 1). In each ear, the excised segment was reattached using
only 6-0 nylon skin sutures. The suture was used to reapproximate the epidermis
and subcutaneous tissue on each side of the ear. No cartilaginous, through-and-through
sutures or supportive dressing were used. Detachment time was recorded.
Buprenorphine hydrochloride (0.05 mg/kg) was given immediately following
surgery and again 12 hours later for pain control. The rabbits were monitored
until they adequately recovered from anesthesia. A protective collar that
extended to the level of the ears was placed around each rabbit's neck to
minimize manipulation of the grafts by the rabbits. Mupirocin (Bactoderm;
Pfizer Inc, New York, NY) ointment was applied to the ears postoperatively.
Of the 20 rabbits, 10 were randomized to the control group, and 10 to
the treatment group. The treatment group received 90-minute treatments of
100% oxygen at 2.0 absolute atmospheres. Treatments were administered 3 times
a day for the first 2 days, twice daily for the next 7 days, and then only
once daily for the next 10 days. Over 19 days, 30 treatments were administered;
in the pilot study, 14 treatments were given over 10 days. Because the pilot
study had suggested some survival benefit with HBO therapy, we believed that
a more aggressive treatment regimen may show further enhancement of graft
An HBO chamber had been constructed by the Science Instrument Technology
Services at our institution. We consulted with the Division of Hyperbaric
Medicine at our institution and various other facilities for advise regarding
construction of the chamber and recommended treatment regimens used in this
protocol. The chamber was constructed of stainless steal and Plexiglas (Röhm
GmbH & Co KG, Darmstadt, Germany) with cylindrical design. Instrumentation
included oxygen hose, an oxygen monitor, pressure gauge, venting device, safety
pop-off valve, and flow regulators. The oxygen level within the chamber was
continuously monitored by an oximeter to ensure that the chamber remained
at 100% oxygen. Continuous pressure monitoring was accomplished with a pressure
gauge. Experience at other centers reportedly has not shown oxygen toxicity
to occur at these treatment levels.
On postoperative day 21, each ear was examined both grossly and microscopically.
Nonviable tissue was debrided. The amount of graft that survived was measured
and recorded. The surviving graft was compared with the initial area of graft
harvested. The surviving graft area was then recorded as a percentage of the
initial graft harvested. This same protocol was used and described in our
pilot study.18 Calculations were then made
to determine the total area and percentage of graft survival.
The Technology Integrated Services Division at the University of Missouri,
Columbia, performed all statistical analysis using SAS statistical software
(SAS Institute Inc, Cary, NC). The percentage of graft survival was the primary
outcome variable. Covariables evaluated included reattachment time, right
vs left ear, surgeon, and graft size used. These items were statistically
analyzed using the SAS system. P<.002 was considered statistically
For the covariables evaluated, no statistically significant differences
were observed in reattachment time, right vs left ear, or surgeon. Regarding
the composite graft measuring 1.5 × 4.0 cm, the percentage of graft
survival for the rabbits receiving HBO treatments was 26.5%, while the percentage
of graft survival for the control group was 9.7% (Figure 2). Regarding the composite graft measuring 1.0 × 3.0
cm, the percentage of graft survival for the treatment group was 27.9% and
14.0% for the control group (Figure 3).
The percentage of graft survival between the treatment and control groups
was significantly different (P = .001). As expected,
the portion of the graft that survived was found adjacent to the anastomosis.
A single death occurred. A staff veterinarian examined the rabbit, and
the death was believed to be secondary to hyperthermia and not HBO.
Facial plastic and reconstructive surgeons have long recognized the
challenges inherent to traumatically amputated auricle. Simple reattachment
has often met with failure in survival of the detached portion. Hyperbaric
oxygen therapy has several therapeutic applications. Twelve disorders are
approved for the use of HBO.12-13
We have previously completed a pilot study investigating the efficacy of HBO
therapy in improving survival of reattached auricular composite grafts in
the rabbit.18 An enhancement in survival noted
in the pilot study prompted this investigation to reconfirm this preliminary
finding and better define a role for HBO therapy with respect to the traumatically
In 2 separate studies we have now observed a slightly better composite
graft survival in the group of rabbits receiving HBO treatments. In the rabbit
model we have used composite grafts of fairly large size in an attempt to
mimic the condition of a major human auricular avulsion injury. Because the
rabbit ear is quite different from that of a human, this is only a fair model
at best. We had no success in survival using large composite grafts at the
tip portion of the rabbit ear either with or without the use of HBO therapy
in our previous study. We have found partial survival (involving tissue near
the interface of reattachment) of large composite grafts in the base portion
of the rabbit ear where both the cartilage and the soft tissue is thicker,
which allows for a more satisfying apposition of tissues along the margins
of reanastomosis. We believe that tissue in the base portion of the rabbit
ear more closely resembles that of the human ear compared with tissue at the
tip of the rabbit ear. Although we recognized the limits of the rabbit as
a model comparable with the human auricle, we believe that the findings from
this study give support to the use of HBO therapy in the treatment of reattached
auricular composite tissue. We encourage further study of this subject.
Accepted for publication September 10, 2001.
This research project was funded by the American Academy of Facial Plastic
and Reconstructive Surgery and by the 1999 Resident Research Grant Award.
This study was presented at the Combined Otolaryngological Societies
Meeting, Orlando, Fla, May 12-15, 2000.
We wish to thank Richard Madsen, PhD, Division of Biostatistics, University
of Missouri, Columbia, for performing the statistical analysis. We appreciate
the assistance with animal care given by the members of the Office of Laboratory
and Animal Medicine and express our thanks to the Division of Hyperbaric Medicine
at the University of Missouri, Columbia, for their guidance.
The views expressed in this article are those of the authors and do
not reflect the official policy or position of the Division of Otolaryngology–Head
and Neck Surgery, University of Missouri, Columbia.
Corresponding author: Stacie D. McClane, MD, 111 Beechwood Rd, Apartment
2, Fort Mitchell, KY 41017 (e-mail: firstname.lastname@example.org).