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Evidence Corner: September 2006
Laura L. Bolton, PhD, FAPWCA
Wounds. 2006;18(8):A19,A20-A22. ©2006 Health Management Publications,
Inc.
Posted 10/10/2006
Dear Readers
To heal a chronic wound, one diagnoses and alleviates the cause of tissue damage then
debrides necrotic tissue and provides an appropriately moist environment for healing.[1]
Without effective debridement, necrotic tissue may impede healing[2] or act as a
foreign body or a focus for microbial proliferation. Clarity is emerging on clinical
efficacy of debriding modalities for chronic wounds. For example, a systematic review
of debridement efficacy reported that hydrogels are the only debridement category with
randomized, controlled trial evidence of faster diabetic foot ulcer healing as compared
to gauze.[3] More recent research reported that surgical debridement of slough or
necrotic tissue from recalcitrant venous leg ulcers hastened healing 4 or 20 weeks after
curettage compared to recalcitrant venous ulcers without slough.[4] Readers have
requested perspective on the best chronic wound evidence available on maggot therapy
or “larval debridement” to aid their clinical decision making. Special thanks go to Dr.
Sherman, author of the 2 studies summarized here, who provided me with the best
available maggot therapy evidence to supplement the MEDLINE search that was
conducted for this column.
Debriding Pressure Ulcers with Maggot Versus Conventional Therapy
Reference: Sherman RA. Maggot versus conservative debridement therapy for the
treatment of pressure ulcers. Wound Repair Regen. 2002;10(4):208–214.
Rationale: Popularity of maggot therapy (MT) has seen a recent resurgence of interest,
but there is little controlled evidence supporting it.
Objective: The objective of the study was to assess utility of MT as a debriding
modality in pressure ulcer (PU) management.
Methods: A retrospective analysis was conducted on 103 patients with 145 PUs
managed between 1990 and 1995 by the MT team in a US Veteran’s Administration
hospital setting. Wounds with osteomyelitis or rapidly advancing infection were
excluded. Patients were included in the analysis if they had nonimproving PUs as
measured for at least 2 weeks while receiving “conventional therapy,” mainly saline or
sodium hypochlorite in gauze (CT), before implementing MT. Five to 8 disinfected
Phaenicia (Lucilia) sericata larvae were applied for approximately 48 hours to each
cm[2] of wound area 1 to 2 times weekly and covered with a porous sheet of Dacron®
chiffon or nylon glued to a hydrocolloid dressing on the surrounding skin. This “cage”

2. was loosely covered with gauze, which was changed every 4–6 hours. Between MT
cycles, wounds were dressed with gauze moistened with saline or 0.125% sodium
hypochlorite. All wounds were evaluated visually, photographed, measured, and traced
every 2 weeks. Wound healing rate was calculated by dividing wound area by wound
circumference. Paired t-tests compared pre-MT versus MT healing rates.
Results: Forty-three evaluable patients received MT by convenience assignment at some
time during the study and 49 received CT. On enrollment, the MT patients had larger
PUs with higher likelihood of diabetes or spinal cord injury and higher average serum
albumin than the CT patients. Necrotic tissue and wound size decreased faster and
granulation tissue improved more during the first 4 weeks of treatment in the MT
compared to CT patients (P < 0.05), though healing time and the percentage of wounds
healed after 12 weeks were not significantly different between the 2 groups. The only
variable significantly associated with PU debridement was MT. Thirty-one PUs treated
first for an average of 4.8 weeks with CT and then treated with MT for an average of 5.2
weeks increased in size during CT, then decreased in size during MT (P < 0.001).
Conclusion: These results establish the foundation for prospective clinical trials
comparing MT to other debridement modalities on PUs.
Maggot Debridement of Ulcers in Patients with Diabetes
Reference: Sherman RA. Maggot therapy for treating diabetic foot ulcers unresponsive
to conventional therapy. Diabetes Care. 2003;26(2):446–451.
Rationale: Maggot therapy selectively debrides necrotic tissue. However, the optimal
role has not been clarified in the management of chronic wounds.
Objective: The objective of the study was to determine the effectiveness of MT in
managing foot and leg ulcers (DUs) failing conventional treatment in hospital patients
with diabetes.
Methods: A retrospective analysis of the aforementioned database was conducted on
143 patients with diabetes with 260 nonhealing DUs referred to the MT service in a US
Veterans Administration hospital. Twenty wounds on 18 patients qualified for analysis.
Six DUs were treated with conventional surgical or nonsurgical therapy (CT), 6 with
MT, and 8 with CT for at least 2 weeks followed by MT. Ulcers were neuropathic in
origin for 86% of the 14 subjects receiving CT or CT+MT and 64% of the 14 subjects
receiving MT or CT+MT. Wound dimensions, area, healing rate at 4 and 8 weeks,
necrotic tissue, granulation tissue, and time to complete healing were measured.
Results: The analysis combined the 6 subjects receiving CT or MT only with the 8
subjects receiving CT first followed by MT, rendering it impossible to compare effects
of CT only with MT only. At first glance, paired t-test results for the 8 subjects
receiving CT (for “~ 5.6 weeks”) to MT (“completely debrided in 4 weeks”) appear
more compelling, reporting statistically significant effects on necrotic tissue and wound
area. However, the most common CT debridement modality was wet-to-dry gauze,
currently recognized as substandard care.[7] Only 1 CT patient received hydrogel, a
debriding modality with evidence supporting healing efficacy in diabetic foot ulcers.[3]
Percent of DU closed during 4 weeks did not reach statistical significance (0% for CT
compared to 14% for MT).

3. Conclusions: While the results are interpreted as supporting efficacy of MT as
compared to CT on DUs, many questions remain unanswered, and a large prospective
trial is warranted.
Clinical Perspective
The Cochrane conclusion agrees with the conclusions of these MT articles. While the
evidence is insufficient to support a firm conclusion of efficacy of larval therapy in any
chronic or acute wound, appropriately powered prospective, randomized, controlled
trials (RCTs) are warranted. When these RCTs are conducted, it is hoped that MT will
be compared to a hydrogel under a moisture-retentive dressing, a modality with
significant evidence of debriding efficacy during 14 days of use.[5]
Valuable lessons can be learned from this literature. First, there is an inherent flaw in
proceeding from CT to MT and assuming that wound size reduction reflects debriding
efficacy. Necrotic tissue debridement is often initially associated with perceived wound
enlargement before healing proceeds to close the wound. Successive treatments should
always be conducted in completely balanced cross-over studies to control for this effect.
Second is the issue of whether to measure healing, debridement, or both. Technically,
debridement efficacy is efficacy in removing necrotic tissue. Subsequent healing varies
according to the wound environment or extent to which the cause of tissue damage has
been consistently and completely alleviated. The MT literature and some hydrogel
literature have measured both debridement and healing. For example, the only
prospective MT RCT found in the literature6 compared MT (n = 6) to a hydrogel with a
gauze (HG) secondary dressing (n = 6). In this MT RCT, only 2 HG patients as
compared to all 6 MT patients were debrided in 1 month. This result does not match
prior published hydrogel debridement results, possibly owing to differences in
application techniques or debridement measures. In a prospective RCT using validated
debridement measures, Romanelli[5] reported significant debriding efficacy of a
hydrogel (n = 16) compared to an enzymatic agent (n = 16) during the first 14 days of
therapy when both were covered with an occlusive film dressing. This literature
suggests that 1) validated measures of debridement are appropriate for comparing
efficacy of debriding agents and 2) gauze is no longer an accepted standard dressing in
debridement studies. It may be associated with substandard debriding outcomes,[6]
masking efficacy when used in conjunction with an evidence-based debriding modality,
such as a hydrogel. There is sufficient evidence to use standard validated debridement
measures5 and to avoid gauze,[7] defining a hydrogel covered with a moisture-retentive
dressing as a best practice standard debriding dressing for future research.[3]
References
1. Parish LC, Bolton LL. Evidence-based dermatology and wound healing: let’s get
real! Skinmed. 2006;5(1):6–7.
2. Saap L, Falanga V. Debridement performance index and its correlation with
complete closure of diabetic foot ulcers. Wound Repair Regen. 2002;10(6):354–359.
3. Smith J. Debridement of diabetic foot ulcers. Cochrane Database Syst Rev.
2002;(4):CD003556.
4. Williams D, Enoch S, Miller D, Harris K, Price P, Harding KG. Effect of sharp
debridement using curette on recalcitrant nonhealing venous leg ulcers: a concurrently
controlled, prospective cohort study. Wound Repair Regen. 2005;13(2):131–137.
5. Romanelli M. Objective measurement of venous ulcer debridement and
granulation with a skin color reflectance analyzer. WOUNDS. 1997;9(4):122–126.
6. Wayman J, Nirojogi V, Walker A, Sowinski A, Walker MA. The cost
effectiveness of larval therapy in venous ulcers. J Tissue Viability. 2000;10(3):91–94.

4. 7. National Institute for Clinical Excellence. Guidance on the use of debriding
agents and specialist wound care clinics for difficult to heal surgical wounds.
Technology Appraisal Guidance—No. 24. London, UK: National Institute for Clinical
Excellence; April 2001.
Laura L. Bolton, PhD, FAPWCA, Adj. Assoc. Prof., UMDNJ; WOUNDS Editorial
Advisory Board Member and Department Editor
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