Topics in Medicine and Surgery

A Multifaceted Approach to the Treatment of

Bumblefoot in Raptors
J. David Remple, DVM, Dip. ECAMS

Abstract
Bumblefoot is a progressive, granulomatous pedal disease primarily affecting
large species of raptors maintained in captivity. Disease is usually initiated by
repeated trauma to weight-bearing plantar skin surfaces causing devitalization
and allowing subsequent invasion of bacterial pathogens. Treatment failure and
disease recurrence have been common, because prior regimes have failed to
address the granulomatous nature of the disease and the initiating cause. The
author found that a 4-pronged therapeutic regime consisting of (1) systemic
antibiotic therapy, (2) direct intralesional antibiotic delivery, (3) surgical de-
bridement, and (4) postoperative protective foot casting has offered the most
effective therapy for the majority of bumblefoot cases to date. The following is
a step-by-step illustrated guide to achieving each phase of therapy with an
accompanying explanation of the importance of each phase. Copyright 2006
Elsevier Inc. All rights reserved.

Key words: bumblefoot; raptors; surgical debridement; bone cement; antibiotic-

impregnated polymethyl methacrylate; foot cast

B
umblefoot is a chronic, granulomatous pedal In the author’s opinion, a 4-pronged therapeutic
disease primarily affecting large species of regime consisting of (1) systemic antibiotic therapy,
raptors maintained in captivity. The disease (2) direct intralesional antibiotic delivery, (3) surgi-
tends to become progressive, invasive, and eventually cal debridement, and (4) protective foot casting of-
disabling in the absence of appropriate therapy.1-6 fers the most effective therapy for the majority of
Pedal architecture (designed for standing on flat bumblefoot cases. Systemic antibiotic therapy helps
surfaces) and relatively heavy body weight predis- prevent the spread of infection to healthy tissues at
pose large falcons to the condition, whereas lighter- the lesion periphery. Surgical debridement reduces
bodied, perching (foot-grasping) accipitrine hawks antigen load and improves vascular perfusion within
tend to be spared. the lesion. Direct delivery of antibiotics through the
Infection appears to be seeded by two routes:
direct inoculation through skin puncture and de-
vitalization of plantar skin from bruising and un- Formerly from the Dubai Falcon Hospital, Dubai, United Arab
relenting pressure, permitting microbial entry Emirates. Presently from the Aspen Wing Bird and Animal Hos-
pital, 3904 West Eisenhower Blvd., Loveland, CO 80538 USA
into underlying pedal tissues.7 Pressure necrosis
Address correspondence to: David Remple, DVM, Dip. ECAMS,
and reduced vascular perfusion reduce immune
2209 Morning Drive, Loveland, CO 80538. E-mail:
factors as well as antibiotic delivery to the affected jdremple@earthlink.net
area.5 There is a generalized failure to degrade © 2006 Elsevier Inc. All rights reserved.
phagocytosed pathogens, which leads to chronic 1557-5063/06/1501-$30.00
granulomatous disease.4 doi:10.1053/j.jepm.2005.11.003

Journal of Exotic Pet Medicine, Vol 15, No 1 ( January), 2006: pp 49-55 49

50 Remple

intralesional placement of antibiotic-impregnated antibiotic concentration achieved with AIPMMA

polymethyl methacrylate (AIPMMA) beads achieves beads usually far exceeds the minimum inhibitory
high, granuloma-penetrating concentrations of anti- concentration for most pathogens, and organisms
biotic in lesional areas and overcomes the obstacle of classified as resistant by culture and sensitivity are
reduced vascular perfusion. Foot casting protects the often sensitive under the higher locally eluted
foot during healing after surgery and removes the concentrations.8,10
pressure and concussive forces on the foot that Several formulations of PMMA are suitable for
helped initiate and perpetuate the disease. Each of impregnation with antibiotic. The formulation pre-
the 4 components of the therapeutic regime is de- ferred by the author is Simplex P (Stryker How-
tailed below. medica Osteonics, Mahwah, NJ USA) because of its
overall workability. To be suitable for incorporation
into bone cement, an antibiotic must be water solu-
Materials and Methods ble, available in powder form (for mixing with the
polymer powder of the cement), heat stabile (to
Systemic Antibiotic Therapy withstand the heat of polymerization when the ce-
Raptors are placed on broad spectrum, bactericidal ment hardens), and bactericidal.11 Antibiotics that
antibiotics 2 to 3 days before a surgical procedure. As meet these criteria and that have been used to treat
a first choice, before culture and sensitivity testing is bumblefoot infections are aminoglycocides (amino-
performed, the author prefers injectable ticarcillin glycoside antibiotics in powder form [gentamicin
(200 mg/kg intramuscularly every 24 hours) (Ti- and tobramycin] can only be obtained in the United
mentin; Smithkline Beecham Pharm, Pittsburgh, PA, States through compounding pharmacies registered
USA). An alternative is clindamycin (100 mg/kg with the Professional Compounding Centers of
orally every 24 hours) (Antirobe; Pharmacia & Up- America), penicillins, fluoroquinolones (Pelwin 5%
John, Kalamazoo, MI, USA). If culture and sensitivity soluble powder for poultry; Wockhardt, Mumbai,
results show sensitivity to any of the above, the anti- India), and clindamycin (Cleocin HCL capsules;
biotic is continued systemically for 21 days. However, Pharmacia and UpJohn, North Peapack, NJ USA).
if there is resistance to the antibiotics above, an The amount of antibiotic that can be impregnated
aminoglycoside such as amikacin can be substituted into bone cement for optimal elution depends on
(15 mg/kg intramuscularly every 12 hours for 1 the antibiotic used. Aminoglycosides (powder form)
week) (Amikacin sulfate injection; Elkins-Sinn, Inc., are mixed with the cement polymer powder in a
Cherry Hill, NJ, USA). ratio of 1:14 (3 g/40 g packet bone cement); peni-
cillin powders are mixed in a ratio of 1:5 (8 g/40 g
Intralesional Antibiotic Delivery packet); fluoroquinolones are mixed in a ratio of 1:6
Chronic granulomatous diseases such as bumblefoot (7 g/40 g packet); and clindamycin is mixed in a
respond best to long-term antibiotic therapy and ratio of 1:6.66 (6 g/40 g packet).11
surgical debridement.7 Systemic antibiotic therapy
alone often fails to address the disease, owing to the Production of AIPMMA Beads. AIPMMA beads
intracellular location of the pathogen within the are easily made in a hospital in a variety of sizes
granuloma and the avascular nature of the lesion suitable for avian use. The beads used in the feet of
itself. raptors are optimally no larger than 2 to 3 mm
diameter, and they should be as round and smooth
Antibiotic-impregnated Bone Cement Beads. Poly- as possible to minimize damage to pedal tissues un-
methyl methacrylate (PMMA) or simply bone ce- der movement. Start by mixing antibiotic powder
ment is a biocompatible plastic acrylic used for the with cement polymer powder. Grind the appropriate
fixation of artificial joints to bones. AIPMMA beads amount of antibiotic powder in a mortar and pestle
have been used as an effective means of delivering to the consistency of talcum powder and add to the
antibiotic to an infected area in which tissue integrity cement polymer. Mix the powder compound by vig-
and vascular supply have been compromised.8 Beads orous shaking for a minimum of 2 minutes, and
are placed in an infected lesion after aggressive sur- divide into 1-g aliquots (Fig 1). Transfer the liquid
gical debridement.6,8,9 The cement is porous, and monomer into an evaporation-proof container and
when tissue fluids penetrate the pores, antibiotic is chill to 0°C in the freezer (chilling the liquid retards
leached out or eluted in high concentration for polymerization time and increases porosity in the
weeks to months.9 Toxic effects are avoided as min- cement). Quickly mix 0.7 mL of the chilled polymer
imal systemic uptake occurs from the lesion.8,10 The with a 1-g aliquot of the powder compound to a
Treatment of Bumblefoot in Raptors 51

Figure 3. The “foot rack” is constructed from 1/4-inch diameter

aluminum splint-making rod and is fashioned to fit the surgical table.
Figure 1. Antibiotic is ground to a talcum powder consistency and Sliding foot-grasping bars are padded. While cushioning the foot, the
added to the cement polymer. For working purposes, the powder padding also provides an anchor for towel clamps to hold the digits
compound is divided into 1-g aliquots (at room temperature, bone in extension. The white arrow indicates the optimal region for
cement has a working time of 3-6 minutes; therefore, this is the placement of a tourniquet (distal 1/3 tibiotarsus).
maximum amount a bead maker can fully utilize before polymeriza-
tion renders the compound unworkable).
should be as long as the expiration date of the
powdered antibiotic by itself.
homogenous, “loose batter” consistency, and load
into a 3-mL syringe. Immediately expel the liquid Surgical Debridement
dough in a line onto a sterile surface. A gloved
operator scoops tiny pieces of dough from the line Debridement is accomplished by making an incision
and rolls them between index finger and palm of the in a nonweight-bearing aspect of the foot and de-
hand into tiny smooth beads (Fig 2). briding all devitalized and necrotic tissues and exu-
Beads are sterilized by ethylene oxide or gamma dates. The goal is to reduce antigen load and convert
radiation.6,9 If ethylene oxide is used, beads must be an infected, necrotic area into a fresh vascular inci-
aerated for 24 hours to allow for dissipation of gas. sion capable of being brought into perfect apposi-
The heat-stable antibiotics listed above (in pow- tion for first intention healing.2,3,7
der form) apparently are unaffected by incorpora-
tion into PMMA.11 Therefore, the viability of these
Equipment and Instrumentation. A special foot-
holding device has proven invaluable for bumble-
antibiotics in powder form in the PMMA matrix
foot surgery (Fig 3). The device straddles the bird
and attaches to the sides of the surgical table. The
foot is gently but firmly held at the tarsus by a pair of
heavily padded sliding bars. The digits are held in
hyperextension with towel clamps fastened to the
padding, and the plantar aspect of the foot and toes
becomes directly accessible to the surgeon without
the need of an assistant.7 Hemostasis is controlled by
the anesthetist by means of a tourniquet placed on
the leg under the device (Fig 3). The size of the
tourniquet used should be no larger than a small
Nye type to avoid over tightening with damage to
nerves and tendons. During surgery, the tourniquet
is released every 3 to 5 minutes to allow for vascular
perfusion.
The surgical instrumentation required consists of
an Olsen Hegar needle holder, a #15 scapel blade
Figure 2. Shaping tiny beads from viscous cement can be chal- and handle, 1 Adson tissue forceps, 1 blunt (atrau-
lenging; however, we have found that a simple rolling motion in the matic) #3/0 (3 mm ⫻ 5 mm) oval curette, and 4
palm of the hand is the most efficient method. towel clamps.
52 Remple

Figure 4. The incision site (indicated here by the red crescent) is in Figure 6. Beads are placed in abscess caverns adjacent to, but not
a nonweight-bearing area anterior to the MTP. under, weight-bearing structures.

Surgical Procedure. The bird is placed in dorsal noticeable discomfort (Fig 6). Later, if culture and
recumbency, and the affected foot is placed in the sensitivity testing results show that inappropriate
foot-holding device. A thorough scrub of the surgical beads have been placed, the foot is simply reopened
area is performed with a stiff toothbrush to remove and appropriate beads are substituted. Because the
hyperkeratotic material, which could impede heal- beads are small, smooth, and biocompatible, they
ing of plantar integument. An incision is made in a can usually be left in the foot indefinitely without
nonweight-bearing part of the plantar skin just ante- concern. Beads placed near the surface of skin are
rior to the metatarsal pad (MTP) (Fig 4). Care usually eventually extruded in a sterile abscess. At
should be taken to avoid incising the MTP, because the end of several weeks’ elution time, any beads
this is a major weight-bearing structure and is com- causing discomfort to the foot can be surgically
posed of very slow-to-heal fibrocartilage. removed.
Debridement of fibrotic and exudative material is Incisions are closed using 4-0 monofilament nylon
accomplished with dull spoon curettes, which allow using a vertical mattress pattern.6,7 The incision
vigorous curettage without damage to vital structures edges are slightly everted to assist healing thinned-
(Fig 5). Surgery is assisted by irrigation with undi- skin edges (Fig 7).
luted pipercillin or ticarcillin from the injection vial. After surgery, an antibiotic dressing is applied to
When the abscess socket is thoroughly debrided, the incision and overlaid with a nonadhesive sterile
AIPMMA beads are placed in socket caverns and dressing (Telfa; Colgate-Palmolive, New York NY,
around, but not under, nonweight-bearing struc- USA). The metatarsus is lightly wrapped with a non-
tures. The number of 2 to 3 mm diameter beads adhesive elastic wrap (Vetwrap; 3M Animal Care
implanted depends on the size of the socket, but Products, St. Paul, MN, USA) and compressed to the
most raptor feet easily accept 3 to 5 beads without

Figure 7. Completed suture line showing slightly everted vertical

Figure 5. Curettage is accomplished with a ‘dull’ spoon curette. mattress pattern.
Treatment of Bumblefoot in Raptors 53

product provides a soft but semirigid supportive

cushion that protects healing wounds without com-
promising adjacent vascular integrity or creating
pressure ischemia. The form fit assures an even,
nonirritating pressure distribution to areas adjacent
to the wound.

Construction of the Composite Silicone

Form-fitting Shoe
Step 1: An assistant holds the bird and places the
bandaged foot, plantar side down, in a normal stand-
ing position on top of a sheet of paper, and an
outline of the foot is traced onto the paper. The
tracing extends to the ends of the digits (Fig 8).
Step 2: Equal parts of the silicone composite im-
pression material are quickly mixed until a uniform
color is achieved. The composite is formed into a
cylindrical shape, the diameter of a piece of chalk,
and placed onto the tracing. With the bird sedated,
Figure 8. A crude tracing has been made from the bandaged foot. an assistant holds the bird while the surgeon presses
Semiliquid silicone is laid onto the tracing from which the cast will
be formed. the foot and toes into the composite. At room tem-
perature, the composite has a molding time of 2
minutes and a setting time of 4 minutes. While the
contours of the foot and proximal digits (Fig 8). A foot is held motionless, composite is quickly worked
small piece of adherent padding, molefoam (Dr. into every nook and cranny along the sides of the
Scholl’s Molefoam; Schering-Plough, Kenilworth, NJ foot and toes (Fig 9). When the composite has set,
USA), measuring the length of the incision by 5 mm the foot is lifted out of the cast, and the Molefoam
wide, is laid over the incision area and pressed onto incision spacer is removed from the exterior of the
the outside of the vetwrap bandage. The padding bandaged foot and discarded.
acts to create a dead space between the incision and Step 3: The ends of the cast toes are trimmed off
the protective foot cast or “bumblefoot shoe.” just proximal to the middle digital pads of digits III
and IV and approximately 1/2 the distance along
Protective Foot Casting digits I and II. Trimming at these locations allows for
unhampered flexion while the cast is being worn.
After surgery, a foot cast or shoe is fashioned to Lastly, all excess composite is trimmed with a #11
protect the incision from pressure, contusion, and scalpel blade to finish the form-fitting, flexible ‘half
contamination, the very factors that helped initiate
the disease. Therefore, the application of protective
shoes is necessary not only for healing to occur, but
to prevent recurrence of disease. Since the first de-
scription of protective pedal appliances,3 there have
been many designs aimed at producing a better
shoe. Most of the early attempts utilized a more or
less rigid protective device that left the incision area
free of weight and pressure. While these shoes re-
lieved pressure on the incision, they often initiated
new disease by transferring weight to other areas of
the foot in contact with the hard cast.
The latest development in the evolution of
bumblefoot shoes utilizes a composite silicone den-
tal impression material modified as a cushion sup-
port for equine laminitis (Sideline Cushion Support,
Kingston, NY USA) to create a form-fitting, flexible Figure 9. The extended foot is pressed into the semiliquid silicone
support shoe.12 The rubbery nature of the cured and quickly formed around the foot and digits.
54 Remple

shoe’ (Fig 10). The cast is affixed to the foot with

vetwrap (Fig 11).
Foot casts are checked daily for signs of foot irri-
tation: picking at wraps, and so forth. Casts are tem-
porarily removed every 7 days to check the incision
and evaluate the foot for new signs of swelling or
irritation. Generally, casts are well tolerated and re-
main on feet for a period of 3 weeks. Foot casts and
sutures are removed after 3 weeks.

Discussion
Raptor bumblefoot is a complex disease that re-
quires complex and aggressive treatment, particu-
larly in advanced, severe, and long-standing cases. A Figure 11. Cast affixed to the foot with vetwrap.
5-stage bumblefoot classification scheme has been
devised by the author based on lesion severity: class
I is the mildest form and shows dermal insult with no
A frustrating feature of chronic granulomatous
underlying infection; class II shows subcutaneous
pedal disease is the tendency for recurrence, partic-
infection without gross swelling (usually scab only);
ularly in severe and advanced cases (class III-IV).
class III shows subcutaneous infection with gross
The introduction of AIPMMA beads has reduced the
swelling; class IV is an extension of class III with
recurrence rate in all surgical classes in our opinion
infection of tendons and bone; and class V is a
by more than 50% over previous treatment regimes.
progression of class IV producing loss of pedal func-
The silicone ‘half-shoe’ protective cast is the latest
tion.7 The 4-pronged treatment approach described
advancement in an evolution of foot-casting meth-
above represents the latest in an evolution of
ods. The silicone casts are comfortable and well
bumblefoot treatment attempts. This treatment ap-
tolerated, and allow full pedal function while being
proach, particularly since the addition of AIPMMA
worn. These shoes have been used successfully on
beads to the regime, has resulted in a dramatic
hundreds of hunting falcons in Dubai, United Arab
improvement in the treatment of all surgical disease
Emirates, with excellent results.6 On several occa-
classes (class II-IV), and it has been used successfully
sions, falcons were prematurely released to their
on hundreds of raptors throughout the world.6
owners for hunting purposes with foot casts still on.
The falcons were returned to the hospital for foot-
cast removal weeks later after successful hunting,
with the foot casts still intact.

References
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of Prey (ed 1). Saul, Gloucestershire, England,
Standfast Press, 1978
2. Riddle KE: Surgical treatment of bumblefoot in rap-
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Advances in the Study of Raptor Diseases. Keighly,
West Yorkshire, England, Chiron Publications, 1980,
pp 67-73
3. Remple JD, Remple CJ: Foot casting as adjunctive
therapy to surgical management of bumblefoot in
raptorial species. J Am Anim Hosp Assoc 23:633-639,
1987
4. Remple JD, Al Ashbal A: Raptor bumblefoot: another
look at histopathology and pathogenesis, in Redig
PT, Cooper JE, Remple JD, Hunter DB (eds): Raptor
Biomedicine. Minneapolis, MN, University of Minne-
sota Press, 1993, pp 92-98
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Treatment of Bumblefoot in Raptors 55

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MN, University of Minnesota Press, 1993, pp 154-160 dental impression material to create a form-fitting,
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295:63-76, 1993 ing in bumblefoot, in: Proceedings, 8th EAAV Con-
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