HOW TO MAKE RATIONAL CHOICES FOR INTRA-ARTICULAR INJECTIONS
How to Avoid Complications Following Joint
Injections I: Site Preparation and Selection of
Needles
Stephen B. Adams, DVM, MS, Diplomate ACVS
Author’s address: Purdue University, College of Veterinary Medicine, 625 Harrison Street, West
Lafayette, IN 47907; e-mail: [email protected]. © 2012 AAEP.
1.
Introduction
Joint injections and other intra-synovial injections
are some of the most common procedures performed
by veterinarians in equine practice. Complications
are uncommon but not rare because of the high
frequency of the procedures. Injury to the veterinarian from a fractious horse kicking or striking
during the procedure may occur. Risks to the horse
include broken needles, damage to joint cartilage,
and failure to enter the joint with the needle. The
most serious complication for the horse is introduction of infectious organisms and subsequent septic
arthritis.1,2 Septic arthritis is a significant concern
in horses because joint infections can lead to a rapid
destruction of articular cartilage and irreversible
loss of joint function. Chronic lameness, debilitation, and euthanasia are potential sequelae. Treatment costs for septic arthritis are often high.
In a retrospective study of 192 horses admitted for
treatment of septic arthritis or tenosynovitis, 22% of
infections were caused by joint injections.1 In another retrospective study, sepsis in 9 of 13 horses
treated for tarsocrural joint infection was caused by
joint injection.3 In humans, the incidence of septic
arthritis following arthrocentesis is quite low, and
one study measured an incidence of 0.037% (37/
100,00).4 Other studies in humans have estimated
the incidence of infection to be less than 0.037%.
The overall incidence of septic arthritis following
intra-articular injection is not well documented in
horses and is believed by many to be higher than the
incidence in humans. In my experience, most
equine veterinarians routinely performing joint injections have experienced post-injection sepsis.
An unpublished study from one practice revealed an
incidence of 0.041% (12/29201 joint injections),
which compares favorably to the human incidence.a
Studies in horses would be useful to determine the
incidence from other equine practices and the best
techniques to avoid post-injection septic arthritis.
Iatrogenic joint sepsis following joint injections is
frequently caused by infections with Staphylococcus
species. The infective organisms causing iatrogenic septic arthritis are usually introduced at the
time of joint injection, and there are three main
sources. The surgeon’s hands can be a source of
contamination. A survey of 341 veterinarians attending a veterinary surgery conference revealed
that 17% had positive nasal swabs for methicillinresistant Staphylococcus aureus (MRSA).5 The
NOTES
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HOW TO MAKE RATIONAL CHOICES FOR INTRA-ARTICULAR INJECTIONS
hands of these veterinarians could also be contaminated with MRSA as well as many other infective
organisms. The skin of the horse is a second source
of infection. Skin can never be fully disinfected,
and contamination almost inevitably occurs when
the skin barrier is broken. Needles perforating the
skin may become contaminated prior to entering the
joint. Bacteria reside in the infundibulum of hair
follicles and in sebaceous glands and ducts where
they can reproduce. Most microbes on the surface
of the skin and on exposed hair shafts are easily
removed by disinfection. Those microbes under the
surface of the skin in the ducts, glands, follicles, and
hair roots cannot be killed and can be inoculated
into sterile tissues below the skin by a needle passing through the contaminated tissues. In humans,
after subcutaneous injection, the interiors of 2.4% of
needles and exteriors of 3.8% of needles were contaminated with microorganisms.6 The presence of
skin material in the knee joint was evaluated in 112
human patients undergoing knee arthroscopy after
insertion of spinal needles for identification of portal
sites during surgery.7 Skin fragments up to 3 mm
in diameter were visualized on the needle bevel in
the knee joints of more than 75% of patients. These
skin fragments will not all be sterile. The third
source of infective organisms that may cause septic
arthritis is contaminated medications. Contamination is most common in multi-dose vials.
The purpose of this paper is to review current
information on preventing septic arthritis following
arthrocentesis and to present some specific recommendations on skin preparation, selection of needles, and techniques for insertion of needles into
joints, which may reduce the risk of septic arthritis.
Site Preparation
The two biggest questions regarding skin preparation are (1) whether or not to remove hair prior to
scrubbing with an antiseptic and (2) what antiseptic
and scrub techniques are most effective for aseptic
preparation of the skin. Clipping of hair is thought
by many veterinarians to be essential to proper skin
preparation. However, many trainers and owners
request that hair not be removed from horses intended to show or race shortly following injections.
In one study evaluating a 5-minute povidone-iodine
scrub followed by a 70% isopropyl alcohol wipe for
injection sites over the middle carpal and distal interphalangeal joints, the presence of hair did not
appear to inhibit the ability of the antiseptics to
reduce bacterial flora compared with clipped sites.8
However, colony-forming units from swabs taken
from post-scrub samples were positive in both
clipped and nonclipped sites, and bacteria isolates
included Bacillus species, nonhemolytic Staphylococcus, and Micrococcus species. The aseptic skin
preparation in this study significantly reduced but
did not eliminate bacterial contamination.8 Although removal of hair in horses at the site of injection may not improve antisepsis of the skin at the
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injection site, the removal of a small patch of hair
directly over the location for joint puncture can
serve as a landmark for needle placement and reduce the need for digital palpation to identify the
correct anatomical site prior to insertion of the needle. Less or no digital palpation of prepped injection sites prior to insertion of the needle may reduce
the risk of contamination of gloves. This would be
especially important when multiple joints are being
injected at the same time in the same horse to prevent cross-contamination between sites.
In a recent study, the skin of five fetlock joints was
aseptically prepared for joint injection using a twostage surgical prepping technique used at Purdue
University Large Animal Hospital for surgical procedures and joint injections.9 The skin over the
fetlock joint was clipped using an electric clipper
with size 40 clipper blades. The first stage of the
procedure was a 3-minute scrub with chlorhexidine
gluconate, using a sterile scrub brush with the operator wearing nonsterile exam gloves. This was
followed with a sterile saline wipe to remove the
soap. The second stage consisted of a 3-minute
scrub with chlorhexidine gluconate with sterile
gauze sponges with the operator wearing sterile
gloves followed by removal of the antiseptic with
gauze sponges moistened with sterile saline. None
of the skin swabs taken prior to needle insertions
were positive for growth on blood agar
plates. Three of 115 (2.61%) tissue samples from
the needle punctures through the prepped fetlock
joint tissues were positive for bacteria growth when
cultured on the blood agar plates. This two-stage
skin preparation technique may decrease the surface contamination of skin compared with other
methods of skin preparation. Larger studies would
be needed to confirm this statement. However, this
method of skin preparation will not decrease the
number of bacteria in the sebaceous ducts, glands,
and hair follicles of deeper tissues. The obvious
disadvantage of the two-stage aseptic skin preparation technique is the time necessary to perform the
technique and the amount of disposable items
needed for the procedure.
Numerous techniques for aseptic skin preparation
have been described that markedly reduce contamination of the surface of the skin with bacteria.
Povidone-iodine compounds for preparation of
equine skin with the hair left intact were used as
10-minute scrubs, 5-minute scrubs, three 30-second
scrubs, and application of a one-step commercial
iodophor solution.b All four skin preparation techniques significantly reduced bacterial contamination and were determined to be acceptable.10 Recent
studies in ponies indicate chlorhexidine gluconate
compounds removed with sterile saline may be superior to povidone-iodine for one-stage skin preparation prior to joint injection.11
Routine therapeutic or diagnostic joint injections
should not be done through skin that has dermatitis
or open wounds, and a needle should not be passed
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Fig. 2. This 20-gauge spinal needle was inserted through a
clipped and surgically prepared area of skin into a joint during
arthroscopy. Note the short hair stubs that were pulled into the
joint by the needle.
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Fig. 1. Joint injections on the dorsal side of this carpus with
severe dermatitis should be avoided.
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into a joint through tissues that are swollen, edematous, or have cellulitis (Fig. 1). When time and
resources are not an impediment, I would recommend a two-stage skin preparation procedure using
chlorhexidine gluconate taking 2 to 3 minutes per
stage. We routinely use fresh gauze sponges for
each skin preparation and individual 4-ounce bottles
of chlorhexidine gluconatec for each horse. Although
wearing sterile gloves may not be critical for adequate reduction of infective organisms from the surface of the horse’s skin, the gloves will ensure that
infective microbes will not be transferred from the
veterinarian to the horse.
Several studies have since been performed to determine the incidence of joint contamination with
tissue and hair debris and the effect of needle size
and type, insertion technique, reuse of needles, and
removal of hair prior to injection on the incidence of
tissue and hair contamination.9,12 The techniques
used for this research have been previously described in detail. Briefly, soft tissue flaps, including the joint capsule, were created by dissecting all
soft tissues from the dorsal aspect of the fetlock
joints of anesthetized or euthanized horses. Needles inserted through the tissue flaps were flushed
into tissue cell culture plates that were examined for
debris with and without magnification with a 4⫻
dissecting microscope. Overall contamination in
both studies was significant, and combined data
showed tissue contamination in 90% of 2028 individual needle insertions and hair fragments from 35%
of needle insertions when all needle sizes, needle
types, injection techniques, and hair lengths were
combined (Fig. 3). Multivariate analysis was used
to determine the best combinations of needles, in-
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Selection of Needles
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Routine arthrocentesis in horses may result in tissue fragments or hair debris being inserted into the
joint. As needles pass through the skin they may
core tissues or cut hair and drag these fragments
into the joint. This complication is not uncommon
in humans or horses.7,9,12 The author has noted
these hair fragments during routine arthroscopic
procedures in horses (Fig. 2). Hair can act as a
foreign body, and tissue fragments from deep dermal tissues can contain bacteria from hair follicles,
sebaceous glands, and ducts. The author became
interested in the significance of tissue and hair contamination following arthroscopy in two horses with
nonresponding septic arthritis following joint injections in which long hair fragments were found in the
joints. These horses did not have previous injuries
or wounds, and the only mechanism for contamination with the hair was joint injection.
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Fig. 3. A clump of hair with some dermis was cored from the
skin by insertion of a 20-gauge sharp disposable needle inserted
perpendicular to the skin of a fetlock joint that had hair removed
with clippers (magnification 4⫻).
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HOW TO MAKE RATIONAL CHOICES FOR INTRA-ARTICULAR INJECTIONS
Table 1. Odds Ratios and P Values of Joint Contamination With Hair
After Needle Insertion Through Fetlock Joint Tissues
Odds Ratio
P Value
1.00
3.44
1.32
1.19
2.14
⬍0.001
0.15
0.38
0.003
1.00
2.44
1.69
⬍0.001
0.02
1.00
0.86
0.30
1.00
1.70
1.84
0.002
⬍0.001
1.00
1.48
4.83
0.21
1.21
0.103
⬍0.001
0.003
0.608
1.00
0.17
0.002
Study 1
Needle gauge and type
20
16
18
22
20 Spinal
Length of hair coat
Unclipped
Clipped
Shaved (razor)
Insertion speed
Fast
Slow
Times needle used
1
2
3
Study 2
Needle gauge and type
20
20 Spinal with stylet
20 Spinal no stylet
22 Spinal with stylet
22 Spinal no stylet
Angle of insertion
Straight (perpendicular)
Angled at 45°
From Wahl et al9 and Adams et al.12
T1
sertion techniques, and hair length to minimize tissue and hair contamination. There were
significant differences in some of the variables (Table 1). Although some differences occurred for contamination with both tissue debris and hair
fragments for each insertion technique, the presence
of hair debris was thought to be significant from a
Table 2.
Recommendations for Insertion of Needles Into Joints to
Minimize Contamination of Joints With Hair and Tissue Debris
(1) Reuse of needles, even once, should be avoided.
(2) Removal of hair with clippers or razor is not necessary
when sharp disposable needles are used and may increase
contamination with short hair fragments.
(3) Removal of hair from the skin is necessary when using 20gauge spinal needles to prevent insertion of long unclipped
hair into joints.
(4) Twenty-two–gauge spinal needles inserted with the stylet
in place markedly reduce tissue and hair contamination
compared with 20-gauge spinal needles.
(5) All spinal needles should be inserted with the stylet in
place.
(6) Angled insertion of needles through the skin (oblique to
surface of skin) reduces tissue and hair contamination.
(7) Tissue coring is common, and clearing the needle following
insertion into the joint by free flow or aspiration of
synovial fluid will clear the debris from the needle prior to
injection of medications.
clinical perspective because hair can elicit a foreign
body reaction.
The most striking finding from the first study,
other than the large percentage of injections that
resulted in tissue and hair contamination, was that
22 of 60 samples following joint puncture with the
20-gauge spinal needle through unclipped hair had
one or more long hairs pulled into the joint cavity
(Fig. 4). In the second study, no long hairs were
noted when 22-gauge spinal needles with the stylet
in place during insertion through unclipped hair
were tested. Angled insertion of needles at an angle of 45° to perpendicular significantly decreased
both tissue and hair contamination. Recommendations for needle usage during joint injection are
given in Table 2.
Conclusion
Septic arthritis following joint injection is uncommon, and large, prospective studies would be needed
in field conditions to determine if these recommendations will make a difference in the incidence of
septic arthritis. Joint infections probably will occur infrequently even under the best of conditions
and procedures. However, it is imperative that veterinarians use the best standards of practice because they are currently understood to minimize
risks of joint infections. Post-injection joint sepsis
can be difficult to treat, can lead to great expenses
for the owner, can cause permanent lameness or
death of affected horses, and can negatively influence owners’ respect for the veterinarian. It is best
to avoid all these problems when possible.
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Fig. 4. Twelve long hairs were pushed into the joint by 20-gauge
spinal needles with the stylet in place inserted 48 times through
unclipped hair. This suggests that contamination with long
hairs occurs in approximately 25% of joint injections with this
needle.
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References and Footnotes
1. Schneider RK, Bramlage LR, Moore RM, et al. A retrospective study of 192 horses affected with septic arthritis/tenosynovitis. Equine Vet J 1992;254:436 – 442.
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HOW TO MAKE RATIONAL CHOICES FOR INTRA-ARTICULAR INJECTIONS
2. LaPoint JM, Laverty S, Lavoie JP. Septic arthritis in 15
Standardbred racehorses after intra-articular injection. Equine Vet J 1992;24:430 – 434.
3. Ross MW. Orsini JA, Richardson DW, et al. Closed suction
drainage in the treatment of infectious arthritis of the equine
tarsocrural joint. Vet Surg 1991;20:21–29.
4. Geirsson AJ, Statkevicius S, Vikingsson A. Septic arthritis
in Iceland 1990 –2002: increasing incidence due to iatrogenic
infections. Ann Rheum Dis 2008;67:638 – 643.
5. Burstiner LC, Weese JS. Methicillin-resistant Staphylococcus aureus colonization in personnel attending a veterinary
surgery conference. Vet Surg 2010;39:150 –157.
6. Whyte W, Hilditch TE, Bell ND. Microbial contamination of
pharmaceutical injections at the site of administration. J Clin Hosp Pharm 1984;9:61– 67.
7. Glaser DL, Schildhorn JC, Bartolozzi AR, et al. The inadvertent introduction of skin into the joint during intra-articular knee injections: do you really know what is on the tip of
your needle? Proc Am Acad Orthop Surg 2001;68:130 –131.
8. Hague BA, Honnas CM, Simpson RB, et al. Evaluation of
skin bacterial flora before and after aseptic preparation of
clipped and nonclipped arthrocentesis sites in horses. Vet
Surg 1997;26:121–125.
9. Wahl K, Adams SB, Moore GE. Contamination of joint with
tissue debris and hair following arthrocentesis: the effect of
needle insertion angle, spinal needle gauge, and insertion of
spinal needles with and without the stylet using ante mortem
and postmortem joint preparations. Vet Surg 2012;41:391–
398.
10. Zubrod CJ, Farnsworth KD, Oaks L. Evaluation of arthrocentesis site bacterial flora before and after 4 methods of
preparation in horses with and without evidence of skin contamination. Vet Surg 2004;33:525–530.
11. Wilson DG, Hartmann VR, Carter A, et al. Comparison of
three preoperative skin preparation techniques in ponies. Equine Vet Ed 2011;23:4620465.
12. Adams SB, Moore GE, Mohammed Elrashidy, et al. Effect
of needle size and type, reuse of needles, insertion speed, and
removal of hair on contamination of joints with tissue debris
and hair after arthrocentesis. Vet Surg 2010;39:667– 673.
a
Hollendonner, K. Markleville, IN (personal communication,
2012).
b
DuraPrep Surgical Solution, 3M Healthcare, St. Paul, MN
55133.
c
Dyna-Hex 4. Xttrium Laboratories, Inc., Chicago, IL 60609.
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