artro

1. COPYRIGHT © SLACK INCORPORATED
■ Feature Article
abstract
A
rthroscopic procedures are as-
sociated with smaller incisions,
less structural damage, improved
intra-articular visualization, less pain in
the immediate postoperative period, and
potentially faster recovery.1
With any sur-
gery, exposure is critical. In arthroscopy,
maintaining adequate exposure through-
out the procedure requires an optical sys-
tem and good joint distension by a system
that delivers and maintains a clear medi-
um into the joint. Lack of adequate joint
distention is probably the most common
avoidable cause of poor visualization.2
As the image quality and effective-
ness of pump systems improve, arthros-
copy has become the primary treatment
modality to address various conditions
previously treated with open techniques.
Use of an Irrigation Pump System in
Arthroscopic Procedures
MARK S. HSIAO, MD; NICHOLAS KUSNEZOV, MD; RYAN N. SIEG, MD; BRETT D. OWENS, MD;
JOSHUA P. HERZOG, MD
The authors are from the Department of Or-
thopaedic Surgery and Rehabilitation (MSH, NK,
JPH), William Beaumont Army Medical Center, El
Paso, and the Department of Orthopaedic Surgery
and Rehabilitation (RNS), Carl R. Darnall Army
Medical Center, Fort Hood, Texas; and Brown
University Alpert Medical School (BDO), Provi-
dence, Rhode Island.
Drs Hsiao, Kusnezov, and Seig have no rele-
vant financial relationships to disclose. Dr Owens
is a paid consultant for Mitek and MTF/Conmed/
Linvatec. Dr Herzog is a paid consultant for Glo-
bus and Stryker.
The views expressed in this manuscript are
those of the authors and do not reflect the official
policy of the Department of the Army, Department
of Defense, or US Government. Drs Hsiao, Kus-
nezov, Sieg, and Herzog are employees of the US
Government. This work was prepared as part of
their official duties and as such, there is no copy-
right to be transferred.
Correspondence should be addressed to: Brett
D. Owens, MD, Brown University Alpert Medi-
cal School, 100 Butler Dr, Providence, RI 02906
(owensbrett@gmail.com).
Received: August 27, 2015; Accepted: Octo-
ber 19, 2015.
doi: 10.3928/01477447-20160427-01
Since its inception, arthroscopic surgery has become widely adopted among
orthopedic surgeons. It is therefore important to have an understanding of
the basic principles of arthroscopy. Compared with open techniques, ar-
throscopic procedures are associated with smaller incisions, less structural
damage, improved intra-articular visualization, less pain in the immediate
postoperative period, and faster recovery for patients. Pump systems used for
arthroscopic surgery have evolved over the years to provide improved intra-
operative visualization. Gravity flow systems were described first and are still
commonly used today. More recently, automated pump systems with pres-
sure or dual pressure and volume control have been developed. The advan-
tages of automated irrigation systems over gravity irrigation include a more
consistent flow, a greater degree of joint distention, improved visualization
especially with motorized instrumentation, decreased need for tourniquet
use, a tamponade effect on bleeding, and decreased operative time. Disad-
vantages include the need for additional equipment with increased cost and
maintenance, the initial learning curve for the surgical team, and increased
risk of extra-articular fluid dissection and associated complications such as
compartment syndrome. As image quality and pump systems improve, so
does the list of indications including diagnostic and treatment modalities to
address intra-articular pathology of the knee, shoulder, hip, wrist, elbow, and
ankle joints. This article reviews the current literature and presents the history
of arthroscopy, basic science of pressure and flow, types of irrigation pumps
and their functions, settings, applications, and complications. [Orthopedics.
2016; 39(3):e474-e478.]
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2. MAY/JUNE 2016
■ Feature Article
Over the years, the use of arthroscopy has
progressed to include the knee, shoulder,
hip, wrist, elbow, and ankle. Orthopedic
surgeons commonly perform arthroscopy
procedures, and it is important to under-
stand the equipment that is used.
HISTORY
The earliest reference for exploration
of body cavities using arthroscopy was
found in the ancient Hebrew literature.
More recently, in the 19th century, the
development of endoscopic devices was
spurred by the desire to explore the blad-
der.3
The first use in orthopedic surgery
occurred in 1918 when Dr Kenji Takagi
described endoscopy of a cadaver knee
joint using a Charrier number 22 cysto-
scope.4
He later modified his instrumenta-
tion to develop the first joint arthroscope.
Arthroscopy of the knee gained worldwide
attention in 1958 when it was introduced
at the Internal Society of Orthopaedic Sur-
gery and Traumatology conference. With
the advancement of arthroscopy, it quick-
ly became apparent synovial fluid was not
the preferred medium for visualization.
Saline rapidly became the standard to re-
place synovial fluid to enhance visualiza-
tion of key structures and pathology.5-7
Pump systems used for arthroscopic
surgery have evolved over the years to
provide improved visualization.8
Gravity
flow systems were used first and are still
commonly used, followed by automated
pump systems. Gravity flow systems
simply use gravity to control inflow by
positioning a bag of fluid higher than the
joint to provide enough pressure for insuf-
flation. The development and use of an
automated pump for arthroscopy began in
Sweden in the 1970s. Currently, there are
2 basic types of automated pump systems.
The first type is a pressure-control pump,
which controls pressure via inflow only.
More recent automated pump systems
maintain pressure by controlling inflow
and outflow independently, thus termed
pressure and flow control pumps or dual
systems.
BASIC SCIENCE
Pressure
Forty years ago, little was known re-
garding intra-articular pressure during
arthroscopy. Questions regarding minimal
pressure required for good visualization,
pressure necessary to rupture the synovi-
um, pressure changes caused by position-
ing, and even average pressures attained
by the gravity flow method remained un-
answered.
In 1977, Gillquist et al9
first reported
that a threshold pressure of 28 mm Hg
was necessary for good visualization
during arthroscopy of the knee. Ewing
et al10
corroborated this finding in 1986
and reported that 30 mm Hg was the aver-
age threshold pressure required to cause
tamponade of small intra-articular ves-
sels. They also stated that a pressure of 70
mm Hg was necessary for consistent and
sustained capsular distention.
In 1986, Bergstrom and Gillquist11
performed a study on 45 knee arthrosco-
pies using a mechanical pump with open
outflow and flow rates of 45 cc per minute.
They reported good visualization for all of
the procedures with intra-articular pres-
sures ranging between 40 and 60 mm Hg
and noted that pressure never rose above
60 mm Hg. In 1992, Arangio and Kostel-
nik12
investigated the minimum adequate
pressure required for arthroscopic proce-
dures of the knee. Their results showed
that with an average pressure of 55
mm Hg, arthroscopy could be performed
in all knee positions studied and that pres-
sure required for adequate joint distention
ranged from 30 to 60 mm Hg.13
As technology advances, the pressure
gradient of an inflow system produced by
an automated pump is totally controlled
by the pump and is not dependent on the
fluid reservoir height, volume, or gravity.
Automated pumps have the capability of
producing predictable continuous flow
rates with an open system. In addition,
they are able to generate intra-articular
pressures that exceed those possible with
gravity inflow systems. Advocates of the
pump system believe they generate better
visualization and clearing of joint debris
during arthroscopy.10,11,14
Flow
Flow through a tube follows Poi-
seuille’s law:
Flow=(Pressure gradient)/(Resistance
to flow).
A gravity-fed system is related to the
height difference between the fluid res-
ervoir and the joint (ie, raising the inflow
bag and not the amount of fluid in the
bag). Also, with a gravity system in which
outflow is closed, flow will occur until
the joint is distended to an intra-articular
pressure equal to the inflow pressure gra-
dient, at which time, flow will cease.
Regardless of whether inflow comes
from a gravity or pump system, intra-
articular flow requires that fluid must come
into and out of the joint at 2 separate points
(inflow-outflow system). The primary
need for fluid flow is to clear the joint of
cloudy fluid caused by blood or debris to
allow improved visualization. When good
visualization is achieved, there is no need
for continuous flow. If flow rates become
exceedingly high, turbulence is created,
which can interfere with visualization.
Conversely, there are times when flow may
be a hindrance, such as during loose body
removal or when performing microfracture
and checking for backbleeding.
If the rate of fluid outflow exceeds the
capacity of the inflow system, a negative
fluid balance exists, which leads to loss
of joint distention and loss of visibility.
This situation commonly occurs with
outflow through a motorized suction
shaver where outflow occurs by a nega-
tive pressure suction line attached to the
shaver. Use of a mechanical pump in this
setting can increase flow rates propor-
tional to the outflow to a point where a
fluid balance exists, thus avoiding loss of
joint distention. With a gravity-fed sys-
tem, this problem may be circumvented
by intermittently clamping the suction
line to the shaver, thus giving inflow time
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3. COPYRIGHT © SLACK INCORPORATED
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to catch up with the negative fluid bal-
ance.
The 2 most common access routes
for inflow during knee arthroscopy are
through the sheath that houses the ar-
throscope or through a separate cannula,
usually placed in the suprapatellar pouch.
Many surgeons prefer to lead inflow
through the arthroscope, despite high re-
sistance created at the inflow spigot and
the water canal between the arthroscope
and the sheath that encases it.15,16
Inflow
through the arthroscope is advantageous
for a number of reasons. Inflow through
the suprapatellar route frequently is im-
peded by knee flexion and the “figure of
four” position, leading to poor visualiza-
tion. In addition, suprapatellar portal inci-
sions can be painful and slow to heal.
Furthermore, in arthroscopy of other
joints (eg, wrist, elbow, ankle, hip), the
number of possible access portals is lim-
ited. Thus, inflow on the scope obviates
using one of few portals for inflow, giving
the surgeon increased flexibility for op-
erative instrument placement. With inflow
from the arthroscope, fluid entering the
joint cleanses the area that coincides with
the surgeon’s field of view.
COMPONENTS OF AN IRRIGATION
SYSTEM
There are 5 basic components to creat-
ing an irrigation system for joint arthros-
copy: (1) saline bag; (2) inflow tubing; (3)
a pressure gradient supplied from gravity
or an automated pump; (4) intra-articular
joint space; and (5) outflow tubing with or
without pressure-sensing feedback to an
automated pump.
One of the advantages of a gravity flow
system is the ease of setup and mainte-
nance. Saline bags are simply attached to
an intravenous (IV) pole a few feet above
the level of the joint being operated on,
then one end of the sterile inflow tubing is
attached to the bags and the other end is at-
tached to the arthroscopy instrumentation.
To change the amount of inflow/pressure
during the case, an operating room nurse
will need to raise or lower the height of the
IV pole. If outflow is necessary for better
visualization, then another portal can be
created with a stopcock instrument, which
allows the amount of outflow desired to be
adjusted manually. The surgeon may attach
outflow tubing to the stopcock so that it
drains into a catch basin or bag.
When using an automated pump sys-
tem, the setup will depend on the type and
brand of pump used. The basic concepts
are inherently the same for each system,
with a few differences. Multiple commer-
cial irrigation pump systems are available.
The system components include transpar-
ent safety covers, irrigation roller pump,
tension rocker arm, power pad, display,
and adjustment. First, the saline bags are
attached to an IV pole the same as for the
gravity system. However, the height of the
IV pole is irrelevant. One end of the sterile
inflow tubing is attached to the arthroscopy
instrumentation, then the middle of the tub-
ing is attached around the roller pump, and
the other end is attached to the saline bags.
Outflow with a pressure control pump is set
up in the same manner as for a gravity sys-
tem. If a pressure and flow control pump is
used, the sterile outflow tubing is attached
through the roller pump designated for
outflow. The Table provides industry ex-
amples of pressure levels with and without
tourniquet in various joints.
Automated pump systems have an
impeller pump power by an electronic
controller. Solution flows from the bags
through the tubes around the roller pump
and through the pressure chamber, where
the pressure is read by a built-in pressure
transducer. The controller determines the
speed of the impeller pump, which drives
the flow of irrigant and determines the re-
sultant static pressure.
The dual system functions similarly
to the pressure control pump, except that
it also has a separate outflow roller con-
nected by tubing back to the pump that
allows for outflow control. Solution flows
from the outflow tubing around the roller,
through a separate chamber where pres-
sure is measured. Computer-integrated in-
flow and outflow control helps to maintain
constant pressure in the joint. The device
also has the capability to increase pressure
and flow independently to eliminate debris
and control bleeding. It interfaces directly
with the shaver to automatically control
shaver suction, and thus no wall suction or
manual adjustments are necessary.
For automated systems, the surgeon
then will have to ensure that the settings
are correct. The inflow pressure is set for
the pressure control pump, and both the
inflow and outflow pressures are set for
the dual system. There may be a foot ped-
al control with the automated systems that
allows for transient increases in pressure
and flow to improve visualization.
DISCUSSION
The effectiveness of an arthroscopic
pump system is based on the visualization
Table
Pressure Level With and Without Tourniquet in Various Joints
Pressure Level, mm Hg
Joint With Tourniquet Without Tourniquet
Shoulder - 50-60
Acromioplasty - 50-60
Knee joint 30-35 65
Wrist 30-40 65
Elbow, ankle 30-40 65
Hip 40-45 65
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4. MAY/JUNE 2016
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afforded to the surgeon during the proce-
dure while maintaining patient safety. Vi-
sualization stems from a combination of
camera image quality and maintaining a
clear fluid medium. The irrigation system
controls the fluid medium environment by
regulating fluid volume used via inflow
and outflow and the intra-articular vs set
pressure. Patient safety relies on maintain-
ing low intra-articular pressures and low
levels of fluid extravasation.17
The advantages to using a gravity flow
system are the ease of setup and main-
tenance as well as a low complication
profile since the pressure rarely reaches
dangerous levels. Gravity flow systems
have been used in Sweden for approxi-
mately 14 years without significant com-
plications.9,11
The drawback associated
with using a gravity-fed system is that it
requires manual adjustments throughout
the case to change the amount of inflow
and outflow necessary for good visualiza-
tion. This can be troublesome for long
cases, especially if the tourniquet cannot
be used.
Ewing et al10
stated that an ideal au-
tomated pump should deliver necessary
flow rates, keep the intra-articular pres-
sure at adequate levels for visualization,
and include safety features such as pres-
sure monitors that sound a warning when
the pressure is too high. Use of these
pumps set to deliver a constant intra-
articular pressure slightly above end cap-
illary diastolic filling pressure should al-
low one to perform arthroscopic surgery
in a clear field of view without the use of
a tourniquet. When an automated pump
meets all of these criteria, then this prod-
uct would offer many advantages over the
gravity-flow methods.10
More recently, evidence suggests that
dual systems provide better visualiza-
tion than pressure-control systems, which
may lead to decreased operative times.
Ogilvie-Harris and Weisleder18
prospec-
tively compared pressure-controlled
pumps vs pressure and flow control
pumps for multiple types of arthroscopic
procedures. Visualization and technical
ease were assessed subjectively via obser-
vations of the video monitor and given a
score based on the amount of impairment
of visualization. They concluded that the
adequacy of visualization and technical
ease significantly improved with the pres-
sure and flow control system compared
with the pressure system alone. They also
compared surgical times for the 2 pumps
based on the duration of the surgery. They
reported an increased number of surger-
ies less than 1 hour using the pressure and
flow control units and concluded that the
increased number of shorter duration sur-
geries was due to improved visualization.
Ampat et al19
prospectively compared
these 2 types of pump systems (Aquaflo2
pump vs Fluid Management System [FMS;
DePuy, Mitek, Raynham, Massachusetts])
for shoulder arthroscopic surgery based on
visual clarity, presence of bleeding vessels,
and total red blood cell loss for subacromial
decompressions of 20 shoulders. The sur-
geon assessed the visual clarity and pres-
ence of bleeding vessels subjectively. Total
red blood cell loss was determined by mul-
tiplying the volume of fluid that was used
and the cell count in the effluent. There
were no significant differences in relation
to visual clarity, presence of bleeding, or
red blood cell loss, and they concluded that
there was no difference between the pumps
in straightforward shoulder procedures.
The studies by Ogilvie-Harris and
Weisleder18
and Ampat et al19
compared
visualization based on subjective mea-
sures, and neither study set out to mea-
sure the amount of operative time saving.
Tuijthof et al17
compared a gravity pump
with a pressure and flow control pump us-
ing objective data and demonstrated time
saving for the latter system.
Sieg et al20
sought to perform a direct
comparison in terms of operative times
in anterior cruciate ligament (ACL) re-
constructive surgery using these 2 auto-
mated pumps. This retrospective study
evaluated all ACL reconstructive sur-
geries performed by 3 surgeons dur-
ing an 8-month period. During the first
4 months, a pressure-driven pump was
used, and during the second 4 months, a
pressure and flow control pump was used.
Fifty-eight ACL reconstructions were per-
formed; 21 procedures were performed
using the pressure-control system, and
23 procedures were performed using the
dual system. Average operative time using
the pressure-control pump was 126 min-
utes vs 111 minutes for the dual system.
There was an average 15-minute decrease
in surgical time (P=.04) in favor of the
dual system. The authors concluded this
was likely due to the improved visualiza-
tion provided by the independent control
of pressure and flow.
COMPLICATIONS
Automated pressure-sensitive pumps
monitor intra-articular pressure and au-
tomatically shut down if preset pressure
levels are not maintained. In normal op-
eration, they automatically maintain flow
and pressure independent of one another
to maintain joint distention and improve
irrigation.13
However, if the pressure sen-
sor fails, automated pumps may not shut
down, and intra-articular pressures can
rise to dangerous levels.
High intra-articular pressures may
pose a risk to fluid extravasation, com-
partment syndrome, and synovial pouch
rupture. Studies have reported synovial
pouch rupture when intra-articular pres-
sure rises in the range of 120 to 150
mm Hg.21,22
Despite known possible com-
plications related to high pressure, many
commercial devices allow pressure values
far above 100 mm Hg.8
Complications rate of 1% have been
described in the literature, with complica-
tions including fluid extravasation (intra-
peritoneal and extraperitoneal accumula-
tion), synovial pouch rupture (distension
of compartments of the leg and thigh),
and compartment syndrome.13
There are
reported cases for termination of knee ar-
throscopy due to distention of the anterior
and posterior compartment of the leg and
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thigh, and compartment syndrome with no
palpable pulses of posterior tibial or dor-
salis pedis arteries requiring fasciotomies.
Noyes and Spievack23
reported excessive
fluid extravasation in 4 of 300 cases dur-
ing a 9-month period. Other complica-
tions that have been reported include mas-
sive intraperitoneal and extraperitoneal
accumulation of irrigation fluid during hip
arthroscopy and compartment syndrome
after knee arthroscopy for examination of
a tibia plateau fracture.24,25
CONCLUSION
Advantages of mechanical fluid ir-
rigation system over gravity irrigation
are: consistent flow; greater degree of
joint distention; improved visualization,
especially when motorized operative in-
struments are used; decreased need for
tourniquet use; a tamponade effect on
bleeding; and decreased operative time.13
Disadvantages include the need for ad-
ditional equipment with increased cost
and maintenance, initial learning curve
for the surgical team, and extra-articular
fluid dissection.23,26
Although significant
advances have been made in arthroscopic
equipment, few investigations exist that
compare different pump systems. Even
though improvements in visualization
have been noted with dual systems, more
research is necessary to determine the
clinical significance.
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