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Techniques in Orthopaedics®
19(4):327–336 © 2004 Lippincott Williams & Wilkins, Inc., Philadelphia
Use of Vena Cava Filters
Leoncio L. Kaw, Jr.,
M.D.
and Ralph B. Dilley,
M.D., F.A.C.S.
Summary: Venous thromboembolism remains a significant cause of morbidity and
mortality in the United States. Although anticoagulation is considered the mainstay of
treatment, placement of vena cava filters is generally indicated in circumstances when
there is a contraindication, complication, or documented failure of anticoagulation
therapy. A number of devices are available and approved by the U.S. Food and Drug
Administration for use. Each of these devices has distinct designs and deployment
mechanisms and, more importantly, have variable data on safety and effectiveness. It
is paramount for physicians to be familiar with the specific features of each device.
This article addresses the indications, techniques of deployment, and complications
associated with vena cava filters. Unique features and comparison data of each
available device is presented. Key Words: Vena cava filters—Deep vein thrombosis—
Pulmonary embolism.
Venous thromboembolism (VTE) continues to be a
significant cause of morbidity and mortality in the
United States. It is projected that at least 201,000 new
cases of VTE occur annually.63 Pulmonary embolism
(PE) is the most severe complication of VTE. The
estimated case fatality rate of PE is 7.7 deaths per 100
patients diagnosed with the condition.65 According to the
National Center for Health Statistics, PE was the underlying or contributing cause of death in 572,773 decedents
during a 20-year period (1979 –1998).33
Anticoagulation is currently the standard treatment for
acute PE; however, approximately 3.9% to 7.9% of
patients who receive therapeutic anticoagulation have
been shown to experience a recurrence.4,16,21 Furthermore, bleeding complications occur in up to 10.5% of
patients.4,21 In these instances, interruption of the inferior
vena cava (IVC) has emerged as an effective alternative
for the prevention of PE.
This article provides an overview of currently available
vena caval filters (VCF) approved by the U.S. Food and
Drug Administration (FDA). Techniques of deployment,
results of studies on VCF, and complications associated
with insertion and use are addressed. In addition, established and controversial indications are discussed.
HISTORICAL BACKGROUND
Lower extremity deep venous thrombosis (DVT) as a
source of pulmonary emboli was established by John
Homans in the 1930s when he demonstrated during
autopsy that the end of a thrombus taken from the
pulmonary artery matched with the residual clot in the
popliteal vein.32 Interruption of venous outflow by femoral, iliac, or IVC ligation was then performed in patients
with lower extremity venous thrombi to prevent PE.31,51
Unfortunately, these methods were frequently associated
with significant operative mortality, a high rate of recurrent PE, and the disabling sequelae of chronic venous
stasis.3,28,49 A different approach to venous interruption
was to allow some blood flow and still prevent passage
of large emboli to the lungs by partial occlusion of the
IVC. Various techniques such as caval plication with
sutures or staples and use of ingenious extravascular
occlusive devices were reported by numerous authors.1,44,48,64 Although the recurrent PE rate was considerably reduced with these approaches, operative mortality and long-term complications from venous stasis
remained significant.48 Consequently, the need for a
procedure or device that allowed effective filtration of
emboli while maintaining IVC patency, and which could
From the Division of Cardiothoracic and Vascular Surgery, Scripps
Clinic and Scripps Green Hospital, La Jolla, California.
Address correspondence and reprint requests to Ralph B. Dilley,
MD, FACS, Division of Cardiothoracic and Vascular Surgery, Scripps
Clinic/Scripps Green Hospital, 10666 N. Torrey Pines Road, La Jolla,
CA 92037. E-mail: rdilley@scrippsclinic.com
327
328
L. L. KAW AND R. B. DILLEY
TABLE 1. Specifications of Current FDA-Approved Vena Cava Filters
Device
Simon Nitinol
(Bard, Covington, GA)
Vena Tech LP
(B. Braun, Evanston, IL)
Vena Tech LGM
(B. Braun, Evanston, IL)
Stainless steel Greenfield
(Boston Scientific,
Watertown, MA)
Titanium Greenfield
(Boston Scientific,
Watertown, MA)
Gianturco-Roehm Bird’s Nest
(Cook, Bloomington, IN)
TrapEase
(Cordis Endovascular,
Warren, NJ)
Recovery
(Bard, Covington, GA)
Günther Tulip
(Cook, Bloomington, IN)
OptEase
(Cordis Endovascular,
Warren, NJ)
Sheath Size
(ID/OD)
Length
(mm)
Diameter
(mm)
Jugular/Femoral/
antecubital
Jugular/femoral
7/9 F
38
28
Permanent
7/9 F
43
40
Permanent
Conical
Jugular/femoral
12/14 F
38
30
Permanent
316 L stainless
steel
Conical
Jugular/femoral
12/14 F
49
32
Permanent
Titanium
Conical
Jugular/femoral
12/14 F
47
38
Permanent
Stainless steel
Multiplane
Jugular/femoral
12/14 F
variable
40
Permanent
Nitinol
Double basket
Jugular/femoral/
antecubital
6/8 F
50
35
Permanent
Nitinol
Femoral
7/9 F
40
32
Permanent/retrievable
Conichrome
Bilevel,
conical
Conical
Jugular/femoral
8.5/10 F
45
30
Permanent/retrievable
Nitinol
Double basket
Jugular/femoral/
antecubital
6/8 F
58
30
Permanent/retrievable
Material
Design
Access
Phynox
Bilevel, domeconical
Conical
Phynox
Nitinol
Intended
Use
ID/OD ⫽ inner/outer diameter.
be performed under local anesthesia to minimize operative risk, became obvious. Initial efforts in the late 1960s
included the Eichelter catheter,71 which was a removable
device, and the Hunter balloon,34 designed for permanent
occlusion of the vena cava. The most popular device was
the Mobin-Uddin umbrella, which was introduced in
1967.47 This device was an umbrella design and consisted of 6 metallic spokes radiating from a central hub.
It was covered on both sides by a circular sheet of
heparin-impregnated silastic membrane with 1.5-mm
perforations to allow continuous blood flow. The umbrella was inserted through a venotomy performed under
local anesthesia and fluoroscopic guidance with the apex
pointing inferiorly. In their first report on the clinical
application of this device, no recurrence of PE was noted
at 8 to 10 months follow up.46 However, thrombotic
occlusion of the IVC was observed in all instances.
The development of the Greenfield filter represented a
major improvement over the Mobin-Uddin umbrella.
The filter was made of 6 stainless steel strands fitted at an
angle of 35° to an apical hub. Fixation was provided by
fine recurved hooks, which grasp the vena caval wall
without penetrating it. The unique conical-shaped design
of the Greenfield filter had the advantage of allowing
trapped emboli to fill and occlude 70% of the length of
the cone without reducing the cross-sectional area more
than 50%, thereby allowing continued blood flow.24 As a
Techniques in Orthopaedics®, Vol. 19, No. 4, 2004
result, a much lower rate of caval occlusion was observed when compared with prior methods of clot filtration. Initial animal and clinical studies on the Greenfield
filter showed maintenance of caval patency in all subjects during the period of observation.24,25 Like the Mobin-Uddin umbrella, the Greenfield filter was inserted
through a venotomy using a 28 French introducer sheath.
Over the next 30 years, several versions of IVC filters
have been developed and marketed. IVC filter insertion
has evolved from an open to a percutaneous procedure,
with introducer sheaths as small as 8 French. In addition,
retrievable filters are now available for patients requiring
temporary protection from thromboembolic events. Although these filters share many similarities in design and
deployment mechanisms, familiarity with their specific
characteristics and features is mandatory for their safe
and appropriate use.
DESCRIPTION OF AVAILABLE DEVICES
Currently, there are 7 permanent and 3 retrievable IVC
filters approved by the FDA. Table 1 summarizes the
physical characteristics and specifications of each.
Simon Nitinol Filter
The Simon Nitinol filter is constructed from a nickel–
titanium alloy that has unique thermal–mechanical prop-
USE OF VENA CAVA FILTERS
329
FIG. 1. Four of 6 FDA-approved permanent vena cava
filters. From left, Bird’s Nest,
stainless steel Greenfield,
TrapEase, and Simon Nitinol
filters.
erties. The filter is pliable at room temperature and
reforms into its predetermined shape when warmed to
body temperature. This flexibility, along with its small
delivery system, allows placement through alternative
sites such as the antecubital or left jugular veins.
The filter design consists of a dome of 7 overlapping
wires below which 6 struts with hooks at the base
diverge to form a cone (Fig. 1). This configuration, in
effect, provides 2 levels of filtration. The insertion procedure requires iced normal saline to be continually infused
through the delivery system. The filter is advanced rapidly
by a feeder pump and subsequently discharged from the
storage catheter. Once in the IVC, the filter then configures
to its predetermined shape. The dome of the filter permits
itself to align with the IVC on deployment.
Vena Tech LGM and LP Filters
The Vena Tech LGM filter is fabricated from Phynox,
a nonferromagnetic alloy with excellent magnetic resonance imaging (MRI) compatibility. It has a conical
configuration with 6 stabilizing sidebars on each limb
designed to center and maintain orientation of the filter
on deployment. These sidebars each contain anchoring
barbs, some oriented superiorly and others inferiorly.
The filter comes in a single kit that can be used for either
the femoral or jugular approach. A guidewire is used to
position the sheath into the IVC. The filter is then
advanced through the entire length of the sheath and
released by quick withdrawal of the sheath.
The Vena Tech LP filter is a more recent, low-profile
version that has 8 Phynox wires forming the conical
configuration instead of 6.
Greenfield Filter
The original Greenfield filter is no longer commercially available and has since been replaced by 2 varieties: the over-the-wire stainless steel and modified-hook
titanium filters (Fig. 1). Both share the similar conical
design of the original filter but differ in that the stainless
steel version can be placed over a guidewire. In addition,
the stainless steel filter has a more flexible carrier system,
which allows insertion through a left femoral approach.
The initial design of the titanium filter was made with
hooks similar to the original Greenfield filter. This,
however, was noted to have a tendency to migrate, tilt,
and perforate the IVC. Subsequent modifications resulted in a recurved hook design with an 80° angulation.
The recurved hook serves as a barrier to penetration
beyond the axis of the filter limb, and the 80° hook limits
both upward and downward force vectors that may induce migration.23
The Greenfield filter has one of the simplest deployment mechanisms among the currently available filters.
An intravascular sheath is inserted through which the
Techniques in Orthopaedics®, Vol. 19, No. 4, 2004
330
L. L. KAW AND R. B. DILLEY
FIG. 2. The OptEase (left)
and Gunther Tulip (right) retrievable filters.
carrier system is advanced to the desired level of placement. The locking mechanism on the control handle is
then released and the carrier gradually retracted until the
filter springs open in the vena cava. Separate color-coded
kits are available for jugular and femoral approaches.
Bird’s Nest Filter
The Gianturco-Roehm Bird’s Nest filter uses a fine
wire, multiplane filtering system consisting of 4 stainless
steel wires, each 25 cm in length and 0.18 mm in
diameter, attached to 2 pairs of V-shaped struts (Fig. 1).
The tips of each strut have hooks designed to engage the
caval wall for fixation. During insertion, a pusher is used
to position the first set of hooks into the IVC. The 4 wires
are then extruded from the filter catheter through a series
of controlled steps, which allows the operator to alter
placement and accommodate anatomic variations. The
advantage of this is the avoidance of the need to center
the filter in the caval lumen and the flexibility to be
placed into vena cavae up to 40 mm in diameter (all other
filters are limited to cavae of 30 mm or less). On the
other hand, optimal deployment requires approximately
7 cm in caval length and therefore is not useful in
patients with short vena cavae. The Bird’s Nest filter
generates the largest MRI artifact because of its stainless
steel construction.
Techniques in Orthopaedics®, Vol. 19, No. 4, 2004
TrapEase and OptEase Filters
The TrapEase filter has a symmetric, double-basket
design that is laser cut from a single tube of nitinol (Fig.
1). The proximal and distal baskets each consist of 6
diamond-shaped struts oriented opposite to each other
and connected by 6 straight side struts. The side struts
contain proximal and distal hooks for fixation within the
IVC. This unique configuration essentially provides 2
levels of filtering and allows a single filter to be placed
from either direction. Moreover, the filter comes with the
lowest profile delivery system available on the market
and therefore can be inserted by bilateral femoral, jugular, or antecubital approaches. The filter is self-centering
and is deployed by simply extruding it from the sheath.
The OptEase filter is a retrievable version of the
TrapEase and shares its basic design and deployment
system. Unlike the TrapEase, the hooks on the side struts
of the OptEase are located only on its proximal aspect
and are longitudinally oriented (Fig. 2). The OptEase
also has a hook on its inferior aspect for retrieval using
a loop snare through a femoral approach. Proper orientation during insertion is therefore mandatory.
Recovery Filter
The Recovery filter has a unique conical design composed of 12 nitinol wires extending from a nitinol sleeve.
The filter has 6 arms and 6 legs, which provide 2 levels
USE OF VENA CAVA FILTERS
of filtration. Insertion is through either femoral vein, and
deployment is similar to the technique used for the
Simon Nitinol filter.
Filter removal is performed with a retrieval cone,
constructed with 9 metal claws covered by a urethane
cover, and inserted through the jugular vein. The retrieval cone is then advanced through a 10 French sheath
and docked with the filter tip so that the filter may be
retracted into the sheath and removed.
Günther Tulip Filter
The Günther Tulip filter is made of an alloy consisting
of cobalt, nickel, chromium, and other trace metals
(commonly called conichrome). It has a conical design
with 4 main struts and 4 secondary struts (Fig. 2). The
secondary struts loop around three fourths of the length
of main struts forming a shape that resembles the petals
of a tulip, hence its name. The primary struts have barbs
on their distal end to provide secure attachment to the
caval wall. The top of the filter has a small hook for
insertion and retrieval through a jugular approach.
The filter can be placed through femoral or jugular
routes, with separate kits available for each. The femoral
filter comes preloaded, whereas the jugular filter has to
be loaded into the introducer before the procedure. Like
with most filters, manual unsheathing is required for
deployment. When inserted through the jugular approach, the filter can be repositioned even after deployment simply by pushing the sheath over the filter to
collapse it. The whole system can then be moved to the
desired position and redeployed by withdrawing the
sheath again. Retrieval is through the jugular approach
using an 80-cm loop snare made of braided platinum.
TECHNIQUES IN FILTER PLACEMENT
Access to the IVC for filter placement is generally
obtained through the right femoral or jugular approach
using the modified Seldinger technique. The choice of
insertion site is arbitrary and normally depends on anatomy, location of the thrombus, type of filter available,
and operator preference. Depending on the clinical condition of the patient, VCF insertion can be performed
safely in the operating room, angiography suite, or at the
bedside, and as an outpatient or inpatient procedure.
Whatever the approach, evaluation of the IVC is mandatory before filter placement. The length and diameter
of the infrarenal IVC should be measured, the location
and number of renal veins determined, the presence and
location of the thrombus ascertained, and the existence of
anatomic variations such as circumaortic renal vein or
duplication of the IVC must be defined. Inadequate
331
imaging has been shown to be a major factor for operator
errors during percutaneous VCF placements.37 A retrospective review by Savin et al.59 demonstrated significantly increased filter misplacement rate when placement was not preceded by cavography (43% vs. 2.5%,
P ⬍ 0.0001). One patient whose filter was misplaced in
the iliac vein developed PE from an existing DVT in the
contralateral limb.
Inadequate imaging can also lead to errors in filter
selection. Placement of a filter too small for the caval
diameter, for instance, can lead to filter migration and
embolism. Currently, only the Bird’s Nest filter is approved for use in an IVC of more than 30 mm in
diameter. In patients with megacava, therefore, a Bird’s
Nest filter should be used (as long as the IVC diameter
does not exceed 40 mm), or 2 filters should be deployed,
1 in each common iliac vein.9
The preferred method of imaging is contrast cavography. Iodinated contrast agents, carbon dioxide, or gadolinium may be used depending on the patient’s renal
function, comorbidity, prior contrast load, and/or the
need for further contrast imaging. Although not routine
in our practice, some authors advocate selective venography before VCF placement.13,30 In their experience,
selective venography depicted aberrant findings not seen
with standard cavography in 23% to 26% of patients. A
significant number of these patients required alterations
in placement or selection of the VCF.
Duplex and intravascular ultrasound (IVUS) are alternative imaging modalities and have been shown to be
effective and safe.10,12,17,69 These can be done at the
bedside and are particularly advantageous in the multiply
injured or critically ill patient when transport to the
operating room or angiography suite can be complex and
potentially hazardous. Secondary benefits include costeffectiveness and avoidance of contrast agent use. With
duplex ultrasound, visualization of the IVC–right renal
vein junction is performed first and used as the anatomic
reference for VCF placement. Diameter measurements of
the IVC in 2 dimensions and assessment of the patency
of the proposed cannulation site are then determined. The
femoral approach is chosen preferentially for logistic
reasons because preparation of a sterile field cephalad to
the bed as needed for jugular access may be extremely
inconvenient. Once the filter is positioned in the proper
location, deployment with duplex ultrasound guidance is
accomplished. Postprocedure plain abdominal radiographs are obtained selectively to confirm filter position.
Adequate duplex imaging of the vena cava before filter
placement is possible in up to 98.5% of nontrauma
patients18 and 90% to 92% of patients with multiorgan
trauma.10,12 If the duplex scan imaging results are inadTechniques in Orthopaedics®, Vol. 19, No. 4, 2004
332
L. L. KAW AND R. B. DILLEY
equate, then fluoroscopic or IVUS-directed filter placement should be carried out.
The ability of IVUS to delineate relevant arterial and
venous anatomy with excellent sensitivity and specificity
is well known. Using selective venography as the “gold
standard,” Ashley et al.6 compared the accuracy of the
anatomic information obtained by both IVUS and contrast venography for VCF placement in trauma patients.
In this study, IVUS was observed to be significantly
more accurate in localizing the renal veins and measuring IVC diameter than contrast venography; however,
the disadvantage of using IVUS for VCF placement is
that actual filter deployment is done blindly. IVUS is
used to define the anatomy and identify the VCF landing
zone, which is marked on the patient. The IVUS catheter
is then removed and exchanged for the VCF catheter,
which is subsequently deployed. In recognition of this
limitation, Wellons et al.69 described an innovative technique in which continuous real-time ultrasonography is
performed to ensure precise filter deployment. Two
punctures 1 cm apart are made on the femoral vein, 1 for
the IVUS and another for the IVC filter sheath. Ninetyfour percent of their patients underwent successful VCF
placement. With this technique, the authors emphasized
the use of IVC filters with low-profile introduction systems (TrapEase and Simon Nitinol) to minimize complications brought about by 2 venipunctures.
Following device deployment, the sheath is removed
and gentle manual compression is applied for 3 to 5
minutes. Prolonged, aggressive compression is discouraged
as a result of significant incidence of insertion site thrombosis. In patients in whom the jugular approach is used, the
head of the bed is elevated up to 60° before sheath removal
to reduce venous pressure and facilitate hemostasis.
We do not routinely anticoagulate patients after VCF
placement. Patient factors, however, must be taken into
consideration in the decision-making. Although VCFs
prevent PE, they have no effect on the prevention and
treatment of DVT, and they cannot prevent an extension,
recurrence, or the sequelae of postthrombotic syndrome.
There is some evidence that anticoagulants lessen the
complication of postthrombotic syndrome.
INDICATIONS FOR USE
Anticoagulation remains the cornerstone for treatment
of acute VTE, but in patients with absolute contraindications to or documented failures of anticoagulation
therapy, insertion of a VCF is generally indicated. With
improved ease of percutaneous insertion provided by
reduced and more flexible delivery systems, and the
reportedly low complication rates associated with their
Techniques in Orthopaedics®, Vol. 19, No. 4, 2004
TABLE 2. Indications and Contraindications for Vena
Cava Filter Placement
Absolute indications
DVT/PE with failure of anticoagulation
DVT/PE with complications from anticoagulation
DVT/PE with contraindication to anticoagulation (severe
gastrointestinal bleeding, intracerebral and retroperitoneal
hemorrhage, need for major surgery)
Relative indications
DVT/PE with pulmonary hypertension and cor pulmonale
Free-floating iliofemoral or IVC thrombus
Prophylaxis for high-risk trauma and surgical patients
DVT/PE in patients with cancer
Recurrent PE with IVC filter in place
History of DVT in patients for hip/knee replacement and gastric
bypass surgery
Contraindications
Chronically thrombosed IVC
No access route to place filter
DVT ⫽ deep vein thrombosis; PE ⫽ pulmonary embolus; IVC ⫽
inferior vena cava.
use, an expansion of the traditional indications for VCF
placement has been observed. In a large populationbased study in the state of California, White et al.70 noted
that most patients with VTE treated with an IVC filter
had neither of the 2 widely accepted indications for filter
use. Indeed, an increasing number of patients are having
IVC filters inserted for prophylaxis, broadly interpreted
to include patients with or without documented DVT or
PE and those in whom the filter was used as an adjunct
to anticoagulation. Data from the Michigan Filter Registry revealed that 46% of filters placed in 1999 were for
prophylaxis, a dramatic increase from 14% as of 1988.26
Unfortunately, there is little level I data to support these
expanded indications. Girard et al.20 reviewed the literature on VCFs published between 1975 and 2000 and
concluded that the evidence for the need of VCF placement is weak. Of the 568 references analyzed, only 1 was
a randomized, controlled trial, and the few large prospective series were so heterogenous as to preclude relevant
comparison and analysis. Nonetheless, guidelines and
reporting standards have been formulated for IVC filter
insertion.22,27 Strict adherence to these guidelines is important for institutional quality assurance programs and
provides physicians the necessary foundation to develop
a practical approach to decision-making. Table 2 lists the
current indications for IVC filter placement modified
from these guidelines. Relatively controversial indications are discussed subsequently.
Free-Floating Thrombus
Identification of free-floating thrombus (FFT) is often
considered an indication for VCF placement based on the
reported incidence of PE as high as 60%50; however, the
available data are conflicting and inconclusive. A recent
USE OF VENA CAVA FILTERS
prospective, nonrandomized study reported no higher
risk for PE from FFT compared with occlusive thrombus
when treated with standard anticoagulation.53 Baldridge
et al.8 evaluated the fate of FFT using duplex ultrasound
and noted that up to 87% do not embolize but rather
become adherent to the vein wall, decrease in size, or
resolve. We agree with most authors that anticoagulation
should be initiated first and VCF placement be reserved
for complications or failures of conservative therapy.
Gastric Bypass Surgery
Pulmonary embolism is the leading cause of perioperative death in bariatric surgical patients.11,54 Although
the reported incidence of PE in this patient population is
low (1–2%), PE accounts for nearly one third to one half
of deaths after gastric bypass surgery.43,54 This does not
appear to be altered by routine use of perioperative DVT
prophylaxis. Perioperative VCF placement has been suggested for prophylaxis. In a 24-year retrospective review
that looked at specific risk factors for developing fatal PE,
Sapala et al.58 identified venous stasis, body mass index of
⬎60 kg/m2, truncal obesity, and hypoventilation syndrome/
obstructive sleep apnea as significant risk factors for VTE.
In the presence of a combination of these factors, the
authors recommended prophylactic IVC filter placement.
Patients With Cancer
Since Trousseau’s first observation in 1865, the association between cancer and thrombosis has been well
established. The annual incidence of VTE among patients with cancer is estimated to be 1 in 200.41 Chemotherapy increases the risk 6.5-fold.29 Furthermore, a
recent prospective, randomized trial comparing the efficacy of dalteparin versus coumadin in preventing recurrent thrombosis in patients with cancer revealed a 13%
combined probability of recurrence at 6 months.42 This
has led some investigators to adopt an aggressive approach to VTE prophylaxis in these patients with a
liberal policy toward the use of IVC filters.
On the other hand, the limited life expectancy of
patients with cancer may not justify the cost or potential
risk for thromboembolic complications. In a retrospective review of patients with malignant disease and VTE,
the 1-year survival rate for those treated with an IVC
filter was 35%, whereas major recurrent thromboembolic
complications developed in 17% of patients.35 Jarrett et
al.36 reported a similar, dismal 26.8% survival rate at 1
year in 116 patients undergoing active treatment for
malignant disease and who had IVC filters placed for
established indications. They concluded that prophylactic filter placement may be of little benefit in this group.
333
High-Risk Trauma Patients
Deep vein thrombosis and PE are common complications of trauma. Endothelial damage, changes in the
coagulation cascade, and prolonged immobilization occur frequently in multiply-injured patients, rendering
them at high risk for VTE. Using serial impedance
plethysmography and contrast venography for diagnosis,
a prospective evaluation of patients with major trauma
(injury severity score ⱖ9) revealed a 58% incidence of
lower extremity DVT, 18% of which involved popliteal
or more proximal veins.19 In addition, Schultz et al.60
observed a 24% incidence of asymptomatic PE diagnosed by chest computed tomographic scan. Effective,
aggressive but safe prophylactic measures are therefore
warranted. These generally include anticoagulation therapy, sequential compression devices (SCDs), and a DVT
screening protocol with serial venous duplex. There are,
however, 2 main issues associated with this approach.
First, it has been shown that up to 35% of trauma patients
have physical impediments to application of SCDs such
as plaster immobilizers, external fixators, complex
wounds, or traction.62 A significant number of these
patients, especially those with solid organ or head injuries which are managed conservatively, cannot be given
anticoagulation. Second, a metaanalysis of existing evidence clearly showed that there is no evidence to support
any 1 method of posttraumatic thromboprophylaxis as
superior to another method or to no prophylaxis at all.67
Thus, many trauma surgeons have opted for the prophylactic use of VCFs to manage this risk.
There is no question that VCFs are efficacious. Numerous studies and a metaanalysis have convincingly
shown that patients with a prophylactically inserted VCF
have a lower incidence of PE compared with concurrently managed patients without a VCF or historical
controls without a VCF.38,40,68 Nonetheless, there is considerable controversy regarding this approach, primarily
as a result of the relatively young age of the patient
population and the lack of long-term data. The evidence
would indicate, however, that the risk– benefit ratio is
favorable for prophylactic VCF insertion in high-risk
trauma patients. To define high risk, the Eastern Association for the Surgery of Trauma Practice Management
Guidelines on VTE identified patients with spinal cord
injuries or spinal fractures (level I recommendation),
older age, increased injury severity score, and blood
transfusion (level II) as risk factors for VTE after injury.55 Patients with multiple long bone fractures, complex
pelvic fractures associated with long bone fractures, and
severe closed head injuries (Glasgow coma score ⬍8)
are likewise considered by many as high-risk injury
patterns for PE.38,40,56,72 With the advent of retrievable
Techniques in Orthopaedics®, Vol. 19, No. 4, 2004
334
L. L. KAW AND R. B. DILLEY
TABLE 3. Summary of Comparison Data
Device*
No.
Simon Nitinol
Vena Tech LP
Vena Tech LGM
Stainless steel Greenfield
Titanium Greenfield
Gianturco-Roehm Bird’s Nest
TrapEase
Recovery
319
30
1050
599
511
1426
189
32
Günther Tulip
91
Duration of
Follow Up
(months)
16.9
2.3
12
26
5.8
14.2
4.2
223 (days)
(4–522)
85 (days)
(7–420)
Recurrent
PE (%)
IVC
Thromboses
(%)
3.8
0
3.4
2.6
3.1
2.9
0.5
0
0
DVT
Retrieval
Success
(%)
Mean
Implantation
Period (Days)
7.7
0
11.2
1.7
6.5
3.9
1.5
0
8.9
10.3
32
7.3
22.7
6
1.5
0
—
—
—
—
—
—
—
100
5
0
98
—
—
—
—
—
—
—
53
(5–134)
9
(2–25)
*Data for the OptEase filter not available.
PE ⫽ pulmonary embolus; IVC ⫽ inferior vena cava; DVT ⫽ deep vein thrombosis.
filters, we foresee more widespread application in this
patient population.
COMPARISON OF INFERIOR VENA CAVA
FILTERS
The effectiveness of IVC filters is generally measured
in terms of its ability to prevent PE while maintaining
caval patency. Unfortunately, there is no prospective,
randomized study comparing the effectiveness and complications associated with currently available IVC filters.
Retrospective studies abound but direct comparison and
analysis of pooled data are difficult as a result of wide
variations in the population studied, indications, associated treatment, and follow up. Presently, no one filter
appears to be superior to the next, but one may have
distinct attributes that would be ideal for a particular
application. Table 3 summarizes the comparison data of
currently available IVC filters based on reviews by
Streiff,66 Kinney,39 and individual case series.5,26,45,61
Temporary or Retrievable Filters
Concerns regarding the long-term safety of VCFs and
the report by Decousus et al.,15 demonstrating only
short-term (12 days) benefit of IVC filter insertion in
preventing PE, have sparked considerable interest in the
use of removable filters. Historically, there are 2 types of
removable filters: temporary filter and retrievable filter.
Temporary filters are designed for mandatory removal
and therefore remain attached to an accessible transcutaneous catheter or wire. Retrievable filters are similar to
permanent filters but with modifications to facilitate
subsequent removal. These filters may also be left in
place indefinitely. If temporary filtration is indicated, it
is recommended that these filters be removed within 14
days. Although successful retrieval have been reported
Techniques in Orthopaedics®, Vol. 19, No. 4, 2004
up to 134 days,5 significant neointimal proliferation at
the attachment sites may preclude safe removal beyond
the recommended time period. However, prolongation of
implantation time is feasible with repositioning of the
device to a different site.14,52
Although indications for use of retrievable filters have
not been established, potential use include prophylaxis
for high-risk trauma patients with a contraindication to
anticoagulation and in patients undergoing gastric bypass
surgery or total hip arthroplasty in whom the risk for PE
is highest in the perioperative period. We anticipate
further expansion of these indications as clinical experience for retrievable IVC filters continues to grow.
Removal of retrievable filters can be challenging and
fraught with risks. Major complications include retrieval
failure, IVC perforation, PE (from captured emboli), and
filter embolization. These risks must be weighed against the
long-term complications of permanent filter placement.
Complications
Major complications from IVC filter placement occur
infrequently. A large single-center review comprising
1765 VCF insertions reported a major procedural complication rate of only 0.3%.7 Likewise, VCF-related
death is a rare event and is usually the result of fatal PE.
Other uncommon causes include exsanguination from
IVC perforation, pericardial tamponade or fatal arrhythmia from filter migration to the heart, and the serious
limb complications of IVC thrombosis. These complications can occur during insertion, shortly after the procedure, or months to years later. The majority of adverse
events reported in the literature are associated with longterm use of the device and include recurrent PE and IVC
thrombosis. The incidence of recurrent PE and IVC
thrombosis among current VCFs is summarized in Table
3. Note that there is a considerable variation in compli-
USE OF VENA CAVA FILTERS
cation rates between devices and this difference reflects
the lack of prospective, randomized data.
Short-term complications may be insertion- or deployment-related. Insertion-related complications are associated with obtaining central venous access and include
bleeding, infection, pneumothorax, air embolism, arterial
injury, and arteriovenous fistula formation. Deploymentrelated complications are usually a function of technique
and are largely avoidable with proper imaging and familiarity of the devices used. For instance, incorrect orientation of a filter can occur when the filter is improperly
loaded or is placed through an inappropriate access route.
All currently available filters with the exception of the
Recovery filter can be inserted from the jugular or femoral
routes. Moreover, all filters with the exception of the Bird’s
Nest and the TrapEase filters need to be oriented correctly
depending on the access route chosen. The efficacy and
stability of inverted filters are unknown and therefore care
must be taken to avoid this complication.
Improper placement of a filter can result from inadvertent extrusion of the device during deployment or
incorrect estimation of its intended position in the IVC as
a result of inadequate imaging or the presence of a variant
anatomy, which was missed. This can lead to placement of
the filter either higher (suprarenal IVC) or lower (iliac
veins) than expected or in another vessel along the access
route (renal vein, right atrium). Again, the importance of
preprocedural imaging cannot be overemphasized.
Full-thickness penetration of the filter through the
caval wall is often seen with imaging but is of unknown
clinical significance. The majority of cases are most
likely asymptomatic; however, erosion of the device into
contiguous structures have been reported with disastrous
consequences.2,57
CONCLUSION
Inferior vena cava filters are effective in providing
protection from life-threatening PE. A number of devices
are available and provide comparable efficacy and safety
profiles. The ease of insertion and low complication rate
of currently available devices have expanded the indications for filter placement. Caution, however, should be
exercised in their liberal use. The relative lack of solid
scientific evidence to determine appropriate indications
and the absence of long-term data should be taken into
account. Retrievable filters are appealing and may take a
broader role in thromboprophylaxis in the future.
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