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Cementing Technique
Contents
Chapter 43 Polymethylmethacrylate Cements forEndoprosthetics – 497
Klaus-Dieter Kühn
Chapter 44 The Principles ofTotal Knee Arthroplasty Cementing
Technique– AJapanese Perspective – 511
Takao Kodama
Chapter 45 Inuence ofCement Storage Temperature onIts
Viscosity andPenetration Depth intheTibia During
Total Knee Arthroplasty – 521
Maarten Verheyden, Dries Van Doninck, Frank Verheyden,
and Klaus-Dieter Kühn
IX
Chapter 46 Antibiotic-Loaded Bone Cement: Pro – 529
Matthew W. Squire
Chapter 47 Antibiotic-Loaded Bone Cement: Con – 541
Shayan Hosseinzadeh, Hugh Gorman,
and Antonia F. Chen
Chapter 48 Enhancement ofRelease Prole ofAntibiotic
fromAntibiotic- Loaded Poly(methyl methacrylate)
Bone Cement forAnchoring ofTotal Joint
Arthroplasties: AState-of-the- Art Review – 549
GladiusLewis
Chapter 49 Tourniquet Use inCemented Total Knee
Arthroplasty – 559
Carl L. Herndon and H. John Cooper
Polymethylmethacrylate
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Cements forEndoprosthetics
Klaus-DieterKühn
Contents
43.1 Introduction – 498
43.2 History – 499
43.3 Cement Viscosity – 500
43.4 Flow Behavior andIntrusion – 502
43.5 Doughing Time andIntrusion – 503
497
43
43.6 PMMA Cement When Loaded withAntibiotics Serves
asanActive Drug Carrier Reducing Infection Rates
andMortality – 505
43.7 Malnutrition asanUnderestimated Risk Factor forDeep
Wound Infection – 506
43.8 Metabolization ofAntibiotics – 507
43.9 Manual Admixing ofAnti-microbials – 509
References – 509
© The Author(s), under exclusive license to Springer-Verlag GmbH, DE, part of Springer Nature 2022
E. Hansen, K.-D. Kühn (eds.), Essentials of Cemented Knee Arthroplasty,
https://doi.org/10.1007/978-3-662-63113-3_43
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43.1 Introduction
PMMA bone cements have been successfully used in
surgery for over 60years to anchor articial joints, and
as a local drug carrier. As a two-component system,
the liquid monomer is mixed with the polymer powder
before use in a suitable mixing bowl or in a mixing system to form a homogeneous dough. The cement dough
can have a high, medium, or low viscosity (HV, MV,
LV), depending on the composition of the bone cement
used (Lewis 1997; Kühn etal. 2005a; Kühn 2014; Bistol
etal. 2019). LV cements are preferably used in the spine
to ll vertebral bodies with a thin injection needle (Lewis
2006). In a few countries, LV cements are also found in
knee endoprosthetics, although registry data point out
that LV cements show lower survival rates. The “transatlantic paradox” shows the different attitudes of surgeons in the United States and in Europe regarding the
use of local antibiotics via ALBC. ALBC is routinely
used in primary interventions in Europe, while plain
bone cement (PBC) is used in the United States (SanzRuiz etal. 2017). An actual review of the National Joint
Registry of England and Wales including over 700,000
total knee arthroplasties (TKAs) demonstrated the use
of ALBC was associated with a decreased risk of revision as compared to TKAs implanted with PBC.ALBC
was associated with a 19% lower rate of septic and aseptic revision as compared to PBC (Jameson etal. 2019).
Furthermore, the additional cost of ALBC per TKA
case is $300–$500 as compared to PBC.The additional
cost of ALBC in 115 patients would be $34,000–$57,000.
Given the average cost of treating one periprosthetic
joint infection (PJI) is approximately $100,000 the use
of ALBC potentially results in signicant cost savings
(Jameson etal. 2019; Sanz-Ruiz etal. 2020).
HV cements, together with the MV version, are used
worldwide as anchoring material in over 90% of articial joints. Highly viscous cements can, therefore, be
described as a “gold standard”, especially in combination with suitable antibiotics to prevent periprosthetic
infections (Colas etal. 2015; Chan etal. 2019).
> High-viscosity PMMA cements are mainly used in
large joints, whereas the use of low viscosity is rela-
tively rare.
> ALBC is used in most primary procedures to prevent
periprosthetic infections. ALBCs reduce the risk of
biolm formation on the implant surface. Antibiotics
only have an adjuvant function, the therapy is the sur-
gery!
The modern cementing technique allows for the clinician to mix the cements in partially (e.g., SMART Mix®,
CEMVAC®, MixeVac®) or completely closed cement-
ing systems (e.g., PALAMIX®, PALACOS® R+G
PRO, CEMVAC®). For the surgeon, the point in time
when the cement paste is ready for application is crucial. In addition, a sufcient processing width is desired
by most users. The complete setting of the cement paste
should not take too long, since the duration of surgery
has a signicant inuence on the effectiveness of a treatment. However, in surgical practice, different operations
are carried out in parallel, so that such key gures alone
are of little signicance. In addition, quality should
take precedence over speed; effectiveness is ultimately
measured by the overall success, which in the case of
anchored articial joints is reected in the long-term
survival of the implants.
> Modern cementing technology today offers com-
pletely closed cementing systems in which the application phase of the dough is dened.
Cemented prostheses show the best survival rates in
patients who were treated with local antibiotic treatment with broad-spectrum antibiotics in addition to
systemic antibiotics during surgery. This ensures that
hematogenically dispersed bacteria and those found on
the skin are signicantly reduced by systemic administration of antibiotics while local antibiotic administration builds up a protective shield as a colonization
barrier around the implant. This sensible prophylactic approach has led to infection rates remaining at a
relatively low level to this day (Buchholz et al. 1981;
Phillips et al. 2006; Jameson et al. 2019; Zhang et al.
2019) (7 Sect. 43.2). Therapeutically, local adminis-
tration of antibiotics is usually used in combination
with systemic antibiotics. Narrow- spectrum antibiotics
are combined with ALBC containing broad-spectrum
antibiotics because the elution behavior is signicantly
improved by synergy (Kühn 2014). The elution properties of commercially available ALBCs also vary considerably and valid release data are only available for a few
products. PALACOS®R+G was approved as a drug at
the end of the 1960s and publications on the comparatively excellent elution behavior of gentamicin from the
cement matrix were submitted to the health authorities
for approval. When determining the elution behavior, a
reproducible method must be used.
Unfortunately, many data presented in the literature are difcult to compare. There are microbiological
limits to the number of inhibition tests, which often go
unnoticed. Recent studies show marginal differences
in the inhibition peak test of PMMA cements (Squire
etal. 2008) and low antibiotic releases below the minimal inhibitory concentration (MIC) after 24h (Meyer
etal. 2011). Our own investigations on elution and on
inhibition yard tests show large differences between the
PMMA cements on the market (Kühn 2018).
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> Broad-spectrum antibiotics (antibiotics with broad
efcacy) should be used systemically (e.g., cephalosporins) and locally (e.g., aminoglycosides) for prophylaxis; narrow-spectrum antibiotics (antibiotics
with narrow efcacy) (e.g., vancomycin against
MRSA) should be used in a targeted therapy.
Today, ALBCs– especially revision cements with more
than one antibiotic– are hardly ever approved as Class
III medical devices, not least because the requirements
for certication are disproportionately high– much to
the disadvantage of patients and surgeons. In surgical
practice, antibiotics are, therefore, manually added to
the cement, in the best case depending on the patient’s
as well as the hospital’s antibiogram. However, manual
mixing also involves some risks and the surgeon bears
responsibility in this “off label” use.
> PMMA bone cements were used to be medicinal
products and were redened as medical devices in
1998. When antimicrobial agents are added manually,
the medical device is modied and the surgeon bears
responsibility in this “off label” use.
43.2 History
PMMA bone cements were developed based on dental
materials (Smith 2005; Smith and Bains 1956; Kühn
2014). Initially, some changes in formulation were
marginal. However, with increasing interest from surgeons, the original dental products were increasingly
adapted to the requirements as anchoring material for
articial joints. The formulation in the two older products PALACOS®R and Simplex®P has probably not
changed signicantly over the decades. In contrast, the
formulation of many other products on the market has
changed over the years, sometimes signicantly. Under
pharmaceutical legislation this would only have been
possible to a very limited degree. However, this has
been facilitated under the Medical Device Directive
via change notications, of which some manufacturers
make use. Just replacing the polymers leads to a change
of about 80–90% of the formulation, resulting in a
completely new product. Chemically similar polymers
are not identical in their properties, therefore, changing polymers without clinical data involves considerable
risks. For that reason, only a few PMMA bone cements
were commercially available before 1998, and the formulations had to be stated exactly on the packaging and in
the package insert.
> Chemically similar polymers or co-polymers are not
identical in their properties.
At that time, all individual components of the liquid monomer and polymer powder were regarded as
medicinal products. Requirements and handling of these
medicinal products were strictly regulated by Good Manufacturing Practices (GMP). Only a few manufacturers
of bone cements had a license as pharmaceutical companies that could produce and distribute such products.
With the changeover to the Medical Device Directive,
PMMA bone cements were no longer subject to pharmaceutical legislation. Today, numerous cements are commercially available and while they all may seem to be very
much alike, the only thing they have in common is the
basic chemical principle of radical polymerization.
> PMMA bone cements were developed based on den-
tal materials. Older products such as Simplex®P and
Palacos®R have probably still retained their basic
formulation to this day.
The rst ALBC was Palacos®R with added gentamicin. Buchholz et al. (1984), together with Heraeus
(Kulzer), added various amounts of gentamicin powder
to the Palacos powder in the late 1960s and tested the
release behavior of the incorporated active ingredient.
Gentamicin was very well released from the Palacos
matrix. The success story of ALBC in endoprosthetics
via Palacos®R+G (former Refobacin®, Palacos®R,
Palacos®R cum Gentamicin, and Palacos®R with
Gentamicin) began with Heraeus (Kulzer), who started
out marketing their products themselves, but later outsourced marketing to various distribution partners
(Merck, Schering-Plough, Smith & Nephew, Biomet,
Zimmer) (Kühn 2007, 2014). In 2017, the Australian
Orthopedic Association (AOA) published a supplementary report on bone cement in hip and knee arthroplasty.
The report covered 293,025 primary TKA procedures
and 9753 revisions between 1999 and 2015 (AOA 2019).
> Palacos®R+G (syn. Refobacin®, Palacos®R,
Palacos®R with Gentamicin) was the rst ALBC on
the market (1969). The use of Palacos®R+G reduced
the infection rate (.
double- digit percentages to below 1% (Buchholz etal.
1981; Phillips etal. 2006).
Fig. 43.1) of initially almost
In addition to gentamicin (PALACOS®, Simplex®,
SmartSet® etc.), tobramycin (Simplex®), erythromycin and colistin (Simplex®), clindamycin (PALACOS®), and vancomycin (PALACOS® and others) are
commercially used in ALBC. The so-called “revision
cements” include Copal®G+C, Copal®G+V, Antibiotic Simplex with Erythromycin and Colistin, and VancoGenx. Copal® products, in particular, are often used
today as the basis for cemented revision procedures in
500
1964–1968
1968–1971
Infectionrate %
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. Fig. 43.1 Reduction rate of
infections after introduction of
PALACOS®R+G in the market
below than 1%. (Data according
to Buchholz etal. 1981; Phillips
etal. 2006). The use of local
antibiotics has also led to a
drastic reduction in the risk of
infection
7.5
7
6
5
43
4
3
2
1
0
4.1
1.6
1972
one-stage and multiple-stage surgery (Kendoff et al.
2015; Sprowson etal. 2016; Kühn 2018). The combina-
tions are adapted to the surgical practice. Microbiotic
analyses in antibiograms show which active ingredients
eliminate the detected germs. Intelligent combinations
include gentamicin with vancomycin and gentamicin
with clindamycin. Different synergies can be observed
with gentamicin and vancomycin. While vancomycin,
in particular, is more effective against certain germs in
the presence of gentamicin, vancomycin elution is also
increased in the presence of gentamicin. The molecule
gentamicin acts as a “backpack” carrying the large molecule vancomycin out of the cement matrix.
> Revision cements contain combinations of antibiotics
with intelligent synergistic effects which increase the
clinical effectiveness and elution properties.
Clindamycin in combination with gentamicin has the
synergistic advantage of being effective against about
90% of all relevant germs found in joint infections.
This extension of the spectrum of action has, among
other things, prompted clinics to use this combination in cement in high-risk patients in primary surgery
(Adelaziz etal. 2019). Gentamicin and clindamycin are
also released particularly well from PMMA cement as
low-molecular-weight hydrophilic agents.
> Active ingredient combinations effectively prevent the
development of resistance as the different antibiotics
damage the bacterial cell at different targets.
1.5
1.5
1.4
0.8
1973
0.6
1974
1975
1976
1977
0.7
1978
1979
0.4
0.6
1980
Active ingredient combinations have already been
successfully used for many serious diseases. Microbiologically, combinations of antibiotics of different antibiotic classes in surgery still have an important effect
based on the different targets at which the respective
antibiotics attack bacteria. By evolution, each administration of antibiotics can result in the accidental
development of resistant bacteria. However, if antibiotics attack the bacteria in two different ways at once,
the potential development of resistance is signicantly
reduced.
43.3 Cement Viscosity
PMMA bone cements consist of two essential components, the liquid monomer and the polymer powder.
Monomers include the basic substance of all PMMA
cements, methylmethacrylate (MMA), as well as the
activator for radical polymerization, di-methyl-paratoluidine (DmpT), hydroquinone (HQ) as a radical
scavenger and, if necessary, a dye (e.g., chlorophyll). The
polymer powder contains homo- or co-polymers which
have a signicant inuence on
5 the properties of the cement later anchored in the
body,
5 the initiator benzoyl peroxide (BPO) which together
with the DmpT of the liquid initiates polymeriza-
tion,
5 an X-ray contrast medium (zirconium dioxide [ZO]
or barium sulfate [BS]),
0.3
1981
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5 a dye, and
5 in the case of ALBCs, one or two antibiotics (Bistol
etal. 2019).
Polymer powder and monomer liquid are usually available in a ratio of 2:1, the polymer powder in a sterile
bag and the liquid in a sterile amber glass ampoule. The
polymer powder is sterilized by γ-radiation or ethylene
oxide, the liquid is sterile-ltered. The sterilization process of the polymer powder has a signicant inuence
on the polymer properties. The molecular weight of the
polymers is signicantly reduced by γ-rays, and the handling properties and viscosity are also inuenced (Lewis
and Mladsi 1998; Deb 2008; Kühn etal. 2005b). Ethylene oxide (Eto) sterilization, on the other hand, shows
almost no interaction with the polymer. The following
parameters change by γ-irradiation of the powder (sterile) compared to the non-sterile powder:
Inuence of γ-Irradiation on Polymer Powder
5 Powder color: slightly changed (white to slightly
grey)
5 Doughing time (much later)
5 Working time (extended)
5 Setting time (much later)
5 Viscosity prole (changed)
5 Molecular weight (signicantly reduced, approx. 50%)
5 ASTM/ISO standard mechanicals (initially high,
then signicantly reduced by aging)
5 Aging (increased)
Mixing the components results in a homogeneous
dough. However, mixing also means energy input: The
stronger the mixing process, the shorter the handling
properties of the cement used. Furthermore, the viscosity behavior of PMMA cements is essentially inuenced
by the following properties:
Factors Inuencing PMMA Viscosity
5 Ambient temperature
5 Component temperature (e.g., cooled cement)
5 Mixing procedure (e.g., speed of mixing)
5 Powder–liquid ratio
5 BPO(initiator)–DmpT(activator) ratio
5 Physical properties of the polymer powder (surface
of the beads)
5 Swelling behavior of the powder with MMA
5 Chemical properties (composition of the polymers/
co-polymers)
5 Mixing device (e.g., vacuum, speed, nozzle shape)
> The sterilization of the polymer powder has a signi-
cant inuence on the cement properties. γ-Rays
change polymers permanently and lead to acceler-
ated aging; ethylene oxide does not change the poly-
mer.
Charnley (1970) concluded, the more powerfully and
the longer the cement components are mixed, the more
porous the cement will be in the dough phase. This particularly applies to the mixing of low-viscosity cements.
LV cements are quickly mixed homogeneously, so no
additional energy input is required. When mixing LV
cement under vacuum, it should be noted that too high
a vacuum can cause the monomer to boil and thereby
form numerous and sometimes large gas bubbles in the
cement.
> With low-viscosity PMMA cements, the liquid mono-
mer can be brought to the boiling point in vacuum
and many air bubbles can be formed in the cement
paste.
A study by Buller etal. (2020) showed higher odds of
aseptic loosening by using HV cements compared to LV
cements with a higher exothermic reaction of HV cements
(Webb and Spencer 2007). The authors report results
with Simplex®HV; PALACOS®R served as reference.
However, in contrast to PALACOS®R, Simplex®HV
has a signicantly lower viscosity, so tendencies toward
aseptic loosening were found with the LV material, but
not with the HV cement.
The results of Buller etal. (2020) are in strong contrast to the register data of the National Joint Registry
(NJR) (Jameson et al. 2019) and Northern European
countries, which show best survival rates (Kaplan Mayer
Curve) with HV PMMA cements (Espehaug etal. 2002)
(. Fig.43.2).
> High-viscosity PMMA cements are used in cemented
endoprosthetics in about 90% of all major joint oper-
ations and are considered the gold standard.
Independent register data show superior survival
rates of HV cements compared to LV cements.
T
of cements especially depends on the MMA and
max
BPO content of the PMMA cement used. While the
MMA content of many cements is similar (powder–liquid ratio 2:1), the BPO content can vary considerably.
Especially Simplex®P has the highest BPO content on
the market and, therefore, tends to have a higher setting
temperature.
> T
of PMMA cements is not determined by viscos-
max
ity but by the amount of MMA and BPO.
502
y
Years
Not revised
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. Fig. 43.2 Cemented
prostheses anchored with HV
cements show best survival rates
100
98
96
94
92
90
High viscosit
Low viscosity
Boneloc
P < 0.0001
0
43
. Fig. 43.3 “Doctor’s nger test” according to ASTM F451/ISO 5833. Sticky cement dough (left) and cement reaching the doughing time
of PMMA cements (right)
43.4 Flow Behavior andIntrusion
. Table 43.1 Doughing time mean of 4 commercial
PMMA cements according to ASTM 451 and ISO 5833
Ideally, bone cements are used when the cement is no
longer sticky. The standards ASTM 451 and ISO 5833
Cement ASTM 451 at 20°C ISO 5833 at 23°
valid for PMMA bone cements have specied a “doctor’s
nger test” for this purpose (ASTM F451-99a 2014; ISO
5833 2002) (. Fig.43.3). ASTM standard tests are done
at 20°C, ISO standard tests at 23°C (. Table43.1). The
mean value of a double determination of one package
each (40g/20mL) is determined as doughing time (DT).
Palacos®R 75s 55s
SmartSet® HV 75s 65s
Palacos® MV 135s 80s
Simplex®P 300s 220s
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> Doughing time is a measure of the ideal time for
cement application in the body and is dened as the
time when the cement dough is no longer sticky.
This so-called doughing time has historically been
dened as a measure of the ideal time for manual
cementing of the bone. When the standard was introduced, considerable uctuations in results obtained were
already noted. This was due to the fact that in Europe
doughing time was measured with a glass rod and in the
United States with a nger in a latex glove. In addition,
measurements were also made at different ambient temperatures.
Considerable differences were found between the
various cements. At that time, Simplex®P had a DT
about 4min longer than that of Palacos®R.The standards committee explained this by the different viscosity
progression of the cements.
> Historically, doughing time has been tested to deter-
mine the time when the cement dough is no longer
sticky after start of mixing. When using closed
cementing systems without cement contact, doughing
time again becomes important.
With the introduction of modern cementing technique, DT was no longer considered important at rst.
However, with the introduction of many new PMMA
cements with unknown handling properties, it became
clear that DT also represents a check on whether the
cement was produced in accordance with the specications. In addition, when using closed cementing systems,
contact with the cement dough may be absent and thus
a direct manual determination/estimation of when the
dough is tack-free can be made.
43.5 Doughing Time andIntrusion
The doughing time of PMMA cement is carried out in
a double determination with a powder-free latex glove.
For this purpose, the cement is not extruded, but only
stripped at the top of the nozzle, so that the monomer
does not evaporate too quickly and distort the results
(. Fig. 43.3). Cement units are conditioned at 20
°C/23 °C ± 1 °C.Subsequently, the DT is determined
according to ASTM F451/ISO 5833. Directly after the
determination of DT, the intrusion is determined 1min,
2min, and 3min after the tested DT.
Compared to the 3 other PMMA cements investigated, Palacos®MV has a different mixing ratio of
44 g/20 mL. This 10% difference in mass may signicantly inuence our test results.
Simplex®P cement dough is known to be tack-free
on the surface earlier while on the inside the dough
clearly is still sticky. Therefore, the DT of Simplex®P
cannot be determined beyond doubt. The manufacturer
also refers to this phenomenon in the package insert
and recommends that surgeons process Simplex®P only
after 3–4min.
> DT values according to ASTM 451 and ISO 5833 are
not comparable, since the measurement is made at
different component and ambient temperatures. In
addition, cements may already be tack-free on the
surface, while the dough is still sticky on the inside
(e.g., Simplex®P).
The determination of intrusion is mainly based and
inuenced on the results of the DT determination, as the
measurement is performed 1min after reaching DT.For
this purpose, the cement is placed in a cylindrical form
with 4 holes of 1mm of diameter each and pressed into
the 4 holes with a punch pressure of 49N.The measurement is carried out according to ISO at 23°C or according to ASTM at 20°C.Shaped bodies with 4 holes and
the corresponding pins are produced. The height of the
pins in mm corresponds to the intrusion (.
Fig.43.4).
However, as mentioned above, not every cement is
ready for application after reaching the DT according to the standard determination. This is due to the
behavior of some polymers or co-polymers and their
interaction with the starter system (BPO-DmpT) for
polymerization. For example, Simplex®P contains a
styrene co- polymer and the BPO is polymerized into
polymer beads. This reduces quick availability of the
BPO.In many other PMMA cements, the BPO is freely
present in the polymer and is immediately available. The
voluminous styrene-containing co-polymer powder of
Simplex®P is wetted by the monomer liquid with a time
delay, which may also be a reason why the cement paste
produced is initially dry. The dry top layer of the dough
apparently results in Simplex®P being free of surface
tackiness according to ASTM or ISO, while the dough
still is quite sticky on the inside. Therefore, additional
waiting time is recommended for the application, so that
the cement can optimally be used.
> The optimum time for cement application in the bone
is associated with a certain viscosity. The dough
should be tack-free and able to withstand bleeding
pressure.
However, this also means that the intrusion of
Simplex®P cannot be determined at the time of DT
according to ASTM or ISO, but only after an addi-
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. Fig. 43.4 Intrusion measurement and specimen with 4 holes to detect the intrusion (in mm) 4-times
43
. Table 43.2 Intrusion measurement [mm] according to
ASTM F451/ISO 5833 at 20°C, intrusion at the time after
doughing state is reached [min]
Product 1min 2min 3min
Palacos®R 11.4mm 10.1mm 3.1mm
SmartSet HV 11.7mm 4.8mm 2.9mm
Palacos MV 16.8mm 8.2mm 2.1mm
Simplex P 15.4mm 7.5mm 2.2mm
tional waiting phase recommended by the manufacturer
(+3–4min). Since the intrusion capacity of the cements
should represent cement penetration into the cancellous bone at the time of application (+1min), intrusion
results can only be compared if the operative basis– i.e.,
the start of the application phase– applies.
Theoretically, all PMMA-based bone cements should
have a comparable viscosity at the optimal application
time, which leads to comparable penetration into the
cancellous bone (.
Table43.2).
While the mixing systems used in the operating room can
inuence DT and intrusion, the waiting time after reaching DT is highly essential. With high-viscosity Palacos®R,
the ASTM/ISO intrusions are between 4mm and 6mm.
Without taking the waiting time into account, Simplex®P
has penetration depths of 8–12mm (. Fig.43.5a).
However, if the waiting time of 3–4min recommended
the manufacturer is considered after DT, intrusion of
Simplex®P is comparable (approx. 4mm) to that of highly
viscous Palacos®R (. Fig.43.5b) because then the viscosity of both cements is comparable (. Table43.2)!
> If used correctly, Simplex®P and Palacos®R show
comparable intrusion in the bone.
The use of low-viscosity PMMA cements is often linked
to easy mixability and ideal interdigitation with the
cancellous bone (Lewis and Carroll 2002). Theoretically, low-viscosity bone cements can only have a better
penetration depth into the bone if they are introduced
to the body too early, i.e., if they are not applied correctly! Regardless of the classication HV, MV, or LV
cements, the use of these cements in the body is always
associated with a comparable viscosity. The technical
basis for this is the determination of DT.If LV cements
are applied too early (before DT is reached) there is a
risk of the dough pouring out. In this phase, LV cement
cannot withstand the bleeding pressure yet, and mixing
of cement and blood can easily occur. This leads to a
lasting mechanical weakening of the cement matrix. In
addition, cement constituents can more easily enter the
venous system and thus increase the risk of embolism.
> Low-viscosity bone cements are often introduced to
the body too early. This is associated with higher risks
of embolism and necrosis. Blood can easily mix with
the cement dough and signicantly weaken the
cement matrix after setting.
In a so-called bleeding apparatus, Lee (2005) explained
that the bleeding pressure will force LV cement brands
out of the bone and blood can be entrapped in the
cement dough. Because of the low DT and short working time, LV cements are often applied too early to the
body. In addition, vacuum mixing of LV cements may
be performed only under a low vacuum of approxi-
Intrusion
a
in [mm]
St
In [mm]
Test time after doughing time [in minutes]
Polymethylmethacrylate Cements forEndoprosthetics
https://t.me/medicina_free
. Fig. 43.5 a Comparison of
intrusion according to ASTM
F451/ISO 5833 after mixing of
Palacos®R and Simplex®P in
various mixing systems. b
Intrusion of Simplex®P 2, 3, 4
and 5min after reaching DT
14
12
10
8
6
4
2
505
43
0
1 + Palacos
Palamix
b
9
8
7
6
5
4
3
2
1
0
Palamix
2 min
R
2 + Palacos
R
Biomet Optivac
R
+ Palacos
Stryker Revolution + Palacos
Intrusion Stryker revolution with Simplex P
3 min
R
Palamix
1 + Simplex
P
2 + Simplex
Palamix
4 min 5 min
P
+ Simplex
Biomet Optivac
ryker Revolution + Simplex
P
P
mately 550mbar. However, such a low vacuum will not
be sufcient to fully eliminate the pores in the dough
(Draenert et al. 1999). Therefore, vacuum mixing at
room temperature at a pressure of 15 mbar will result
in a boiling monomer due to its vapor pressure being a
function of temperature.
Furthermore, too deep an intrusion into the bone
can be associated with a high cement surface in the bone,
which carries an additional necrotic risk. The drainage
systems (bloodstream, metallic prosthesis, tissue) can
then no longer neutralize the heat development of the
deeper-lying cement.
43.6 PMMA Cement When Loaded
withAntibiotics Serves asanActive
Drug Carrier Reducing Infection Rates
andMortality
Periprosthetic joint infection and cancer can share similar traits (Benharroch and Osyntsov 2012). Mortality
rates in oncology have been carefully documented and
declined. On the other hand, mortality rates of PJI are
often underreported. In 2013, the American Cancer
Society published a comparison of deaths from vari-
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