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A. Siddiqi et al.
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31.1 Introduction
The utilization of all-polyethylene tibial (APT) components in TKA has clear advantages, especially in patients
with correctable deformity with minimal tibial bone
loss. As indicated by the study conducted at our institution, the survivorship of APT TKAs in young and active
patients is comparable to that of MBT TKAs and excellent clinical results were observed after 10–18years. The
cost advantage of APT components is substantial per
case and even greater cumulatively at long-term.
Although APT components lack modularity and do not
allow for the usage of stems and augments in complex
primary TKAs, they completely eliminate the concerns
surrounding the issue of backside wear. APT components are a viable and excellent cost-saving option in
contemporary TKA.
31.2 Case Example
An 80-year-old female with past medical history of
hypertension, coronary artery disease, and a body mass
index of 35kg/m2 presents to the clinic with debilitating
left knee pain for a few years from primary end-stage
osteoarthritis. Over the past 6 months, the patient’s
symptoms did not improve with activity modications,
corticosteroid, and hyaluronic acid injections. Her
radiographs demonstrate several medial compartment
and patellofemoral joint space narrowings with osteophyte formation and subchondral cysts and sclerosis
(. Fig.31.1). On physical examination, the patient has
a correctable varus deformity without a thrust during
ambulation. After discussing risks, benets, and alternatives, the patient elects to undergo primary left total
knee arthroplasty. During the surgical procedure, after
all bony cuts and soft-tissue releases are performed to
have equal medial–lateral, exion–extension balanced
gaps, a posterior stabilized femoral component and allpolyethylene tibial (APT) component is cemented into
place (. Fig. 31.2). During a long-term follow-up of
10years, patient continues to have full range of motion
(0–120°) and is pain-free.
31.3 Background
> “Modularity is like an addiction. You know it is bad
for you, but you do it anyway.” (Chitranjan
S.Ranawat, MD)
All-polyethylene tibial (APT) components and metalbacked tibias represent the original total condylar tibial
component design with long-term survivorship over
90% (Ranawat et al. 1993; Gill et al. 1999). Despite
excellent outcomes, biomechanical studies in the early
. Fig. 31.1 Anteroposterior, lateral, and Merchant radiographs demonstrating severe tricompartmental degenerative joint disease
All-Polyethylene Tibial Components in Primary Total Knee Arthroplasty: Why It Works and Why I Do Not Use…
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. Fig. 31.2 Anteroposterior, lateral, and Merchant radiographs demonstrating posterior-stabilized primary TKA with an all- polyethylene
tibial component
1980s described modularity advances that led to widespread adoption of cemented metal-backed modular
(MBT) tibial components globally (Lewis et al. 1982;
Fipp 1983; Bartel etal. 1986). The Annual Report of the
National Joint Registry for England and Wales in 2007
showed that only 3.9% of primary TKAs utilized APT
components (Bettinson etal. 2009). Proponents of MBT
components cite greater intraoperative exibility with
modularity and the ability to apply a porous coating for
cementless xation (Small etal. 2010; Gioe etal. 2007a).
However, many studies comparing APT to MBT have
not been able to demonstrate signicant difference in
outcomes and implant survivorship (Bettinson et al.
2009; Gioe et al. 2007b; Blumenfeld and Scott 2010;
Robinson and Green 2011).
In a nite element analysis, Fipp etal. (1983) found
that compressive stress on cancellous bone was substantially increased when the load was applied to a single
tibial plateau but when the load was equally distributed
to both plateaus, the cancellous bone stress under APT
components was nearly equal to the cancellous bone
under metal-backed tibial (MBT) components.
Therefore, when utilizing APT, it is essential to make a
at tibial cut that is perpendicular to the mechanical
axis to ensure equal load distribution and implant longevity. In a study of 536 at non-conforming coronal
design APT in 405 patients, Faris etal. (2003) reported a
failure rate of 68% at 10years. Fifty-seven (73%) of 79
failures occurred in association with loosening or medial
tibial plateau collapse likely attributed to a varus or valgus tibia cut. The authors found the implant–bone
stresses were the highest with extreme edge-loading with
varus or valgus tilt of the implants with a at articular
geometric coronal plane design.
> Although APT-conforming geometric designs have
substantially improved over the past decade to minimize liftoff and edge-loading, the basic tenet of a at
perpendicular tibial cut and overall limb mechanical
alignment is of utmost importance (Stiehl etal. 1999).
31.4 Surgical Technique
Proper preparation and implantation of APT components require adequate exposure. Ran-Sall maneuver
(Meftah etal. 2012a) is important to properly expose the
tibial surface to ensure an even at cut without softtissue interposition. It is also critical to preserve medial
subchondral bone that will bear the shear stresses across
the APT component during cyclical loading. Since the
APT implants are non-modular, the surgeon must be
satised with intraoperative stability and soft-tissue balance during trialing prior to nal cementation.
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> We recommend cementing the femoral component
rst as cementing the tibia initially is likely to obscure
visualization and not allow for proper removal of
excess cement from the posterior portion of the femo-
ral component.
> This is especially important when using posterior-
stabilized implants since the post of the APT may
prevent femoral component seating.
> Surgeons newer to this technique may consider using
separate bags of cement for the femur and tibia to
ensure appropriate component alignment without
liftoff.
Implants are cemented using the conventional thirdgeneration technique. Any posterior extruded cement is
removed prior to femur reduction on the APT implant.
After the cement hardens, the knee is put through a full
range of motion (ROM) to conrm proper balancing
followed by standard closure of the arthrotomy, subcutaneous tissue, and skin.
Advantages
z
From a technical viewpoint, the tibial resection is generally more conservative to accommodate the minimum
thickness of polyethylene. The lack of modularity eliminates the issue of backside wear from modularity. The
absence of a metal base plate allows the use of thicker
polyethylene inserts, thus reducing the amount of wear
and reducing shear stresses occurring at the cement–
prosthesis and cement–bone interfaces.
Disadvantages
z
Unlike MBT, APT implants may be reserved for individuals with minimal coronal deformity, adequate tibial
bone stock, and normal proximal tibial anatomy. The
lack of modularity signicantly limits intraoperative
options if instability is noted after nal implant cementation (Doran etal. 2015). Furthermore, there are no
options for liner removal in procedures involving irrigation and debridement for acute periprosthetic joint
infection or late TKA revision for instability that
requires a thicker or varus–valgus constrained polyethylene insert (Blumenfeld and Scott 2010; Doran et al.
2015). Finally, as cementless TKA is garnering increas-
ing interest, there are limited APT press-t options.
31.5 Implant Cost
In the current cost-conscious healthcare environment,
there is increased attention to improving the quality of
care while curtailing expenditure. Limiting implant cost
has been an area of focus in an effort to decrease overall
spend per episode of care provided.
> APT implants have been shown to have substantial
cost-saving implications with some studies demonstrating 20% to 50% lower costs versus MBT (Gioe
et al. 2006, 2007a, b; Muller et al. 2006; Gioe and
Bowman 2000; Healy et al. 2002; Najibi et al. 2003;
Pomeroy etal. 2000).
Although some authors have suggested that keeping
both APT and MBT on the shelf increases inventory
costs (Pagnano etal. 1999), the cost appears to be minimal compared with potential savings. In a randomized
controlled trial of 111 APT and 102 MBT TKA, Gioe
etal. (Gioe and Bowman 2000) reported contemporary
congruent APT components with equivalent function to
MBT at mean 49-month follow-up with an average of
$675 (USD) cost-saving per procedure for APT. In
another registry study, Gioe et al. (2007a) reported
99.4% survival at 14.3years with all-cause revision as
the primary endpoint. The estimated cost savings for the
APT was $729 (USD) per case compared to MBT.The
authors further reported that if all patients older than
75years old in the registry received APT, the projected
implant cost savings would be greater than $1.2 million
(USD) (Gioe etal. 2007a).
Browne etal. (2018) constructed a Markov model
analysis to examine cost-effectiveness of APT and determine what difference in revision rates would make MBT
implants a more cost-saving choice. Cost data from the
authors’ institution was used in conjunction with published United States implant list prices and modeled
with a 3% discount rate. The study found that over a
20-year period, a failure rate greater than 27% for APT
would be needed to achieve equivalent cost compared
with the proposed failure rate of 18% for MBT. The
authors concluded that APT implants are cost-effective
if the excess total revision rate increases by less than 9%
in 20 years compared with MBT TKA (Browne etal.
2018).
31.6 Clinical Outcomes
In a study conducted at the Hospital for Special Surgery,
a 10–18-year follow-up study for 44 APT TKAs in 32
patients (12 bilateral TKA) that were 60 years and
younger demonstrated good to excellent outcome in 96%
of patients with implant survivorship greater than 95%.
(Meftah etal. 2012b) The implants were either posterior
stabilized Pressed Fit Condylar (PFC) Modular or Sigma
designs (DePuy Orthopaedics, Inc., Warsaw, Ind).
Clinical analysis included pre- and postoperative vali-
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dated Knee Society Score (KSS), Knee Society Function
Score (KSFS), Western Ontario and McMaster
Universities Osteoarthritis Index (WOMAC), UCLA
activity score and a detailed Patient Administered
Questionnaire (ROC-PAQ) containing separate sections
for pain, daily living activities, sport participation, and
satisfaction (Rasquinha etal. 2006; Cooper et al. 2010;
Ranawat etal. 2004). The KSS improved from 38.3±9.7
to 94±7 and KSFS improved from 51.5±14.1 to 89±20
at an average of 12.4±2.7 years of follow-up. None of
the patients in the study indicated that they were dissatised (satisfaction score less than 5 on the ROC-PAQ) and
the mean satisfaction score was 9.2±1.4. 62% of patients
were participating in sporting activities such as running,
gym exercises, and playing tennis or golf.
The survivorship of MBT TKAs is widely reported
in the literature and ranges from 88.9% to 97.2% at
8–13years (Gioe etal. 2007b; Bozic etal. 2005; Ehrhardt
etal. 2011; Parsch etal. 2009; Stern and Insall 1992). A
number of good-quality studies have also compared survivorship and function of APT and MBT TKAs
(Bettinson etal. 2009; Gioe etal. 2007b).
> The general conclusion has been that the results are
similar at 10years with regard to function, survivor-
ship, patient satisfaction, and radiological parame-
ters.
One prospective study followed APT TKA patients over
14 years and found 99% cumulative survival as compared to 95.1% for MBT patients. The cumulative revision rate for the APT group was 1%, which was
signicantly lower than the 4.9% CRR in the MBT
group (p=0.02).
Houdek etal. (2016) reviewed 31,939 patients undergoing primary TKA (28,224 (88%) MBT and 3715
(12%) APT) over a 43-year period and found APT components to have signicantly improved survivorship
(p < 0.0001) compared to MBT. Interestingly, APT
TKA had improved survival for all body mass index
(BMI) groups except in the morbidly obese subgroup
(BMI ≥ 40) where there was no statistical difference
(p > 0.05). Additionally, APT implants were found to
have signicantly lower rates of periprosthetic joint
infections, instability, aseptic loosening, periprosthetic
fractures, and fewer radiolucent lines. Herschmiller etal.
(2019) also found statistically fewer radiolucent lines
(p<0.001) around APT on plain radiographs compared
to MBT.However, the authors appropriately concluded
that the clinical implications of fewer radiolucencies are
unknown. Through radiostereometric analysis (RSA)
testing, however, Nouta etal. (Nouta etal., 2012) found
that APT had better xation compared with MBT as the
maximum total point motion for APT was 0.6 (± 0.2)
versus 0.89 (± 1.3) for the MBT.
A recent meta-analysis of 32 articles evaluating
58,942 TKA patients demonstrated no signicant differences in patient-reported outcome measures (PROMs)
and functional outcome scores. However, APT had statistically higher revision rates compared with MBT
(2.02% vs. 1.85%, p<0.00001, respectively). The authors
concluded that this nding demonstrates a negative
impact on APT cost-effectiveness and that MBT should
remain the implant of choice. However, the ndings
from the study should be taken with caution since the
quality of evidence of the studies included was low
according to GRADE scoring. Conversely, another
recent meta-analysis of 30 studies from 2000 to 2016
reported level 1 evidence comparing APT and MBT
with no statistically signicant survivorship difference
(Kumar etal. 2019).
In a registry study, Mohan etal. (2013) evaluated the
risk of revision in younger patients (<65years old) and
in older patients (≥65years old) with APT TKA. 27,657
TKAs were evaluated with 2306 (8%) patients having
APT TKA and 25,351 (92%) with MBT components. In
adjusted models, the risk of early all-cause revision
(hazard ratio [HR]=0.5) and aseptic revision (HR=0.6)
was lower for the APT cohort than for the MBT cohort.
In older patients, the early risk of all-cause revision was
0.6 for the APT patients compared to the MBT cohort.
In younger patients, the adjusted risk of all-cause revision (HR=0.3) and the adjusted risk of aseptic revision
(HR=0.3) were lower for the APT cohort than for the
MBT group. Overall, APT TKA patients had a 49%
lower risk of early all-cause revision and a 41% lower
risk of aseptic revision compared to MBT (Mohan etal.
2013). Furthermore, the risk of early revision for any
causes was even lower in younger patients (p<0.01).
Why I Do Not Use It Anymore
z
Despite the widespread literature on APT longevity and
survivorship, the senior author is no longer a routine
utilizer of APT components. As implant MBT design
has improved polyethylene manufacturing and tibial
locking mechanism over the past decade, MBT disadvantages have been signicantly mitigated. Although
APT is signicantly more cost-effective, this cost may be
offset by overall improved workow efciency with
decreased number of implant trays, especially at higher
volume centers. Additionally, in most communities APT
does not represent a standard of care. The comfort of
modularity is here to stay and has similarly demonstrated long-term viability and success.
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Take-Home Messages
5 The utilization of APT components in TKA
has clear advantages, especially in patients
with correctable deformity with minimal
tibial bone loss.
5 APT avoids locking mechanism problems
and backside wear unique with MBT
implants.
5 Although APT-conforming geometric
designs have substantially improved over
the past decade to minimize liftoff and
edge-loading, the basic tenet of a at perpendicular tibial cut and overall limb
mechanical alignment is of utmost importance.
5 We recommend cementing the femoral com-
ponent rst as cementing the tibia initially
is likely to obscure visualization and does
not allow for proper removal of excess
cement from the posterior portion of the
femoral component. This is especially
important when using posterior stabilized
implants since the post of the APT may prevent femoral component seating. Surgeons
newer to this technique may consider using
separate bags of cement for the femur and
tibia to ensure appropriate component
alignment without liftoff.
5 APT implants have been shown to have sub-
stantial cost-saving implications with some
studies demonstrating 20–50% lower costs
versus MBT. APT offers signicant cost
reduction of up to $725 USD per case and
even greater savings cumulatively.
5 The lack of modularity for APT limits
intraoperative and postoperative options
that require simple polyethylene insert
exchange or increased constraint.
5 APT is shown to have excellent functional
clinical outcomes and long-term survivorship among varying age groups and BMI
compared to MBT.
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199908000- 00019
Cementless Total Knee
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Arthroplasty
BradleyA.King andArthurL.Malkani
Contents
32.1 Introduction – 366
32.2 Cementless TKA Designs – 366
32.2.1 Early Cementless TKA Designs – 366
32.2.2
Second-Generation Cementless TKA Designs – 368
32.3 Surgical Technique – 369
32.4 Results – 371
365
32
References – 374
© 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_32
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32.1 Introduction
Cemented xation for total knee arthroplasty (TKA)
remains the gold standard for primary TKA worldwide
with a record of excellent clinical outcomes and implant
survivorship for up to 20years (Scuderi and Insall 1992;
Attar etal. 2008; Falatyn etal. 1995). Cementless TKA
designs have been present since the 1980s with variable
outcomes (Meneghini and Hanssen 2008). Early cementless implants contained aws and never gained traction
due to multiple factors such as patch porous coating,
poor polyethylene locking mechanisms, tibial screw
augmentation leading to screw track osteolysis, femoral
component fracture, and patella failures. Corrections of
these design aws, together with advances in biomaterials, have led to a new generation of cementless TKA
implants. As demonstrated in total hip arthroplasty
(THA), cementless xation is advantageous because of
intimate biologic xation, leading to long-term durable
survivorship.
Joint arthroplasty, previously performed in a more
sedentary and elderly population with end-stage osteoarthritis, continues to experience a changing demographic to include younger, more active, and obese
patients (Kurtz etal. 2007, 2009; Dalury 2016). The pro-
portion of younger patients undergoing TKA increased
between 1993 and 2006. The demand for primary TKA
in patients ages 45–54years is projected to increase by 17
times from 2006 to 2030. Patients younger than 65years
are expected to make up the majority of demand for primary or revision TKA by 2030 (Kurtz etal. 2009). The
prevalence of TKA has increased across all age groups in
the past two decades. In 2015, the estimated prevalence
of patients living with a TKA in the United States was
0.68% at 50years, 2.92% at 60years, 7.29% at 70years,
10.38% at 80 years, and 8.48% at 90 years (Maradit
Kremers etal. 2015). Increased life expectancy, together
with this increasing prevalence of TKA, means more
patients are living longer with knee implants, therefore
placing increased stress at the bone–cement–implant
interface.
Obesity continues to be a major problem in the United
States. The combined number of patients undergoing
TKA categorized as obese or morbidly obese (BMI ≥30)
increased signicantly from 1990 to 2005 from 42% to
60%. Obese patients make up a disproportionately large
proportion of TKA patients, as the nationwide prevalence of obesity in 2005 was 32% (compared to 60% of
TKA population) (Fehring et al. 2007). By 2030, it is
estimated that 87% of adults in the United States will be
either overweight or obese (Wang etal. 2008).
Aseptic loosening is the one of the most common
reasons for revision TKA. The cement–bone interface
has been shown to attenuate over time (Miller et al.
2014). Studying a series of postmortem retrieved knee
implants, it was found that implants with greater time
in service had less interlock at the cement–bone interface, demonstrated by resorption of the trabeculae in
the cement interlock region (Miller etal. 2014; Sharkey
etal. 2014).
> Younger patients with active lifestyles and obese
patients pose a challenge to cemented TKA due to
greater amounts of stress on the cement–bone interface.
Cement has poor resistance to shear and tension forces
that are present in greater amounts at this interface in
larger or active patients (Lewis 1997; Harrysson etal.
2004). Abdel et al. (2015) demonstrated that patients
with a BMI> 35 experienced a two times greater risk
of revision with cemented implants due to aseptic tibial loosening compared to patients with a BMI< 35,
regardless of age or coronal alignment. Patients experiencing aseptic loosening of the tibia in their study were
statistically younger. Meehan etal. (2014) demonstrated
that the risk of revision surgery due to aseptic loosening
in cemented primary TKA at 1year postoperatively in
patients <50years old was 4.7 times greater than that of
a >65-year-old cohort.
> Long-term component xation remains a concern in
the obese and younger population.
32.2 Cementless TKA Designs
Given the current and anticipated demand for TKA
by younger and heavier patients, there is an emphasis
on improving the reliability and survivorship of joint
replacements. With the past success of cementless THA,
there has been an increased interest in the use of cementless TKA to provide biologic xation over mechanical
cement xation for long-term durability. However, given
the failure rates of rst-generation cementless TKA, a
cautious approach is needed in proceeding with neweror second-generation cementless TKA designs.
32.2.1 Early Cementless TKA Designs
> The rst generation of cementless TKA designs in the
1980s had limited acceptance due to xation and
design aws leading to high failure and poor clinical
outcomes.
Early cementless implants had multiple design aws
including the following
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32
5 Patch porous coating
5 Poor polyethylene locking mechanisms
5 Tibial screw augmentation leading to screw track
osteolysis
5 Femoral component fracture
5 Patella failures
Additionally, these rst-generation design implants did
not provide adequate mechanical xation for immediate
implant stability (Meneghini and Hanssen 2008; Cherian etal. 2014; Berger etal. 2001).
Tibial component xation in early designs was inconsistent and had issues with initial xation. Dunbar etal.
(2009) used radiostereometric analysis to demonstrate
that immediate rigid implant stability is essential for
long-term biological xation in cementless TKA.Early
designs did not attain adequate initial mechanical xation to allow for bony ingrowth due to multiple reasons, in addition to issues with liftoff and subsidence
(Matassi etal. 2014). These rst-generation designs had
an increased incidence of progressive radiolucent lines
at the implant–bone interface leading to aseptic loosening (Rand 1991; Rosenberg etal. 1990). Stems or screws
were added to enhance initial xation to allow for osseointegration. These screw tracks created an access channel into the tibial metaphysis for debris. Together with
rst-generation polyethylene and a poor polyethylene
liner locking mechanism, particulate debris caused osteolysis along the screw track (. Fig.32.1). The incidence
of screw track osteolysis was reported to be greater
than 30% in some cementless tibial component designs
(Lewis etal. 1995; Peters Jr etal. 1992). Holloway etal.
(2010) showed reliable xation with screwless cementless tibial baseplates at an average of 7.6years follow-up.
Other studies have also demonstrated no advantage to
using tibial baseplate with or without screws (Ferguson
etal. 2008; Schepers et al. 2012; Ritter and Meneghini
2010). Another cause of metaphyseal osteolysis and
loosening was baseplates with a patch porous coating,
which created access channels that allowed particulate
debris to spread into the metaphysis (Whiteside 1995).
Subsequent designs had a circumferential and fully
porous-coated surface to prevent this problem.
Early patellar failures were due to both awed design
and surgical technique. Femoral components had a nonanatomic trochlea (Varadarajan etal. 2011). Less atten-
. Fig. 32.1 AP and lateral radiographs of rst-generation cementless TKA with polyethylene wear and osteolysis along the screw track in
the tibial metaphysis
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tion was given to femoral component rotation leading
to malalignment and wear (Ritter and Meneghini 2010).
The use of rst-generation polyethylene along with a
metal-backed patella also accelerated polyethylene wear
leading to metal-on-metal articulation with the femoral component and eventual metallosis (Berger et al.
2001; Ritter and Meneghini 2010). Failure of the metal-
backed patella was the most common mode of failure
of early cementless TKA designs due to polyethylene
wear, failure of ingrowth, and dissociation of the metal
and polyethylene components (Rosenberg et al. 1988;
Lombardi Jr etal. 1988).
While early designs of cementless tibial and patellar
implants had concerns, early design cementless femoral
components fared well. The femoral implant attains its
initial mechanical stability through the multiplanar bone
cut providing initial stability for bony ingrowth. Some
early design cementless femoral components did fail
due to fatigue fracture at weak points along the implant
(Whiteside etal. 1993). Early femoral components, both
cemented and cementless, were not designed to optimize
patellar tracking, which contributed to patella polyethylene wear and metal-backed patellar component failure.
Despite design aws and problems with the metalbacked patella, there were successes with femoral and
tibial xation. In a review of primary cementless TKA
with the Miller-Galante 1 system (Zimmer, Warsaw, IN)
at an average of 11years follow-up, Berger etal. (2001)
reported mixed results: cementless femoral xation was
excellent, whereas 48% of metal-backed patellar components were revised. These patellar component failures led to a 12% femoral revision rate due to femoral
component damage. None of the femoral components
were loose and none had radiolucency. Cementless tibial
xation had a 9% aseptic loosening rate and 12% of the
well-xed tibial components had small osteolytic lesions
develop. Using aseptic loosening as the end point, the
10-year survivorship was 90.7% for the patellar component, 100% for the femoral component, and 94.3% for
the tibial component.
Ritter and Meneghini (2010) reviewed 73 cementless
knees from 1984 to 1986 and demonstrated that many
of the early cases of cementless TKA failures were due
to the metal-backed patella. Twelve of the 15 failures
leading to revision in their series were due to patellar
component failure with an overall 76.4% survivorship at
20years. The survivorship of the cementless tibial and
femoral components was 96.8%.
Bassett (1998) reviewed 1000 consecutive primary TKA using the Performance prosthesis (Biomet/
Kirschner, Warsaw, IN) from 1988–1993. Of these, 584
cases had cementless femoral and tibial components. All
had a cemented all-polyethylene patella. At an average
. Table 32.1 First-generation cementless TKA survivor-
ship studies
Research group Length of
follow-up
(years)
Whiteside (
Hofmann etal.
(
2001)
Schroder etal.
(
2001)
Khaw etal.
2002)
(
Hardeman etal.
(
2006)
Watanabe etal.
(2004)
Tarkin etal.
2005)
(
Buechel Sr etal.
(
2001)
Ritter and
Meneghini (
1994) 10 94.1 Ortholoc
10 95.1 Natural
10 97.1 AGC-
10 95.6 PFC
10 97.1 Prox
13 96.7 Osteon-
17 97.9 LCS-RP
18 98.3 LCS-RP
20 98.6 AGC
2010)
Survivorship (%)
Design
2000
ics
of 5.2-year follow-up, the implant survival rate in the
cementless group was 99%, with slightly higher subjective and functional knee scores for cementless knees
compared to knees with cemented components. There
were a number of early cementless TKA designs that
were able to achieve successful long-term results similar to cemented TKA with 10-year survival rates greater
than 94% (. Table 32.1) (Ritter and Meneghini 2010;
Whiteside 1994; Hofmann et al. 2001; Schroder et al.
2001; Khaw etal. 2002; Hardeman etal. 2006; Watanabe
etal. 2004; Tarkin etal. 2005; Buechel Sr etal. 2001).
32.2.2 Second-Generation Cementless TKA
Designs
> Lessons learned from early cementless TKA design
aws, together with advances in biomaterials and
manufacturing processes, have led to the creation of a
second generation of cementless TKA implants.
The emergence of new biomaterials, such as hydroxyapatite (Soballe etal. 1991a, b, 1992), porous tantalum
(Bobyn et al. 1999; Cohen 2002; Zhang et al. 1999),
and highly porous titanium (Frenkel etal. 2004), and
advanced manufacturing techniques have led to implants
with improved ability to achieve early mechanical stabil-
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