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A. Takahashi
a b
30°
45°
45°
45°
. Fig. 21.12 Patient positioning for the Merchant a and modied weight-bearing b axial views (Baldini etal. 2007)
Strategies for Anterior Knee Pain Reduction in
Primary TKA
5 Preventing axial malrotation of the components
via detailed preoperative planning
5 Proper cementing technique when resurfacing
5 Firm capsular closure particularly around MPFL
5 Rheumatoid arthritis: patellar resurfacing with lat-
eral facetectomy
5 Degenerative arthritis when using components
with the deep trochlea (Takahashi et al.
patellar retention with patelloplasty
5 Degenerative arthritis when using components
with a shallow trochlea:
– Patellar facet angle (Takahashi et al. 2012)
≥133° (at patella): patellar retention with
patelloplasty
– Patellar facet angle <133° (projecting
patella):patellar resurfacing with lateral facetectomy
2012):
Take-Home Messages
5 The use of patellar resurfacing versus reten-
tion in TKA has long been a controversy since
there are signicant variations in the rates of
patellar resurfacing among countries, whether
it should be performed remains unclear.
5 Patellar retention is advantageous as it is less
invasive to the extensor mechanism, can preserve the bone, and has a shorter operative
time. However, patellar retention has disadvantages, which include anterior knee pain
and a high rate of revision surgery for patellofemoral joint fracture.
5 High-contact pressure in the patellofemoral
joint causes postoperative anterior knee pain.
5 Axial malrotation of the components could
cause patellofemoral high-contact pressure;
thus, this should be avoided via detailed preoperative planning.
21
Patella Replacement inKnee Arthroplasty: AJapanese Perspective
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5 Steep facet angle and component trochlea
are associated with patellofemoral highcontact stress. Hence, they could be indicators for selective patellar resurfacing.
5 Lateral patellar facet impingement after
TKA could be treated with lateral facetectomy, with relatively good outcomes.
5 Successful repair of the MPFL after using
the medial parapatellar approach in TKA
could reduce the incidence of anterior knee
pain.
5 When resurfacing the patella with cement
xation, multiple small anchor holes are necessary only when the patella is eburnated.
The bone surface should be dried before
starting cement xation. Moreover, cement
must be placed on both the implant and bony
surfaces, and compression force should be
applied until cement polymerization is completed.
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Knee Arthroplasty: AnAsian
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Perspective
WilsonWang, BryanT.H.Koh, andVikaeshMoorthy
Contents
22.1 Introduction – 246
22.1.1 Demographics ofKnee OA inWestern Versus
Asian Populations – 246
22.1.2 TKA inWestern Versus Asian Countries – 246
22.1.3
Predictors ofKnee OA andKnee Arthroplasty – 247
Unicompartmental andPatellofemoral Arthroplasty – 247
22.1.4
22.2 Ethnic Dierences inKnee Morphology – 248
22.2.1 Asian Versus Western Knee Anatomy – 248
22.2.2 Lower Extremity Axial Alignment inAsian Versus
Caucasian Adults – 249
22.2.3 Dierences inDistal Femoral Morphology – 249
22.2.4 Dierences inProximal Tibial Morphology – 250
22.2.5 Dierences inPatella Morphology andOthers – 251
245
22
22.3 Prevailing Knee Arthroplasty Techniques – 251
22.3.1 Special Considerations inAsian Knee Arthroplasty – 251
22.3.2 UKA Utility inAsia – 254
22.4 Cementless TKA – 254
22.4.1 Background ofCementless TKA – 254
22.4.2 Cementless Versus Cemented TKA – 255
22.5 Patellofemoral Arthroplasty andBackground
andUtility ofPatellar Resurfacing – 256
References – 257
© 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_22
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22.1 Introduction
22.1.1 Demographics ofKnee OA
inWestern Versus Asian Populations
Knee osteoarthritis (OA) is the most common joint disorder affecting the elderly throughout the world. It is the
leading cause of disability stemming from chronic pain
and immobility with an incredible impact on public
health (Kim et al. 2008). The downstream effects of
knee OA include reduced quality of life from an individual’s and caregiver’s perspective (Fransen etal. 2011)
to increased healthcare cost and reduced productivity.
Total knee arthroplasty (TKA) is known to be the most
effective intervention for advanced-stage knee OA for
pain control and functional improvement (Lin et al.
2018).
Knee OA occurs in 12% of American adults aged
65years or older, and in 13% of women and 10% of men
60years or older in the United States (Kim etal. 2008;
Lin et al. 2018; Zhang et al. 2001). The prevalence of
knee OA for females in East Asian countries has been
reported to be higher than the equivalent prevalence for
females reported in the US Caucasian population, while
for males the gure is slightly lower comparatively (Kim
et al. 2008; Zhang etal. 2001). In one report (Beijing
Osteoarthritis Study), the prevalence of knee OA was
found to be 15% in women and 5.6% in men aged
60 years or older in Beijing, China, and that among
those over 50years old in Taiwan was about 37% (Zhang
etal. 2001). A population-based epidemiological study
conducted in Vietnam, which involved 170 men and 488
women over 40years of age also found that 31% of men
and 35% of women had radiographic OA of the knee
(Ho-Pham etal. 2014). As such the prevalence of knee
OA in Asia is comparable with Caucasian populations
(Nguyen 2014).
In 2012, OA affected 27% of the population aged
over 45years in industrialized countries and this rate is
expected to increase by 11% by 2032 when an additional
26,000 individuals per one million population will be
affected (Pabinger et al. 2015). Among these patients,
the highest incidence of OA is found in the knee joint,
which is affected twice as often as the hip joint. This is
especially the case in Asia where people have the habit
of squatting or sitting on the oor, and it has been postulated that squatting may in fact protect against OA of
the hip (Nguyen 2014). It is estimated that 6% of those
aged 30years and older and 15% of those aged 45years
and older experience knee OA, with a lifetime risk of
45% (Murphy etal. 2008). In view of these trends, it is
unsurprising that the need for TKAs is also expected to
grow exponentially in the coming years (Pabinger etal.
2015).
22.1.2 TKA inWestern Versus Asian
Countries
TKA is one of the most successful clinical interventions
for patients with debilitating hip and knee diseases
(Kumar etal. 2015) and is currently the international
standard of care for treating degenerative and rheumatologic knee disorders (Kurtz etal. 2011). TKA is the
treatment of choice in the most severe forms of knee OA
and has even been described as a surrogate marker of
severe OA (Jonsson etal. 2016). Previous studies of knee
replacement have shown substantial improvements in
patients’ health-related quality of life (HRQoL) scores
after the surgery, especially in terms of the pain dimension (Ko etal. 2011), suggesting high utility and benet
of TKA as the treatment of choice for severe knee OA.
Given that both population aging and economic
growth have taken place at a fast pace in many Asian
countries, it is expected that knee OA will become a
major public health problem and that utilization of
TKA will increase in many Asian countries as well,
where over 60% of the world population lives (Kim etal.
2008; Ko etal. 2011). Apart from aging, there is much
evidence from mostly Western cohorts that obesity or
heavy-occupational physical activity, such as that carried out by many people in rural communities in Asia,
are clear risk factors for symptomatic knee OA (Fransen
etal. 2011). These further support the view of a rapidly
rising rate of TKAs across Asia in the coming years.
In fact, primary TKA rates have increased by 407%
in South Korea from 2001 to 2010, according to data
from the Health Insurance Review Agency (HIRA)
from South Korea (Koh et al. 2013). Also using the
national data collected by HIRA in South Korea, Kim
etal. (2008) found that from 2002 to 2005, 103,601 TKA
surgeries were performed in South Korea, with the rate
of TKA increasing over the years from 2002 to 2005 and
being signicantly higher in women than in men.
Likewise, in Taiwan, a retrospective study by Lin etal.
(2018) using Taiwan’s National Health Insurance
Research Database, showed that 154,553 TKA surgeries
were performed in Taiwan during the 15-year study
period from 1996 to 2010, with the number of TKAs
increasing from 5303 in 1996 to 17,368 in 2010 (an
increase of 202.56%), while the rate of TKAs tripled,
from 24.64 to 74.55 per 100,000 between 1996 and 2010.
This trend of a rapid increase in the rate of TKAs in
recent years is expected to continue in Asia, in view of
the aforementioned factors.
Most studies to date have also reported that satisfaction following TKA is high. Mahomed et al. (2011)
evaluated 857 patients 1 year following TKA and
reported an overall satisfaction score of 88%. A study
on 25,275 patients from the Swedish Joint Arthroplasty
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247
22
Registry showed a satisfaction score of 81% (Dunbar
2001). While these gures have to be quoted from stud-
ies performed on a predominantly Western population,
there are no large-scale studies that have evaluated satisfaction rates on Asian patients undergoing TKA.
> However, of note, TKA in Asian populations involves
a few unique challenges, especially that of higher
demands of postoperative exion among Asians (Bin
AbdRazak and Yeo 2015).
As such, further improving patient satisfaction following TKA is certainly a challenge, especially in the Asian
context. In fact, Thambiah etal. (2015) also concluded
that although there was a high level of patient satisfaction (92.8%) following TKA in their cohort of 103 Asian
patients in Singapore, a signicant minority was dissatised, likely due to reasons of patient expectations and
inadequate postoperative exion as deemed by the
patients.
22.1.3 Predictors ofKnee OA andKnee
Arthroplasty
Risk factors for knee OA have been studied mostly in
Caucasian populations residing in high-income countries and include age, female gender, obesity, a history of
knee surgery or signicant trauma, or having an occupation requiring heavy lifting, kneeling, or squatting
(Jensen 2008). Less epidemiological research in chronic
musculoskeletal conditions has been conducted in countries in Asia (Fransen etal. 2011).
individuals with end-stage knee OA.Logistic regression
revealed that age, Knee Outcome Survey–Activities of
Daily Living Subscale (KOS-ADLS), Timed Up and Go
(TUG), Stair Climbing Task (SCT), quadriceps strength,
and knee extension range of motion (ROM) signicantly predicted TKA within 2 years (p ≤ 0.001,
R2 = 0.412). Conversely, younger age, higher KOS-
ADLS scores, faster TUG and SCT times, stronger
quadriceps, and full knee extension predicted those who
do not undergo TKA.Using backward regression, age,
knee extension ROM and KOS-ADLS together signicantly predicted whether or not a person would undergo
TKA (p≤0.001, R2=0.403).
Lin etal. (2018) also identied year, female gender,
increased age, and OA as key risk factors and predictors
of TKA.The relative risk ratio (RR) was as follows:
5 1.09 (95% CI: 1.08–1.09) per year
5 1.66 (95% CI:1.63–1.69) for females compared with
males
5 5.45 (95% CI: 5.16–5.75) for the 50 to 59 age group
5 15.21 (95% CI: 14.45–16.00) for the 60 to 69 age
group
5 21.23 (95% CI: 20.17–22.34) for the 70 to 79 age
group
5 16.24 (95% CI: 15.30–17.25) for the ≥80 age group,
when compared with the <50 age group
Patients with rheumatoid arthritis (RA) and avascular necrosis (AVN) as their primary diagnoses were also
found to have a lower risk for TKA (RR=0.15, 95%
CI:15.30–17.25 and RR = 0.007, 95% CI:15.30–17.25,
respectively) than those with OA.
> While it is reasonable to extend some of these risk
factor ndings to Asian countries, there are also likely
to be a signicant demographic, cultural, lifestyle,
and environmental differences inuencing the onset
and progression of knee OA in Asian populations.
Kim etal. (2008) have suggested that both kneeling and
squatting are strong risk factors for knee OA, and this
lifestyle factor might account for greater functional disability as well as the prevalence of knee OA in Asians
due to greater use of the squatting posture by Asians in
daily activities, such as toileting. Compared with Western countries in which stability for walking is important,
in Asian countries, knee exion for squatting and kneeling may be more important in the decision to undergo
surgery, accounting for the increase of OA and TKA
rates among Asians.
Using functional data from 120 persons with endstage knee OA, Zeni Jr. etal. (2010) determined clinical
factors which predict the decision to undergo TKA in
22.1.4 Unicompartmental
andPatellofemoral Arthroplasty
Apart from TKA, current surgical treatments for knee
OA patients also include unicompartmental knee
arthroplasty (UKA). Previous studies have shown that
TKA and UKA are both safe and effective (Callahan
etal. 1994, 1995). Although UKA is effective in patients
with knee OA restricted to a single compartment, TKA
is generally recommended for patients with more extensive knee OA (Zhang etal. 2008). Of note, in comparison to TKA, UKA has the additional benets of lower
costs, shorter hospitalization, less invasiveness, quicker
rehabilitation, and a potentially better cost-effectiveness
prole (Ko etal. 2011; Slover etal. 2006).
More recent studies on US patients suggest that
12–26% of patients might qualify for UKA according to
the Kozinn and Scott criteria (Woolson etal. 2010). In
contrast, He etal. (2018) suggest that a smaller percentage of Chinese patients undergoing knee arthroplasty
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22
are candidates for UKA: Of the 300 knees with OA that
were studied, they found that 241 knees were excluded
from UKA because of the extent of deformity (n=156),
decreased range of motion (n=119), advanced patellofemoral arthritis with bone loss (n=11), and AP instability (n=1). Of the remaining 63 knees, only 54 knees
(18%) met the modied Oxford criteria for mobile UKA
and only 25 knees (8%) met the Kozinn and Scott criteria for xed UKA.
> The authors concluded that in comparison to
Caucasian population only a smaller percentage of
patients in a Chinese cohort meet the UKA indication
criteria and therefore propose that it might make
more sense to concentrate UKA surgeries in high volume centers for predominantly Asian communities.
The patellofemoral (PF) joint is the most incongruent
joint in the body and problems of the PF joint in Asian
populations are distinct enough from the tibiofemoral
joint to warrant separate attention, including patellofemoral osteoarthritis (PFOA), which occurs due to the
loss of cartilage of the patella and the trochlear groove
of the femur.
A high prevalence of PFOA has been observed in
studies conducted in the Middle East and Asia, whereas
lower prevalence rates were reported in Estonia and
Sweden (Kobayashi etal. 2016; Wise etal. 2012). These
ndings were consistent with Pereira et al. (2011) who
found that studies conducted in Europe, particularly
Northern Europe, reported a lower prevalence of
PFOA.A previous study by Muraki etal. (2009) has
also suggested that the culture of kneeling, particularly
in Asian countries, could lead to a higher prevalence of
knee OA.However, there has been no conclusive evidence to suggest any cultural link with PFOA.In fact,
conicting evidence has suggested that the increased
contact area between the patella and femoral trochlear
during kneeling could be a protective mechanism from
developing patellofemoral OA (Rytter etal. 2009).
Certain genes have also been reported to have high
associations with knee OA in some ethnic populations
but not others. For instance, variants in the expression
of genes responsible for cartilage and bone growth (such
as DVWA, DQB1, and BTNL2) have been shown to
increase the risk of developing knee OA in Asian cohorts
(Japanese, Chinese and Korean), but not in European
cohorts (Valdes and Spector 2011). Therefore, it is reasonable to believe that ethnic groups have different
genetic predispositions for developing OA, accounting
for the geographic variability of PFOA.It has also been
suggested that identication of individuals at a high risk
of OA and of TKA failure might be facilitated by the
use of combinations of such genetic markers, allowing
for the application of preventive and disease management strategies in knee OA and TKAs (Valdes and
Spector 2011).
22.2 Ethnic Dierences inKnee Morphology
22.2.1 Asian Versus Western Knee Anatomy
TKA is a precise procedure, requiring accurate softtissue balancing and resection of bone thickness equal
to the thickness of the implanted prosthetic component.
A properly shaped prosthesis can provide the best coverage and avoid soft-tissue impingement. Therefore, TKA
prostheses based on accurate morphologic data of the
knee, taking into account morphologic differences
between gender and ethnicity would give better surgical
and postoperative results (Hosseinzadeh etal. 2013).
> Recent anthropometric studies have suggested that
the current design of TKA prostheses does not fully
cater to racial anthropometric differences and that
most of the commercially available TKA prostheses
are designed according to the anthropometric data of
Caucasian knees.
This has been suspected as the cause of the component
mismatch in Asian patients (Yue etal. 2011).
Iorio etal. (2007) showed that Japanese patients had
a signicantly lower postoperative ROM than Caucasian
patients after TKA and that 4.1% of Japanese patients
required revision after primary posterior cruciateretaining TKA within an average follow-up of 6.6years,
whereas only 2.6% of their American counterparts
needed revision within an average follow-up of 9years.
The authors suggested that the racial morphologic differences in knee anatomy and resultant component mismatch might be a key contributing factor, causing this
signicant difference in outcomes (Hosseinzadeh etal.
2013).
Studies have also shown that the dimensions of
Chinese knees are generally smaller than Caucasian
knees, with Chinese females having a signicantly narrower distal femur than Caucasian females, and Chinese
males having a wider proximal tibia than their Caucasian
counterparts. Morphological measurements of Chinese
knees have also shown that both Chinese males and
females have smaller femoral aspect ratio (mediolateral
[fML]/anteroposterior [fAP]) dimensions than their
Caucasian counterparts (Hosseinzadeh etal. 2013; Yue
etal. 2011; Mahfouz etal. 2012).
The ndings on TKA component mismatch have led
some researchers to suggest that Asians should have special designs of the TKA prosthesis system (Yue etal.
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22
2011). With the higher prevalence of knee OA and lower
preoperative knee function in Asian populations than
Caucasian populations (Zhang etal. 2001; Inoue etal.
2001; Joshy etal. 2006) and the increasing use of TKA
in Asia,(Kim et al. 2008) it has become essential to
understand the differences in knee morphology and
anatomy between Asian and Caucasian populations, so
as to improve TKA prostheses and the outcomes of
TKA in Asians.
22.2.2 Lower Extremity Axial Alignment
inAsian Versus Caucasian Adults
Achieving normal axial alignment of the lower extremity is important to surgeons who perform reconstructive
surgery of the knee. The normal alignment of the lower
extremity in Caucasians has been documented by
Moreland etal. (1987) with the use of radiographs of
the lower extremity and currently, there are several
known differences in the axial alignment of the lower
extremities between Asians and Caucasian populations.
The inferolateral angle between the knee joint surface and the mechanical axis of the tibia is an index of
knee joint obliquity. This angle in subjects, as reported
by Tang et al. (2005) was 95.4 ± 2.5° in women and
94.9±2.3° in men which is signicantly larger than that
in Caucasian subjects, as reported by Hsu etal. (1990)
with a mean of 91.0 ± 1.4° in Caucasian men and a
mean of 90.1±1.9° in Caucasian women.
> These ndings suggest agreater medial inclination of
the knee joint in Chinese as compared to Caucasian
people (Hosseinzadeh etal. 2013).
> According to Shao etal. (2018) East Asian individu-
als also have a more lateral tibial shaft axis than
Caucasians.
The study found that East Asian individuals had a
−9.9±2.7mm (range −16.2 to −4.6mm) offset from the
tibial shaft axis to Akagi’s line in the mediolateral direction, compared to −7.7 ± 3.1 mm (range −13.4 to
−0.3 mm) for Caucasians. However, there was no signicant difference in the femoral diaphysis offset
between the East Asian and Caucasian groups.
(0.55±0.338), while 78% of Japanese subjects exhibited
a more varus alignment (1.64±0.438). Tang etal. (2005)
also showed that the lower extremities of the Chinese
women had a mean of 2.2 ± 2.5° of varus alignment,
and those of Chinese men had a mean of 2.2±2.7° of
varus alignment, suggesting that the knees of Chinese
female subjects, were in more varus alignment than were
those in the Caucasian female subjects in the study by
Hsu etal. (1990)
The mean anatomic axis angle, condyle angle, and
condyle–plateau angle were also signicantly different
in the Beijing Osteoarthritis Study (BOA) (n = 173)
when compared with the Framingham Osteoarthritis
Study (FOA) (n = 134). Although the mean anatomic
axis angle was valgus in both cohorts, the BOA cohort
was 1.35° more valgus (p=0.01) in men and 2.01° more
valgus (p<0.001) in women, as compared to their counterparts in the FOA cohort (Harvey et al. 2008).
Considering the distribution for the anatomic axis angle
in the Framingham and Beijing subjects before adjusting for age and BMI, the difference in the mean anatomic axis was more valgus in Beijing subjects, with the
standard deviation of this measure in the Beijing subjects being larger compared with the Framingham subjects (F-test for equality of variances p<0.0001) (Harvey
etal. 2008). However, examination of the anatomic axis
is a small sample of the cohort of the Beijing and
Framingham populations did not explain the higher lateral tibiofemoral OA prevalence in Chinese and no clear
conclusions could be made (Harvey etal. 2008).
Currently, most TKA systems recommend prosthesis
placement such that the transverse axis of the articial
knee joint is perpendicular to the mechanical axes of the
tibia and the femur. This results in an alignment of the
lower extremity which is most similar to the alignment
documented by Moreland et al. and Hsu et al.
Unsurprisingly, the mechanical axes of the femur and
the tibia did not form a straight line in either Chinese
males or females (Hosseinzadeh etal. 2013).
> Further studies are required to conclusively charac-
terize the axial alignment of the lower extremities in
Asians and how it differs from that of Caucasians,
and such data need to be used to develop new and
updated guidelines and TKA prostheses systems that
better accommodate and suit the Asian knee.
> In general, existing studies have shown that the Asian
knee tends to be more varus than Caucasian knees,
although there are some discrepancies seen in the literature.
Hovinga and Lerner (2009)) found that the mechanical
alignment in Caucasians was slightly varus in 57%
22.2.3 Dierences inDistal Femoral
Morphology
Recent studies have suggested that the current design of
total knee arthroplasty does not cater to racial anthropometric differences, causing a component mismatch in
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W. Wang et al.
22
Asian patients,(Yue etal. 2011) due to poor t and compatibility of the femoral component of the prosthesis
for the Asian knee. Ho etal. (2006) found that three of
ve TKA systems used in China tended to overhang
across the mediolateral width of resected femurs from
Chinese patients. Cheng etal. (2009) also found that the
femoral component overhang was more obvious in
Chinese females than males and suggested that the prostheses that were designed for Caucasian patients may be
too large for Chinese patients,(Yue et al. 2011) due to
morphological differences between the Chinese and
Caucasian knee. Thus, it is crucial to characterize the
distal femoral morphology and differences in this morphology between Asian and Western populations.
The mediolateral (fML) and anteroposterior (fAP)
size of the femur, measured using a viewing plane set
perpendicular to the femoral long axis have revealed signicant differences in the dimensions and morphology
of Asian versus Caucasian knees. Several studies (Ho
etal. 2006; Cheng et al. 2009; Urabe et al. 2008) have
compared the morphology of Asian knees to that of
TKA prostheses currently used in Asia and found that
the general size and femoral aspect ratio (mediolateral
[fML]/anteroposterior [fAP]) of these prostheses were
not suitable for Asian patients.
> In general, the femoral volume of East Asians
(466.5±95.0cm
Caucasians (540.2±117.3cm
3
) is signicantly smaller than that of
3
) (Shao etal. 2018).
The height-adjusted ratios of the half metaphyseal
femur (p < 0.001), the whole condyle (p = 0.03), the
anterior condyle (p<0.001), and the resected condyle
(p=0.004) have also been found to be signicantly lower
in Japanese women compared to their Caucasian counterparts. However, the height-adjusted ratio of the posterior condyle was signicantly smaller in Caucasian
women (p=0.02) (Urabe etal. 2008).
The fML dimension of Chinese females
(72.8±2.6mm; range, 70.0–79.1mm) was signicantly
smaller than that of Caucasian females (76.4±4.0mm;
range, 70.3–82mm) (P=0.002). Chinese males had an
average fML dimension of 82.6±3.6mm (range, 72.6–
87.1mm), which was signicantly smaller than that of
Caucasian males (86.0±5.6mm; range, 74.9–100.2mm)
(P=0.028) (Yue etal. 2011).
Chinese females also had a signicantly smaller average fML/fAP ratio than Caucasian females
(1.239 ± 0.042 vs. 1.286± 0.063). While a progressive
decline in the fML/fAP ratio with increasing fAP dimension was noted for both races, there was a distinct offset
between the corresponding regression lines for Chinese
and Caucasian knees, indicating that Chinese females
had a smaller fML/fAP ratio than Caucasian females
for the same fAP dimension. Thus, the differences in
average values of femoral aspect ratio between Chinese
and Caucasian females cannot be explained by differences in knee size alone, and this may point to a distinct
variation in femoral shape between the two races (Yue
etal. 2011).
22.2.4 Dierences inProximal Tibial
Morphology
In general, the tibial volume of East Asians
(293.1 ± 61.1 cm3) has been found to be smaller than
that of Caucasians (327.0±74.7cm3) (Shao etal. 2018).
The tibial dimension of Chinese males is generally
smaller than that of Caucasian males and measurements
of tibia have also shown that the tibial size of Chinese
females is generally smaller than that of Caucasian
females (Yue etal. 2011).
A signicant difference has been noted for the tibial
aspect ratio, with that of Chinese males being signicantly larger than that of Caucasian males (1.82±0.07
vs. 1.75±0.11) (P=0.033) (Yue etal. 2011). Mahfouz
et al. (2012) also found that East Asian males had a
smaller tibial mediolateral/tibial anteroposterior (tML/
tAP) ratio than Caucasian males (1.33 ± 0.12 vs.
1.4±0.06), with normalized ratios and nonlinear shape
analysis in support of differences between East Asians
and Caucasians independent of any scale factor.
Based on the study by Hovinga and Lerner (2009) a
lower tibial torsion was also found in Japanese as compared to Caucasian populations. The average torsion
angle was 37.58° for all subjects and showed signicant
differences with ethnicity (p < 0.01) with Caucasians
demonstrating a higher torsion angle than Japanese
(Hovinga and Lerner 2009). Tamari et al. (2006) also
found that the Japanese patients had signicantly greater
femoral torsion angles (FTA) and femoral antetorsion
than Australian Caucasians, more so in females than
males and more so in the younger than older age group.
The coronal tibial slope, which measures the mediolateral slope of the tibial plateau, has recently been
appreciated as a factor associated with accelerated
development of knee OA, in a study based on follow-up
of 4796 individuals of both genders from ages 45 to
79in the Osteoarthritis Initiative (OAI), a longitudinal
observational study of adults with or at risk for knee
osteoarthritis at four clinical sites in the United States
[Driban] (Driban etal. 2016). The study showed that the
coronal slope ranged from 3.0° valgus to 9.0° varus, and
a greater varus coronal slope was associated with an
increased risk of incident accelerated knee osteoarthritis
(OR=1.15, 95% CI=1.01 to 1.32), and that for every
degree of increase in varus coronal slope, the odds of
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251
22
developing accelerated knee osteoarthritis increased by
15%. This study did not discuss racial differences in their
ndings, but the increased incidence in Asian populations may be hypothesized from other related alignment
reports,(Hosseinzadeh etal. 2013; Tang etal. 2005; Hsu
etal. 1990) and this feature is a frequent nding in the
authors’ clinical experience (. Fig.22.1).
22.2.5 Dierences inPatella Morphology
andOthers
Little work has been done comparing the anthropometric patella morphology of Asians to that of Caucasians.
However, unsurprisingly, in line with the differences in
the tibial and femoral dimensions, current studies show
that the patella of Asians is generally smaller than that
of their Western counterparts.
Kim et al. (2016) found that in Koreans, mean
heights and widths of the patella were smaller than corresponding measurements in Westerners for both men
(36.2mm and 45.6mm vs. 39.4mm and 49.5mm) and
women (33.1 mm and 41.0 mm vs. 35.0 mm and
42.7 mm). However, the width/height ratios and ridge
positions were similar in both Koreans and Westerners.
Koreans were also found to have thinner patellae than
Westerners. The mean central ridge thickness was
21.2mm (range 17 to 26mm) in women and 23.1mm
(range 20 to 26 mm) in men, whereas corresponding
reported mean thicknesses in Western patients were 21.8
to 22.5mm and 23.9 to 26.1mm.
The general principle of resecting patellar bone
equivalent to the height of the patellar button (usually
around 8 to 9mm) means that the thinner the patella,
the less the residual bone thickness. This measurement is
of signicance in TKA as thinner patellae are less amenable to patellar resurfacing, particularly if the resected
residual thickness is 11mm or less, which may entail a
fracture risk (Kim 2013). Thinner patellae of less than
21 mm preoperatively or less than 12mm of residual
thickness after resurfacing seem to be associated with
less satisfactory results and ROM, even without patellar
fracture or implant loosening (Chung etal. 2015).
patellar resurfacing components have been adopted
recently to address the problems of resurfacing thin
patellae and these may be of benet in Asian TKAs,(Ha
and Na 2012) but longer term results regarding tribology and long-term survivorship are awaited
(. Fig.22.2).
Hovinga et al. also found higher ACL laxity in
Japanese compared to Caucasian populations (Hovinga
and Lerner 2009). ACL laxity measurement for
Caucasian females was 6.4±0.36mm (n=22), and for
males was 4.9±0.35mm (n=20). For Japanese females,
the laxity was 8.1± 0.65mm (n = 12), and for males
6.9 ± 0.56 mm (n = 11). Signicant differences were
found for both gender (p = 0.003) and ethnicity
(p=0.0002) (Hovinga and Lerner 2009).
Concluding Remarks
z
Almost all prosthetic implants have been designed and
manufactured to accommodate the knee anatomy of
Caucasians, and there is some doubt about the application of these TKA prostheses systems in Asians, as even
the smallest size from each Western prosthesis company
may be too big for some Asian patients.
Beyond the mere size, as reviewed in the above paragraphs, there are many differences in various anatomic
parameters between Asian and Caucasian knees, affecting the t of current prostheses in Asian knees.
As such, it is clearly necessary to have specically
designed TKA prostheses systems for Asian populations, accommodating not only the smaller Asian knee
but also the variations in aspect ratios and size parameters. Another consideration in Asian knee prostheses is
their need for more exion than their western counterparts, given the differences in cultural and lifestyle factors necessitating greater exions in Asians for
functionality and operative satisfaction. As such, achieving deep exion after TKA, although not as important
as the technical consideration, is also a signicant point
to consider in prosthesis design.
22.3 Prevailing Knee Arthroplasty
Techniques
> Thin patellae may be overlooked in preoperative
radiographs due to variable and often increased magnications in patellar views, and in Asian knees, patellar thickness should always be measured carefully
before any step towards patellar resurfacing.
In our experience, native patellae of 14 to 15mm thickness have been encountered in Asian female patients
which are not amenable to current patellar resurfacing
techniques (. Fig. 22.2). Strategies to develop thinner
22.3.1 Special Considerations inAsian
Knee Arthroplasty
Generally, the strategies currently used to manage joint
deformities in Asian patients are similar to those used
when treating other ethnic groups (Kim et al. 2016).
Some experts believe that any type of Western- or Asianmanufactured TKA prosthesis system can accommodate subtle differences in anthropometric knee anatomy
between Asians and Westerners, regardless of differ-
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