Distal femur rotation relates to joint obliquity in ACL-deficient Chinese


Yau, W.P.; Chiu, K.Y.; Fok, A.W.M.; Yan, C.H.; Ng, F.Y.

Clinical Orthopaedics and Related Research 471(5): 1458-1464

2013


The lower limb osteometry of Chinese differs from that of whites. The joint line of the knee in the coronal plane in Chinese is more medially inclined and the posterior condylar angle of the distal femur in the axial plane is larger. However, it is unclear whether there is any direct association between the coronal plane and axial plane osteometry. We asked whether the joint line obliquity of the knee is related to the posterior condylar angle of the distal femur in young Chinese subjects. Ninety-nine young Chinese patients with anterior cruciate ligament injuries were recruited. The lower limb alignment and joint line obliquity were measured using standing long radiographs of the whole lower limb. The rotational alignment of the distal femur was assessed in the axial cuts of the MRI. The distal femur rotational alignment was associated with the obliquity of the knee in Chinese. The posterior condylar angle was 5° ± 2°. The knee was 5° ± 3° medially inclined. The joint line of the knee in a group of young Chinese patients was more medially inclined than that of whites. The posterior condylar angle of the distal femur was larger. The presence of an association between distal femur rotational alignment and joint line obliquity in this group of young Chinese patients suggests a possible developmental cause explaining the difference in osteometry between races.

Clin
Orthop
Relat
Res
(2013)
471:1458-1464
DOI
10.1007/s11999-012-2698-4
Clinical
Orthopaedics
and
Related
Research
®
A
Publication
of
The
Assodation
of
Bone
and
Joint
Surgeons.
SYMPOSIUM:
SPECIAL
CONSIDERATIONS
FOR
TKA
IN
ASIAN
PATIENTS
Distal
Femur
Rotation
Relates
to
Joint
Obliquity
in
ACL-deficient
Chinese
W.
P.
Yau
MBBS,
FRCSE,
FHKCOS,
K.
Y.
Chiu
MBBS,
FRCSE,
FHKCOS,
August
W.
M.
Fok
MBChB,
FRCSE,
FHKCOS,
C.
H.
Yan
MBBS,
FRCSE,
FHKCOS,
F.
Y.
Ng
MBBS,
FRCSE,
FHKCOS
Published
online:
21
November
2012
©
The
Association
of
Bone
and
Joint
Surgeons®
2012
Abstract
Background
The
lower
limb
osteometry
of
Chinese
dif-
fers
from
that
of
whites.
The
joint
line
of
the
knee
in
the
coronal
plane
in
Chinese
is
more
medially
inclined
and
the
posterior
condylar
angle
of
the
distal
femur
in
the
axial
plane
is
larger.
However,
it
is
unclear
whether
there
is
any
direct
association
between
the
coronal
plane
and
axial
plane
osteometry.
Questions/purposes
We
asked
whether
the
joint
line
obliquity
of
the
knee
is
related
to
the
posterior
condylar
angle
of
the
distal
femur
in
young
Chinese
subjects.
Methods
Ninety-nine
young
Chinese
patients
with
ante-
rior
cruciate
ligament
injuries
were
recruited.
The
lower
limb
alignment
and
joint
line
obliquity
were
measured
using
standing
long
radiographs
of
the
whole
lower
limb.
The
rotational
alignment
of
the
distal
femur
was
assessed
in
the
axial
cuts
of
the
MRI.
Results
The
distal
femur
rotational
alignment
was
asso-
ciated
with
the
obliquity
of
the
knee
in
Chinese.
The
posterior
condylar
angle
was
±
2°.
The
knee
was
±
medially
inclined.
Conclusions
The
joint
line
of
the
knee
in
a
group
of
young
Chinese
patients
was
more
medially
inclined than
that
of
whites.
The
posterior
condylar
angle
of
the
distal
femur
was
larger.
The
presence
of
an
association
between
distal
femur
rotational
alignment
and
joint
line
obliquity
in
this
group
of
young
Chinese
patients
suggests
a
possible
developmental
cause
explaining
the
difference
in
osteom-
etry
between
races.
Introduction
Each
author
certifies
that
he
or
she,
or
a
member
of
his
or
her
immediate
family,
has
no
funding
or
commercial
associations
(eg,
consultancies,
stock
ownership,
equity
interest,
patent/licensing
arrangements,
etc)
that
might
pose
a
conflict
of
interest
in
connection
with
the
submitted
article.
All
ICMJE
Conflict
of
Interest
Forms
for
authors
and
Clinical
Orthopaedics
and
Related
Research
editors
and
board
members
are
on
file
with
the
publication
and
can
be
viewed
on
request.
Each
author
certifies
that
his
or
her
institution
approved
or
waived
approval
for
the
reporting
of
this
case
and
that
all
investigations
were
conducted
in
conformity
with
ethical
principles
of
research.
W.
P.
Yau
(El),
K.
Y.
Chiu,
C.
H.
Yan
Department
of
Orthopaedics
and
Traumatology,
The
University
of
Hong
Kong,
Queen
Mary
Hospital,
Room
508A,
Professorial
Block,
0
&
T,
No.
102,
Pokfulam
Road,
Hong
Kong,
Hong
Kong
e-mail:
A.
W.
M.
Fok,
F.
Y.
Ng
Department
of
Orthopaedics
and
Traumatology,
Queen
Mary
Hospital,
Hong
Kong,
Hong
Kong
TKA
is
one
of
the
most
commonly
performed
orthopaedic
operations.
The
success
of
TKA
depends
on
correct
implantation
of
the
prosthesis
and
proper
ligament
balance
of
the
deformed
knee
[8,
18].
Restoration
of
the
neutral
mechanical
alignment
of
the
lower
limb
in
the
coronal
plane
and
the
correct
rotational
alignment
in
the
axial
plane
are
considered
as
two
of
the
most
important
issues
during
prosthesis
implantation
[1,
2,
6,
8].
However,
it
is
well
known
that
the
osteometry
of
Asians
differs
from
that
of
Western
populations
in
both
size
and
morphology
[4,
11,
19,
20, 22,
23].
In
a
group
of
young
healthy
asymptomatic
Chinese
volunteers,
we
demon-
strated
that
the
mechanical
axis
of
the
lower
limb
in
the
coronal
plane
was
more
varus
in
the
Chinese
patients
(2.2°
varus)
and
the
joint
line
was
more
medially
inclined
(5.2°)
[16].
In
a
separate
study
of
82
embalmed
cadaveric
femurs
of
known
Chinese ethnicity
[23],
we
observed
that
the
1Springer
Joint
line
Mechanical
obliquity
axis
of
the
of
the
lower
limb
knee
Right
(SD
1.6°)
Left
2.6°
(SD
1.4°)
Male
(SD
1.4°)
Female
al°
(SD
1.9°)
5.2°
(SD
/4°)
(SD
3°)
Right
Varus
1.5°
(SD
2.0°)
Left
Varus
1.1°
(SD
2.1°)
Male
Varus
2.3°
(SD
2.3°)
Female
Varus
1.3°
(SD
1.8°)
Varus
2.2°
(SD
2.6°)
Varus
(SD
3°)
Volume
471,
Number
5,
May
2013
Posterior
Condylar
Angle
in
Chinese
1459
posterior
condylar
angle
(ie,
the
angle
between
the
surgical
epicondylar
axis
and
posterior
condylar
line
of
the
distal
femur)
was
larger.
The
average
posterior
condylar
angle
was
5.2°.
The
reported
lower
limb
alignment
and
joint
line
obliquity
in
whites
were
varus
and
medially
inclined
3°,
respectively
[7,
14].
These
values
differ
from
those
reported
for
Chinese
[20]
(Table
1).
Despite
the
observa-
tion
of
the
apparent
incidental
findings
of
comparable
average
angle
of
joint
line
obliquity
(5.2°
medial
inclina-
tion)
and
posterior
condylar
angle
(5.2°),
it
is
unclear
whether
the
joint
line
obliquity
of
the
knee
is
associated
with
the
rotational
alignment
of
the
distal
femur.
We
therefore
asked
whether
(1)
a
correlation
existed
between
the
rotational
alignment
of
the
distal
femur
in
the
axial
plane
(posterior
condylar
angle)
and
the
obliquity
of
the
joint
line
of
the
knee
in
the
coronal
plane;
and
(2)
there
was
a
difference
in
the
posterior
condylar
angle
of
the
distal
femur
between
varus
alignment
and
valgus
alignment
Table
1.
Results
of
measurements
compared
with
published
data
Publication
Number
of
knees
Ethnicity
Posterior
condylar
angle
Berger
et
al.
75
White
Male
3.5°
[3]*
(SD
1.2°)
Female
a3°
(SD
1.2°)
Griffin
et
al.
104
White
3.1°
(SD
[5]*
1.75°)
Yip
et
al.
82
Chinese
5.2°
[23]t
(SD
1.9°)
Moreland
et
al.
50
White
[14]*
Hsu
et
al.
120
White
[7]*
Tang
et
al.
100
Chinese
[20]
t
Current
studyt
99
Chinese
(SD
2°)
*
White
data;
tChinese
data.
of
the
mechanical
axis
of
the
lower
limb
in
the
coronal
plane.
Materials
and
Methods
We
assessed
120
young
Chinese
patients
with
anterior
cruciate
ligament
(ACL)
deficiency
attending
an
ACL
reconstruction
preoperative
assessment
clinic
from
March
2008
to
September
2011.
For
patients
with
bilateral
ACL
deficiency
(five
patients),
only
the
right
knee
was
evalu-
ated.
The
inclusion
criteria
were
as
followed:
(1)
Chinese
ethnicity;
(2)
age
from
16
to
40
years
old;
(3)
isolated
ACL
deficiency
without
substantial
collateral
ligament
defi-
ciency;
and
(4)
presence
of
preoperative
MRI
of
the
involved
knee.
Fifteen
knees
did
not
satisfy
the
inclusion
criteria:
substantial
collateral
ligament
laxity
requiring
collateral
ligament
reconstruction
in
two
knees,
MRIs
absent
in
seven
knees,
and
six
knees
in
patients
older
than
40
years.
The
exclusion
criteria
were
as
follows:
(1)
evi-
dence
of
osteoarthritis
of
the
involved
knee
with
a
Kellgren
and
Lawrence
grading
of
2
or
above
[10];
(2)
substantial
malrotation
of
the
standing
long
film
of
the
lower
limb
as
indicated
by
a
noncentral
location
of
the
patella;
and
(3)
MRI
scanning
protocol
not
complying
with
the
research
protocol.
Six
knees
were
excluded
(two
knees
with
evi-
dence
of
osteoarthritis
on
conventional
knee
radiographs,
two
knees
with
malrotated
long
films,
and
two
knees
with
a
suboptimal
MRI
scanning
protocol).
These
exclusions
left
99
patients
with
99
knees
for
analysis.
There
were
87
male
patients
and
12
female
patients.
The
average
age
of
the
patients
was
25
±
6
years
(range,
16-37
years).
There
were
53
right
knees
and
46
left
knees.
Seventy-three
patients
had
meniscal
tears
of
at
least
one
side.
Eighteen
patients
had
isolated
medial
meniscal
tears.
Forty-
two
patients
had
isolated
lateral
meniscal
tears.
Thirteen
patients
had
tears
of
both
medial
and
lateral
menisci.
Eight
patients
underwent
surgery
on
the
involved
knee
before
recruitment.
One
patient
underwent
a
partial
lateral
men-
iscectomy.
Four
had
repair
of
menisci
performed
(two
on
the
medial
meniscus
and
two
on
the
lateral
meniscus).
Three
patients
underwent
diagnostic
arthroscopy.
Sample
size
estimation
was
performed
to
determine
a
possible
correlation
between
joint
line
obliquity
of
the
knee
and
posterior
condylar
angle
of
the
distal
femur.
The
reported
SD
of
joint
line
obliquity
of
the
knee
and
posterior
condylar
angle
of
the
distal
femur
in
Chinese
were
2.4°
[20]
and
1.9°
[23],
respectively.
To
detect
a
weak
to
moderate
association
of
0.3,
assuming
a
Type
I
error
of
0.05
and
setting
the
power
of
study
at
0.8,
a
minimal
sample
of
57
patients
was
required.
Standing
radiographs
of
the
whole
lower
limb
were
taken
using
a
standard
protocol
described
in
a
previous
1
Springer
1460
Yau
et
al.
Clinical
Orthopaedics
and
Related
Research®
study
[20].
All
subjects
were
asked
to
stand,
wearing
their
usual
footwear,
with
both
knees
fully
extended
and
both
patellae
facing
forward
[9].
A
weightbearing
AP
radio-
graph
of
the
entire
lower
limb
then
was
made
with
the
x-ray
beam
centered
at
the
knees
at
a
distance
of
2.5
m.
A
cassette
holding
long
radiographs
(300
x
900
mm)
was
placed
immediately
behind
the
subject.
A
setting
of
60
mA
seconds
and
a
kilovoltage
of
65
to
80
were
required
to
provide
the
necessary
exposure.
Substantial
malrotation
of
the
long
films
was
assumed
to
be
present
if
the
patella
was
not
centrally
located
[9].
Preoperative
MRIs
of
the
knee
were
obtained
in
all
patients.
Among
the
99
patients,
64
patients
underwent
MRI
at
the
author's
institution
and
35
underwent
MRI
at
other
institutions.
The
MRI
scans
at
the
author's
institute
were
performed
with
a
1.5-Tesla
MRI
system
(SignaHD;
General
Electric,
Milwaukee,
WI,
USA)
using
a
knee
coil
(General
Electric).
Six
sequences,
including
T1
and
T2,
in
coronal,
sagittal,
and
axial
planes
were
performed.
The
other
parameters
for
all
six
sequences
included
matrix,
256
x
256;
field
of
view,
16
cm;
thickness,
4
mm;
and
space,
0.5
mm.
The
scanning
of
the
axial
scan
of
the
distal
femur
was
performed
along
the
anatomical
axis
of
the
distal
femur.
MRIs
at
the
other
institutions
were
considered
satisfactory
if
the
following
criteria
were
met:
(1)
the
MRI
system
was
at
least
1.5
Tesla;
(2)
axial
T2-weighed
fat-
saturated
spin
echo
sequence
was
done;
(3)
the
scanning
of
the
axial
scan
of
the
distal
femur
should
be
performed
within
10°
from
the
anatomical
axis
of
the
distal
femur;
and
(4)
the
slice
thickness
should
be
at
least
4
mm
or
less.
The
radiographs
were
digitized
using
a
VXR-12
plus
film
digitizer
(VIDAR,
Herndon,
VA,
USA)
and
mea-
surements
were
made
using
commercially
available
software
(OsiriX
32-bit
4.1.2;
Pixmeo,
Geneva,
Switzer-
land).
The
reported
inter-
and
intraobserver
agreement
in
these
measurements
was
strong
to
perfect
[21].
Two
of
the
authors
(WPY,
CHY)
assessed
the
axial
alignment
of
the
lower
limb
and
joint
line
obliquity
in
the
digitalized
standing
radiographs
of
the
whole
lower
limb.
One
of
the
authors
(WPY)
was
the
treating
surgeon.
Two
angles
were
measured:
the
mechanical
axis
of
the
lower
limb
in
the
coronal
plane
and
the
obliquity
of
the
joint
line
of
the
knee
with
reference
to
the
mechanical
axis
of
the
tibia.
The
mechanical
axes
of
the
femur
and
the
tibia
were
the
lines
joining
the
center
of
the
knee
to
the
center
of
the
femoral
head
and
the
center
of
the
knee
to
the
center
of
the
ankle,
respectively.
The
centers
of
the
joints
were
defined
according
to
the
protocol
previously
described
[14,
20].
The
mechanical
axis
of
the
lower
limb
in
the
coronal
plane
was
defined
as
the
acute
angle
between
the
mechanical
axis
of
the
femur
and
the
mechanical
axis
of
the
tibia
(Fig.
1).
It
was
expressed
in
varus
aligned,
neutral,
or
valgus
aligned.
The
joint
line
of
the
knee
was
defined
as
a
line
tangential
to
the
subchondral
plate
of
the
proximal
tibia
(Fig.
2).
The
obliquity
of
the
joint
line
with
reference
to
the
mechanical
axis
of
the
tibia
was
defined
as
the
acute
angle
between
the
joint
line
of
the
knee
and
perpendicular
to
the
mechanical
axis
of
the
tibia.
It
was
expressed
in
medially
inclined,
neutral,
or
laterally
inclined
(Fig.
2).
The
same
observers
(WPY,
CHY)
measured
the
rota-
tional
alignment
of
the
distal
femur
using
a
T2
axial
cut
MRI
of
the
knee.
The
posterior
condylar
angle
was
mea-
sured
according
to
the
protocol
previously
described
[12].
The
posterior
condylar
angle
was
originally
described
by
Berger
et
al.
[3].
It
was
the
angle
between
the
surgical
epicondylar
axis
and
the
posterior
condylar
line
of
the
distal
femur.
The
surgical
epicondylar
axis
was
a
line
joining
the
medial
and
lateral
femoral
epicondyle.
The
medial
femoral
epicondyle
was
identified
on
the
MRI
as
the
deepest
point
of
the
medial
sulcus,
which
repre-
sented
the
origin
of
the
deep
part
of
the
medial
collateral
ligament.
The
lateral
femoral
epicondyle
was
defined
as
the
most
prominent
point
at
the
origin
of
the
lateral
collateral
Center
of
Hip
Mechanical
Axis
of
Femur
Center
of
Knee
Mechanical
Axis
of
Tibia
Center
of
Ankle
Fig.
1
Mechanical
axis
of
the
lower
limb.
Mechanical
axis
of
the
lower
limb
was
defined
as
the
acute
angle
between
the
mechanical
axis
of
femur
and
mechanical
axis
of
the
tibia.
It
was
expressed
as
varus
aligned,
neutral,
or
valgus
aligned.
Mechanical
axis
of
the
femur
was
the
line
joining
the
center
of
the
femoral
head
and
the
center
of
the
knee.
Mechanical
axis
of
the
tibia
was
the
line
joining
the
center
of
the
knee
and
the
center
of
the
ankle.
1
Springer
4
1
.
Transepicondylar
Axis
4
Lateral
etha
Femoral
F
Mora
I
Epioand
yl
.
picondyl
Posterior
Condylar
Line
'N
Volume
471,
Number
5,
May
2013
Posterior
Condylar
Angle
in
Chinese
1461
Joint
Line
of
Knee
Mechanical
Axis
of
Tibia
Fig.
2
Obliquity
of
the
joint
line
with
reference
to
mechanical
axis
of
the
tibia.
The
joint
line
of
the
knee
was
defined
as
a
line
tangential
to
the
subchondral
plate
of
the
proximal
tibia.
The
obliquity
of
the
joint
line
with
reference
to
mechanical
axis
of
the
tibia
was
defined
as
the
acute
angle
between
the
joint
line
of
the
knee
and
perpendicular
to
the
mechanical
axis
of
the
tibia.
It
was
expressed
as
medially
inclined,
neutral,
or
laterally
inclined.
ligament.
The
posterior
condylar
line
was
defined
as
a
line
tangential
to
the
most
posterior
point
of
the
cartilage
of
the
medial
and
lateral
femoral
condyles
(Fig.
3).
The
inter-
and
intraobserver
variability
of
mechanical
axis
of
the
lower
limb,
obliquity
of
the
joint
line,
and
posterior
condylar
angle
was
determined
with
an
intraclass
correlation.
For
the
repeatability
in
the
measurement
of
mechanical
axis
of
long
film
and
joint
line
obliquity
of
the
knee,
we
found
an
intraobserver
ICC
of
0.87
and
interobserver
agreement
of
0.85
(Table
2).
For
the
repeatability
in
the
measurement
of
the
posterior
condylar
angle,
the
intraobserver
agreement
was
0.74
and
the
interobserver
agreement
was
0.43.
We
assessed
the
association
between
the
rotational
alignment
of
the
distal
femur
(ie,
the
posterior
condylar
angle)
and
the
obliquity
of
the
joint
line
using
a
Pearson
correlation.
We
determined
whether
there
was
a
difference
in
the
posterior
condylar
angle
of
the
distal
femur
between
varus
alignment
and
valgus
alignment
of
the
lower
limb
with
Student's
t-test.
We
used
SPSS
20.0
(IBM,
New
York,
NY,
USA)
for
all
analyses.
Fig.
3
Posterior
condyle
angle.
Posterior
condylar
angle
was
the
angle
between
the
surgical
transepicondylar
axis
and
the
posterior
condylar
line
of
the
distal
femur.
Surgical
transepicondylar
axis
was
a
line
joining
the
medial
femoral
epicondyle
(deepest
point
of
the
medial
sulcus,
where
the
deep
part
of
medial
collateral
ligament
attaches)
and
lateral
femoral
epicondyle
(most
prominent
point
at
the
origin
of
lateral
collateral
ligament).
Posterior
condyle
line
was
a
line
joining
the
most
posterior
point
of
the
medial
and
lateral
femoral
condyle
cartilage.
Table
2.
Interobserver
and
intraobserver
agreement
Measurement
Interobserver Intraobserver
agreement agreement
(intraclass
(intraclass
correlation) correlation)
Posterior
condylar
angle
0.43
0.74
Joint
line
obliquity
of
the
knee
0.85
0.87
Mechanical
axis
of
the
lower
limb
in
the
coronal
plane
0.82
0.98
Results
We
found
an
association
(r
=
0.391,
p
<
0.001)
between
the
obliquity
of
the
joint
line
of
the
knee
in
the
coronal
plane
and
the
posterior
condylar
angle
of
the
distal
femur
in
the
axial
plane.
The
average
obliquity
of
joint
line
was
medial
inclination.
The
average
posterior
condylar
angle
was
(Table
3).
The
posterior
condylar
angle
in
patients
with
varus
alignment
of
the
lower
limb
was
larger
than
that
in
patients
with
valgus
alignment
(p
=
0.015).
The
average
mechan-
ical
axis
of
the
lower
limb
was
varus
(Table
3).
Sixty
lower
limbs
were
in
varus
alignment.
The
average
posterior
condylar
angle
in
varus
of
the
knee
was
6°.
Thirty-nine
lower
limbs
were
in
valgus
alignment.
The
average
pos-
terior
condylar
angle
in
valgus
of
the
knee
was
5°.
1
Springer
1462
Yau
et
al.
Clinical
Orthopaedics
and
Related
Research®
Discussion
It
is
well
known
that
the
osteometry
of
Asians
differs
from
that
of
Western
populations
[4,
11,
19,
20,
22,
23]
(Fig.
4).
The
lower
limb
alignment
was
more
varus
and
the
Table
3.
Axial
alignment
of
the
lower
limb,
obliquity
of
the
joint
line,
and
rotational
alignment
of
the
distal
femur
Measurement
Result
Posterior
condylar
angle
±
(1°-10°)
Male:
±
Female:
±
Joint
line
obliquity
Medial
inclined
±
with
reference
to
mechanical
(medial
inclined
11°
axis
of
tibia
to
lateral
inclined
2°)
Male:
medial
inclined
±
Female:
medial
inclined
±
Axial
alignment
of
the
lower
Varus
±
limb
in
the
coronal
plane
(valgus
to
varus
8°)
Male:
varus
±
Female:
valgus
±
Chinese
Fig.
4
Comparison
between
white
and
Chinese
lower
limb
osteom-
etry.
The
lower
limb
alignment
was
more
varus
and
the
knee
was
more
medially
inclined
in
Chinese
when
compared
with
white
patients.
obliquity
of
the
joint
line
of
the
knee
was
more
medially
inclined
in
a
group
of
young
Chinese
volunteers
with
an
average
age
of
24
years
[20].
The
posterior
condylar
angle
of
Chinese
was
noted
to
be
larger
in
studying
82
embalmed
Chinese
cadaveric
femurs
of
an
average
age
of
78
years
[23]
(Table
1).
However,
it
is
unclear
whether
there
is
a
direct
correlation
between
the
coronal
plane
osteometry
and
the
axial
plane
osteometry
of
the
distal
femur.
We
therefore
asked
whether
(1)
a
correlation
existed
between
the
rotational
alignment
of
the
distal
femur
in
the
axial
plane
(posterior
condylar
angle)
and
the
obliquity
of
the
joint
line
of
the
knee
in
the
coronal
plane;
and
(2)
whether
there
was
a
difference
in
the
posterior
condylar
angle
of
the
distal
femur
between
varus
alignment
and
valgus
alignment
of
the
mechanical
axis
of
the
lower
limb
in
the
coronal
plane.
There
were
a
number
of
limitations
in
the
current
study.
First,
the
subjects
recruited
were biased
to
a
group
of
young
active
patients
with
ACL
deficiency.
The
characteristics
of
the
patients
were
different
from
those
of
older
patients
requiring
TKA.
However,
early
degeneration
is
more
likely
in
this
group
of
ACL-deficient
patients
[13,
15-17]
because
of
the
abnormal
biomechanics
in
the
knee
and
high
chance
of
concomitant
meniscal
and
cartilage
injury.
Second,
females
were
underrepresented
(14%
of
the
studied
knees).
This
was
related
to
the
primary
diagnosis
in
the
inclusion
criteria
(ACL-deficient
knee),
which
was
more
common
in
men
than
in
women
in
our
population.
Third,
despite
the
attempts
at
minimizing
biases
arising
from
malrotation
of
the
standing
radiographs
of
the
lower
limb,
errors
in
this
area
were
still
unavoidable.
In
a
cadaveric
experiment
testing
the
influence
of
rotation
on
the
errors
in
measure-
ment
of
the
mechanical
axes
of
the
femur,
the
average
reported
variation
was
2.5°
between
the
positions
of
20°
of
internal
rotation
and
20°
of
external
rotation
[9].
By
excluding
patients
with
excessive
rotation
in
the
standing
long
radiographs,
the
impact
should
be
negligible.
Fourth,
the
use
of
MRI
in
assessing
the
rotational
axes
of
the
distal
femur
might
not
be
optimal.
CT
would
be
a
better
option
for
identifying
these
bony
landmarks.
However,
preopera-
tive
CT
carried
substantial
radiation
hazard
and
was
not
appropriate
for
a
group
of
young
active
individuals
for
clinical
purposes.
Furthermore,
because
the
two
collateral
ligaments
could
be
identified
on
the
MRI,
these
provided
an
additional
clue
in
locating
the
two
femoral
epicondyles.
Fifth,
the
interobserver
repeatability
of
measurement
of
the
posterior
condylar
angle
was
not
high,
although
the
intra-
observer
agreement
was
(Table
2).
This
might
be
related
to
the
anatomy
of
the
medial
femoral
epicondyle,
which
was
a
sulcus
located
in
the
center
of
a
horseshoe-shaped
ridge.
The
depth
of
the
sulcus
was
small
and
could
be
difficult
to
locate
[5].
Sixth,
73
of
99
patients
had
meniscal
tears.
One
patient
had
a
history
of
partial
lateral
meniscectomy.
The
1
Springer
r
=
0.391
(
p
<
0.001)
10-
.
.
5-
gm
-r
••••
.
s
.
-2
0
2
4
6
8
10
12
Joint
Line
Obliquity
of
Knee
(degrees)
(Medially
inclined:
positive;
Laterally
inclined:
negative)
0
Mean
=
(SD
2
°
)
Externally
Rotated
or
more
20
15
-
10
Volume
471,
Number
5,
May
2013
Posterior
Condylar
Angle
in
Chinese
1463
Is-
Fig.
5
Relationship
between
joint
line
obliquity
and
posterior
condylar
angle.
The
coronal
plane
knee
line
obliquity
was
associated
with
the
axial
plane
posterior
condylar
angle
of
the
distal
femur.
The
average
joint
line
obliquity
was
medially
inclined
and
the
average
posterior
condylar
angle
was
5°.
presence
of
meniscal
tears,
especially
medial,
might
influence
the
varus
deformity
of
the
knee.
We
found
an
association
between
the
rotational
align-
ment
of
the
distal
femur
and
the
joint
line
obliquity
with
reference
to
the
anatomical
axis
of
the
proximal
tibia
(Fig.
5).
The
average
joint
line
obliquity
in
a
group
of
young
Chinese
patients
with
ACL
deficiency
in
the
current
study
was
5°.
This
was
larger
than
the
reported
data
in
the
white
study
(0.5°
[7]
and
2.8°
[14])
(Table
1).
The
pos-
terior
condylar
angle
was
in
the
current
study,
which
was
also
bigger
than
that
reported
in
the
white
population
(3.5°
for
males
and
0.3°
for
females
in
one
study
[3]
and
3.1°
in
another
study
[5])
(Table
1).
A
large
variation
of
posterior
condylar
angle
(1°-10°)
(Fig.
6)
was
found
in
the
current
study.
This
finding
cautions
the
practice
of
routine
use
of
a
fixed
angle
of
external
rotation
from
the
posterior
condylar
line
(eg,
3°)
in
determining
the
rotation
of
femoral
components
during
TKA
in
Chinese.
Reference
to
multiple
anatomical
axes
(eg,
transepicondylar
axis
and
Whiteside
line)
and
adoption
of
a
balanced
flexion
gap
method
and
distracter
should
be
considered
in
individualizing
the
rotation
of
the
femoral
component.
The
finding
of
an
association
between
the
joint
line
obliquity
and
posterior
condylar
angle
may
further
help
preoperative
planning
of
the
rotational
alignment
of
the
femoral
component,
espe-
cially
if
an
excessive
medially
inclined
joint
line
is
observed
in
the
proximal
tibia
on
the
preoperative
radiograph.
Varus
alignment
of
the
lower
limb
was
associated
with
larger
posterior
condylar
angle
of
the
distal
femur.
Despite
the
fact
that
the
average
alignment
in
our
study
was
in
the
0
2
4
6
S
10
12
Posterior
Condylar
Angle
(Degrees)
Fig.
6
Distribution
of
posterior
condylar
angle.
The
average
poster-
ior
condylar
angle
was
5°.
However,
the
dispersion
was
large
(2°-
10°).
More
than
90%
of
the
knee
had
a
posterior
condylar
angle
of
more
than
3°.
Varus
1
°
(SD
3
°)
-10
-5
0
5
10
Mechanical
Axis
of
Lower
Limb
(degrees1
(Varus:
positive
and
Valgus:
negative)
Fig.
7
Distribution
of
mechanical
axis
of
the
lower
limb.
The
mean
mechanical
axis
was
varus
1°.
The
alignment
ranged
from
valgus
to
valgus
8°.
Thirteen
knees
had
a
lower
limb
mechanical
axis
alignment
of
varus
or
more.
range
of
that
in
white
reports
[7,
14],
the
dispersion
of
the
data
was
higher
in
our
series
(Fig.
7).
The
maximal
varus
alignment
was
varus
8°.
Thirteen
knees
(13%)
had
a
lower
limb
alignment
of
varus
or
more.
This
varus
malalign-
ment
of
the
lower
limb
in
a
group
of
young
ACL-deficient
Chinese
is
likely
to
be
developmental
in
nature.
The
medial
collateral
ligament
may
be
relatively
shorter.
The
associ-
ation
of
varus
knee
alignment
with
larger
posterior
condylar
angle
might
create
additional
difficulty
in
per-
forming
ligament
balance
during
TKA
in
Chinese.
This
is
Pos
ter
ior
Con
dy
lar
Ang
le
(
deg
rees
)
Freq
ue
ncy
(
Nu
m
be
r
o
f
cases
)
20
15
5
1Springer
1464
Yau
et
al.
Clinical
Orthopaedics
and
Related
Research®
because
more
aggressive
medial
release
may
be
required
in
restoring
the
limbs
back
to
neutral
mechanical
axis.
In
the
presence
of
a
larger
posterior
condylar
angle,
if
the
femoral
component
is
to
be
placed
parallel
to
the
transepicondylar
axis,
paradoxical
medial
laxity
may
occur
in
the
flexion
gap.
This
may
result
in
midflexion
instability
of
the
replaced
knee.
To
conclude,
we
found
an
association
between
the
joint
line
obliquity
of
the
knee
in
the
coronal
plane
and
posterior
condylar
angle
in
the
axial
plane
in
young
Chinese
patients
with
ACL
deficiency.
Varus
alignment
of
the
lower
limb
in
young
patients
without
osteoarthritis
was
associated
with
larger
posterior
condylar
angle
of
the
distal
femur.
References
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Akagi
M,
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Y,
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T,
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Y,
Horiguchi
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H,
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Effect
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knee
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Jacobs
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Insall
JN,
Binazzi
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Clin
Orthop
Relat
Res.
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Jiang
CC,
Insall
JN.
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of
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on
the
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of
the
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Pitfalls
in
the
use
of
femoral
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in
total
knee
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Clin
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Kellegren
JII,
Lawrence
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