The morphology of the femur in
developmental dysplasia of the hip
Nobuhiko Sugano, Philip C. Noble, Emir Kamaric, Joseph K. Salama,
Takahiro Ochi, Hugh S.Tullos
From Baylor College of Medicine, Houston, Texas and Osaka University Medical
School, Suita, Japan
e studied the morphometry of 35 femora from
31 female patients with developmental dysplasia
of the hip (DDH) and another 15 from 15 age- and
sex-matched control patients using CT and
three-dimensional computer reconstruction models.
According to the classification of Crowe et al 15 of the
dysplastic hips were graded as class I (less than 50%
subluxation), ten as class II/III (50% to 100%
subluxation) and ten as class IV (more than 100%
subluxation).
The femora with DDH had 10 to 14° more
anteversion than the control group independent of the
degree of subluxation of the hip. In even the most
mildly dysplastic joints, the femur had a smaller and
more anteverted canal than the normal control. With
increased subluxation, additional abnormalities were
observed in the size and position of the femoral head.
Femora from dislocated joints had a short, anteverted
neck associated with a smaller, narrower, and
straighter canal than femora of classes I and II/III or
the normal control group.
We suggest that when total hip replacement is
performed in the patient with DDH, the femoral
prosthesis should be chosen on the basis of the
severity of the subluxation and the degree of
anteversion of each individual femur.
W
J Bone Joint Surg [Br] 1998;80-B:711-9.
Received 28 August 1997; Accepted after revision 16 January 1998
N. Sugano, MD, Assistant Professor
T. Ochi, MD, Professor and Chairman
Department of Orthopaedic Surgery, Osaka University Medical School,
2-2 Yamadaoka, Suita 565-0871, Japan.
P. C. Noble, PhD, Associate Professor
E. Kamaric, MS, Senior Research Associate
J. K. Salama, BS, Medical College Student
H. S. Tullos, MD, Professor and Chairman
Department of Orthopaedic Surgery, Baylor College of Medicine, 6565
Fannin Suite 2626, Houston, Texas 77030, USA.
Correspondence should be sent to Dr N. Sugano.
©1998 British Editorial Society of Bone and Joint Surgery
0301-620X/98/48319 $2.00
VOL. 80-B, NO. 4, JULY 1998
Developmental dysplasia of the hip (DDH) is the most
common underlying condition leading to secondary osteo1-4
arthritis of the hip although the incidence of the latter
varies on a regional and ethnic basis. In the absence of
degenerative changes, femoral and/or pelvic osteotomies
are often performed to correct DDH in an attempt to restore
coverage of the femoral head. In advanced degenerative
disease in the adult, total hip arthroplasty is done to eliminate subluxation and restore the normal position of the
abductors with respect to the centre of the joint. This can
only be successfully achieved if the nature and severity of
the preoperative deformity are fully appreciated.
There have been few detailed studies of the morphometry of the dysplastic femur. It is well known that it often
5-8
has a narrow medullary canal and increased anteversion,
but the differences in the size and shape between normal
and dysplastic femora have not yet been quantified. Previous studies have reported dimensional parameters derived
from plain radiographs or CT of patients with DDH of
varying degrees of severity, but without corresponding
9,10
control groups.
The size and shape of the human femur,
however, vary with the gender, age, stature and ethnic
11
background of the individual and it is not possible to
isolate the effect of dysplasia on its shape. The degree of
subluxation of the hip also leads to significant alterations in
the shape of the femur because of profound changes in the
magnitude and direction of the joint reaction force.
Because of the anatomical abnormalities of the dysplastic femur, it is widely believed that if total hip replacement is performed using conventional designs of femoral
prostheses, the centre of the femoral head will not be
restored to an acceptable position. This has led to the
increased use of customised prostheses and the emergence
8,12-16
of implants specifically designed for DDH.
Since the
anatomical abnormalities present are thought to increase
6,15
with the severity of subluxation of the hip,
the technical
difficulty in performing joint replacement and the appropriate design of a femoral prosthesis may be related to the
severity of the disease by its effect on the morphology of
the dysplastic femur.
Our aim was to evaluate the hypothesis that the threedimensional anatomy of the femur with DDH differs fundamentally from that of the normal femur and is related to the
degree of subluxation of the hip.
711
712
N. SUGANO,
Fig. 1a
P. C. NOBLE,
E. KAMARIC,
ET AL
Fig. 1b
Fig. 1c
Radiographs of a) class-I b) class-II/III and c) class-IV femora.
Patients and Methods
We studied 35 femora from 31 adult female patients with
DDH who represented variable degrees of subluxation.
6
According to the classification of Crowe et al 15 hips were
class I (less than 50% subluxation) (Fig. 1a), ten class II or
III (50% to 100% subluxation) (Fig. 1b) and ten class IV
(more than 100% subluxation) (Fig. 1c). Eight patients in
class I and class II/III had had closed reduction of the hip
during childhood and one patient in class I open reduction.
In the remaining 22 patients subluxation or dislocation of
the hip had been noticed after the age of three years and
had remained untreated. None of these patients had had an
osteotomy for treatment or correction of their hip disease.
We excluded patients with radiological evidence of joint
degeneration or total ischaemic necrosis of the femoral
17
head.
The three groups were matched as closely as possible for
age. The overall mean age was 54.7 ± 11.2 (SD) years (23 to
73); patients in class I had a mean age of 52.5 ± 12.6 years
(23 to 73) compared with 53.4 ± 11.0 years for those in
class II/III (31 to 70) and 59.4 ± 8.5 years for class IV (43
to 69) (p > 0.05, unpaired t-test). An additional group of 15
age-matched female patients (mean age 59.7 ± 14.9 years;
range 20 to 78) served as a normal anatomical control
group. They had undergone radiological investigation of
non-traumatic osteonecrosis of the femoral head (8
patients) or rheumatoid arthritis (7 patients) and had at least
one hip that was radiologically normal without collapse of
the femoral head or erosive changes.
The mean height of the patients with DDH in class I was
152 ± 4.2 cm (146 to 160), in class II/III 150 ± 5.8 cm (143
to 157) and in class IV 147 ± 6.8 cm (138 to 157). That of
the control group was 152 ± 6.8 cm (138 to 164). There
was no statistically significant difference between the four
groups except between classes I and IV (p = 0.02, unpaired
t-test). The mean body-weight was 54 ± 4.2 kg (46 to 62) in
class I, 54 ± 7.9 kg (38 to 68) in class II/III, 52 ± 7.3 kg (42
to 62) in class IV, and 54 ± 10.2 kg (36 to 76) in the control
group. None of these differences was statistically significant. The average height and weight of the DDH and
control groups were identical to published data for Japanese
women of 50 to 59 years of age (152 ± 5.1 cm and 54 ±
18
8.0 kg).
Transverse images were obtained of each femur using a
helical CT scanner (CT HiSpeed Advantage RP; GE, Milwaukee, Michigan) according to a standard CT protocol
with a field of view of 34 cm. Each CT image was reconstructed using a standard bone algorithm (GE). Image data
stored on an optical disc were converted to a tiff format of
512 512 matrix by a data conversion program (GE
MOD/RPF; Image and Measurement, Tokyo, Japan) and a
digital image analysis program (BrainImage; Kennedy
Krieger Institute, Baltimore, Maryland) operating on a
desktop computer (Power Tower Pro 225; Power Computing, Round Rock, Texas).
The hip and knee were fully extended with the lower
limbs secured to the table with a below-knee splint which
fixed the rotational position of the limb. Positioning was
checked by anteroposterior and lateral scout views. Each
femur was imaged using the following set of transverse
scans: 1) contiguous 3 mm slices from the top of the
femoral head to 2 cm below the lesser trochanter; 2) 3 mm
slices at 10 mm intervals from 2 cm below the lesser
THE JOURNAL OF BONE AND JOINT SURGERY
THE MORPHOLOGY OF THE FEMUR IN DEVELOPMENTAL DYSPLASIA OF THE HIP
713
Fig. 2
Three-dimensional reconstructed model of a class-I
femur. The extracortical (A) and intracortical (B) models are initially orientated with the femoral condyles
resting on the table plane. The models are then translated and rotated in space until the axis of the femoral
shaft and the centre of the head are located within the
coronal plane (C and D).
trochanter to 2 cm below the isthmus of the femoral canal;
and 3) seven serial slices of 3 mm thickness through the
femoral condyles.
A customised program was developed to reconstruct the
image of each femur from the CT data and to allow
calculation of dimensional and morphological variables. All
the data could be extracted independently of the position of
the patient during scanning and the orientation of the
original CT slices with respect to the femur.
In the first stage of the bone reconstruction process the
inner (endosteal) and outer (periosteal) contours of the
femur were extracted using a Laplacian and Gaussian filter
19-21
Specialised pattern recogwith a gradient thresholding.
nition software was then used to partition the co-ordinate
data into subsets describing the internal and external surfaces of six contiguous regions within each femur (the
femoral head, the neck, the greater and lesser trochanters,
the metaphysis and diaphysis and the femoral condyles).
Three-dimensional surface-splined models of each contiguous region were constructed and reorientated until the
axis of the femoral shaft and the centre of head were
located within the coronal plane with the femoral axis
parallel to the vertical direction (Fig. 2). The following
variables were calculated:
1) The centre and diameter of the femoral head, obtained
from the sphere of best fit to data describing the surface of
the head. Severely deformed regions of the femoral head
were visually identified and eliminated from the
calculation.
2) The height of the centre of the femoral head, defined as
VOL. 80-B, NO. 4, JULY 1998
the vertical distance from the centre of the lesser trochanter
(CLT) to the centre of the femoral head.
3) The medial offset of the femoral head, defined as the
perpendicular distance from the medullary axis to the centre of the head.
4) The axis of the femoral neck, calculated as the line of
best fit to the centroids of 1 mm slices taken through a
central segment of the neck (length 21 mm) (Fig. 3).
5) The canal isthmus, defined as the point of minimum
Fig. 3
A surface model of the femoral neck. The neck axis
is shown by the dotted line, constructed by joining
the centroids of transverse slices taken through the
femoral neck.
714
N. SUGANO,
P. C. NOBLE,
Fig. 4
A top view of the femur orientated within the table-top co-ordinate system
showing the centre of the femoral head (A), the axis of the medullary
canal (B) and the axis of the femoral neck (C).
cross-sectional area of the medullary canal.
6) The length of the femoral neck defined as the distance
between two points on the neck axis located closest to the
centre of the femoral head and the medullary axis,
respectively.
7) The height of the greater trochanter, defined as the
vertical distance from the CLT to the tip of the
trochanter.
8) The mediolateral diameter of the medullary canal, measured at four levels within the canal: the 35% level (35% of
the head centre height above the CLT), the level of the CLT,
the –35% level (35% of the head centre height below the
CLT), and the level of the canal isthmus. The maximum
value of the mediolateral extracortical diameter of the
diaphysis was also recorded.
Table I. Mean (±
SD)
E. KAMARIC,
ET AL
9) The anteversion of the femur, defined according to
22
Kingsley and Olmsted in a spatial co-ordinate system
simulating placement of the femur on a flat surface. For this
purpose, the three-dimensional model was positioned with
the table plane (z-x plane) coincident with the posterior
condyles and the most prominent posterior point of the
greater trochanter. The axis of the femoral shaft was
defined as the line connecting the centroids of a transverse
section through the femur at the base of the lesser trochanter and a section taken through the distal condyles at the
point of greatest anteroposterior width of the femur. Femoral anteversion was defined as the angle formed between
the axis of the neck and the table plane when viewed along
the femoral axis (Fig. 4).
11,23
10) The canal flare index,
calculated as the ratio
between the mediolateral width of the medullary canal at
the 35% level and at the canal isthmus.
11) The major axis angle, defined as the angle between a
line connecting the longest transverse diameter of the canal,
was measured at the same level as the mediolateral diameter of the canal. This parameter was selected as a
measure of canal rotation.
We performed statistical analysis on the morphological
variables of the four groups. Initially, we tested the distribution of each variable for normality using the ShapiroWilk W test. For normally distributed variables, differences
between groups were analysed by ANOVA followed by the
unpaired t-test for multiple pair-wise comparisons of all
significant variables (p < 0.05). The Kruskal-Wallis test
was applied to all variables that were not normally distributed, followed by the Mann-Whitney test for nonparametric post-hoc comparisons. In view of the large
number of comparisons performed in this study (102), the p
value for a statistically significant difference between two
variables was set at 0.005. Although this threshold provides
a good balance between type-I and type-II errors, the
dimensional parameters in each group
Class
Control
Height of centre of femoral head (mm)
Diameter of femoral head (mm)
Neck length (mm)
Height of greater trochanter (mm)
Isthmus position (mm)
Mediolateral extracortical diameter of the diaphysis (mm)
Median lateral canal width (mm)
At 35% of head centre height above CLT
At CLT
At 35% of head centre height below CLT
At isthmus
Canal flare index
Anteroposterior canal width at isthmus (mm)
Neck-shaft angle (degrees)
Anteversion (degrees)
Major axis angle (degrees)
At 35% of head centre height above CLT
At CLT
At 35% of head centre height below CLT
At isthmus
I
II or III
IV
44.2
44.1
47.5
54.3
106.7
25.3
±
±
±
±
±
±
5.4
2.0
5.5
4.0
14.2
1.8
45.7
44.9
43.0
53.8
98.5
23.8
±
±
±
±
±
±
6.5
1.9
3.0
3.6
11.8
1.5
36.3
50.9
38.0
50.3
105.6
22.6
±
±
±
±
±
±
7.2
5.3
5.3
4.9
8.3
1.7
39.0
42.2
35.7
55.8
93.5
21.6
±
±
±
±
±
±
4.9
6.1
4.4
5.8
10.8
1.5
41.7
29.9
23.7
12.8
3.4
16.3
125.8
22.6
±
±
±
±
±
±
±
±
2.8
3.4
4.3
2.6
0.7
3.1
6.3
10.6
38.6
26.5
19.8
9.8
4.0
13.0
127.9
34.0
±
±
±
±
±
±
±
±
3.1
2.2
2.4
0.9
0.5
1.9
8.9
16.0
40.9
30.9
24.8
10.6
3.9
14.7
123.9
32.8
±
±
±
±
±
±
±
±
3.1
3.3
4.0
2.0
0.7
2.0
5.2
14.4
31.2
23.2
18.5
10.4
3.0
13.6
117.7
37.0
±
±
±
±
±
±
±
±
4.3
4.1
4.1
1.5
0.5
2.4
6.6
5.4
15.2
35.2
39.6
70.2
±
±
±
±
10.4
8.8
10.2
12.8
28.4
46.1
54.8
68.7
±
±
±
±
17.1
14.4
13.2
13.1
29.3
43.2
49.9
72.9
±
±
±
±
17.3
14.2
14.9
10.3
39.1
47.5
55.7
67.3
±
±
±
±
8.2
8.0
10.4
12.8
THE JOURNAL OF BONE AND JOINT SURGERY
THE MORPHOLOGY OF THE FEMUR IN DEVELOPMENTAL DYSPLASIA OF THE HIP
715
Table II. Statistical significance (p value) of the femoral dimensions in each group
Height of centre of femoral head (mm)
Diameter of femoral head (mm)
Neck length (mm)
Height of greater trochanter (mm)
Isthmus position (mm)
Mediolateral extracortical diameter of the diaphysis (mm)
Mediolateral canal width (mm)
At 35% of head centre height above CLT
At CLT
At 35% of head centre height below CLT
At isthmus
Canal flare index
Anteroposterior canal width at isthmus (mm)
Neck-shaft angle (degrees)
Anteversion (degrees)
Major axis angle (degrees)
At 35% of head centre height above CLT
At CLT
At 35% of head centre height below CLT
At isthmus
Control v
class I
Control v
class II/III
Control v
class IV
Class I v
class II/III
Class I v
class IV
Class II or III
v class IV
0.4748
0.3185
0.0116
0.7642
0.0737
0.0126
0.0026
0.0010
0.0001
0.0309
0.8213
0.0002
0.0519
0.3048
0.0001
0.4285
0.0103
0.0001
0.0004
0.0036
0.0108
0.0565
0.1496
0.0793
0.0113
0.1741
0.0003
0.2908
0.2945
0.0019
0.2850
0.0065
0.2660
0.0082
0.0258
0.1788
0.0135
0.0064
0.0063
0.0012
0.0098
0.0023
0.4140
0.0121
0.4045
0.4478
0.4717
0.0350
0.0297
0.1924
0.5146
0.0305
0.0001
0.0001
0.0013
0.0147
0.1758
0.0246
0.0075
0.0005
0.1204
0.0018
0.0019
0.3457
0.8682
0.0350
0.1700
0.6978
0.0003
0.0146
0.3905
0.2120
0.0004
0.5603
0.0009
0.2673
0.0004
0.0001
0.0004
0.7910
0.0019
0.1988
0.0565
0.1306
0.0120
0.0142
0.0013
0.7446
0.0159
0.1034
0.0449
0.5959
0.0001
0.0140
0.0022
0.5991
0.8706
0.5396
0.3235
0.4124
0.0666
0.7833
0.8554
0.8143
0.1243
0.4184
0.2865
0.3368
chance of at least one spurious significant difference was
102
40% (1-[1-0.005] ).
Results
The mean length of the femur, as measured on the anteroposterior scout view was 400 ± 15 mm (382 to 434) for the
control group, compared with an overall mean of 391 ±
19 mm (353 to 440 mm) for the dysplastic groups
24
(p > 0.05, unpaired t-test). The mean CE angle was 10 ±
5.8° (0 to 18) for class I and 28 ± 5.8° (20 to 38) for the
25
control group. The mean Sharp angle was 47.9 ± 3.2° (43
to 52) for class I and 39.3 ± 3.8° (29 to 44) for the control
group.
Tables I and II give the measured variables in the four
groups and the p values for pair-wise comparisons for each
variable. The mean shape of the femur in each group is
shown in Figure 5. There was no significant variation
between groups in terms of the height of the centre of the
head and the canal orientation at the isthmus. There were
few differences between femora in class I and in the control
group but the medullary canals of class-I femora were
shorter and were more tapered than those of the agematched control group as indicated by differences in the
canal flare index (p < 0.05). The inclination of the femoral
neck was similar in class-I and control femora, but the
femoral neck and the medullary canal were more anteverted
at all levels proximal to the medullary isthmus. With the
exception of the major axis angle at the isthmus, all of these
differences were statistically significant (Tables I and II).
In the DDH groups, the height of the centre of the
femoral head, the neck length, and the extracortical mediolateral diameter at the isthmus decreased with subluxation
of the hip (Table I). The widths of the medullary canal at
the 35% level, at the CLT, and at the –35% level were
significantly smaller in class IV than in class I, class II/III,
VOL. 80-B, NO. 4, JULY 1998
and the control group (Table II and Fig. 6). The width of
the canal at the isthmus was comparable in all three DDH
groups. Class-IV femora had the straightest canals, compared with class-I and class-II/III femora (Figs 6 and 7), as
indicated by the values of the canal flare index (3.0 v 4.0
and 3.9, respectively). The canal taper of class I, class II/
III, and the control femora were similar above the 35%
level.
The average neck-shaft angles of the control and dysplastic femora were very similar, although there were some
differences in the distributions of both groups (p = 0.371)
(Fig. 8). Overall, the incidence of coxa valga (neck-shaft
angle >135°) was 7% in the normal femora and 9% in the
DDH group, while coxa vara (neck-shaft angle <115°)
occurred in none of the normal femora but in 11% of the
dysplastic group. Within the DDH femora, the neck inclina-
Fig. 5
The mean shape of the femur in each dysplastic group (continuous line)
compared with the normal control group (dotted line). The extracortical
boundaries have been removed for clarity.
716
N. SUGANO,
P. C. NOBLE,
E. KAMARIC,
ET AL
Fig. 6
The mean values of the maximum mediolateral (ML)
width of the canal, at the 35% level, at the centre of the
lesser trochanter (CLT), at the –35% level, and at the
isthmus.
Fig. 7
Three-dimensional reconstructed model of a class-IV
femur. The extracortical (A) and intracortical (B) models are initially orientated with the femoral condyles
resting on the table plane. The models are translated
and rotated in space until the axis of the femoral shaft
and centre of the head are located within the coronal
plane (C and D).
tion decreased with increasing severity of subluxation, with
an increased incidence of coxa vara in the femora of class
IV, compared with class I or class II/III (p < 0.01 and
p < 0.05) (Figs 2 and 7).
The femora with DDH had anteversion on average of
more than 10 to 14° of that of the age-matched control
group. In addition, the incidence of excessively anteverted
femora (anteversion >40°) was only 7% in the normal
femora compared with 23% in femora with DDH (Fig. 9).
The anteversion in all three DDH groups was comparable.
Moreover, the axial variation in the rotational orientation of
the medullary canal was remarkably similar for both the
normal and DDH femora. This supports the conclusion that
the observed differences in anterior offset of the femoral
head were due to differences in canal torsion, primarily
between the isthmus and the –35% level of the canal. The
change in rotational orientation of the canal above the 35%
level was similar in class I and class II/III compared with
the normal control group.
Discussion
Previous studies on the morphology of the femur in adults
with DDH have made qualitative and clinical observations
THE JOURNAL OF BONE AND JOINT SURGERY
THE MORPHOLOGY OF THE FEMUR IN DEVELOPMENTAL DYSPLASIA OF THE HIP
717
Fig. 8
Bar chart of the neck-shaft angle of the normal and
dysplastic femora.
Fig. 9
Bar chart of the neck anteversion of the normal and
dysplastic femora.
Fig. 10
Variation of the torsional alignment of the medullary
canal at the 35% level, at the centre of the lesser
trochanter (CLT), at the –35% level and at the isthmus.
Corresponding values of the mean anteversion of each
group are included for comparison.
VOL. 80-B, NO. 4, JULY 1998
718
N. SUGANO,
P. C. NOBLE,
on the basis of plain radiographs. A common characteristic
of DDH is an unusually small femoral head associated with
a short femoral neck, which is often markedly antever5-7,14,26
The dysplastic femur has also been shown to
ted.
have a straighter, more tapered canal with an unusually
6,13,16,26
narrow medullary isthmus
and the neck-shaft angle
is more valgus than that of the normal femur, resulting in a
9
medial cortex of a larger radius.
Few previous studies have used CT and three-dimensional reconstruction to describe fully the deformities asso9
ciated with hip dysplasia. Robertson et al were the first to
use these techniques to examine the geometry of the proximal femur in 24 Japanese adults with DDH. Their findings
led to the development of an average model of the dysplastic femur but their study was based on a heterogeneous
group of male and female patients with widely varying
degrees of subluxation. Furthermore, as there was no control group, they could only draw conclusions regarding
abnormalities of the shape and dimensions of the dysplastic
femur on the basis of anatomical parameters derived from
normal femora of Western populations.
In our study, all the groups were matched for age and
gender since significant changes in the shape of the prox23
imal femur have been related to these variables. All our
measurements were derived from three-dimensional reconstructions of individual femora, based upon CT data
obtained using a high-speed helical scanner. This allowed
us to compare the morphometry of normal femora with
each of the dysplastic groups. Our findings showed that
although the stature of the patients and the overall length of
their femora were not significantly different from those of
the normal control group, even the femora in class I had
significant anatomical abnormalities, including a shorter
femoral neck and a narrower diaphysis and intramedullary
canal. Similar findings were observed in patients with more
severe dysplasia and subluxation in whom femoral hypoplasia was a common observation.
Our study also showed that dysplastic femora had a
significant increase in anteversion of the femoral neck.
Although this was highly variable, mildly dysplastic femora
(class I) had anteversion of 12° more than that of the
normal control group, with anteversion of individual cases
exceeding 60°. Class-II/III and class-IV femora also
showed similar abnormalities with anteversion of 10 to 14°
more than normal. When we compared the canal orientation of each group, we found that the increased torsion of
the DDH femora arose within the diaphysis between the
lesser trochanter and the isthmus (Fig. 10). This finding
supports the theory that the excessive anteversion of the
DDH femur is due to abnormal internal rotation of the limb
27-30
because femoral anteversion has been shown
in utero
to decrease throughout childhood at a relatively constant
rate as part of the normal process of skeletal maturation,
31,32
even in cases of DDH.
We therefore expect that, at
birth, the anteversion angles of our DDH patients were
even greater than our mean value of 34.6°.
E. KAMARIC,
ET AL
The cross-sectional shape of the medullary canal was
remarkably similar in all four groups. The major canal axis
at the isthmus was orientated in the same direction in the
DDH and normal femora and the AP diameter of the canal
was larger than the ML diameter. This finding contradicts
26
the observation of Mendes who stated that the shape of
the DDH canal was narrower in the frontal plane than in the
sagittal plane as a result of residual or excessive anteversion of the proximal femur and the femoral neck.
It is widely believed that coxa valga is typically present
13
in the DDH femur but we found no significant difference
in the neck-shaft angle of class I and control femora. On the
contrary, the mean inclination of the femoral neck decreased
slightly with increasing severity of subluxation (Table I) and
therefore there were significantly more cases of coxa vara in
patients classified as class IV than in the control group. The
impression that the DDH femur has a more valgus neck
inclination is probably due to the normal effect of anteversion on the appearance of the proximal femur as projected
on a standard AP radiograph. As the neck of the average
DDH femur is orientated at 35° to the coronal plane, the AP
radiograph gives an oblique view of the proximal femur,
with significant foreshortening of the neck.
We have shown that the Crowe classification is a useful
guide for the selection of femoral prostheses. In cases of
class I, II or III subluxation, conventional designs of femoral stem may be acceptable in many cases, provided that
due consideration is given to the small size of many femora
15,33
In cases of more than 40° of anteversion,
in DDH.
16,34
however, a corrective osteotomy,
a retroverted insertion
of a cemented stem, a customised implant, or a prosthesis
with a modular neck that allows adjustment of antever13
sion may be required. In cases of class IV, the canal is
straight and narrow and a straight stem with little proximal
medial curvature should be used, even if a hip replacement
together with a segmental osteotomy and preservation of
16
the femoral neck are needed.
We suggest therefore that when total hip replacement is
performed in the DDH patient, the femoral prosthesis
should be chosen on the basis of the severity of subluxation
of the hip and the degree of anteversion of each individual
femur.
Although none of the authors have received or will receive benefits for
personal or professional use from a commercial party related directly or
indirectly to the subject of this article, benefits have been or will be
received but are directed solely to a research fund, educational institution,
or other non-profit institution with which one or more of the authors is
associated.
References
1. Aronson J. Osteoarthritis of the young adult hip: etiology and
treatment. Instructional Course Lectures, AAOS 1986;36:119-28.
2. Bombelli R, Bombelli M. Dysplastic osteoarthritis of the hip. J Bone
Joint Surg [Br] 1995;77-B:(Suppl II):141.
3. Nakamura S, Ninomiya S, Nakamura T. Primary osteoarthritis of
the hip joint in Japan. Clin Orth 1989;241:190-6.
4. Stulberg SD, Harris WH. Acetabular dysplasia and development of
osteoarthritis of the hip. In: Harris WH, ed. The hip. Proceedings of
the second open scientific meeting of The Hip Society. St Louis, etc:
CV Mosby Company, 1974:82-93.
THE JOURNAL OF BONE AND JOINT SURGERY
THE MORPHOLOGY OF THE FEMUR IN DEVELOPMENTAL DYSPLASIA OF THE HIP
5. Charnley J, Feagin JA. Low-friction arthroplasty in congenital
subluxation of the hip. Clin Orthop 1973;91:98-113.
6. Crowe JF, Mani VJ, Ranawat CS. Total hip replacement in congenital dislocation and dysplasia of the hip. J Bone Joint Surg [Am]
1979;61-A:15-23.
7. Dunn HK, Hess WE. Total hip reconstruction in chronically dislocated hips. J Bone Joint Surg [Am] 1976;58-A:838-45.
8. Woolson ST, Harris WH. Complex total hip replacement for dysplastic or hypoplastic hips using miniature or microminiature components. J Bone Joint Surg [Am] 1983;65-A:1099-108.
9. Robertson D, Essinger J, Imura S, et al. Femoral deformity in adults
with developmental hip dysplasia. Clin Orthop 1996;327:196-206.
10. Yanagimoto S. Basic study of cementless hip prosthesis design:
analysis of the proximal femur in Japanese patients with osteoarthritis
of the hip. Nippon Seikeigeka Gakkai Zasshi 1991;65:731-44.
11. Noble PC, Box GG, Kamaric E, et al. The effect of aging on the
shape of the proximal femur. Clin Orthop 1995;3163:1-44.
12. Anwar MM, Sugano N, Masuhara K, et al. Total hip arthroplasty in
the neglected congenital dislocation of the hip: a five- to 14-year
follow-up study. Clin Orthop 1993;295:127-34.
13. Gorski JM. Modular noncemented total hip arthroplasty for congenital dislocation of the hip: case report and design rationale. Clin Orthop
1988;228:110-6.
14. Huo MH, Salvati EA, Lieberman JR, Burstein A, Wilson PD Jr.
Custom-designed femoral prostheses in total hip arthroplasty done
with cement for severe dysplasia of the hip. J Bone Joint Surg [Am]
1993;75-A:1497-504.
15. Jasty M, Anderson MJ, Harris WH. Total hip replacement for
developmental dysplasia of the hip. Clin Orthop 1995;311:40-5.
16. Paavilainen T, Hoikka V, Paavolainen P. Cementless total hip
arthroplasty for congenitally dislocated or dysplastic hips: technique
for replacement with a straight femoral component. Clin Orthop
1993;297:71-81.
17. Bucholz RW, Ogden JA. Patterns of ischaemic necrosis of the
proximal femur in nonoperatively treated congenital hip disease. In:
The Hip. Procs of the 6th meeting of the Hip Society, 1978. St. Louis,
etc: CV Mosby Co, 1978:43-63.
18. Someya I. Kokumin Eisei no Doukou. In: Matsuura J, ed. National
nutrition survey. Tokyo: Health and Welfare Statistics Association,
1995:467 (in Japanese).
VOL. 80-B, NO. 4, JULY 1998
719
19. Marr D, Hildreth E. Theory of edge detection. Proc R Soc Lond
1980;B207:187-217.
20. Srinivasa N, Ramakrishnan K, Rajgopal K. Detection of edges from
projections. IEEE Trans Med Imag 1992;11:76-80.
21. Sutherland C, Bresina S, Gayou D. Use of general purpose mechanical computer assisted engineering software in orthopaedic surgical
planning: advantages and limitations. Comput Med Imaging Graph
1994;18:435-41.
22. Kingsley PC, Olmsted KL. A study to determine the angle of
anteversion of the neck of the femur. J Bone Joint Surg [Am] 1948;
30-A:745-51.
23. Noble PC, Alexander JW, Lindahl LJ, et al. The anatomic basis of
femoral component design. Clin Orthop 1988;235:148-65.
24. Wiberg G. Studies on dysplastic acetabula and congenital subluxation
of the hip joint: with special reference to the complication of osteoarthritis. Acta Chir Scand 1939;83:Suppl. 58.
25. Sharp IK. Acetabular dysplasia: the acetabular angle. J Bone Joint
Surg [Br] 1961;43-B:268-72.
26. Mendes DG. Total hip arthroplasty in congenital dislocated hips. Clin
Orthop 1981;161:163-79.
27. Badgley CE. Etiology of congenital dislocation of the hip. J Bone
Joint Surg [Am] 1949;31-A:341-56.
28. Badgley CE. Correlation of clinical and anatomical facts leading to a
conception of the etiology of congenital hip dysplasia. J Bone Joint
Surg 1943;25:503-23.
29. Watanabe RS. Embryology of the human hip. Clin Orthop 1974;98:
8-26.
30. Wilkinson JA. Prime factors in the aetiology of congenital dislocation
of the hip. J Bone Joint Surg [Br] 1963;45-B:268-83.
31. Crane L. Femoral torsion and its relation to toeing-in and toeing-out.
J Bone Joint Surg [Am] 1959;41-A:421-8.
32. Fabry G, MacEwen GD, Shands AR Jr. Torsion of the femur: a
follow-up study in normal and abnormal conditions. J Bone Joint Surg
[Am] 1973;55-A:1726-38.
33. Sugano N, Saito S, Takaoka K, et al. Spongy metal Lübeck hip
prostheses for osteoarthritis secondary to hip dysplasia: a 2-6 year
follow-up study. J Arthroplasty 1994;9:253-62.
34. Holtgrewe JL, Hungerford DS. Primary and revision total hip
replacement without cement and with associated femoral osteotomy. J
Bone Joint Surg [Am] 1989;71-A:1487-95.