Download Morphology and Bony ROM of Hip Joints with Dysplasia

Morphology and Bony ROM of Hip Joints with Dysplasia
1
Nakahara, I; 1Takao, M; 1Sakai, T; 2Nishii, T; 1Yoshikawa, H; +2Sugano, N
Department of Orthopaedic Surgery, Osaka University Graduate School of Medicine, Suita, Japan
+2Department of Orthopaedic Medical Engineering, Osaka University Graduate School of Medicine, Suita, Japan
[email protected]
1
Results: The morphologic parameters of the acetabulum and femur were
shown in Table 1. The differences between the normal and dysplasia groups
were found in APP tilt, acetabular anteversion, acetabular inclination, CE
angle, and femoral neck anteversion. When the acetabular rim depth was
shown in a graph (Fig. 1), there were three valleys and three peaks. The
peaks were seen on average at the points of 45 degrees anterior, 135 degrees
anterior, and 135 degrees posterior from the acetabular top in the normal
group and at the points of 45 degrees anterior, 135 degrees anterior, and 150
degrees posterior in the dysplasia group. The average acetabular rim depth of
dysplasia group was significantly shallower than that of the normal group at
all the points.
The angles of bony impingement are shown in Table 2. The maximum
flexion and internal rotation at 90 degree flexion was significantly larger in
the dysplasia group than those of the normal group, and the maximum ranges
in the external rotation was significantly smaller in the dysplasia group.
Table 1 Results of measurements. Data shows mean ± SD. A minus value of
APP tilt meant that APP tilted backward.
Normal
Dysplasia
P value
APP tilt
-4.2±6.5
7.8±5.8
<0.05
Acetabular anteversion
21.1±7.3
26.1±6.6
<0.05
Acetabular inclination
38.7±4.3
51.6±2.8
<0.05
CE angle
37.1±8.7
6.2±5.3
<0.05
Femoral head diameter
42.8±2.3
43.8±1.9
0.07
Femoral anteversion
25.1±9.9
41.6±13.2
<0.05
Neck-Shaft angle
125.6±4.8
127.1±5.6
0.17
Angle (Degrees)
Introduction:
Hip dysplasia is a major cause of secondary osteoarthritis. Acetabular reorientation osteotomies are often performed to prevent the hip joints from
development of osteoarthritis. However, if osteotomies are simply aimed for
a sufficient femoral head coverage, unexpected acetabular version change
and too much anterior or posterior coverage may occur due to the unique
anatomy of hip dysplasia that causes impingement-induced osteoarthritis.
Therefore, it is worth studying the relationship between the morphologic
parameters of acetabulum and bony range of motion
The purpose of this study was to characteristic morphological parameters
of the dysplastic hips which relates to the bony ROM and to clarify the
differences from the normal hips.
Materials and Methods:
Computed tomography (CT) images of 31
dysplastic hip joints of 17 patients were used in this study. All of the patients
were female gender with the average age of 35.5±8.2 (range; 24 to 54) years
old. The dysplastic hip joints were with less than 15 degrees of lateral centeredge (CE) angle. CT images of 73 normal hip joints from 49 female persons
with the age of 71.7±4.6 (range; 63 to 80) years old were used as normal hip
joint geometry for comparison. There were no symptoms or no radiographic
abnormalities in their hip joints.
Using 3D viewer software (3D template; Japan Medical Materials),
multiple planar reconstruction (MPR) views through arbitrary orthogonal
three planes were reconstructed. To reconstruct standardized MPR views, the
coronal plane and the transverse plane were adjusted to include the bilateral
anterior superior iliac spines (ASIS). Then, the coronal plane was tilted until
the pubic tubercles were on the same plane with ASIS. This sagittal rotation
angle was defined as the tilt of the anterior pelvic plane (APP). Then the
orthogonal MPR views were moved to pass the center of the acetabulum,
which was defined as the center of sphere best fitted to the acetabulum. On
these views, acetabular anteversion from anterior and posterior acetabular
edges and inclination from superior and inferior edges were measured. The
orthogonal MPR views were further moved so that a plane could include
three points of anterior, superior, and posterior acetabular edges. The plane
including the three points was defined as an acetabular opening plane and a
line which was perpendicular to the plane and passed through the femoral
head center was defined as an acetabular axis. On the planes perpendicular to
the opening plane through the femoral head center, the acetabular edge angle
between the acetabular axis and a line through the femoral head center and
each acetabular edge point was measured around the acetabular rim at 15
degrees of interval from the deepest acetabular notch. In the femoral side,
femoral head diameter, femoral anteversion and neck shaft angle were
measured according to the method reported previously [1].
Additionally 3D surface models of the pelvis and femur of these
subjects were constructed from the CT images to measure ROM. The origins
of coordinate systems were consistent with the femoral head center to make it
the center of the joint motion. To turn the pelvis around the origin, the pelvic
coordinate system was created by making APP on a coronal plane with both
ASISs on an axial plane. The femoral coordinate system was referred by the
posterior condylar plane, which was including most prominent posterior
point of greater trochanter and the posterior condyles, on a coronal plane [2].
Then the bony impingement angles in flexion (Flex), extension (Ext),
external rotation (ER), and internal rotation at 90 degrees of flexion
(IR@F90) were measured.
100
90
80
70
60
Top
Ant 45 Ant 90 Ant 135 Notch Post 135 Post 90 Post 45
Acetabular location
Female
Dysplasia
Fig. 1 The acetabular rim depth was shown as a center edge angle in an
interval of 15 degrees. There were significant differences at all thelocations.
Table 2 Results of ROM. Data shows mean ± SD.
Normal
Dysplasia
Flex
125.1±10.3
138.9±12.1
Ext
54.7±20.0
51.1±23.3
ER
38.2±14.1
23.7±14.6
IR@F90
47.6±14.0
75.6±12.6
P value
<0.05
0.47
<0.05
<0.05
Discussion: The acetabulum of the dysplasia group has a larger anteversion
and inclination and a shallower rim depth than the normal acetabulum. The
femur of the dysplasia group has a larger neck anteversion than the normal
femur as reported previously [2-4]. These anatomical characteristics of hip
dysplasia leaded to larger ROM in flexion and internal rotation at 90 degree
flexion, and smaller ROM in the external rotation.
These relationship suggests that a simple lateral rotation of the acetabulum
further decrease ROM of extention and external rotation. A balanced
anterolateral rotation of the acetabulum is needed in acetabular re-orientation
osteotomies for hip dysplasia.
References:
1.
Sugano N et al. J Comput Assist Tomogr 1998
2.
Sugano N et al. J Bone Joint Surg Br 1998
3.
Noble PC et al. Clin Orthop Relat Res 2003
4.
Murphy SB et al. Clin Orthop Relat Res. 1990
Poster No. 2006 • 56th Annual Meeting of the Orthopaedic Research Society