AJR 2004; 182:1363-1366
© American Roentgen Ray Society
Acetabular Fractures Revisited: Part I, Redefinition of the Letournel Anterior Column
John H. Harris, Jr.1,2,
Jody S. Lee1,3,
Kevin J. Coupe4 and
Thea Trotscher4
1 Department of Radiology, University of Texas-Houston Medical School, 6431
Fannin, Houston, TX 77030.
2 Present address: 200 Alta Vista Dr., Sedona, AZ 86351.
3 Present address: 2019 Red Magnolia Ct., Kingwood, TX 77339.
4 Department of Orthopaedic Surgery, University of Texas-Houston Medical School,
Houston, TX.
Received February 24, 2003;
accepted after revision November 25, 2003.
Address correspondence to J. H. Harris, Jr.
(jhharris{at}myexcel.com).
Abstract
OBJECTIVE. The objective of part 1 of this study is to redefine the
Letournel anterior column on the basis of developmental and adult pelvic
skeletal anatomy.
MATERIALS AND METHODS. The axial CT scans of 112 randomly selected
patients with acetabular fracture or fracture-dislocations admitted to a level
I trauma center between January 1998 and December 2000 were analyzed by an
experienced orthopedic trauma surgeon and two experienced emergency
radiologists. When available, 3D reformatted images were analyzed as well. The
discrepancy between the Letournel definition of the anterior and posterior
columns became readily apparent. Standard text books of anatomy and surgical
anatomy were referenced relative to the embryologic and adult components of
the acetabulum.
RESULTS. The anterior column is redefined with its superior border
being the anatomic arcuate and iliopectineal lines, thereby coinciding with
the superior border (arcuate line) of the Letournel posterior column.
CONCLUSION. Redefinition of the anterior column eliminates
diagnostic ambiguity of the Letournel elementary anterior column fracture as
well as the Letournel associated anterior column or wall with hemitransverse
fracture. The redefined anterior column is integral to the CT-based
classification described in part 2 of our study.
Introduction
The two-column concept and the definition of the anterior and posterior
columns of Judet and Letournel
[1–4]
remain the basis for describing acetabular fractures today.
In a study of 112 patients with acetabular fractures, a major discrepancy
in the anatomic definition of the anterior column with respect to that of the
posterior column became apparent.
The purpose of this report is to redefine the anterior column, making it
anatomically comparable to the Letournel posterior column. This
anatomically-correct definition of the anterior column of the acetabulum is a
key element of the CT-based reclassification of acetabular fractures described
in part 2 of "Acetabular Fractures Revisited."
Materials and Methods
The complete set of axial CT scans of 112 randomly selected patients
admitted to a level I trauma center from January 1, 1998, to December 14,
2000, with the diagnosis of acetabular fracture or fracture-dislocation
constitutes the data for this study. Axial CT scans of the entire pelvis were
obtained on either a CTi helical or LightSpeed MDCT scanner (General Electric
Medical Systems). Axial images were printed at consecutive 5-mm levels from
the iliac crest to the acetabular roof and in consecutive 3-mm increments
through the acetabulum to the ischial tuberosity.
The anterior and posterior columns, as seen on a mid acetabular axial CT
scan, were defined by a line representing the mid coronal plane of the
acetabulum (Fig. 1).
The acetabular walls ("rims" or "lips") are an
integral component of the columns. A search of English-language literature
failed to produce any reference in which the acetabular walls were defined
either anatomically or as seen on axial CT scans. Therefore, the wall
component of the columns, as seen on a mid acetabular CT scan, was defined by
an imaginary line connecting the anterior and posterior margins of the
articulating (lunar) surface of the acetabulum
(Fig. 1). (We subsequently
became aware of a similar definition
[5].) That portion of the
acetabulum lateral to the line b–b1 was designated
"wall" and that medial to the line, "column."
The Letournel and Judet [4]
definition of the anterior and posterior columns
(Fig. 2), endorsed by others
[6–9],
is inconsistent because, although the posterior column is limited superiorly
by the arcuate line, the anterior column extends above the arcuate line to the
iliac crest. Anatomically [10]
and clinically
[11–13],
the acetabulum is confined to the "true" pelvis. This concept is
further supported by the fact that the quadrilateral plate (the lateral wall
of the birth canal) is the medial wall of the acetabulum.
On the basis of the relationship of the roof of the acetabulum to the
anatomic arcuate–iliopectineal line
(Fig. 3) and axial CT scans of
the supraacetabulum (Fig. 4),
we define the superior extent of the anterior column as coinciding with the
ventral portion of the arcuate line and its contiguous iliopectineal line
anteromedial to the iliopectineal eminence (Figs.
3 and
5). This concept is further
supported by the developmental anatomy of the acetabulum
(Fig. 5), which shows the pubic
bone component of the acetabulum to coincide with our concept of the anterior
column of the acetabulum.
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Fig. 4. —Axial CT scan shows column anatomy of iliac base. Image of
pelvic skeleton was superimposed on CT scout view of patient's pelvis from
which axial images were obtained. Left midhemi acetabular axial CT scan is
shown for reference purposes. Axial CT supraacetabular images a–d show
axial CT anatomy of iliac base. Anterior column is indicated by gray arrow;
iliopectineal line, by white arrow; and posterior column, by black arrow. W =
wall.
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Fig. 5. —Schematic representation shows ossification centers of
innominate bone of 8-year-old child. That portion of triradiate cartilage
separating pubic bone from ilium and ischium (arrowheads) identifies
division between anterior and posterior columns. In essence, pubic bone,
including its iliopectineal eminence (arrow), constitutes anterior
column. (Reprinted from
[14])
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The arcuate line is the sharp crest
[10] at the base of the iliac
wing on the inner surface of the innominate bone
(Fig. 3), which separates the
false (greater) from the true (lesser) pelvis. The arcuate line extends from
the sacroiliac joint to the iliopectineal eminence
(Fig. 3). That portion of the
arcuate line that separates the false from the true pelvis defines the
superior extent of both the anterior and posterior columns
(Fig. 3).
The ventral extension of the arcuate line from the iliopectineal eminence
to the pubic tubercle is the anatomic iliopectineal line
[10]
(Fig. 3). The anatomic arcuate
and iliopectineal lines constitute the radiographic iliopectineal line
(Fig. 6).
The superomedial margin of the anterior column crosses the anterior portion
of the quadrilateral plate in an obliquely anteroinferior course to enter the
obturator foramen at the level of the obturator crest. The latter lies
immediately posterior to the acetabular notch
(Fig. 7A). The superolateral
margin of the anterior column extends in an oblique inferolateral direction
from the arcuate line across the superior surface of the iliac body
(Fig. 7A) to enter the
acetabular fossa between the anterior inferior spine and the iliopectineal
eminence (Fig. 7B). The margin
of the anterior column then traverses the acetabular fossa inferomedially to
exit through the acetabular notch (Figs.
7B and
7C). Thus, the anterior column
includes approximately the anterior one fifth of the quadrilateral plate (Fig.
7A,
7B,
7C). Our definition of the
anterior column is supported by the relationship of the developing pubic bone
to the ilium and ischium (Fig.
5).
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Fig. 7A. —Anatomically defined anterior column of acetabulum.
Arrowheads indicate anterior inferior iliac spine; curved arrows,
iliopectineal eminence; and straight arrows, pubic tubercle. Schematic
representation shows anatomically redefined anterior (dotted area)
and Letournel-defined posterior (striped area) column in internal
projection.
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Fig. 7B. —Anatomically defined anterior column of acetabulum.
Arrowheads indicate anterior inferior iliac spine; curved arrows,
iliopectineal eminence; and straight arrows, pubic tubercle. Schematic
representation shows anatomically redefined anterior (dotted area)
and Letournel-defined posterior (striped area) columns in obturator
oblique projection.
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Fig. 7C. —Anatomically defined anterior column of acetabulum.
Arrowheads indicate anterior inferior iliac spine; curved arrows,
iliopectineal eminence; and straight arrows, pubic tubercle. Schematic
representation shows anatomically redefined anterior (dotted area)
and Letournel-defined posterior (striped area) columns in lateral
projection.
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To relate the axial images of the supraacetabular portion of the ilium to
the anatomy of the innominate bone and therefore identify the anatomy of these
images, we took a digital photograph of a model of an adult pelvis and
electronically superimposed it on the lateral scout view of a living subject
in recumbency. Axial images at arbitrarily selected slice levels of the
supraacetabulum from the in vivo scan were printed alongside the photograph of
the pelvic specimen with the axial image level indicated on the photograph
(Fig. 4). The radiographic
iliopectineal line and the anterior and posterior columns were identified on
the selected axial images. From the bottom up, the anterior column is shown
anterior to and the posterior column, posterior to the radiographic
iliopectineal line (Fig. 4).
This unfamiliar concept is better understood by observing the confluence of
the iliopectineal (anterior column) and the ischiopectineal (posterior column)
lines on Figure 6.
Results
The anatomically based redefinition of the anterior column results in the
superior extent of each column being comparable and being defined by the
arcuate line and limiting the anterior column to the true pelvis.
Discussion
Letournel's first description of the anterior column extending to the iliac
crest [1] remains the
recognized and accepted definition today. However, the Letournel definition of
the anterior column leads to ambiguity in diagnosis. For example, a Letournel
"elementary" anterior column fracture could be confined to the
anatomic anterior column of the acetabulum, whereas the same Letournel
fracture type would apply to an anterior column fracture with extension into
the iliac wing.
Similar ambiguity can apply to the Letournel associated fracture, anterior
column or wall with hemitransverse, which could either be confined to the
anatomic acetabulum or have superior extension into the iliac wing.
Redefinition of the Letournel anterior column by limiting its superior
extent to the arcuate-iliopectineal line confines each column to the anatomic
acetabulum. This concept justifies fractures limited to the acetabulum itself,
such as wall, single-column, and some dual-column (Letournel transverse)
fractures.
Redefining the superior extent of the anterior column to coincide with that
of Letournel's posterior column provides a cognitive rationale for two-column
fractures with inferior extension (Letournel T-shaped and its variants),
superior extension (into the iliac wing), or simultaneous superior and
inferior extension.
Finally, the anatomically redefined anterior column is integral to the
CT-based classification of acetabular fractures described in part 2 of this
presentation.
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Abstract
Introduction
