*Work performed at the Hip Group, Orthopedics and Traumatology Department, Irmandade Santa Casa de Misericórdia, Faculdade de Ciências Médicas da Santa Casa de São Paulo (FCMSCSP), São Paulo, SP, Brazil.
ABSTRACT:
OBJECTIVE The purpose of the present paper is to compare the equivalence of the measurement
of
the alpha angle using the Ducroquet and cross-table lateral views. METHODS We have recruited 90 patients, resulting in 95 hips. We have standardized the
realization of the radiographic views. The incidence of the lateral cross-table views
were taken with 15º of internal rotation with the patient in the supine position,
and
the incidence of the Ducroquet views was standardized with the patient in the supine
position, with 90º of flexion and 45º of abduction of the hip. The alpha angle was
measured in both lateral views, by two musculoskeletal radiologists. The measurements
were performed in 2 different times: an initial evaluation and another 4 weeks
afterwards. The t Student test was used and calculated the intraclass correlation
coefficient (ICC). RESULTS We have found a good intraobserver correlation for both views in different times;
there
was no statistically significant difference between the measurements performed by
the
two views. However, the interobserver correlation was low. CONCLUSION In conclusion, the Ducroquet profile view is a good choice for the α angle measurement
and can be used instead of the cross-table view.
OBJETIVO O objetivo do presente trabalho é comparar a equivalência da medida do ângulo alfa
do
quadril usando as incidências laterais de Ducroquet e de cross-table. MÉTODO Estudamos 90 pacientes, com um total de 95 quadris, e padronizamos a realização das
radiografias conhecidas como “Ducroquet” e “cross-table.” A incidência de perfil de
cross-table foi realizada em 15º de rotação interna com o paciente em posição supina,
e
a incidência de perfil de Ducroquet foi padronizada com o paciente posicionado em
decúbito dorsal, em 90º de flexão e 45º de abdução do quadril. O ângulo alfa foi medido
em ambas as radiografias de perfil, por dois radiologistas especializados em afecções
musculoesqueléticas. As medidas foram realizadas em 2 épocas diferentes: uma avaliação
inicial e outra após 4 semanas. O teste t de Student foi utilizado e calculou o
coeficiente de correlação intraclasse (CCI). RESULTADOS Encontramos boa correlação intraobservador para ambas as incidências radiográficas
em
diferentes momentos. Não houve diferença estatisticamente significante entre as medidas
feitas pelas duas visualizações. No entanto, a correlação interobservadores foi
baixa. CONCLUSÃO A incidência radiográfica de perfil de Ducroquet é uma boa opção para a medida do
ângulo alfa e pode ser usada ao invés da incidência radiográfica de perfil
cross-table.
Palavras-chave: impacto femoroacetabular; quadril/anormalidades; quadril/diagnóstico por imagem; radiografia.
FIGURES
Citation: Polesello GC, Queiroz MC, Ricioli Junior W, Rudelli M, Nunes MAA, Amaral DT. Comparative Evaluation of Cross-table and Ducroquet Incidences for
Measurement of the Hip Alpha Angle*. 54(4):428. doi:10.1055/s-0039-1693044
Note:
*
Work performed at the Hip Group, Orthopedics and Traumatology Department, Irmandade
Santa
Casa de Misericórdia, Faculdade de Ciências Médicas da Santa Casa de São Paulo (FCMSCSP),
São Paulo, SP, Brazil.
Received: March 05 2019; Accepted: January 22 2019
INTRODUCTION
Femoroacetabular impingement (FAI) is a well-established entity in world orthopedics.1-6 It is
considered one of the main mechanically originated processes resulting in hip
arthrosis.1,3,4,6-9 Its
diagnosis is aided by well-defined radiographic parameters.2,4,10 Most of the morphological alterations of this
condition are not visible in anteroposterior hip radiographies.2-4 Profile views
demonstrate better the nonspherical portion of the femoral neck and the deformities
caused
by FAI.8,9,11-13
This nonspherical portion of the femoral head-neck joint can be measured with the
alpha
angle (Nötzli angle).8,12 The alpha angle is formed by a line drawn through the
center of the femoral head, following the femoral neck axis, and another line connecting
the
center of the femoral head to the point where the femoral head protrudes beyond a
circle
drawn around the femoral head (the point where the femoral head sphericity ends).8,12 In
its original description, the angle was measured on oblique axial magnetic resonance
imaging
(MRI).
Several profile views were described to investigate femoral neck abnormalities, but
the
most commonly used is the cross-table view.5,6,14 The Ducroquet profile view is another option, easy to
perform regardless of the table and requiring only 90º flexion and 30º to 45º
abduction.12 Since it is technically easy,
including intraoperatively during hip arthroscopy, it is our imaging of choice to
evaluate
the alpha angle.
The present study aims to compare the equivalence of the measurement of the alpha
angle
using the Ducroquet and cross-table views.
MATERIALS AND METHODS
This is a prospective study performed at the Department of Orthopedics and Traumatology
of
at Santa Casa de Misericórdia de São Paulo Medical School from January 2008 to April
2010. A
total of 90 patients were recruited, resulting in 95 hips, which were voluntarily
selected
and radiographed in the Ducroquet and cross-table views. Informed consent was obtained
from
all of the patients, and the study was approved by the Institutional Review Board
under the
number 240/09.
Radiographies
The radiographic views were standardized. All of the views were performed by the same
technicians, using the same technique, and were supervised by an orthopedist. The
cross-table view (Figs. 1A and 1B) was obtained with the patient in the supine position, with the
studied lower limb in 15º internal rotation and the contralateral limb in 90º flexion
to
avoid image interposition, as recommended by the technique, whereas the Ducroquet
view
(Figs. 1C and 1D) was standardized with the patient in dorsal recumbency, 90º flexion, and 45º
abduction of the affected hip, in neutral rotation.
Fig. 1. (A and B). Cross-table view positioning;
(C and D). Ducroquet view positioning.
Fig. 1. (A and B). Cross-table view positioning; (C and D). Ducroquet view positioning.
Radiographic Measurement
The alpha angle (Nötzli angle)8,12 was determined on both profile views by two
musculoskeletal radiologists using the same measurement techniques.8,13 The angle was
measured digitally with the Image software, version 1.37 (National Institutes of Health,
Bethesda, MD, USA).
The measurements were performed at two different time points: at the initial evaluation
(referred as “pre”) and 4 weeks afterwards (referred as “post”). The statistical analysis
was performed with a summary of variables, boxplot graphs, and scatter diagrams. The
Student t-test was used, and the intraclass correlation coefficient (ICC) was calculated
with PASW Statistics for Windows, Version 10.0 (SPSS Inc., Chicago, IL, USA). The
level of
significance was determined at 0.05 (5%).
RESULTS
The measurements of the alpha angle were similar for both observers at the two time
points,
that is, at baseline and after 4 weeks (Fig. 2 and
Table 1).
Fig. 2. Boxplot graph of hip angle measurements made by two different observers in two
different views (Ducroquet and Cross-table) and two different time points (pre and
post). Pre: Initial measurements. Post: measurements after 4 weeks. CT: Cross-Table
view. DC: Ducroquet view. Obs1: Observer 1. Obs2: Observer 2.
Fig. 2. Boxplot graph of hip angle measurements made by two different observers in
two different views (Ducroquet and Cross-table) and two different time points (pre
and post). Pre: Initial measurements. Post: measurements after 4 weeks. CT: Cross-Table
view. DC: Ducroquet view. Obs1: Observer 1. Obs2: Observer 2.
Table 1. Radiographic measurements of the alpha angle of the hip by two different observers
with two different views (Ducroquet and cross-table) and two different times (pre
and
post)
Observer
Radiographic View
Time
Mean (º) ± SD
Median (º)
1
Cross-Table
pre
49.8 ± 7.43
50.1
post
49 ± 7.31
48.5
1
Ducroquet
pre
50.2 ± 8.32
49.8
post
48 ± 7.89
48.2
2
Cross-Table
pre
44.9 ± 9.77
42.3
post
45.4 ± 8.68
45.5
2
Ducroquet
pre
45.2 ± 9.22
45.2
post
44.9 ± 7.88
44.4
Abbreviations: post, measurements after 4 weeks; pre, initial measurements; SD,
standard deviation.
Table 1. Radiographic measurements of the alpha angle of the hip by two different
observers with two different views (Ducroquet and cross-table) and two different times
(pre and post)
The following analysis was performed:
To compare the results from observers 1 and 2 for each radiographic view in the
1st and 2nd evaluation (pre and post).
Regarding the analysis among observers:
A.1) Cross-table: there was a disparity between the observers 1 and 2 at the
pre-evaluation (Table 2 and Fig. 3A) and at the postevaluation (Table 2 and Fig.
3B).
Table 2. Intraclass correlation coefficients of the measurements the alpha angle
of the hip by two observers at the cross-table and Ducroquet views
Table 2. Intraclass correlation coefficients of the measurements the alpha angle of
the hip by two observers at the cross-table and Ducroquet views
Fig. 3. (A) Correlation of the initial measurements of the alpha
angle of the hip made by two different observers with the cross-table view.
Pre: initial measurements; (B) Correlation of the 2nd
measurements of the alpha angle of the hip made by 2 different observers with
the cross-table view. Post: measurements after four weeks; (C)
Correlation of the initial measurements of the alpha angle of the hip made by
two different observers with the Ducroquet view. Pre: initial measurements;
(D) Correlation of the 2nd measurements of the alpha
angle of the hip made by 2 different observers with the Ducroquet view. Post:
measurements after 4 weeks.
Fig. 3. (A) Correlation of the initial measurements of the alpha angle of the hip
made by two different observers with the cross-table view. Pre: initial measurements;
(B) Correlation of the 2nd measurements of the alpha angle of the hip made by 2 different
observers with the cross-table view. Post: measurements after four weeks; (C) Correlation
of the initial measurements of the alpha angle of the hip made by two different observers
with the Ducroquet view. Pre: initial measurements; (D) Correlation of the 2nd measurements
of the alpha angle of the hip made by 2 different observers with the Ducroquet view.
Post: measurements after 4 weeks.
A.2) Ducroquet: there was disparity between observers 1 and 2 at the pre-evaluation
(Table 2 and Fig. 3C) and at the postevaluation (Table
2 and Fig. 3D).
There was a statistically significant difference (p = 0.000) between
measurements between observers for both incidences at both time points.
To compare the correlation of the measurements of the cross-table and Ducroquet views
for each observer at both time points.
B.1) There was little disparity between observers 1 and 2 in the measurements of
the hip angles in both views at the same time (Table
2 and Fig. 4A): observer 1,
1st measurement; Table 2 and
Fig. 4B: observer 1, 2nd
measurement; Table 2 and Fig. 4C: observer 2, 1st measurement; Table 2 and Fig.
4D: observer 2, 2nd measurement.
Fig. 4. (A) Correlation of the initial measurements of the alpha
angle of the hip made by observer 1 with the cross-table and Ducroquet views.
Pre: Initial measurements. Obs1: observer 1; (B) Correlation of
the 2nd measurements of the alpha angle of the hip made by observer
1 with the cross-table and Ducroquet views. Post: measurements after 4 weeks.
Obs1: observer 1; (C) Correlation of the initial measurements of
the alpha angle of the hip made by the observer 2 with the cross-table and
Ducroquet views. Pre: Initial measurements. Obs2: observer 2; (D)
Correlation of the 2nd measurements of the alpha angle of th hip made by the
observer 2 with the cross-table and Ducroquet views. Post: measurements after
4 weeks. Obs2: Observer 2.
Fig. 4. (A) Correlation of the initial measurements of the alpha angle of the hip
made by observer 1 with the cross-table and Ducroquet views. Pre: Initial measurements.
Obs1: observer 1; (B) Correlation of the 2nd measurements of the alpha angle of the
hip made by observer 1 with the cross-table and Ducroquet views. Post: measurements
after 4 weeks. Obs1: observer 1; (C) Correlation of the initial measurements of the
alpha angle of the hip made by the observer 2 with the cross-table and Ducroquet views.
Pre: Initial measurements. Obs2: observer 2; (D) Correlation of the 2nd measurements
of the alpha angle of th hip made by the observer 2 with the cross-table and Ducroquet
views. Post: measurements after 4 weeks. Obs2: Observer 2.
There was no statistically significant difference (p > 0.05) in the
alpha angle measured on both radiographic views by the same observer at the same time
(Table 3).
Table 3. Intraobserver analysis of the measurements of the alpha angle of the hip at two
different views (Ducroquet and cross-table) and two different times (pre and
post)
Analysis
p-value
1
Cross-table (Obs1 pre) - Ducrocquet (Obs1 pre)
0.309
2
Cross-table (Obs2 pre) - Ducrocquet (Obs2 pre)
0.611
3
Cross-table (Obs1 post) - Ducrocquet (Obs1 post)
0.699
4
Cross-table (Obs2 post) - Ducrocquet (Obs2 post)
0.223
Abbreviations: post, measurements after 4 weeks; pre, initial measurements; Obs1,
Observer 1; Obs2, Observer 2.
Table 3. Intraobserver analysis of the measurements of the alpha angle of the hip
at two different views (Ducroquet and cross-table) and two different times (pre and
post)
DISCUSSION
Comparing the measurement of the alpha angle by two observers using the Ducroquet
and
cross-table radiographic views, we observed good intraobserver correlation, but low
interobserver correlation.
The diagnosis of the subtle changes that may cause early hip coxarthrosis is evolving
in
the last few years.15 Radiographs are valuable for
the detection of femoral and acetabular morphological changes.4,11,12
The alpha angle (Nötzli angle) is often used to diagnose pathological deformities
of the
femoral neck.6,8,12,13,16
There are controversies as to the ideal view for alpha angle measurement. Meyer et
al13 compared 6 radiographic views (anteroposterior, Dunn,
Dunn with 45º of flexion, cross-table with 15º of internal rotation, cross-table in
neutral
rotation, and cross-table with 15º of external rotation). They concluded that the
Dunn view
at 45º or 90º of flexion or the cross-table view with internal rotation are better
at
detecting changes in the sphericity of the femoral head-to-neck transition; in addition,
the
authors noted that the anteroposterior and cross-table views with external rotation
are not
able to detect these changes.
The Ducroquet view is easy to perform and represents the true profile of the proximal
femoral end, perfectly showing the transition between the neck and the femoral head.11,12
Moreover, this view is useful for intraoperative control during femoral osteoplasty,
since
it allows obtaining profile images without moving the fluoroscopy arm.
The cross-table profile technique also provides a true view of the femoral neck; in
addition, it allows the visualization of the accessory acetabulum. However, it is
technically more demanding because the imaging tube must be mobile. It also requires
an
orthopedic table that does not interfere with the height of the tube.11,12 Many orthopedic
centers in Brazil do not have the mobile X-ray equipment or a suitable orthopedic
table
required for this view.
There was a statistically significant difference (p = 0.00) for the
interobserver measurements with both views and at both time points.
The mean measurements of observer 2 were lower compared with all of the measurements
from
observer 1; this finding may be due to subtle differences in the measurement techniques
from
both observers.
There was a good intraobserver correlation for both incidences at the 2 time points;
moreover, there was no statistically significant difference (p = 0.309,
p = 0.611, p = 0.699, p = 0.223)
between the measurements obtained in both views.
The analysis of radiographic parameters obtained at different moments has already
been
reported in the literature.1,13 Meyer et al13
showed that the use of cross-table and Dunn views by positioning limbs at 45º and
90º
(similar to the Ducroquet view) resulted in a better reproduction of alpha angle
measurements.
In our study, the measurement of the alpha angle was dependent on the observer. However,
this disparity usually does not exist when the same observer performs different measures
over a given time.
One of the limitations of our work was the difficulty in obtaining cross-table views
in
obese patients, since, at that time, we only had conventional X-ray equipment. The
recent
availability of digital X-ray equipment made it easier to obtain these images in these
patients. The difficulty in obtaining cross-table views may be due to the standardization
of
the Ducroquet view in our hospital as the radiographic incidence of choice to visualize
the
hip profile. Another limitation was the analysis by only two radiologists as observers.
Given these results, we believe that the Ducroquet radiographic view is a good option
for
alpha angle measurement, and that it can be the profile of choice since it is easily
performed during hip arthroscopies without moving the fluoroscopy arm.
CONCLUSION
We conclude that the measurement of the alpha angle using the cross-table or Ducroquet
view
is equivalent.
ACKNOWLEDGMENT
We are grateful to Prof. Daniel K. Scheffer for providing the statistical analysis.
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1 Hip Group, Orthopedics and Traumatology Department, Faculdade de Ciências Médicas da Santa Casa de São Paulo (FCMSCSP), Irmandade Santa Casa de Misericórdia, São Paulo, SP, Brazil 2Radiology Service, Hospital Sírio Libanês, São Paulo, SP, Brazil
1 Hip Group, Orthopedics and Traumatology Department, Faculdade de Ciências Médicas da Santa Casa de São Paulo (FCMSCSP), Irmandade Santa Casa de Misericórdia, São Paulo, SP, Brazil 2Radiology Service, Hospital Sírio Libanês, São Paulo, SP, Brazil
1 Hip Group, Orthopedics and Traumatology Department, Faculdade de Ciências Médicas da Santa Casa de São Paulo (FCMSCSP), Irmandade Santa Casa de Misericórdia, São Paulo, SP, Brazil 2Radiology Service, Hospital Sírio Libanês, São Paulo, SP, Brazil
1 Hip Group, Orthopedics and Traumatology Department, Faculdade de Ciências Médicas da Santa Casa de São Paulo (FCMSCSP), Irmandade Santa Casa de Misericórdia, São Paulo, SP, Brazil 2Radiology Service, Hospital Sírio Libanês, São Paulo, SP, Brazil
1 Hip Group, Orthopedics and Traumatology Department, Faculdade de Ciências Médicas da Santa Casa de São Paulo (FCMSCSP), Irmandade Santa Casa de Misericórdia, São Paulo, SP, Brazil 2Radiology Service, Hospital Sírio Libanês, São Paulo, SP, Brazil
Giancarlo Cavalli Polesello, MD, PhD, Rua Dr. Cesário Mota Júnior, 112, Bairro Vila Buarque, São Paulo, SP, 01221-020, Brazil (e-mail: dot.quadril@hotmail.com).
Polesello, GC, Queiroz, MC, Ricioli, W, Rudelli, M, Nunes, MAA, Amaral, DT. Comparative Evaluation of Cross-table and Ducroquet Incidences for Measurement of the Hip Alpha Angle*. Rev Bras Ortop.. 54(4):428-433. DOI: 10.1055/s-0039-1693044
