![Relative roll and pitch angles: (a) conventional group according to Graf’s sonographic criteria [8], (b) guidance system assisted group in which the developed system was used to optimize relative transducer position in addition to Graf’s criteria [10].](https://www.researchgate.net/publication/387157283/figure/fig2/AS:11431281300150813@1735346956469/Relative-roll-and-pitch-angles-a-conventional-group-according-to-Grafs-sonographic_Q320.jpg)
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Citation: Heisinger, S.; Chiari, C.;
Willegger, M.; Windhager, R.; Kolb, A.
Clinical Evaluation of an Electronic
Guidance System for Optimizing the
Ultrasound Screening for
Developmental Hip Dysplasia in
Newborns. J. Clin. Med. 2024,13, 7656.
https://doi.org/10.3390/
jcm13247656
Received: 25 November 2024
Revised: 10 December 2024
Accepted: 13 December 2024
Published: 16 December 2024
Copyright: © 2024 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
Article
Clinical Evaluation of an Electronic Guidance System for
Optimizing the Ultrasound Screening for Developmental Hip
Dysplasia in Newborns
Stephan Heisinger, Catharina Chiari, Madeleine Willegger , Reinhard Windhager * and Alexander Kolb
Department of Orthopedics and Trauma Surgery, Medical University of Vienna, 1090 Vienna, Austria;
stephan.heisinger@meduniwien.ac.at (S.H.); madeleine.willegger@meduniwien.ac.at (M.W.)
*Correspondence: reinhard.windhager@meduniwien.ac.at
Abstract: Background: Graf ultrasound screening is considered an established method for early
detection of developmental dysplasia of the hip (DDH). Although characterized by a high degree
of standardization to allow for good reproducibility of results, examination-related factors may still
affect sonographic measurements. The relative tilt angle between the hip and the probe is a potential
pitfall as it significantly influences sonographic measurements and consequently classification of
DDH according to Graf. Objectives: Evaluation of an electronic guidance system developed to
reduce relative tilt angles and increase reliability and comparability in ultrasound screening of DDH.
Materials and Methods: Twenty-five newborns were examined using a prototype guidance system,
which tracks the position of the transducer and the pelvis to calculate the relative tilt angles. Two
ultrasound images were obtained, one conventionally and the other one using the guidance system.
Subsequently, relative roll and pitch angles and sonographic measurements were determined and
analyzed. Results: The relative inclination angles in the conventional group ranged from
−
12.6
◦
to 14.3
◦
(frontal plane) and
−
23.8
◦
to 32.5
◦
(axial plane). vs.
−
3.7
◦
to 3.0
◦
and
−
3.2
◦
to 4.5
◦
in the
guidance system group. The variances were significantly lower in the guidance system-assisted group
for both planes (p< 0.001 and p< 0.001, respectively). The optimized transducer position showed
significant effects and consequently significantly reduced alpha angles were observed (p= 0.001,
and p= 0.003). Conclusions: The guidance system allowed a significant reduction in the relative
tilt angles, supporting optimal positioning of the transducer, resulting in significant effects on Graf
sonographic measurements. This technique shows great potential for enhancing the reproducibility
and reliability of ultrasound screening for DDH.
Keywords: hip dysplasia; hip ultrasound; innovative 3D navigation; population health screening
1. Introduction
Developmental Dysplasia of the hip (DDH) is a developmental disorder that can
result in various abnormalities of the hip joint such as neonatal instability of the hip joint,
acetabular of femoral dysplasia, and hip subluxation and dislocation [
1
,
2
]. DDH may be iso-
lated, but can also be found with concomitant defects such as clubfoot, torticollis, or other
spine-related or neuromuscular disorders or diseases such as Down’s syndrome [
3
,
4
]. Tao
et al. reported a pooled prevalence of DDH—resulting from 65 primary studies—to be 1.4%;
however the studies showed great variances with regard to reported prevalence, which
can be attributed to the varying regional incidence rates and screening programs [
2
,
5
]. As
reviewed by Vaquero-Picado et al., risk factors for DDH are breech presentation, family his-
tory, female gender, oligohydramnios, elevated weight at birth, multiple pregnancy, left hip,
hyperlaxity and clubfoot deformity [
6
]. As reviewed by Harsanyi et al., various genes and
epigenetic modifications were found to be associated with DDH [
7
]. Graf ultrasound screen-
ing is widely considered the gold standard for early detection of developmental dysplasia
of the hip in newborns [8–10]. This approach is defined by a high level of standardization
J. Clin. Med. 2024,13, 7656. https://doi.org/10.3390/jcm13247656 https://www.mdpi.com/journal/jcm
J. Clin. Med. 2024,13, 7656 2 of 9
in the sonographic examination, ensuring reliable reproducibility of results [
11
,
12
]. The
classification is based on standardized measurement of the
α
-angle-angle between the bony
acetabular roof and the vertical cortex of the ilium—and the
β
-angle-angle between the line
drawn between the turning point and the center of the labrum—resembling the cartilage
roof line—and the vertical cortex of the ilium [
13
]. While the
α
-angle is an indicator for
bony femoral head coverage, the
β
-angle is used to evaluate femoral head cartilaginous
coverage [
2
,
13
,
14
]. If DDH persists or is not detected early at all it results in altered biome-
chanics of the hip and overloading articular cartilage and consequently it may lead to early
osteoarthritis of the hip [
6
]. DDH can be classified into four types according to Graf, where
Type I resembles a normal hip (
α
> 60
◦
,
β
< 55
◦
), Type II (43
◦
<
α
< 60
◦
, 55
◦
<
β
< 77
◦
) a
dysplastic hip or a hip with delayed ossification, Type III (
α
< 43
◦
,
β
> 77
◦
) resembles a
subluxated hip, and Type IV (α< 43◦,βcannot be measured) a dislocated hip [2,13].
Overall, it is estimated that up to 9.1% of all total hip replacement (THR) cases can
be attributed to DDH, and it is the main cause of THR in young patients (approximately
21% to 29%) [
6
,
15
,
16
]. Taking this into consideration, the relevance of screening for DDH
in regard to the potential socioeconomic burden is highlighted. Although clinical screen-
ing is widely recommended, there is no international consensus on hip ultrasound as
a screening tool
[17–20]
. As reviewed by Kilsdonk et al., the lack of consensus leads to
considerable variation in regard to screening programs across the world [
17
]. Overall there
are few high-quality studies that compare the various screening programs; however, two
studies from Austria and Germany were able to show a decrease in surgery rates and
complications as well as a reduction in costs since the introduction of universal ultrasound
screening
[17,21,22]
. Considering that the high efficiency of non-operative treatment when
DDH is detected early, this highlights the relevance of screening programs, consequently
reducing the rate of surgical interventions and the resulting socioeconomic burden [23].
Despite all of the efforts to standardize ultrasound screening for DDH, examination-
related factors have been discussed that might affect sonographic measurements unfavor-
ably and result in overestimated incidence rates of DDH [
24
]. When it comes to examination-
related errors, the relative tilt angle between the hip being examined and the ultrasound
probe is a critical factor, as shown by Jaremko et al. through the use of 3D ultrasound
imaging [
25
]. So far, this issue has primarily been addressed using tools like a mechanical
transducer guiding device and a baby positioning aid (cradle) [26].
An analysis of the effects of relative tilt angles between the hip joint and transducer
on Graf’s method using an optoelectronic motion capture system demonstrated a highly
significant effect on sonographic measurements and, furthermore, on Graf’s DDH clas-
sification [
27
]. However, the optoelectronic motion capture system used was unable to
determine the position of the newborn’s hip or pelvis, which is a significant limitation since
the position of the hip or pelvis is crucial for calculating the relative tilt angles [
27
]. To
overcome this limitation, the development of the system used here was started [10].
This study aimed to assess the effectiveness of a new electronic navigation system in
reducing examiner-related errors in the relative tilt angle between the ultrasound trans-
ducer and the examined hip joint. It also analyzed the system’s impact on sonographic
measurements compared to traditional ultrasound screening based on Graf’s method.
2. Materials and Methods
The study received approval from the Institutional Review Board of the Medical
University of Vienna (Ethical vote: EK-No: 1414/2012, dated 24 April 2015) and was
conducted in compliance with applicable guidelines and regulations [
10
]. Informed consent
was obtained from all legal guardians prior to participation.
An electronic guidance system was developed at our institution to determine relative
tilt errors between the transducer and the hip joint under examination [
10
]. This electronic
system utilizes two position sensors: one is mounted on the ultrasound transducer with
a 3D-printed adapter, while the other is placed epicutaneously in a central position on
the back, dorsal to the sacrum (see Figure 1) [
10
]. The two position sensors consist of a
J. Clin. Med. 2024,13, 7656 3 of 9
combination of accelerometer, gyroscope and magnetometer (MPU-9250, InvenSense Inc.,
San Jose, CA, USA) as described previously [10].
J. Clin. Med. 2024, 13, x FOR PEER REVIEW 3 of 9
system utilizes two position sensors: one is mounted on the ultrasound transducer with a
3D-printed adapter, while the other is placed epicutaneously in a central position on the
back, dorsal to the sacrum (see Figure 1) [10]. The two position sensors consist of a com-
bination of accelerometer, gyroscope and magnetometer (MPU-9250, InvenSense Inc., San
Jose, CA, USA) as described previously [10].
Figure 1. Illustration of the 3D position sensors: detection of the pelvic position by an epicutaneous
sensor placed dorsally over the sacrum (arrowhead) and of the transducer position by a sensor fixed
by a 3D printed adapter (thin arrow); (a) starting position: the coordination system is shown at the
boom left (normal vector of the frontal (F), axial (A) and sagial (S) planes); (b) alignment of trans-
ducer and pelvis using the guidance system in the axial and frontal plane: note the tilted pelvic
position and the different orientation rotation of the sensors in the sagial plane.
A specially developed software program calculates the relative inclination angles be-
tween the two sensors in the frontal, axial and sagial planes in real time, representing
roll, pitch and yaw angles, respectively (see Figure 1). These measurements are transmit-
ted to PC-based output software that displays the angles in real time to assist navigation
and stores the data. The measurement accuracy of the roll and pitch angles was estab-
lished as ±1°, while the yaw angle accuracy was determined to be ±2°, as these accuracies
were deemed clinically acceptable by the authors. A patent application has been submit-
ted for this system [28].
In total, twenty-five consecutive newborns underwent sonographic screening within
the first week of life by a single experienced examiner using the Graf’s method with a GE
Logiq F8 series system with a 7.5 MHz linear transducer (GE Healthcare, Milwaukee, WI,
USA) in 2021. In each child examined, two ultrasound images were obtained for each hip
joint according to the following criteria: One ultrasound image was captured using the
conventional method, following the sonographic criteria outlined by Graf [26] (group A).
Another image was captured using the guidance system, complementing Graf’s so-
nographic criteria by optimizing the transducer’s position based on the calculated tilt an-
gles (Group B) [10]. If a suitable image could not be acquired because of the newborn’s
restlessness, the data collection process was halted.
Figure 1. Illustration of the 3D position sensors: detection of the pelvic position by an epicutaneous
sensor placed dorsally over the sacrum (arrowhead) and of the transducer position by a sensor fixed
by a 3D printed adapter (thin arrow); (a) starting position: the coordination system is shown at
the bottom left (normal vector of the frontal (F), axial (A) and sagittal (S) planes); (b) alignment of
transducer and pelvis using the guidance system in the axial and frontal plane: note the tilted pelvic
position and the different orientation rotation of the sensors in the sagittal plane.
A specially developed software program calculates the relative inclination angles
between the two sensors in the frontal, axial and sagittal planes in real time, representing
roll, pitch and yaw angles, respectively (see Figure 1). These measurements are transmitted
to PC-based output software that displays the angles in real time to assist navigation and
stores the data. The measurement accuracy of the roll and pitch angles was established as
±
1
◦
, while the yaw angle accuracy was determined to be
±
2
◦
, as these accuracies were
deemed clinically acceptable by the authors. A patent application has been submitted for
this system [28].
In total, twenty-five consecutive newborns underwent sonographic screening within
the first week of life by a single experienced examiner using the Graf’s method with a
GE Logiq F8 series system with a 7.5 MHz linear transducer (GE Healthcare, Milwaukee,
WI, USA) in 2021. In each child examined, two ultrasound images were obtained for
each hip joint according to the following criteria: One ultrasound image was captured
using the conventional method, following the sonographic criteria outlined by Graf [
26
]
(group A). Another image was captured using the guidance system, complementing Graf’s
sonographic criteria by optimizing the transducer’s position based on the calculated tilt
angles (Group B) [
10
]. If a suitable image could not be acquired because of the newborn’s
restlessness, the data collection process was halted.
J. Clin. Med. 2024,13, 7656 4 of 9
Statistical Analysis
Data were processed using SPSS Statistics 28 software (SPSS Inc., Chicago, IL, USA).
Normal distribution of parameters was evaluated using Kolmogorov–Smirnov tests and
Q-Q plots. The relative roll and pitch angles between the transducer and pelvic positions
were evaluated using paired t-tests and Levene’s tests. The effects on sonographic
α
-angles
were analyzed using paired t-tests. McNemar’s test was used to analyze the difference in
classification according to Graf. The significance level was defined as p< 0.05.
3. Results
Out of the twenty-five newborns, nineteen had both hips measured following the
study protocol, five had only one hip measured due to increased spontaneous movements
during the examination, and one was excluded because of restlessness. Thus, sonographic
images and relative 3D position data of 43 hips (86 measurements) were obtained according
to the study protocol.
In group A (conventional sonography according to Graf) 39 hips were classified as
Type I and 4 hips as Type II. In group B (guidance system enhanced sonography) 33 hips
were classified as Type I and 10 hips as Type II. The observed difference in classification
was found to be statistically significant (p= 0.031) No other types according to Graf were
detected in our patient sample. Concludingly, the application of our guidance system
resulted in an increased detection rate of Type II hips by reducing relative tilt angles.
4. Analysis of 3D-Data
In group A, where sonographic images were acquired without the guidance system,
the relative tilt angles between the transducer and pelvis ranged from
−
12.6
◦
to 14.3
◦
for
the roll angle (measured in the frontal plane) and from
−
23.8
◦
to 32.5
◦
for the pitch angle
(measured in the axial plane). In group B, which used the guidance system, the relative tilt
angles ranged from
−
3.7
◦
to 3.0
◦
in the frontal plane and
−
3.2
◦
to 4.5
◦
in the axial plane.
(see Table 1). Comparison of variances of relative tilt angles showed highly significant
differences with lower variance in group B (p< 0.001 for frontal and axial planes). In the
axial plane a dorsal tilted transducer position was found more often in group A (mean
pitch angle 4.4
◦
versus 0.3
◦
in group B; p= 0.022). In the frontal plane the tilt angles showed
no significant differences between group A and B (0.2
◦
and 0
◦
;p= 0.854). Figure 2shows
the measured relative roll and pitch angles of both groups.
Table 1. Overview of relative roll (frontal plane) and pitch angles (axial plane): group A (conventional)
and group B (guidance system assisted).
N Minimum Maximum Mean Standard Deviation
roll angle (group A) 43 −12.6◦14.3◦0.2◦7.1
pitch angle (group A) 43 −23.8◦32.5◦4.4◦10.9
roll angle (group B) 43 −3.7◦3.0◦0.0◦1.8
pitch angle (group B) 43 −3.2◦4.5◦0.3◦1.8
Sonographic measurements according to Graf’s system showed slightly reduced alpha
angles in group B (mean alpha angle 62.9
◦
[SD 3.2] in group A and 61.3
◦
[SD 3.5] in group
B; p= 0.04). Correction of cranial and dorsal tilt errors using the guidance system showed
significant effects on alpha angles (p= 0.001 and p= 0.003, respectively). The correction
of caudal or ventral tilt angles showed no significant effects (p= 0.186 and p= 0.191). An
overview of the effects of the tilt angle corrections is shown in Figure 3.
J. Clin. Med. 2024,13, 7656 5 of 9
J. Clin. Med. 2024, 13, x FOR PEER REVIEW 4 of 9
Statistical Analysis
Data were processed using SPSS Statistics 28 software (SPSS Inc., Chicago, IL, USA).
Normal distribution of parameters was evaluated using Kolmogorov–Smirnov tests and
Q-Q plots. The relative roll and pitch angles between the transducer and pelvic positions
were evaluated using paired t-tests and Levene’s tests. The effects on sonographic α-an-
gles were analyzed using paired t-tests. McNemar’s test was used to analyze the difference
in classification according to Graf. The significance level was defined as p < 0.05.
3. Results
Out of the twenty-five newborns, nineteen had both hips measured following the
study protocol, five had only one hip measured due to increased spontaneous movements
during the examination, and one was excluded because of restlessness. Thus, sonographic
images and relative 3D position data of 43 hips (86 measurements) were obtained accord-
ing to the study protocol.
In group A (conventional sonography according to Graf) 39 hips were classified as
Type I and 4 hips as Type II. In group B (guidance system enhanced sonography) 33 hips
were classified as Type I and 10 hips as Type II. The observed difference in classification
was found to be statistically significant (p = 0.031) No other types according to Graf were
detected in our patient sample. Concludingly, the application of our guidance system re-
sulted in an increased detection rate of Type II hips by reducing relative tilt angles.
4. Analysis of 3D-Data
In group A, where sonographic images were acquired without the guidance system,
the relative tilt angles between the transducer and pelvis ranged from −12.6° to 14.3° for
the roll angle (measured in the frontal plane) and from −23.8° to 32.5° for the pitch angle
(measured in the axial plane). In group B, which used the guidance system, the relative
tilt angles ranged from −3.7° to 3.0° in the frontal plane and −3.2° to 4.5° in the axial plane.
(see Table 1). Comparison of variances of relative tilt angles showed highly significant
differences with lower variance in group B (p < 0.001 for frontal and axial planes). In the
axial plane a dorsal tilted transducer position was found more often in group A (mean
pitch angle 4.4° versus 0.3° in group B; p = 0.022). In the frontal plane the tilt angles showed
no significant differences between group A and B (0.2° and 0°; p = 0.854). Figure 2 shows
the measured relative roll and pitch angles of both groups.
Figure 2. Relative roll and pitch angles: (a) conventional group according to Graf’s sonographic cri-
teria [8], (b) guidance system assisted group in which the developed system was used to optimize
relative transducer position in addition to Graf’s criteria [10].
Figure 2. Relative roll and pitch angles: (a) conventional group according to Graf’s sonographic
criteria [
8
], (b) guidance system assisted group in which the developed system was used to optimize
relative transducer position in addition to Graf’s criteria [10].
J. Clin. Med. 2024, 13, x FOR PEER REVIEW 5 of 9
Table 1. Overview of relative roll (frontal plane) and pitch angles (axial plane): group A (conven-
tional) and group B (guidance system assisted).
N Minimum Maximum Mean Standard Deviation
roll angle (group A) 43 −12.6° 14.3° 0.2° 7.1
pitch angle (group A) 43 −23.8° 32.5° 4.4° 10.9
roll angle (group B) 43 −3.7° 3.0° 0.0° 1.8
pitch angle (group B) 43 −3.2° 4.5° 0.3° 1.8
Sonographic measurements according to Graf’s system showed slightly reduced al-
pha angles in group B (mean alpha angle 62.9° [SD 3.2] in group A and 61.3° [SD 3.5] in
group B; p = 0.04). Correction of cranial and dorsal tilt errors using the guidance system
showed significant effects on alpha angles (p = 0.001 and p = 0.003, respectively). The cor-
rection of caudal or ventral tilt angles showed no significant effects (p = 0.186 and p =
0.191). An overview of the effects of the tilt angle corrections is shown in Figure 3.
Figure 3. Illustration of the effects of correction of tilt angles on alpha angles. The average reduction
in the alpha angle is color coded and inserted as a number.
5. Discussion
The critical role of accurately positioning the ultrasound transducer relative to the
pelvis in achieving reliable results during DDH ultrasound screening has been previously
established [27,29]. Despite the standardization of Graf hip screening, a certain suscepti-
bility of the method to relative tilt errors has been discussed [10,25,30]. The presence of
unfavorable relative tilt angles and their significant effects on the obtained sonographic
measurements was shown in an experimental study [27]. The importance of ensuring that
Figure 3. Illustration of the effects of correction of tilt angles on alpha angles. The average reduction
in the alpha angle is color coded and inserted as a number.
J. Clin. Med. 2024,13, 7656 6 of 9
5. Discussion
The critical role of accurately positioning the ultrasound transducer relative to the
pelvis in achieving reliable results during DDH ultrasound screening has been previously
established [
27
,
29
]. Despite the standardization of Graf hip screening, a certain suscepti-
bility of the method to relative tilt errors has been discussed [
10
,
25
,
30
]. The presence of
unfavorable relative tilt angles and their significant effects on the obtained sonographic
measurements was shown in an experimental study [
27
]. The importance of ensuring
that the transducer is positioned in the correct plane was also demonstrated using 3D
ultrasound imaging [25,30].
Since these studies primarily focused on achieving an optimal transducer position
(i.e., measurement plane) without accounting for the pelvic position, the presented system
was developed [
10
]. Given the varying spontaneous pelvic positions observed in clinical
practice, this is an important step in overcoming a major limitation. In our previous study,
we were able to show that the guidance system can significantly reduce the variances in
relative tilt angles which we aimed to further evaluate in a larger sample [10].
Analysis of the 3D data in this study showed a significant reduction in the variance of
the relative tilt angles between the pelvis and the transducer in the frontal and axial planes,
confirming the findings of our previous study [
10
]. However, the aim of the present study
was to provide initial insights into the effects of correcting tilt angles on sonographically
measured alpha angles. The comparison between group A (conventional) and group B
(guidance system assisted) showed that the correction of cranial tilt angles leads to reduced
alpha angles. Interestingly, these cranial tilt angles are frequently combined with dorsal
tilt angles, a combination which was reported to overestimate alpha angles [
27
]. Our
findings support this relationship and underscore the importance of avoiding combined
cranial/dorsal tilt errors. Surprisingly, the effect of caudal tilt errors was not significant.
Here, we would expect that caudal tilt errors tend to underestimate the alpha angles [
27
].
However, this might be due to the experience of the examiner avoiding extensive caudal
tilt errors in most cases (compare Figure 3and Table 1). Beyond all doubt, our system’s ap-
plicability and benefit for inexperienced examiners needs to be evaluated in further studies.
As stated in our previous report, the electronic guidance systems capability to detect
the pelvis position is the key advantage compared to the simple mechanical guidance
device recommended by Graf [10].
In our experience, clinical practice has often shown that tilting of the pelvic orientation
in the lateral position is often not recognized with the cradle-like positioning aid suggested
by Graf.
As a result, despite the use of mechanical aids, undetected tilting of the pelvic orien-
tation often leads to misalignment between the transducer and the pelvis, consequently
leading to significantly altered alpha angle measurements. Although experienced ex-
aminers are likely to detect and correct tilting errors, our guidance system also enables
inexperienced examiners to reduce errors and produce reliable measurements. The elec-
tronic guidance system not only reduces the problem of misalignment, but also stores the
3D data for improved documentation of the correct examination technique. Considering
the significant reduction in alpha angles in group B, this highlights the clinical relevance
of the application of our guidance system, which has the capacity to eliminate errors that
might have clinical implications. Consequential clinical implications may be a prolonged or
shortened treatment with Pavlik harnesses, which is not only relevant to the socioeconomic
aspect, but also improves the newborn’s quality of life by not adding the restriction of
a harness. This may lead to an improved predictability regarding treatment duration.
Moreover, it should be considered that treatment with a Pavlik harness makes everyday
activities such as changing diapers or bathing more difficult for the parents of an affected
child. Our results regarding the classification of subtypes according to Graf show that the
application of our guidance system results in an increased detection rate of Type II hips
by reducing potential tilting errors which consequently suggests that it may influence the
treatment in case of “borderline” hips. This finding further highlights the relevance of
J. Clin. Med. 2024,13, 7656 7 of 9
our novel approach. The increased detection rate of type II hips may result in prolonged
treatment or closer follow-up examinations. However, the actual clinical impact needs to
be determined in further larger studies with long-time follow-up as our system might be
prone to overdiagnosis.
The application of universal ultrasound screening for DDH is still being discussed,
with controversy [
31
]. A review by Kuitunen et al. has shown higher detection rates with
universal ultrasound screening; however, the late detection rates and operative treatment
rates were shown to be similar to those among clinically and selectively screened new-
borns [
31
]. However, the broad regional variety of incidence of DDH, varying screening
programs, etc. may be a limitation of this review [
31
]. Two studies from Austria and
Germany, on the contrary, have shown a significant reduction in surgery rates and costs
after the introduction of universal ultrasound screening [
21
,
22
]. Although universal ul-
trasound screening may still be up for debate, applications like our guidance system can
significantly improve the quality and reproducibility of ultrasound screening, thereby
making it applicable even for inexperienced examiners.
The correct alignment between the transducer and the pelvic position has not yet been
clearly defined in all planes. The alignment in the frontal and axial planes (roll and pitch
angles) is defined as parallel, with a target value of 0
◦
between the transducer and pelvic
sensor in these planes; however, no specific target value is established for the sagittal plane
(yaw angle) [
10
]. Further research is needed to define this value for the sagittal plane in
order to enhance the guidance system for guidance in the sagittal plane.
The study is mainly limited by the cohort size and the restriction to one examiner.
Further studies with a larger sample size as well as multiple examiners will be needed to
validate our electronic guidance system. Moreover, the evaluation of inter-observer and
intra-observer reliability is a crucial aspect that needs to be addressed in future studies. A
potential bias may also occur due to the study protocol in which the hip is first examined
conventionally and secondly using our navigation system, since the examiner has already
seen the joint before.
However, our results show that the application of our presented electronic guidance
system reduces tilting errors, thereby significantly reducing alpha angles, which may
have clinical implications. Furthermore, it has the capacity to enable even inexperienced
examiners to produce correct and more reproducible measurements, which is a major
advantage compared to non-guided examinations. Taking all of these advantages into
account, we believe that an implication of our presented electronic guidance system in
clinical practice has the potential to improve reproducibility and reliability in the ultrasound
screening for DDH. Nevertheless, we clearly state that further larger studies with long-term
follow-up are needed to validate it.
6. Conclusions
Our electronic guidance system significantly reduced the relative tilt angles between
the transducer and the newborn’s pelvis, ensuring optimal positioning of the transducer
relative to the pelvis. The correction of tilt errors showed significant effects on Graf sono-
graphic measurements. Our results suggest that this system has the potential to improve
reproducibility and reliability in the ultrasound screening for DDH. However, larger clini-
cal studies with long-term follow-up are required to validate this novel application and
potential clinical implications resulting from it.
Author Contributions: Conceptualization, A.K.; Validation, C.C. and M.W.; Formal analysis, S.H.;
Investigation, C.C. and A.K.; Resources, R.W.; Data curation, A.K.; Writing—original draft, S.H., R.W.
and A.K.; Writing—review and editing, S.H. and M.W.; Supervision, R.W.; Funding acquisition, A.K.
All authors have read and agreed to the published version of the manuscript.
Funding: This research was supported by “The Medical Scientific Fund of the Mayor of the Federal
Capital Vienna”, grant nr. 15144.
J. Clin. Med. 2024,13, 7656 8 of 9
Institutional Review Board Statement: The study was conducted in accordance with the Declaration
of Helsinki, and approved by Institutional Review Board of the Medical University of Vienna (Ethical
vote: EK-No: 1414/2012, dated 24 April 2015).
Informed Consent Statement: Informed consent was obtained from all legal guardians prior
to participation.
Data Availability Statement: The original contributions presented in this study are included in the
article. Further inquiries can be directed to the corresponding author.
Conflicts of Interest: The authors declare no conflict of interest. On behalf of all authors, the
corresponding author states that there is no conflict of interest. One of the authors (R.W.) has received
institutional funding from Stryker, DePuy Synthes Austria, Johnson & Johnson Medical Limited,
Medacta, Zimmer Biomet Gmbh.
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