Kompendium 2020 Forschung & Klinik

TOP-Studien
67
Table 1: Relative roll and pitch angles (between
infant pelvis and transducer in the frontal and
axial planes) for measurements without navigation
(conventional) and for measurements with
navigation system (nav); boldface = significant.
Table 1 min max mean std.-deviation
pitch-angle (conventionel) -23,8° 14,2° 0,6° 9,26
roll-angle (conventionel) -12,5° 14,3° -0,9° 7,68
pitch-angle (nav) -2,8° 4,5° 0,4° 2,23
roll-angle (nav) -3,0° 3,5° 0,3° 2,15
the navigation system significantly reduces the variance of the roll and pitch
angles, i.e. the relative tilt between the infant’s pelvis and the transducer, but
also that the mean value remains unchanged by the alignment with navigation
with regard to these two tilt angles. This means that a more accurate alignment
of the transducer with respect to the pelvis is achieved by the navigation
system, while the target alignment to the original method according to Graf
remains unchanged.
Compared to established aids such as positioning aids for the baby (cradles)
and mechanical transducer guiding devices, the main advantage of the
presented system is the accurate detection of the pelvic position. An additional
strength is not only the accuracy achieved, but also the documentation
of the 3D data, which increases the safety of the method for patients and
examiners.
A limitation of this work is the small size of the collective. Therefore, although
a highly significant improvement in transducer alignment in the frontal and
axial planes could be shown, no significant effect on sonographic alpha
angle could be presented. However, there seems to be a tendency for the
alpha-angles to be reduced under a transducer alignment corresponding to
the navigation data.
Conclusion
This work shows that the alignment between pelvis and transducer can be
significantly improved by the presented navigation system. This represents
a promising approach to increase the quality of the screening program.
Further studies in a large collective are necessary to analyze the effects on
the sonographically measured hip parameters.
Priv.-Doz. Dr. Alexander Kolb
Author:
Alexander Kolb, senior physician,
head of the outpatient clinic
for femoropatellar pathologies
at the Department of Orthopaedics
and Trauma Surgery,
Medical University of Vienna.
Endocert surgeon; 2014 GOTS
fellow. Specialties: Pediatric
orthopedics, endoprosthetics,
sports orthopedics.
References:
1
Graf, R. Fundamentals of sonographic diagnosis of infant hip dysplasia. J. Pediatr. Orthop. 4,
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2
Ea, S. et al. Inter-observer agreement of ultrasonographic measurement of alpha and beta angles
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3
Roposch, A., Graf, R. & Wright, J. G. Determining the reliability of the Graf classification for hip
dysplasia. Clin. Orthop. Relat. Res. 447, 119–24 (2006).
4
Kolb, A. et al. Measurement considerations on examiner-dependent factors in the ultrasound
assessment of developmental dysplasia of the hip. Int. Orthop. 41, 1245–1250 (2017).
5
Kolb, A. et al. Development of an electronic navigation system for elimination of examiner-dependent
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1–5 (2020).
6
Kolb, A. Electronic Transducer Guiding Device for the Sonographic Screening for Developmental
Dysplasia of the Hip. MUW Technol. Offer. 782.18 (2019). doi:10.1007/s00264-017-3455-9