Elsevier

Gait & Posture

Volume 57, Supplement 1, September 2017, Pages 9-10
Gait & Posture

O6: Using medical imaging to define the medial-lateral axis of the femur led to significantly different hip rotation kinematics in children with torsional deformities

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Introduction

Kinematics and kinetics during gait are used to inform surgical decision making. For example, hip rotation kinematics are considered the key measurement to decide to perform a femoral derotational osteotomy, and to predict surgical outcomes [1]. However, the accuracy and reliability of hip rotation kinematics has been shown to be the least repeatable [2]. The accuracy of hip rotation kinematics depends on the accurate localisation of the medial-lateral axis of the femur. Conventional methods to localise the medial-lateral axis of the femur is through palpation of bony landmarks (the medial and lateral epicondyles), and define the axis from markers, or a Knee Alignment Device (KAD), over the landmarks. Functional calibration methods have also been derived because the medial-lateral axis of the femur determines the sagittal plane flexion-extension axis of the knee joint. Results on the efficacy of functional and conventional methods in the literature varies [3], [4]. Furthermore, the methods have only been tested in healthy adults. There is no guarantee that results derived from healthy adult populations translate to clinical populations, especially children with torsional deformities, for which accurate hip rotation kinematics are paramount.

Section snippets

Research Question

What is the accuracy of conventional and functional methods to locate the medial-lateral axis of the femur in children with torsional deformities?

Methods

Following ethics approval, 20 children (8 with cerebral palsy, 11 with rotational malalignment and 1 with a genetic disorder) with torsional deformities (confirmed with CT medical imaging) and scheduled for 3D gait analysis were recruited to participate in the study. A registered physiotherapist with >5years experience in gait analysis equipped the children with the standard PiG (VICON, UK) marker set, with additional skin markers on the thighs and shanks. The conventional model used the KAD,

Results

Both conventional and functional methods were significantly different from the EOS benchmark. Approximately 50% of the data were greater than +2SD of normal variability from the EOS benchmark. In contrast, freehand 3D ultrasound was only 1° different in average (NS, p=0.146) and all data were within 2SD of normal variability. As a result, hip rotation kinematics from the medical imaging based methods (EOS, freehand ultrasound) were almost identical whereas hip rotation kinematics from

Discussion

We found significant differences between medical imaging-based and conventional/functional methods to determine the medial-lateral axis of the femur. The use of medical imaging-based methods seems warranted given the importance of hip rotation kinematics for clinical decision making in children with torsional deformities.

References (4)

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  • McGinley

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    (2009)
There are more references available in the full text version of this article.

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