Understanding the effect of lower limb torsional deformities in typically developing children and adolescents
Dr Morgan Sangeux
Lower limb torsional deformities (torsion in the femur and the tibia) are common in children and adults with Cerebral Palsy (CP). Cerebral palsy is a group of permanent movement disorders that are attributed to non progressive disturbances of the developing brain. The prevalence rate of CP in Australia is around 2 or 3 in 1,000 live births. This rate increases to 40 –100 per 1,000 live births among babies born very early or with very low birth weight. In Australia, it is estimated that a child with CP is born every 15 hours, and over 34,000 Australians currently have the disorder.
Lower limb torsional deformities increase during growth in children with cerebral palsy due to their neurological conditions. The torsional deformities lead to single or multi-level lever-arm disease and may prevent the children from being able to walk. As a result, most children with cerebral palsy presenting with torsional deformities are treated with surgical correction. These children often undergo pre-operative gait analysis to support decision and planning because of the complexity of the surgical corrections.
Gait analysis is a non-invasive force and motion measurement technique which provides quantitative information on limb motion, net joint torques and muscle electromyography. However, some key information to support surgical decision cannot be obtained from gait analysis alone. The net torque exerted about a joint can be produced by an infinite combination of muscle forces because the number of muscles spanning each joint is greater than the degrees of freedom of joint movement. Musculoskeletal modelling provides information such as the time histories of muscle forces leading to the possibility to calculate joint contact forces during gait.
Musculoskeletal models need to be patient specific to be accurate. Until recently, most studies have used Magnetic Resonance Imaging (MRI). However, the cost associated with the acquisition and processing of MRI images generally prohibits use in the clinical setting. Our team has developed alternative medical imaging protocols to inform patient-specific models, for example from Computed Tomography (CT), 3D free-hand ultrasound and low dose bi-planar X-rays (EOS-imaging).
Our aim is to allow musculoskeletal modelling computations to be run in the clinical setting and the additional information on muscle and joint contact forces to contribute to clinical decision making. The expected outcomes are (i) a better understanding of the functional effect of lower limbs torsional deformities in children with cerebral palsy, (ii) a better understanding of the benefits of surgical correction in children with cerebral palsy, and (iii) a tool to calculate the muscle and joint contact forces during gait available for a wide range of clinical settings leading to more informed surgical decision making.
- NH&MRC CP-CRE, Chief Investigators: Professor Dinah Reddihough, Professor H.Kerr Graham, Professor Christine Imms, Professor Nadia Badawi, Associate Professor Michael Coory, Professor Eve Blair, Professor Rob Carter.
- Canadian Institutes of Health Research: Professor Unni Narayanan, Dr Darcy Fehlings, Professor H. Kerr Graham, Dr R Hamdy, Dr Kishore Mulpuri.
- The Murdoch Children’s Research Institute
- The University of Melbourne
- Passmore E, Lai A, Sangeux M, Schache AG, Pandy M. Application of ultrasound imaging to subject-specific modelling of the human musculoskeletal system. Meccanica. 2016;1:12
- Passmore E, Sangeux M. Defining the medial-lateral axis of an anatomical femur coordinate system using freehand 3D ultrasound imaging. Gait Posture. 2016;45:211-6.
- Passmore, E., M.G. Pandy, H.K. Graham and M. Sangeux, Measuring Femoral Torsion In Vivo Using Freehand 3-D Ultrasound Imaging. Ultrasound in medicine & biology. 2016;42(2):619-23.
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