Author: Arjun Sivakumar
Sivakumar, Arjun, 2018 Involvement of the Medial Column Ligaments in Biomechanically Simulated Adult Acquired Flatfoot Deformity, Flinders University, College of Science and Engineering
Terms of Use: This electronic version is (or will be) made publicly available by Flinders University in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. You may use this material for uses permitted under the Copyright Act 1968. If you are the owner of any included third party copyright material and/or you believe that any material has been made available without permission of the copyright owner please contact copyright@flinders.edu.au with the details.
Background: Adult acquired flatfoot deformity (AAFD) is one of the most common
etiologies, estimated to affect approximately 8% of adults (aged 21 and over) in the U.S. (NPD
Group for the Institute for Preventive Foot Health, National Foot Health Assessment 2012).
This corresponds to approximately 19 million people (U.S. Census Bureau, 2017).
Classification systems describing the symptoms of AAFD are widely used in the clinical
assessment and treatment of the condition (‘Stage I – IV Flatfoot’) and recognize the spring
ligament as the most contributing stabilizing structure of the medial ankle during all stages of
the condition, with the deltoid ligament described to only experience substantial deterioration
at the end stage of the condition (Stage IV flatfoot). In spite of this, the biomechanical
involvement of these ligaments as the physical deformity progresses has not been established.
Objectives: The aim of this study was to better understand the biomechanical contribution of
the primary static stabilizing ligaments of the medial column (spring ligament, deltoid
ligament, talocalcaneal interosseous, cuneonavicular ligaments) during the physical
progression of AAFD.
Methods: 9 unmatched Fresh-frozen cadaveric feet specimens were used. The age of the
specimens ranged from 44 to 84 years and the cause of death was not related to the foot.
Except for the posterior tibial tendon (dynamic stabilizer), all other structures were kept intact.
Small tantalum beads were carefully implanted at the attachment sites of the deltoid,
talocalcaneal, navicular cuneiform and spring ligaments (superomedial calcaneonavicular and
inferior calcaneonavicular).
A characteristic physical deformity anatomically similar to AAFD was progressively produced
in the cadaveric feet using a novel six degree of freedom (6DOF) Hexapod Robot. This was
produced under load control through applying 10 degrees of dorsiflexion, followed by a series
of 5 incremental loads (100N, 230N, 460N, 690N, 920N) with the foot fully unconstrained.
Left and right stereo-radiographs were taken of the foot in its unloaded state, as well as at each
of the loadsteps. Radiostereometric Analysis (RSA) was then used to, digitize and track the
displacement of the tantalum markers in 3D space and calculate the strain within each of the
ligaments at each progressive loadstep.
Results: The strains for each of the 11 ligaments at 5 progressive loads were calculated, from
which the sequence of recruitment of the ligaments could be observed at each stage through
the interacting elongations and subsequent contractions of the stabilizing ligaments at
progressive loads. The tibiocalcaneal portion of the deltoid ligament exhibited the highest
strain at each loading condition.
Conclusion: Under the tested conditions, the biomechanical contribution of the static
stabilizing of the medial column as the physical deformity progresses was evaluated. The
deltoid ligament was found to experience higher strains than the other ligaments at each stage
of the condition. An understanding of the contribution of the ligaments during the onset of
AAFD is essential for optimizing the management of symptomatic AAFD. From this study, it
is suggested that more attention be given to the deltoid ligament at all stages of AAFD.
Keywords: Adult Acquired Flatfoot Deformity, Medial Column Ligaments, Biomechanics, Contribution, Strain, Radiostereometric Analysis
Subject: Engineering thesis
Thesis type: Masters
Completed: 2018
School: College of Science and Engineering
Supervisor: Associate Professor John Costi