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This may be the author’s version of a work that was submitted/accepted for publication in the following source: Bishop, Chris, Paul, Gunther, & Thewlis, Dominic (2013) The reliability, accuracy and minimal detectable difference of a multi- segment kinematic model of the foot-shoe complex. Gait and Posture, 37(4), pp. 552-557. This file was downloaded from: https://eprints.qut.edu.au/49002/ c Consult author(s) regarding copyright matters This work is covered by copyright. Unless the document is being made available under a Creative Commons Licence, you must assume that re-use is limited to personal use and that permission from the copyright owner must be obtained for all other uses. If the docu- ment is available under a Creative Commons License (or other specified license) then refer to the Licence for details of permitted re-use. It is a condition of access that users recog- nise and abide by the legal requirements associated with these rights. If you believe that this work infringes copyright please provide details by email to [email protected] License: Creative Commons: Attribution-Noncommercial-No Derivative Works 2.5 Notice: Please note that this document may not be the Version of Record (i.e. published version) of the work. Author manuscript versions (as Sub- mitted for peer review or as Accepted for publication after peer review) can be identified by an absence of publisher branding and/or typeset appear- ance. If there is any doubt, please refer to the published source. https://doi.org/10.1016/j.gaitpost.2012.09.020 G Model GAIPOS-3720; No. of Pages 6 Gait & Posture xxx (2012) xxx–xxx Contents lists available at SciVerse ScienceDirect Gait & Posture jo urnal homepage: www.elsevier.com/locate/gaitpost The reliability, accuracy and minimal detectable difference of a multi-segment kinematic model of the foot–shoe complex a, b,1 a,2 Chris Bishop *, Gunther Paul , Dominic Thewlis a School of Health Sciences, University of South Australia, City East Campus, North Terrace, Adelaide, SA 5000, Australia b School of Public Health and Social Work, QUT - Queensland University of Technology, Kelvin Grove, Queensland 4059, Australia A R T I C L E I N F O A B S T R A C T Article history: Kinematic models are commonly used to quantify foot and ankle kinematics, yet no marker sets or Received 2 February 2012 models have been proven reliable or accurate when wearing shoes. Further, the minimal detectable Received in revised form 17 May 2012 difference of a developed model is often not reported. We present a kinematic model that is reliable, Accepted 20 September 2012 accurate and sensitive to describe the kinematics of the foot–shoe complex and lower leg during walking gait. In order to achieve this, a new marker set was established, consisting of 25 markers applied on the Keywords: shoe and skin surface, which informed a four segment kinematic model of the foot–shoe complex and Kinematics lower leg. Three independent experiments were conducted to determine the reliability, accuracy and Footwear minimal detectable difference of the marker set and model. Inter-rater reliability of marker placement Foot and ankle biomechanics Reliability on the shoe was proven to be good to excellent (ICC = 0.75–0.98) indicating that markers could be Accuracy applied reliably between raters. Intra-rater reliability was better for the experienced rater (ICC = 0.68– 0.99) than the inexperienced rater (ICC = 0.38–0.97). The accuracy of marker placement along each axis was <6.7 mm for all markers studied. Minimal detectable difference (MDD90) thresholds were defined for each joint; tibiocalcaneal joint – MDD90 = 2.17–9.368, tarsometatarsal joint – MDD90 = 1.03–9.298 and the metatarsophalangeal joint – MDD90 = 1.75–9.128. These thresholds proposed are specific for the description of shod motion, and can be used in future research designed at comparing between different footwear. ß 2012 Elsevier B.V. All rights reserved. 1. Introduction possible to model a foot–shoe complex (i.e. the foot and shoe together) rather than just a shoe or the foot in isolation. In this Kinematic models are commonly used to quantify foot and example, the foot remains the major factor determining the ankle kinematics during activities of daily living. However, most of kinematics, however the shoe changes the basic assumptions of these models were developed with the intention of studying the segments. barefoot biomechanics [1,2], when typically activities of daily While the concept of a shoe model appears relatively logical, living are performed while wearing shoes. The translation of these there are methodological issues that must be dealt with. Firstly, one models to the study of shod kinematics is problematic. It has been must define the segments of the model based on standard palpable previously identified that tracking the motion of shoe-mounted anatomical landmarks. Palpation through the surface of a shoe markers does not indicate the movement of the foot inside the shoe comes with a degree of complexity and a number of unknown [3,4]. Although methods have been developed to apply markers on factors. Palpation guidelines, such as those documented by Van Sint the skin surface through the shoe, the analysis of in-shoe foot Jan [6], that are commonly followed in surface marker sets were not kinematics is not always required [5]. In this case, it is essential to developed for use through clothing or shoes. By following these consider the segments of the shoe, which are conceptually similar methods, it is likely the application of markers on the shoe surface to the anatomy of the foot, rather than the foot itself. When the will come with a degree of inaccuracy in regards to the location of the structure of the shoe is added to the complexity of the foot, it is underlying anatomical landmark. This will have a direct impact on the accuracy of anatomical frame definition. We have previously described a method for palpating anatomical landmarks through the shoe upper [7]. Using these guidelines we have proposed a set of * Corresponding author. Tel.: +61 8 83022425. offset values, which account for the difference between the shoe E-mail addresses: [email protected] (C. Bishop), upper and anatomical landmark [7]. The second problem encoun- [email protected] (G. Paul), [email protected] (D. Thewlis). 1 tered is that of technical componentry and material thickness Tel.: +61 7 31385795. 2 Tel.: +61 8 83021540. common to shoes such as rigid heel counters. 0966-6362/$ – see front matter ß 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.gaitpost.2012.09.020 Please cite this article in press as: Bishop C, et al. The reliability, accuracy and minimal detectable difference of a multi-segment kinematic model of the foot–shoe complex. Gait Posture (2012), http://dx.doi.org/10.1016/j.gaitpost.2012.09.020 G Model GAIPOS-3720; No. of Pages 6 2 C. Bishop et al. / Gait & Posture xxx (2012) xxx–xxx coordinate systems (LCS) were used to define each segment. Each joint was Both single-segment and multi-segment marker based models modelled with three degrees of rotational freedom. The joint pose was then of the foot have been published, with demonstrated good intra- estimated using the global optimisation technique described by Lu and O’Connor and inter-rater reliability of marker placement and model output [18]. Rotation of the tibiocalcaneal joint around the x-axis (medial–lateral) was [1,2,8–13]. A recent review highlighted that the current trend is to flexion/extension, about the y-axis (anterior–posterior) was abduction/adduction consider the foot as a number of segments [14]. This trend can be and about the z-axis (superior–inferior) was inversion/eversion. To ensure the z- axis was aligned with the long axis of the segment, the axes of rotations changed extrapolated to the study of footwear kinematics as shoes are when describing the distal foot joints. Rotation around the x-axis (medial–lateral) typically thought to consist of a heel counter, mid-sole and toe box. remained flexion/extension, but the y-axis (superior–inferior) changed to represent Despite demonstrated reliability, the absence of marker placement abduction/adduction and the z-axis (anterior–posterior) changed to represent accuracy assessment makes it difficult to interpret the accuracy of inversion/eversion. An XYZ cardan sequence was used to represent the order of rotations for each joint [19]. anatomical frame definition relative to the underlying bone embedded frame [15]. In addition to reporting static or dynamic 2.1.3. Anatomical landmarks measures of marker placement reliability and accuracy, it is A marker set consisting of 14, 10 mm retro-reflective markers and one hallux important to determine the minimal detectable difference and trihedron (three, 10 mm markers) was applied to the shoe surface and four, 10 mm understand the limitations of a given kinematic model. Therefore, markers and one plate-mounted marker cluster (four, 15 mm markers) were the aim of the study was to demonstrate the reliability and static applied to the skin surface of the leg to define anatomical frames (Fig. 1). To apply markers on the skin surface, previously developed guidelines were used [6]. To and dynamic accuracy of a marker set we have previously palpate anatomical landmarks through the shoe upper, custom guidelines were proposed [7] (albeit to describe the offsets between the shoe developed (Additional File 1). A technical cluster consisting of at least three non- upper and anatomical landmark), which could be used in future collinear markers was placed on each segment.