Recommendations for the reporting of foot and ankle models

Abstract

Multiple marker sets and models are currently available for assessing foot and ankle kinematics in gait. Despite the presence of such a wide variety of models, the reporting of methodological designs remains inconsistent and lacks clearly defined standards. This review highlights the variability found when reporting biomechanical model parameters, methodological design, and model reliability. Further, the review clearly demonstrates the need for a consensus of what methodological considerations to report in manuscripts, which focus on the topic of foot and ankle biomechanics. We propose five minimum reporting standards, that we believe will ensure the transparency of methods and begin to allow the community to move towards standard modelling practice. The strict adherence to these standards should ultimately improve the interpretation and clinical useability of foot and ankle marker sets and their corresponding models.

Introduction

Over the past decade our understanding of foot and ankle motion during gait has increased significantly due to pioneering bone pin analysis and the expansion of multi-segment foot models used to assess and quantify kinematic parameters in gait (Carson et al., 2001, MacWilliams et al., 2003, Leardini et al., 2007, Nester et al., 2007, Lundgren et al., 2008, Wolf et al., 2008). More sophisticated analytical methods have allowed for a better understanding of foot and ankle function. Where previously the foot has been considered as a single rigid segment in the literature, invasive in vivo measurements of foot kinematics have highlighted its complexity and the importance of the joints distal to the hindfoot (Lundgren et al., 2008, Wolf et al., 2008).

The utility and rationale of multi-segment foot models have previously been explored in review articles, yet conflicting conclusions are presented (Rankine et al., 2008, Deschamps et al., 2011). In their review, Rankine et al. (2008) concluded that there is demonstrated clinical application of multi-segment foot models in the characterisation of gait associated with pathologies such as rheumatoid arthritis, posterior tibial tendon dysfunction and hallux rigidus. However, this does not necessarily demonstrate wider clinical utility, as this conclusion is based on the literature, where multi-segment foot models have not been used extensively to describe other pathologies than those reported. In comparison, Deschamps et al. (2011) discuss the inherent issues relating to reliability, and conclude that further research is required to document the reliability and external validity of published models. This is likely to directly inform clinical utility.

Perhaps the broader issues of clinical utility and practicality could be easily resolved through standardisation of either reporting or more drastically modelling. The concept of standardisation has been approached by a number of international scientific societies in the past (such as the ISB recommendations for joint coordinate systems (Wu et al., 2002, Wu et al., 2005). These attempts have largely been accepted by the international community and are not commonly cited. While the initiative of the ISB was successful, there have been very few further examples of clear standards for reporting of models. In February 2012 the authors contacted the ISB, ESB, GCMAS, ASB and iFAB to investigate, if at the time, there were any standards for reporting models of the foot and ankle. All societies reported that there were no such standards in place.

Despite the review by Deschamps et al. (2011), providing much needed clarity with regards to the appropriate use of multi-segment foot models, their findings have been limited by the exclusion of single segment foot models. This current review differs to those previous published as it critically evaluates the concept of marker set and model development of both single segment and multi-segment foot models. The primary aim of this review was to systematically review the existing literature and identify all articles that report an original model or a major variation of an original model of the foot and ankle. From the findings of the literature review, and critical analysis, we also aim to propose a series of reporting standards, which we hope will help to facilitate consistency and transparency when developing a new model of the foot and ankle.