Effects of foot orthoses: How important is the practitioner?
Introduction
Foot orthoses (FO) are generally used by clinical practitioners to treat a number of musculoskeletal pathologies. Previous researchers have attempted to study different orthotic devices to understand their effects on gait kinematics and kinetics. Understanding these differences would improve the chances of achieving the desired treatment or outcome. Nevertheless, the exact mechanisms by which FO work are yet to be fully understood. In fact, a number of studies have reported contradicting or unsystematic results [1], [2], [3], [4], [5]. Yet, certain main themes can be extracted from these studies. Recent literature surveys [6], [7] concluded that FO generally have an attenuating effect on the peak impact vertical force and loading rate. Commonly reported kinematic effects normally relate to ankle joint sagittal plane movements, rearfoot frontal plane and tibial transverse plane movements [8]. Specifically, many studies reported that FO increased plantarflexion of the foot, decreased rearfoot eversion and internal tibial rotation [5], [9], [10], [11], [12], [13], [14], [15], [16], [17]. However, kinetic or kinematic effects do not appear to be consistent through all studies [1], [2], [13], [14], [18], [19]. Hence, controversies still persist with regards to whether or not FO induce generic effects on subjects.
Furthermore, the lack of standardisation of the terminology surrounding FO only adds to the ambiguity of their effects [8]. Throughout the literature, the term “foot orthoses” is used as an umbrella term to describe a broad range of devices including custom-made foot orthoses (CFO), prefabricated foot orthoses, heel-lifts, lateral/medial wedges and even flat insoles. Whilst the inherent differences in design and purpose of each device may appear simple, all are defined as foot orthoses despite their different effects. It is therefore crucial that more precise descriptions are provided in order to allow clear and easy classification of devices. Therefore, the terminology used in the current paper will specify which type of foot orthoses is discussed in an attempt to avoid any confusion.
Heiderscheit et al. [20] suggested plausible explanations for the contradicting conclusions on the effects of orthoses. Variation in orthoses fitting methods was amongst the suggested explanations. Although it has been reported that CFO can yield good results for the treatment of lower-limb disorders and injuries [1], [15], [21], construction methods and casting techniques are seldom described in great detail. Based on previous studies [1], [2], [22], it is possible to assume that the prescription and casting method could differ between studies depending on the practitioner involved. This could, in part, explain the conflicting results. Consequently, the exact method used to produce these orthoses remains unclear and almost impossible to replicate.
However, other external factors may also influence the results. As each study focussing on custom-made foot orthoses (CFO) will use a specific practitioner to assess, prescribe and cast each subject included within a study, it is difficult to rule out the importance of the practitioner on the final outcome measure. For example, whilst Stacoff et al. [15] observed significantly different effects between three types of orthoses, three different podiatrists were involved in the process, each one in charge of making one type of orthoses. It cannot be dismissed that the observed changes could be attributed to the change in practitioner or techniques used instead of the orthoses themselves as reported.
As the process of fabricating a CFO involves many variables, the influence of each variable is currently unknown. Due to the nature of the CFO, specifically designed for each subject, assessing their effects and effectiveness is a complex task that has not been completed. Consequently, the aim of the present study was to assess the influence of one of those variables, the inter-practitioner variability of CFO and their different kinematic and kinetic effects during normal gait.
Section snippets
Methodology
A total of 11 practitioners (six podiatrists and five orthotists) with years of clinical experience ranging from 2 to 20 years (mean 11.5 years, ±7.0) took part in the study. A broad spectrum of experience and two different professions were included in the study with a view to better represent the current services and choices available to patients suffering from musculoskeletal pathologies. The practitioners taking part in the study were considered as subjects in order to assess the
Kinematic variables
Table 1, Table 2 present a summary of the kinematic results for the knee, hindfoot-to-tibia and forefoot-to-hindfoot. For the calculated kinematic variables, there were a number of significant systematic changes recorded. On the left lower limb, peak knee flexion, peak knee internal rotation and sagittal knee angle at heel strikes were reduced by a mean of 3.28° (±1.25°), 5.88° (±3.67°) and 1.87° (±0.60°) respectively. For the left foot, a decrease in peak forefoot plantarflexion, forefoot peak
Variability and consistency
The current results suggest that high variability exists between the effects generated by the 11 different CFO used in the study. Only a third (22/64) of the calculated variables caused systematic changes. For most variables, effects appeared to be sporadic, with many CFO producing opposite effects when compared to other CFO. The standard protocol to study FO, as reported in the literature, is to use multiple subjects with a single pair of orthoses. The observed results from each condition are
Conclusion
In summary, it was found that most CFO will induce some systematic changes during gait. Furthermore, this study demonstrated that inter-practitioner variability is a major factor in orthotic intervention in treating a single patient and for a specific pathology. Based on the findings, it is strongly recommended to use caution when drawing general conclusions from research studies using CFO as it has been showed that the practitioner himself or herself will have a great influence on the
Acknowledgments
The authors would like to thank Salts TechStep for their support throughout this study and Andrew Greenhalgh for his help with the Matlab script.
Conflict of interest statement
There is no conflict of interests of any authors with the presented work in this manuscript.
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