Effects of foot orthoses on skeletal motion during running
Introduction
Excessive eversion and excessive tibial rotation have been associated with various running injuries [1], [2] Excessive eversion has been linked to Achilles tendon problems [3], [4] and to shin splints [5], [6] whereas excessive tibial rotation has been associated with the development of knee injuries [2], [7].
To reduce and control excessive movements, foot orthoses or shoe inserts are often applied medially inside the shoes. Studies analyzing the effect of such orthoses administered to injured runners generally report 70–80% positive outcomes [1], [7], [8]. This is a rather surprising result since the orthoses tested in these studies differed considerably in shape, material properties (ranging from flexible to rigid) and placements. The lack of a consensus on the appropriate application of shape, material properties and placement of foot orthoses indicates that the knowledge on which these decisions were based is small and incomplete.
Effects produced by orthoses may be the result of mechanical and/or proprioceptive mechanisms. Orthoses are thought to reduce foot eversion and/or increase the afferent feedback from cutaneous receptors in the foot [9], which is assumed to change the innervation pattern and, consequently, the movement. However, the quantification of these cause and effect processes is not trivial and the determination of the actual skeletal foot movement is difficult, since skeletal kinematics are masked by soft tissue movements [10], [11].
Several groups have studied the effect of foot orthoses on rearfoot movement using various orthotic designs, materials, and placements as well as varus wedged shoes, but the results were inconsistent. One group of authors found significant differences in rearfoot movements as a result of these interventions [12], [13], [14], [15], [16] whilst another did not [17], [18], [19], [20], [21]. Nigg et al. [20] reported a reduction of initial pronation (eversion) as a result of medial orthoses but not of total pronation, and found that a posterior support inside the shoe (support beneath the sustentaculum tali) was more effective in reducing initial eversion than more anterior placements. However, the reasons for these results are not well understood.
Foot movement is transferred to the tibia by a coupling mechanism [22], [23], [24], [25]. Consequently, it has been proposed that excessive eversion may be transferred into excessive tibial rotation [4], [5], [7]. Thus, it may be concluded that orthoses may have an effect on this movement coupling and may consequently affect tibial rotation. However, effects of orthoses on the transfer of the foot movement to the tibia during running have not yet been studied, and hence, orthotic effects on the kinematics of the lower extremities are currently not well understood.
Studies related to the kinematics of running and orthotic effects are based on skin or shoe mounted marker settings. Recent studies comparing skin/shoe markers with bone pin markers indicate that externally mounted markers overestimate the movements of the underlying bone [10], [11]. Therefore, external markers cannot be used to obtain precise skeletal kinematics information. Hence, the purpose of this study was to quantify the effect of medially placed orthoses on calcaneal eversion and tibial rotation using markers mounted on bone pins.
The hypotheses to be tested in this study were:
I. Posterior orthoses are more effective in decreasing maximum eversion and internal tibial rotations compared with anterior orthoses.
II. Medially placed orthoses (anterior and posterior) decrease maximum eversion and internal tibial rotation compared with no orthoses.
Section snippets
General project description
The experiments were performed at the Department of Orthopaedic, Karolinska Institute at Huddinge University Hospital, Stockholm. The project was part of a larger study performed at the University of Calgary, Canada [11], [26], [27]. Ethical approval for the experiments was obtained from the Ethics committee of the Karolinska Hospital and by the Medical Ethics Committee of The University of Calgary.
Briefly, five healthy male volunteers participated in this study (mean 28.6 (SD 4.3 years), mean
Results
Eversion and tibial rotation movement patterns are presented in Fig. 3 (single curves of a typical subject) and Fig. 4 (mean curves of each condition for each subject). Eversion and internal tibial rotation took place from touchdown until midstance, thereafter, the movements reversed to inversion and external tibial rotation until take-off. These general movement patterns were found to be consistent for all subjects and test conditions.
At touchdown the calcaneus was inverted and the tibia was
Discussion
Due to the invasive character of the study the number of subjects was limited to five, which did not allow an extensive statistical analysis. However, the general rotation patterns during running were very consistent and generally found to be similar to previous investigations using external markers in running [29], [30], [31], bone markers in running as well as bone markers in walking [32], [33]. Differences between those investigations and this study are discussed below, including the results
Conclusion
In conclusion, this in vivo study showed that medially placed foot orthoses did not substantially change tibiocalcaneal movement patterns during running of normal subjects. Orthotic effects on eversion and tibial rotations were found to be small and unsystematic over all subjects. Differences between the subjects were significantly larger (up to 10°; p < 0.01) than between the orthotic conditions (1–4°). Significant orthotic effects across the subjects were found only for total internal tibial
Acknowledgements
This study was supported by the Swedish Defense Material Administration, the Swiss Federal Sports Commission (ESK), the Olympic Oval Endowment Fund of Calgary and ADIDAS America. The help of R. Lawson, H. Strebel and E. Avramakis at various stages of the project was greatly appreciated. The authors would like to thank S. Drevemo and C. Johnston of the Swedish University of Agricultural Science in Uppsala for providing movement analysis equipment.
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