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Baur H.1, Hähni M.1, Hirschmüller A.2,3
1Bern University of Applied Sciences, Health, Physiotherapy, Bern, Switzerland, 2Altius Swiss Sportmed Center, Rheinfelden, Switzerland, 3University Hospital Freiburg, Clinic for Orthopaedic and Trauma Surgery, Freiburg im Breisgau, Germany
Background: Foot orthoses are often prescribed in activity-related overuse injuries despite clear evidence. A primary goal of therapy is pain reduction and symptomatic relief. Depending on the pathology and construction principle, foot orthoses are thought to achieve unloading of specific foot areas. For the forefoot area one strategy is to redistribute pressure from the forefoot to the midfoot by metatarsal pads. Another strategy is to apply local cushioning material under the symptomatic areas in the forefoot. It is still unclear which strategy works best in dynamic situations like running.
Purpose: The purpose was therefore to analyse the effects of two different foot orthoses construction strategies (forefoot cushioning FC; metatarsal pad MP) on plantar pressure in the forefoot area.
Methods: This experimental laboratory study included 23 asymptomatic amateur runners (female: 13, male 10; age: 31.7 ± 9.4 yrs.; height: 1.72 ± 0.09 m; weight: 64.0 ± 8.6 kg; running volume: 166 ± 101 min per week). The runners had to accomplish running intervals (treadmill: 2.78 m·s-1; duration: 2 min) with randomly assigned either one of the two test conditions (FC, MP) or a control foot orthosis (CO) without functional elements implemented. Plantar pressure was measured with an in-shoe device (Pedar-x®-System, Novel®, Munich, D). The means of 10 steps of the maximum peak pressure [kPa] in the forefoot (primary outcome) and the total foot [kPa] were extracted. Furthermore comfort ratings by means of the ICI (insole comfort index, sum score 0-100) were taken as secondary outcome after each running interval. Group differences of the primary outcome peak pressure in the forefoot area were tested by the Friedman-Test (α=0.05). The remaining outcomes were descriptively evaluated (mean ± standard deviation; median; lower & upper 95%-confidence interval; CI).
Results: The peak pressure [kPa] under the forefoot area was in FC (281±80, 95%-CI 246-315) significantly (p=0.003) reduced (11%) compared to CO (313±69, 95%-CI: 283-343). This was also shown in the comparison of FC to MP (MP: 315±80, 95%-CI: 280-350; p=0.001). This means a reduction by 12%. No difference was found between CO and MP (p=0.858). Peak pressure [kPa] under the total foot were CO 364±82, 95%-CI: 328- 399; MP 357±80, 95%-CI: 326- 387; FC 333±81 95%-CI: 298-368. The ICI-score (median) was 50 for CO, 47 for MP and 54 for FC.
Conclusion(s): Local forefoot cushioning is the method of choice to reduce pressure under the respective foot area. In contrast to metatarsal pads, forefoot cushioning can result in significant reductions of plantar pressure. In dynamic situations like running, metatarsal pads should therefore not be implemented in foot orthoses. All tested conditions were rated similar in comfort. Differences in comfort did therefore not influence running execution of subjects. If patients (e.g. metatarsalgia patients) can benefit from forefoot cushioning short- and/or long-term should be evaluated in prospective randomized and controlled intervention studies.
Implications: If mechanical unloading of the forefoot is a goal in the treatment of forefoot pathologies, cushioning of symptomatic areas helps to reduce plantar pressure. Therefore orthopaedic devices can accompany physiotherapy treatment modalities especially during physical activity.
Funding acknowledgements: Foot orthoses were provided by IETEC Orthopädische Einlagen GmbH, Künzell, Germany. No further external funding was received for this project.
Topic: Sport & sports injuries
Ethics approval: The study was evaluated by the Ethics Committee of the Canton Bern (KEK-Nr. Z039/12) and was classified as low risk.
All authors, affiliations and abstracts have been published as submitted.
