Background: No studies have determined the optimal location and angular orientation for orthotic dorsal control mechanisms (e.g. dorsal foot strap) for use in lower limb orthoses to resist foot motion for maximum user function and comfort.
Objectives: To determine the optimal dorsal location and angular orientation of an orthotic control mechanism to resist foot movements associated with heel rise.
Study design: An in vitro cadaveric study quantified the dorsal force required to resist foot motion.
Methods: The study simulated heel rise and quantified the force of a dorsal control mechanism in nine test conditions comprising three angles (75°, 90°, and 105°) and three longitudinal axis positions at 2.0 cm increments.
Results: The test condition representing the longest lever arm (proximal location) applied at an obtuse angle (105°) required the least force (55.6 N) to constrain foot motion, whereas the shortest lever arm (distal location) at the acute angle (75°) required the greatest force (90.4 N) to constrain foot motion.
Conclusion: To resist foot motion relative to the orthosis, clinicians should aim for the most proximal placement (longest lever arm) at an obtuse angle (105°) with the intention that the resultant controlling force be perpendicular to the bony structure.
Clinical relevance: A dorsal foot control strap applies a critical orthotic corrective force, as part of a force couple to restrict motion of the foot and shank in lower limb orthoses. Foundational orthotic principles that stipulate optimal clinical placement and angular orientation are necessary to ensure maximum function and comfort to users.
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