Material properties and application of biomechanical principles provide significant motion control performance in experimental ankle foot orthosis-footwear combination. (February 2021)

• Record Type: Journal Article
• Authors: Hovorka, Christopher F.; Kogler, Géza F.; Chang, Young-Hui; Gregor, Robert
• Is Part Of: Clinical biomechanics. Volume 82(2021)
• Publication Date: 2021-02
• Subjects: Ankle foot orthosis -- Footwear -- Ankle foot orthosis-footwear combination -- Motion control -- Three force system -- Stiffness; Biomechanics -- Periodicals; Osteopathic medicine -- Periodicals; Biomechanics -- Periodicals; Osteopathic Medicine -- Periodicals; 612.76
• DOI: 10.1016/j.clinbiomech.2021.105285
• Languages: English
• ISSNs: 0268-0033

Abstract

Abstract: Background: This study, the first of its kind, originated with the need for a brace (an ankle foot orthosis), to constrain ankle plantarflexion and dorsiflexion within a motion threshold of <5°. A conventional thermoplastic, solid brace failed during a quasi-static loading study, informing the investigation and development of an experimental carbon composite brace, maximizing stiffness and proximity of shank and foot cylindrical shells to provide the required degree of control. Methods: Two experiments were conducted: a quasi-static loading study, using cadaveric limbs ( n = 2), and a gait study with healthy subjects ( n = 14). Conditions tested were STOP, FREE, and CONTROL. Data for all studies were collected using six motion-capture cameras (Vicon, Oxford, UK; 120 Hz) tracking bone-anchored markers (cadaveric limbs) and skin-anchored markers (subjects). In the quasi-static loading study, loading conditions were congruent with the gait study. Study 1 involved a quasi-static loading analysis using cadaveric limbs, compared motion data from a conventional thermoplastic solid brace and the experimental brace. Study 2 involved quantifying ankle plantarflexion and dorsiflexion in subjects during treadmill walking, in brace STOP, FREE, and CONTROL conditions. Findings: The experimental brace in STOP condition consistently constrained ankle plantarflexion and dorsiflexion below the motion threshold of <5°, across all studies. Interpretation: Collectively, these findings demonstrate (1) that a conventional thermoplastic, solid brace was ineffective for clinical applications that required significant motion control, and (2) that ankle motion control is most effective when considered as a relationship between the brace, the ankle-foot complex, and the external forces that affect them both. Highlights: This study describes the performance of ankle foot orthoses and footwear used by healthy subjects. A conventional thermoplastic solid ankle foot orthosis failed to restrict ankle motion to less than 5 degrees. An experimental ankle foot orthosis-footwear combination restricted ankle motion to less than 5 degrees. Integral footwear in the experimental ankle foot orthosis minimized interruption in rollover. Research on ankle foot orthoses and footwear requires a shift in focus by scientists and clinicians.