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The effect of carbon fiber custom dynamic orthosis use and design on limb loading and motion
Dissertation   Open access

The effect of carbon fiber custom dynamic orthosis use and design on limb loading and motion

Kirsten M Anderson
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Autumn 2025
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Abstract

One of the leading causes of hospitalization among young adults is lower limb injury1 which puts patients at risk of developing post-traumatic osteoarthritis (PTOA).2-5 The negative effects of limb trauma and resulting ankle PTOA include persistent physical and psychosocial disability.1-12 Ankle foot orthoses (AFOs) are used following lower limb trauma to stabilize the foot and ankle. Carbon fiber custom dynamic orthoses (CDOs) are a subset of AFOs that support and protect the limb, control ankle motion, and offload the injured foot and ankle following lower limb trauma. CDOs have been shown to significantly improve physical function, limb mechanics and loading, and patient reported outcomes following lower limb trauma.5, 13-24CDOs consist of a proximal cuff that wraps around the leg just below the knee, a carbon fiber posterior strut that runs the length of the leg and stores and returns energy, a full-length carbon fiber footplate that acts as a lever arm to deflect the posterior strut, and in some cases a foam heel wedge in the shoe. CDO design characteristics including posterior strut stiffness15, 21, 25-27 and bending point20, 28, heel height and durometer5, and alignment14, 22, 29, 30 have previously been studied to determine the effect they have on limb mechanics, foot loading, and patient reported outcomes. The majority of prior literature focuses on the Intrepid Dynamic Exoskeletal Orthosis (IDEO) which has successfully restored function for military service members following lower limb trauma.5, 14-18, 20-24, 26-28, 31, 32 The reported success with the IDEO has resulted in increased adoption of CDOs in civilian practice,27, 32-39 and clinicians can select each CDO component to best meet the needs of their patient.17, 35, 36 There are certain limitations to previous work that clinicians must consider when applying these results in civilian practice; certain components of the CDO, including the proximal cuff and footplate, have not been systematically investigated, the CDO design characteristics that have been investigated in the IDEO do not necessarily overlap with those included in CDOs more commonly used in civilian practice, and the IDEO is commonly provided in tandem with a targeted training program. The included studies investigate the effects of posterior strut stiffness and proximal cuff design, representative of those used in clinical practice and prior research, on limb mechanics, foot loading, and patient perception of the CDO. Individuals who had experienced lower limb injuries tested a nearly 60% range of posterior strut stiffnesses, lower than those tested in previous CDO related research. While CDO use altered limb mechanics and foot loading compered to walking without an orthosis, there were limited differences between stiffness conditions. Unimpaired individuals and individuals who had experienced lower limb injuries resulting in ankle PTOA completed testing with four proximal cuff designs with differing geometry and closure mechanisms. The included proximal cuff designs are representative of those used in clinical practice and prior research, but there were limited differences in limb mechanics, foot loading within the CDO, and patient reported outcomes between cuff designs. Study results indicate that a range of posterior strut stiffnesses and proximal cuff designs can be used to alter limb mechanics and foot loading within the CDO during gait. This allows clinicians to consider other factors during the CDO provision process, such as patient preferences or donning and doffing capability. Additional work is needed to determine if a larger range of posterior strut stiffnesses, stiffness of the full-length footplate, or targeted training programs impact limb mechanics, foot loading, and patient perception of the CDO.
 AFO Ankle Foot Orthosis Carbon Fiber Post-Traumatic Osteoarthritis

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