Iterative Design of Custom Dynamic Orthoses to Reduce Articular Contact Stress

Iterative Design of Custom Dynamic Orthoses to Reduce Articular Contact Stress

The proposed study evaluates the effect of carbon fiber brace design on forces across the ankle joint. Research suggests that ankle arthritis develops after ankle fracture, in part, due to elevated forces on the cartilage. It is expected that carbon fiber braces can be designed to reduce forces in the ankle joint and thereby reduce the risk of developing arthritis following traumatic injury. In this study, brace geometry will be varied to determine how these changes influence the forces experienced by ankle cartilage. The proposed study will provide evidence that can be used by clinicians and researchers to design braces that most effectively reduce forces on ankle cartilage.

The primary purpose of this line of research is to investigate the effects of carbon fiber custom dynamic orthosis (CDO) design on the forces and contact stress at the ankle, with the goal of reducing the development of post traumatic osteoarthritis (PTOA) in the ankle. Research suggests that ankle arthritis develops, in part, due to increased contact stresses within the ankle joint following fracture. It is expected that reducing articular contact stress at the ankle has the potential to delay or prevent the development of PTOA. CDOs have been shown to significantly improve function following extremity injury, and show promise for offloading the injured limb after severe lower extremity injuries. Therefore, the proposed effort is designed to evaluate how different CDO design factors influence offloading and therefore the reduction of forces and articular contact stress at the ankle.

Adult participants will be evaluated while wearing carbon fiber braces of varied geometry. The primary dependent measure is ankle joint contact stress. Following consent and enrollment computerized tomography (CT) images will be used to determine the geometry of the joint articular surfaces. Ankle contact stress will be calculated using discrete element analysis and biomechanical data collected in subsequent data collection.

Participants will be cast and fit for three CDOs with varied geometry. Participants will be blinded to the design variation of each device and will only know them as CDO-A, CDO-B, or CDO-C. Testing will be completed under 4 conditions: No-CDO, CDO-A, CDO-B, CDO-C, with each bracing condition (A/B/C) representing a CDO design variant. Physical performance measures will incorporate tests of agility, speed, and lower limb power to ensure that changes to device design do not negatively affect physical function. Questionnaires will be used to evaluate participants' current and desired activity level, pain with and without CDO use, satisfaction with the devices, perception of comfort and smoothness between devices, and preference between CDOs. Semi-structured interviews will be completed to fully capture the participant's perspective. Lower limb forces and motion will be assessed using a computerized motion capture system and force plates in the floor. Forces between the foot and CDO will be measured using force sensing insoles, and muscle activity data will be collected using surface electromyography. Devices will be mechanically tested, and participant demographic and anthropometric data will be recorded.

TIBIAL PILON FRACTURE PARTICIPANTS:

Inclusion Criteria:

• Ages: 18-65
• Sustained unilateral fracture of the tibial pilon within the preceding 5 years
• The fracture has completely healed
• Ability to walk 50 feet without use of an assistive device (cane, crutch, etc.)
• Ability to walk at a slow to moderate pace
• Shoe size between women's 8 and 13.5 or men's 6.5 and 13
• Ability to read and write in English and provide written informed consent
• Individuals with elevated contact stress according to model generated using PedCAT standing CT images (will be answered after completing visit one)

Exclusion Criteria:

• Pain > 6/10 while walking
• Increase in pain during testing of 3/10 or greater
• Neurologic, musculoskeletal (including bilateral fractures) or other condition limiting function of the contralateral extremity
• Medical or psychological condition that would preclude functional testing (ex. moderate or severe brain injury, stroke, heart disease)
• Wounds to the calf that would prevent CDO fitting
• Fractures secondary to neuropathy or severe osteopenia
• Classification as non-ambulatory
• Previous fractures near the tibial pilon on the involved limb
• Surgery on involved limb anticipated in the next 6 months
• Requirement of a knee stabilizing device (i.e. KAFO, KO…) to perform daily activities
• Visual or hearing impairments that limit walking ability or limit the ability to comply with instructions given during testing
• BMI greater than 40
• Pregnancy- Per participant self-report. Due to the expected small number of pregnant individuals and resulting inability to account for its effect on resulting outcomes, participants will be withdrawn from the study.

HEALTHY ABLE-BODIED PARTICIPANTS:

Patient Inclusion Criteria

• Between the ages of 18 and 65
• Shoe size between women's 8 and 13.5 or men's 6.5 and 13
• Healthy individuals without a current complaint of lower extremity pain, spine pain, or medical or neuromusculoskeletal disorders that have limited participation in work or exercise in the last 6 months
• Full active range of motion of the bilateral lower extremities and spine
• Ability to hop without pain
• Ability to perform a full squat without pain
• Ability to read and write in English and provide written informed consent

Patient Exclusion Criteria

• Diagnosed moderate or severe brain injury
• Prior lower extremity injury resulting in surgery or limiting function for greater than 6 weeks
• Diagnosis of a physical or psychological condition that would preclude testing (e.g. cardiac condition, clotting disorder, pulmonary condition)
• Visual or hearing impairment that would interfere with instructions given during testing
• Require an assistive device
• Wounds to the foot or calf that would prevent CDO use
• BMI greater than 40
• Pregnancy - Per participant self-report. Due to the expected small number of pregnant individuals and resulting inability to account for its effect on resulting outcomes, participants will be withdrawn from the study