SCANLOAD: The Effect of Limb Loading on Lower Limb Geometry

Orthotists currently use a range of weight bearing conditions when casting or scanning a patient's limb during the Ankle foot orthosis (AFO) fitting process. This variability in clinical practice is the result of differing opinions regarding the best method for fitting, and a limited understanding of how weight bearing affects the resulting geometry. Few studies have been performed to determine the effect of weight bearing on resulting geometry, or the consistency of the geometry obtained. In this study we seek to evaluate the effect of foot loading on lower limb geometry and the consistency of measurements using low-cost 3D scanning technology, with implications for fitting AFOs.

Two groups of subjects will be recruited for this study. The first group (Group 1) will consist of healthy, able-bodied individuals with no history of lower extremity trauma. The second group (Group 2) will consist of individuals with unilateral, below-knee functional deficits that require an AFO for daily activities (e.g. fracture, muscle and/or nerve injury, ankle arthritis, or peripheral neurologic disease).

We will obtain a brief medical history to identify major medical conditions or prior injuries that could influence limb geometry and lead to reliance on an AFO for Group 2 participants.

A 3D representation of each participant's lower limb geometry will be obtained using a Structure Core scanner (Occipital, Inc.), which uses an infrared structured light projector to construct a 3D image of an object. The scanner is connected to an iPad; to operate the scanner, the user rotates the iPad camera around the desired object. In seconds, the entire geometry is digitally reconstructed. Measurements will be evaluated using digital imaging analysis software (Standard Cyborg, Inc.). The different conditions being tested are full weight bearing, partial weight bearing, and non-weight bearing. The effect of limb loading on multiple measures of limb geometry will be evaluated. Limb measurements will include 1) width of the metatarsal heads, 2) width of the calcaneus, 3) foot length, 4) foot height, 5) arch height, 6) medial-lateral width between ankle malleoli, 7) minimum circumference above the ankle malleoli, 8) maximum calf circumference , 9) medial-lateral width of the knee condyles 10) anterior-posterior width at mid patellar tendon, 11) distance from bottom of foot to tibial tubercle.

Eligibility Criteria:
GROUP 1

Patient Inclusion criteria

* Ages: 18-75
* Healthy individuals without a current complaint of lower extremity pain, spine pain, active infections or medical or neuromusculoskeletal disorders that have limited participation in work or exercise in the last 6 months
* Ability to perform a full squat without pain
* Able to read and write in English and provide written informed consent

Patient Exclusion criteria

* Diagnosed moderate or severe brain injury
* Diagnosis of a physical or psychological condition that would preclude testing (e.g. cardiac condition, clotting disorder, pulmonary condition)
* Current complaint of pain or numbness in the spine
* Uncorrected visual or hearing impairments that limit the ability to understand or comply with instructions given during testing
* Require an assistive device
* Open/unhealed wounds on lower extremity.
* Body mass index (BMI) above 35

GROUP 2

Patient Inclusion criteria

* Ages: 18-75
* Daily AFO use to address unilateral below knee functional deficits (e.g. fracture, muscle and/or nerve injury, ankle arthritis, or peripheral neurologic disease)
* Ability to stand independently without use of an assistive device (Cane, crutch, etc)
* Ability to safely bear full body weight on affected limb without use of an AFO or other protection
* Able to read and write in English and provide written informed consent

Patient Exclusion criteria

* Use of an AFO that crosses the knee (includes Knee brace or similar)
* Open/unhealed wounds on lower extremity
* Uncorrected visual or hearing impairments that limit the ability to understand or comply with instructions given during testing
* Body mass index (BMI) above 35
* Diagnoses of a moderate to severe brain injury