Date of Award

5-2024

Document Type

Scholarly Project

Degree Name

Doctor of Physical Therapy (DPT)

Department

Physical Therapy

First Advisor

Gary Schindler

Keywords

Navicular motion, gait, navicular drop, Vicon system

Abstract

Purpose/Hypothesis: Understanding navicular motion during gait is crucial for research and clinical applications. This study aimed to assess a method of measuring navicular drop during dynamic walking trials. Our technique used a two-stage assessment of navicular drop; these stages consisted of an initial static examination of the navicular position in subtalar neutral, combined with a dynamic evaluation of navicular drop during walking gait. These stages were conducted twice, with a week between data collections. This study aimed to determine the reliability of this two-stage method. We hypothesize that a two-stage process, using two independent Vicon systems, will be able to provide reliable assessments of both static navicular position in subtalar neutral and dynamic navicular motion during walking trials. Number of Subjects: 40

Materials/Methods: Each participant was fitted with a four-marker set of reflectors. Three reflectors were placed on each foot to establish a transverse plane parallel to the plantar surface of each foot. The markers consisted of one on the posterior surface of the calcaneus as well as one on the distal end of the first and fifth metatarsal. Finally, a marker on the navicular bone's medial surface allowed for calculating position above its local transverse plane. The navicular position above this local transverse plane allowed for the assessment of the navicular position during static and dynamic navicular measurement. DocuSign Envelope ID: AE0EA240-29F9-4CBE-B922-361DCA2A9F90 viii Two Vicon motion capture systems were used for data collection in this study. The first system was used during the static stage. This eight-camera Vicon system had cameras placed in such a way as to create an intensely observed area measuring one cubic meter. A trained physical therapist put the participant's foot in subtalar neutral within this volume. Previous studies indicated that a trained PT could place a foot in a subtalar neutral with good reliability. The Vicon system essentially takes a snapshot of the ankle and the positions of the markers in the subtalar neutral position. The second Vicon system was established to observe walking on a treadmill. Participants walked on the treadmill barefoot at 3.5 miles per hour. Leg length was recorded for each participant, and 3.5 represented a Froude number of 45. During walking trials, navicular motion was tracked. Three trials were collected for each participant. Five samples of navicular position at midstrike were extracted, resulting in a total of fifteen samples extracted dynamic samples for each participant. The average navicular position at midstrike was then compared to the navicular position during the static trials. The navicular drop was then defined as the difference between the navicular position at midstrike and the navicular position during the static subtalar neutral.

Results: On the first day, the average right foot navicular drop was 13.3mm; on day two, this drop was measured at 13.5 mm. Further, the left foot demonstrated an average navicular drop of 14.1 mm on day one and 14.9 mm on day two. Pearson product correlations testing revealed significant correlations between day one and day two for navicular drop measurements (Right foot r =.75, Left foot r = .57, overall r = .66). Finally, there were no significant differences between day one and day two of collections. (Right foot p = .71, Left foot p = .10). DocuSign Envelope ID: AE0EA240-29F9-4CBE-B922-361DCA2A9F90 ix

Conclusion: Results in this study demonstrate that our technique is reliable for determining navicular drop. In congruence with the well-established base validity of the Vicon system, our method for assessing navicular drop has been determined to be both valid and reliable.

Clinical Relevance: This technique employed in the clinical setting will provide clinicians with a rigorous, trustworthy method of testing a client's foot health. Further, this method allows for the dynamic assessment of navicular drop and represents an advance over previously employed methods of navicular drop testing, which have questionable validity and reliability.

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