Ankle Arthritis Etiology Predicts Patterns of Gait Dysfunction: A Prospective Multivariate Gait Analysis

Category: Ankle; Ankle Arthritis; Basic Sciences/Biologics; Hindfoot Introduction/Purpose: Preoperative factors influencing functional disability imparted on the patient by ankle arthritis have not previously been assessed with gait analysis. The purpose of this study was to assess the influence of ankle arthritis etiology and deformity, measured radiographically, on gait performance in a dedicated gait lab utilizing a multisegment foot model. With three calcaneal and four metatarsal markers in addition to standard lower extremity markers, the modified Helen Haynes model allows for the evaluation of range of motion (ROM) within the 'ankle-hindfoot segment.' The primary hypothesis was that three- dimensional ankle-hindfoot segment ROM would be more restricted in patients with post-traumatic ankle arthritis than other etiologies. The secondary hypothesis was that temporospatial and kinetic measures would not vary by etiology. Methods: A longitudinal cohort of 183 patients with end-stage ankle arthritis were prospectively enrolled from 2008-2018. Mean age was 61, BMI 29, and 56% were male. Four etiologic groups were defined: Post-fracture (100), arthritis caused by planovalgus foot deformity (23), chronic instability associated with cavovarus (32), and miscellaneous (28), comprised of inflammatory (7), idiopathic (6), instability without deformity (5), septic (2), and avascular necrosis (3) as causes. The four-segment Milwaukee foot model was used in a dedicated gait lab with a 12-camera motion capture system. Gait data was collected over a minimum 20 gait cycles across a 10-meter walkway. Kinetic data was simultaneously collected with two force plates embedded in the walkway operating at 1 MHz. AP and lateral tibiotalar angles, lateral talus-first metatarsal angles, calcaneal pitch, and tibiotalar ratio were measured. Multivariate regression analyzed the effect of etiology and radiographic measures on gait function, controlling for age, gender, and BMI. Results: The primary hypothesis was confirmed. Sagittal plane ankle-hindfoot segment ROM was lower in post-traumatic and higher in valgus patients compared to other etiological groups (P