Arthrodesis for post-traumatic ankle osteoarthritis leads to a reduced function of the affected limb with changes in gait and pedobarography: a retrospective cross-sectional study

BACKGROUND: Ankle arthrodesis is an established procedure for end-stage ankle osteoarthritis. Besides the known limited functionality, gait and foot arch changes are accompanying pathologies, which are little investigated. The aim of the present study was to determine the influence of ankle arthrodesis on gait, pedobaropraphy and functional outcome. METHODS: Thirtyfive patients with unilateral ankle joint fusion after post-traumatic osteoarthritis and a mean follow-up of 60.8 months (SD 18.5, range 32-92) were included. Primary outcome were a 3-D gait analysis including pedobarography. American Orthopaedic Foot and Ankle Society (AOFAS) Score, douleur neuropathique (DN4), EQ-5D-3 L, numeric pain rating scale (NRS), Olerud-Molander Ankle Score (OMAS), painDETECT, short form 36 (SF-36), short musculoskeletal function assessment-German version (SMFA-D) and a clinical examination were secondary outcomes. RESULTS: The AOFAS scores showed predominantly fair or poor results (Rearfoot: 48.6% fair, 34.3% poor; Midfoot 42.9% fair, 25.7% poor), while the SMFA tended to reflect mild dysfunction (bother index 31.7, functional index 27.5). Pain-related questionnaires showed a low incidence of pain (DN4 4.1, NRS 2.2, painDETECT 11.6). Kinematic changes were only marginally observed, while the spatio-temporal parameters showed relevant asymmetries between the fused and healthy side. The pedobarography revealed, in addition to other differences, a reduced maximum contact area on the arthrodesis side compared to the healthy side. CONCLUSIONS: Arthrodesis of the ankle joint results in significant limitation of daily activities with reduced function of the affected limb. The impact of ankle arthrodesis go well beyond the loss of extension and flexion, with changes in spatial and temporal movement, weight bearing profile and contact surface. However, results of pain questionnaires show a good result with regard to the main goal of the arthrodesis, the elimination of pain. TRIAL REGISTRATION: DRKS, DRKS00033495. Registered 14 March 2024, https://www.drks.de/DRKS00033495 .