RANGE OF MOTION OF THE HINDFOOT FOLLOWING ANKLE ARTHRODESIS: A PROSPECTIVE ANALYSIS.

Abstract

Introduction: Gait analysis studies of patients following ankle arthrodesis have demonstrated a functional gait, largely due to tarsal hypermobility compensating for lost tibio-talar motion. We present a prospective radiographic study comparing the pre and post-operative range of motion of the foot following ankle arthrodesis. In this study, we introduce a radiographic technique using reliable anatomic landmarks to measure sagittal range of motion of the foot after ankle arthrodesis.

Materials and Methods: Between 2002 and 2007, we performed 154 arthrodesis procedures of the ankle. Patients were suitable for inclusion in this study if an isolated arthrodesis of the ankle was performed for post traumatic arthritis with a minimum of 1 year follow-up without any additional hindfoot operations. Preoperative and post-operative passive plantar flexion and dorsiflexion radiographs were obtained in a standardized fashion. Anatomic landmarks were then used to measure and compare tibio-talar, mid-tarsal, and subtalar movement.

Results: There were 48 patients who met the inclusion criteria for this study. Preoperatively, the mean measured motion was as follows: total sagittal motion 35o, tibio-talar motion18o, mid-tarsal (transverse tarsal + naviculo cuneiform + tarsometatarsal joints) motion 12o (34% of pre-op sagittal arc), subtalar motion 5.5o (15% of pre-op sagittal arc), and mid-tarsal + subtalar motion 17.5o (49% of pre-operative sagittal motion). These changed post operatively to a mean motion as follows: total sagittal motion 18.5o, (52% of preoperative sagittal motion), mid-tarsal motion 10o (28% of pre-op sagittal arc), subtalar motion 10.5o (27% of pre-op sagittal arc), and mid-tarsal + subtalar motion 20.5o (54% of pre-operative sagittal motion).

Discussion: This study presents an accurate and reproducible means of measuring the sagittal plane range of motion of the hindfoot and ankle, and documents the presence of increased motion in the subtalar and talonavicular joints after ankle arthrodesis.