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.

Background: The Evans osteotomy has been proven to be very effective in treating flatfoot deformity in adults. However, it has not been shown whether the site of osteotomy influences the contact areas and peak pressures within the subtalar joint. It is hypothesized that the posterior facet of the calcaneus rotates posteriorly and laterally resulting in altered contact characteristics and peak pressures in the subtalar joint.

Materiala and Methods: We used a finite-element model (FEA) of the hindfoot. Computed tomography slides of patients who suffered from adult flatfoot deformity were prepared by means of open-source software and converted into a three-dimensional model of the hindfoot. The FEA model allows the virtual performance of an osteoteomy and simulates force transmissions through the hindfoot and calculates joint contact characteristics and peak pressure alterations as well. Two different kind of osteotomies were tested:

an osteotomy 10mm proximal to the calcaneocuboid joint line and

Results: There were small but significant differences found between osteotomies done either close to the calcaneocuboid joint or directly adjacent to the posterior facet. At both sites the posterior calcaneal facet rotated posteriorly and laterally. However we found a significant decreases in contact areas and raises in peak pressures within the subtalar joint in cases where the osteotomy was performed close to the posterior calcaneal facet.

Summary: This study presents the effects of virtual Evans osteotomies on the subtalar joint and their dependence upon the site of the osteotomies.