Multisegment Foot Kinematic and Kinetic Compensations in Level and Uphill Walking Following Tibiotalar Arthrodesis

Background: Foot and ankle movement alterations following ankle arthrodesis are still not well understood, particularly those that might contribute to the documented increase in adjacent joint arthritis. Generalized tarsal hypermobility has long been postulated, but not confirmed in gait or functional movements. The purpose of this study was to more thoroughly evaluate compensation mechanisms used by arthrodesis patients during level and uphill gait through a variety of measurement modalities and a detailed breakdown of gait phases. Methods: Level ground and uphill gait of 14 unilateral tibiotalar arthrodesis patients and 14 matched controls was analyzed using motion capture, force, and pressure measurements in conjunction with a kinetic multisegment foot model. Results: The affected limb exhibited several marked differences compared to the controls and to the unaffected limb. In loading response, ankle eversion was reduced but without a reduction in tibial rotation. During the second rocker, ankle dorsiflexion was reduced, yet was still considerable, suggesting compensatory talar articulation (subtalar and talonavicular) motion since no differences were seen at the midtarsal joint. Also during the second rocker, subjects abnormally internally rotated the tibia while moving their center of pressure laterally. Third rocker plantarflexion motion, moments, and powers were substantially reduced on the affected side and to a lesser extent on the unaffected side. Conclusion: Sagittal plane hypermobility is probable during the second rocker in the talar articulations following tibiotalar fusion, but is unlikely in other midfoot joints. The normal coupling between frontal plane hindfoot motion and tibial rotation in early and mid stance was also clearly disrupted. These alterations reflect a complex compensatory movement pattern that undoubtedly affects the function of arthrodesis patients, likely alters the arthrokinematics of the talar joints (which may be a mechanism for arthritis development), and should be considered in future arthrodesis as well as arthroplasty research. Level of Evidence: Level III, comparative study.