How Do Hindfoot Fusions Affect Ankle Biomechanics: A Cadaver Model

Abstract

Background While successful subtalar joint arthrodesis provides pain relief, resultant alterations in ankle biomechanics need to be considered, as this procedure may predispose the remaining hindfoot and tibiotalar joint to accelerated degenerative changes. However, the biomechanical consequences of isolated subtalar joint arthrodesis and additive fusions of the Chopart's joints on tibiotalar joint biomechanics remain poorly understood. Questions/purposes We asked: What is the effect of isolated subtalar fusion and sequential Chopart's joint fusions of the talonavicular and calcaneocuboid joints on tibiotalar joint (1) mechanics and (2) kinematics during loading for neutral, inverted, and everted orientations of the foot? Methods We evaluated the total force, contact area, and the magnitude and distribution of the contact stress on the articular surface of the talar dome, while simultaneously tracking the position of the talus relative to the tibia during loading in seven fresh-frozen cadaver feet. Each foot was loaded in the unfused, intact control condition followed by three randomized simulated hindfoot arthrodesis modalities: subtalar, double (subtalar and talonavicular), and triple (subtalar, talonavicular, and calcaneocuboid) arthrodesis. The intact and arthrodesis conditions were tested in three alignments using a metallic wedge insert: neutral (flat), 10°i nverted, and 10°everted. Results Tibiotalar mechanics (total force and contact area) and kinematics (external rotation) differed owing to hindfoot arthrodeses. After subtalar arthrodesis, there were Each author certifies that he or she, or a member of their immediate family, has no commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article. Clinical Orthopaedics and Related Research ®A Publication of The Association of Bone and Joint Surgeons® decreases in total force (445 ± 142 N, 95% CI, 340-550 N, versus 588 ± 118 N, 95% CI, 500-676 N; p \ 0.001) and contact area (282 mm 2 , 95% CI, 222-342 mm 2 , versus 336 ± 96 mm 2 , 95% CI, 265-407 mm 2 ; p \ 0.026) detected during loading in the neutral position; these changes also were seen in the everted foot position. Hindfoot arthrodesis also was associated with increased external rotation of the tibiotalar joint during loading: subtalar arthrodesis in the neutral loading position (3.3°± 1.6°; 95% CI, 2°-4.6°; p = 0.004) and everted loading position (4.8°± 2.6°; 95% CI, 2.7°-6.8°; p = 0.043); double arthrodesis in neutral (4.4°± 2°; 95% CI, 2.8°-6°; p = 0.003) and inverted positions (5.8°± 2.6°; 95% CI, 3.7°-7.9°; p = 0.002), and triple arthrodesis in all loaded orientations including neutral (4.5°±1.8°; 95% CI, 3.1°-5.9°; p = 0.002), inverted (6.4°± 3.5°; 95% CI, 3.6°-9.2°; p = 0.009), and everted (3.6°± 2°; 95% CI, 2°-5.2°; p = 0.053) positions. Finally, after subtalar arthrodesis, additive fusions at Chopart's joints did not appear to result in additional observe...

Risk Factors for Failure of Total Ankle Arthroplasty With a Minimum Five Years of Follow-up

“…19 This finding makes sense: hindfoot fusion has been shown to lead to altered tibiotalar loading patterns. 11 The resulting eccentric stresses on the implant could consequently lead to accelerated implant failure, whether by loosening, joint instability, or polyethylene wear and osteolysis. However, this should not discourage surgeons from performing hindfoot fusions in patients with TAA when indicated, as these patients can still have good outcomes with significant clinical and functional improvements from their baseline.…”

Triple Arthrodesis for Adult-Acquired Flatfoot Deformity

“…7 Another cadaver model found subtalar arthrodesis to have the most detrimental effect on tibiotalar biomechanics, and additive fusions of the talonavicular and calcaneocuboid joints did not further significantly affect the ankle joint. 39 It is, however, difficult to apply this cadaver model to actual weightbearing and gait following these procedures. Despite overall positive outcomes following triple arthrodesis, it is important to keep in mind that over- and undercorrection, malunion, and nonunion are concerns and that there is a steep learning curve with regard to correction, appropriate joint preparation, fixation, and soft tissue handling.…”

Effect of Complete Syndesmotic Disruption and Deltoid Injuries and Different Reduction Methods on Ankle Joint Contact Mechanics

“…Given that the loads imparted to the specimen through the hydraulic testing frame and Achilles tendon were the same in the intact and disrupted conditions and that peak contact pressure did not change, it was implied that tissues outside of the sensor’s footprint experienced higher loads. 10 Tissues experiencing higher loads could include the fibula or medial gutter. Alternatively, although the sensor used in the current study was specifically designed for use in ankles, 2 there could have been some areas on the talar dome outside of the sensor footprint that were experiencing more loads.…”