Transverse Plane Rotational Misalignment of Ankle Arthrodesis and Arthroplasty in Cadaveric Gait Simulation

Abstract

End-stage arthritis of the ankle is a debilitating disease that is commonly treated surgically with arthrodesis and arthroplasty of the ankle joint. Misalignment of the ankle joint occurs in both of these surgeries, and for both procedures, misalignment can negatively impact patient outcomes. The goal of this thesis was to examine misalignment of these procedures in cadaveric gait simulation. Using cadaveric specimens in orthopaedics and biomechanics allows for novel concepts or evaluations of procedures to be performed without the potential harm to a patient. A robotic gait simulator was used to simulate stance phase of gait on cadaveric foot specimens, to examine multiple alignments of ankle arthrodesis and arthroplasty. Ground reaction forces and tibia-to-ground kinematics were replicated by the simulator from patients postoperatively for each surgery. Ankle arthrodesis was simulated using a custom two-plate fixture that allowed for the ankle to be fused in multiple transverse plane rotational alignments of the surgery. Misalignment of the ankle arthrodesis showed minimal significant changes to joint ranges of motion of the foot, but analysis of joint angles throughout stance phase showed an abnormal position of the naviculocuneiform and cuboid-fifth metatarsal joints due to internal rotational misalignments. No changes were seen in the plantar pressure distribution analysis due to misalignment. Ankle arthroplasty was simulated using a custom surgical technique and fixture, designed to implant the Salto Talaris total ankle system into cadaveric specimens such that the neutral alignment replicated the in vivo surgery, but transverse plane rotational misalignments could be applied to the arthroplasty. Transverse plane rotational misalignment of the arthroplasty altered joint kinematics of not only the ankle joint, but distal foot joints as well. Plantar pressure distribution was not changed due to arthroplasty misalignment. These studies quantified the effect of transverse plane rotational misalignment of each surgery on joint kinematics and plantar pressure distribution. The results suggest that arthroplasty misalignment may have a greater effect on foot function than arthrodesis misalignment, but comparisons between the studies are difficult due to the differences in loading conditions between the studies. Analyses of joint stresses would allow for more complete understanding of the biomechanical changes the foot undergoes due to surgical misalignment, and could further the clinical knowledge of joint loading after these procedures.