Anatomically Based Investigations of Total Ankle Arthroplasty
Open Access
- Author:
- Fauth, Andrew Ray
- Graduate Program:
- Kinesiology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 28, 2005
- Committee Members:
- Neil Sharkey, Committee Chair/Co-Chair
Stephen Jacob Piazza, Committee Member
John Henry Challis, Committee Member
Steven Howard Zarit, Committee Member
James Michelson, Committee Member - Keywords:
- ankle arthroplasty
talocrural joint
joint replacement
ankle - Abstract:
- The study addressed alignment and orientation issues of the talocrural joint with a specific emphasis on applications for total ankle arthroplasty (TAA). The first phase involved thorough morphological and geometrical characterizations of 8 cadaveric ankle joints, which were completed using a 3D digitization system and numerical optimization methods. The study also explored the design, use, and implantation of prototype surgical instrumentation and joint replacement components as a means of evaluating talocrural joint orientations. First, the 3D spatial orientations of easily identifiable and palpable anatomical landmarks were calculated along with clouds of points replicating the articular surfaces of the distal tibia, talus, and fibula. The articular surfaces of the tibia and talus were characterized geometrically as cylinders via numerical optimization. Results indicated that the size of the mean radius of curvature of the articular surfaces of the tali and tibiae were within the findings of previous research. Statistical comparisons between the cylinders fit to the tibia and the talus revealed significantly larger radii of curvature for the tibia. In addition, males had significantly larger radii of curvature than females. The articular surfaces were also separated into medial and lateral halves for separate cylinder fits, and comparisons of radius size were made between the medial and lateral fits for the tibia vs. the talus, males vs. females, and the medial and lateral fits vs. the original whole-fits. Joint surface orientations were identified via the cylinder fits and were compared to the 3D position and orientation of surrounding anatomical landmarks. These assessments yielded consistent and predictable findings in the coronal plane (neutral varus/valgus), confirming some traditional TAA alignment procedures. The orientations of the joint surfaces in the transverse plane were found to be highly variable, and as a result, no consistent relationship was identified that would predict the transverse orientation of the joint surfaces. Calculations were also made of the coronal and transverse orientations of vectors connecting anatomical landmarks such as the intermalleolar (IM) axis and edges of the anterior and posterior articular surfaces. Results showed that the orientations of the IM axes were highly variable in both planes, indicating that current TAA alignment procedures that approximate the alignment of the components based on the IM axis may be erroneous. The results from the initial orientation calculations were applied towards the development of prototype surgical alignment instrumentation and components for TAA. This instrumentation was used to perform TAA surgery and implant experimental TAA components to examine the joint orientations of 5 cadaveric ankles. The simple, congruent, cylindrical component system developed was based on the radius of curvature data from the cylinder optimizations, and allowed unrestricted translation and rotation of the components in the transverse plane that was designed determine the optimum TAA component orientation in this plane. The cylindrical components were inserted in place of the talocrural joint surfaces, and their orientation was measured at a static, neutral position to evaluate the accuracy of the cuts. Next, the feet were subjected to kinematic experiments involving cycles of plantarflexion and dorsiflexion. Initial and final orientations and translations of the components were calculated, along with intra-experimental rotational oscillations. Final component positions and orientations were compared with the spatial orientation of anatomical landmarks in order to identify repeatable alignment relationships. Analysis of the results showed a great deal of variance in the transverse plane orientation of the components, therefore a mean transverse plane orientation that was representative of all specimens was not identified. In addition, through the plantar/dorsiflexion trials, the components exhibited rotational oscillations in the transverse plane demonstrating that talocrural motion is multi-planar. The results of the study indicate that a more thorough understanding of the transverse orientations of talocrural joint surfaces is needed before reliable, predictable alignment criteria can be developed for TAA. Nevertheless, the current study identified orientations in the coronal and sagittal planes which confirm certain existing TAA alignment protocols, and also demonstrated that it is possible to develop instrumentation that can improve the accuracy of the TAA bone cuts.