The motion between components in a mobile-bearing total ankle replacement measured by cone-beam CT scanning.

Background: To measure the motion of polyethylene insert and implant components of mobile-bearing total ankle replacement (TAR) by cone-beam CT scanning.

Methods: 10 TAR patients with high amount of clinical motion after the CCI implant (Ceramic Coated Implant; Wright Medical Technology, Arlington, TN, USA) with average age at operation 64,3 years (range 47-84) and average clinical total range of motion 42 degrees (range 35-55) were included.

Results: The average total range of motion between the insert and the tibial component was 0.8mm (range 0-2) in the coronal plane, and 2.9mm (range 1-6) in the sagittal plane. There was wide variation in the axial rotation measurements between the components.

Conclusion: We found measurable motion between the mobile-bearing insert and the tibial component in all planes. The relevance of this motion to the function and long-term survival of the TAR remains to be determined.