Although optimal alignment is essential for improved function and implant longevity after TKA, we have less bony landmarks of tibia relative to femur. Trans-malleolar axis (TMA) is a reference line of distal tibia in the axial plane, which externally rotated relative to a ML axis of proximal tibia. We originally defined another reference axis associated with the orientation of tibial plafond, and then measured tibial torsion in the 3D-coordinate system. Three-dimensional CAD models of 20 tibiae were reconstructed based on pre-operative CT data from OA patients (16 females and 4 males, 73.8 ± 6.9 years old). TMA was a line connecting each apex of medial and lateral malleolus. The plafond axis (PLA) that we originally defined in this study was a line connecting each midpoint of medial and lateral margin of talocrural facet. In terms of interobserver correlation coefficiency and mean errors of the designated points to define those axes, TMA was found out to be 0.982, 3.14 ± 0.47 mm (medial), and 0.988, 4.88 ± 0.59 mm (lateral). Those of PLA were 0.997, 1.97 ± 0.53 mm (medial), and 0.995, 2.02 ± 0.44 mm (lateral). The tibial torsion was 16.3 ± 6.3°with reference to TMA, and 10.2 ± 8.4°to PLA. Based on these results, as for the rotational reference axis in the axial plain of distal tibia, we consider the plafond axis to be another reliable and reproducible axis, which is expected to be applicable in preoperative planning in TKA to reduce outliers of coronal alignment.
Reconstruction of the lateral ligaments of the ankle has been performed for many years, but few reports are available regarding the outcome after 10 years or longer, and there are no such reports on reconstruction with the more recently developed artificial ligaments. I report the clinical outcome and radiological findings.
On stress X-ray taken at the final examination, TTA improved preoperatively 19 degrees to 4 degrees postoperatively, and ADT improved from 12 to 5 mm. There was no marked development or progression of arthropathic changes. No allergic reaction to the artificial ligament material occurred in any patient. postoperatively and no patient had instability that became severe enough for reoperation to be required. As for arthropathic changes, in 3 patients with a TTA of 10 degrees or more postoperatively, progression of mild osteoarthritic changes was observed.