Summary

Even in the everyday position like prone position, PS-TKA showed significantly large Anterior tibial translation than BCS-TKA.

Abstract

Purpose

The purpose of this study was to evaluate the anterior tibial translation (ATT) in the prone position after total knee arthroplasty (TKA).

Methods

Twenty one subjects (21 knees) undergoing bi-cruciate substituting (BCS)-TKA (Journey II: Smith and Nephew) and 24 subjects (24 knees) undergoing posterior stabilizing (PS)-TKA, were included in this study. Approximately 6 months after surgery, and when the subjects had recovered their range of knee motion, following the Mae’s method, accurate lateral radiographic imaging of the knee was performed with full knee extension in supine position and prone position. The maximal protrusion length of the femoral posterior component, posteriorly to the extension line parallel to the tibial shaft from the edge of the posterior tibial plateau was measured on the lateral radiographs. The length difference between the prone and supine position was regarded as the prone-ATT. The posterior protrusion length of the femoral component, and the prone-ATT were compared between BCS and PS-TKAs.

Results

The posterior protrusion length of the femoral component in supine position were, BCS-TKA 4.3±1.9mm, and PS-TKA 8.7±2.3mm, respectively. The length in prone position were, BCS-TKA 4.8±2.3mm, and PS-TKA 10.7±2.2m, respectively. Although the length was not changed by the position in BCS-TKA, PS-TKA showed significantly larger posterior protrusion length of femoral condyle in prone position when compared with that in supine position. PS-TKA showed significantly large posterior protrusion length of femoral component when compared with BCS-TKA. The prone-ATT were, BCS-TKA 0.7±2mm, and PS-TKA 2±1.9mm. PS-TKA showed significantly larger ATT than that of BCS-TKA.

Conclusion

Even in the everyday position like prone position, PS-TKA showed significantly large ATT than BCS-TKA. Better anterior knee laxity after TKA would be influenced to the clinical results or discomfort feeling of the BCS-TKA.