Evaluation of Medial Posterior Tibial Slope and Medial Posterior Capsule Slope in Total Knee Arthroplasty

Abstract

Objective: In total knee arthroplasty (TKA), it is important to reconstruct the knee alignment precisely to have satisfactory outcomes in terms of function, desensitization, and durability. In the coronal and axial plane, there is vast literature concerning alignment. However, the proper alignment in the sagittal plane and its clinical impact on function and outcome has not been studied to any great extent. Although the posterior tibia slope (PTS) has been proven to be important in TKA, and used when cutting the proximal tibia, it is difficult to measure PTS intraoperatively, and also it differs between normal and degenerative knees.

Methods: We focused on the articular capsule insertion on the tibia, which is more detectable intraoperatively. We defined the posterior capsule slope (PCS) as a new index, and evaluated and compared it with PTS in 51 autopsied knees. We measured the angle between the anterior cortex of the tibia, as one of the axes, and the line connecting the anterior edge and the posterior edge of the medial tibia plateau, and defined it as PTS. We also measured the angle between the anterior cortex of the tibia and the line connecting the anterior edge and the posterior edge of the capsule insertion point and defined it as PCS. We compared the data between PTS and PCS in terms of gender, side and whether there was the presence, or not, of degenerative change.

Results: There was a strong correlation between PTS and PCS, though there were no statistically significant difference between the two parameters. This was the same in all groups.

Conclusion: PCS may be useful for reconstructing the proper sagittal alignment in TKA.