Summary

Bony anatomy and ligamentous laxity are two independant data which should be assessed individually during total knee arthroplasty.

Abstract

Purpose

The goal of this study was to analyse the correlation between the bony morphotype measured by the CPAK classificationand the mediolateral laxity measured during surgery. The hypothesis tested was that there was i significant statistical link between the CPAK classification and the mediolateral laxity in extension.

Methods

All patients operated for TKA by two experienced surgeons between 2011 and 2020 were eligible. Five hundred and twenty cases were randomly selected from those with a complete anatomical analysis.
The CPAK classification was analyzed as categorical data. Arithmetic Hip-Knee-Ankle (aHKA) and Joint Line Orientation (JLO) angles were expressed with their mean and standard deviation, and then transformed into categorical data according to McDessi.

Results

There was a significant difference between the mean values of the medial laxity (p<0.001), but not for the lateral laxity (p=0.053) for the different CPAK classes.
There was a significant difference between the mean values of the medial laxity (p<0.001) but not the lateral laxity (p=0.09) for the different aHKA classes. There was a weak significant negative correlation between the numerical values of the aHKA angle and of the medial (p<0.001) and the lateral laxity (p<0.001). There was no significant difference between the mean values of the medial (p=0.12) or the lateral laxity (p=0.75) for the different JLO classes. There was no correlation between the numerical values of the JLO angle and of the medial (p=0.09) or the lateral laxity (p=0.73).

Conclusion

It was not possible to predict the ligamentous laxity from the bony anatomyduring total knee arthroplasty. Bony anatomy and ligamentous laxity are two independant data which should be assessed individually during total knee arthroplasty.