Summary

In our study shows that residual varus due to HKA and aHKA as well as undercorrection of LDFA increases the satisfaction score after surgery, however, the increase of LDFA is the most important factor with statistically significant difference.

Abstract

Background

The success of TKR is multifactorial. The benefit from this procedure is to improve pain and increase the patients' quality of life style. Traditionally, TKR is performed with mechanical alignment, but recent studies observed great variability of constitutional alignment between each patient, so the variability of patient satisfaction with this philosophy could be related to the change of anatomy.

Purpose

The purpose of the article is to compare patient satisfaction outcomes after total knee replacement with mechanical alignment philosophy in patients who had preoperative varus deformity and postoperative obtained residual varus or neutral alignment.

Material And Methods

Analytical, retrospective partial retrospective, longitudinal observational study from 2016-2020. We measured preoperatively and postoperatively the mechanical axis, arithmetic mechanical axis, joint obliquity, LDFA, MPTA. For statistical analysis we divided the study into two parts. The first part consists of the comparison of the means of the FJS-12 score between both groups. In the second part we divided the sample into two groups, patients with scores higher or lower than 68 points on the FJS-12 scale in which we obtained a Spearman correlation and compared their respective means. Finally, we performed a multiple linear and binomial logistic regression of each section with the variables that were statistically significant in order to determine the factors that most influence the change in the scale score.

Results

In the last 5 years and after performing the inclusion and exclusion criteria, we obtained a total of 35 patients and 42 TKR with mechanical alignment. We found better results in satisfaction scores when HKA sub-correction, sub-correction or correction to neutral of LDFA, maintaining the same HKA and aHKA as well as obtaining postoperative varus by aHKA. However in multiple linear regression, the most important factors influencing the FJS-12 score are: Postoperative LDFA and keeping the same mechanical axis (R2 of 424, p=.000).
In the second part, the correlation observes that postoperative LDFA was shown to be the most important factor in satisfaction scores. The oddis ratio shows that the risk of presenting low satisfaction scale scores increases 19.09 times if we leave the patient with neutral alignment by aHKA. Similarly, changing the arithmetic axis increases the risk of low satisfaction scores by 9.91 times.
Binomial logistic regression for the second section shows us that the most important factor for scoring greater than 68pts is postoperative LDFA.

Conclusions

Our study shows that residual varus by HKA and aHKA as well as undercorrection of LDFA increases the satisfaction score after surgery, however, increased LDFA is the most important factor with statistically significant difference.