# Prediction of Range of Motion in Patients After Total Knee Arthroplasty by Shear Wave Elastography

## TL;DR

This study explores how changes in muscle and tendon elasticity can predict knee mobility after surgery.

## Contribution

A novel use of shear wave elastography to predict post-surgery knee range of motion.

## Key findings

- Combining patient data and elasticity measurements improved prediction accuracy to 79%.
- Elasticity measurements alone predicted group classification with 68% accuracy.
- Early post-operative elasticity data significantly enhanced prediction sensitivity to 92%.

## Abstract

Introduction. We hypothesized changes in the elasticity in quadriceps and patella tendon before and after total knee arthroplasty would be correlated with a post-operative range of motion after total knee arthroplasty. To prospectively assess the post-operative range of motion after total knee arthroplasty, logistic regression was adopted with elasticity in the quadriceps and patella tendons were measured using shear wave elastography (SWE). Materials and Methods. From March 2021 to June 2021, SWE was performed on 95 patients (86 women; aged 57–85, mean 70.62 ± 5.49 years) preoperatively and 2 days after total knee arthroplasty. Elasticity at quadriceps and patellar tendons were measured with full flexion and extension using SWE. Based on the range of motion after surgery at 56 days, we divided the patients into two groups (Group A > 120 degrees; group B < 120 degrees). Using a logistic regression algorithm, classification between groups was performed. For the input of algorithm, patient information, the elasticity of quadriceps and patella tendons preoperatively and two days after total knee arthroplasty were used. Results. The accuracy of predicting group using only patient information was 62%, whereas using only elasticity was 68%. Furthermore, combining information and elasticity before and after surgery at 2 days, accuracy, sensitivity, specificity was 79%, 92%, 56%. Conclusions. Combined with patient information, elasticity measured by SWE at pre-op and early post-op periods could be effective to predict the performance of postoperative ROM. This algorithm could provide direction for rehabilitation.