# Factors Influencing the Postoperative Flexion Angle in Cruciate-Sacrificing Rotating Platform of Total Knee Arthroplasty

## TL;DR

This study identifies factors influencing improved knee flexibility after a specific type of knee replacement surgery.

## Contribution

The study is one of the few to investigate factors affecting range of motion in cruciate-sacrificing rotating platform TKA.

## Key findings

- Preoperative and postoperative knee angles significantly differed between groups with good and poor flexion improvement.
- The ɤ angle was significantly associated with improved postoperative flexion range of motion.
- KOOS pain and activity scores showed significant differences between the two groups.

## Abstract

Background: Various factors affect the improvement of range of motion (ROM) after total knee arthroplasty (TKA). However, there are few reports specific to cruciate-sacrificing rotating platform (CSRP) TKA. In this study, factors affecting postoperative ROM improvement of CSRP TKA were investigated.

Methods: The study included 79 patients with knee osteoarthritis who underwent unilateral CSRP TKA at our institution. The group with an improvement of 5° or more (Δflexion angle) than the preoperative was defined as the good Δflexion group (38 knees), and that with less than 5° was defined as the poor Δflexion group (41 knees). The assessments were performed one day before and one year after surgery. Factors including rest and walking pain, knee flexion and extension angle, isometric knee extension strength, the five subscales of Knee injury and Osteoarthritis Outcome Score (KOOS), α, β, γ and δ angles, femoro-tibial angle (FTA), and condylar twist angle were assessed. Unpaired t-test, Mann-Whitney U test, and Chi-square test were used to test differences between the good and poor Δflexion groups. Multiple logistic regression examined the association between each factor and the dependent variables (good Δflexion or poor Δflexion).

Results: Significant differences in the preoperative knee flexion, postoperative knee flexion, preoperative knee extension, and postoperative knee extension angles, postoperative KOOS pain and activity of daily living, β, ɤ angles were observed between the good and poor Δflexion groups. The model Chi-squared test revealed that the ɤ angle was significantly affected by the Δflexion angle.

Conclusions: With the CSRP TKA, flexion insertion of the femoral component was associated with postoperative flexion ROM improvement.