Varus-Valgus Constrained Prostheses in Revision Total Knee Arthroplasty: A Retrospective Study of Mid- to Long-Term Outcomes

TL;DR

This study evaluates the effectiveness of varus-valgus constrained prostheses in revision knee surgeries, showing high survival rates and improved patient outcomes over mid- to long-term follow-up.

Contribution

The study provides empirical evidence on the mid- to long-term outcomes of using varus-valgus constrained prostheses in complex revision knee surgeries.

Findings

Patients showed significant improvements in range of motion, Oxford Knee Score, and Knee Society Score post-surgery.

The implant survival rate was 98.3% at 60 months, with low complication rates for infections and aseptic loosening.

Radiolucent lines were observed in some components but did not significantly impact overall survival rates.

Abstract

Introduction

Total knee arthroplasty (TKA) is a well-established treatment for end-stage knee arthritis, providing substantial pain relief and functional improvement. However, the increasing need for revision TKA (RTKA) due to factors such as polyethylene wear, aseptic loosening, periprosthetic infection, and instability presents significant challenges. This study aimed to assess the mid- to long-term clinical and radiographic outcomes, implant survival rates, and complications associated with RTKA using a varus-valgus constrained (VVC) prosthesis.

Methods

This retrospective observational study analyzed patients who underwent RTKA with either VVC or condylar constrained knee prostheses at Sunshine Hospitals in Hyderabad, India, between January 1, 2010 and January 1, 2020, with a minimum follow-up of four years. Data were obtained from the joint registry. The inclusion criteria encompassed patients who underwent single-stage or two-stage RTKA for any indication, including periprosthetic joint infection (PJI), instability, or aseptic loosening. Functional outcomes were assessed using the Knee Society Score (KSS) and Oxford Knee Score (OKS), while radiolucent lines were evaluated with the updated Knee Society Roentgenographic Score. Implant survival rates were analyzed using Kaplan-Meier survival analysis.

Results

A total of 139 patients met the eligibility criteria for the final analysis, with a mean follow-up of 6.3 ± 2.4 years. The cohort had a mean age of 64.8 ± 7.8 years, comprising 90 females (64.7%), and a mean BMI of 29.3 ± 5.4. The primary indications for RTKA were PJI (70 cases, 50.4%) and aseptic loosening (47 cases, 33.8%). Significant postoperative improvements were observed in range of motion (from 73.2 degrees preoperatively to 104.3 degrees postoperatively), OKS (from 14.3 to 29.2), and KSS (from 48.2 to 74.9), all of which were highly significant (p < 0.001). Radiolucent lines were detected in 13 femoral components (9.35%) and 18 tibial components (12.95%), with one case progressing to aseptic loosening. Complications included superficial surgical site infections (two cases, 1.4%) and persistent prosthetic joint infections (three cases, 2.2%). Kaplan-Meier survival analysis demonstrated a 98.3% survival rate at 60 months, with reoperation for any cause as the endpoint.

Conclusions

The use of VVC prostheses in RTKA yields favorable long-term outcomes, demonstrating high survival rates and significant functional improvements. While managing bone defects and preventing postoperative infections remain challenges, meticulous surgical techniques and comprehensive postoperative care play a crucial role in achieving reliable results. These factors contribute to improved patient outcomes and enhanced prosthesis longevity in complex RTKA cases.

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