Does multi-axial postoperative alignment beyond 3 degrees of neutral in mechanically aligned total knee arthroplasty impact survivorship? An updated systematic review and meta-analysis.

Hayden Ebb, Dr. Samuel Macdessi, Jil Wood, Dr. Luke Corban, Dr. Stephen Bested, Dr. Nickson Ning

Introduction:

With the global incidence of total knee arthroplasty (TKA) projected to rise sharply by 2030, ensuring long-term implant survival is a growing clinical priority. Mechanical alignment (MA), which aims to achieve neutral limb alignment postoperatively, has been the standard surgical technique since the mid-1980s. While many studies have supported the ±3° threshold in the coronal plane, emerging alignment strategies and imaging technologies have prompted debate about the relevance of this traditional benchmark. Additionally, sagittal and axial alignment—often overlooked—may also influence prosthetic outcomes.

Aim:

This systematic review and meta-analysis aims to evaluate whether deviations beyond ±3° from neutral alignment in the coronal, sagittal, or axial planes are associated with increased rates of prosthetic failure or revision in mechanically aligned TKAs. It also seeks to consolidate existing evidence using gold-standard imaging methods, contributing to a more comprehensive understanding of survivorship in three dimensions.

Method:

A systematic search was conducted across six major databases (Embase, MEDLINE, PubMed, Scopus, Web of Science, and Orthosearch). After removing duplicates, 898 records were screened by two independent reviewers (HE and LC) using Rayyan. A third reviewer (JW) was involved to resolve any discrepancies in study inclusion. Forty articles were initially selected for full-text review; however, this number was reduced to 38 due to availability. Risk of bias assessment and application of exclusion criteria are still underway. Data extraction is focused on postoperative alignment measurements, imaging modality, implant design, and revision outcomes. The review process is being conducted in accordance with PRISMA guidelines.

Conclusions:

Given the variability in surgical techniques, implant designs, and follow-up durations across studies, this review may not definitively answer the alignment-survivorship question. However, we hope it meaningfully contributes to the evolving evidence base, guiding better outcomes for future TKA patients.