# Determining the effect of femoral anteversion and hip alignment parameters on lower limb and knee alignment post-total hip arthroplasty

## TL;DR

This study examines how hip replacement surgery affects leg and knee alignment, finding that femoral anteversion plays a key role in influencing biomechanics and potential knee osteoarthritis.

## Contribution

The study identifies femoral anteversion as a critical factor in post-THA alignment changes and suggests its controlled adjustment could improve outcomes.

## Key findings

- Femoral anteversion is a key determinant of valgus alignment in the operative leg and lateral patellar tilt.
- Increased femoral offset and hip osteoarthritis diagnosis are associated with alignment changes post-THA.
- Contralateral leg alignment is influenced by ipsilateral hip alignment changes and patient age.

## Abstract

Total hip arthroplasty (THA) aims to restore hip joint alignment in patients with osteoarthritis (OA) or osteonecrosis of the femoral head (ONFH). While THA directly affects hip alignment, it also influences leg and patellar alignment, potentially altering knee biomechanics and accelerating osteoarthritis progression. Postoperative alignment changes commonly include increased varus alignment in the operative leg and valgus alignment in the contralateral leg. However, the factors contributing to these changes remain unclear, particularly the role of femoral anteversion. This study analyzed 228 patients who underwent hybrid THA, assessing preoperative and postoperative radiographic parameters, including femoral anteversion, femoral offset, hip center shift, and leg length. Multiple linear regression identified factors influencing alignment changes. Femoral anteversion emerged as a key independent determinant affecting valgus alignment of the operative leg and lateral patellar tilt. Increased femoral offset and diagnosis of hip OA were also associated with alignment changes, while contralateral alignment was influenced by ipsilateral HKAA changes and patient age. These findings suggest that increased femoral anteversion following THA may mitigate excessive varus loading and protect against secondary knee OA. Accurate control of anteversion, supported by navigation or artificial intelligence (AI)-assisted planning, could optimize postoperative biomechanical balance and long-term outcomes.