# The Usefulness of the Lateral Femoral Epicondyle as a Landmark for Evaluating Leg Length Discrepancy in Robot-Assisted Total Hip Arthroplasty

## TL;DR

This study examines whether using the lateral femoral epicondyle as a landmark improves leg length measurement accuracy in robot-assisted hip surgery.

## Contribution

The study introduces the lateral femoral epicondyle as a practical and time-saving alternative landmark in robotic hip surgery.

## Key findings

- Using the lateral epicondyle showed similar leg length discrepancy results compared to the intrapatella landmark.
- No significant differences in leg length measurements were found between the three groups.
- The lateral epicondyle method may offer a more convenient technique for robotic-assisted hip arthroplasty.

## Abstract

Objective: One of the biggest advantages of robot-assisted hip replacement surgery is the reduction in dislocation rates because of proper implant positioning and accurate measurement of the leg length. Therefore, we aimed to investigate the usefulness of using the lateral epicondyle as a landmark to minimize errors in leg length measurement. Methods: This retrospective study was conducted between September 2023 and March 2025 and included 24 patients who underwent robotic-assisted total hip arthroplasty (rTHA, Group I). These procedures were performed by two experienced surgeons. The data were compared with results from two additional groups: patients who underwent rTHA using the intrapatella landmark (Group II) and those who underwent conventional total hip arthroplasty (cTHA) without robotic assistance (Group III). Leg length measurements were evaluated using postoperative X-rays and intraoperative robotic monitoring. ANOVA and Student’s t-test were used to analyze the significance of the variables (p < 0.05). Results: The mean X-ray LLD (xLLD) was 1.39 mm (−7.43–11.63 mm) and Mako LLD (mLLD) was 4.77 mm (−6–12 mm) in Group I. The mean xLLD was 3.54 mm (−5.02–13.6 mm) and mLLD was 4.20 mm (−22–14 mm) in Group II. The mean xLLD was 4.06 mm (−8.62–21.2 mm) in Group III. There was no statistical significance between the three groups (p = 0.241). Conclusions: Using the lateral femoral epicondyle as a landmark for the limb length measurement is a viable alternative to the intrapatella landmark in rTHA. This method may save time and offer and more convenient technique in measuring leg length changes during robotic-assisted total hip arthroplasty.