# Anatomical relationship between the intertrochanteric line and femoral neck osteotomy level in direct anterior approach total hip arthroplasty: a 3D morphometric and cadaveric validation study

## TL;DR

This study identifies the intertrochanteric line as a reliable landmark for femoral neck osteotomy in hip replacement surgery.

## Contribution

The study introduces the intertrochanteric line height as a reproducible anatomical reference for femoral neck osteotomy in direct anterior approach total hip arthroplasty.

## Key findings

- ITL-H is a consistent anatomical landmark with no sex difference in height.
- An osteotomy 23 mm above ITL-H achieves high success rates in preserving calcar bone.
- Individualized preoperative planning is still recommended for optimal outcomes.

## Abstract

Inaccurate femoral neck osteotomy is a recognized technical challenge in direct anterior approach total hip arthroplasty (DAA-THA), largely due to limited femoral exposure and the absence of a standardized intraoperative landmark. This study aimed to investigate whether the ITL is an alternative bony landmark for femoral neck osteotomy during the DAA.

Three anatomical references, the Intertrochanteric line (ITL) height (ITL-H), ITL angle (ITL-A), and femoral saddle height (SH), were measured from 3D-CT models of 60 normal hip patients (30 males and 30 females) to simulate a cutting height of 10 mm above the LT. Twenty cadaveric hip specimens were then used to evaluate the accuracy of the proposed anatomical references.

The mean ITL-H, ITL-A, and SH were 23 ± 4 mm, 17.4° ± 3.5°, and 26 ± 4 mm, respectively. While ITL-H showed no sex difference (23 ± 3.4 mm vs 23.1 ± 4.1 mm, P = 0.96), significant differences existed for ITL-A (15.8° ± 3.4° vs 19.9° ± 1.4°, P = 0.001) and SH (27.2 ± 3.9 mm vs 23.9 ± 3 mm, P = 0.002). ITL-H was not correlated with age (P = 0.063), femoral length (P = 0.31), or femoral neck shaft angle (P = 0.41). Femoral neck osteotomy performed 23 mm above the ITL-H could yield 80% and 100% success rates for cutting heights of 10–15 mm and > 5 mm above the LT, respectively.

ITL-H serves as a reproducible anatomical landmark for femoral neck osteotomy during DAA-THA. An osteotomy level of approximately 23 mm above the ITL-H represents a safe lower margin to avoid excessive calcar bone resection. Nevertheless, individualized preliminary osteotomy based on preoperative templating remains necessary, with intraoperative adjustment according to patient-specific ITL-H.

Video Abstract

Video Abstract

The online version contains supplementary material available at 10.1186/s42836-025-00365-4.