# Evaluating the Reliability of the Lesser Trochanter as a Landmark for Limb Length Discrepancy in Direct Anterior Approach Total Hip Arthroplasty

## TL;DR

This study assesses how reliable the lesser trochanter is as a landmark for correcting limb length differences during hip replacement surgery, finding it effective when combined with imaging techniques.

## Contribution

The study evaluates the lesser trochanter's reliability as a surgical landmark for limb length correction in THA, specifically in an Indian patient population.

## Key findings

- Using the lesser trochanter with fluoroscopy reduced limb length discrepancy from 1.5 cm preoperatively to 0.2 cm postoperatively.
- Patients with postoperative limb length discrepancy ≤0.5 cm showed significantly better functional outcomes and higher satisfaction.
- Standardized protocols combining lesser trochanter measurements and fluoroscopic validation improved surgical accuracy and patient recovery.

## Abstract

Background and aim

Limb length discrepancy (LLD) is a common complication following total hip arthroplasty (THA), significantly impacting functional outcomes, patient satisfaction, and quality of life. The direct anterior approach (DAA) for THA has gained popularity due to its potential for minimizing LLD through precise intraoperative control. Despite advancements, achieving limb length equality remains challenging, particularly in the Indian patient population, where anatomical variations may affect surgical outcomes. The lesser trochanter (LT) is frequently utilized as a landmark for intraoperative LLD assessment. However, the reliability of the LT in DAA-THA remains debated. This study aimed to evaluate the accuracy and consistency of using the LT as an intraoperative reference for LLD correction in DAA-THA.

Methods

A retrospective cohort analysis was conducted on 130 patients who underwent DAA-THA at a high-volume tertiary care center between January 2023 and December 2023. Patients were selected based on the inclusion criteria of age >18 years, availability of preoperative and postoperative radiographs, and adequate fluoroscopic imaging during surgery. The LT was used as the primary landmark for limb length restoration. Intraoperative fluoroscopy and standardized leg positioning systems were employed to ensure accurate component placement. Preoperative and postoperative LLD were measured using standardized radiographic techniques, and functional outcomes were assessed through the Harris Hip Score (HHS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Forgotten Joint Score (FJS). Statistical analysis was performed to determine the association between LLD correction and functional recovery.

Results

The cohort had a mean age of 57.1 years, with 70% males and 30% females. The mean BMI was 27.1 ± 4.4 kg/m2. Primary indications were avascular necrosis (73.8%), femoral neck fractures (19.2%), rheumatoid arthritis (6.2%), and primary osteoarthritis (0.8%). The mean preoperative LLD of 1.5 cm was reduced to 0.2 cm postoperatively, with only two patients having LLD >1 cm.

Functional outcomes improved significantly postoperatively, with HHS increasing from 40.7 ± 5.7 preoperatively to 95.1 ± 4.4 at 12 months (p < 0.001). The WOMAC score decreased from 60.7 ± 5.8 to 10.1 ± 6.7 over the same period (p < 0.001). The FJS improved from 19.9 ± 6.45 preoperatively to 85.5 ± 9.3 postoperatively, indicating high patient satisfaction. Patients with postoperative LLD ≤0.5 cm had significantly higher HHS and lower WOMAC scores compared to those with residual LLD >1 cm, highlighting the importance of precise LLD correction for optimal functional recovery.

Conclusion

The LT serves as a reliable anatomical landmark for correcting LLD during DAA-THA, particularly when combined with intraoperative fluoroscopy and standardized positioning systems. This approach resulted in favorable postoperative functional outcomes and high patient satisfaction. Implementing standardized protocols that include LT-based measurements and fluoroscopic validation can significantly reduce LLD, enhancing clinical outcomes in THA. Further research is warranted to validate these findings in larger, multicenter cohorts.