# Fifteen-Year Follow-Up of Nanos Neck-Preserving Hip Arthroplasty: An Observational Retrospective Study

## TL;DR

This study shows that a bone-preserving hip replacement implant called Nanos has excellent long-term results, especially for younger patients, with minimal complications over 15 years.

## Contribution

The paper provides 15-year follow-up data on the Nanos neck-preserving hip implant, demonstrating its long-term durability and low revision rates.

## Key findings

- Both age groups showed significant improvement in hip function scores after 15 years.
- Radiographs confirmed stable implant fixation without osteolysis in all patients.
- The 15-year survivorship was 100% for patients under 50 and 96.6% for those 50 and older.

## Abstract

Introduction: Neck-preserving total hip arthroplasty (THA) has gained interest for conserving bone stock, restoring biomechanics, and facilitating revision surgery. The Nanos® femoral stem, designed for metaphyseal fixation while preserving the femoral neck, represents a reliable alternative to conventional THA. This study reports 15-year clinical and radiographic outcomes of the Nanos implant. Materials and Methods: We retrospectively reviewed 53 patients (35 males, 18 females) who underwent THA with the Nanos stem between 2008 and 2010. Patients were stratified into two groups according to age: <50 years (n = 24) and ≥50 years (n = 29). The primary diagnosis was osteoarthritis (95%), with a few cases of avascular necrosis or dysplasia. Clinical evaluation included the Harris Hip Score (HHS) and the Western Ontario and McMaster Universities Arthritis Index (WOMAC). Radiographic assessment focused on implant stability, osteolysis, and heterotopic ossifications. Kaplan–Meier survival analysis was performed with revision for any reason as the endpoint. Results: At 15 years of follow-up, both groups showed significant improvement (p < 0.001). In patients <50 years, HHS increased from 53.3 to 94.8 and WOMAC decreased from 79.9 to 3.5. In patients ≥50 years, HHS improved from 47.5 to 95.2 and WOMAC from 81.5 to 3.2. Radiographs confirmed stable fixation without osteolysis. Complications included two dislocations and one cortical perforation requiring revision. Kaplan–Meier survivorship at 15 years was 100% (<50) and 96.6% (≥50). Conclusions: The Nanos stem provided excellent long-term outcomes with low complication and revision rates. It should be considered one of several reliable short-stem options for younger, active patients, offering durable function while preserving bone stock.