Patients With Modular-Neck Total Hip Arthroplasty: A Brief Five-Year Follow-Up Study
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Published on: August 4, 2022
Daisuke Inoue1, Camilo Restrepo2, Blake Nourie2
1Department of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University Hospital, Philadelphia, PA; Department of Orthopaedic Surgery, Graduate School of Medical Science, Kanazawa University, Kanazawa, Ishikawa, Japan.
Background:
We have previously reported the early clinical results of a modular-neck stem identifying an early 2-year revision rate of 13% due to neck-stem corrosion. This report updates our findings to a midterm mean follow-up of 5 years.
Methods:
This is a consecutive retrospective review of 186 modular-neck hips in 175 patients with a mean follow-up period was 60.1 ± 22.9 months (range 24-100). We reviewed clinical findings, routine radiographs, detailed imaging (metal artifact reduction software-magnetic resonance imaging, ultrasound), and serum ion levels of cobalt and chromium. We performed a survival analysis with the endpoint defined as revision total hip arthroplasty due to neck-stem corrosion.
Results:
We revised 41 hips (22.0%) for neck-stem corrosion. Clinical symptoms (groin pain ± local swelling) were consistently present in those that came for revision. Mean serum cobalt ion levels increased as time passed in all patients. Detailed image findings showed that larger fluid collections and local soft tissue masses were seen predominately in symptomatic patients. However, 14% of patients who underwent revision did not have positive magnetic resonance imaging or ultrasound findings. The survival rate was 87% (95% confidence interval 81-92) at 3 years postoperatively and 72% (95% confidence interval 64-80) at 7 years postoperatively.
Conclusion:
The revision rate for this modular-neck stem due to neck-stem corrosion at mid-term follow-up almost doubled in comparison to previous short-term results. It seems reasonable to consider clinical follow-up alone as symptoms, rather than blood testing for ion levels, seem to be the defining characteristic of failure.
Insights
Midterm follow-up of modular-neck hip stems revealed a nearly doubled revision rate for corrosion compared to early results. Clinical symptoms, not ion levels, appear to be the primary indicator of failure in these hip implants.
Area of Science:
- Orthopedic surgery
- Biomaterials science
- Medical device engineering
Background:
- Previous early results showed a 13% revision rate for modular-neck stem corrosion within 2 years.
- This study provides midterm follow-up data for these implants.
Purpose of the Study:
- To update clinical findings on modular-neck hip stems with a midterm mean follow-up of 5 years.
- To assess the incidence and characteristics of neck-stem corrosion and its impact on revision rates.
Main Methods:
- Retrospective review of 186 modular-neck hips in 175 patients.
- Mean follow-up of 60.1 months.
- Evaluation included clinical findings, radiographs, advanced imaging (MRI, ultrasound), and serum ion levels (cobalt, chromium).
Main Results:
- 41 hips (22.0%) required revision due to neck-stem corrosion.
- Symptomatic patients consistently presented with groin pain and/or swelling.
- Serum cobalt levels increased over time; imaging revealed fluid collections and soft tissue masses in symptomatic cases.
- Survival rate was 72% at 7 years, with 14% of revised patients lacking positive imaging findings.
Conclusions:
- The midterm revision rate for modular-neck stem corrosion nearly doubled compared to early findings.
- Clinical symptoms are more indicative of failure than serum ion level monitoring.
- This highlights potential long-term concerns with modular-neck hip implant designs regarding corrosion.
