Unexpected varus deformity and concomitant metal ion release and MRI findings of modular-neck hip stems : descriptive RSA study in 75 hips with 8 years’ follow-up
Kiernan, Sverrir LU
; Kaptein, Bart
; Flivik, Carl
; Sundberg, Martin
LU
and Flivik, Gunnar
LU
(2021)
In Acta Orthopaedica
92(1).
p.67-73
- Abstract
Background and purpose — Modular-neck hip stems have been identified with corrosion-related problems from the neck–stem junction. We report an ongoing varus deformity of modular-neck hip stems with simultaneous metal ion release observed during a study comparing the migration of modular vs. standard hip stems. Patients and methods — We followed 50 patients with modular and 25 with standard neck stems using radiostereometry (RSA). At 5-year follow-up, we noted a compromised integrity of the modular stem with varus deformity in the neck–stem interface. Changes in head–tip distance as well as whole-blood ion concentration and MRI findings were analyzed. The modular stems were followed further up to 8 years. Results — The head–tip distance... (More)
Background and purpose — Modular-neck hip stems have been identified with corrosion-related problems from the neck–stem junction. We report an ongoing varus deformity of modular-neck hip stems with simultaneous metal ion release observed during a study comparing the migration of modular vs. standard hip stems. Patients and methods — We followed 50 patients with modular and 25 with standard neck stems using radiostereometry (RSA). At 5-year follow-up, we noted a compromised integrity of the modular stem with varus deformity in the neck–stem interface. Changes in head–tip distance as well as whole-blood ion concentration and MRI findings were analyzed. The modular stems were followed further up to 8 years. Results — The head–tip distance decreased continuously by 0.15 mm per year resulting in 1.2 (95% CI 1.0–1.4) mm at 8 years for modular stems, while for the standard stems at 5 years, the decrease was 0.09 (CI 0.0–0.2) mm or 0.02 mm/year. For the modular stems, the reduction in head–tip distance correlated to the increase in whole-blood cobalt concentration at 8 years but not to the MRI grading of tissue reactions. At 5 years, cobalt levels were 4.9 µg/L for modular stems and at 8 years 4.8 µg/L, whereas for standard stems this was 1.0 µg/L. After 8 years, 9 of 72 stems had been revised for different reasons, but only 1 with obvious adverse local tissue reaction (ALTR). Interpretation — We present a surprisingly large progressive deformation at the modular neck–stem junction, but so far without a definite clinical problem. Even the femoral head seems to show slight compression onto the taper over time. A high rate of revisions for the modular type of this stem has raised general concerns, and it has been recalled from the market.
(Less)
- author
- Kiernan, Sverrir
LU
; Kaptein, Bart
; Flivik, Carl
; Sundberg, Martin
LU
and Flivik, Gunnar
LU
- organization
- publishing date
- 2021
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Acta Orthopaedica
- volume
- 92
- issue
- 1
- pages
- 67 - 73
- publisher
- Taylor & Francis
- external identifiers
-
- pmid:33297800
- scopus:85097427907
- ISSN
- 1745-3674
- DOI
- 10.1080/17453674.2020.1853387
- language
- English
- LU publication?
- yes
- id
- c52db94b-0883-4ff2-a80b-26eee0d06a96
- date added to LUP
- 2020-12-22 12:47:16
- date last changed
- 2025-01-24 03:16:15
@article{c52db94b-0883-4ff2-a80b-26eee0d06a96,
abstract = {{<p>Background and purpose — Modular-neck hip stems have been identified with corrosion-related problems from the neck–stem junction. We report an ongoing varus deformity of modular-neck hip stems with simultaneous metal ion release observed during a study comparing the migration of modular vs. standard hip stems. Patients and methods — We followed 50 patients with modular and 25 with standard neck stems using radiostereometry (RSA). At 5-year follow-up, we noted a compromised integrity of the modular stem with varus deformity in the neck–stem interface. Changes in head–tip distance as well as whole-blood ion concentration and MRI findings were analyzed. The modular stems were followed further up to 8 years. Results — The head–tip distance decreased continuously by 0.15 mm per year resulting in 1.2 (95% CI 1.0–1.4) mm at 8 years for modular stems, while for the standard stems at 5 years, the decrease was 0.09 (CI 0.0–0.2) mm or 0.02 mm/year. For the modular stems, the reduction in head–tip distance correlated to the increase in whole-blood cobalt concentration at 8 years but not to the MRI grading of tissue reactions. At 5 years, cobalt levels were 4.9 µg/L for modular stems and at 8 years 4.8 µg/L, whereas for standard stems this was 1.0 µg/L. After 8 years, 9 of 72 stems had been revised for different reasons, but only 1 with obvious adverse local tissue reaction (ALTR). Interpretation — We present a surprisingly large progressive deformation at the modular neck–stem junction, but so far without a definite clinical problem. Even the femoral head seems to show slight compression onto the taper over time. A high rate of revisions for the modular type of this stem has raised general concerns, and it has been recalled from the market.</p>}},
author = {{Kiernan, Sverrir and Kaptein, Bart and Flivik, Carl and Sundberg, Martin and Flivik, Gunnar}},
issn = {{1745-3674}},
language = {{eng}},
number = {{1}},
pages = {{67--73}},
publisher = {{Taylor & Francis}},
series = {{Acta Orthopaedica}},
title = {{Unexpected varus deformity and concomitant metal ion release and MRI findings of modular-neck hip stems : descriptive RSA study in 75 hips with 8 years’ follow-up}},
url = {{http://dx.doi.org/10.1080/17453674.2020.1853387}},
doi = {{10.1080/17453674.2020.1853387}},
volume = {{92}},
year = {{2021}},
}