Unexpected High Rates of Corrosion Related Revisions: Short-Term Results of the Modular Neck Rejuvenate Stem

Background:

The Rejuvenate modular neck stem (Stryker, Mahwah, NJ) was recently recalled due to corrosion at the neck-stem junction. The purpose of this study was to investigate the rate of corrosion related failures and survivorship of this implant, and analyze the correlation between the implant and patient factors with serum metal ion levels.

Material and Methods:

Between June 2009 and July 2012, 123 Rejuvenate stems (97 modular and 26 non-modular) THAs were implanted in 104 patients by a single surgeon via a modified anterolateral approach. Serum Cobalt (Co) and Chromium (Cr) levels (microgram per liter [μg/L]) were obtained in all patients. In cases of elevated serum metal ion levels or symptomatic hip, patients underwent magnetic resonance imaging (MRI) for assessment of osteolysis or adverse local tissue reactions (ALTR). Correlation between implant factors (implant size, head size, head length, offset), patient factors (age, gender, BMI) with serum metal ion levels and revisions were analyzed using logistic regression models.

Results:

The mean follow-up was 2.7 ± 0.6 years. The mean Co and Cr levels were 5.4 ± 5.7 μg/L (0.2–31) and 2.1 ± 1.5 μg/L (0.1–4.3), respectively. The differences between the Co and Cr levels in the two groups were statistically significant. 49% of THAs in the modular group had elevated metal ion levels (> 4.0 μg/L). There was a significant correlation between higher metal ion levels, younger age, and higher offset (p < 0.05). Presence of pain and high cobalt levels were significant predictors for revision surgery. The rate of revision at the time of this study was 26%, the majority were in the 2^nd year after surgery. The Kaplan-Meier survivorship was 75% at the time of this study.

Discussion and Conclusions:

The short-term high rate of corrosion related revision with Rejuvenate modular neck stems is extremely alarming. We anticipate more revisions in the near future.

Level of Evidence: Level III, Therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.