Background: Several acetabular components utilizing novel ultraporous metal substrates have been introduced over the past decade. Collectively by design, they have a lower modulus of elasticity to reduce stress shielding, a higher coefficient of friction to enhance interference fit, and ultraporous surfaces to enhance osseointegration. However, little literature exists regarding their clinical performance.
Methods: This study compared the clinical and radiographic results of 109 hips in 95 patients using a Tritanium primary cup (Stryker, Mahwah, NJ) to an age, body mass index, and gender-matched cohort of 100 patients that received a contemporary cup (Stryker Trident PSL HA).
Results: At an average 4.24 + 1.49 years, implant survivorship of the Tritanium primary cup was 98.2%, with 2 cups revised for failure of osseointegration. One-year radiographs revealed radiolucent and radiosclerotic lines in 2 or more DeLee zones in 30.3% of cups and 3 zone involvement in 8.2%. These proportions increased (40.0% and 17.1%, respectively) at minimum 5-year follow-up. A comparison of 1 year and last follow-up radiographs revealed progression in 13.8%. Tritanium primary components with radiolucency in 2 or more zones exhibited significantly lower HHS at 2 years compared to all Trident peripheral self-locking (PSL) components (P < .0001) and Tritanium primary components with 1 zone or no radiolucency (P = .026). Scanning electron microscopy of a retrieved cup revealed local inflammatory reaction and no evidence of osseointegration.
Conclusion: Despite adequate implant survivorship, over one third of Tritanium primary cups had 2 or more zone radiolucency at minimum 5-year follow-up with associated lower Harris hip scores.
Keywords: Trabecular Metal; acetabular fixation; osseointegration failure; primary hip arthroplasty; ultraporous metal substrates.
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