Background: Ultraporous highly porous-coated acetabulum components

were introduced to further enhance osteointegration of uncemented cups

in total hip arthroplasty (THA). Implant survival data on these new devices is

scarce, however. The aim of our study was to assess survivorship of ultraporous

Tritanium cups (Stryker, Mahwah, NJ, USA) in a population-based register study.

Methods: Data on 6,080 primary THAs with a Tritanium cup and 25,670 THAs

with a conventional uncemented cup (reference group) were collected from the

Finnish Arthroplasty Register from 1.1.2009 to 31.12.2017. Kaplan-Meier survival

estimates with 95% confidence intervals (CI) were calculated. The endpoint was

revision for any reason or for aseptic loosening of the cup. Revision was defined

as a change or removal of at least one component. Revision risks were assessed

using Cox multiple regression model. The variables assessed in the Cox model

were age group, gender, diagnosis, femoral head size, operated side, operation

year, and fixation of the stem. Because the proportional hazards assumption of

the Cox model was not fulfilled the follow-up time was divided into three time

periods: 0-2years, 2-4 years, and over 4 years.

Results: The 7-year Kaplan-Meier survivorship of the Tritanium group (94.0%

(95% CI 92.9-94.9)) was inferior compared to that of the reference group (95.6%

(CI 95.3-95.9)) for any reason of revision. In the Cox regression analysis the

Tritanium group had an increased risk of revision for any reason compared

to the reference group for the time period 4 years and over (HR 3.12, (95% CI

1.82-5.25, p<0.001)). The Tritanium group had an increased risk of revision for

aseptic loosening of the cup compared to the reference group both for the time

period from 0 to 2 years (HR 3.80, (95% CI 1.76-8.24, p<0.001)), and for the time

period from 2 to 4 years (HR 11.2, (95% CI 3.28-38.0, p<0.001)).

Conclusions: The use of the ultraporous-coated Tritanium cup for primary THA

does not provide an advantage over conventional uncemented cups.

Level of evidence: Therapeutic level III