Migration of a cemented fixed-bearing, polished titanium tibial baseplate (Genesis II) at ten years

Aims

The purpose of the present study was to examine the long-term fixation of a cemented fixed-bearing polished titanium tibial baseplate (Genesis ll).

Patients and Methods

Patients enrolled in a previous two-year prospective trial (n = 35) were recalled at ten years. Available patients (n = 15) underwent radiostereometric analysis (RSA) imaging in a supine position using a conventional RSA protocol. Migration of the tibial component in all planes was compared between initial and ten-year follow-up. Outcome scores including the Knee Society Score, Western Ontario and McMaster Universities Arthritis Index, 12-item Short Form Health Survey, Forgotten Joint Score, and University of California, Los Angeles Activity Score were recorded.

Results

At ten years, the mean migration of the tibial component was less than 0.1 mm and 0.1° in all planes relative to the post-operative RSA exam. Maximum total point movement increased with time (p = 0.002) from 0.23 mm (sd 0.18) at six weeks to 0.42 mm (sd 0.20) at ten years.

Conclusion

The low level of tibial baseplate migration found in the present study correlates to the low rate of revision for this implant as reported in individual studies and in joint replacement registries.

Take home message: Overall, the implant was found to be well fixed at ten years, supporting its continued clinical use and the predictive power of RSA for determining long-term fixation of implants.