Uncemented Metal-Backed Tantalum Patellar Components in Total Knee Arthroplasty Have a High Fracture Rate at Midterm Follow-Up.

BACKGROUND

There is interest in uncemented total knee arthroplasty due to the hope for long-term biologic fixation, but limited data are available regarding uncemented tantalum patellar components. The purpose of this study was to evaluate the radiographic outcomes of uncemented tantalum patellar implants at midterm follow-up.

METHODS

We retrospectively reviewed a consecutive series of 30 knees in 29 patients who underwent cementless total knee arthroplasty with an uncemented metal-backed tantalum patella between September 2006 and April 2009. Patients were required to have a minimum radiographic follow-up of 2 years. Anteroposterior and lateral radiographs of the knee were evaluated for signs of implant fracture or gross loosening. Clinical follow-up was obtained by reviewing each patient's most recent orthopedic record.

RESULTS

Thirty knees in 29 patients met inclusion criteria. The mean age of the cohort was 59.1 years with a mean body mass index of 31.9 kg/m2. Mean postoperative radiographic follow-up time was 5.5 years. Six fractures of the patellar component were noted. This represented a fracture rate of 20% among the entire cohort and 35% among the 17 knees with visible patellae on anteroposterior radiograph. All fractures had a transverse pattern. No gross patellar component loosening was noted. Among patients with component fractures, 2 required revisions for instability and 1 revision was for infection.

CONCLUSION

Our results suggest a minimum 20% rate of component fracture at midterm follow-up. Although many of these patellar component fractures were asymptomatic, they have the potential to impact revision rates in the longer term.