The beneficial effect of hydroxyapatite lasts: a randomized radiostereometric trial comparing hydroxyapatite-coated, uncoated, and cemented tibial components for up to 16 years

Abstract

Background and purpose: In contrast to early migration, the long-term migration of hydroxyapatite- (HA-) coated tibial components in TKA has been scantily reported. This randomized controlled trial investigated the long-term migration measured by radiostereometric analysis (RSA) of HA-coated, uncoated, and cemented tibial components in TKA.

Patients and methods: 68 knees were randomized to HA-coated (n = 24), uncoated (n = 20), and cemented (n = 24) components. All knees were prospectively followed for 11-16 years, or until death or revision. RSA was used to evaluate migration at yearly intervals. Clinical and radiographic evaluation was according to the Knee Society system. A generalized linear mixed model (GLMM, adjusted for age, sex, diagnosis, revisions, and BMI) was used to take into account the repeated-measurement design.

Results: The present study involved 742 RSA analyses. The mean migration at 10 years was 1.66 mm for HA, 2.25 mm for uncoated and 0.79 mm for the cemented group (p < 0.001). The reduction of migration by HA as compared to uncoated components was most pronounced for subsidence and external rotation. 3 tibial components were revised for aseptic loosening (2 uncoated and 1 cemented), 3 for septic loosening (2 uncoated and 1 cemented), and 1 for instability (HA-coated). 2 of these cases were revised for secondary loosening after a period of stability: 1 case of osteolysis and 1 case of late infection. There were no statistically significant differences between the fixation groups regarding clinical or radiographic scores.

Interpretation: HA reduces migration of uncemented tibial components. This beneficial effect lasts for more than 10 years. Cemented components showed the lowest migration. Longitudinal follow-up of TKA with RSA allows early detection of secondary loosening.

Figure 1.

CONSORT flow chart.

Figure 2.

Migration in maximum total point motion (MTPM) (mean and standard deviation) according to the duration of follow-up in the hydroxyapatite (HA) group (green boxes), the uncoated group (red boxes), and the cemented group (blue boxes). The direct postoperative RSA radiograph is the reference. The groups differed significantly in migration (p < 0.001, GLMM). Missing values at 4-year follow-up were estimated as the mean of the 3-year and 5-year follow-up.

Figure 3.

Migration from 1 to 10 years in maximum total point motion (MTPM) (mean and standard deviation) according to the duration of follow-up in the hydroxyapatite (HA) group (green boxes), the uncoated group (red boxes), and the cemented group (blue boxes). The 1-year postoperative RSA radiograph is the reference. The groups differed significantly in migration (p < 0.001, GLMM). Missing values at 4-year follow-up were estimated as the mean of the 3-year and 5-year follow-up.

Figure 4.

Migration from 1 to 16 years in maximum total point motion (MTPM) of individual cases with 10 years of RSA follow-up or more according to the duration of follow-up in the hydroxyapatite (HA) group (upper row), the uncoated group (middle row), and cemented group (lower row). The 1-year postoperative RSA radiograph was the reference.

Figure 5.

Individual migration patterns of the liner exchange and revised cases (with the postoperative radiograph as reference). For the insert exchanges, the letters at the top indicate the time of insert exchange with blue C for cemented tibial components, green H for HA-coated tibial components, and red U for uncoated tibial components. The tibial components remained securely fixed after the exchange of insert.