Table II.
Mean intention-to-treat outcomes with 95% confidence intervals (CI) according to the mixed-effect analysis for within-group change from baseline to five years and between-group difference at five years. Performed according to prespecified analysis plan.
| Outcome | vE-PE (95% CI) | XLPE (95% CI) | vE-PE vs XLPE (95% CI) | p-value |
|---|---|---|---|---|
| Comparison between vE-PE and XLPE | ||||
| Total head penetration (mm) | 0.006 (-0.059 to 0.070) | 0.090 (0.029 to 0.151) | -0.084 (-0.173 to 0.005) | 0.064 |
| Head penetration rate | ||||
| 0 to 3 months (mm/yr) | 0.124 (-0.105 to 0.353) | 0.041 (-0.192 to 0.274) | 0.083 (-0.243 to 0.410) | 0.617 |
| 3 months to 1 year (mm/yr) | -0.047 (-0.141 to 0.046) | 0.005 (-0.087 to 0.097) | -0.053 (-0.184 to 0.078) | 0.429 |
| 1 to 2 years (mm/yr) | 0.027 (-0.045 to 0.100) | 0.060 (-0.011 to 0.132) | -0.033 (-0.135 to 0.069) | 0.525 |
| 2 to 5 years (mm/yr) | -0.006 (-0.032 to 0.020) | 0.005 (-0.020 to 0.030) | -0.011 (-0.047 to 0.025) | 0.554 |
| Secondary outcomes | ||||
| Cup migration (mm) | 0.293 (0.159 to 0.427) | 0.262 (0.133 to 0.391) | 0.031 (-0.155 to 0.217) | 0.743 |
| Comparison between 32 and 36 mm | 32 mm | 36 mm | 32 mm vs 36 mm | |
| Total head penetration (mm) | 0.038 (-0.031 to 0.107) | 0.058 (-0.001 to 0.116) | -0.020 (-0.110 to 0.071) | 0.671 |
| Head penetration rate | ||||
| 0 to 3 months | 0.008 (-0.229 to 0.245) | 0.139 (-0.086 to 0.364) | -0.132 (-0.458 to 0.195) | 0.430 |
| 3 months to 1 year (mm/yr) | -0.012 (-0.066 to 0.043) | -0.011 (-0.061 to 0.039) | -0.001 (-0.132 to 0.130) | 0.987 |
| 1 to 2 years (mm/yr) | 0.044 (-0.033 to 0.121) | 0.044 (-0.023 to 0.112) | -0.000 (-0.103 to 0.102) | 0.999 |
| 2 to 5 years (mm/yr) | 0.003 (-0.025 to 0.030) | -0.002 (-0.026 to 0.021) | 0.005 (-0.032 to 0.041) | 0.800 |
| Secondary outcomes | ||||
| Cup migration (mm) | 0.199 (0.059 to 0.340) | 0.338 (0.214 to 0.462) | -0.139 (-0.327 to 0.049) | 0.147 |
| Harris Hip Score | 32 (26 to 38) | 33 (27 to 40) | -1 (-8 to 6) | 0.704 |
| UCLA Activity Score | 0.8 (0.1 to 1.5) | 0.9 (-2.3 to 4.1) | -0.2 (-3.3 to 3.0) | 0.172 |
| EQ-5D Health State | 0.20 (0.15 to 0.26) | 0.07 (-0.20 to 0.34) | 0.13 (-0.13 to 0.40) | 0.752 |
| EQ-5D VAS | 17 (11 to 23) | 19 (-11 to 48) | -2 (-30 to 27) | 0.583 |
| SF-36 PCS | 2.7 (1.3 to 4.0) | -0.5 (-6.9 to 5.8) | 3.2 (-3.0 to 9.4) | 0.873 |
| SF-36 MCS | -1.4 (-2.8 to 0.0) | 3.7 (-2.8 to 10.1) | -5.1 (-11.3 to 1.2) | 0.321 |
No interaction was found between the two randomization factors for total head penetration (p = 0.318), steady-state wear (p = 0.285), or cup migration (p = 0.496) using mixed-effect analysis of variance.
Wald test.
CI, confidence interval; EQ-5D, EuroQol five-dimension questionnaire; MCS, mental component score; PCS, physical component score; SE, standard error of the mean SF-36, 36-Item Short-Form Health Survey questionnaire; UCLA, University of California, Los Angeles; VAS, visual analogue scale; vE-PE, vitamin E-doped cross-linked polyethylene liners; XLPE, cross-linked polyethylene liners