Table 2.
RSA double examination measurements at 1-year follow-up, specified for the 6 different implant types
| Axis | Translations (mm) | Rotations (°) | MTPM (mm) | ||||||
|---|---|---|---|---|---|---|---|---|---|
| x | y | z | TT a | x | y | z | TR b | ||
| Oxford UKA (cementless) (n = 391) | |||||||||
| Mean difference | 0.00 | 0.00 | –0.00 | 0.01 | –0.03 | –0.01 | 0.02 | 0.01 | 0.01 |
| SD difference | 0.04 | 0.03 | 0.16 | 0.12 | 0.22 | 0.17 | 0.17 | 0.19 | 0.13 |
| CR c | 0.08 | 0.07 | 0.31 | 0.23 | 0.42 | 0.33 | 0.33 | 0.37 | 0.26 |
| NexGen Trabecular Metal CR Monoblock (cementless) (n = 244) | |||||||||
| Mean difference | –0.00 | 0.00 | 0.00 | –0.03 | 0.02 | –0.05 | –0.01 | –0.08 | –0.07 |
| SD difference | 0.08 | 0.06 | 0.31 | 0.20 | 0.37 | 0.30 | 0.14 | 0.30 | 0.22 |
| CR c | 0.16 | 0.13 | 0.62 | 0.39 | 0.72 | 0.58 | 0.28 | 0.59 | 0.44 |
| NexGen Stemmed Precoat (cemented) (n =1 65) | |||||||||
| Mean difference | –0.00 | –0.00 | –0.02 | 0.01 | –0.05 | –0.05 | 0.00 | –0.02 | –0.02 |
| SD difference | 0.08 | 0.09 | 0.19 | 0.13 | 0.31 | 0.53 | 0.12 | 0.41 | 0.28 |
| CR c | 0.16 | 0.17 | 0.38 | 0.26 | 0.60 | 1.03 | 0.24 | 0.79 | 0.54 |
| Oxford UKA (cemented) (n = 113) | |||||||||
| Mean difference | –0.01 | –0.01 | 0.00 | –0.01 | 0.02 | –0.00 | 0.02 | –0.01 | –0.01 |
| SD difference | 0.05 | 0.03 | 0.11 | 0.07 | 0.21 | 0.19 | 0.16 | 0.16 | 0.09 |
| CR c | 0.10 | 0.07 | 0.21 | 0.14 | 0.40 | 0.36 | 0.32 | 0.31 | 0.18 |
| Triathlon Primary TKA (cemented) (n = 46) | |||||||||
| Mean difference | –0.01 | –0.01 | 0.01 | –0.01 | 0.01 | –0.04 | 0.02 | 0.01 | –0.00 |
| SD difference | 0.05 | 0.04 | 0.14 | 0.10 | 0.26 | 0.28 | 0.09 | 0.24 | 0.19 |
| CR c | 0.10 | 0.08 | 0.27 | 0.20 | 0.52 | 0.54 | 0.18 | 0.48 | 0.37 |
| Triathlon Primary TKA (cementless) (n = 16) | |||||||||
| Mean difference | –0.00 | –0.03 | –0.03 | –0.00 | 0.08 | 0.05 | 0.01 | –0.05 | –0.02 |
| SD difference | 0.04 | 0.05 | 0.05 | 0.04 | 0.25 | 0.24 | 0.09 | 0.20 | 0.11 |
| CR c | 0.08 | 0.09 | 0.10 | 0.08 | 0.49 | 0.47 | 0.19 | 0.40 | 0.21 |
| Vanguard Interlok CR with locking bar (cemented) (n = 15) | |||||||||
| Mean difference | –0.00 | 0.01 | –0.01 | –0.01 | –0.01 | 0.03 | 0.03 | –0.06 | –0.05 |
| SD difference | 0.05 | 0.04 | 0.10 | 0.07 | 0.14 | 0.31 | 0.09 | 0.22 | 0.18 |
| CR c | 0.10 | 0.08 | 0.20 | 0.13 | 0.28 | 0.61 | 0.18 | 0.43 | 0.35 |
RSA: radiostereometric analysis, MTPM: maximum total point motion, TKA: total knee arthroplasty, UKA: unicompartmental knee arthroplasty, SD: standard deviation.
The mean difference represents the systematic measurement error. The SD difference represents the random variation (precision).
a
Total translation (TT) was calculated using the Pythagorean theorem (TT= √(x2+y2+z2)).
b
Total rotation (TR) was calculated using the Pythagorean theorem (TR= √(x2+y2+z2)).
c
CR = coefficient of repeatability = 1.96. * SD difference represents the expected clinical precision.