Cox regression model identifying risk factors of revision after 5 years of primary total knee and unicompartmental replacement: hospital data
| Risk factors (reference category) | Patients undergoing KR (n=188 509) | ||
| Crude analysis HR (95% CI); p value | Adjusted analysis HR (95% CI); p value | Adjusted analysis competing risks HR (95% CI); p value | |
| Year of primary KR (2008) | |||
| 2009 | 0.91 (0.78 to 1.06); p=0.23 | 0.90 (0.77 to 1.05); p=0.20 | 0.88 (0.75 to 1.03); p=0.10 |
| 2010 | 0.82 (0.68 to 0.98); p=0.03 | 0.82 (0.69 to 0.99); p=0.037 | 0.77 (0.64 to 0.92); p=0.004 |
| 2011 | 0.83 (0.64 to 1.07); p=0.15 | 0.83 (0.65 to 1.07); p=0.15 | 0.69 (0.54 to 0.87); p=0.002 |
| Age at primary KR (continuous variable) | 0.94 (0.9–0.9); p<0.01 | 0.95 (0.95 to 0.96); p<0.01 | 0.95 (0.94 to 0.95); p<0.01 |
| Sex (women) | |||
| Men | 1.08 (1.0–1.2); p=0.23 | 1.13 (0.99 to 1.28); p=0.074 | 1.09 (0.95 to 1.24); p=0.21 |
| Body mass index (normal) | |||
| Underweight | 1.96 (0.96 to 4.01); p=0.07 | 2.31 (1.13 to 4.73); p=0.022 | 2.22 (1.08 to 4.56); p=0.029 |
| Overweight | 1.04 (0.85 to 1.28); p=0.68 | 0.91 (0.74 to 1.11); p=0.35 | 0.92 (0.75 to 1.13); p=0.45 |
| Obese class I (moderately obese) | 1.02 (0.83 to 1.25); p=0.87 | 0.74 (0.60 to 0.91); p=0.004 | 0.75 (0.61 to 0.92); p=0.007 |
| Obese class II and higher | 1.20 (0.96 to 1.49); p=0.10 | 0.70 (0.56 to 0.88); p=0.002 | 0.71 (0.56 to 0.88); p=0.002 |
| IMD (quintiles), at primary KR (less deprived 20%) | |||
| Less deprived 20%–40% | 0.87 (0.72 to 1.05); p=0.14 | 0.84 (0.70 to 1.01); p=0.06 | 0.84 (0.70 to 1.01); p=0.058 |
| Less deprived 40%–60% | 0.91 (0.75 to 1.10); p=0.32 | 0.78 (0.64 to 0.94); p=0.01 | 0.77 (0.64 to 0.93); p=0.008 |
| More deprived 20%–40% | 0.94 (0.78 to 1.14); p=0.55 | 0.79 (0.65 to 0.96); p=0.016 | 0.78 (0.64 to 0.94); p=0.01 |
| Most deprived 20% | 0.87 (0.71 to 1.06); p=0.17 | 0.71 (0.58 to 0.87); p=0.001 | 0.70 (0.58 to 0.86); p=0.001 |
| Ethnicity (white) | |||
| Non-white | 0.68 (0.5 to 0.9); p=0.01 | 0.58 (0.43 to 0.78); p<0.01 | 0.59 (0.44 to 0.80); p=0.001 |
| OKS, baseline score (0–10 points) (0=poor, 48=good) | |||
| (11–14 points) | 0.82 (0.7 to 1.0); p=0.03 | 0.85 (0.70 to 1.02); p=0.073 | 0.85 (0.71 to 1.02); p=0.087 |
| (15–19 points) | 0.69 (0.6 to 0.8); p<0.01 | 0.71 (0.60 to 0.85); p<0.01 | 0.73 (0.61 to 0.87); p<0.01 |
| (20–24 points) | 0.51 (0.4 to 0.6); p<0.01 | 0.55 (0.44 to 0.68); p<0.01 | 0.56 (0.45 to 0.69); p<0.01 |
| (25–48 points) | 0.37 (0.3 to 0.5); p<0.01 | 0.42 (0.33 to 0.53); p<0.01 | 0.43 (0.34 to 0.54); p<0.01 |
| OKS, 6- month score (0–10 points) (0=poor, 48=good) | |||
| (11–14 points) | 0.72 (0.61 to 0.86); p<0.01 | 0.81 (0.67 to 0.96); p=0.016 | 0.81 (0.68 to 0.97); p=0.019 |
| (15–19 points) | 0.53 (0.44 to 0.63); p<0.01 | 0.59 (0.49 to 0.72): p<0.01 | 0.60 (0.50 to 0.72); p<0.01 |
| (20–24 points) | 0.43 (0.35 to 0.52); p<0.01 | 0.48 (0.39 to 0.59); p<0.01 | 0.48 (0.39 to 0.59); p<0.01 |
| (25–48 points) | 0.29 (0.23 to 0.36); p<0.01 | 0.33 (0.26 to 0.41); p<0.01 | 0.33 (0.26 to 0.42); p<0.01 |
| EQ-5D-3L Anxiety Depression, 3 months or closer to primary KR (I am not anxious or depressed) | |||
| I am moderately anxious or depressed | 1.02 (0.9 to 1.2); p=0.78 | 0.73 (0.63 to 0.83); p<0.01 | 0.72 (0.63 to 0.82); p<0.01 |
| I am extremely anxious or depressed | 1.26 (0.9 to 1.7); p=0.14 | 0.67 (0.49 to 0.91); p=0.01 | 0.65 (0.48 to 0.89); p=0.007 |
HR represents number of times to have a revision after 5 years compared with the reference group. A value >1 indicates that the group has higher risk for revision.
Variables included in the final regression model are those with at least one category with a p value <0.05 for a single imputed dataset in a backward selection.
Body mass index and sex were force-entered into all models.
Bold figures represent results with p values <0.05 in the final regression model
EQ-5D-3L, EuroQol five domains; IMD, Index of Multiple Deprivation; KR, total and unicompartmental knee replacement; OKS, Oxford Knee Score.