Table 2.
Univariate analysis of risk factors for aseptic loosening after revision total knee arthroplasty
| Potential risk factor | Loosening (n = 17) | No loosening (n = 48) | OR | 95% CI | p |
|---|---|---|---|---|---|
| Age, years | 69.22 | 71.94 | 0.95 | 0.87–1.02 | 0.188 |
| Female sex | 8 | 39 | 4.88 | 1.47–16.13 | 0.009* |
| Bone defect severity | |||||
| Femur (loosening, n = 12) | |||||
| I | 3 | 28 | 0.29 | 0.07–1.22 | 0.075 |
| IIa | 9 | 25 | |||
| Tibia (loosening, n = 12) | |||||
| I | 1 | 26 | 0.09 | 0.01–0.78 | 0.005* |
| IIa | 11 | 27 | |||
| Prosthesis before revision | |||||
| Primary TKA | 14 | 43 | 2.28 | 0.86–6.01 | 0.094 |
| UKA | 0 | 3 | |||
| Revision TKA | 3 | 1 | |||
| None | 0 | 1 | |||
| Stem length, mm | |||||
| Femur | 100 (75–200) | 100 (25–200) | 0.990 | 0.96–1.01 | 0.990 |
| Tibia | 75 (25–150) | 100 (25–200) | 0.98 | 0.96–1.01 | 0.157 |
| Radiographic finding | |||||
| Alignment, ° | 5.0 (2.1–6.2) | 5.8 (5.2–7.4) | 0.62 | 0.43–0.87 | 0.006* |
| Femur (loosening, n = 12) | |||||
| CFR0.85 | 8.33 (1/12) | 52.83 (28/53) | 0.08 | 0.01–0.67 | 0.020* |
| CFR0.7 > 2 cm | 16.67 (2/12) | 75.47 (40/53) | 0.07 | 0.01–0.33 | 0.001* |
| CFR0.7 > 4 cm | 8.33 (1/12) | 45.28 (24/53) | 0.11 | 0.01–0.91 | 0.041* |
| CFRmax | 0.69 (0.54–1.00) | 0.82 (0.47–1.00) | 0.94 | 0.89–0.98 | 0.010* |
| CFR0.85 length | 0.0 (0.0–4.7) | 1.2 (0.0–7.8) | 0.37 | 0.13–0.97 | 0.045* |
| CFR0.7 length | 0.0 (0.0–7.5) | 3.5 (0.0–10.3) | 0.50 | 0.31–0.79 | 0.003* |
| Tibia (loosening, n = 12) | |||||
| CFR0.85 | 8.33 (1/12) | 47.17 (25/53) | 0.10 | 0.01–0.84 | 0.034* |
| CFR0.7 > 2 cm | 41.67 (5/12) | 77.36 (41/53) | 0.21 | 0.05–0.77 | 0.020* |
| CFR0.7 > 4 cm | 16.67 (2/12) | 58.49 (31/53) | 0.14 | 0.02–0.71 | 0.018* |
| CFRmax | 0.77 (0.60–0.88) | 0.82 (0.53–1.00) | 0.96 | 0.91–1.01 | 0.159* |
| CFR0.85 length | 0.0 (0.0–1.7) | 0.0 (0.0–12.8) | 0.40 | 0.15–1.07 | 0.069* |
| CFR0.7 length | 1.6 (0.0–4.3) | 4.5 (0.0–4.7) | 0.70 | 0.52–0.94 | 0.019* |
Data are shown as frequency (number/total) or median (interquartile range) unless otherwise specified. Bone defect severity was assessed using the Anderson Orthopaedic Research Institute classification. Alignment indicates the femoral-tibial angle. CFR was calculated as the ratio between the stem width and the medullary canal width. CFRx stands for CFR > x. CFRx > y indicates the stem length > y for CFR larger than x. CFRx length indicates the stem length for which CFR > x. CFRmax indicates the maximum CFR over the entire length of the stem. CI, confidence interval; CFR, canal filling ratio; OR, odds ratio; TKA, total knee arthroplasty; UKA, uni-compartment knee arthroplasty; *: p < 0.05