The demographic characteristics of participants
120 participants were chosen, and related demographic characteristics are shown in Table 1. As described before, 56 participants with valgus and severe varus (varus deviation ≥ 15°) knee were determined as challenging TKA, while the other was defined as regular TKA (n = 64). Due to the loss of follow-up, 99 participants were finally taken into the analysis (Fig. 1). No significant difference was found in those four groups (RCT, RCRAT, CCT, CCRAT) in the basic characteristics.
Table 1
The demographic characteristics of the participants
| | RCT | CCT | RCRAT | CCRAT |
Basic Characteristics | Age (years) | 67.8 ± 7.3 | 69.4 ± 8.9 | 63.5 ± 6.8 | 66.1 ± 6.6 |
Height (cm) | 156.9 ± 6.2 | 159.0 ± 7.0 | 160.1 ± 7.1 | 156.0 ± 7.3 |
Body mass(kg) | 67.4 ± 10.2 | 66.2 ± 10.9 | 72.4 ± 10.4 | 65.0 ± 12.3 |
BMI (kg/m2) | 27.4 ± 4.2 | 26.2 ± 4.0 | 27.9 ± 3.3 | 26.5 ± 3.3 |
Hypertension (%) | 37.0% | 43.5% | 34.5% | 34.8% |
Diabetes (%) | 29.6% | 39.1% | 30.8% | 47.8% |
Specialized Characteristics | KL Grade 3 (%) | 18.5% | 13.0% | 23.1% | 8.7% |
KL Grade 4 (%) | 71.5% | 87.9% | 76.9% | 91.3% |
MA | 171.2 ± 3.1 | 172.3 ± 12.8 | 173.2 ± 3.7 | 174.2 ± 14.3 |
VAS | 4.0 ± 0.9 | 4.1 ± 1.0 | 3.9 ± 0.9 | 3.7 ± 1.0 |
OKS | 40.8 ± 7.0 | 40.4 ± 6.5 | 38.9 ± 6.6 | 40.6 ± 8.3 |
HSS | 30.4 ± 7.4 | 32.5 ± 6.4 | 28.3 ± 3.0 | 31.1 ± 6.3 |
CRAT improved spatial accuracy of prosthesis
The spatial accuracy of the prosthesis was described as shown in Fig. 3A, including the offset of MA, FVA, TVA, FFA, and TFA. The labels corresponding to each group were shown in Fig. 3I. In the statistical data shown in Fig. 3B, the value was − 3.40 ± 2.56° and − 1.55 ± 2.18° separately in the conventional and CRAT groups. The CRAT showed statistically significant improvement in the lower limb force line correction. In both regular and challenging TKA, the correction of MA showed a consistent trend, represented by the less offset of MA (p < 0.05). Meanwhile, in the violin graphs, the decrease of dispersion was clearly announced. In the detailed measurement of femoral and tibial components (Fig. 3C-F), the CRAT group showed a similar increase in the accuracy of prosthesis location, especially the coronal location of the tibial component represented by TVA. In the TVA offset shown in Fig. 3D, the value of RCRAT and CCRAT was separately 0.00 ± 1.13°, and − 0.57 ± 1.38°, almost exactly as expected, which was significantly less than RCT and CCT group (-1.93 ± 1.64°, and − 2.26 ± 1.29° separately, P < 0.0001). In the other indexes without a statistical difference, the absolute offset values also decreased. For example, in the FFA offset (Fig. 3E), the value of conventional TKA and CRAT was separately − 2.20 ± 2.88° and − 1.92 ± 2.19°, while the alters were also observed in the subgroups. Although the difference was without statistical significance, we also considered them as additional evidence to prove that CRAT improved the spatial accuracy of the prosthesis.
CRAT improved knee function in 6-months follow-up
The labels corresponding to each group were shown in Fig. 4D. The preoperative OKS and HSS scores of participants were given in Table 1, while no statistical difference was found in the four groups. In the 6-months follow-up scores, the participants received CRAT performed better in the self-reported knee function, reflected by the decreased OKS scores (Fig. 3G, 21.52 ± 3.98 vs 19.38 ± 3.61 in RCT vs RCRAT, P < 0.01; 19.65 ± 4.53 vs 16.52 ± 2.73 in CCT vs CCRAT, P < 0.05) and increased HSS scores (Fig. 3H, 77.74 ± 5.47 vs 82.19 ± 2.56 in RCT vs RCRAT, P < 0.0001; and 76.22 ± 4.96 vs 79.91 ± 2.66 in CCT vs CCRAT, P < 0.0001). These results demonstrated that CRAT effectively improved postoperative knee function and was satisfactory.
CRAT caused more postoperative pain and blood loss
In Fig. 4A, the VAS score in the 3rd postoperative day was significantly higher in the CRAT group, especially in the challenging TKA (2.48 ± 0.80 vs. 1.70 ± 0.70, CCT vs. CCRAT, p = 0.0009), indicating that participants who underwent the CRAT suffered more pain compared with the conventional TKA in the early postoperative stage.
In the intraoperative blood loss (Fig. 4B), blood loss in the CCRAT group was 34.10% compared to the CCT group (P < 0.0001), which might be explained by the more accurate osteotomy and reduction of unexpected tissue damage. Although the intraoperative blood loss decreased in the regular TKA, the value is without statistical difference. The trend showed a reversed difference in the postoperative blood loss calculated on the 3rd postoperative day (Fig. 4C). The CRAT group showed a significantly higher blood loss compared to the conventional group (661.9 ± 328.9 vs. 860.5 ± 353.7 ml, P < 0.01). While the increase was dependent primarily on the regular TKA (604.1 ± 296.2 vs. 861.9 ± 295.5 in RCT vs. RCRAT, P < 0.01) instead of challenging TKA (725.7 ± 358.6 vs. 904.2 ± 368.4 in CCT vs. CCRAT, P = 0.1389).