Early clinical outcome and learning curve following unilateral primary total knee arthroplasty after introduction of a novel total knee arthroplasty system

Table 2 Alignment of the total joint arthroplasty including the tibial and femoral components

	Control group	Introduction group	P value (Control vs Introduction)	Follow-up group	P value (Control vs Follow-up)	Test
Tibial AP-alignment, mean (95%CI)	88.5 (88.1-88.9)	88.5 (88.1-88.9)	0.68	88.5 (88.1-88.8)	1.0	Mann-Whitney U test
Outliers, n (%)	11 (14.7)	10 (13.3)	0.81	10 (16.1)	0.81	χ2
Femoral AP-alignment, mean (95%CI)	96.0 (95.5-96.5)	95.4 (95.0-95.8)	0.06	95.6 (95.2-96.0)	0.22	Unpaired T-test
Outliers, n (%)	21 (28)	14 (18.7)	0.18	11 (17.7)	0.16	χ2
Post-operative TFA, mean (95%CI)	4.4 valgus (3.8-5.0)	3.8 valgus (3.3-4.4)	0.16	4.2 valgus (3.6-4.8)	0.62	Unpaired T-test
Outliers, n (%)	25 (33.3)	26 (34.7)	0.86	23 (37.1)	0.65	χ2
Medial Tibial Overhang, n (%)	5 (6.7)	8 (10.7)	0.38	6 (9.7)	0.52	χ2
Lateral Tibial Overhang, n (%)	6 (8.0)	7 (9.3)	0.77	4 (6.5)	0.73	χ2
Tibial Slope, mean (95%CI)	88.8 (88.2-89.4)	85.1 (84.4-85.8)	< 0.0001	84.9 (84.2-85.5)	< 0.0001	Unpaired T-test
Outliers, n (%)	21 (28.0)	13 (17.3)	0.12	12 (19.4)	0.24	χ2
Femoral Flexion (FF), mean (95%CI)	86.2 (85.3-87.0)	88.2 (87.8-88.7)	< 0.0001	88.2 (87.8-88.6)	< 0.0001	Unpaired T-test
Outliers, n (%)	44 (58.7)	28 (37.3)	0.009	16 (25.8)	< 0.0001	χ2

For AP alignment femoral and tibial components, < 90 degrees correspond to varus placement and > 90 degrees correspond to valgus placement. Outliers were found based on intervals for optimal alignment of the components[13]. For normally distributed data, in accordance with Shapiro Wilk-test, kurtosis, skewness and histogram inspection mean values are presented and p-value calculated using the unpaired T-test. Otherwise Mann-Whitney U test was applied. P values for categorical data is calculated using Pearsons Chi-squared (χ²) test. 95%CI: 95 % Confidence interval; TFA: Tibio-femoral angle.