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

Table 1 Baseline characteristics

	Control group	Introduction group	P value (Control vs Introduction)	Follow-up group	P value (Control vs Follow-up)	Test
Subjects count, n (%)	75 (100)	75 (100)		62 (100)
Age, mean (range)	65.6 (49-84)	61.1 (39-81)	0.009	65.1 (45-86)	0.90	Mann-Whitney U test
Gender, male/female (%)	31/44 (m = 41%, f = 59%)	38/37 (m = 51%, f = 49%)	0.25	24/38 (63.2)	0.76	χ2
BMI, median (range)	29.4 (17.3-45.1)	29.4 (19.4-46.9)	1.0	28.8 (20.3-51.9)	1.0	Mann-Whitney U test
ASA Score, median	2	2	0.23	2	0.80	χ2
ASA Score I, n (%)	11 (14.7)	14 (18.7)		7 (11.3)
ASA Score II, n (%)	46 (61.3%)	49 (65.3%)		38 (61.3)
ASA Score III, n (%)	18 (24%)	10 (13.3%)		17 (27.4)
Pre-operative TFA, mean (95%CI)	1.2 valgus (0.5 varus–2.4 valgus)	0.1 varus (1.2 varus–1.0 valgus)	0.12	0.4 varus (1.7 varus–0.9 valgus)	0.076	Unpaired T-test
Varus Outliers, n (%)	47 (62.7)	55 (73.3)		50 (80.6)
Valgus Outliers, n (%)	5 (6.7)	2 (2.7)		2 (3.3)

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 or Fisher’s exact t-test. Fischer’s exact test was applied when chi-squared (χ²) conditions may be violated due to expected cell number count below 5 and/or total cell count below 40. Pre-operative TFA outliers found based on the principles of neutral knee alignment[13]. Pre-operative TFA is measured in degrees. 95%CI: 95% Confidence interval; TFA: Tibio-femoral angle; BMI: Body mass index; ASA: American Society of Anaesthesiologists.