Multi-factorial analysis of time efficiency in total knee arthroplasty

Figures & data

Table I.  Comparison of means for total time in the operating room, surgical procedure time, and tourniquet time.

Navigation group	Total time (min)	Surgery time (min)	Tourniquet time (min)
Pre-navigation	131 ± 21	94 ± 17	64 ± 12
Medtronic	139 ± 21	101 ± 15	75 ± 12
PRAXIM custom	126 ± 15	86 ± 12	60 ± 9

Table II.  Results of ANOVA and pair-wise comparison using Tukey's adjustment for significant differences between surgical navigation groups: Difference in means (95% simultaneous confidence interval; ^**denotes significant result).

	p-value for equality among groups	Medtronic vs. pre-navigation	Medtronic vs. PRAXIM	Pre-navigation vs. PRAXIM
Total time	0.031	8.43 (−3.57, 20.44)	13.44^** (1.40, 25.40)	4.97 (−7.04, 16.97)
Surgical time	0.002	7.63 (−1.84, 17.10)	14.87^** (5.40, 24.34)	7.23 (−2.24, 16.70)
Tourniquet time	<0.001	11.00^** (4.00, 18.00)	14.60^** (7.61, 21.60)	3.60 (−3.40, 10.60)

Table III.  Chi-square analysis is performed to test associations between categorical variables and surgical navigation type, and the F-test is used to compare mean values for the three navigation groups for continuous variables.

Variable	p-value	Pre-navigation mean (SD)	PRAXIM mean (SD)	Medtronic mean (SD)
Age	F2.87 = 1.20, p = 0.31	64.5 (9.9)	67.2 (8.6)	68.1 (9.6)
BMI	F2.87 = 1.23, p = 0.30	31.1 (6.3)	32.9 (8.0)	30.2 (5.9)
Knee score	F2.86 = 0.48, p = 0.62	41.5 (7.9)	42.3 (17.3)	39.3 (8.8)
Gender	X = 0.0, p = 1.00	17/30 female	17/30 female	17/30 female
Patellar resurfacing	X = 24.3, p < 0.01	9/30 non-resurfaced	26/30 non-resurfaced	10/30 non-resurfaced

Table IV.  Multiple linear regression analysis with surgical time as outcome, adjusting for patellar resurfacing, BMI, deformity category and navigation type.

Variable	Estimate (Std. error)	F-value	p-value
Patellar resurfacing:		16.53	<0.001
No	−9.13 (3.79)
Yes	0.00 (reference)
BMI	0.14 (0.25)	0.13	0.72
Deformity group:		0.82	0.54
Valgus, 0–4°	2.45 (9.66)
Varus, 0–4°	−5.96 (4.69)
Valgus, 5–9°	2.51 (7.24)
Varus, 5–9°	0.00 (reference)
Valgus, 10+°	−0.18 (5.84)
Varus, 10+°	−6.26 (6.28)
Navigation type:		3.58	0.54
Medtronic	8.09 (3.98)
PRAXIM	−2.71 (4.65)
Pre-navigation	0.00 (reference)

Table V.  Published studies evaluating mean computer navigation and conventional surgery times in total knee arthroplasty.

	Mean surgery time (min)
Study	Conventional	Computer navigated	SD
Bäthis et al., 2004 [2]	64	78	P < 0.01
Victor et al., 2004 [13]	73.5	93	P < 0.0001
Chauhan et al., 2004 [4]	67	80	P < 0.001
Duckling et al., 2005 [5]	79	92	P < 0.001
Jenny et al., 2005 [8]	99	108	P < 0.01
Seon et al., 2006 [11]	92	97	NSD
Kim et al., 2007 [9]	82	97	P < 0.001
Bauwens et al., 2007 [15]	73	90	P < 0.001
Dutton et al., 2008 [6]	83	107	P < 0.001
Summary	81 ± 12	95 ± 11

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