Comparison of functional results with navigation-assisted minimally invasive and conventional techniques in bilateral total knee arthroplasty

Figures & data

Figure 1. Skin incision and position of sensor fixing screws.

Figure 2. A 68-year-old woman with bilateral TKA (CON TKA on the left side; NA-MIS TKA on the right) at the one-year follow-up showing the smaller incision on the NA-MIS side.

Table I.  Comparison of the preoperative data of the NA-MIS and CON sides.

	NA-MIS side	CON side	p
Preoperative  HSS (point)	68.5 (51–83)	66.5 (48–81)	0.324
Range of motion (°)	115.5 (30–140)	117.0 (35–135)	0.777
Femorotibial  angle (° ± SD)	−0.5 ± 7.2*	−0.4 ± 7.2*	0.968

* = varus

Table II.  Comparison of results at 3 and 6 months postoperatively for the NA-MIS and CON sides (all values shown as mean ± standard deviation).

	NA-MIS side	CON side	p
3 months postop.
ROM	125.8 ± 9.8	121.2 ± 7.9	0.074
HSS score	90.0 ± 4.0	87.3 ± 5.7	0.040
WOMAC
Pain	8.1 ± 1.0	9.3 ± 2.1	0.024
Function	27.0 ± 3.5	29.0 ± 3.1	0.059
Stiffness	3.6 ± 1.3	4.0 ± 1.1	0.230
Total	38.8 ± 4.8	42.0 ± 4.6	0.029
6 months postop.
Range of motion	128.4 ± 9.3	126.8 ± 10.8	0.633
HSS score	92.7 ± 3.8	89.8 ± 5.5	0.042
WOMAC
Pain	7.1 ± 1.7	8.3 ± 1.9	0.031
Function	25.2 ± 3.8	27.2 ± 4.2	0.116
Stiffness	2.8 ± 1.1	3.0 ± 1.3	0.609
Total	35.1 ± 5.0	38.5 ± 4.9	0.031

Table III.  Comparison of results at 9 months and one year postoperatively for the NA-MIS and CON sides (all values shown as mean ± standard deviation).

	NA-MIS side	CON side	p
9 months postop.
Range of motion	128.3 ± 6.8	127.0 ± 10.7	0.737
HSS score	93.1 ± 3.8	90.4 ± 5.3	0.111
WOMAC
Pain	6.2 ± 1.2	7.6 ± 2.1	0.020
Function	24.3 ± 6.5	25.2 ± 6.7	0.678
Stiffness	2.9 ± 1.0	3.0 ± 1.2	0.603
Total	33.5 ± 7.0	35.5 ± 7.8	0.545
1 year postop.
Range of motion	129.5 ± 8.0	127.1 ± 8.8	0.364
HSS score	93.3 ± 4.0	92.8 ± 4.3	0.730
WOMAC
Pain	6.1 ± 1.5	7.2 ± 2.3	0.122
Function	23.0 ± 4.5	25.0 ± 7.4	0.573
Stiffness	2.8 ± 1.0	2.9 ± 1.0	0.504
Total	31.9 ± 5.6	35.2 ± 9.8	0.277

Table IV.  Comparisons of radiological outlier results for the two groups.

	NA-MIS side	CON side	p
Mechanical axis angle
Average value (°)	−0.7 ± 1.6*	−0.8 ± 2.5*	0.815
No. of outliers	2	8	0.043
Coronal inclination  of femoral prosthesis
Average value (°)	88.9 ± 2.6	88.7 ± 2.8	0.769
No. of outliers	3	9	0.061
Coronal inclination  of tibial prosthesis
Average value (°)	90.5 ± 1.7	90.1 ± 2.3	0.365
No. of outliers	2	3	0.645

* = varus