Early full weight bearing is safe in open-wedge high tibial osteotomy

Figures & data

Figure 1.  The OW-HTO, Tomofix implant and tantalum beads used for RSA.

Figure 2.  The 6 possible directions of migration are shown schematically. T: transalation in mm; R: rotation in degrees; x: transverse axis; y: longitudinal axis; z: sagittal axis.

Table 1.  Preoperative patient characteristics for the early weight bearing (E) group and the standard weight bearing (S) group. Mean (SD)

	E	S	p-value
Age	49 (8)	53 (8)	0.1
Weight	81 (11)	86 (12)	0.3
Height	177 (8)	176 (11)	0.4
BMI	26 (3)	28 (3)	0.1
Varus angle pre-op	6.0° (2.8°)	5.0° (2.6)	0.3
Planned correction	8.9° (2.4°)	8.1° (3.1)	0.3
VAS pain	51 (25)	56 (22)	0.6
Lysholm	57 (16)	63 (16)	0.3

Table 2.  KOOS, WOMAC and Tegner scores preoperatively and at the postoperative follow-up times for the early weight bearing (E) group. Mean (SD)

Score	Preoperatively	6 weeks	3 months	6 months	12 months
KOOS
Pain	43 (17)	67 (23)^a	68 (22)^a	78 (21)^a	74 (19)^a
Symptom	47 (14)	54 (12)	52 (14)	58 (11)^a	60 (15)^a
ADL	47 (18)	67 (18)	69 (21)^a	77 (26)^a	76 (19)^a
Sp/Rec	21 (20)	20 (22)	37 (30)	47 (32)^a	41 (27)^a
QOL	35 (11)	36 (12)	40 (18)	44 (16)^a	49 (11)^a
WOMAC
Total	49 (16)	30 (17)^a	28 (20)^a	21 (22)^a	17 (14)^a
Pain	11 (4)	6 (4)^a	6 (5)^a	4 (4)^a	4 (4)^a
Stiffness	3 (1)	2 (1)^a	2 (1)^a	1 (1)^a	1 (1)^a
Function	36 (12)	23 (12)^a	21 (14)^a	15 (18)^a	16 (13)^a
TEGNER	1.9 (1.4)			2.9 (1.6)	3.1 (1.5)

ADL: activities of daily living; Sp/Rec: sport/recreation; QOL: quality of life.

^a p < 0.05 relative to the preoperative score.

Table 3.  Migration in the early weight bearing (E) group and the standard weight bearing (S) group at 3 follow-up times. Values are translation (T) in mm and rotation (R) in degree.

Follow-up	E		S
Axis	Mean (SD)	(Range)	Mean (SD)	(Range)
6 weeks
Tx	-0.02 (0.36)	(-0.70–0.60)	0.17 (0.24) ^b	(-0.09–0.84)
Ty	-0.10 (0.24)	(-0.75–0.27)	-0.15 (0.19) ^b	(-0.64–0.19)
Tz	-0.01 (0.14) ^c	(-0.20–0.30)	-0.19 (0.37) ^b, c	(-0.79–0.46)
Rx	-0.16 (0.74)	(-1.18–1.78)	-0.57 (0.89) ^b	(-3.20–1.03)
Ry	-0.16 (0.52)	(-0.92–0.60)	-0.15 (0.60)	(-1.70–0.80)
Rz	-0.01 (0.67)	(-1.69–1.04)	-0.05 (0.66)	(-1.79–1.10)
3 months
Tx	-0.01 (0.40)	(-0.86–0.69)	0.14 (0.24) ^b	(-0.27–0.71)
Ty	-0.13 (0.22)	(-0.75–0.19)	-0.17 (0.25) ^b	(-0.74–0.22)
Tz	-0.05 (0.20)	(-0.50–0.32)	-0.17 (0.33) ^b	(-0.78–0.40)
Rx	-0.41 (0.99)	(-2.11–2.17)	-0.88 (1.47) ^b	(-6.14–1.49)
Ry	-0.09 (0.58)	(-1.18–0.94)	-0.05 (0.47)	(-0.84–0.73)
Rz	0.06 (0.75)	(-1.72–1.42)	0.16 (0.54)	(-0.79–1.04)
12 month
Tx	-0.03 (0.40)	(-0.81–0.73)	0.07 (0.25)	(-0.43–0.58)
Ty	-0.18 (0.27) ^a	(-0.97–0.16)	-0.29 (0.49) ^b	(-1.83–0.14)
Tz	-0.08 (0.21)	(-0.53–0.35)	-0.23 (0.32) ^b	(-0.76–0.53)
Rx	-0.73 (0.88) ^a	(-2.26–0.60)	-1.18 (1.12) ^b	(-4.45–0.73)
Ry	-0.07 (0.51)	(-0.89–0.75)	0.12 (0.67)	(-0.78–2.06)
Rz	0.19 (0.82)	(-1.76–1.46)	0.45 (0.86)	(-0.68–2.06)

In 1 patient in the S group, the postoperative RSA radiograph was missing; for this patient, the 6-week result served as baseline.

^a,b Significant migration (2-sided, p < 0.05) at the follow-up within the ^a E and ^b S groups, tested with the Wilcoxon test, but not clinically relevant.

^c Significant difference in migration (2-sided, p < 0.05) in the S group compared with the E group, tested with the Mann–Whitney U test, but migrations were below the detection limit.

Table 4.  Increases in migration in the early weight bearing (E) group and the standard weight bearing (S) group from 6 weeks to 3 months and from 3 to 12 months postoperatively. Values are translation (T) in mm and rotation (R) in degree.

	E		S
	1.5–3 months	3–12 months	1.5–3 months	3–12 months
Tx	0.01 (0.08)	-0.02 (0.09)	-0.03 (0.23)	-0.07 (0.21)
Ty	-0.04 (0.06) ^a	-0.04 (0.07) ^a	-0.02 (0.24)	-0.13 (0.37)
Tz	-0.07 (0.17)	-0.02 (0.11)	0.02 (0.20)	-0.06 (0.23)
Rx	-0.25 (0.35) ^a	-0.30 (0.47) ^a	-0.29 (0.82)	-0.40 (0.89)
Ry	0.07 (0.48)	0.02 (0.25)	0.06 (0.45)	0.21 (0.55)
Rz	0.07 (0.20)	0.12 (0.18) ^a	0.10 (0.39)	0.29 (0.55) ^b

^{a, b} Significant increase (2-sided, p < 0.05) during the time intervals within the ^a E and ^b S groups, tested with the Wilcoxon test, but not clinically relevant.