How does a systematic tuning protocol for ankle foot orthosis–footwear combinations affect gait in children in cerebral palsy?

Figures & data

Figure 1. Lower leg/foot markers for (A) NS-SHOES (non-supportive textile shoes) and (B) AFO-footwear combination. Heel height was incremented by placing wedges of 5, 10, and 15 mm below the heel surface of the shoe (indicated with I, (B)). Shank to vertical angle (SVA) was calculated as the orientation of the shank (knee joint centre to ankle joint centre), to the vertical in the sagittal plane. Foot to horizontal angle (F2H) was calculated as the position of the foot (MT2-HEE) to the horizontal in the sagittal plane. Note that markers remained attached to the shoe and AFO for all AFO walking trials.

Figure 2. Time-normalised gait curves (left panel) and accompanying values at specific gait events (right panel) for a 9 y old girl walking with knee hyperextension (EXT), for sagittal hip and knee angles, internal knee moment, shank to vertical angle (SVA), and foot to horizontal angle (F2H). NS-SHOES: non-supportive flexible shoes (red/dashed), AFO: ankle foot orthosis (green), with incremented heel height of 5, 10, and 15 mm. Vertical dash-dotted lines (left) represent timing of gait events (initial contact (IC), peak knee flexion (PKF), midstance (MST), and maximal knee extension at terminal stance (TST)). Horizontal dash-dotted lines (right) represent mean ± 1SD of typically developing children. Positive foot to horizontal angles indicate an upwards positioned forefoot, with respect to the floor surface. Recl: reclined; incl: inclined.

Figure 3. Effect of ankle foot orthoses with incremented heel height (AFO, +5, +10, and +15 mm) on sagittal hip, knee, shank to vertical (SVA), and foot to horizontal (F2H) angles. Group results (mean-SD) are presented for children walking with excessive knee flexion gait pattern (FLEX) and knee hyperextension (EXT). NS-SHOES: non-supportive flexible shoes; AFO: ankle foot orthosis; incl: inclined; recl: reclined; up: forefoot up with respect to floor; down: forefoot down with respect to floor (i.e., representing heel rise). Note that no significant interaction effect was found between group and heel height.

Table 1. Characteristics of the participants and their ankle foot orthoses (AFOs).

Subject	Age	GMFCS	Uni-Bilat	Gait type^a	TM speed (m/s)	AFO type	Material	Footplate^b
1	12	II	2	FLEX	0.87	Ventral	Resin	Stiff
2	10	I	1	FLEX	0.75	Dorsal, PLS	Carbon	Rigid
3	10	II	2	FLEX	0.80	Dorsal, PLS	Carbon	Rigid
4	12	I	2	FLEX	0.95	Dorsal, PLS	Carbon	Rigid
5	14	II	2	FLEX	0.82	Dorsal, PLS	Carbon	Rigid
6	11	II	1	FLEX	0.80	Dorsal, PLS	Carbon	Rigid
7	9	I	2	FLEX	0.70	Dorsal	Resin	Stiff
8	6	II	2	FLEX	1.00	Dorsal	Resin	Flexible
9	7	II	2	FLEX	0.90	Dorsal, PLS	Carbon	Rigid
10	8	I	1	EXT	0.70	Dorsal, PLS	Carbon	Rigid
11	18	I	1	EXT	0.90	Dorsal, PLS	Carbon	Rigid
12	11	II	2	EXT	0.50	Dorsal, PLS	Carbon	Rigid
13	12	I	1	EXT	1.15	Dorsal, PLS	Carbon	Rigid
14	11	II	1	EXT	1.10	Dorsal	Resin	Stiff
15	16	I	1	EXT	1.10	Dorsal	Resin	Flexible
16	7	I	1	EXT	1.00	Dorsal, Hinge	Resin	Flexible
17	11	I	1	EXT	1.20	Dorsal, PLS	Carbon	Rigid
18	11	I	1	EXT	0.90	Dorsal, PLS	Carbon	Rigid

TM: treadmill; GMFCS: gross motor classification system; Uni-Bilat: unilateral (1) or bilateral (2) AFO types: PLS: posterior leaf spring. Hinge: hinged AFO, allowing ankle dorsiflexion, but no plantarflexion (stop at 0°).

^a Gait type (FLEX/EXT) was classified based on mean knee flexion-extension angles during walking without AFOs, in the NS-SHOES/non supportive shoes condition.

^b AFO footplates were classified as “stiff” when using carbon holding energy-storing capacity and rigid when no torsion or motion of the material was possible. In case of a flexible footplate, stiffness of the footplate was regarded to be below the stiffness of the foot itself. Note that the resin AFOs are considered rigid, allowing no range of motion in the ankle joint.

Table 2. Group results (mean ± SD) of children walking with excessive knee flexion (FLEX) and knee hyperextension (EXT).

									Effect NS-SHOES versus AFO			Effect incremented heel height
				NS-SHOES	AFO	AFO + 5 mm	AFO + 10 mm	AFO + 15 mm	Group FLEX/EXT	Condition NS-SHOES AFO	Interaction Group × condition	Group FLEX/EXT	Condition AFO/+..mm	Interaction Group × condition
Parameter	Event	TD	Group	Mean ± SD	Mean ± SD	Mean ± SD	Mean ± SD	Mean ± SD	p	p	p	p	p	p
Kinematics
Hip angle (°)	IC	32.4 ± 5.3	Flex	37.9 ± 9.9	37.5 ± 9.5	39.2 ± 9.9	39.8 ± 9.9	40.1 ± 9.3	0.446	0.918	0.856	0.462	<0.001*	0.588
			Ext	34.6 ± 7.8	34.7 ± 7.1	35.7 ± 7.4	36.8 ± 7.3	37.5 ± 7.4
	PKF	8.8 ± 4.5	Flex	8.7 ± 4.7	7.6 ± 6.7	7.7 ± 7.1	7.7 ± 7.0	8.0 ± 6.5	0.031*	0.592	0.360	0.086	<0.001*	0.091
			Ext	1.8 ± 6.1	2.1 ± 5.6	2.3 ± 6.2	2.2 ± 5.8	2.8 ± 6.0
	MST	6.4 ± 5.1	Flex	9.2 ± 5.6	8.3 ± 7.4	8.9 ± 7.9	9.1 ± 7.7	9.5 ± 7.4	0.025*	0.323	0.650	0.120	<0.001*	0.403
			Ext	2.0 ± 4.8	1.6 ± 6.3	1.7 ± 6.1	2.2 ± 5.8	2.5 ± 6.1
	TST	2.4 ± 6.9	Flex	9.3 ± 8.6	8.0 ± 8.4	7.1 ± 8.0	7.9 ± 8.9	7.3 ± 8.4	0.050	0.030*	0.239	0.003*	0.003*	0.551
			Ext	2.4 ± 8.0	–1.6 ± 9.4	–2.1 ± 9.2	–2.1 ± 8.9	–2.4 ± 9.1
Knee angle (°)	IC	0.5 ± 3.6	Flex	26.8 ± 5.6	24.4 ± 9.2	25.5 ± 8.9	26.7 ± 8.4	28.4 ± 8.1	0.010*	0.102	0.391	0.018	<0.001*	0.837
			Ext	15.1 ± 8.7	14.3 ± 9.0	14.9 ± 8.7	15.9 ± 8.1	18.0 ± 8.3
	PKF	17.0 ± 5.3	Flex	33.0 ± 7.0	31.2 ± 9.7	33.2 ± 10.3	34.3 ± 9.5	36.5 ± 9.6	0.046*	0.534	0.060	0.086	<0.001*	0.091
			Ext	22.1 ± 9.1	25.5 ± 8.4	25.9 ± 7.7	25.9 ± 8.0	27.9 ± 7.4
	MST	10.4 ± 3.8	Flex	21.1 ± 4.7	16.3 ± 4.8	17.7 ± 5.6	20.3 ± 6.0	22.4 ± 4.8	<0.001*	0.934	0.016*	0.120	<0.001*	0.403
			Ext	8.0 ± 7.0	13.1 ± 6.7	14.1 ± 6.5	15.1 ± 5.2	17.7 ± 5.4
	TST	6.0 ± 4.6	Flex	15.4 ± 5.3	11.4 ± 5.2	11.1 ± 5.6	12.9 ± 6.2	14.1 ± 5.8	<0.001*	0.208	0.065	0.001*	0.003*	0.551
			Ext	0.9 ± 3.4	1.7 ± 5.5	2.1 ± 4.4	2.2 ± 3.1	4.8 ± 4.0
SVA (°)	IC	–19.1 ± 3.6	Flex	0.7 ± 4.0	0.2 ± 7.8	–0.2 ± 6.4	0.3 ± 6.8	1.0 ± 6.0	0.013*	0.339	0.608	0.026	0.141	0.925
			Ext	–6.5 ± 4.3	–8.1 ± 7.9	–8.6 ± 8.3	–8.6 ± 7.7	–7.3 ± 8.2
	PKF	1.3 ± 2.6	Flex	11.1 ± 4.3	11.7 ± 6.1	12.5 ± 5.7	13.1 ± 6.0	14.6 ± 5.2	0.037*	0.214	0.453	0.051	<0.001*	0.292
			Ext	5.0 ± 5.7	7.2 ± 5.5	7.2 ± 5.5	7.0 ± 5.3	8.6 ± 5.1
	MST	7.3 ± 2.4	Flex	15.1 ± 2.9	14.2 ± 4.2	14.9 ± 3.8	16.0 ± 4.1	17.2 ± 3.8	0.009*	0.419	0.119	0.114	<0.001*	0.426
			Ext	8.5 ± 3.7	11.3 ± 5.5	11.4 ± 5.7	11.8 ± 5.0	13.5 ± 5.0
	TST	16.0 ± 2.9	Flex	21.7 ± 3.9	20.8 ± 4.1	21.3 ± 4.4	22.4 ± 4.4	23.6 ± 4.2	0.042*	0.506	0.189	0.254	<0.001*	0.431
			Ext	15.5 ± 4.5	18.1 ± 7.0	18.7 ± 6.0	18.9 ± 5.3	21.4 ± 4.5
F2H (°)	IC	–22.5 ± 4.7	Flex	–3.1 ± 4.6	–5.3 ± 8.3	–5.0 ± 6.8	–4.3 ± 7.4	–3.4 ± 7.0	0.586	0.586	0.004*	0.097	0.068	0.706
			Ext	–0.41 ± 6.3	–11.7 ± 9.6	–12.1 ± 10.2	–12.1 ± 9.5	–10.7 ± 10.1
	PKF	–2.1 ± 1.9	Flex	–0.4 ± 3.1	1.9 ± 4.1	3.5 ± 4.0	4.3 ± 3.0	6.1 ± 3.7	0.184	0.526	0.452	0.933	<0.001*	0.476
			Ext	1.3 ± 3.1	2.2 ± 5.9	3.2 ± 6.0	3.9 ± 6.1	5.6 ± 6.0
	MST	–0.9 ± 2.2	Flex	1.8 ± 4.1	4.2 ± 4.1	5.3 ± 3.8	6.5 ± 4.0	7.9 ± 4.0	0.271	0.904	0.549	0.713	<0.001*	0.631
			Ext	2.9 ± 5.2	3.6 ± 6.6	4.5 ± 6.4	5.2 ± 6.1	6.8 ± 6.2
	TST	3.1 ± 2.9	Flex	7.1 ± 7.8	8.8 ± 4.6	9.9 ± 5.2	10.9 ± 5.5	12.3 ± 5.8	0.547	0.647	0.684	0.409	<0.001*	0.479
			Ext	6.4 ± 8.2	6.7 ± 8.6	7.2 ± 8.2	7.6 ± 7.7	9.7 ± 7.4
GPS (°)		6.4 ± 2.0	Flex	10.1 ± 3.8	9.9 ± 2.9	10.2 ± 3.2	10.0 ± 3.3	10.3 ± 3.5	0.197	0.237	0.775	0.173	0.392	0.958
			Ext	8.5 ± 1.7	8.1 ± 1.8	8.3 ± 1.8	8.4 ± 1.9	8.5 ± 2.1
Moments
Hip moment (Nm/kg)	IC	0.41 ± 0.16	Flex	0.32 ± 0.08	0.22 ± 0.21	0.21 ± 0.16	0.18 ± 0.16	–17 ± 0.15	0.575	0.002*	0.625	0.566	0.470	0.163
			Ext	0.37 ± 0.15	0.24 ± 0.11	0.22 ± 0.12	0.25 ± 0.14	0.24 ± 0.14
	PKF	0.44 ± 0.14	Flex	0.57 ± 0.21	0.58 ± 0.20	0.60 ± 0.20	0.60 ± 0.20	0.59 ± 0.20	0.319	0.910	0.841	0.112	0.395	0.086
			Ext	0.46 ± 0.30	0.46 ± 0.24	0.42 ± 0.24	0.42 ± 0.24	0.39 ± 0.21
	MST	0.07 ± 0.08	Flex	0.33 ± 0.16	0.31 ± 0.16	0.31 ± 0.16	0.30 ± 0.17	0.30 ± 0.16	0.124	0.158	0.493	0.038*	0.277	0.571
			Ext	0.21 ± 0.21	0.16 ± 0.18	0.16 ± 0.18	0.13 ± 0.17	0.11 ± 0.15
	TST	–0.21 ± 0.19	Flex	–0.03 ± 0.24	–0.08 ± 0.26	–0.11 ± 0.30	–0.11 ± 0.27	–0.10 ± 0.26	0.033*	0.009*	0.095	0.006*	0.010*	0.049*
			Ext	–0.18 ± 0.15	–0.36 ± 0.17	–0.42 ± 0.18	–0.44 ± 0.17	–0.51 ± 0.18
Knee moment (Nm/kg)	IC	–0.22 ± 0.08	Flex	–0.06 ± 0.10	–0.03 ± 0.11	–0.02 ± 0.11	–0.01 ± 0.12	0.02 ± 0.14	0.141	0.002*	0.156	0.401	0.005*	0.654
			Ext	–0.15 ± 0.09	–0.07 ± 0.08	–0.06 ± 0.09	–0.03 ± 0.12	–0.03 ± 0.12
	PKF	–0.16 ± 0.19	Flex	0.36 ± 0.21	0.24 ± 0.24	0.31 ± 0.27	0.33 ± 0.25	0.42 ± 0.28	0.534	0.457	0.010*	0.162	<0.001*	0.995
			Ext	0.20 ± 0.22	0.40 ± 0.22	0.49 ± 0.22	0.49 ± 0.23	0.47 ± 0.22
	MST	–0.07 ± 0.11	Flex	–0.09 ± 0.12	–0.25 ± 0.21	–0.21 ± 0.21	–0.15 ± 0.22	–0.08 ± 0.21	0.983	0.982	0.007*	0.09	<0.001*	0.518
			Ext	–0.25 ± 0.20	–0.09 ± 0.26	–0.01 ± 0.25	–0.05 ± 0.25	–0.11 ± 0.25
	TST	–0.27 ± 0.12	Flex	–0.13 ± 0.05	–0.29 ± 0.16	–0.31 ± 0.15	–0.28 ± 0.17	–0.24 ± 0.18	0.008*	0.242	0.025*	0.652	0.007*	0.551
			Ext	–0.40 ± 0.16	–0.35 ± 0.17	–0.36 ± 0.24	–0.33 ± 0.22	–0.26 ± 0.24

NS-SHOES: non-supportive flexible shoes; AFO: ankle foot orthosis, incremented with 5, 10, and 15 mm wedge below the heel surface. IC: initial contact; PKF: instance of peak knee flexion; MST: midstance; TST: terminal stance; SVA: shank to vertical angle; F2H: foot to horizontal angle; GPS: gait profile score, TD: typically developing children, mean value given for reference. Positive kinematic outcomes represent: hip/knee flexion, shank inclination (SVA), and forefoot orientated upwards with respect to the floor (F2H). For joint moments, positive outcomes represent an internal knee/hip extension moment.

* Statistical significance (p < 0.05).

Figure 4. Individual shank to vertical angle (SVA) at midstance scattered against sagittal knee angles (upper row), sagittal internal knee moment (second row) and SVA (third row) at initial contact, midstance (MST) and terminal stance for different walking conditions. Mean data of each condition are presented for all individuals. Regression lines (dotted) are presented when generalised estimation equations (GEE) analysis indicated a significant relation (p < 0.05). Grey squares represent reference data of typically developing children (±1SD) [28]. NS-SHOES: non-supportive flexible shoes; AFO: ankle foot orthosis, incremented with 5, 10, and 15 mm wedge below the heel surface. GPS: gait profile score.

Oudenhoven LM, Booth ATC, Buizer AI, et al. How normal is normal: consequences of stride to stride variability, treadmill walking and age when using normative paediatric gait data. Gait Posture. 2019;70:289–297.

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