Adaptations from the prosthetic and intact limb during standing on a sway-referenced support surface for transtibial prosthesis users

Figures & data

Table 1. Participant characteristics.

Participant	Sex	Height	Weight	Age	YSA	Cause	Amp	Dom	Liner	Susp	Foot	Control	Sex	Height	Weight	Age
1	M	182	82	63	18	Trauma	L	R	Gel	Vacuum	ESAR	C1	M	177	76	62
2	M	173	94	67	24	Trauma	R	R	Gel	Vacuum	ESAR	C2	M	172	103	65
3	M	181	66	30	13	Trauma	L	R	Gel	Pin	ESAR	C3	M	178	70	32
4	M	181	84	42	17	Trauma	L	R	Gel	Seal-in	ESAR	C4	M	183	86	47
5	M	180	65	59	21	Vascular	L	R	Gel	Pin	ESAR	C5	M	177	68	59
6	F	172	68	50	33	Infektion	L	R	Gel	Sleeve	ESAR	C6	F	172	76	55
7	M	190	78	44	8	Trauma	L	L	Pelite + gel	Pin	ESAR	C7	M	192	87	48
8	M	178	86	50	8	Trauma	R	R	Gel	Vacuum	ESAR	C8	M	183	85	50
9	M	176	92	80	10	Trauma	R	A	Gel	Pin	ESAR	C9	M	175	77	75
10	M	183	88	36	7	Trauma	R	R	Gel	Vacuum	ESAR	C10	M	186	85	37
11	M	182	72	48	6	Trauma	L	R	Gel	Pump	ESAR	C11	M	185	73	49
12	M	183	77	55	5	Trauma	R	R	Gel	Vacuum	ESAR	C12	M	178	74	51
13	M	183	82	67	7	Trauma	R	R	Gel	Vacuum	ESAR	C13	M	181	78	66
14	M	183	78	33	7	Trauma	L	R	Gel	Vacuum	ESAR	C14	M	180	84	35
Mean (SD)	M = 13; F = 1	180.5 (4.6)	79.4 (9.2)	51.7 (14.4)	13.1 (8.3)	–	–	–	–	–	–	–	M = 13; F = 1	179.9 (5.6)	80.1 (9.0)	52.2 (12.5)

Participants 1–14 from TPU with matched CON. Sex (M: male; F: female), Height (m), Weight (kg), Age (years), YSA: years since amputation (years); cause of amputation, Amp: amputation side; (L: left; R: right); Dom: dominant side; (L: left; R: right; A: ambidextrous); Liner: material interface between residual limb and socket (Gel: gel liners such as silicone, Pelite: pelite foam), Susp: suspension form (Vacuum: non-active, negative pressure interface (one-way valve), Pin: distal pin, Seal-in: Seal-in liner, Pump: active electrical pump), Foot: energy storing and return foot (ESAR). Summary statistics (means and standard deviation (SD)) presented where appropriate.

Figure 1. The three individual foot position conditions (1–3). Condition 1 – the participant’s intact limb (black) is on the embedded forceplate (e) in the Neurocom Pro Balance Master (b), the individual’s prosthetic limb is standing on the force structure (d) which is resting on the embedded AMTI forceplate (c) in the floor (a). In condition 1, data from two forceplates are being collected: one set from the AMTI forceplate (STAT) (c) (prosthetic limb), and one set from the Neurocom forceplate (SWAY) (e) (intact limb). Condition 2 – the experimental conditions are the same but with reverse order of the intact and prosthetic limb (intact on the AMTI forceplate (c) and prosthetic on the Neurocom forceplate (e). In condition 2, data from two forceplates are being collected: one set from the AMTI forceplate (STAT) (c) (intact limb), and one set from the Neurocom forceplate (SWAY) (e) (prosthetic limb). Condition 3 – both limbs were on the Neurocom forceplate (e). In condition 2, data from one forceplate is being collected: the Neurocom forceplate (MIDDLE) (e) (resultant CoP from both limbs).

Figure 2. Data collection protocol. Each participant is tested in three-foot position conditions relating to which feet are on the Neurocom platform (both, intact and prosthetic). Coinciding with data collected from the Neurocom, was data collected from the AMTI at the same time. Whilst data from the intact foot on the Neurocom was collected (INTACT_SWAY), data was also collected from the prosthetic limb on the AMTI forceplate (PROS_STAT). For each of these foot position conditions, a randomized order of sway reference gains was applied to the support surface (stable, unstable, very unstable). Sway reference gains applied (1:1, 2:1) refer to the amount of angular sway referencing applied per angular deviation of the CoG in the anteroposterior plane [31].

Table 2. Mean difference and 95% CI of the difference for left-right (CON-Group) and intact-prosthetic side (TPU-Group) for each of the support surface conditions.

			95% confidence interval of the difference
Group	Condition	Mean difference (N)	Lower	Upper
TPU	Stable	−0.2	−1.0	0.6
	Unstable	1.2	−0.3	2.9
	Very Unstable	0.7	−2.1	3.6
CON	Stable	0.2	−0.4	0.8
	Unstable	0.3	−0.3	1.0
	Very Unstable	0.8	0.0	1.6

All units are in Newtons (N).

Figure 3. 95% CI of the anteroposterior CoP position for the STAT conditions (left – A) and the SWAY conditions (right – B) separated by support surface condition (stable, unstable, very unstable). Transtibial prosthesis users (TPU) group: Black lines indicate prosthetic limb, grey lines indicate intact limb, broken lines indicate middle position (for SWAY conditions (B) only). Control (CON) group: Black lines indicate left limb, grey lines indicate right limb, broken lines indicate middle position (for SWAY conditions (B) only). All units in meters (m).

Figure 4. 95% CI of the mean GRF amplitude for the STAT conditions in the anteroposterior direction (left – A) and mediolateral direction (right – B) separated by support surface condition (stable, unstable, very unstable). Transtibial prosthesis users (TPU) group: Black lines indicate prosthetic limb and grey lines indicate intact limb. Control (CON) group: Black lines indicate left limb and grey lines indicate right limb. All units in newtons (N).

Figure 5. 95% CI of the mean GRF_Z amplitude for the STAT conditions separated by support surface condition (stable, unstable, very unstable). Transtibial prosthesis users (TPU) group: Black lines indicate prosthetic limb and grey lines indicate intact limb. Control (CON) group: Black lines indicate left limb and grey lines indicate right limb. All units in newtons (N).

Figure 6. 95% CI of the anteroposterior CoP integral for the STAT conditions (left – A) and the SWAY conditions (right – B) separated by support surface condition (stable, unstable and very unstable). Transtibial prosthesis users (TPU) group: Black lines indicate prosthetic limb, grey lines indicate intact limb, broken lines indicate middle position (for SWAY conditions (B) only). Control (CON) group: Black lines indicate left limb, grey lines indicate right limb, broken lines indicate middle position (for SWAY conditions (B) only). All units in arbitrary units (a.u.).

Clark S, Riley MA. Multisensory information for postural control: sway-referencing gain shapes center of pressure variability and temporal dynamics. Exp Brain Res. 2007;176:299–310.

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