Altered postural timing and abnormally low use of proprioception in lumbar spinal stenosis pre- and post- surgical decompression

Table 2 Posturography

	Patients N = 11	Patients post-surgery N = 9	Control subjects N = 15	P
	Mean (SE)	Δ (%)	Mean (SE)	P
Spontaneous sway
RMS (cm)	0.56 (0.02)		0.43 (0.01)	< 0.000*
RMS (cm)		−5.3		0.029*
MV (cm/sec)	0.72 (0.04)		0.52 (0.03)	0.002*
MV (cm/sec)		−6.4		0.244
CF (Hz)	0.50 (0.50)		0.44 (0.01)	0.001*
CF (Hz)		4.6		0.071
Perturbed stance
Mean GAIN	1.85 (0.02)		1.93 (0.02)	0.015*
Mean GAIN		1.2		0.482
Mean PHASE (°)	−98.83 (2.22)		−119.09 (1.90)	< 0.000*
Mean PHASE (°)		15.3		< 0.000*
Model parameters
Ki (s ⁻¹·rad^− 1)	74.95 (2.63)		74.85 (2.25)	0.979
Ki (s ⁻¹·rad^− 1)		5.2		0.407
Kp (rad⁻¹)	1093.64 (39.11)		1047.63 (33.49)	0.374
Kp (rad⁻¹)		0.0		0.994
Kd (s·rad⁻¹)	307.39 (8.61)		285.62 (7.37)	0.058
Kd (s·rad⁻¹)		−4.3		0.206
Wp (%)	61.04 (2.59)		68.81 (2.22)	0.025*
Wp (%)		3.1		0.595
Td (msec)	172 (6.1)		172 (5.3)	0.919
Td (msec)		−5.0		0.344
Ppas (rad⁻¹)	82.25 (3.37)		82.88 (2.88)	0.888
Ppas (rad⁻¹)		−9.0		0.490
Dpas (s·rad⁻¹)	55.93 (1.42)		57.09 (1.21)	0.533
Dpas (s·rad⁻¹)		6.3		0.296

*indicates a significant difference p < 0.05
Δ post-surgery minus pre-surgery, SE standard error, RMS root means square, MV mean velocity, CF center frequency, Ki integral gain of the Neural Controller, Kp proportional gain (stiffness factor), Kd derivative gain (damping factor), Wp proprioceptive sensory weight, Td feedback time delay, Ppas passive stiffness factor, Dpas passive damping factor

ISSN: 1471-2474