BACKGROUNDPlantar sensory input is a crucial component of proprioceptive system, which is important for maintaining balance and gait control. Foot orthoses are traditionally prescribed to correct/compensate foot deformity and relieve foot pain in patients. Adding some electronic components at insoles to capture the plantar force information and providing corresponding feedback information could compensate sensory loss in patients and amputees [1-3], this may further be applied to help improve lower limb motor control.AIMTo investigate the effect of instant biofeedback of plantar pressure distribution at medial and lateral forefoot on alteration of foot inversion and push-off forces during stance phrase in patients with hemiplegic stroke.METHODThis study was conducted in a university locomotion laboratory. Convenience sampling approach was adopted to recruit 8 patients with hemiplegic stroke (7M+1F, age 54±10 years, height 175±6 cm, weight 72±11 kg) in this study. All participants walked with visible foot inversion and seven of them walked with visible foot plantarflexion in swing phrase. The foot inversion and plantarflexion deformities were flexible and can be corrected by external forces.A vibrotactile biofeedback system was developed and evaluated, which integrated two force sensors at plantar surface of foot in a pair of flat insoles measuring the plantar forces at medial and lateral forefoot, and wirelessly sent instant control signals to one vibrator at wrist when the magnitude of detected plantar force at medial-side forefoot was lower than 50% of the lateral-side’s.A three-dimensional motion capture system (3D) motion capture system (Vicon Nexus 1.8.1, Vicon NexusTM, Vicon Motion Systems Ltd., UK) and an in-shoe plantar pressure measurement system (novel pedar-x system, PedarTM, novel GmbH, Munich, DE) were used to measure each subject’s spatial-temporal gait parameters and plantar pressure distribution during walking in each of the two experimental conditions with randomized sequences: 1) with biofeedback system turned-off, and 2) with biofeedback system turned-on.RESULTSUpon turning on the biofeedback system, the medial-side plantar pressure at both forefoot and midfoot of the affected limb increased significantly and became close to that of the sound limb, while the plantar pressure at rearfoot and lateral-side midfoot of the affected limb decreased significantly in subjects (Figure 1, p<0.05). The subjects adjusted their gait pattern by significantly decreasing the foot external rotation and hip flexion, and increasing the pelvic backward rotation of both limbs during stance phrase (p<0.05). Although no significant difference was found, subject’s affected limb also revealed notable reduction of foot inversion in stance phrase and increase of plantar-flexion in terminal stance phrase during walking upon using the device.

DISCUSSION & CONCLUSIONInstant vibrotactile biofeedback of plantar pressure distribution at medial and lateral forefoot helps relieve the foot inversion, facilitate initiation of swing phrase, and additionally increase weight-bearing symmetry in stance phrase during walking in patients with stroke. The positive results of this study shed new lights on future research of wearable plantar force-based biofeedback system for improving gait in people with impaired lower-limb motor control. It further allows the targeted gait training and improvement of motor control to be conducted in both indoor and outdoor environments.