Effect of a mixed reality-based intervention on arm, hand, and finger function on chronic stroke

Abstract

Background: Virtual and mixed reality systems have been suggested to promote motor recovery after stroke. Basing on the existing evidence on motor learning, we have developed a portable and low-cost mixed reality tabletop system that transforms a conventional table in a virtual environment for upper limb rehabilitation. The system allows intensive and customized training of a wide range of arm, hand, and finger movements and enables interaction with tangible objects, while providing audiovisual feedback of the participants' performance in gamified tasks. This study evaluates the clinical effectiveness and the acceptance of an experimental intervention with the system in chronic stroke survivors.

Methods: Thirty individuals with stroke were included in a reversal (A-B-A) study. Phase A consisted of 30 sessions of conventional physical therapy. Phase B consisted of 30 training sessions with the experimental system. Both interventions involved flexion and extension of the elbow, wrist, and fingers, and grasping of different objects. Sessions were 45-min long and were administered three to five days a week. The body structures (Modified Ashworth Scale), functions (Motricity Index, Fugl-Meyer Assessment Scale), activities (Manual Function Test, Wolf Motor Function Test, Box and Blocks Test, Nine Hole Peg Test), and participation (Motor Activity Log) were assessed before and after each phase. Acceptance of the system was also assessed after phase B (System Usability Scale, Intrinsic Motivation Inventory).

Results: Significant improvement was detected after the intervention with the system in the activity, both in arm function measured by the Wolf Motor Function Test (p < 0.01) and finger dexterity measured by the Box and Blocks Test (p < 0.01) and the Nine Hole Peg Test (p < 0.01); and participation (p < 0.01), which was maintained to the end of the study. The experimental system was reported as highly usable, enjoyable, and motivating.

Conclusions: Our results support the clinical effectiveness of mixed reality interventions that satisfy the motor learning principles for upper limb rehabilitation in chronic stroke survivors. This characteristic, together with the low cost of the system, its portability, and its acceptance could promote the integration of these systems in the clinical practice as an alternative to more expensive systems, such as robotic instruments.

Keywords: Augmented reality; Hemiparesis; Physical therapy; Stroke; Tabletop systems; Upper limb; Virtual reality.

Fig. 1

Prototype of the virtual reality-based system. The hardware used in this experiment consisted of: a) a Kinect™ (Microsoft®, Redmond, WA, USA), which estimated the depth information of the scene, and a LCD projector EB-1720 (EPSON, Suwa, NGN, Japan), which projected the VR; b) a conventional table; and c) a computer Vostro 420 (Dell Inc., Round Rock, TX, USA) equipped with a QuadCore @ 2.83 GHz and 4 GB of RAM, which generated the VE, tracked the movements of the user on the area of interest, and modified the VE according to them

Fig. 2

Participant training with the system. A participant interacts with the system using a tangible object. Participant must grate a carrot, represented on the top surface of the item, on a salad. The task is achieved through repeated flexion-extension of the wrist, while maintaining the forearm on the table and the elbow still

Fig. 3

Description of the exercises. The exercises covered a wide range of hand and arm movements, mostly focusing on the flexion and extension of the elbow and the wrist. a Exercise: to sweep the crumbs from the table. Movement: flexion-extension of the wrist without involving the fingers. b Exercise: to grate. Movement: Grasping and flexion-extension of the wrist. c Exercise: to knock on doors. Movement: flexion-extension of the wrist against gravity. d Exercise: to cook. Movement: grasping involving flexion-extension of the elbow and rotation of the shoulders. e Exercise: to squeeze a sponge. Movement: flexion-extension of the metacarpophalangeal-interphalangeal joint. f Exercise: to dial a number. Movement: tapping. g Exercise: to play piano. Movement: flexion-extension of the thumb, index, and middle finger. h Exercise: to buy items. Movement: pincer grasping with the thumb and index involving flexion-extension of the elbow and rotation of the shoulders

Fig. 4

Statistically significant effects throughout the intervention. Significant improvement was detected after the experimental intervention (from B_i to B_f) but not after the following conventional intervention (from B_f to A_f) nor the previous (from A_i to B_i), but in the Amount of Use subscale of the Motor Activity Log. WMFT: Wolf Motor Function Test; BBT: Box and Blocks Test; NHPT: Nine Hole Peg Test; MAL-QOM: Quality of Movement subscale of the Motor Activity Log; MAL-AOU: Amount of Use subscale of the Motor Activity Log. *: p < 0.05; **: p < 0.01