TABLE 1.

Study characteristics for publications utilizing nonimmersive VR/AR systems

AUTHOR (YEAR) STUDY DESIGN PEDro SCALE/MINORS SCORE	SAMPLE (N) TYPE OF INJURY MEAN AGE IN YEARS (SD)	VR VS. AR	VR/AR MODALITY	SESSIONS: NUMBER/DURATION; TREATMENT PERIOD DURATION; FOLLOW-UP	OUTCOME MEASURES	PRIMARY FINDINGS
Mercier and Sirigu (2009) Case series MINORS: 13	n=8 2 ULA 6 BPA 37.1 (11.3)	VR	Mirrored virtual limb: participants used the virtual limbs to match target movements on a computer screen.	Session: 16/30–60 min; Treatment: 8 wk; Follow-up: 4 wk	VAS	1) Significant average 38% reduction in pre- to posttreatment PLP intensity at end of study (p=0.02) and 4-week follow-up (p=0.03). 2) No significant difference in PLP intensity between the end of treatment and 4-week follow-up (p=0.44).
Perry et al (2013) Case series MINORS: 10	n=7 7 ULA range: 20–33	VR	Surface EMGs: participants were given a “free-play” period to move and visualize their virtual limbs.	Session: 20/30 min; Treatment: 4 wk	SF-MPQ, VAS	1) 3/5 participants reported decrease in “average daily” PLP. 2) 4/5 participants reported decrease in “worst daily” PLP.
Ortiz-Catalan et al (2014) Case report MINORS: 9	n=1 1 ULA 72	AR	Surface EMGs: participants used their virtual limbs, controlled by EMG signals, to interact with a car racing game or match target limb postures.	Session: 23/20 min; Treatment: 4.5 mo	SF-MPQ, VAS	1) Sustained levels of pain initially reported by participants was gradually reduced to complete pain-free periods. 2) Phantom posture initially reported as a strongly closed fist was gradually relaxed over treatment sessions and an improved telescopic effect.
Perry et al (2018) Case series MINORS: 11	n=8 8 ULA range: 20–30	VR	Surface EMGs: participants were given a “free-play” period to move and visualize their virtual limbs.	Session: 20/30 min	SF-MPQ, VAS	1) Significantly improvement in “worst PLP” (B=–0.474, p=0.015). 2) Significant improvement in “current PLP” (B=–0.248, p=0.042). 3) Nonsignificant improvement in “average PLP” (B =–0.248, p=0.078). 4) Significant improvement in SF-MPQ scores (B =–0.096, p=0.003)
Ortiz-Catalan et al (2016) Case series MINORS: 13	n=14 14 ULA 50.3 (13.9)	AR/VR	Surface EMGs: participants used their virtual limbs to interact with a car racing game or match target limb postures.	Session: 12/2 hr; Treatment: average 6.4 wk; Follow-up: 1, 3, and 6 mo	NRS, PRI, SF-MPQ, WPDS	1) Significant 47% decrease in PLP via WPDS (SD: 39; absolute mean change: 1.0 [0.8]; p=0.001). 2) Significant 32% decrease in PLP via NRS (SD: 38; absolute mean change: 1.6 [1.8]; p=0.007). 3) Significant 51% decrease in PLP via PRI (SD: 33; absolute mean change: 9.6 [8.1]; p=0.0001). 4) Average improvements measured by the PRI at the last session decreased by 2%, 6%, and 24% at 1-, 3-, and 6-month follow-up, respectively. 5) Significant reduction in NRS for intrusion of PLP in activities of daily living and sleep by 43% (SD: 37; absolute mean change: 2.4 [2.3]; p=0.004) and 61% (SD: 39; absolute mean change: 2.3 [1.8]; p=0.001), respectively.
Yanagisawa et al (2020) RCxT PEDro Scale: 8	n=12 2 ULA 10 BPA 48.0 (8.05)	VR	Brain computer interface: participants were divided into experimental and control groups and instructed to visualize opening and closing their phantom limbs. The virtual hand displayed to the participant was controlled by MEG signals in the experimental group and a randomizing algorithm in the control group.	Session: 24/10min; Treatment: 3 days; Follow-up: 5 days	SF-MPQ, VAS	1) No significant difference between baseline SF-MPQ scores for the experimental and control groups (p=0.88). 2) Significant difference between baseline VAS scores for the 2 groups (p=0.0005) because participants were not allocated based on the pain scales. 3) After 3 days, there was a significant decrease in PLP via VAS from baseline in the experimental group (mean [SD]: 45.3 [24.2]–30.9 [20.6], 1/100mm; p=0.009), but not after random training (mean[SD]: 36.6 [19.5]–36.7 [25.0], p=0.98).
Rothgangel et al (2018) RCT PEDro Sclae: 8	n=75 75 LLA 61.1 (14.1)	AR	Teletreatment: Participants were divided into teletreatment, mirror therapy, and control groups. Teletreatment and mirror therapy groups received 4 weeks of mirror therapy, while the control group received 4 weeks of sensorimotor exercises. Mirror therapy and control groups then continued their interventions for 6 weeks, while the teletreatment group used a tablet-delivered virtual limb system for 6 weeks.	Session: 10/30 min; Treatment: 4 wk; Continued sessions: variable/30 min; Continued treatment: 6 wk; Follow-up: 10 wk, 6 mo	NRS, NPS, PSFS, VAS, EuroQool Questionnaire, GPES, Pain Self-Efficacy Questionnaire	1) No significant treatment effect of mirror therapy in control group on average intensity of PLP at 4 weeks (treatment effect: –1.2; 95% CI: –2.4–0.0; p=0.054). 2) All three groups showed a reduction in the average intensity of PLP at 10 weeks and 6-month follow-up, with no statistically significant differences between the groups. 3) Self-directed mirror therapy showed significantly reduced duration of PLP at 6 months, compared to either teletreatment with AR (p=0.050) or control (p=0.019).

VR: virtual reality; AR: augmented reality; PEDro: Physiotherapy Evidence Database; MINORS: Methodological Index for Non-randomized Studies; SD: standard deviation; RCT: randomized controlled trial; RCxT: randomized crossover trial; ULA: upper limb amputation; LLA: lower limb amputation; BPA: brachial plexus avulsion; EMG: electromyography; MEG: magnetoencephalography; mo: month(s); wk: week(s); hr: hour(s); min: minute(s); VAS: visual analogue scale; SF-MPQ: short-form McGill Pain Questionnaire; NRS: numerical rating scale; PRI: pain rating index; WPDS: weighted pain distribution scale; GPES: global perceived effect scale; PSFS: patient-specific functional scale; PLP: phantom limb pain; CI: confidence interval