Reliability of The Butterfly Test - A Clinical Assessment to Quantify Movement Control of the Cervical Spine

Research Objectives: To determine the inter-rater and test-retest reliability of The Butterfly Test, a clinical assessment to quantify movement control of the cervical spine.

Design: Outcome measure reliability study. Subjects performed The Butterfly Test using the NeckCare System (NeckCare, Iceland). Subjects wore a head-mounted movement sensor and attempted to follow a moving target on a computer screen as accurately as possible with a cursor controlled by the sensor. The target moved at an unpredictable velocity along three predetermined trajectories invisible to the subject. Subjects performed the test twice on the same day, instructed by two raters (A and B), then again two days later (with rater B).
Two-way mixed-effects model intraclass correlation coefficient (ICC) for absolute agreement was used to assess inter-rater and test-retest reliability.

Setting: Laboratory setting.

Participants: Thirty-five healthy individuals (21 female, 14 male) aged 21-53 years (39 ± 4.8) were recruited using convenience sampling.

Interventions: Not applicable.

Main Outcome Measures: Movement control parameters reported by The Butterfly Test were: 1) Amplitude Accuracy (AA), the average distance between the target and subject-controlled cursor; 2) Time-on-Target (ToT), the relative time spent on target; 3) Undershoot (US), the relative time spent behind the target; 4) Overshoot (OS), the relative time spent ahead of the target.

Results: Good test-retest reliability and moderate to good inter-rater reliability was demonstrated for AA (0.72-0.84). Test-retest and inter-rater reliability was moderate to good for ToT (0.67-0.87), US (0.69-0.77), and OS (0.79-0.87). No consistent differences in ICCs were observed between the three trajectories.

Conclusions: The Butterfly Test is a reliable clinical tool for assessing movement control of the cervical spine. Reliable objective outcome measures for movement control performance may support clinical decision-making and lead to improved and personalized treatment of cervical spine-related conditions.

Author(s) Disclosures: Dr. Jona Marin Olafsdottir owns shares in NeckCare.