Comparison of the immobilizing effect of soft, semi-rigid and rigid neck orthoses

Cervical orthoses are widely used in the management of cervical spine (c-spine) injuries, serving to limit motion, alleviate pain, and enhance patient security. While extensive research has examined soft and rigid cervical braces, data on semi-rigid braces, such as the PDC collar, remain scarce. This study aims to compare the immobilizing effects of a semi-rigid cervical orthosis to those of a soft and a rigid orthosis on c-spine mobility in healthy individuals.

In a prospective study, 20 healthy participants (mean age 28.0 ± 6.0 years) underwent motion analysis using a 3D camera system under four conditions: without an orthosis and while wearing a soft, semi-rigid, and rigid orthosis. Maximum cervical range of motion (ROM) was measured during flexion/extension, lateral flexion, and axial rotation. The maximum active ROM was determined for each orthosis. After testing for normal distribution (Shapiro-Wilk test), repeated measures ANOVA with post-hoc Bonferroni-corrected t-tests was used for pairwise comparison of absolute ROM across orthoses.

All orthoses significantly restricted ROM compared to the unrestricted state (p < 0.01). Flexion/extension was the most restricted movement across all orthoses. The rigid orthosis provided the greatest restriction in all three movement directions, significantly reducing flexion/extension to 27.5° from an unrestricted ROM of 107.3° (p < 0.01). It also restricted rotation and lateral flexion significantly more than the semi-rigid and soft orthoses (p < 0.01). The semi-rigid orthosis significantly reduced flexion/extension compared to the soft collar (39.1° vs. 48.1°, p < 0.01), while no significant differences were observed between the two in rotation or lateral flexion.

The semi-rigid orthosis effectively limits c-spine mobility, particularly in flexion/extension, offering an intermediate option between soft and rigid braces. Its use may balance immobilization needs and patient comfort in cases requiring moderate motion restriction without increased complication risks.