Assessing range of motion to evaluate the adverse effects of ill-fitting cervical orthoses

Although previous studies have primarily focused on testing the effectiveness of cervical orthoses under properly fit conditions, this study focuses on analyzing the effects of an ill-fitted cervical orthosis (Miami J). This may have significance to health-care providers in understanding the effects of an improperly fitted neck brace.

The aims of this study were threefold: first, to apply virtual reality (VR) feedback control to repeatedly measure orthoses effectiveness in the primary motions; second, to use this control methodology to test the orthoses ability to restrict flexion/extension (FE) as a function of axial rotation (AR); third, to test the effects of an ill-fitting Miami J on cervical motion.

This study combines six degrees of freedom electromagnetic trackers and VR feedback to analyze the effectiveness of common cervical orthoses under less than optimal conditions.

Twelve healthy male subjects aged 21 to 35 (mean 29.44 years, SD 6.598) years with no previous spinal cord injuries or current neck pain participated in the study.

Cervical range of motion (CRoM) measurements were used to determine the amount of motion restriction for each of the fitted (too small, correct size, and too big) Miami J orthoses.

One Nest of Birds (NOB) electromagnetic sensor (Ascension Technology) was placed on the head and another on the upper back to measure motion of the head relative to the torso. The VR goggles (i-O Display Systems) were worn so that real-time feedback was available to the subject for motion control. The subject executed the primary motions of FE, AR, and lateral bending (LB) in separate sets of five trials each. Next, in combined motion, the subject axially rotated to a set point and then FE to his maximums. This entire set of motions was repeated for each (soft collar, Miami J, Miami J with chest extension, Sternal Occipital Mandibular Immobilizer (AliMed, Inc.), (SOMI and Halo) as well as the Miami J (one size too small and one size too big); the fitting of each brace was done by a board certified orthotist. A repeated measures analysis of variance was used to determine differences between the tested states (*p=.05).

For the validation test, the primary motions recorded for subjects wearing each cervical brace, which demonstrated that the various orthoses all restricted CRoM. The soft collar restricted less motion than the other devices, whereas the Halo restricted the most motion throughout. For the ill-fitting cervical collar comparison, motion in the correct size collar was normalized to 1.0, and the correct size allowed less motion than either the too big or too small braces. In FE, the too big brace tended to allow more motion than the too small, but only the too big brace in extension was significantly different from the correct size. In AR, the too small brace seemed to allow more motion than the too big. Both the too big and too small braces were significantly different than the correct size in both left and right AR. In LB, the too big brace and too small brace were very similar in the amount of motion they were able to restrict. Both braces were significantly different than the correct size in right LB, whereas only the too small brace was significantly different from the correct size in left LB. In the combined motion data, both the too big and too small braces allowed more motion than the correct size. The too small brace seemed to allow more FE at all degrees of AR except for extreme right AR.

To our knowledge, the effects of improperly fitted cervical orthoses on CRoM are still unknown. Using the NOB electromagnetic tracking system combined with VR feedback, we were able to consider the motion restriction of ill-fitting Miami J orthoses for both primary and combined motions. For both motion types, increased motion was possible when the subject was improperly fitted with the Miami J. If not considered, these excessive motions could potentially have detrimental effects on patient satisfaction, clinical outcomes, or even lead to increased secondary injury.