Improving Visual Estimates of Cervical Spine Range of Motion
Cervical spine range of motion (ROM) is a common measure of cervical conditions, surgical outcomes, and functional impairment. Although ROM is routinely assessed by visual estimation in clinical practice, visual estimates have been shown to be unreliable and inaccurate. Reliable goniometers can be used for assessments, but the associated costs and logistics generally limit their clinical acceptance.
To investigate whether training can improve visual estimates of cervical spine ROM, we asked attending surgeons, residents, and medical students at our institution to visually estimate the cervical spine ROM of healthy subjects before and after a training session. This training session included review of normal cervical spine ROM in 3 planes and demonstration of partial and full motion in 3 planes by multiple subjects. Estimates before, immediately after, and 1 month after this training session were compared to assess reliability and accuracy.
Immediately after training, errors decreased by 11.9° (flexion-extension), 3.8° (lateral bending), and 2.9° (axial rotation). These improvements were statistically significant. One month after training, visual estimates remained improved, by 9.5°, 1.6°, and 3.1°, respectively, but were statistically significant only in flexion-extension.
Although the accuracy of visual estimates can be improved, clinicians should be aware of the limitations of visual estimates of cervical spine ROM. Our study results support scrutiny of visual assessment of ROM as a criterion for diagnosing permanent impairment or disability.
Training clearly improved the accuracy of visual estimates of cervical spine ROM. Estimates were statistically improved for all planes immediately after training and remained significantly improved for flexion-extension (the plane of largest error initially) 1 month after training. Before training, mean errors varied across planes. Training normalized mean errors to about 15°, and this effect lasted in flexion-extension, lateral bending, and axial rotation (Figures 4A–4C). Of note, before training these percentage errors increased with increased motion from neutral in the flexion-extension and lateral bending planes. At full ROM, percentage errors in estimates were greater. After training, percentage errors did not increase appreciably with increasing motion.
Readers will naturally reflect on the clinical significance of the motion assessment improvements demonstrated after the training session described in this study. We must be aware that functional assessments are increasingly being emphasized in the clinical arena—with respect to clinical conditions, surgical outcomes, and functional impairments. We highlight a point made earlier: A difference of only 5° can affect impairment ratings in the medicolegal realm.1 In estimating flexion-extension motion, lasting improvements of almost 10° were demonstrated and maintained 1 month after the training session described in this study.
Nevertheless, mean errors in visual estimation remained at about 15° in all planes of motion, despite our modest improvements. This finding raises the question of whether visually estimated ROM should be pertinent to assessments of impairment and disability. Although visual estimates of ROM may have more utility as a screening test for impairment and disability, fine differences in ROM simply cannot be reliably assessed by visual estimation.
This study has limitations. First, it was conducted at a single institution where the evaluators received most of their training. Their skill in visually estimating cervical spine ROM may not be generalizable to a larger population of spine specialists who are practicing at other institutions and may have different training backgrounds.
Second, only healthy subjects were assessed. Some studies of cervical spine ROM have shown better reliability in symptomatic subjects relative to asymptomatic subjects.13,14 To attempt to overcome this limitation, we assessed many different excursions of motion that were often not to the extremes of motion.
Third, the “gold standard” we used for motion assessment was an electrogoniometer, which has some inherent error (previously validated mean [SD] error of 2.3° [2.6°] relative to radiographs8). Although obtaining radiographs of each movement would have more closely resembled the gold standard, the radiation dose associated with such a study is prohibitive.
Last, the assessors included medical students. The medical students’ estimates, however, tended to be more accurate than the residents’ or attending surgeons’ (though the difference was not statistically significant). This tendency may reflect the medical students’ closer attention to detail. Clearly, including medical students in the study did not negatively affect the accuracy of the estimates or the validity of our findings.
Conclusion
Despite its limitations, visual assessment of cervical spine motion remains the gold standard in clinical practice and is routinely recorded and reported. Mean errors ranged from 15.5° to 23.9°, depending on plane of motion being assessed, but these improved after a training session.
Visual estimates of motion in flexion-extension were most improved by training, as the initial errors in this plane were the largest. Statistically significant improvement of about 10° remained for flexion-extension motion estimates 1 month after training.
During a time when we are increasingly emphasizing functional outcomes, such a degree of improvement could be of clinical significance. Our study results support a call for more formalized training of ROM assessment, but clinicians should also be aware of the limitations of visual estimates of cervical spine ROM, and our study results support scrutiny of visual assessment of ROM as a criterion for diagnosing permanent impairment or disability.
