University of Southern California
University of Southern California
USC Chan Division of Occupational Science and Occupational Therapy
USC Chan Division of Occupational Science and Occupational Therapy

Musculoskeletal Sonography and Occupational Performance Laboratory

Active Research

Early Identification of Median Nerve Pathology

Compression of the median nerve (asterisks) while holding a dental scaling instrument

Compression of the median nerve (asterisks) while holding a dental scaling instrument

Nearly 70% of dental hygienists report experiencing discomfort in their forearms/wrists/hands, primarily due to the use of dental scaling instruments. Dental scaling requires sustained pinching and repetitive movements that place high load on the forearm and hand muscles. This high muscle load, combined with pinching and non-neutral wrist positions, approximately doubles the risk of developing hand and median nerve pathology due to strain on the tendons and compression of the median nerve.  Scaling of more than four hours per day has been directly associated with pathology.

Dental hygiene students have an elevated risk of musculoskeletal injury due to intensive exposure to scaling during their educational training. We have documented a significant increase in subjective reports of discomfort in the hand, wrist, and fingers of these students, with the prevalence of students with discomfort doubling to tripling across their two-year training program. Up to 60% of individuals report having discomfort at the end of their training. To enhance education, develop preventive training, and address work-related musculoskeletal disorders in dental hygienists, it is necessary to better understand the link between exposure and pathology development.

Our interdisciplinary team is attempting to advance this goal with funding from the National Institute for Occupational Safety and Health (NIOSH).  We are specifically interested in the use of sonographic imaging to identify factors that may predispose individuals to injury and to monitor changes in tissues in response to exposure to scaling activities, as well as evaluating the relative contribution of body postures and strain related to dental scaling tasks themselves.  Using these data we aim to develop and validate a novel method for early detection of median nerve pathology and determine the effects of task components on changes in morphology.

Dr. Roll evaluating the carpal tunnel with sonographic imaging

Dr. Roll evaluating the carpal tunnel with sonographic imaging

This study is following dental hygiene students throughout their two-year educational training, obtaining measures each semester.  First, we are using sonographic imaging to monitor changes in tissue morphology of the distal upper extremity. Sonographic imaging has been used in an animal model to observe early progressive increases in median nerve size due to task exposure. By understanding this progression in humans, it would be possible to develop an early detection technique to stop, slow, or reverse pathology before it becomes costly and debilitating.

Nerve Conduction

These sonographic measures are being compared to neurophysiological changes using nerve conduction testing, subjective reports of symptoms and functional limitations using questionnaires, and task exposures during scaling using video analyses. This work will establish predictive validity of a novel method for early detection of work-related pathology using sonographic imaging, while also identifying task components of intensive functional hand activity (e.g., scaling) associated with morphologic changes.

Intermediate outcomes of this research will establish sonographic imaging as an early detection tool for workplace-screening and inform methods for combining measures of nerve morphology, neurophysiology, and subjective symptoms for predicting the development of work-related injuries. This work will also inform the development of targeted preventive interventions for task components of intensive hand activities that are related to changes in tissue morphology. Identifying morphologic changes in early-stages of pathology and the specific task components linked to these changes are the first steps toward early detection and prevention of work-related musculoskeletal injuries in dental hygienists.

Funding

Sonographic tissue morphology in early stage work-related pathology
National Institute for Occupational Safety and Health / Centers for Disease Control
R01-OH010665 (PI: Roll)
Total Funding: $2,324,186
Funding Period: 9/30/15 – 9/29/19

Association of nerve movement during functional hand use to pathology development in dental hygienists
USC Office of Undergraduate Programs – Undergraduate Research Associates Program
Total Funding: $6,000
Funding Period: 8/15/18 – 5/15/19

Publications

Yao, B., Gan, K., Lee, A., & Roll, S. C. (2020). Comparing shape categorization to circularity measurement in the evaluation of median nerve compression using sonography. Journal of Diagnostic Medical Sonography, 36(3), 224-232. https://doi.org/10.1177/8756479319898471 Show abstract

Takata, S. C., Kysh, L., Mack, W. J., & Roll, S. C. (2019). Sonographic reference values of median nerve cross-sectional area: A protocol for a systematic review and meta-analysis. Systematic Reviews, 8(1), 2. https://doi.org/10.1186/s13643-018-0929-9 Show abstract

Takata, S. C., & Roll, S. C. (2019). Identification of aberrant muscle bellies in the carpal tunnel using sonography. Journal of Diagnostic Medical Sonography, 35(1), 62–68. https://doi.org/10.1177/8756479318807469 Show abstract

Roll, S. C., Evans, K. D., Volz, K. R., & Sommerich, C. M. (2013). Longitudinal design for sonographic measurement of median nerve swelling with controlled exposure to physical work using an animal model. Ultrasound in Medicine & Biology, 39(12), 2492-2497. https://doi.org/10.1016/j.ultrasmedbio.2013.08.008 Show abstract

Presentations

Yao B, Gan H, Lee A, Roll SC. Dynamic evaluation of median nerve shape in the carpal tunnel. Poster presentation at: USC Ostrow School of Dentistry Research Day, 2019; Los Angeles, CA.

Takata SC, Roll SC.  Sonographic prevalence of space-occupying long flexor muscle bellies in the carpal tunnel of healthy individuals.  Paper presentation at: American Institute of Ultrasound in Medicine Annual Conference, 2019; Orlando, FL.

Roll SC, Forrest JL, Mack WJ.  Differential effects of work-related task training on upper extremity health in occupational therapy and dental hygiene students. Poster presentation at:  97th Annual Conference of the American Occupational Therapy Association, 2019; New Orleans, LA

Roll SC, Takata SC. Illuminating the nuances of carpal tunnel syndrome: Advanced concepts in prevention and rehabilitation for the experienced therapist. Short course presentation at: American Society of Hand Therapists Annual Conference, 2018; Dallas, TX.

Takata, S. C., & Roll, S. C. (2017). Relationship of internal carpal tunnel measurements to external wrist-ratio: Implications for prevention of carpal tunnel syndrome. Paper presentation at 6th Annual Occupational Therapy Summit of Scholars, Boston, MA.

Melrose, M. D., Wilkins, K., Forrest, J. L., & Roll, S. C. (2017). Identifying risk of hand injuries in dental hygienists: A longitudinal cohort study. Poster presentation at American Dental Educators Association Allied Program Directors’ Conference, Baltimore, MD.

Roll, S. C., & Mitchell, J. (2017). Relationship of internal carpal tunnel measurements to external wrist-ratio: Implications for prevention and diagnosis. Paper presentation at Annual Convention of the American Institute of Ultrasound in Medicine, Orlando, FL.

Roll, S. C., Mack, W. J., & Forrest, J. L. (2017). Identification of early-stage median nerve pathology: Longitudinal multiple cohort study protocol. Electronic poster at Annual Convention of the American Institute of Ultrasound in Medicine, Orlando, FL.

Roll, S. C., Mack, W. J., Forrest, J. L., Baker, L. L., & Baker, N. A. (2016). Identification of early-stage median nerve pathology: Protocol for a longitudinal, multiple cohort study. Paper presentation at 5th Annual Occupational Therapy Summit of Scholars, Pittsburgh, PA.