Using Digital Human Modeling (DHM) to Examine Sonographer Upper Extremity Loading

Introduction/ Background

• Sonographers have the highest rate of musculoskeletal injuries within the healthcare sector. These injuries are linked to high force requirements while using the ultrasound probe, sustained loading, and awkward postures during scans. Injuries may be elevated when completing scans on patients who are overweight or obese, as increased adipose tissue affects ultrasound scan quality (and sonographer loading) and patient size affects sonographer posture.
• Project researchers at Brock University collaborated with Occupational Health & Safety staff at Niagara Health to complete this ergonomic assessment.
• Sonographers complete 13 scans a day and work approximately 37 hours a week on average. All sonographers reported that an increase in patient BMI makes scanning more difficult to complete. This BMI complaint was unique and had not been investigated in the literature to date.

Goal

Evaluate differences in the physical demands of sonographers based on patient anthropometrics.

What was Done and How?

• An ergonomic examination using digital human modeling was conducted using computer software called Santos Human Pro (v. 1.5.2021.209). In collaboration with the healthcare system:
  • Virtual environments were created
  • Scan locations selected from our survey based on increased difficulty
• Four scan locations (shoulder, leg, breast, kidney) were completed bilaterally, generating eight scan locations. 18 avatars were created for the scans, representing two sexes, 5th/50th/95th height percentiles, and normal/overweight/obese BMI metrics; resulting in 144 total scans.
• Ergonomic assessments were completed using the Arm Force Field (AFF) tool and the Rapid Upper Limb Assessment (RULA). 

Results of the Changes

AFF population strength capabilities identified low population capability overall across all scans. Patient anthropometrics demonstrated a limited effect on population capability, with lower population capability values only appearing for Left Shoulder scans of obese male patients. For scans that were longer than 15 minutes, a dramatic decrease in AFF population strength capability was observed, particularly in 45-minute scans, where >1% population strength capability was observed in almost all scan scenarios. These findings indicated that limiting scan lengths to 15 minutes per hour warranted strong consideration in preventing musculoskeletal injury risk.

RULA scores depicted moderate to high musculoskeletal injury risk, with scores differing by scan location. Left Kidney, Right Kidney, and Right Shoulder scans averaged >5.75, while scores >4 were observed in Left and Right Leg scans. This demonstrated that changes to the way scans are completed needed to be made in order to decrease the sonographer's risk of injury.

• The use of digital human modeling has substantial flexibility in task assessment and can highlight tasks of interest. Digital human modeling can allow the user to replicate an environment and quickly assess the task to identify task factors that are elevating musculoskeletal injury risk.
• The AFF and RULA are widely used ergonomic assessment tools and can be transferred to multiple work scenarios.
• The creation of individual avatars that replicated patient size created a unique strength for the project. Typically, most DHM platforms allow for environment creation but have little flexibility in changing the physical anthropometrics of the avatar.

The approach and measures described here can be used in a wide array of work tasks and can be transferred to multiple work scenarios. Digital human modelling has substantial flexibility in task assessment and can highlight tasks of interest, environment replication, and quick assessments to determine musculoskeletal injury risk.

Contact: Dr. Michael Holmes
Canada Research Chair, Neuromuscular Mechanics and Ergonomics
Brock University, St. Catharines, Ontario
Email: mholmes2@brocku.ca

Burnett, DR & Campbell-Kyureghyan, NH (2010). International Journal of Industrial Ergonomics, 40(3):306-314. 

McDonald, A et al. (2012). Applied Ergonomics, 43(6):971-978. 

Muir, M et al. (2004). Journal of Diagnostic Medical Sonography, 20(5):317-325.