Assessment and characterization of in situ rotator cuff biomechanics

Abstract

Rotator cuff disease is a degenerative disorder that is a common, costly, and often debilitating, ranging in severity from partial thickness tear, which may cause pain, to total rupture, leading to loss in function. In current clinical practice, treatment decisions are frequently made through subjective assessment of pain and range of motion combined with qualitative assessment of x-ray images, magnetic resonance images (MRI), or ultrasound images. Treatment of disease may include physical therapy, surgery, or a combination of both. Often, the final determination of the best course of action is at the discretion of the clinician, and is based on personal experience as opposed to quantitative standards. v ACKNOWLEDGEMENTS I would first like to acknowledge my advisor, Dr. David Kwartowitz for providing assistance and direction throughout my graduate research. I would also like to thank my committee members Dr. Delphine Dean and Dr. Melinda Harman for their insight and guidance.

Mechanisms of Shoulder Range of Motion Deficits in Asymptomatic Baseball Players

“…Our results are based on the assessment of compressive muscle stiffness as opposed to linear muscle stiffness. While this may limit our full understanding of the muscle's influence on shoulder ROM, our technique was validated against known ex vivo elastomer ploymers 45 and is consistent with similar methods reported by Van Loocke et al 49,50 Furthermore, previous work involving recently deceased cadaveric specimens has confirmed that ultrasound measurement of compressive muscle stiffness is valid and positively correlated with linear muscle stiffness mechanics. 48 At this time, we are unaware of any existing studies that demonstrate the influence of linear rotator cuff stiffness on shoulder ROM in vivo.…”

“…45 This relationship was computed given a known transducer size (A) and the measurement of the applied force through the ultrasound transducer. The resting length (L 0 ) and change in length (DL) were measured from the resulting ultrasound images and were expressed in kilopascals (kPA).…”

“…48 This method has been validated against the known stiffness of polyvinyl alcohol cryogel phantom moduli and cadaveric specimens. 45 Specifically, bilateral infraspinatus stiffness was measured in the prone position, with the testing arm placed in 90°of shoulder abduction and 90°of elbow flexion. The probe was positioned within the long axis of the infraspinatus muscle at the spinoglenoid notch (Figure 2A).…”

“…Stress (s) was calculated as an applied force (F) over a surface area (A), while strain (e) was the change in the tissue length (DL) from the original resting length (L 0 ). 45 This relationship was computed given a known transducer size (A) and the measurement of the applied force through the ultrasound transducer. The resting length (L 0 ) and change in length (DL) were measured from the resulting ultrasound images and were expressed in kilopascals (kPA).…”