Dynamic imaging and function of partial supraspinatus tendon tears

Area of Science:

• Orthopedics
• Musculoskeletal imaging
• Biomechanics

Background:

• The supraspinatus tendon is crucial for shoulder function.
• Assessing supraspinatus tendon integrity in vivo is vital for diagnosis and treatment.
• Real-time ultrasound offers a dynamic method for evaluating tendon mechanics.

Purpose of the Study:

• To identify and document normal and abnormal supraspinatus tendon function in vivo using real-time ultrasound.
• To differentiate between healthy, partially torn, fully torn, and repaired supraspinatus tendons based on dynamic ultrasound characteristics.

Main Methods:

• A case-control study involving four groups: partial tear, full-thickness tear, successfully repaired tear, and healthy controls (20 individuals each).
• Diagnosis confirmed by magnetic resonance arthrography (except controls).
• Real-time ultrasound imaging of the supraspinatus tendon at rest and during maximal isometric abduction, measuring tendon thickness changes at specific distances from insertion.

Main Results:

• No significant difference in tendon thickness at rest across groups, with least variation 1.5 cm from insertion.
• During muscle contraction, normal tendons showed significant thickness increase at 2 cm from insertion.
• Tendon deformation was not observed in full-thickness or partial tears upon contraction.

Conclusions:

• Partially torn supraspinatus tendons can be functionally incompetent, presenting biomechanical deformation similar to full-thickness tears.
• Dynamic ultrasound findings after successful supraspinatus tendon repair resemble those of a normal tendon.
• Despite normal dynamic ultrasound, repaired tendons may be associated with reduced muscle strength generation.