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This study reports the application of a novel method for quantitatively determining differences in the mechanical properties of healthy and torn rotator cuff tissues. In order to overcome problems of stress risers at the grip-tendon interface that can obscure mechanical measurements of small tendons, we conducted our investigation using dynamic shear analysis. Rotator cuff tendon specimens were obtained from 100 patients during shoulder surgery. They included 82 differently sized tears and 18 matched controls. We subjected biopsy samples of 3 mm in diameter to oscillatory deformation under compression using dynamic shear analysis. The storage modulus (G') was calculated as an indicator of mechanical integrity. Normal tendons had a significantly higher storage modulus than torn tendons, indicating that torn tendons are mechanically weaker than normal tendons (p = 0.003). Normal tendons had a significantly higher mean shear modulus than tendons with massive tears (p < 0.01). Dynamic shear analysis allows the determination of shear mechanical properties of small tissue specimens obtained intra-operatively that could not be studied by conventional methods of tensile testing. These methods could be employed to investigate other musculoskeletal tissues. This pilot study provides some insight into mechanisms that might contribute to the failure of repair surgery, and with future application could help direct the most appropriate treatment for specific rotator cuff tears.

Original publication

DOI

10.1302/0301-620X.93B7.25741

Type

Journal article

Journal

J Bone Joint Surg Br

Publication Date

07/2011

Volume

93

Pages

942 - 948

Keywords

Adult, Age Factors, Aged, Aged, 80 and over, Case-Control Studies, Formaldehyde, Functional Laterality, Humans, Middle Aged, Rotator Cuff, Rotator Cuff Injuries, Sex Factors, Shear Strength, Tendon Injuries, Tissue Preservation, Young Adult