Muscle biopsies from the supraspinatus in retracted rotator cuff tears respond normally to passive mechanical testing: a pilot study.

Purpose: The aim of the present study was to assess the function of the isolated muscle component in retracted rotator cuff tears.

Methods: Muscle biopsies were harvested from the supraspinatus and the ipsilateral deltoid in seven patients undergoing surgery for a large, retracted rotator cuff tear. Single fibres and fibre bundles were subjected to passive stretching in vitro with subsequent recordings of tension and sarcomere lengths using the laser diffraction technique.

Passive mechanical features of single fibers from human muscle biopsies--effects of storage.

Background: The purpose of this study was to investigate the effect of storage of human muscle biopsies on passive mechanical properties.

Methods: Stress-strain analysis accompanied by laser diffraction assisted sarcomere length measurement was performed on single muscle fibres from fresh samples and compared with single fibres from stored samples (-20 degrees C, 4 weeks) with the same origin as the corresponding fresh sample. Basic morphological analysis, including cross sectional area (CSA) measurement, fibre diameter measurement, fibre occupancy calculation and overall morphology evaluation was done.

Inferior mechanical properties of spastic muscle bundles due to hypertrophic but compromised extracellular matrix material.

The passive mechanical properties of small muscle fiber bundles obtained from surgical patients with spasticity (n = 9) and patients without neuromuscular disorders (n = 21) were measured in order to determine the relative influence of intracellular and extracellular components. For both types of patient, tangent modulus was significantly greater in bundles compared to identical tests performed on isolated single cells (P < 0.05).