Friday, October 25, 2013

The anterior rotator cuff cable

The Biomechanical Relevance of Anterior Rotator Cuff Cable Tears in a Cadaveric Shoulder Model

This paper builds on the classical paper of Harryman and Clark, showing that the cuff insertion is not a homogeneous sheath, but rather a complex intersection of many fibers in at least 5 different layers. They also showed that the 'anterior cable' (the anterior 1 cm of the insertion immediately posterior to the biceps tendon) is not just a thickened aspect of the supraspinatus tendon, but also a means by which the supraspinatus inserts around the biceps tendon into the lesser tuberosity, providing special strength and importance to this aspect of the tendon.For that reason a defect in the the anterior aspect of the tendon is of greater consequence than a defect of the tendon behind the anterior aspect of the cable. Here's a figure from the Harryman and Clark article.

These authors used 12  human cadaveric shoulders to compare equivalently sized supraspinatus cuts of either the anterior rotator cuff cable (n = 6) or the adjacent rotator cuff crescent (n = 6). Under loading the gap distance of large cable tears was significantly greater than that of large crescent tears (median gap distance, 1.3 mm) (p = 0.002), a finding that supports the importance of the anterior cable.

Comment: This is an excellent anatomical/biomechanical study. The authors' statement of the clinical relevance may not, however, necessarily follow: "Clinicians should consider early repair of rotator cuff cable tears, which may need surgical intervention to address their biomechanical pathology. In contrast, surgical treatment may be more safely delayed for rotator cuff crescent tears." It is unclear whether the repair of an acute tendon tear of the crescent should be delayed, just as it is unclear that the repair of a failed anterior cable should be rushed if conditions are not favorable for a durable repair.

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