Bursal-Side Partial-Thickness Rotator Cuff Tears
Bursal-side rotator cuff tears are a common source of shoulder pain and disability. The complex microanatomy and load distribution may contribute to their development. Symptoms and physical exam are similar to other rotator cuff syndromes. MRI is usually
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Kevin Shea and Colin Pavano
17.1 Introduction
17.2 Anatomy and Pathomechanics
Partial-thickness tears of the rotator cuff, in particular, the supraspinatus, are a common finding in patients with symptomatic rotator cuff disease. Codman [1] was the first to describe these tears and termed the articular-side tears “rim rents.” He documented some degree of rotator cuff tearing, primarily in the supraspinatus tendon, in up to 20% of autopsy specimens studied. Recognition of the spectrum of partial-thickness tears grew with the routine use of arthroscopy to perform surgical procedures in the shoulder. Ellman [2], Snyder [3], Esch [4], and others described various partial tears, bursal, articular, and interstitial. While partial articular-side rotator cuff tears (PASTA lesions) have received the most attention in the literature, bursal-side tears are also frequent sources of shoulder pain requiring treatment. This chapter will outline the anatomy, pathomechanics, and current treatment of these types of partial rotator cuff tears.
In order to understand partial rotator cuff tears, it is first important to understand the microanatomy of the rotator cuff tendon, and in particular, the supraspinatus tendon. In general, most tendons, e.g., the patellar tendon, are formed by rows of parallel collagen fibers, all aligned in the direction of the applied force. Histologic sections usually show parallel fiber orientation that is the same regardless of the area of tendon examined. In contrast, the fiber arrangement of the supraspinatus tendon is multiplanar, reflecting the complex loading of the rotator cuff. Clarke and Harryman [5] showed that the supraspinatus tendon is actually composed of five distinct layers, each with its own distinct arrangement of collagen fibers, as is shown in Fig. 17.1. Layers 2 and 3 are the thickest and likely carry most of the applied load. Fibers in layer 2 are oriented in the classic alignment, parallel to the line of applied supraspinatus muscle force generation, but the fibers of layer 3 are smaller and more loosely packed and lack specific orientation, reflecting more complex loading, likely in the transverse (anterior-posterior) axis. Differential movement between these load-bearing soft-tissue planes, in particular between layers 2 and 3, creates the potential shear failure between these layers. Fukuda [6] published a series of histologic whole block specimens from 66 operated partial-thickness tears. These sections of bursal-side
K. Shea (*) · C. Pavano Department of Orthopaedic Surgery, University of Connecticut, Farmington, CT, USA e-mail: [email protected]; [email protected]
© ISAKOS 2019 A. B. Imhoff, F. H. Savoie III (eds.), Rotator Cuff Across the Life Span, https://doi.org/10.1007/978-3-662-58729-4_17
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K. Shea and C. Pavano
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a
b
Fig. 17.1 (a) illustrates the multilayer organization of the rotator cuff tendon. Layers 2 and 3 are thought to transmit most of the load between the muscle and bone. Partial-thickness tears delaminate in the plane in between these layers. (
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