The morphology of the subacromial and related shoulder bursae. An anatomical and histological study.

Shoulder bursae are essential for normal movement and are also implicated in the pathogenesis of shoulder pain and dysfunction. The subacromial bursa (SAB), within the subacromial space, is considered a primary source of shoulder pain. Several other bursae related to the subcoracoid space, including the coracobrachial (CBB), subcoracoid (SCB) and subtendinous bursa of subscapularis (SSB), are also clinically relevant. The detailed morphology and histological characteristics of these bursae are not well described. Sixteen embalmed cadaveric shoulders from eight individuals (five females, three males; mean age 78.6 ± 7.9 years) were investigated using macro-dissection and histological techniques to describe the locations, dimensions and attachments of the bursae, their relationship to surrounding structures and neurovascular supply. Bursal sections were stained with haematoxylin and eosin to examine the synovium and with antibodies against von Willebrand factor and neurofilament to identify blood vessels and neural structures respectively. Four separate bursae were related to the subacromial and subcoracoid spaces. The SAB was large, with a confluent subdeltoid portion in all except one specimen, which displayed a distinct subdeltoid bursa. The SAB roof attached to the lateral edge and deep surface of the acromion and coracoacromial ligament, and the subdeltoid fascia; its floor fused with the supraspinatus tendon and greater tubercle. The CBB (15/16 specimens) was deep to the conjoint tendon of coracobrachialis and short head of biceps brachii and the tip of the coracoid process, while the inconstant SCB (5/16 specimens) was deep to the coracoid process. Located deep to the subscapularis tendon, the SSB was a constant entity that commonly displayed a superior extension. Synovial tissue was predominantly areolar (SAB and SSB) or fibrous (CBB and SCB), with a higher proportion of areolar synovium in the bursal roofs compared to their floors. Blood vessels were consistently present in the subintima with a median density of 3% of the tissue surface area, being greatest in the SSB and SAB roofs (4.9% and 3.4% respectively) and least in the SAB floor (1.8%) and CBB roof and floor (both 1.6%). Nerve bundles and free nerve endings were identified in the subintima in approximately one-third of the samples, while encapsulated nerve endings were present in deeper tissue layers. The extensive expanse and attachments of the SAB support adoption of the term subacromial-subdeltoid bursa. Morphologically, the strong attachments of the bursal roofs and floors along with their free edges manifest as fixed and mobile portions, which enable movement in relation to surrounding structures. The presence of neurovascular structures demonstrates that these bursae potentially contribute blood supply to surrounding structures and are involved in mechanoreception. The anatomical details presented in this study clarify the morphology of the shoulder bursae, including histological findings that offer further insight into their potential function.

Clinical anatomy of the subacromial and related shoulder bursae: A review of the literature.

The subacromial bursa (SAB) is the main bursa of the shoulder. It facilitates normal movement and is also commonly involved in shoulder disorders. Other shoulder bursae have been described but their anatomy has not been well studied. Anatomical variation of shoulder bursae has been suggested and this has implications for clinical practice. This article reviews current knowledge of the normal anatomy of the SAB and related shoulder bursae. A systematic review of the English and German literature was conducted using databases and a hand search of reference lists focusing on the clinical anatomy of the SAB, coracobrachial and subcoracoid bursae and subtendinous bursa of subscapularis. Twenty-four original sources and 13 textbooks were identified. Fifteen studies described the general morphology of the shoulder bursae using cadaveric specimens, eight examined innervation, and one provided information about the blood supply of the SAB. The literature agrees that the SAB is consistent and well innervated with a lateral subdeltoid part and a variable subcoracoid portion. There is variability regarding the consistency, location, and communications of the coracobrachial and subcoracoid bursae and the superior part of the subtendinous bursa of subscapularis, and little information on their nerve and blood supply. Several bursae are present around the shoulder joint. Further research is warranted to understand the precise attachments, dimensions, and communications of the bursae, as well as their nerve and blood supply. This information will improve understanding of the clinical relevance of these bursae and inform appropriate assessment and treatment. Clin. Anat. 30:213-226, 2017. © 2017 Wiley Periodicals, Inc.