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

Abstract

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 potenti...

Histological changes and neural elements in the subacromial bursa on patients with rotator cuff tear: Pilot study

“…A recent study also reported the presence of mechanoreceptors in SAB. [31] Nevertheless, mechanoreceptors were absent in our and the probability of missing the mechanoreceptor was low because it is approximately 100 times larger than the nerve fibers. [1] In this study, the preoperative VAS score measured just before the operation was 2.9 ± 1.2, which is relatively lower than that in other studies.…”

“…A recent study also reported the presence of mechanoreceptors in SAB. [ 31 ] Nevertheless, mechanoreceptors were absent in our study, and the probability of missing the mechanoreceptor was low because it is approximately 100 times larger than the nerve fibers. [ 1 ]…”

The Effectiveness of Ultrasound-Guided Subacromial-Subdeltoid Bursa Combined With Long Head of the Biceps Tendon Sheath Corticosteroid Injection for Hemiplegic Shoulder Pain: A Randomized Controlled Trial

“…The SASD bursa is essential for shoulder movement and plays a key role in the subacromial gliding mechanism, which is covered by suprascapular nerve and free nerve endings ( 44 ). Several previous studies have shown that proinflammatory cytokines (IL-1β and IL-6), metalloproteases (MMPs) ( 45 ), and pain mediators (COX-2 and substance P) were associated with shoulder pain in patients with SASD bursitis.…”

Subacromial Bursa: A Neglected Tissue Is Gaining More and More Attention in Clinical and Experimental Research

“…This is supported by the fact that the subacromial bursa is innervated by several nerves, such as the suprascapular nerve and the lateral pectoral nerves and contains free nerve endings [ 64 , 65 , 66 ]. Thereby, neural structures are absent in the intima and found primarily in the subintima of the bursa in close proximity to blood vessels [ 67 ]. The presence of the neuropeptide substance P was rated as the reason for shoulder pain in patients with rotator cuff disease [ 68 ].…”

“…The subacromial bursa is a well vascularized structure [ 13 ] with a vessel density of 1.8–3.4%, depending on whether the floor or roof of the bursa is being investigated [ 67 ]. Due to the location of the subacromial bursa, its tight fibrovascular network with high proportions of proliferating cells is also covering the tendon in the case of a tendon tear.…”