Acromion and glenoid shape: Why are they important predictive factors for the future of our shoulders?

Abstract

The shape of the acromion differs between patients with degenerative rotator cuff tears and individuals without rotator cuff pathology.It can be assessed in the sagittal plane (acromion type, acromion slope) and in the coronal plane (lateral acromion angle, acromion index, critical shoulder angle).The inter-observer reliability is better for the measurements in the coronal plane.A large lateral extension (high acromion index or high critical shoulder angle) and a lateral down-sloping of the acromion (low lateral acromion angle) are associated with full-thickness supraspinatus tears.The significance of glenoid inclination for rotator cuff disease is less clear.The postulated patho-mechanism is the compression of the supraspinatus tendon between the humeral head and the acromion. Bursal side tears might be caused by friction and abrasion of the tendon. Articular side tears could be due to impairment of the gliding mechanism between tendon fibrils leading to local stress concentration. Further research is needed to understand the exact pathomechanism of tendon degeneration and tear.Cite this article: EFORT Open Rev 2017;2. DOI: 10.1302/2058-5241.2.160076. Originally published online at www.efortopenreviews.org

Radiological and biomechanical assessment of displaced greater tuberosity fractures

“…It is therefore logical that the supraspinatus tendon rather than the greater tuberosity impinges against the undersurface of the acromion or the coracoacromial ligament. This pathomechanism is consistent with the literature concerning impingement syndrome [ 19 – 21 ]. CT scans with three-dimensional reconstruction of the shoulder and animation of the bones would therefore not correctly simulate subacromial impingement.…”

Editorial Commentary: Does the Morphology of the Acromion Explain All Rotator Cuff Tears?

“…One hypothesis is that increased subacromial pressure alters the microstructure and the flexibility of the tendons. 6 Tendon degeneration alone, however, does not explain all rotator cuff tears. In many cases, a trauma causes the tendon rupture.…”

“…5 It should be noted that both the critical shoulder angle and the acromion index quantify the lateral extension of the acromion with respect to the glenoid plane and that they are not independent variables. 6 Combining them in a single analysis would maybe provide even better evidence. How a large acromion contributes to rotator cuff lesions needs to be clarified.…”

Editorial Commentary: Angles, Ratios, and Rotation—Is It Worth Splitting Hairs Over the Critical Shoulder Angle?

“…Several authors suggested that a lateralized acromion would result in an overloaded supraspinatus resulting in a tear. 11,13 Nyffeler and Meyer 14 proposed that repetitive compression of the posterosuperior cuff by a lateralized acromion results in altered gliding capacity of the tendon fibrils causing local stress concentration, resulting in a tendon tear. Furthermore, if a preoperatively high CSA or AI could result in an RCT, would decreasing it by lateral acromioplasty minimize the chance of recurrence of a postoperative tear?…”