Coracoacromial morphology: a contributor to recurrent traumatic anterior glenohumeral instability?

Abstract

Background: While scapular morphology contributes to glenohumeral osteoarthritis and rotator cuff disease, its role in traumatic glenohumeral instability remains unknown. We hypothesized that coracoacromial and glenoid morphology would differ between healthy subjects and those with recurrent traumatic anterior shoulder instability.Methods: Computed tomographic scans of 31 cadaveric control scapulae and 54 scapulae of patients with recurrent traumatic anterior shoulder instability and Hill-Sachs lesions were threedimensionally reconstructed. Statistical shape modelling identified the modes of variation between the scapulae of both groups. Corresponding measurements quantified these modes in relation to the glenoid center (linear offset measures), defined by the best-fit circle of the inferior glenoid, or glenoid center plane (angles), which bisects the glenoid longitudinally. Distances were normalized for glenoid size. Results:As compared to controls, the unstable coracoids were shorter (p=0.004), with a more superior and medial offset of the tip (mean difference [MD]: 7 and 3 mm, respectively; p<0.001), and an origin closer to the 12 o'clock position (MD: 6°; p<0.001). The unstable scapular spines

Thinking outside the glenohumeral box: Hierarchical shape variation of the periarticular anatomy of the scapula using statistical shape modeling

“…40,41 Owens et al 20 found that the coracohumeral distance was an independent risk factor for traumatic anterior shoulder instability, with an increased risk of instability of 20% for every 1-mm increase in coracohumeral distance. This was further confirmed by Jacxsens et al, 42 who found a more medial and superior orientation of the coracoid process in patients with anterior instability as compared to nonpathologic shoulders, suggesting that a difference in the position of the coracoid process and its attaching soft tissue alter the stabilizing function of the conjoined tendon in the shoulder. On the basis of the substantial shape variation around the coracoid seen in modes 4 and 5, differences in coracohumeral distance can be explained by an underlying deviation of the coracoid process.…”

The Trillat Procedure for Anterior Glenohumeral Instability

“…Recurrent traumatic AGI was significantly associated with a shorter coracoid, oriented more superomedial. Furthermore, the origin of the coracoid on the glenoid was located more posteriorly, closer to the 12 o'clock position than the 3 o'clock position 2 (Fig. 2).…”

“…Mean shape differences between a control group and a pathologic unstable scapula group according to a statistical shape modeling developed by Jacxsens et al 2 Blue arrows indicate an increase, whereas yellow arrows denote a decrease between the illustrated mean shape of the control group and the mean shape of the unstable group. The size of the arrow represents the magnitude of the morphologic differences.…”

“…The coracoid process acts as a bony block when transferred to the glenoid neck 6 . Although the mechanism of normal coracoid anatomy influencing stability remains unclear 1 , the position of the coracoid may provide a more important biomechanical function than previously thought 2 because its soft-tissue attachments can serve as an anterior buttress to prevent anterior humeral head dislocation, as demonstrated in several studies 1,7-9 .…”

“…Indeed, the authors found that during shoulder adduction, the CJT was oriented medial to the joint line, and when the shoulder was abducted and externally rotated, it was located lateral to the joint line, thus playing a restricted stabilizer effect in these shoulder positions 7 . Furthermore, during the Trillat procedure, medializing the coracoid also translates the CJT medially, which may enhance its barrier effect because the tendon will be oriented closer to the Mean shape differences between a control group and a pathologic unstable scapula group according to a statistical shape modeling developed by Jacxsens et al 2 Blue arrows indicate an increase, whereas yellow arrows denote a decrease between the illustrated mean shape of the control group and the mean shape of the unstable group. The size of the arrow represents the magnitude of the morphologic differences.…”