Preoperative glenoid considerations for shoulder arthroplasty: a review

Abstract

Preoperative assessment of the glenoid in the setting of shoulder arthroplasty is critical to account for variations in glenoid morphology, wear, version, inclination, and glenohumeral subluxation.Three-dimensional computed tomography (3D CT) scan assessment of the morphology of glenoid erosion allows for a more accurate surgical decision-making process to correct deformity and restore the joint line.Newer technology has brought forth computer-assisted software for glenoid planning in shoulder arthroplasty and patient-specific instrumentation.There have been promising early findings, although further evaluation is needed to determine how this technology impacts implant survivorship, function, and patient-reported outcomes. Cite this article: EFORT Open Rev 2020;5:126-137. DOI: 10.1302/2058-5241.5.190011.

Keywords: glenoid classification; glenoid deformity; preoperative planning; shoulder 3D CT scan; shoulder arthroplasty.

Fig. 1

(A) Type A1 glenoid on an axillary lateral radiograph of a left shoulder, characterized by a well-centred humeral head with mild, symmetric glenoid erosion in the absence of glenohumeral subluxation. (B) Type A2 glenoid on an axillary lateral radiograph of a right shoulder, characterized by deeper, symmetric glenoid erosion in which a line connecting the anterior and posterior glenoid rims would transect the humeral head.

Fig. 2

(A) Type B1 glenoid on axial CT, characterized by posterior glenoid wear without significant glenoid erosion; note the subchondral cyst beneath the posterior glenoid articular surface. (B) Type B2 glenoid on axial CT, characterized by posterior subluxation of the humeral head on the glenoid, with subsequent posterior glenoid erosion and a characteristic biconcave appearance. (C) In vivo B2 glenoid during a right shoulder arthroplasty, with characteristic biconcave appearance with increased wear and sclerosis on posterior aspect of glenoid (left side of picture). (D) Type B2 glenoid uploaded into preoperative planning software, showing calculated glenoid version, glenoid inclination, and posterior humeral head subluxation measurements, respectively (BLUEPRINT, Wright Medical, Memphis, TN, USA). (E) Type B3 glenoid on axial CT, characterized by progression of posterior wear leading to an excessively retroverted, monoconcave glenoid.

Fig. 3

(A) Type C1 glenoid on axial CT, characterized by dysplastic glenoid retroversion greater than 25 degrees. (B) Type C2 glenoid on axial CT, characterized by a dysplastic, high premorbid glenoid retroversion in addition to degenerative posterior glenoid wear resulting in biconcavity.

Fig. 4

Type D glenoid on axial CT, which, while rare, is characterized by glenoid anteversion.

Fig. 5

Favard type E glenoids. (A) E0: superior humeral head migration without glenoid erosion, on true AP radiograph. (B) E1: concentric glenoid erosion, on coronal CT. (C) E2: superior erosion limited to the superior glenoid, on coronal CT. (D) E3: erosion extending to the inferior glenoid edge, on coronal CT.

Fig. 6

(A) Glenoid version as measured on an axillary right shoulder radiograph using the Friedman method, where version is the angle between the glenoid line and the perpendicular (dashed) to the line joining the medial edge of the scapula and the centre of the glenoid (scapular axis). (B) Glenoid version as measured on axial CT using the Friedman method, where version is the angle between the glenoid line and the perpendicular (dashed) to the line joining the medial edge of the scapula and the centre of the glenoid (scapular axis). (C) Glenoid version as measured on axial CT using the glenoid hull method, where version is measured in a similar way to the Friedman method, but with the glenoid hull plane (the line between the centre of the glenoid and the point of the scapula where the anterior and posterior cortices meet medially) replacing the scapular axis.

Fig. 7

(A) Glenoid inclination as measured on a coronal CT of a left shoulder using the beta angle, which is the angle formed by the intersection of the glenoid line and the tangential line through the floor of the supraspinous fossa. The value of inclination is then calculated as the beta angle subtracted from 90. (B) The critical shoulder angle (CSA) shown on a true shoulder anteroposterior radiograph, defined as the intersection angle at the inferior glenoid margin between the glenoid line and the line drawn from the inferior bony margin of the glenoid to the lateral-most border of the acromion. (C) The reverse shoulder (RSA) angle measured on a coronal CT of a left shoulder, defined as the angle between the perpendicular (dashed line) of the tangential line through the floor of the supraspinous fossa and the line through the inferior glenoid fossa (connecting the inferior glenoid rim to the intersection of the supraspinous fossa tangential line and the glenoid rim).

Fig. 8

(A) The Walch index for glenohumeral subluxation, defined as the ratio of line D to E, where line A refers to the glenoid line, B to its perpendicular which bisects the glenoid, C to a line parallel with A transecting the medial third of the humeral head, and lines D and E represent humeral head measurements along line C posterior to line C and from anterior-posterior humeral head, respectively. (B) Scapulohumeral subluxation index, measured using the glenoid hull plane. The measurement is again obtained by the ratio of line D to E, where line B is replaced by the line along the glenoid hull plane (connecting the centre of the glenoid and the point of the scapula where the anterior and posterior cortices meet medially) and line C transects the medial third of the humeral head and is perpendicular to line B. Lines D and E again represent humeral head measurements along line C posterior to line C and from anterior-posterior humeral head, respectively.