Quantification of the position, orientation, and surface area of bone loss in type B2 glenoids

The arthritic glenoid: anatomy and arthroplasty designs

“…However, existing designs orient the augment along the central axis of the implant, assuming that maximum bone loss is directed towards the 9 o'clock position in a right shoulder. As previously stated, the recent literature has found bone loss to occur in a posteroinferior direction towards the 8 o'clock position [14][15][16][17]. This may result in significant bone removal in order to achieve full backside seating [27,28].…”

“…The B2 arthritic triad (glenoid biconcavity, acquired glenoid retroversion, and humeral head posterior subluxation) presents one of the most challenging and controversial osteoarthritis patterns when managed with joint replacement [12•, 13]. The recent literature has suggested that in these biconcave asymmetrically eroded glenoids, maximum bone loss occurs in a posteroinferior direction with the erosion being directed towards the 8 o'clock position in a right shoulder [14][15][16][17]. The surgical options in these cases include hemi-arthroplasty, eccentric reaming, glenoid bone grafting, augmented glenoid components, or reverse shoulder arthroplasty [6•, 12•].…”

“…In asymmetrically eroded glenoids, humeral articular contact is concentrated on the posterior neoglenoid region. This region typically represents around 50 % of the total glenoid surface area [15], thereby concentrating the region of load transfer and contact over a decreased area. The result of this is substantially denser and less porous bone in the neoglenoid [38,39].…”

“…In more severe cases, with erosion progressing past the centre of the glenoid, alternative approaches should be considered. Standard components will likely result in peg perforation after eccentric reaming, and current augmented component designs do not account for the increased region of bone loss [15].…”

Controversies in Shoulder Arthroplasty

“…28,29 One study found that the deformity axis pointed on average to the 8 o'clock position (in a right shoulder) rather than in a true anterior to posterior plane. 30 This may be important when considering augment component design.…”