Posterior Glenoid Bone Loss and Instability: An Evidence-based Approach to Diagnosis and Management

Abstract

Posterior glenohumeral instability is an underappreciated cause of disability that may necessitate surgical intervention to allow functional glenoid restoration. However, posterior glenoid bone abnormalities, when sufficiently severe, may contribute to persistent instability despite a well-performed capsulolabral repair. Recognition and understanding of these lesions is critical to both surgical decision making and execution of the surgical plan. Numerous procedures have been described to address posterior instability including recent developments in arthroscopic grafting techniques. The purpose of this article was to provide an evidence-based strategy for diagnosis and management of posterior shoulder instability and glenoid bone loss.T o keep the humeral head centered within the glenoid during shoulder motion, the glenohumeral joint relies on the congruence of the glenoidhumeral head relationship, glenoid version, and a balance of static (ie, capsule, labrum, and glenohumeral ligaments) and dynamic (ie, rotator cuff musculature) stabilizers. When this balance becomes disrupted and concavity compression is altered, glenohumeral instability may occur, typically in an anterior or posterior direction.The primary soft-tissue stabilizers preventing posterior instability are the thick posterior-inferior glenohumeral ligament (PIGHL) and the posterior labrum. The PIGHL tightens in shoulder flexion to block posterior subluxation, while the posterior labrum centralizes the humeral head within the glenoid cavity and increases its functional depth. 1 Similar to their analogs in anterior instability, the posterior soft-tissue stabilizers are typically disrupted or attenuated. However, osseous stabilizers are often underappreciated for their importance in preventing recurrence. 2 Posterior instability and posterior capsular laxity most often occur secondary to repetitive posterior subluxation in the position of instability (ie, shoulder flexed and internally rotated) with the PIGHL under tension (eg, bench press and football blocking). It may also occur from acute injury including trauma and posterior muscular overpull. 3 Although posterior instability occurs with reported prevalence of 1.1 per 100,000 person-years, the true rate is likely higher. 4 In military populations, posterior instability is more commonly

The Perfect-Circle Technique Demonstrates Poor Inter-Rater Reliability in Measuring Posterior Glenoid Bone Loss on Magnetic Resonance Imaging

“…In contrast, posteriorly sloped bone loss occurs from erosive, repetitive, posterior loading and may not appear as distinct bone loss lesions when calculating the total area of loss on sagittal imaging. 30 …”

Risk Factors for Glenoid Bone Loss in the Setting of Posterior Glenohumeral Instability

“…Although no consensus guidelines exist for the use of posterior glenoid augmentation procedures, several bone block procedures have been described for use in patients with clinically significant posterior bone loss. Dickens et al 12 advocate for the use of posterior glenoid reconstruction in patients with bone loss of >20% or >10% in the setting of glenoid retroversion, failed primary posterior labral repair, or incompetent or irreparable posterior capsular-labral tissue. While outcome studies after posterior bone augmentation are limited, Gilat et al 15 found that distal tibial allograft augmentation resulted in good outcomes and a reasonable complication rate in a series of 10 patients.…”

Posterior Shoulder Instability and Glenoid Bone Loss: A Review and a Free Bone Graft Technique

“…Initially used in the context of anterior instability, this technique employs similar principles when used for the calculation of pGBL. Bone loss is calculated by dividing the width of the osseous defect by the diameter of a "perfect circle" placed on the inferior two-thirds of the glenoid [18]. It is prudent to point out that although anterior and posterior bone loss may be calculated in a similar fashion, the pathologic mechanisms differ significantly.…”

“…Critical bone loss in posterior instability from a quantitative standpoint has not been entirely defined. In a recent review, Dickens et al [18] suggested that capsulolabral repair in isolation is inadequate in cases of pGBL >20% in the primary setting and >10% in revision cases.…”

“…In cases of pGBL or failed prior stabilization attempts, this procedure offers certain advantages (Table 1). Distinct advantages of this procedure include a low risk of recurrent dislocation, a high rate of return to sport, and potentially less morbidity than with a glenoid osteotomy [18]. Furthermore, because the primary stability of the procedure relies on native bone-to-bone healing (as opposed to soft-tissue or allograft healing), an accelerated return to activity may be possible [12].…”