Enlargement of Glenoid Defects in Traumatic Anterior Shoulder Instability

Abstract

Background:Large glenoid rim defects in patients with traumatic anterior shoulder instability are often regarded as a contraindication for arthroscopic Bankart repair, with a defect of 20% to 27% considered as the critical size. While recurrence of dislocations, male sex, and collision sports were reported to be the significant factors influencing large glenoid defects, the influences of subluxations and more detailed types of sports were not investigated.Purpose:To investigate the influence of the number of dislocations and subluxations and type of sport on the occurrence and size of glenoid defects in detail.Study Design:Case-control study; Level of evidence, 3.Methods:A total of 223 shoulders (60 with primary instability, 163 with recurrent instability) were prospectively examined by computed tomography. Glenoid rim morphology was compared between primary and recurrent instability. In patients with recurrent instability, the relationship between the glenoid defect and the number of dislocations and subluxations was investigated. In addition, glenoid defects were compared among 49 male American football players, 41 male rugby players, 27 male baseball players, and 25 female athletes.Results:The mean extent of the glenoid defect was 3.5% in shoulders with primary instability and 11.3% in those with recurrent instability. A glenoid defect was detected in 108 shoulders (66.2%) with recurrent instability versus 12 shoulders (20%) with primary instability. Regarding the influence of the total number of dislocations/subluxations, the average extent of the glenoid defect was 6.3% in 85 shoulders with 2 to 5 events, 12.9% in 34 shoulders with 6 to 10 events, and 19.6% in 44 shoulders with 11 or more events. The glenoid defect became significantly larger along with an increasing number of recurrences. Although recurrent subluxation without dislocation also influenced the glenoid defect size, the number of dislocations did not. The average extent of the glenoid defect was 12.0% in rugby players, 8.9% in American football players, 4.7% in female athletes, and 4.5% in baseball players. Glenoid defects were significantly smaller in male baseball players and female athletes than in male collision athletes.Conclusion:The glenoid defect is significantly enlarged by damage due to recurrent dislocation and subluxation; therefore, glenoid rim morphology differs markedly between primary and recurrent instability. Glenoid defect size is also influenced by sex and by the type of sport.

Is CT scan a predictor of instability in recurrent dislocation shoulder?

“…The correlation between the number of dislocation and the glenoid width defect was found to be significant ( p = 0.017). This result of the present study is similar to various other studies 15, 18, 20. The correlation between the number of dislocation and Hill-Sachs defect was also found to be significant ( p = 0.030).…”

“…This result of the present study is similar to various other studies. 15 , 18 , 20 The correlation between the number of dislocation and Hill-Sachs defect was also found to be significant ( p = 0.030). While the other study has found that Hill-Sachs defect has significant correlations with initial trauma and relocation.…”

Bipolar Bone Loss in Male Athletes With Traumatic Anterior Shoulder Instability: An Evaluation Using a New Scoring System

“…To quantify the glenoid defect, the inferior portion of the glenoid rim was approximated to a true circle on en face 3D-CT scans that had been reconstructed with elimination of the humeral head. 10 – 13 The extent of the glenoid defect was calculated as a percentage of the glenoid rim length by the equation B / A × 100%, where A is the diameter of the fitted circle and B is the width of the defect ( Figure 1A ). A Hill-Sachs lesion was diagnosed if an abnormal groove was detected on the posterolateral aspect of the head of the humerus.…”

Editorial Commentary: Is Arthroscopic Bankart Repair Using Suture Anchors on the Glenoid Appropriate Treatment for Traumatic Anterior Shoulder Instability?

“…We previously reported that glenoid defects were seen in 20% of shoulders with primary instability and 66.2% of shoulders with recurrent instability. 11 Thus, glenoid rim fractures are not rare in unstable shoulders, and it has recently come to be considered that assessment of glenoid bone defects is required when planning surgery for traumatic anterior shoulder instability. However, CT has not been established as an essential tool for evaluating patients with postoperative recurrence of instability and repeated scanning should be avoided because of radiation exposure, so plain radiographic or magnetic resonance imaging is often performed instead after instability recurs.…”