Bone defects in the humeral head or antero-inferior edge of the glenoid cavity increase recurrence risk following arthroscopic Bankart repair. The present study sought to quantify such preoperative defects using a simple radiological technique and to determine a threshold for elevated risk of recurrence.

A retrospective study conducted in two centers enrolled patients undergoing primary arthroscopic Bankart repair for isolated anterior shoulder instability in 2005. The principle assessment criterion was revision for recurrent instability. Quantitative radiology comprised: the ratio of notch depth to humeral head radius (D/R) on AP view in internal rotation; Gerber’s X ratio between antero-inferior glenoid cavity edge defect length and maximum anteroposterior glenoid cavity diameter on arthro-CT scan; and the D1/D2 ratio between the glenoid joint surface diameters of the pathologic (D1) and healthy (D2) shoulders on Bernageau glenoid profile views. Seventy-seven patients were included, with a mean follow-up of 44 months (range, 36–54).

Overall recurrence rate was 15.6%. Recurrence risk was significantly greater when the humeral notch length was more or equal to 20% of the humeral head diameter and the Gerber ratio more or equal to 40%. On Bernageau views, mean D1/D2 ratio was 4.2% (range, 0–23%) in patients without recurrence, versus 5.1% (range, 0–19) in those with recurrence (P=0.003).

Beyond the above thresholds, bone defect as such contraindicates isolated arthroscopic stabilization. The D/R and Gerber ratios are simple and reproducible quantitative measurements can be taken in routine practice, enabling preoperative planning of complementary bone surgery as needed.

Level IV; retrospective cohort study.