This Level V technique paper introduces the on-track/off-track model for anterior shoulder instability with bipolar bone loss. It replaces the qualitative engaging/non-engaging concept with a quantitative method using the glenoid track and Hill-Sachs interval. The authors build a 4-group treatment algorithm from these measurements.
When you see recurrent anterior instability, do not stop at glenoid bone loss. Assess both sides of the joint together. The mental model: the humeral head sweeps a track across the glenoid in abduction and external rotation. A Hill-Sachs lesion that stays within the track is stable. One that extends medial to it engages and dislocates.
The key move is calculating the glenoid track (0.83 × D − d) and comparing it to the Hill-Sachs interval. If the interval is larger, the lesion is off-track and a Bankart alone will fail. This paper reframes the old engaging/non-engaging question into a measurable one, and it debunks the over-diagnosis of engagement from dynamic exam under anesthesia. Real engagement is about 7%, not 34% to 46%.
The practical payoff is the 4-group algorithm: it tells you when to add remplissage, when to do a Latarjet, and when a humeral-sided procedure is still needed after Latarjet.
This Level V technique paper introduces the on-track/off-track model for anterior shoulder instability with bipolar bone loss. It replaces the qualitative engaging/non-engaging concept with a quantitative method using the glenoid track and Hill-Sachs interval. The authors build a 4-group treatment algorithm from these measurements.
When you see recurrent anterior instability, do not stop at glenoid bone loss. Assess both sides of the joint together. The mental model: the humeral head sweeps a track across the glenoid in abduction and external rotation. A Hill-Sachs lesion that stays within the track is stable. One that extends medial to it engages and dislocates.
The key move is calculating the glenoid track (0.83 × D − d) and comparing it to the Hill-Sachs interval. If the interval is larger, the lesion is off-track and a Bankart alone will fail. This paper reframes the old engaging/non-engaging question into a measurable one, and it debunks the over-diagnosis of engagement from dynamic exam under anesthesia. Real engagement is about 7%, not 34% to 46%.
The practical payoff is the 4-group algorithm: it tells you when to add remplissage, when to do a Latarjet, and when a humeral-sided procedure is still needed after Latarjet.