Saha analyzes what keeps the humeral head in the glenoid during motion, not just at rest. Using anthropometry, radiography, and EMG in normal, dislocating, and paralyzed shoulders, he identifies the structural and muscular contributors to dynamic stability. The paper connects these factors to recurrent anterior dislocation and its surgical correction.
This paper is the conceptual root of how we still teach shoulder stability: a shallow socket holding only a third of the head demands active control, so the rotator cuff is not just a mover but a dynamic stabilizer.
Think of the cuff as steering the head into the glenoid throughout the arc. Subscapularis and infraspinatus balance the head to 150 degrees, then infraspinatus finishes the job to full elevation. Saha's four-factor framework explains why some patients dislocate with trivial force. Glenoid hypoplasia, anterior glenoid tilt, excess retrotorsion, and weak steerers each remove a layer of protection.
The 80 percent versus 26.5 percent anterior tilt difference is the practical takeaway: bony geometry, not just soft tissue, drives recurrent anterior instability. This logic underpins bony procedures for instability, including scapular neck osteotomy and humeral rotation osteotomy that Saha proposed to correct the underlying geometry.
Saha analyzes what keeps the humeral head in the glenoid during motion, not just at rest. Using anthropometry, radiography, and EMG in normal, dislocating, and paralyzed shoulders, he identifies the structural and muscular contributors to dynamic stability. The paper connects these factors to recurrent anterior dislocation and its surgical correction.
This paper is the conceptual root of how we still teach shoulder stability: a shallow socket holding only a third of the head demands active control, so the rotator cuff is not just a mover but a dynamic stabilizer.
Think of the cuff as steering the head into the glenoid throughout the arc. Subscapularis and infraspinatus balance the head to 150 degrees, then infraspinatus finishes the job to full elevation. Saha's four-factor framework explains why some patients dislocate with trivial force. Glenoid hypoplasia, anterior glenoid tilt, excess retrotorsion, and weak steerers each remove a layer of protection.
The 80 percent versus 26.5 percent anterior tilt difference is the practical takeaway: bony geometry, not just soft tissue, drives recurrent anterior instability. This logic underpins bony procedures for instability, including scapular neck osteotomy and humeral rotation osteotomy that Saha proposed to correct the underlying geometry.