This cadaveric biomechanical study tested how tuberosity position affects shoulder motion after hemiarthroplasty for 4-part proximal humerus fractures. Using a robotically driven articulator, the authors compared anatomic (anterior fin) versus nonanatomic (lateral fin) tuberosity fixation in 5 fresh human shoulders. It asks whether horizontal-plane malposition of the tuberosities impairs external rotation.
When you assist on a hemiarthroplasty for a 4-part proximal humerus fracture, tuberosity rotation in the horizontal plane matters as much as version and height.
Historically emphasis was placed on getting version and height right, with less attention to rotational alignment of the tuberosities. This paper shows why that gap matters: nonanatomic placement raises rotation torque 8-fold and can make normal motion nearly impossible.
The mental model: tuberosity position sets rotator cuff tension. Push the lesser tuberosity posterior and you over-tension the subscapularis and anterior capsule while the greater tuberosity can abut the glenoid and mechanically block rotation.
Use the bicipital groove as your lighthouse. Reattaching tuberosities to the anterior fin (over the groove) reliably reproduces anatomic reduction; the lateral fin predictably malreduces them. This is a 5-specimen cadaver study of external rotation only, so it isolates a mechanism rather than proving clinical outcomes.
This cadaveric biomechanical study tested how tuberosity position affects shoulder motion after hemiarthroplasty for 4-part proximal humerus fractures. Using a robotically driven articulator, the authors compared anatomic (anterior fin) versus nonanatomic (lateral fin) tuberosity fixation in 5 fresh human shoulders. It asks whether horizontal-plane malposition of the tuberosities impairs external rotation.
When you assist on a hemiarthroplasty for a 4-part proximal humerus fracture, tuberosity rotation in the horizontal plane matters as much as version and height.
Historically emphasis was placed on getting version and height right, with less attention to rotational alignment of the tuberosities. This paper shows why that gap matters: nonanatomic placement raises rotation torque 8-fold and can make normal motion nearly impossible.
The mental model: tuberosity position sets rotator cuff tension. Push the lesser tuberosity posterior and you over-tension the subscapularis and anterior capsule while the greater tuberosity can abut the glenoid and mechanically block rotation.
Use the bicipital groove as your lighthouse. Reattaching tuberosities to the anterior fin (over the groove) reliably reproduces anatomic reduction; the lateral fin predictably malreduces them. This is a 5-specimen cadaver study of external rotation only, so it isolates a mechanism rather than proving clinical outcomes.