This cadaveric biomechanical study measured how forearm rotation changes force, contact area, and pressure across the radiocapitellar and ulnotrochlear joints. Ten extended elbows were axially loaded at 160 N during cyclic pronation and supination. It asks whether the pronated elbow is better suited for axial load transmission.
The clinical mental model here is simple: in the extended elbow under axial load, pronation spreads the radiocapitellar load over more surface, dropping peak pressure without changing total force. That is why patients instinctively pronate when bracing for a fall or throwing a punch. The pronated radial head is more congruent and better protected.
This connects directly to the terrible triad. Fitzpatrick showed axial loading in pronation produces radial head and coronoid fracture with posterior dislocation, while supination produces dislocation without fracture. The authors' interpretation is that pronation is protective until the interosseous membrane fails, after which the maximally proximal, engaged radius is more likely to fracture.
Practically, this reinforces why radial head length and interosseous membrane integrity matter after radial head arthroplasty. Underlengthening stresses the membrane, overlengthening overloads the joint.
This cadaveric biomechanical study measured how forearm rotation changes force, contact area, and pressure across the radiocapitellar and ulnotrochlear joints. Ten extended elbows were axially loaded at 160 N during cyclic pronation and supination. It asks whether the pronated elbow is better suited for axial load transmission.
The clinical mental model here is simple: in the extended elbow under axial load, pronation spreads the radiocapitellar load over more surface, dropping peak pressure without changing total force. That is why patients instinctively pronate when bracing for a fall or throwing a punch. The pronated radial head is more congruent and better protected.
This connects directly to the terrible triad. Fitzpatrick showed axial loading in pronation produces radial head and coronoid fracture with posterior dislocation, while supination produces dislocation without fracture. The authors' interpretation is that pronation is protective until the interosseous membrane fails, after which the maximally proximal, engaged radius is more likely to fracture.
Practically, this reinforces why radial head length and interosseous membrane integrity matter after radial head arthroplasty. Underlengthening stresses the membrane, overlengthening overloads the joint.