Is humeral segmental defect replacement device a stronger construct than locked IM nailing?

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Bone pathology

Background:

• Intramedullary (IM) nailing is standard for impending pathologic humeral fractures.
• Rotator cuff violation during IM nail insertion causes complications.
• A superior fixation method is needed for these fractures.

Purpose of the Study:

• To compare the mechanical properties of humeral segmental replacement prostheses and IM nails.
• To evaluate construct strength in a simulated impending pathologic humeral fracture model.

Main Methods:

• Nine matched pairs of human humeri were used.
• A 50% middiaphyseal defect simulated an impending fracture.
• Specimens were fixed with either an IM nail or a segmental defect prosthesis.
• Mechanical testing in torsion to failure was performed.

Main Results:

• Prosthesis constructs demonstrated greater peak torque and peak rotation at failure.
• Intramedullary nail constructs exhibited higher torsional stiffness.
• A linear relationship between peak torque and bone T-score was observed for both devices.
• The prosthesis showed greater superiority in weaker bones (lower T-scores).

Conclusions:

• Humeral segmental replacement prostheses provide a stronger construct than IM nails for impending pathologic humeral fractures.
• The prosthesis is a potentially advantageous alternative, especially in osteoporotic bone.
• Further clinical evaluation is warranted to confirm these biomechanical findings.