Biomechanical analysis of two ulnar head prostheses.

Area of Science:

• Orthopedic surgery
• Biomechanics
• Biomedical engineering

Background:

• The distal radioulnar joint (DRUJ) is crucial for forearm rotation.
• Ulnar head prostheses are used to restore DRUJ function after injury or resection.
• Evaluating the biomechanical effectiveness of these prostheses is essential.

Purpose of the Study:

• To assess the biomechanical effectiveness of two distinct ulnar head prostheses.
• To compare the biomechanics of the distal radioulnar joint after prosthesis implantation versus intact specimens.
• To evaluate the prostheses' ability to restore normal forearm rotation and joint stability.

Main Methods:

• Utilized 5 fresh-frozen cadaver arms for biomechanical testing.
• Employed electromagnetic sensors to measure forearm rotation, diastasis, and subluxation.
• Tested intact specimens and specimens with two types of ulnar head prostheses.
• Applied loads simulating pronator/supinator muscles for dynamic rotation analysis.

Main Results:

• Forearm rotation decreased in pronation after prosthesis implantation.
• Diastasis generally decreased across most forearm positions.
• Subluxation increased in supination compared to intact specimens.
• Both prostheses demonstrated near-normal DRUJ biomechanics compared to distal ulna resection outcomes.

Conclusions:

• Ulnar head prostheses can effectively restore distal radioulnar joint function.
• Despite minor changes in rotation and subluxation, the prostheses offer a viable alternative to distal ulna resection.
• These prostheses are recommended for improving outcomes in patients with compromised distal radioulnar joint integrity.