Proximal ulna morphometry: which are the "true" anatomical preshaped olecranon plates?

Area of Science:

• Orthopedic surgery
• Biomechanics
• Anatomical studies

Background:

• Optimal surgical fixation of proximal ulna fractures requires implants that precisely match bone anatomy.
• Existing olecranon plates may not fully replicate the complex geometry of the proximal ulna, potentially leading to suboptimal fit and outcomes.

Purpose of the Study:

• To determine the ideal design parameters for an anatomical preshaped olecranon plate.
• To define the optimal varus and anterior angulation, and dimensions for olecranon plates based on proximal ulna morphology.

Main Methods:

• A detailed geometric analysis of 200 Caucasian proximal ulnae was performed using digital calipers and goniometers.
• Measurements of varus and anterior angulation, olecranon angle, and olecranon length were recorded.
• The fit of three different contoured olecranon plates was evaluated on a model ulna.

Main Results:

• The proximal ulna exhibits an average varus angulation of 8.48° and anterior angulation of 8.49°.
• These angulations are located approximately 8.19 cm and 8.63 cm distal to the proximal bone point, respectively.
• Only a plate with both varus and anterior angulation demonstrated a good fit to the ulna model in two planes.

Conclusions:

• Anatomical preshaped olecranon plates should incorporate average varus and anterior angulations of the ulna.
• The olecranon component of the plate should align with the average olecranon angle and not exceed the average olecranon length.
• Such optimized plates are expected to facilitate accurate intraoperative restoration of proximal ulna anatomy, potentially improving results for complex fractures.