Effect of Elbow Position on Load to Failure in Olecranon Fracture Fixation: A Biomechanical Cadaveric Study

This study evaluates if relative flexion or extension of the ulnohumeral joint affects the strength of repair in olecranon fractures treated with a precontoured locking plate.

A cadaveric study was performed in matched pair cadaveric elbows. All soft tissue was dissected from the radius, ulna, and elbow of each specimen, leaving interosseous ligaments and joint capsules intact. Soft tissue from the humerus was dissected away, leaving only the triceps tendon and ulnar insertions intact. An oblique proximal to distal olecranon osteotomy was created in each specimen 1 cm from the tip of the olecranon. Internal fixation with standard precontoured locking plates and a Krackow augmentation suture with #2 FiberWire followed. Specimens were randomized to elbow position of 90 or 20 degrees° and loaded to failure via axial pull through the triceps. Load at failure, displacement at the time of failure, peak load, stiffness, and mechanism of failure was recorded and compared. The study was repeated a second time with the osteotomy more proximal, 0.6 cm creating a smaller fragment with less opportunities for locking screw fixation. This small fragment group was then tested as the large fragment group had.

There were no significant differences in load at failure, peak load, or stiffness between the elbow position in the large fragment group. Displacement at time of failure was significantly different, although not clinically relevant. Failure of fixation in this group was a mix of triceps avulsion and failure through fracture site. The smaller fragment group with less points of fixation demonstrated no statistically significant differences in any parameters. A majority of the failures were at the fracture site.

Ulnohumeral position does not significantly affect overall construct strength even in olecranon fractures with small proximal fragments with limited points of fixation.