Introduction: The most common method for internal fixation of olecranon fractures is AO tension band wiring (TBW). A number of complications related to this technique have been described, such as subcutaneous prominence of the device, skin irritation, infection, loss of extension in the elbow joint and non-union.

To avoid those complications Dr. Robert J. Medoff has designed a new device, the ulnar sled, which will be shown on a picture.

The objective of this cadaver study was to determine the stability of olecranon fracture fixation with the ulnar sled and compare it with AO method.

Methods: In six matched pairs of fresh-frozen arms a fracture of the olecranon was created and stabilized with either TBW or the ulnar sled.

The ulnar sled (US) group: The two free legs of the sled were inserted into two pre-drilled holes from the tip of the olecranon into the ulna medullary cavity of the ulna. The washer was then placed with its slot over the prominence of the sliding plate and with a screw fixed bicortically into the ulna, through the distal part of the proximal oval washer hole. Compression over the fracture site could be observed visually and the washer was finally fixed with another bicortical screw in its distal hole.

The TBW group: In the TBW group the AO technique with oblique bicortical K-wires and the two-knot-modification was used.

Mechanical Testing: First the brachialis and then the triceps muscle were sequentially loaded with 5 kg (50N) for 20 cycles in three different angles: 45, 90 and 135. The fracture displacement was measured before and after loading.

Results: The increase in the fracture gap after 20 cycles of loading for the two fixation techniques will be shown in a table. There was no significant increase of the fracture gap for either device when loading the brachialis muscle at any of the three flexion angles. The fracture displacement in 90 in triceps loading was 0.23mm in the the US group and in 0.19mm in the TBW group. This difference was not significant (p> 0.05). Similar results were obtained for the other flexion angles. Almost no displacement was observed in brachialis loading with either method.

Discussion: The results suggest that the ulnar sled method is a stable surgical method for fixation of uncommuted olecranon fractures when compared to TBW.