The Effect of Supratrochlear Foramen on Susceptibility of the Distal Humerus to Fracture – A Biomechanical Study

Background: The frequency of supratrochlear foramen (STF) varies considerably among different populations, from 0.3% and up-to 58%. The STF is theorized to be a stress riser increasing the distal humerus` tendency to fracture as a result of relatively low energy trauma. Divergent single column fracture is a rare type of intra-articular fracture of the distal humerus caused by low energy trauma in adolescence and young adults who have a large STF. To this date, very few cases of this fracture have been described.

Our study objective was to find whether the STF is simply an anatomical variant or if it truly raises the likelihood of a distal humeral fracture.

Materials and Methods: We used 24 identical synthetic humeral bones were split into even `case` and `control` groups. In the `case` group we drilled the olecranon fossa in order to simulate the STF in. The size and location of the hole were chosen in accordance to the epidemiologic studies describing the STF. Using the INSTRON 4500 loading frame we axially loaded the synthetic bone modules.

Results: Both study groups showed similar loading patterns and no statistically significant difference in maximal load to fracture.

Discussion: Despite the fact that the prevalence of the STF is relatively high and may reach over 50% in some population, only 6 cases of the `divergent single column` fracture pattern have been described over the years. This makes the assumption that the STF is a stress risers and a risk factor for supracondylar fractures questionable. Our study, using saw bone models with and without the STF found no statistically significant difference in the loading patterns and maximal load at the point of fracture. These results may also help to refute this theory. Future studies using cadavers may be developed based on our study module.