Finite element analysis of acromioclavicular joint stress in the treatment of Neer II distal clavicular fracture.

OBJECTIVE

This finite element analysis compared the biomechanical performance of two surgical approaches for Neer Type II distal clavicle fractures: isolated locking plate fixation versus locking plate fixation combined with anatomical double-bundle coracoclavicular ligament reconstruction.

METHODS

A three-dimensional finite element model of the shoulder was developed from the CT scan of a 30-year-old healthy male. Three conditions were simulated: an intact joint (Group A, control), a fractured joint fixed with a locking plate alone (Group B), and a fractured joint fixed with a locking plate plus ligament reconstruction (Group C). Materials were assigned linear elastic properties. Under a simulated 90° arm abduction load, we analyzed the distribution of Von Mises stress, the displacement of the distal clavicular fracture fragment, and the subacromial contact pressure.

RESULTS

Compared to Group B, Group C exhibited a more favorable biomechanical profile. The combined technique reduced the peak Von Mises stress at the distal clavicle by 37% (44.28 MPa vs. 70.12 MPa). Fragment displacement decreased by 42% in the horizontal plane (4.52 mm vs. 7.76 mm) and by 45% vertically (2.87 mm vs. 5.23 mm). The peak subacromial pressure was also lower in Group C (980 kPa vs. 1520 kPa).

CONCLUSION

Within the constraints of this finite element model, augmenting plate fixation with anatomical coracoclavicular ligament reconstruction reduced stress concentration and improved fragment stability in Neer type II fractures, suggesting a biomechanical advantage over plating alone. These computational results support the continued clinical investigation of this combined technique.