Assessment of BFX cup version in a three-dimensional model simulating the ventrodorsal radiographic view.

Objective: To measure truncated face and open face versions of the biological fixation (BFX) cup in a three-dimensional (3D) model simulating the ventrodorsal radiographic projection with different cup and pelvis positions.

Study design: Computer simulation.

Methods: Simulated ventrodorsal views were generated in silico using 3D models of a BFX cup and a medium-sized canine pelvis. Truncated face and open face versions of the BFX cup were defined and measured with various angles of cup version, cup inclination, and pelvic extension.

Results: Truncated face version was different from and underestimated open face version by 12° to 22° (p < .001). Open face version varied with inclination while truncated face version was unaffected by inclination. Open face version was dependent on the degree of pelvic extension while truncated face version was unaffected.

Conclusion: Open face version differed from truncated face version. Changes in open face version were not consistently matched by a change in truncated face version.

Clinical significance: The open face of the cup may be excessively retroverted without this being reflected by truncated face retroversion as seen on a ventrodorsal radiographic view. However, in this study, BFX cups placed with truncated face version and inclination in the normal range and an ALO of 45° yielded predictable open face version.