Fit assessment of anatomic plates for the distal medial tibia.

OBJECTIVES

With the development and popularization of minimally invasive surgical methods and implants for fracture fixation, it is increasingly important that the available implants are precontoured to the specific anatomic location for which they are designed. The objective of this study was to develop a noninvasive method and criteria for quantifying the fit of a distal periarticular medial tibia plate and to test the method on a small set of tibia models.

METHODS

The undersurface of the plate was extracted from a digital model of the plate. The surface of the plate was fitted to 21 computer tomography (CT)-based 3-dimensional (3-D) models of human tibiae. Four criteria were defined that constitute an anatomic plate fit and subsequently were applied for the quantitative fit assessment. The fitting of the plate undersurface to the bone was entirely conducted in a virtual environment.

RESULTS

An anatomic fit of the plate was achieved for 4 of the models (19%). The individual categories generated fits of 62% (n = 13) for the proximal end; 43% (n = 9) for the proximal angle; 57% (n = 12) for the middle distance; and 57% (n = 12) for a distal fit.

CONCLUSIONS

Although for the 4 individual criteria plate fits of 43%-62% were achieved, a global/anatomic fit only occurred for 19% of the bone models. This outcome is likely a result of bone morphology variations, which exist in a random population sample combined with the effects of a nonoptimized plate shape. Recommendations for optimizing the fit of the plate are discussed.