Effect of age, sex, height, ethnicity, and femoral bowing on the anatomical fitting of the LCP distal femur plate.

PURPOSE: Lateral locking-plate fixation is commonly used for distal femur fractures. Pre-contoured plates attempt to match the bony anatomy of the target patient population. However, plate fit is highly variable due to inter-subject morphological differences. If plate misfit is not recognised and addressed, axial malalignment may arise. This study evaluates the effects of age, sex, height, ethnicity, and femoral bowing on the anatomical fit of a distal femur plate.

METHODS

Unilateral 3D models of 80 (40 male, 40 female) Caucasian and 79 (34 male, 45 female) Vietnamese femora were utilised. Both cohorts consisted of young (< 65 years) and old (≥ 65 years) subjects, with 40 young and 40 old Caucasian, and 36 young and 43 old Vietnamese. The plate undersurfaces of 9-, 11- and 13-hole LCP Distal Femur plate 3D models were positioned on bone models and anatomical fitting was assessed through application of developed clinical criteria.

RESULTS

Satisfactory plate conformity was achieved from plate head up to hole 6, with most measurement locations fitting 52-100% of bones from both ethnicities. There was tendency towards proximal plate misfit from hole 8 onwards with 0-41% fit achieved in this region, and mean distances of 11.6 mm and 16.3 mm being observed at the proximal plate tip for Caucasians and Vietnamese respectively (p ≤ 0.017). Patient sex, height, ethnicity, and femoral bowing all had significant impacts on fit, while the effect of age was limited. Sex and ethnicity related height differences would suggest that patient height and femoral bowing are the main variables affecting fit.

CONCLUSIONS

The observed proximal plate misfit for both Caucasians and Vietnamese suggests LCP Distal Femur plates may exhibit less anatomical conformity than generally assumed. Where plates are used as a reduction tool, pre-operative templating of the intact contralateral femur may help identify plate misfit.