Do Far Cortical Locking Screws in Locking Plates Lead to Earlier and Increased Medial Callus in Distal Femur Fractures Comparing to Standard Locking Screws?

Abstract

Background: Locking plates (LP) are commonly used to treat distal femur fracture. Far cortical locking (FCL) screws are designed to increase axial motion at the fracture site resulting in more callus formation in animal study. In our previous study, progress to healing was assessed. There were statistically significant differences in modified RUST score postoperatively with higher scores in the FCL group. However, the amount of callus formed was not quantitatively measured. The purpose of this study is to quantitatively assess the medial callus area (mm²) and changes in callus area over time in radiographs of distal femur fractures treated with FCL as compared to traditional locking plate constructs.

Methods: A retrospective review of medical records conducted to identify patients with distal femur fractures. Medial callus area from AP radiographs was quantified from 6-, 12- and 24-week postop radiographs using OrthoRead software. Medial callus areas were compared between FCL construct fixation and traditional LP.

Results: After applying inclusion and exclusion criteria, 69 patients with 70 total fractures were included for analysis. There were no significant differences between FCL (n=42) and LP (n=28) in demographic data or rates of complications (18%), fixation failures (10%), union (90%), or revision (10%) (all p>0.05). Medial callus areas did not significantly differ after adjustment for multiple comparisons between FCL vs. LP at 6 (195.2 mm² (0.0-2007.1) vs. 200.7 mm² (0.0-1137.0), p=0.982) or 12 (372.1 mm² (0.0-2241.9) vs. 298.1 mm² (0.0-1959.9), p=0.727) weeks postop. While between group differences were significant at 24 weeks postop (FCL:455.7 mm² (30.4-2388.2) vs. LP:287.8 mm² (0.0-1514.7), p=0.023) statistically significant differences were not sustained following adjustment for multiple comparisons (p=0.069). Larger medial callus was formed as duration from surgery increased to 24 weeks in the FCL as compared to the LP group in analyses limited to titanium implants ((FCL:455.7 mm² (30.4-2388.2) vs. LP: 259.25 mm² (0.001514.70), p=0.039).

Conclusion: In this study, there is increased callus generated in FCL vs LP constructs at 24 weeks postoperatively (p=0.02). This is in accordance with previous animal models. However clinical advantages of this increased callus were not identified in the study. Because of the study limitations and potential confounders, prospective studies are necessary to further assess whether there is a clinically relevant healing advantage of FCL over standard LP constructs.

Level of evidence: III.