Supplemental Fixation of Supracondylar Distal Femur Fractures: A Biomechanical Comparison of Dual-Plate and Plate-Nail Constructs

Objectives: This biomechanical study compares the effectiveness of dual-plate (DP) and plate-nail (PN) constructs for fixation of supracondylar distal femur fractures in synthetic and cadaveric specimens. Methods: Twenty-four synthetic osteoporotic femurs were used to compare 4 constructs in an extra-articular, supracondylar fracture gap model (OTA/AO type 33-A3). Constructs included: (1) distal lateral femoral locking plate (DLFLP), (2) retrograde intramedullary nail (rIMN), (3) DLFLP + medial locking compression plate (DP construct), and (4) DLFLP + rIMN (PN construct). DP and PN constructs were then directly compared using 7 matched pairs of cadaveric femurs. Specimens underwent cyclic loading in torsion and compression. Biomechanical effectiveness was measured by quantifying the load-dependent stiffness of each construct. Results: In synthetic osteoporotic femurs, the DP construct had the greatest torsional stiffness (1.76 +/- 0.33 Nm/deg) followed by the rIMN (1.67 +/- 0.14 Nm/deg), PN construct (1.44 +/- 0.17 Nm/deg), and DLFLP (0.68 +/- 0.10 Nm/deg) (P < 0.01). The DP construct also had the greatest axial stiffness (507.9 +/- 83.1 N/mm) followed by the PN construct (371.4 +/- 41.9 N/mm), DLFLP (255.0 +/- 45.3 N/mm), and rIMN (109.2 +/- 47.6 N/mm) (P < 0.05). In cadaveric specimens, the DP construct was nearly twice as stiff as the PN construct in torsion (8.41 +/- 0.58 Nm/deg vs. 4.24 +/- 0.41 Nm/deg, P < 0.001), and over one-and-a-half times stiffer in compression (2148.1 +/- 820.4 vs. 1387.7 +/- 467.9 N/mm, P= 0.02). Conclusions: DP constructs provided stiffer fixation than PN constructs in this biomechanical study of extra-articular distal femur fractures. In the clinical setting, fracture morphology, desired healing mode, surgical approach, and implant cost should be considered when implementing these fixation strategies.