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

Abstract

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.

Three-dimensional computed tomography mapping and analysis of distal femur fractures (AO/OTA types 33A, 33B, and 33C)

“…In type C fractures, the distance from the lower border of the fracture line hot zone to the joint line was approximately 5 cm, and the perpendicular length of the hot zone was about 4 cm. Although the distance of the hot zone measured on the femur template can only be used as a reference, osteotomy gaps created in the former studies (18)(19)(20)(21)(22) were not long enough to accurately simulate the fracture morphology, which may underpower the results drawn from those studies. According to the scale of the template model, we suggest that for type A fracture model, the osteotomy gap should be made approximately 4 cm and the supracondylar osteotomy at 4 cm proximal to the joint line.…”

“…Therefore, a modified surgical incision to the distal femur such as the ''Swashbuckler'' approach described by Starr et al (25) should be considered by orthopaedic surgeons in preoperative planning. Meanwhile, although the biomechanical study has found that double plate constructs provided more stable fixation than lateral plate + retrograde intramedullary nail (rIMN) constructs (19), lateral plate + rIMN constructs may be more suitable in type A3 fracture cases with dispersed medial comminuted metaphysis due to a lack of medial exposure.…”

Nail diameter significantly impacts stability in combined plate-nail constructs used for fixation of supracondylar distal femur fractures

“…[6,[23][24][25][26][27] Two recent biomechanical studies have looked at PN fixation of distal femur fractures. [4,5] Neither study evaluated the effect of nail diameter on construct stiffness. In the clinical setting, the effect of nail diameter has been evaluated in geriatric proximal intertrochanteric femur fractures.…”

“…Specimen mounting and testing followed a previously published protocol. [5] Briefly, specimens were first loaded in torsion using a custom testing jig on an Instron testing machine (Instron Model 3365, Norwood, Massachusetts). Torque was applied along the femoral mechanical axis in internal rotation to mimic internal rotation of the tibia during normal knee flexion.…”

“…[1][2][3] In addition, the use of PN constructs has been the focus of recent multiple biomechanical studies. [4][5][6] The purported benefits of this technique include improved resistance to fixation failure and earlier return to full weight bearing.…”