Biomechanical performance of a novel light-curable bone fixation technique

Abstract

Traumatic bone fractures are often debilitating injuries that may require surgical fixation to ensure sufficient healing. Currently, the most frequently used osteosynthesis materials are metal-based; however, in certain cases, such as complex comminuted osteoporotic fractures, they may not provide the best solution due to their rigid and non-customizable nature. In phalanx fractures in particular, metal plates have been shown to induce joint stiffness and soft tissue adhesions. A new osteosynthesis method using a light curable polymer composite has been developed. This method has demonstrated itself to be a versatile solution that can be shaped by surgeons in situ and has been shown to induce no soft tissue adhesions. In this study, the biomechanical performance of AdhFix was compared to conventional metal plates. The osteosyntheses were tested in seven different groups with varying loading modality (bending and torsion), osteotomy gap size, and fixation type and size in a sheep phalanx model. AdhFix demonstrated statistically higher stiffnesses in torsion (64.64 ± 9.27 and 114.08 ± 20.98 Nmm/° vs. 33.88 ± 3.10 Nmm/°) and in reduced fractures in bending (13.70 ± 2.75 Nm/mm vs. 8.69 ± 1.16 Nmm/°), while the metal plates were stiffer in unreduced fractures (7.44 ± 1.75 Nm/mm vs. 2.70 ± 0.72 Nmm/°). The metal plates withstood equivalent or significantly higher torques in torsion (534.28 ± 25.74 Nmm vs. 614.10 ± 118.44 and 414.82 ± 70.98 Nmm) and significantly higher bending moments (19.51 ± 2.24 and 22.72 ± 2.68 Nm vs. 5.38 ± 0.73 and 1.22 ± 0.30 Nm). This study illustrated that the AdhFix platform is a viable, customizable solution that is comparable to the mechanical properties of traditional metal plates within the range of physiological loading values reported in literature.

Biomechanical Variability and Usability of a Novel Customizable Fracture Fixation Technique

“…Maximum load at failure was evaluated as the largest force value before failure and the corresponding maximum bending moment (BM) was calculated from the bending moment arm determined from the fixture dimensions. Bending stiffness (BS) was calculated from the moment versus displacement curve between 25-75% of the maximum bending moment [11]. The main outcome variables measured were BM (Nm) and BS (Nm/mm).…”

“…The AdhFix osteosynthesis platform has previously been biomechanically studied in various conformations in cyclic loading, bending and torsion in ex vivo porcine phalanxand ovine metacarpal fracture models in accordance with established biomechanical test recommendations and has shown promising biomechanical results when compared to conventional metal plates and Kirschner wires [10][11][12][13]. Overall, the AdhFix platform has demonstrated superior stiffness and inferior max bending moment when compared to a similarly sized conventional locking plate in reduced ex vivo ovine transverse fractures in 4-point bending.…”

“…Overall, the AdhFix platform has demonstrated superior stiffness and inferior max bending moment when compared to a similarly sized conventional locking plate in reduced ex vivo ovine transverse fractures in 4-point bending. However, studies suggest that the AdhFix platform provides sufficient biomechanical support to treat phalanx fractures, even though it does not provide the same ultimate bending moment as a corresponding metal plate [10,11]. Furthermore, in torsional biomechanical tests, AdhFix demonstrated superior stiffness and comparable maximum torque when compared to small fragment locking plates [11].…”

“…However, studies suggest that the AdhFix platform provides sufficient biomechanical support to treat phalanx fractures, even though it does not provide the same ultimate bending moment as a corresponding metal plate [10,11]. Furthermore, in torsional biomechanical tests, AdhFix demonstrated superior stiffness and comparable maximum torque when compared to small fragment locking plates [11].…”

“…However, the flexibility inherent in this approach also means that variations in size, shape, and biomechanical properties between each osteosynthesis are to be expected. Up until now the biomechanical studies of the AdhFix technique have been analyzed using only a single biomechanical researcher or a single surgeon to eliminate potential variations and allow for a comparison between different osteosynthesis techniques and AdhFix [10,11].…”