Abstract
This experimental in vitro study evaluated the influence of screw length on the mechanical properties of a locking reconstruction plate designed with locking rings inserted into plate holes. Synthetic bone cylinders with 10 mm fracture gap and seven-hole locking reconstruction plates were used. Two groups of bone-plate constructs were assembled: Group 1 – three monocortical screws on each fracture side, Group 2 - three bicortical screws on each fracture side. In each group nine bone-plate constructs were tested until failure, three each in bending, compression and torsion. In each group, 21 bone-plate constructs were tested for failure in fatigue testing, seven each for bending, compression and torsion. In all static testing no significant differences were found between G1 and G2, except ultimate moment in torsion test (G2>G1; P=0.008). Statistical analysis revealed significant differences between groups in axial compression fatigue testing (G1>G2; P<0.05) and four-point bending fatigue testing (G1<G2; P<0.05) in maximum load, minimum load, maximum moment, and minimum moment. In conclusion, screw length can affect the mechanical properties of locking reconstruction plate. Compared to bicortical screws, monocortical screws were less resistant to bending than axial compression. This must be considered when choosing implant, particularly in fractures under high axial loads.
Highlights
Despite the variety of sizes and shapes of bone plates and screws, the choice of implants depends on various factors such as fracture site, fracture type, bone quality, strength and stiffness required, cost and availability[1,2,3]
Biomechanical evaluation was performed on acetabular fractures of canine cadavers for the same purpose[23]
In all static testing no significant differences were found between the monocortical (G1) and bicortical (G2) bone-plate constructs, except for the ultimate moment in the torsion test (G2>G1)
Summary
Despite the variety of sizes and shapes of bone plates and screws, the choice of implants depends on various factors such as fracture site, fracture type, bone quality, strength and stiffness required, cost and availability[1,2,3]. Several mechanical and biological advantages have been attributed to the locking screw–plate, including axial and angular stability due to its locking mechanism between plate and screw, preservation of the periosteal blood supply, reduced requirement for anatomical plate contouring, and possibility the system’s elasticity to stimulate bone healing[1,2,7,8,9,10]. These advantages have stimulated the modification or conversion of various traditional bone plates into locked systems, including reconstruction plates, by changing especially the screw-hole geometry.
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