The effect of the combination of locking screws and non-locking screws on the torsional properties of a locking-plate construct
Little is known about the torsional properties of bone-plate constructs when a combination of locking and non-locking screws have been used. Sixty cadaveric canine femurs were divided into three groups. In the first group, the plate was affixed using three non-locking screws. In the second group, only locking screws were used while a combination of one locking and two non-locking screws were used in the third group. All constructs were subjected to torsion until failure. Torque, angle of torsion, and work were all calculated at the maximum failure point, as well as at five degrees of plastic deformation, which was thought to be more representative of clinical failure. At the maximum failure point, the locking group had significantly higher torque, angle, and work values than the non-locking group. The combination group was intermediate to the two other groups, and significantly differed from the non-locking group in torque, and from the locking group in work. At five degrees of plastic deformation, the locking group required significantly higher torque and work than the non-locking group. The combination group required a significantly higher torque than the non-locking group. This study suggests that a construct composed of all locking screws will fail at a greater torque value, and sustain greater work to failure in torsion compared to a construct composed of all non-locking screws. The addition of a single locking screw to an otherwise non-locking construct will increase the torque at the offset failure point and may be of clinical value in constructs subjected to high torsional loads.
Available from: Leonardo Augusto Lopes Muzzi
- "Mechanical properties comparison between these two fracture fixation systems was performed in this study aiming the subsequent clinical use of the implants. The use of canine femora was felt to closely mimic clinical reality as other materials would not have the same bone biomechanical properties (Gordon et al., 2010). The paired femora used for comparison between systems minimized variations like bone porosity and mineralization. "
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ABSTRACT: The purpose this original article is to compare the mechanical properties of an interlocking nail-plate combination (plate-nail) vs. an intramedullary pin-plate combination (plate-rod) applied to experimentally induced gap fractures in canine femora. Twenty four paired canine femora were assigned to either plate-nail or plate-rod with 2.7 mm or 3.5 mm system constructs. In each femur, a mid-diaphyseal ostectomy was performed and the selected system was applied. Paired system constructs were subjected to compression and bending tests. The maximum load differed significantly between fixation systems. The plate-nail system had greater maximum load than plate-rod system. The strength, stiffness and maximum deformation was similar between plate-rod and plate-nail. The plate-nail system proved to be a good option for diaphyseal long bone fracture fixation in dogs.
Available from: Marybeth Horodyski
- "A hybrid construct in which both locking and non-locking screws were used was selected because these constructs are commonly used in dogs . Furthermore, previous studies have shown that placement of a single locking screw in each of the major fracture segments increases a construct’s axial and torsional stability [29-32]. Another limitation that should be considered is that constructs had differences in the number of screws, in addition to differences in plate working length. "
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ABSTRACT: There are several factors that can affect the fatigue life of a bone plate, including the mechanical properties of the plate and the complexity of the fracture, position of the screws can influence construct stiffness, plate strain and cyclic fatigue of the plate. No studies have investigated these variables in implants utilized for long bone fracture fixation in dogs and cats. The purpose of the present study was to evaluate the effect of plate working length on construct stiffness, gap motion and resistance to cyclic fatigue of dog femora with a simulated fracture gap stabilized using a 12-hole 2.4 mm LCP. Femora were plated with 12-hole 2.4 mm locking compression plates (LCP) using 2 screws per fracture segment or with 12-hole 2.4 mm LCP using 5 screws per fracture segment resulting in a short working length.
Construct stiffness did not differ significantly between stabilization techniques. Implant failure did not occur in any of the plated femora during cycling. Mean +/- SD yield load at failure in the short plate working length stabilization technique were significantly higher than in the long plate working length stabilization technique.
In a femoral fracture gap model stabilized with a 2.4 mm LCP applied in contact with the bone, plate working length had no effect on stiffness, gap motion and resistance to fatigue. The short plate working length constructs failed at higher loading amount; however, yield loads for both short and long plate working length stabilization techniques were within physiologic range.
Available from: Jörg A Auer
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ABSTRACT: This prospective study describes a series of 18 olecranon fractures in 16 horses that were treated with locking compression plates (LCP). Twelve of the 18 fractures were simple (type 2), whereas six were comminuted (type 4). Six fractures were open and 12 were closed. Each horse underwent LCP osteosynthesis consisting of open reduction and application of one or two LCP. Complete fracture healing was achieved in 13 horses. Three horses had to be euthanatized: two because of severe infection and one because of a comminuted radial fracture 11 days after fixation of the olecranon fracture. Complications encountered after discharge of the horses from the Equine Hospital at the Vetsuisse Faculty (University of Zurich) included implant infection (n=2) and lameness (n=3), which were successfully treated with implant removal. Despite being easier to use, LCP osteosynthesis resulted in a clinical outcome similar to DCP osteosynthesis.
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