The effect of the combination of locking screws and non-locking screws on the torsional properties of a locking-plate construct

Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada.
Veterinary and Comparative Orthopaedics and Traumatology (Impact Factor: 0.89). 12/2009; 23(1):7-13. DOI: 10.3415/VCOT-09-05-0055
Source: PubMed


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.

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    • "A hybrid construct in which both locking and non-locking screws were used was selected because these constructs are commonly used in dogs [29]. 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.
    BMC Veterinary Research 06/2013; 9(1):125. DOI:10.1186/1746-6148-9-125 · 1.78 Impact Factor
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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.
    Veterinary and Comparative Orthopaedics and Traumatology 01/2011; 24(1):57-61. DOI:10.3415/VCOT-10-02-0020 · 0.89 Impact Factor
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    ABSTRACT: OBJECTIVE: To evaluate the complication rate of the double (DPO) and triple pelvic osteotomy (TPO) procedure (unilateral and bilateral) with a locking purpose-specific plate. STUDY DESIGN: Retrospective case series ANIMALS: Dogs (n = 26; 38 hips) MATERIALS: Medical records (January 2007-January 2011) of dogs that had unilateral or bilateral DPO or TPO were evaluated. Signalment, age, body weight, estimated preoperative subluxation and reduction angles, lameness, and complications were evaluated. Follow-up radiographs were evaluated for implant loosening or failure, femoral head coverage (FCH), pelvic dimensions, and radiographic evidence of healing. RESULTS: Screw loosening occurred in 1 of 266 (0.4%) screws placed and in 1 of 38 hips (2.6%). The rate of screw loosening was significantly lower than previously reported. Only 1 hip (2.6%) developed a major complication. Minor complications involving implants occurred in 2 hips (5.3%). Three to 5 locking screws were used per plate. There was a significant increase in FCH and Norberg angle (NA) compared with preoperative values. No clinically significant change in pelvic canal dimensions measured at 3 locations was identified. CONCLUSION: Locking 7-hole TPO plates with 3-5 locking screws resulted in a lower rate of major and minor implant associated complications than the reported complication rate for conventional 6-hole plates. En bloc pullout of the caudal aspect of the plate is an infrequent but repeatable complication associated with the locking TPO implant.
    Veterinary Surgery 12/2011; 41(1). DOI:10.1111/j.1532-950X.2011.00930.x · 1.04 Impact Factor
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