scholarly journals Biomechanical comparison of two locking plate constructs under cyclic torsional loading in a fracture gap model

2015 ◽  
Vol 28 (05) ◽  
pp. 323-330 ◽  
Author(s):  
A. Bilmont ◽  
S. Palierne ◽  
M. Verset ◽  
P. Swider ◽  
A. Autefage
Keyword(s):  
Locking Plate ◽  
Torsional Loading ◽  
Screw Head ◽  
The Third ◽  
Cyclic Torsion ◽  
Locking Screws ◽  
Locking Compression Plates ◽  
Number Of Cycles ◽  
Biomechanical Comparison ◽  
Locking Screw

SummaryObjectives: The number of locking screws required per fragment during bridging osteo-synthesis in the dog has not been determined. The purpose of this study was to assess the survival of two constructs, with either two or three screws per fragment, under cyclic torsion.Methods: Ten-hole 3.5 mm stainless steel locking compression plates (LCP) were fixed 1 mm away from bone surrogates with a fracture gap of 47 mm using two bicortical locking screws (10 constructs) or three bicortical locking screws (10 constructs) per fragment, placed at the extremities of each LCP. Constructs were tested in cyclic torsion (range: 0 to +0.218 rad) until failure.Results: The 3-screws constructs (29.65 ± 1.89 N.m/rad) were stiffer than the 2-screws constructs (23.73 ± 0.87 N.m/rad), and therefore, were subjected to a greater torque during cycling (6.05 ± 1.33 N.m and 4.88 ± 1.14 N.m respectively). The 3-screws constructs sustained a significantly greater number of cycles (20,700 ± 5,735 cycles) than the 2-screws constructs (15,600 ± 5,272 cycles). In most constructs, failure was due to screw damage at the junction of the shaft and head. The remaining constructs failed because of screw head unlocking, sometimes due to incomplete seating of the screw head prior to testing.Clinical significance: Omitting the third innermost locking screw during bridging osteosynthesis led to a reduction in fatigue life of 25% and construct stiffness by 20%. Fracture of the screws is believed to occur sequentially, starting with the innermost screw that initially shields the other screws.

scholarly journals Biomechanical Comparison of Two Locking Plate Constructs Under Cyclic Loading in Four-Point Bending in a Fracture Gap Model: Two Screws versus Three Screws Per Fragment

2019 ◽  
Vol 32 (01) ◽  
pp. 059-066 ◽  
Author(s):  
Sophie Palierne ◽  
Baptiste Froidefond ◽  
Pascal Swider ◽  
André Autefage
Keyword(s):  
Relative Displacement ◽  
Bending Test ◽  
Test Range ◽  
Locking Screws ◽  
Four Point Bending ◽  
Plate Fracture ◽  
The Difference ◽  
Number Of Cycles ◽  
Biomechanical Comparison ◽  
Locking Screw

Objectives The number of locking screws required per fragment during bridging osteosynthesis has not been fully determined in the dog. The purpose of this study was to assess the survival of two constructs, with either two or three screws per fragment, under cyclic bending. Methods A 10-hole, 3.5-mm stainless steel locking compression plate was fixed 1 mm away from a bone surrogate in which the fracture gap was 47 mm. Two groups of 10 constructs, prepared with either two or three bicortical locking screws placed at the extremities of each fragment, were tested in a load-controlled 4-point bending test (range 0.7 to + 7 Nm) until failure. Results The 3-screw constructs were stiffer than the 2-screw constructs (19.73 ± 0.68 N/mm vs. 15.52 ± 0.51 N/mm respectively) and the interfragmentary relative displacements were higher for the 2-screw constructs (11.17 ± 0.88%) than for the 3-screw constructs (8.00 ± 0.45%). The difference between the number of cycles to failure for the 3-screw constructs (162,448 ± 30,073 cycles) and the 2-screw constructs (143,786 ± 10,103 cycles) was not significant. Failure in all constructs was due to plate fracture at the level of the compression holes. Clinical Significance Omission of the third innermost locking screw during bridging osteosynthesis subjected to bending forces led to a 20% reduction in construct stiffness and increased relative displacement (+39.6%) but did not change fatigue life.

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

2010 ◽  
Vol 23 (01) ◽  
pp. 7-13 ◽  
Author(s):  
N. M. M. Moens ◽  
J. Runciman ◽  
G. Monteith ◽  
S. Gordon
Keyword(s):  
Plastic Deformation ◽  
Locking Plate ◽  
Combination Group ◽  
Clinical Value ◽  
Locking Screws ◽  
Torsional Loads ◽  
Failure Point ◽  
Locking Screw ◽  
Torsional Properties ◽  
Torque Angle

SummaryLittle 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.

scholarly journals Temporal Changes in Reverse Torque of Locking-Head Screws Used in the Locking Plate in Segmental Tibial Defect in Goat Model

2021 ◽  
Vol 8 ◽  
Author(s):  
Remigiusz M. Grzeskowiak ◽  
Rebecca E. Rifkin ◽  
Elizabeth G. Croy ◽  
Richard C. Steiner ◽  
Reza Seddighi ◽  
...  
Keyword(s):  
Locking Plate ◽  
Segmental Bone Defect ◽  
Stable Fixation ◽  
Plate Removal ◽  
Locking Screws ◽  
Reverse Torque ◽  
Segmental Bone ◽  
Locking Screw ◽  
With Screws ◽  
Over Time

The objective of this study was to evaluate changes in peak reverse torque (PRT) of the locking head screws that occur over time. A locking plate construct, consisting of an 8-hole locking plate and 8 locking screws, was used to stabilize a tibia segmental bone defect in a goat model. PRT was measured after periods of 3, 6, 9, and 12 months of ambulation. PRT for each screw was determined during plate removal. Statistical analysis revealed that after 6 months of loading, locking screws placed in position no. 4 had significantly less PRT as compared with screws placed in position no. 5 (p < 0.05). There were no statistically significant differences in PRT between groups as a factor of time (p > 0.05). Intracortical fractures occurred during the placement of 151 out of 664 screws (22.7%) and were significantly more common in the screw positions closest to the osteotomy (positions 4 and 5, p < 0.05). Periosteal and endosteal bone reactions and locking screw backout occurred significantly more often in the proximal bone segments (p < 0.05). Screw backout significantly, negatively influenced the PRT of the screws placed in positions no. 3, 4, and 5 (p < 0.05). The locking plate-screw constructs provided stable fixation of 2.5-cm segmental tibia defects in a goat animal model for up to 12 months.

scholarly journals Removal of locking plates: new implant, new challenges and new solutions

2011 ◽  
Vol 1 (2) ◽  
pp. 25
Author(s):  
Bhavuk Garg ◽  
Tarun Goyal ◽  
Vijay Kumar ◽  
Rajesh Malhotra ◽  
Prakash P. Kotwal
Keyword(s):  
Locking Plate ◽  
Perioperative Complications ◽  
Point Of View ◽  
Locking Plates ◽  
Screw Head ◽  
Plate Removal ◽  
Novel Technique ◽  
Initial Surgery ◽  
New Challenges ◽  
Locking Screw

Removal of locking plates in many ways poses novel challenges compared to conventional plates. None of the techniques described for the removal of locking plates are adequate for all situations. We report our experience of 27 patients from whom a total of 33 locking plates were removed. We also describe a novel technique for the removal of locking plates which in our experience could be used in most of these patients because it is appropriate for all situations and, from a technical point of view, is easy to use. Our new technique consists of removing the problematic locking screw by cutting the plate on both sides of the screw hole and using the screw head-plate hole unit for removal. We analyzed all these patients for the location of the plate, number of locking screws, time of implant removal since the initial surgery, reason for removal of the plate, nature of the difficulties encountered during surgery, and any perioperative complications. A total of 43 (17.34%) screws were difficult to remove. Twenty screws were found to be stripped, 15 were jammed and 8 were broken. Fourteen of the 20 stripped screws and all 15 jammed screws were removed using our technique. We found this technique of locking plate removal to be very versatile and useful in most of the cases in which removal was difficult. At the same time, it also causes less damage to the bone compared to other techniques.

scholarly journals Effect of monocortical and bicortical screw numbers on the properties of a locking plate-intramedullary rod configuration

2016 ◽  
Vol 29 (06) ◽  
pp. 459-465 ◽  
Author(s):  
Kevin Parsons ◽  
Julie Etches ◽  
Katie Hamilton ◽  
Neil Burton ◽  
Elinor Field
Keyword(s):  
Locking Plate ◽  
Screw Loosening ◽  
Locking Screws ◽  
Pull Out ◽  
Physiological Load ◽  
Significant Difference ◽  
Load To Failure ◽  
Axially Loaded ◽  
Locking Screw ◽  
Bicortical Screw

SummaryObjectives: To evaluate the effect of varying the number and configuration of locking bicortical and monocortical screws on a plate-rod construct using a mid-diaphyseal femoral ostectomy model.Methods: Thirty Greyhound femurs were assigned to six groups (A-F). An intramedullary pin was placed in each bone following which a 3.5 mm locking plate was applied with six differing locking screw configurations. Groups A to C had one bicortical screw in the most proximal and distal plate holes and one to three monocortical locking screws in the proximal and distal fragments. Groups D to F had no bicortical screws placed and two to four monocortical locking screws in proximal and distal fragments. Each construct was axially loaded at 4 Hz from a preload of 10 Newtons (N) to 72 N, increasing to 144 N and 216 N, each of 6000 cycles with a further 45,000 cycles at 216 N to simulate a three to six week postoperative convalescence period. Constructs were then loaded to failure.Results: No construct suffered screw loosening or a significant change in construct stiffness during cyclic loading. There was no significant difference in load to failure of any construct (p = 0.34), however, less variation was seen with monocortical constructs. All constructs failed at greater than 2.5 times physiological load, and failure was by bending of the intramedullary pin and plate rather than screw loosening or pull-out.Clinical significance: Axially loaded locking monocortical plate-rod constructs applied to the canine femur may confer no difference biomechanically to those employing locking bicortical screws.

scholarly journals Internal Radioulnar Fixation for Treatment of Nonunion of Proximal Radius and Ulna Fractures in a Toy Breed Dog

VCOT Open ◽  
2021 ◽  
Vol 04 (01) ◽  
pp. e24-e31
Author(s):  
Luca Vezzoni ◽  
Paolo Abrescia ◽  
Aldo Vezzoni
Keyword(s):  
Locking Plate ◽  
Callus Formation ◽  
Previous Treatment ◽  
Bone Morphogenetic Protein 2 ◽  
Distal Ulna ◽  
Proximal Ulna ◽  
Proximal Radius ◽  
Locking Screws ◽  
Morphogenetic Protein ◽  
Ulna Fractures

AbstractIn this case report, we describe an alternative surgical procedure to treat proximal radius and ulnar nonunion in a toy breed dog. A 14-month-old, Maltese cross-breed dog was referred after previous treatment with external and internal fixation had failed, resulting in a nonunion of a fracture of the proximal radius and ulna with the proximal radius fragment too small and friable to be used for fixation. A craniomedial approach was made to debride the radius nonunion site and a second approach to the lateral aspect of the ulna was made. The fracture was realigned and a titanium locking plate was applied in bridging fashion, fixed to the proximal ulnar fragment with three locking screws in the most proximal plate holes, a fourth screw was inserted in the mid-shaft of the distal ulnar fragment and three locking screws were inserted in the distal most holes of the plate through the distal ulna to engage the distal radial fragment. A recombinant bone morphogenetic protein 2 graft was inserted into the radius and ulna fracture sites. The dog had a successful clinical and radiographic outcome with bridging of the defect 4 weeks postoperatively and complete callus formation 8 weeks postoperatively. Implants have undergone dynamization and then removal. Use of a locking plate as an internal fixator achieving fixation of the proximal ulna and distal radius can be considered an option for the treatment of proximal radioulnar nonunions with a small proximal radial fragment.

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