Effect of bending direction on the mechanical behaviour of 3.5 mm String-of-Pearls and Limited Contact Dynamic Compression Plate constructs

Summary

Objective: To compare the bending properties of String-of-Pearls^® (SOP) and Limited Contact Dynamic Compression Plate^® (LCDCP) constructs in orthogonal bending directions.

Methods: 3.5 mm SOP and LC-DCP plates were fixed to a bone model simulating a comminuted tibial fracture. Specimens were non-destructively tested in both mediolateral and craniocaudal bending for 10 cycles. Bending stiffness and total angular deformation were compared using parametric analyses (p <0.05).

Results: For both constructs, stiffness was significantly less when bending moments were applied against the thickness of the plates (mediolateral bending) than against the width (craniocaudal bending). When compared to the mediolateral plane, bending constructs in the craniocaudal plane resulted in a 49% (SOP group) and 370% (LC-DCP group) increase in stiffness (p <0.001). Mediolateral bending stiffness was significantly greater in the SOP than the LC-DCP constructs. Conversely, in craniocaudal bending, SOP constructs stiffness was significantly less than that of the LC-DCP constructs. The differences between the two constructs in total angular deformation had an identical pattern of significance.

Clinical significance: This study found that SOP showed less variability between the orthogonal bending directions than LC-DCP in a comminuted fracture model, and also described the bi-planar bending behaviour of both constructs. Although not exhibiting identical bending properties in both planes, SOP constructs had a more homogenous bending behaviour in orthogonal loading directions. The difference between the SOP with a circular cross sectional shape compared to the rectangular shape of standard plates is probably responsible for this difference.

Keywords

String-of-Pearls - SOP - Limited Contact- Dynamic Compression Plate - LC-DCP - craniocaudal bending - mediolateral bending - stiffness

• References

• 1 Johnson AL, Houlton JEF, Vannini R. AO principles of fracture management in the dog and cat.. Davos Platz, Switzerland: AO Publishing 2005
• 2 Muir P, Johnson KA, Markel MD. Area moment of inertia for comparison of implant cross-sectional geometry and bending stiffness. Vet Comp Orthop Traumatol 1995; 8: 146-152.
• 3 Standard specification and test method for metallic bone plates, ASTM F382-99 (re-approved 2008) e1 Annual Book of ASTM standards.. West Conshohocken, PA: ASTM; 2008
• 4 Zahn K, Frei R, Wunderle D. et al. Mechanical properties of 18 different AO bone plates and the clamp-rod internal fixation system tested on a gap model construct. Vet Comp Orthop Traumatol 2008; 21: 185-194.
• 5 Blake CA, Boudrieau RJ, Torrance BS. et al. Single cycle to failure in bending of three standard and five locking plates and plate constructs. Vet Comp Orthop Traumatol 2011; 24: 408-417.
• 6 DeTora M, Kraus K. Mechanical testing of 3.5 mm locking and non-locking bone plates. Vet Comp Orthop Traumatol 2008; 21: 318-322.
• 7 Malenfant RC, Sod GA. In vitro biomechanical comparison of 3.5 string of pearl plate fixation to 3.5 locking compression plate fixation in a canine fracture gap model. Vet Surg 2014; 43: 465-470.
• 8 Ness MG. The effect of bending and twisting on the stiffness and strength of the 3.5 SOP implant. Vet Comp Orthop Traumatol 2009; 22: 132-136.
• 9 Cabassu JB, Kowaleski MP, Shorinko JK. Single cycle to failure in torsion of three standard and five locking plate constructs. Vet Comp Orthop Traumatol 2011; 24: 418-425.
• 10 Bouvier M, Hylander WL. In vivo bone strain on the dog tibia during locomotion. Acta Anatomica 1984; 118: 187-192.
• 11 Matushek KJ, Sumner-Smith G, Schatzker J. et al. A strain-gauge study of the effect of external fixation on the canine tibia. Arch Orthop Trauma Surg 1989; 108: 159-165.
• 12 Demner D, Garcia TC, Serdy MG. et al. Biomechanical comparison of mono- and bicortical screws in an experimentally induced gap fracture. Vet Comp Orthop Traumatol 2014; 27: 422-429.
• 13 Pearson T, Glyde M, Hosgood G. et al. The effect of intramedullary pin size and monocortical screw configuration on locking compression plate-rod constructs in an in vitro fracture gap model. Vet Comp Orthop Traumatol 2015; 28: 95-103.
• 14 Déjardin LM, Guillou R, Ting D. et al. Effect of bending direction on the mechanical behaviour of interlocking nail systems. Vet Comp Orthop Traumatol 2009; 22: 264-269.
• 15 Déjardin LM, Lansdowne JL, Sinnott MT. et al. In vitro mechanical evaluation of torsional loading in simulated canine tibiae for a novel hourglass-shaped interlocking nail with a self-tapping tapered locking design. Am J Vet Res 2006; 67: 678-685.
• 16 Lansdowne JL, Sinnott MT, Déjardin LM. et al. In vitro mechanical comparison of screwed, bolted, and novel interlocking nail systems to buttress plate fixation in torsion and mediolateral bending. Vet Surg 2007; 36: 368-377.
• 17 Boero Baroncelli A, Reif U, Bignardi C. et al. Effect of screw insertion torque on push-out and cantilever bending properties of five different angle-stable systems. Vet Surg 2013; 42: 308-315.
• 18 Goett SD, Sinnott MT, Ting D. et al. Mechanical comparison of an interlocking nail locked with conventional bolts to extended bolts connected with a type-IA external skeletal fixator in a tibial fracture model. Vet Surg 2007; 36: 279-286.
• 19 von Pfeil DJ, Déjardin LM, DeCamp CE. et al. In vitro biomechanical comparison of a plate-rod combination-construct and an interlocking nail-construct for experimentally induced gap fractures in canine tibiae. Am J Vet Res 2005; 66: 1536-1543.
• 20 Ting D, Cabassu JB, Guillou RP. et al. In vitro evaluation of the effect of fracture configuration on the mechanical properties of standard and novel interlocking nail systems in bending. Vet Surg 2009; 38: 881-887.
• 21 Bouvy BM, Markel MD, Chelikani S. et al. Ex vivo biomechanics of Kirschner-Ehmer external skeletal fixation applied to canine tibiae. Vet Surg 1993; 22: 194-207.
• 22 Stoffel K, Dieter U, Stachowiak G. et al. Biomechanical testing of the LCP - how can stability in locked internal fixators be controlled?. Injury 2003; 34: 11-19.
• 23 Ahmad M, Nanda R, Bajwa AS. et al. Biomechanical testing of the locking compression plate: When does the distance between bone and implant significantly reduce construct stability?. Injury 2007; 38: 358-364.
• 24 Gardner MJ, Brophy RH, Campbell D. et al. The mechanical behavior of locking compression plates compared with dynamic compression platesin a cadaver radius model. J Orthop Trauma 2005; 19: 597-603.
• 25 Miller EI, Acquaviva AE, Eisenmann DJ. et al. Perpendicular pull-out force of locking versus non-locking plates in thin cortical bone using a canine mandibular ramus model. Vet Surg 2011; 40: 870-874.
• 26 O’Toole RV, Andersen RC, Vesnovsky O. et al. Are locking screws advantageous with plate fixation of humeral shaft fractures? A biomechanical analysis of synthetic and cadaveric bone. J Orthop Trauma 2008; 22: 709-715.
• 27 Goh CS, Santoni BG, Puttlitz CM. et al. Comparison of the mechanical behaviors of semicontoured, locking plate-rod fixation and anatomically contoured, conventional plate-rod fixation applied to experimentally induced gap fractures in canine femora. Am J Vet Res 2009; 70: 23-29.
• 28 Acquaviva AE, Miller EI, Eisenmann DJ. et al. Biomechanical testing of locking and nonlocking plates in the canine scapula. J Am Anim Hosp Assoc 2012; 48: 372-378.
• 29 Irubetagoyena I, Verset M, Palierne S. et al. Ex vivo cyclic mechanical behaviour of 2.4 mm locking plates compared with 2.4 mm limited contact plates in a cadaveric diaphyseal gap model. Vet Comp Orthop Traumatol 2013; 26: 479-488.
• 30 Chao P, Conrad BP, Lewis DD. et al. Effect of plate working length on plate stiffness and cyclic fatigue life in a cadaveric femoral fracture gap model stabilized with a 12-hole 2.4 mm locking compression plate. BMC Veterinary Research 2013; 9: 125
• 31 Maxwell M, Horstman CL, Crawford RL. et al. The effects of screw placement on plate strain in 3.5 mm dynamic compression plates and limited-contact dynamic compression plates. Vet Comp Orthop Traumatol 2009; 22: 125-131.
• 32 El Haj M, Khoury A, Mosheiff R. et al. Orthogonal double plate fixation for long bone fracture nonunion. Acta Chir Orthop Traumatol Cech 2013; 80: 131-137.
• 33 Muller FJ, Galler M, Fuchtmeier B. Clinical and radiological results of patients treated with orthogonal double plating for periprosthetic femoral fractures. Int Orthop 2014; 38: 2469-2472.
• 34 Kosmopoulos V, Nana AD. Dual plating of humeral shaft fractures: orthogonal plates biomechanically outperform side-by-side plates. Clin Orthop Relat Res 2014; 472: 1310-1317.