Mechanical performance in axial compression of a titanium polyaxial locking plate system in a fracture gap model

 

 Buy Article Permissions and Reprints

Summary

Objective: To evaluate the bending strength of the VetLOX^® polyaxial locking plate system.

Materials and methods: Thirty-five 3.5 mm 12-hole titanium VetLOX^® plates were used to stabilize seven different construct designs in a 1 cm fracture gap simulation model. Each construct was subjected to axial compression. Mean bending stiffness (BS) and yield load (YL) of each construct design were analysed using a one-way ANOVA and Tukey post-hoc analysis. Screw angulation was measured on reconstructed computed tomography (CT) images.

Results: Reducing plate working length for fixed-angle constructs significantly increased BS (p <0.01) and YL (p <0.01). For a constant plate working length, increasing screw number did not significantly affect BS (p = 1.0) or YL (p = 0.86). Screw angulation measurement technique was validated by intra-class correlation coefficients (ICC) (ICC >0.9 for inter- and intra-observer measurements). An average screw angle of 13.2° did not significantly affect mechanical performance although incomplete screw head-plate engagement was noted on some reconstructed CT images when angulation exceeded 10°. Prefabricated screw-head inserts did not significantly increase mechanical performance. A 4 mm bone-plate stand-off distance significantly reduced BS and YL by 63% and 69% respectively.

Clinical relevance: The VetLOX^® system allows the benefits of polyaxial screw insertion whilst maintaining comparable bending properties to fixed angle insertion. The authors recommend accurate plate contouring to reduce the risk of plate bending.

• References

• 1 Blake C, Boudrieau R, Torrance B. 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.
  Article in Thieme ConnectPubMedGoogle Scholar
• 2 Barnhart MD, Rides CF, Kennedy SC. et al. Fracture repair using a polyaxial locking plate system (PAX). Vet Surg 2013; 42: 60-66.
  CrossrefPubMedGoogle Scholar
• 3 Cabassu JB, Kowaleski MP, Shorinko JK. et al. Single cycle to failure in torsion of three standard and five locking plate constructs. Vet Comp Orthop Traumatol 2011; 24: 418-425.
  Article in Thieme ConnectPubMedGoogle Scholar
• 4 Rutherford S, Ness MG. Effect of contouring on bending structural stiffness and bending strength of the 3.5 titanium SOP implant. Vet Surg 2012; 41: 983-987.
  CrossrefPubMedGoogle Scholar
• 5 Egol KA, Kubiak EN, Fulkerson E. et al. Biomechanics of locked plates and screws. J Orthop Trauma 2004; 18: 488-493.
  CrossrefPubMedGoogle Scholar
• 6 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.
  CrossrefPubMedGoogle Scholar
• 7 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.
  CrossrefPubMedGoogle Scholar
• 8 Greiwe RM, Archdeacon MT. Locking plate technology: current concepts. J Knee Surg 2007; 20: 50-55.
  Article in Thieme ConnectPubMedGoogle Scholar
• 9 Gautier E, Sommer C. Guidelines for the clinical application of the LCP. Injury 2003; 34 Suppl (Suppl. 02) B63-76.
  CrossrefPubMedGoogle Scholar
• 10 Johnson A. Current concepts in fracture reduction. Vet Comp Orthop Traumatol 2003; 16: 59-66.
  Article in Thieme ConnectPubMedGoogle Scholar
• 11 Hulse D, Hyman W, Nori M. et al. Reduction in plate strain by addition of an intramedullary pin. Vet Surg 1997; 26: 451-459.
  CrossrefPubMedGoogle Scholar
• 12 Bellapianta J, Dow K, Pallotta NA. et al. Threaded screw head inserts improve locking plate biomechanical properties. J Orthop Trauma 2011; 25: 65-71.
  CrossrefPubMedGoogle Scholar
• 13 Schmokel HG, Stein S, Radke H. et al. Treatment of tibial fractures with plates using minimally invasive percutaneous osteosynthesis in dogs and cats. J Small Anim Pract 2007; 48: 157-160.
  CrossrefPubMedGoogle Scholar
• 14 Guiot LP, Dejardin LM. Prospective evaluation of minimally invasive plate osteosynthesis in 36 nonarticular tibial fractures in dogs and cats. Vet Surg 2011; 40: 171-182.
  CrossrefPubMedGoogle Scholar
• 15 Hoffmeier KL, Hofmann GO, Muckley T. Choosing a proper working length can improve the lifespan of locked plates. A biomechanical study. Clin Biomech (Bristol, Avon) 2011; 26: 405-409.
  CrossrefPubMedGoogle Scholar
• 16 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 Vet Res 2013; 91: 125.
  PubMedGoogle Scholar
• 17 Miller DL, Goswami T. A review of locking compression plate biomechanics and their advantages as internal fixators in fracture healing. Clin Biomech (Bristol, Avon) 2007; 22: 1049-1062.
  CrossrefPubMedGoogle Scholar
• 18 ASTM International. Standard Specification and Test Method for Metallic Bone Plates. West Conshohocken F382-99: ASTM International 2008
  PubMedGoogle Scholar
• 19 Filipowicz D, Lanz O, McLaughlin R. et al. A biomechanical comparison of 3.5 locking compression plate fixation to 3.5 limited contact dynamic compression plate fixation in a canine cadaveric distal humeral metaphyseal gap model. Vet Comp Orthop Traumatol 2009; 22: 270-277.
  PubMedGoogle Scholar
• 20 Reaugh HF, Rochat MC, Bruce CW. et al. Stiffness of modified Type 1a linear external skeletal fixators. Vet Comp Orthop Traumatol 2007; 20: 264-268.
  Article in Thieme ConnectPubMedGoogle Scholar
• 21 Hudson CC, Lewis DD, Cross AR. et al. A biomechanical comparison of three hybrid linear-circular external fixator constructs. Vet Surg 2012; 41: 954-965.
  CrossrefPubMedGoogle Scholar
• 22 Deiss R, Bali MS, Doherr M. et al. In vitro biomechanical testing of a micro external skeletal fixator. Vet Comp Orthop Traumatol 2013; 26: 385-391.
  Article in Thieme ConnectPubMedGoogle Scholar
• 23 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.
  Article in Thieme ConnectPubMedGoogle Scholar
• 24 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.
  Article in Thieme ConnectPubMedGoogle Scholar
• 25 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.
  Article in Thieme ConnectPubMedGoogle Scholar
• 26 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.
  CrossrefPubMedGoogle Scholar
• 27 Ellis T, Bourgeault CA, Kyle RF. Screw position affects dynamic compression plate strain in an in vitro fracture model. J Orthop Trauma 2001; 15: 333-337.
  CrossrefPubMedGoogle Scholar
• 28 Fulkerson E, Egol KA, Kubiak EN. et al. Fixation of diaphyseal fractures with a segmental defect: a biomechanical comparison of locked and conventional plating techniques. J Trauma 2006; 60: 830-835.
  CrossrefPubMedGoogle Scholar
• 29 Bufkin BW, Barnhart MD, Kazanovicz AJ. et al. The effect of screw angulation and insertion torque on the push-out strength of polyaxial locking screws and the single cycle to failure in bending of polyaxial locking plates. Vet Comp Orthop Traumatol 2013; 26: 186-191.
  Article in Thieme ConnectPubMedGoogle Scholar
• 30 Hebert-Davies J, Laflamme GY, Rouleau D. et al. A biomechanical study comparing polyaxial locking screw mechanisms. Injury 2013; 44: 1358-1362.
  CrossrefPubMedGoogle Scholar