Biomechanical comparison of gourd-shaped LCP versus LCP for fixation of comminuted tibial shaft fracture

Abstract

The purpose of this study was to compare monotonic biomechanical properties of gourd-shaped LCP fixation with LCP fixation of human tibial shaft in gap fracture mode. Twenty paired fresh cadaveric human tibias were randomly divided into 4 groups (5 pairs each): (1) axial loading single cycle to failure testing, (2) torsion single cycle to failure testing, (3) 4-point bending single cycle to failure testing, and (4) dynamic 4-point bending testing. A 7-hole 4.5 mm gourd-shaped LCP was secured on the anteromedial surface of 1 randomly selected bone from each pair, respectively, using 6 locking screws in the 1st, 2nd, 3rd, 5th, 6th and 7th hole with the middle hole unfilled and just located at the mid-diaphysis of the tibia. A 7-hole 4.5 mm LCP was secured on the other bone with the same method. Standard AO/ASIF techniques were used. After fixation finished, a 10 mm gap in the mid-diaphysis of tibia was created, centrally located at the unfilled hole. The axial, torsional, and bending stiffness and failure strengths were calculated from the collected data in static testings and statistically compared using paired Student’s t-test. The 4-point bending fatigue lives of the two constructs were calculated from the dynamic testing data and also statistically compared using paired Student’s t-test. Failure modes were recorded and visually analyzed. P<0.05 was considered significant. Results showed that the axial, torsional and bending stiffness of gourd-shaped LCP construct was greater (4%, 19%, 12%, respectively, P<0.05) than that of the LCP construct, and the axial, torsional and bending failure strengths of gourd-shaped LCP construct were stronger (10%, 46%, 29%, respectively, P<0.05) than those of the LCP construct. Both constructs failed as a result of plate plastic torsional deformation. After axial loading and 4-point bending testings, LCP failed in term of an obvious deformation of bent apex just at the unfilled plate hole, while the gourd-shaped LCP failed in term of a deformation of bent arc between the 3rd and 5th holes, which indicated a more consistent stress distribution on gourd-shaped LCP. Fatigue life of gourd-shaped LCP construct was significantly greater than LCP construct (153 836±2 228 vs. 132 471±6 460 cycles, P<0.01). All constructs failed as a result of fracture of the plate through the compression hole of the unfilled combination screw hole. The biomechanical testing showed that gourd-shaped LCP can provide greater stiffness and strength, and longer fatigue life than LCP. The gourd-shaped LCP may be more advantageous mechanically and may reduce the plate breakage rate clinically.

Keywords

tibial fracture / biomechanics / locking compression plate / fatigue

References

[1] FriggR. Locking compression plate (LCP). An osteosynthesis plate based on the dynamic compression plate and the point contact fixator (PC-Fix). Injury, 2001, 32(Suppl2): 63-66

[2] WagnerM, FriggR. Locking compression plate (LCP): Ein neuer AO-Standard. OP J, 2000, 16(3): 238-243

[3] FlorinM, ArzdorfM, LinkeB, et al.. Assessment of stiffness and strength of 4 different implants available for equine fracture treatment: a study on a 20 degrees oblique long bone fracture model using a bone substitute. Vet Surg, 2005, 34(3): 231-238

[4] SommerC, GautierE, MüllerM, et al.. First clinical results of the locking compression plate (LCP). Injury, 2003, 34(Suppl2): 43-54

[5] SommerC, BabstR, MüllerM, et al.. Locking compression plate loosening and plate breakage: a report of four cases. J Orthop Trauma, 2004, 18(8): 571-577

[6] GreenE, LubahnJD, EvansJ. Risk factors, treatment, and outcomes associated with nonunion of the midshaft humerus fracture. J Surg Orthop Adv, 2005, 14(2): 64-72

[7] GandhiA, LiporaceF, AzadV, et al.. Diabetic fracture healing. Foot Ankle Clin, 2006, 11(4): 805-824

[8] BrunnerH, SimpsonJP. Fatigue fracture of bone plates. Injury, 1980, 11(3): 203-207

[9] VallierHA, HennesseyTA, SontichJK, et al.. Failure of LCP condylar plate fixation in the distal part of the femur: a report of six cases. J Bone Joint Surg [Am], 2006, 88(4): 846-853

[10] YukataK, DoiK, HattoriY, et al.. Early breakage of a titanium volar locking plate for fixation of a distal radius fracture: case report. J Hand Surg Am, 2009, 34(5): 907-909

[11] CartnerJL, MessinaA, BakerC, et al.. Does insertion torque affect the mechanics of locking hole inserts and fatigue performance of bridge plate constructs?. Bone Joint Sci, 2011, 2(3): 1-4

[12] RuediTP, MurphyWM. . AO principles of fracture management, 2000, Stuttgart New York, Thieme Verlag, 139-230

[13] AhmadM, NandaR, BajwaAS, et al.. Biomechanical testing of the locking compression plate: when does the distance between bone and implant significantly reduce construct stability?. Injury, 2007, 38(3): 358-364

[14] OzkayaN, NordinM. . Fundamentals of Biomechanics, Equilibrium, Motion, and Deformation, 1991, New York, NY, Van Nostrand Reinhold, 277-278

[15] BrinkerWO, OlmsteadML, Sumner-SmithG, et al.. . Manual of Internal Fixation in Small Animals, 19982nd ed.Berlin, Germany, Springer-Verlag, 1-289

[16] ScottP, ElizabethG, RobertoE. Fatigue analysis of plates used for fracture stabilization in small dogs and cats. Vet Surg, 2006, 35(6): 573-578

[17] KanchanomaiC, PhiphobmongkolV, MuanjanP. Fatigue failure of an orthopedic implant-A locking compression plate. Eng Failure Anal, 2008, 15(5): 521-530

[18] HoffmeierKL, HofmannGO, MückleyT. Choosing a proper working length can improve the lifespan of locked plates: A biomechanical study. Clin Biomech (Bristol, Avon), 2011, 26(4): 405-409

[19] BellapiantaJ, DowK, PallottaNA, et al.. Threaded screw head inserts improve locking plate biomechanical properties. J Orthop Trauma, 2011, 25(2): 65-71

[20] DumbletonJH, BlackJ. BlackJ, DumbletonJH. Principles of mechanics. Clinical biomechanics: a case history approach, 1981, New York, Churchill Livingstone, 359-400

[21] TencerAF, JohnsonKD, KyleRF, et al.. Biomechanics of fractures and fracture fixation. Instr Course Lect, 1993, 42: 19-55

[22] SeideK, TriebeJ, FaschingbauerM. Locked vs. unlocked plate osteosynthesis of the proximal humerus-a biomechanical study. Clin Biomech (Bristol, Avon), 2007, 22(2): 176-182

[23] RoeS. . Internal Fracture Fixation: Textbook of Small Animal Surgery, 20033rd edPhiladelphia, PA, Saunders, 1798-1881

[24] SodGA. . Numerical Methods in Fluid Dynamics: Initial and Initial Boundary-value Problems, 1986, Cambridge, UK, Cambridge University Press, 321

[25] PerrenSM. Evolution of the internal fixation of long bone fractures. The scientific basis of biological internal fixation: choosing a new balance between stability and biology. J Bone Joint Surg [Br], 2002, 84(8): 1093-1110

[26] EgolKA, KubiakEN, FulkersonE, et al.. Biomechanics of locked plates and screws. J Orthop Trauma, 2004, 18(8): 488-493

[27] PerrenSM. Backgrounds of the technology of internal fixators. Injury, 2003, 34(Suppl2): B1-B3

[28] GiannoudisPV, EinhornTA, MarshD. Fracture healing: the diamond concept. Injury, 2007, 38(Suppl4): S3-S6

[29] EpariDR, KassiJP, SchellH, et al.. Timely fracture-healing requires optimization of axial fixation stability. J Bone Joint Surg [Am], 2007, 89(7): 1575-1585

[30] FiroozabadiR, McDonaldE, NguyenT-Q, et al.. Does plugging unused combination screw holes improve the fatigue life of fixation with locking plates in comminuted supracondylar fractures of the femur?. J Bone Joint Surg [Br], 2012, 94(2): 241-248

[31] WheelerKR, JamesLA. Fatigue behavior of type 316 stainless steel under simulated body conditions. J Biomed Mater Res, 1971, 5(3): 267-281

[32] BrunnerH, SimpsonJP. Fatigue fracture of bone plates. Injury, 1980, 11(3): 203-207

[33] DawsonDB, PellouxRM. Corrosion fatigue crack growth of titanium alloys in aqueous environments. Metallurg Trans, 1974, 5(3): 723-731