- •Screw hole merging could markedly enhance fatigue lives of locking plates.
- •Partial thread removal could significantly increase the fatigue lives of plates.
- •Removing 1/3 of threads in merged hole does not affect the screw's holding power.
- •Offset holes in locking plates can reduce fatigue lives significantly.
This study investigated the effects of screw hole merging, thread removal, and screw hole offset on the mechanical properties of locking plates.
Finite element models were used to develop the optimal design of the merged holes. Four titanium locking plates with different hole designs were analyzed. Type I had threaded round holes. Type II had merged holes. Type III had merged holes with partial thread removal. Type IV had threaded offset holes. Mechanical experiments similar to finite element analyses were conducted and compared. Screw bending tests were used to assess the screw holding power.
Finite element analyses showed the optimal merging distance between two round screw holes was 3.5 mm with 2/3 circumferences in each hole. The stresses of types II and III were respectively 6.42% and 7.33%, lower than that of type I. The stress of type IV was 1.66% higher than that of type I. In the mechanical tests, the fatigue lives of types II and III were respectively 3.86 and 7.16 times higher than that of type I. The fatigue life of type IV was 37% lower than that of type I. The differences in the bending strengths of screws were insignificant.
Merging holes could mitigate screw hole stress and increase the fatigue lives of the plates significantly. Partial thread removal could further improve the fatigue life. Merging holes and thread removal did not decrease the screw holding power significantly. The fatigue lives were significantly decreased in plates with offset holes.
To read this article in full you will need to make a payment
Purchase one-time access:Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
One-time access price info
- For academic or personal research use, select 'Academic and Personal'
- For corporate R&D use, select 'Corporate R&D Professionals'
Subscribe:Subscribe to Clinical Biomechanics
Already a print subscriber? Claim online access
Already an online subscriber? Sign in
Register: Create an account
Institutional Access: Sign in to ScienceDirect
- Computer-aided engineering approach for parametric investigation of locked plating systems design.J. Med. Devices. 2013; 7021001https://doi.org/10.1115/1.4024644
- Biomechanical testing of distal femur osteotomy plate fixation techniques: the role of simulated physiological loading.J. Exp. Orthop. 2014; 1: 1https://doi.org/10.1186/s40634-014-0001-1
- Half-threaded holes markedly increase the fatigue life of locking plates without compromising screw stability.Bone Jt. Res. 2020; 9: 645-652https://doi.org/10.1302/2046-3758.910.bjr-2019-0237.r2
- Contradictory working length effects in locked plating of the distal and middle femoral fractures—A biomechanical study.Clin. Biomech. 2020; 80105198https://doi.org/10.1016/j.clinbiomech.2020.105198
- Mechanical performance of the new posterior spinal implant: effect of materials, connecting plate, and pedicle screw design.Spine. 2003; 28: 881-886https://doi.org/10.1097/01.brs.0000058718.38533.b8
- Notch sensitivity of titanium alloy, commercially pure titanium, and stainless steel spinal implants.Spine. 2001; 26: 1668-1672https://doi.org/10.1097/00007632-200108010-00008
- Guidelines for the clinical application of the LCP.Injury. 2003; 34: 63-76https://doi.org/10.1016/j.injury.2003.09.026
- Why and how do locking plates fail?.Injury. 2018; 49: S56-S60https://doi.org/10.1016/s0020-1383(18)30305-x
- The use of titanium and stainless steel in fracture fixation.Expert Rev. Med. Devices. 2010; 7: 843-853https://doi.org/10.1586/erd.10.53
- Clinical outcomes of locked plating of distal femoral fractures in a retrospective cohort.J. Orthop. Surg. Res. 2013; 8: 43https://doi.org/10.1186/1749-799x-8-43
- Choosing a proper working length can improve the lifespan of locked plates. A biomechanical study.Clin. Biomech. 2011; 26: 405-409https://doi.org/10.1016/j.clinbiomech.2010.11.020
- Notch sensitivity of titanium causing contradictory effects on locked nails and screws.Med. Eng. Phys. 2010; 32: 454-460https://doi.org/10.1016/j.medengphy.2010.03.006
- Screw head plugs increase the fatigue strength of stainless steel, but not of titanium, locking plates.Bone Jt. Res. 2018; 7: 629-635https://doi.org/10.1302/2046-3758.712.bjr-2018-0083.r1
- Locked internal fixator: sensitivity of screw/plate stability to the correct insertion angle of the screw.J. Orthop. Trauma. 2004; 18: 483-487https://doi.org/10.1097/00005131-200409000-00002
- Fatigue failure of an orthopedic implant – a locking compression plate.Eng. Fail. Anal. 2008; 15: 521-530https://doi.org/10.1016/j.engfailanal.2007.04.001
- Stiffness and endurance of a locking compression plate fixed on fractured femur.J. Appl. Biomech. 2010; 26: 10-16https://doi.org/10.1123/jab.26.1.10
- Modification of the screw hole structures to improve the fatigue strength of locking plates.Clin. Biomech. 2018; 54: 71-77https://doi.org/10.1016/j.clinbiomech.2018.03.011
- Surgical treatment of peri-prosthetic femur fractures with dedicated NCB plates: our experience.Acta Biomed. 2020; 91: 297-304https://doi.org/10.23750/abm.v91i2.8608
- Stress concentration and its mitigation techniques in flat plate with singularities—A critical review.Engl. J. 2012; 16: 1-16https://doi.org/10.4186/ej.2012.16.1.1
- Mitigation curves for determination of relief holes to mitigate stress concentration factor in thin plates loaded axially for different discontinuities.Int. J. Eng. Innov. Technol. 2012; 2: 1-7
- Mitigating stress concentration through defense hole system for improvement in bearing strength of composite bolted joint, part 1: numerical analysis.J. Compos. Mater. 2017; 51: 3685-3699https://doi.org/10.1177/0021998317692396
- Locking plates: tips and tricks.J. Bone Jt. Surg. 2007; 89: 2298-2307https://doi.org/10.2106/00004623-200710000-00028
- Locking compression plate loosening and plate breakage.J. Orthop. Trauma. 2004; 18: 571-577https://doi.org/10.1097/00005131-200409000-00016
- Biomechanical assessment of titanium and stainless steel posterior spinal constructs: effects of absolute/relative loading and frequency on fatigue life and determination of failure modes.J. Spinal Disord. 1997; 10 (PMID: 9438811): 473-481
- The current status of locked plating: the good, the bad, and the ugly.J. Orthop. Trauma. 2008; 22: 479-486https://doi.org/10.1097/BOT.0b013e31817996d6
- Notch sensitivity jeopardizes titanium locking plate fatigue strength.Injury. 2016; 47: 2726-2732https://doi.org/10.1016/j.injury.2016.09.036
- Biomechanical comparison of two angular stable plate constructions for periprosthetic femur fracture fixation.Int. Orthop. 2014; 38: 47-53https://doi.org/10.1007/s00264-013-2113-0
- Topology optimization of rectangular plate having central circular hole & provision of auxiliary holes to reduce SCF.Int. Res. J. Eng. Technol. 2016; 3: 1084-1087
Published online: May 06, 2022
Accepted: May 3, 2022
Received: January 6, 2022
© 2022 Elsevier Ltd. All rights reserved.