The fatigue strength of small diameter tibial nails

doi:10.1016/S0020-1383(00)00219-9

Injury

Volume 32, Issue 5, June 2001, Pages 401-405

https://doi.org/10.1016/S0020-1383(00)00219-9 Get rights and content

Abstract

This study was performed to evaluate the fatigue strength of commonly used small diameter tibial nails.

Five types of small diameter tibial nails (7 mm aap Biorigid Nail®, 8 mm aap Biorigid Nail®, 8 mm Ace UTN®, 8 mm RT Tibial Nail®, 8 mm Synthes UTN®) with a sample size of 30 implants (six samples of each nail type) were tested with a new modular testing system. One module of the testing system was removed, simulating a 55-mm distal tibial defect, to induce maximum loading on the distal portion of the implant and locking bolts.

The average yield strengths were obtained from static, single cycle tests and revealed an average static ultimate load of 1072 N (aap7), 1820 N (aap8), 1812 N (Ace), 1942 N (R&T), and 1543 N (Syn). The fatigue limits were evaluated by cyclic, sinusoidal loading and revealed a fatigue strength of 750 N (aap7), 1092 N (aap8), 906 N (Ace), 971 N (R&T), and 771 N (Syn) to endure 500 000 cycles. Our results showed that the solid tibial nails fractured in the testing device in the same manner and location as they do in the clinical series.

This study showed that all the small diameter tibial nails tested are obviously able to transmit loads of more than average body weight. The fatigue strength of the implants is relatively high, which means that patients without bone defects could be mobilised with full weight bearing as tolerated by pain. However, according to the results of this study, early mobilisation with full weight bearing in a normal gait cycle can not be suggested in patients with segmental tibial fractures or fractures with defect zones.

Introduction

Fatigue strength is one of the most important material characteristics of small diameter nails used with an unreamed technique for stabilisation of tibial fractures with severe soft tissue damage. These statically locked tibial nails are load bearing devices, often used for extended periods of time, especially in tibial fractures with bone defects. However, they are temporary implants with a limited life expectancy under continuous dynamic stress loads. In cases of delayed and non-union mechanical fatigue failure due to dynamic stress is to be expected sooner or later [1].

This study was performed to evaluate the fatigue strength of commonly used small diameter tibial nails.

Section snippets

Material and methods

Five types of small diameter tibial nails (Table 1) were tested with a new modular testing system described earlier [2]. A sample size of 30 implants (six samples of each nail type) was tested. One module (module 2) of the testing system was removed (Fig. 1), simulating a 55 mm distal tibial defect, to induce maximum loading on the distal portion of the implant and locking bolts. The intramedullary fixation devices (IMFDs) were centred in the tube of the testing system by polyurethane washers

Single cycle loading

The results of the static, single cycle tests are presented in Table 2. The 8-mm implants aap8, ACE, and R&T showed similar failure levels. The implants reached their individual yield points (Fig. 2) under average loads of 1820, 1812, and 1942 N. The 8 mm Syn implants showed resistance against static ultimate load (SUL) of average double body weight (1540 N). The aap7 implant reached its individual yield points under an average load of 1072 N. It was obvious that all the five implant types

Discussion

Small diameter tibial nails have been developed for the stabilisation of tibial fractures with severe soft tissue injuries. However, there seems to be a growing enthusiasm in the trauma community for solid tibial nails inserted without reaming for stabilisation of all types of tibial fractures, fractures that could be easily stabilised with larger diameter nails inserted after reaming. Several authors have warned that the lower fatigue strength of these small diameter nails might result in a

Acknowledgements

This work was supported by funds of the Ludwig Boltzmann Institute for Biomechanics and Cell Biology, Vienna and by funds of the Society of Friends supporting the Scientific Research at the Trauma Centre, Vienna. We wish to express our gratitude to the companies aap Implants Inc., Ace Medical Company, Smith & Nephew and Mathys Austria Medical PLC for donating the small diameter tibial nails to be tested. We further wish to express our gratitude to A. Speitling of Stryker-Howmedica-Osteonics for

References (24)

J.B. Morrison
Mechanics of the knee in relation to normal walking
J. Biomech.
(1970)
A.C. Fairbank et al.
Stability of reamed and unreamed intramedullary tibial nails: a biomechanical study
Injury
(1995)
R.J. Eveleigh
A review of biomechanical studies of intramedullary nails
Med. Eng. Phys.
(1995)
Gaebler C, Berger U, Schandelmaier P, Greitbauer M, Schauwecker HH, Applegate B, Zych G, Vécsei V. Rates and odds...
Gaebler C, Speitling A, Milne EL, Stanzl-Tschegg S, Vécsei V, Latta LL. A new modular testing system for biomechanical...
J.J. Hutson et al.
Mechanical failures of intramedullary nails applied without reaming
Clin. Orthop.
(1995)
R.W. Boccardi et al.
Evaluation of muscular moments at the lower limb joints by an on-line processing of kinematic data and ground reaction
J. Biomech.
(1981)
D.G. Wright et al.
Action of the subtalar and ankle-joint complex during the stance of walking
J. Bone Jt. Surg.
(1964)
R.S. Adelaar
The practical biomechanics of running
Am. J. Sports Med.
(1986)
A.H. Burstein et al.
Fundamentals of Orthopaedic Biomechanics
(1994)

Milne EL, Latta LL. Biomechanical testing of tibial intramedullary devices. Internal memo...

Mueller ME, Allgoewer M, Schneider R, Willenegger, Manual of Internal Fixation, 3rd ed., Springer, Berlin,...

Cited by (13)

Comparison of fatigue strengths of biocompatible Ti-15Zr-4Nb-4Ta alloy and other titanium materials
2011, Materials Science and Engineering C
Citation Excerpt :
The results steered developments in Ti alloy innovation towards long-term high biocompatibility, excellent corrosion resistance, and fatigue strength. Fatigue is a type of damage often observed in implanted metals and is regarded as an important cause of orthopedic metal implant failure [9–16]. Chao et al. investigated the causes of in vivo fracture of a cementless Ti-6Al-4V alloy hip prosthesis.
The fatigue strength of an annealed Ti-15Zr-4Nb-4Ta alloy at 1 × 10⁸ cycles was approximately 730 MPa. The fatigue strength of its alloy was much improved following an ageing treatment after a solution treatment. The tension-to-tension fatigue strengths of annealed Ti-6Al-4V, V-free Ti-6Al-7Nb, Ti-6Al-2Nb-1Ta, and Ti-15Mo-5Zr-3Al alloys at 1 × 10⁸ cycles were approximately 685, 600, 700, and 350 MPa, respectively. The ratios of fatigue strength at 1 × 10⁸ cycles to ultimate tensile strength for the α- and (α + β)-type Ti materials were higher than 65%.
Material selection
2010, Metals for Biomedical Devices
Stiffness analysis of tibia-implant system under cyclic loading
2008, Materials Science and Engineering C
A testing method has been developed to characterize stiffness and permanent deformation of bone-implant systems. The system consists of an artificial tibia with simulated distal fracture stabilized by an unreamed intramedullary nail. This system was loaded with three different sequences at 2 Hz, each consisting of 40,000 sinusoidal cycles, simulating clinical relevant loading conditions. Evaluation of the results showed a stiffness of 2782 N/mm with a standard deviation of 311 N/mm and a permanent deformation of 0.64 mm with a standard deviation of 0.21 mm. The locking screws broke exclusively during the third loading sequence starting with the most proximal of the distal screws. The study provides a standard technique for biomechanical testing and a comparison of different bone/implant-systems avoiding the variability of cadaver bone tests.
Intramedullary nailing of tibial shaft fractures: Size matters
2016, Journal of Orthopaedic Trauma
Finite element analysis of mechanical properties of wooden club shaped and general screws with interlocking intramedullary nail
2014, 2014 IEEE International Conference on Mechatronics and Automation, IEEE ICMA 2014
Literature discrepancies in biomechanical loading of orthopedic trauma devices intended for lower extremities
2014, ASTM Special Technical Publication

View all citing articles on Scopus

View full text

The fatigue strength of small diameter tibial nails

Abstract

Introduction

Section snippets

Material and methods

Single cycle loading

Discussion

Acknowledgements

J. Biomech.

Injury

Med. Eng. Phys.

Mechanical failures of intramedullary nails applied without reaming

Clin. Orthop.

Evaluation of muscular moments at the lower limb joints by an on-line processing of kinematic data and ground reaction

J. Biomech.

Action of the subtalar and ankle-joint complex during the stance of walking

J. Bone Jt. Surg.

The practical biomechanics of running

Am. J. Sports Med.

Fundamentals of Orthopaedic Biomechanics