Investigation into factors affecting the mechanical behaviours of a patient-specific vertebral body replacement

Abstract

Most vertebral body implants that are currently designed and produced in batches have difficulty meeting the patient-specific demands. Moreover, several complications, including a low fusion rate, subsidence occurrence, and rod displacement, are associated with these implants. This study aims to investigate the effects of patient-specific geometric and clinical parameters on the biomechanics of a vertebral body replacement. A three-dimensional patient-specific vertebral body replacement model was established as the basic model for parametric studies, including the anatomic design of the endplates, tilting angle, thickness, and dislocation of the vertebral body implant. A finite element analysis was applied to determine the stress distribution of the vertebral body implant when under various loading conditions. The model with an anatomical interfacing design generates 75% less stress concentration compared to a flat design; the peak stress of the model with a tilted angle closely matching the replaced vertebra segment is decreased by 30%; and the thickness close to the cortical bone can offer better bone growth capability and long-term stability. Patient-specific geometrical parameters were found to significantly affect the biomechanics of a vertebral body replacement, and therefore, a design customized especially for the endplates is necessary for better stability and long-term longevity of the prostheses. Regardless of such progress, how to balance the stability of a vertebral body implant and the safety of the peripheral nervous system remains a clinical challenge.

Keywords

Vertebral body replacement patient-specific design subsidence bone graft fusion finite element analysis

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References

De Beer

Van der Merwe

. Patient-specific intervertebral disc implants using rapid manufacturing technology. Rapid Prototyping J 2013; 19: 126–139.

Behrbalk

Uri

Parks

et al . Fusion and subsidence rate of stand alone anterior lumbar interbody fusion using PEEK cage with recombinant human bone morphogenetic protein-2. Eur Spine J 2013; 22: 2869–2875.

Choi

Sung

KH.

Subsidence after anterior lumbar interbody fusion using paired stand-alone rectangular cages. Eur Spine J 2006; 15: 16–22.

Kanayama

Hashimoto

Shigenobu

et al . Pitfalls of anterior cervical fusion using titanium mesh and local autograft. J Spinal Disord Tech 2003; 16: 513–518.

Van der Houwen

Baron

Veldhuizen

et al . Geometry of the intervertebral volume and vertebral endplates of the human spine. Ann Biomed Eng 2010; 38: 33–40.

Lian

Jin

et al . Patient-specific design and biomechanical evaluation of a novel bipolar femoral hemi-knee prosthesis. J Bionic Eng 2014; 11: 259–267.

De Beer

Scheffer

. Reducing subsidence risk by using rapid manufactured patient-specific intervertebral disc implants. Spine J 2012; 12: 1060–1066.

Bahraminasab

Sahari

Edwards

et al . Multi-objective design optimization of functionally graded material for the femoral component of a total knee replacement. Mater Design 2014; 53: 159–173.

Zhong

Chen

Hung

CH.

Load- and displacement-controlled finite element analyses on fusion and non-fusion spinal implants. Proc IMechE, Part H: J Engineering in Medicine 2009; 223: 143–157.

10.

Wilcox

RK.

The biomechanical effect of vertebroplasty on the adjacent vertebral body: a finite element study. Proc IMechE, Part H: J Engineering in Medicine 2006; 220: 565–572.

11.

Noailly

Wilke

Planell

et al . How does the geometry affect the internal biomechanics of a lumbar spine bi-segment finite element model? Consequences on the validation process. J Biomech 2007; 40: 2414–2425.

12.

Yamamoto

Panjabi

Crisco

et al . Three-dimensional movements of the whole lumbar spine and lumbosacral joint. Spine 1989; 14: 1256–1260.

13.

Yang

Teo

Fuss

FK.

Application of Taguchi method in optimization of cervical ring cage. J Biomech 2007; 40: 3251–3256.

14.

Tan

Bailey

Dvorak

et al . Interbody device shape and size are important to strengthen the vertebra-implant interface. Spine 2005; 30: 638–644.

15.

Lowe

Hashim

Wilson

et al . A biomechanical study of regional endplate strength and cage morphology as it relates to structural interbody support. Spine 2004; 29: 2389–2394.

16.

Rohlmann

Zander

Bock

et al . Effect of position and height of a mobile core type artificial disc on the biomechanical behaviour of the lumbar spine. Proc IMechE, Part H: J Engineering in Medicine 2008; 222: 229–239.

17.

Pearcy

Evans

O’Brien

JP.

The load bearing capacity of vertebral cancellous bone in interbody fusion of the lumbar spine. Eng Med 1983; 12: 183–184.

18.

Closkey

Parsons

Lee

et al . Mechanics of interbody spinal fusion. Analysis of critical bone graft area. Spine 1993; 18: 1011–1015.

19.

Wang

Zhang

Sadeghipour

et al . Effect of posterolateral disc replacement on kinematics and stress distribution in the lumbar spine: a finite element study. Med Eng Phys 2013; 35: 357–364.

20.

Xiao

Wang

Gong

et al . Establishment and verification of a non-linear finite element model for human L4–L5 lumbar segment. In: Proceedings of the 2010 3rd international conference on biomedical engineering and informatics, Yantai, China, 16–18 October 2010. New York: IEEE.

21.

Zhao

Wang

Chen

et al . Finite element analysis of minimal invasive transforaminal lumbar interbody fusion. Cell Biochem Biophys 2014; 70: 609–613.

22.

Erbulut

Zafarparandeh

Hassan

et al . Determination of the biomechanical effect of an interspinous process device on implanted and adjacent lumbar spinal segments using a hybrid testing protocol: a finite-element study. J Neurosurg Spine 2015; 23: 200–208.

23.

Coe

JD.

Instrumented transforaminal lumbar interbody fusion with bioabsorbable polymer implants and iliac crest autograft. Neurosurg Focus 2004; 16: E11.

24.

Schlösser

TPC

Shah

Reichard

et al . Differences in early sagittal plane alignment between thoracic and lumbar adolescent idiopathic scoliosis. Spine J 2014; 14: 282–290.

25.

Rohlmann

Zander

Bergmann

Effects of fusion-bone stiffness on the mechanical behavior of the lumbar spine after vertebral body replacement. Clin Biomech 2006; 21: 221–227.

26.

Dreischarf

Shirazi-Adl

Arjmand

et al . Estimation of loads on human lumbar spine: a review of in vivo and computational model studies. J Biomech 2016; 49: 833–845.

27.

Weinbaum

Cowin

Zeng

A model for the excitation of osteocytes by mechanical loading-induced bone fluid shear stresses. J Biomech 1994; 27: 339–360.

28.

Corniola

Jägersberg

Stienen

et al . Complete cage migration/subsidence into the adjacent vertebral body after posterior lumbar interbody fusion. J Clin Neurosci 2015; 22: 597–598.

29.

Chuah

Abd Rahim

Yusof

MI.

Topology optimisation of spinal interbody cage for reducing stress shielding effect. Comput Methods Biomech Biomed Engin 2010; 13: 319–326.

30.

Denoziere

DN.

Biomechanical comparison between fusion of two vertebrae and implantation of an artificial intervertebral disc. J Biomech 2006; 39: 766–775.

31.

Polikeit

Ferguson

Nolte

et al . The importance of the endplate for interbody cages in the lumbar spine. Eur Spine J 2003; 12: 556–561.

32.

Agarwal

Palepu

Agarwal

et al . Biomechanical evaluation of an endplate-conformed polycaprolactone-hydroxyapatite intervertebral fusion graft and its comparison with a typical nonconformed cortical graft. J Biomech Eng 2013; 135: 61005–61009.

33.

Chen

Chiang

Lin

et al . Biomechanical comparison of three stand-alone lumbar cages – a three-dimensional finite element analysis. BMC Musculoskelet Disord 2013; 14: 281.

34.

Pizanis

Holstein

Vossen

et al . Compression and contact area of anterior strut grafts in spinal instrumentation: a biomechanical study. BMC Musculoskelet Disord 2013; 14: 254.