Alteration of load sharing of anterior cervical implants with change in cervical sagittal alignment

Mei Wang, Krishnaj Gourab, Linda M. McGrady, Raj D. Rao

Research output: Contribution to journalArticle

Abstract

Anterior cervical discectomy and fusion (ACDF) is often supplemented with the application of an anterior plate to improve the stability of the fusion segment. While plate design has been shown to influence stress shielding of the graft, little is known about how the kyphotic alignment of a fused cervical segment affects the load sharing between the anterior plate and the osteoligamentous structures of the spine. The aim of this study was to characterize load sharing between an anterior plate and the osteoligamentous structures of the cervical motion segments in kyphotic versus normal lordotic alignment following single-level ACDF using fresh ovine cervical spines (C3-C6). The loading protocol involved preloading the spine with a 20 N compressive force and applying quasi-static moments (up to 2.1 Nm) in the sagittal plane to simulate flexion and extension. Stiffness of the fusion segment was measured from the moment-rotation plot. Normal lordotic alignment was replicated by insertion of a fibular allograft 2 mm taller than the interbody space. Kyphotic alignment was simulated by removing the graft and reapplying a shorter anterior cervical plate. The average segmental sagittal angulation at C4-C5 was 5.2 ± 1.6° of lordosis for the normal lordotic group and 6.8 ± 2.3° of kyphosis for the kyphotic group. With flexion, the plate shared 52.8% of the applied load in the normal lordotic group, and 70.1% in the kyphotic group (p <0.03). In extension, the amount of load-share by the plate in the normal lordotic group was comparable to that of the kyphotic group (52.7% vs. 40.7%, p = 0.16). This study shows that kyphotic alignment of the cervical fusion segment increases the load sharing of the anterior plate under flexion loading.

Original languageEnglish (US)
Pages (from-to)768-773
Number of pages6
JournalMedical Engineering and Physics
Volume30
Issue number6
DOIs
StatePublished - Jul 2008
Externally publishedYes

Fingerprint

Diskectomy
Spine
Fusion reactions
Transplants
Lordosis
Kyphosis
Grafts
Allografts
Sheep
Shielding
Stiffness

Keywords

  • Anterior cervical discectomy and fusion
  • Cervical plating
  • Kyphosis
  • Load sharing
  • Ovine model

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Psychology(all)

Cite this

Alteration of load sharing of anterior cervical implants with change in cervical sagittal alignment. / Wang, Mei; Gourab, Krishnaj; McGrady, Linda M.; Rao, Raj D.

In: Medical Engineering and Physics, Vol. 30, No. 6, 07.2008, p. 768-773.

Research output: Contribution to journalArticle

Wang, Mei ; Gourab, Krishnaj ; McGrady, Linda M. ; Rao, Raj D. / Alteration of load sharing of anterior cervical implants with change in cervical sagittal alignment. In: Medical Engineering and Physics. 2008 ; Vol. 30, No. 6. pp. 768-773.
@article{ea4b5e6332fa4016bcd7ee021bcf64db,
title = "Alteration of load sharing of anterior cervical implants with change in cervical sagittal alignment",
abstract = "Anterior cervical discectomy and fusion (ACDF) is often supplemented with the application of an anterior plate to improve the stability of the fusion segment. While plate design has been shown to influence stress shielding of the graft, little is known about how the kyphotic alignment of a fused cervical segment affects the load sharing between the anterior plate and the osteoligamentous structures of the spine. The aim of this study was to characterize load sharing between an anterior plate and the osteoligamentous structures of the cervical motion segments in kyphotic versus normal lordotic alignment following single-level ACDF using fresh ovine cervical spines (C3-C6). The loading protocol involved preloading the spine with a 20 N compressive force and applying quasi-static moments (up to 2.1 Nm) in the sagittal plane to simulate flexion and extension. Stiffness of the fusion segment was measured from the moment-rotation plot. Normal lordotic alignment was replicated by insertion of a fibular allograft 2 mm taller than the interbody space. Kyphotic alignment was simulated by removing the graft and reapplying a shorter anterior cervical plate. The average segmental sagittal angulation at C4-C5 was 5.2 ± 1.6° of lordosis for the normal lordotic group and 6.8 ± 2.3° of kyphosis for the kyphotic group. With flexion, the plate shared 52.8{\%} of the applied load in the normal lordotic group, and 70.1{\%} in the kyphotic group (p <0.03). In extension, the amount of load-share by the plate in the normal lordotic group was comparable to that of the kyphotic group (52.7{\%} vs. 40.7{\%}, p = 0.16). This study shows that kyphotic alignment of the cervical fusion segment increases the load sharing of the anterior plate under flexion loading.",
keywords = "Anterior cervical discectomy and fusion, Cervical plating, Kyphosis, Load sharing, Ovine model",
author = "Mei Wang and Krishnaj Gourab and McGrady, {Linda M.} and Rao, {Raj D.}",
year = "2008",
month = "7",
doi = "10.1016/j.medengphy.2007.10.004",
language = "English (US)",
volume = "30",
pages = "768--773",
journal = "Medical Engineering and Physics",
issn = "1350-4533",
publisher = "Elsevier BV",
number = "6",

}

TY - JOUR

T1 - Alteration of load sharing of anterior cervical implants with change in cervical sagittal alignment

AU - Wang, Mei

AU - Gourab, Krishnaj

AU - McGrady, Linda M.

AU - Rao, Raj D.

PY - 2008/7

Y1 - 2008/7

N2 - Anterior cervical discectomy and fusion (ACDF) is often supplemented with the application of an anterior plate to improve the stability of the fusion segment. While plate design has been shown to influence stress shielding of the graft, little is known about how the kyphotic alignment of a fused cervical segment affects the load sharing between the anterior plate and the osteoligamentous structures of the spine. The aim of this study was to characterize load sharing between an anterior plate and the osteoligamentous structures of the cervical motion segments in kyphotic versus normal lordotic alignment following single-level ACDF using fresh ovine cervical spines (C3-C6). The loading protocol involved preloading the spine with a 20 N compressive force and applying quasi-static moments (up to 2.1 Nm) in the sagittal plane to simulate flexion and extension. Stiffness of the fusion segment was measured from the moment-rotation plot. Normal lordotic alignment was replicated by insertion of a fibular allograft 2 mm taller than the interbody space. Kyphotic alignment was simulated by removing the graft and reapplying a shorter anterior cervical plate. The average segmental sagittal angulation at C4-C5 was 5.2 ± 1.6° of lordosis for the normal lordotic group and 6.8 ± 2.3° of kyphosis for the kyphotic group. With flexion, the plate shared 52.8% of the applied load in the normal lordotic group, and 70.1% in the kyphotic group (p <0.03). In extension, the amount of load-share by the plate in the normal lordotic group was comparable to that of the kyphotic group (52.7% vs. 40.7%, p = 0.16). This study shows that kyphotic alignment of the cervical fusion segment increases the load sharing of the anterior plate under flexion loading.

AB - Anterior cervical discectomy and fusion (ACDF) is often supplemented with the application of an anterior plate to improve the stability of the fusion segment. While plate design has been shown to influence stress shielding of the graft, little is known about how the kyphotic alignment of a fused cervical segment affects the load sharing between the anterior plate and the osteoligamentous structures of the spine. The aim of this study was to characterize load sharing between an anterior plate and the osteoligamentous structures of the cervical motion segments in kyphotic versus normal lordotic alignment following single-level ACDF using fresh ovine cervical spines (C3-C6). The loading protocol involved preloading the spine with a 20 N compressive force and applying quasi-static moments (up to 2.1 Nm) in the sagittal plane to simulate flexion and extension. Stiffness of the fusion segment was measured from the moment-rotation plot. Normal lordotic alignment was replicated by insertion of a fibular allograft 2 mm taller than the interbody space. Kyphotic alignment was simulated by removing the graft and reapplying a shorter anterior cervical plate. The average segmental sagittal angulation at C4-C5 was 5.2 ± 1.6° of lordosis for the normal lordotic group and 6.8 ± 2.3° of kyphosis for the kyphotic group. With flexion, the plate shared 52.8% of the applied load in the normal lordotic group, and 70.1% in the kyphotic group (p <0.03). In extension, the amount of load-share by the plate in the normal lordotic group was comparable to that of the kyphotic group (52.7% vs. 40.7%, p = 0.16). This study shows that kyphotic alignment of the cervical fusion segment increases the load sharing of the anterior plate under flexion loading.

KW - Anterior cervical discectomy and fusion

KW - Cervical plating

KW - Kyphosis

KW - Load sharing

KW - Ovine model

UR - http://www.scopus.com/inward/record.url?scp=47649103977&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=47649103977&partnerID=8YFLogxK

U2 - 10.1016/j.medengphy.2007.10.004

DO - 10.1016/j.medengphy.2007.10.004

M3 - Article

VL - 30

SP - 768

EP - 773

JO - Medical Engineering and Physics

JF - Medical Engineering and Physics

SN - 1350-4533

IS - 6

ER -