Circumferential Bending Test of Lumbar 4-5 Segment and Biomechanical Investigation of Stability for Anterior Lumbar Interbody Cages and Supplemental Posterior Instrumentation

Ki Chan An; Jang Seok Choi; Young Chang Kim; Dong Reol Shin; Jung Woog Shin; Jae Do Kim; R.M. Puno

doi:10.4184/jkss.2002.9.2.59

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An, Choi, Kim, Shin, Shin, Kim, and Puno: Circumferential Bending Test of Lumbar 4-5 Segment and Biomechanical Investigation of Stability for Anterior Lumbar Interbody Cages and Supplemental Posterior Instrumentation

Original Article

Journal of Korean Spine Surg 2002;9(2):59-59*.

Published online: 21 February 2002

DOI: https://doi.org/10.4184/jkss.2002.9.2.59

Circumferential Bending Test of Lumbar 4-5 Segment and Biomechanical Investigation of Stability for Anterior Lumbar Interbody Cages and Supplemental Posterior Instrumentation

Ki Chan An, M.D., Jang Seok Choi, M.D., Young Chang Kim, M.D., Dong Reol Shin, M.D., Jung Woog Shin, M.D.^∗, Jae Do Kim, M.D.^∗∗, R.M. Puno^∗∗∗

Department of Orthopedic Surgery, Inje University Pusan Paik Hospital

^∗Department of Biomechanical Engineering, Inje University

^∗∗Department of Orthopaedic Surgery, Ko Sin University

^∗∗Spine Institute, Louisville, KY

Address reprint requests to Ki-Chan An, M.D. Department of Orthopedics, College of Medicine, Inje University Gaegum-dong, Pusanjin-gu, Pusan 633-165, Korea Tel : 82-51-890-6256, Fax : 82-51-892-6619, E-mail : osahnkc@ijnc.inje.ac.kr

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Study Design

Compare the effectiveness of three types of cages used in each case separately with that of cages supplemented by posterior fixation such as transfacet screws and transpedicular screws.

Objectives

To determine whether any important information could be obtained when anterolateral and/or posterolateral bending is imposed.

Summary of Literature Review

Most lumbar spine biomechanical bending tests have been performed on flexion-extension and lateral bending only.

Materials and Methods

Flexibility was tested through the unconstrained eccentric compression- bending of isolated L4- L5 motion segments. A total of sixteen fresh frozen human cadaveric lumbosacral spine specimens(range of ages : 42± 13 years 12 males and 4 females) were tested in this investigation. In each case bending load was applied in flexion(0 degree direction), then in 30 degree increments around the transverse plane until flexion was repeated at the 360 degree loading direction. Specimens underwent anterior interbody instrumentation with three different types of cage at L4- 5 in three groups, respectively. A fter testing the interbody fusion constructs, the L4- L5 segments were first stabilized posteriorly using transfacet screws and then retested using transpedicular screw instrumentation.

Results

In the intact model, the increase in deflection angle was twice compared with that of the previous point starting from 120 degree up to 150 degree. The pure extensional motion showed the largest deflection angles which are 3.5 times higher than those in pure flexion in average. All three types of cages showed the similar results that were obtained from the intact model.

When two kinds of supplementary instrumentations were implanted, the average deflection angle was decreased by 30% in flexion compared with that in the model with cages only. Furthermore, more than 50% decrease in deflection angles was observed in extension. However, no significant difference was found between two types of posterior instrumentations.

Conclusions

1. There was significant increase in deflection angles during extensional movement starting from 120 degree up to 180 degree in intact lumbar 4- 5 segment compared with those of flexional movement.2. All cages significantly stabilized the spine in flexion to lateral movement while none of cages stabilized in extension movement.3. All three cages included in this study provided the greatest stabilization in circumferential bending test when used with supplementary posterior instrumentations.4. There were no significant differences in spine stiffness between posterior transfacet screw fixation and transpedicular fixation.

Keywords: Biomechanics, Lumbar Spine Stability, A nterior and Posterior Instrumentation

REFERENCES

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Figures and Tables%

Fig. 1.

Specimen mounting (A. specimen with bending moment, B. specimen with the cage, C. specimen with anterior interbody cage and transfacet screws, D. specimen with anterior interbody cage and transpedicular screw with rods).

Fig. 2.

Three kinds of cages used in this study (A. type A, B. type B, C. type C).

Fig. 3.

Deflection angles measured at various points under bending moments.

Fig. 4.

Comparison of deflection angles among the cages.

Fig. 5.

Comparison of deflection angles among the surgical techniques at the same measuring point.

Fig. 6.

The changes in deflection angles among the bending moment along the measuring point.

Table 1.

Classification of the models studied

Cage Type	Instruments Used	Model Name
Type A	Intact	AI
	Cage Only	AO
	Cage + TransFacet Screw	AF
	Cage + TransPedicular Screw	AP
Type B	Intact	BI
	Cage Only	BO
	Cage + TransFacet Screw	BF
	Cage + TransPedicular Screw	BP
Type C	Intact	CI
	Cage Only	CO
	Cage + TransFacet Screw	CF
	Cage + TransPedicular Screw	CP

Table 2.

Statistical analysis of the significant difference among the cages only (O : p≤0.05, ∆: 0.05<p≤ 0.1, X : p>0.1)

θ		2.5 Nm			5 Nm			7.5 Nm
		AO	BO	CO	AO	BO	CO	AO	BO	CO
0˚	AO	–	X	X	–	∆	O	–	X	X
	BO	–	–	X	–	–	∆	–	–	O
	CO	–	–	–	–	–	–	–	–	–
30˚	AO	–	X	O	–	X	O	–	X	O
	BO	–	–	O	–	–	O	–	–	O
	CO	–	–	–	–	–	–	–	–	–
60˚	AO	–	X	O	–	X	O	–	X	O
	BO	–	–	O	–	–	X	–	–	O
	CO	–	–	–	–	–	–	–	–	–
90˚	AO	–	X	X	–	O	O	–	X	O
	BO	–	–	X	–	–	X	–	–	X
	CO	–	–	–	–	–	–	–	–	–
120˚	AO	–	O	O	–	X	O	–	X	X
	BO	–	–	X	–	–	X	–	–	X
	CO	–	–	–	–	–	–	–	–	–
150˚	AO	–	X	X	–	X	X	–	X	X
	BO	–	–	X	–	–	X	–	–	X
	CO	–	–	–	–	–	–	–	–	–
180˚	AO	–	X	X	–	O	X	–	X	X
	BO	–	–	X	–	–	∆	–	–	X
	CO	–	–	–	–	–	–	–	–	–

Table 3.

Statistical analysis of the significant difference in three type cage (I:2.5 Nm II:5 Nm III : 7.5 Nm)

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