Predictability of Magerl & McCormack's Load Sharing Classification on the Metal Failure after Pedicle Screw Fixation in the Thoracolumbar Spine Fracture

Myun Whan Ahn; Sung Hyuk Park; Min Chul Sung; Jong Chul Ahn; Hyun Kook Youn

doi:10.7469/JKSS.2008.15.4.223

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Ahn, Park, Sung, Ahn, and Youn: Predictability of Magerl & McCormack's Load Sharing Classification on the Metal Failure after Pedicle Screw Fixation in the Thoracolumbar Spine Fracture

Original Research

Journal of Korean Spine Surg 2008;15(4):223-229.

Published online: 18 January 2008

DOI: https://doi.org/10.7469/JKSS.2008.15.4.223

Predictability of Magerl & McCormack's Load Sharing Classification on the Metal Failure after Pedicle Screw Fixation in the Thoracolumbar Spine Fracture

Myun Whan Ahn, M.D., Sung Hyuk Park, M.D., Min Chul Sung, M.D., Jong Chul Ahn, M.D., Hyun Kook Youn, M.D.

Department of Orthopaedic Surgery, College of Medicine, Yeungnam University, Daegu, Korea

Address reprint requests to Myun Whan Ahn, M.D. Department of Orthopaedic Surgery, College of medicine, Yeungnam University Daemyungdong 317-1, Namgu, Daegu, Korea Tel: 82-53-620-3643, Fax: 82-53-628-4020, E-mail: mwahn@ynu.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

A retrograde study of metal failures at thoracolumbar spinal fractures fixed using pedicle screws.

Objectives

The predictability and usefulness of the McCormack's classifications for metal failures was compared with Magerl's classifications.

Summary of Literature Review

The load sharing classification was introduced to predict metal failure after short-segmental pedicle screw fixation by McCormack. However, its reliability is uncertain.

Materials and Methods

From July 2000 to July 2003, this study examined the plain radiographs and CT images of 31 out of 46 patients who underwent posterior stabilization using pedicle screws for thoracolumbar fractures and could be followed up at least 1 year. Fractures were classified utilizing Denis's, Magerl's, and McCormack's systems.

Results

As a result of analysis of relation between metal failure and classification system by Magerl or McCormack, there was no significant difference in its distribution. There was no correlation between the fixation range and metal failures in type C3 fractures, but there was a correlation between short fixation and metal failures in rotational burst fractures in short fixation.

Conclusions

In order to prevent metal failures after fixing thoracolumbar spinal fractures by pedicle screws, the stability should be evaluated using Magerl's classification and McCormack's total score. In addition, in cases of type C3 fractures according to the Magerl's classification, reconstructions should be carried out with a long segment fixation or anterior supporting bone grafts, particularly when McCormack's total score is greater than 7.

Keywords: Thoracolumbar spine, Fracture, Metal failure, Pedicle screw

REFERENCES

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Table 1.

Distribution of fractures with relation to metal failure and the fracture type according to denis classification at each injury level

Metal failure	Level	Denis classification							Total
		Compression type A	Burst type			Seat belt	Flexion rotation	Flexion-distractio
		Compression type A	A	B	D	Seat belt	Flexion rotation	Flexion-distractio
No	T10				1				1
	T11				1			1	2
	T12	1			1		1	1	4
	L1	1	4	2	2		2	2	130
	L2				3			1	4
	L3				1	1		1	3
	L5				1				1
	Total	2	4	2	100	1	3	6	280
Yes	L1				1				1
	L3				1				1
	L4				1				1
	Total				3				3

Table 2.

Cross-tabulation of metal failure, instrumented levels and magerl's classification

Magerl's classification	Metal failure	Instrumented level		Total
Magerl's classification	Metal failure	Short fixation	Long fixation	Total
A1:	No	1	0	1
Impaction	Total	1	0	1
A2:	No	1	0	1
Split	Total	1	0	1
A3:	No	5	1	6
Burst	Total	5	1	6
B1:	No	0	1	1
Distraction	Total	0	1	1
B2:	No	5	2	7
Distraction	Total	5	2	7
C2:	No	0	2	2
Lateral shear	Total	0	2	2
C3:	No	5	5	10
Rotational	Yes	3	0	3
burst	Total	8	5	13

Fisher's exact test (2-sided) significance, p>0.05

Table 3.

Cross-tabulation of metal failure, instrumented levels and magerl's classification (C3 & others)

Instrumented level	Metal failure	Magerl's classification		Total
Instrumented level	Metal failure	Rotation burst	Others	Total
Short fixation	No	5	12	17
	Yes	3	00	03
	Total	8	12	20
Long fixation	No	5	06	11
	Total	5	06	11

Fisher's exact test (2-sided) significance, p=0.049

Table 4.

Cross-tabulation of metal failure, total scores according McCormack's classification and instrumented levels in the burst fracture

Instrumented level	Metal failure	Total scores		Total
Instrumented level	Metal failure	<7	≥7	Total
Short fixation	No	4	6	100
	Yes	1	2	3
	Total	5	8	130
Long fixation	No	1	5	6
	Total	1	5	6

Fisher's exact test: 2-sided significance, p>0.05

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