Radiolucent Zones Surrounding Transpedicular Screws After Lumbar Spinal Instrumented Fusion

Sang Wook Bae; Ho Yoon Kwak; Baik Yong Song; Jae Chul Yoo; Young Joo An

doi:10.4184/jkss.2005.12.2.115

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Bae, Kwak, Song, Yoo, and An: Radiolucent Zones Surrounding Transpedicular Screws After Lumbar Spinal Instrumented Fusion

Original Article

Journal of Korean Spine Surg 2005;12(2):115-122.

Published online: 12 February 2005

DOI: https://doi.org/10.4184/jkss.2005.12.2.115

Radiolucent Zones Surrounding Transpedicular Screws After Lumbar Spinal Instrumented Fusion

Sang Wook Bae, M.D., Ho Yoon Kwak, M.D., Baik Yong Song, M.D., Jae Chul Yoo, M.D., Young Joo An, M.D.

Department of Orthopedic Surgery, Eulji Hospital, Eulji Medical University

Address reprint requests to Ho Yoon Kwak, M.D. Department of Orthopedic Surgery, Eulji Hospital Eulji Medical University Hagye-Dong, Nowon-Ku, 280-1, Seoul, Korea Tel: 82-2-970-8256, Fax: 82-2-972-0068, E-mail: khy2401@eulji.or.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 Designs

A retrospective study for radiographic and clinical assessment.

Objectives

To clarify the clinical significance of the radiolucent zones surrounding transpedicular screws that occasionally appears following lumbar spinal instrumented fusion.

Summary of Literature Review

that the formation of radiolucent zones surrounding pedicular screws are significantly frequent after transpedicular fixation.

Materials and Method

88 cases, age 50 or older, which underwent lumbar spinal fusion with transpedicular screws, between January 1999 and December 2002, were included in this investigation. The postoperative radiographs of all patients were analyzed for radiolucent zones around the transpedicular screws. These radiolucent zones were evaluated in relation the number of fusion levels, the existence of osteoporosis, and the fusion status and satisfaction rates. Results: Radiolucent zones were observed in 30 cases (34%, 30/88), 13 (43%, 13/30) of which disappeared during the follow- up period. The average number of fixation levels in the cases with and without radiolucent zones were 2.33 (range 1- 4, SD 0.94) and 1.74 (range 1- 4, SD 0.82), respectively. Osteoporosis was found to accompany 43.3 and 20.7% of the cases with and without radiolucent zones, with the latter cases showing a statistically significant higher fusion rate and greater patient satisfaction.

Conclusion

Radiolucent zones, a frequent finding following pedicle screw fixation, resulted in less favorable outcomes. Surgeons should be alert to radiolucent zones and their transformation during follow- up. Methods for improving the stability of the interface between the pedicle screw and vertebral bone will require further research.

Keywords: Radiolucent zone, Transpedicular Screw

REFERENCES

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Fig. 1.

(A) Clearly visible radiolucent zones surrounding both S1 screws at postoperative 1 year. (B) Radiolucent zones become less clearly visible at two and half years after surgery. (C)Radiolucent zones disappear completely at postoperative 4 years.

Fig. 2.

(A) Wide radiolucent zones around the both sacral screws. (B) Radiograph after removal of sacral pedicle screws, which had shown severe loosening in the operating field.

Table 1.

Disappearance of radiolucent zones according to the widths

	Appearance	Disappearance
1~2 mm	12	08
2~3 mm	13	04
> 3 mm	05	01
Total	30	13
%	100%	43.3%

Table 2.

Radiolocent zones according to number of fusion segments

	Radiolucent zone (+)	Radiolucent zone (-)	Number
1 segment	06	27	33
2 segments	12	20	32
3 segments	08	10	18
4 segments	04	01	05
Total	30	58	88
Mean± SD	2.33± 0.94	1.74± 0.82

Table 3.

Clinical results

	Fusion status		Preoperative VAS	Postoperative VAS	Kirkaldy-Willis grade
Radiolucent zone (+)	Lenke A	12	4.80± 1.26	3.58± 0.83	Excellent	11
	Lenke B	10			Good	12
	Lenke C	06			Fair	05
	Lenke D	02			Poor	02
Radiolucent zone (-)	Lenke A	32	4.69± 1.26	2.12± 0.67	Excellent	30
	Lenke B	19			Good	19
	Lenke C	06			Fair	07
	Lenke D	01			Poor	02

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