Open Access, Peer-reviewed
pISSN 2093-4378
eISSN 2093-4386
    J Korean Soc Spine Surg. 2009 Sep;16(3):202-209. Korean.
    Published online Sep 29, 2009.
    https://doi.org/10.4184/jkss.2009.16.3.202
    Copyright © 2009 Korean Society of Spine Surgery
    Original Article

    Clinical Significance of the Radiolucent Zone Around the Pedicle Screws in the Lumbar Degenerative Disease

    Jong Ill Kwak, M.D., Kyu Yeol Lee, M.D., Hyeon Jun Kim, M.D. and Sang Kyu Sun, M.D.
      • Department of Orthopedic Surgery, College of Medicine, Dong-A University, Busan, Korea.
    • Address reprint requests to: Kyu-Yeol Lee, M.D. Department of Orthopedic Surgery, College of Medicine, Dong-A University, 1, Dongdaesin-dong 3-ga, Seo-gu, Busan 602-715, Korea. Tel: 82-51-240-2867, Fax: 82-51-243-9764, Email: gylee@dau.ac.kr
    Received December 08, 2008; Accepted September 08, 2009.

    Abstract

    Study design

    A retrospective study.

    Objective

    To analyze the clinical significance of the radiolucent zones surrounding pedicle screws.

    Summary of Literature Review

    Clear zones have been suggested in pseudoarthrosis and a loss of fixation. However, few reports have clearly described the long-term course and clinical significance of clear zones.

    Materials and Methods

    The clear zones were evaluated in 399 patients with pedicle screw fixation after 6 months, 1 year, 2 years and 3 years. The patient was considered to be clear zone positive when 1 mm or greater circumferential lucency was confirmed around a screw on film from 2 or more directions. The time-course of the clear zones was examined with regard to age, number of levels fused, bone union, fusion method and reoperation.

    Results

    After 6 months, clear zones were observed in 124 patients (31.1%) but the clear zone-positive rate decreased with time. Clear zones were observed in 89 patients(22.3%), 44 patients(11.0%) and 41 patients(10.3%) after 1 year, 2 years and 3 years, respectively. No new clear zones had developed after 6 months. At the final follow-up, pseudoarthrosis was observed in 12 patients(3.0%). Among them, 11 were clear zone-positive and 1 was clear zone-negative. There was a statistically significant relationship between the clear zone-positive rate and multi-levels, older age and nonunion during following up. In addition, there was a relatively lower clear zone-positive rate in posterolateral fusion combined with posterior lumbar interbody fusion than only posterolateral fusion. However, the difference between them was not statistically significant.

    Conclusion

    The presence of clear zones does not always mean pseudoarthrosis but clear zones persisting for more than 2 years after surgery have a higher rate of pseudoarthrosis.

    Keywords
    Degenerative lumbar disease; Pedicle screw; Radiolucent zone; Pseudoarthrosis

    Figures

    Fig. 1
    Assessment of clear zones around pedicle screws. (A), (B): The presence of a 1 mm or greater radiolucent zone (arrows) around a screw on the radiograph was regarded as clear zone positive.

    Fig. 2
    Reoperation in case of pseudoarthrosis 70-year-old man with PLF for spinal stenosis L1-2, 2-3, 3-4, 4-5, L5-S1 (A), (B): Dynamic view showing angular motion on L5-S1. (C), (D): Postoperative X-ray showing metal removal and expandable screw fixation & bone graft and PLIF.

    Fig. 3
    Disappearance of clear zones around pedicle screws: 60-year-old woman with PLF for spinal stenosis L5-S1 with degenerative spondylolisthesis (A), (B): Clear zones (arrows) around pedicle screws were observed at 6 months (C), (D): Clear zones around pedicle screws disappeared at 3 years.

    Tables

    Table 1
    Relationship between clear zone and age

    Table 2
    Relationship between clear zone and number of levels

    Table 3
    Relationship between clear zone and bone union

    Table 4
    Relationship between clear zone and procedure of fusion

    Table 5
    Relationship between clear zone and reoperation

    References

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    MeSH Terms
    Follow-Up Studies
    Humans
    Pseudarthrosis
    Reoperation
    Retrospective Studies
    Metrics
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