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KMID : 0388720090160030202
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Journal of Korean Society of Spine Surgery
2009 Volume.16 No. 3 p.202 ~ p.209
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Clinical Significance of the Radiolucent Zone Around the Pedicle Screws in the Lumbar Degenerative Disease
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Kwak Jong-Ill
Lee Kyu-Yeol
Kim Hyeon-Jun
Sun Sang-Kyu
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Abstract
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Study Design A retrospective study.
Objective: To analyze the clinical significance of the radiolucent zones surrounding pedicle screws.
Summary of the 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.
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KEYWORD
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Degenerative lumbar disease, Pedicle screw, Radiolucent zone, Pseudoarthrosis
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